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Dalton Transactions Downloaded by Institute of Chemistry, CAS on 22 September 2012 Published on 08 August 2012 on http://pubs.rsc.org | doi:10.1039/C2DT30989K

An international journal of inorganic chemistry www.rsc.org/dalton

Volume 41 | Number 39 | 21 October 2012 | Pages 11909–12312

ISSN 1477-9226

COVER ARTICLE Wen-Hua Sun, Carl Redshaw et al. Ethylene polymerization by 2-iminopyridylnickel halide complexes: synthesis, characterization and catalytic influence of the benzhydryl group

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Ethylene polymerization by 2-iminopyridylnickel halide complexes: synthesis, characterization and catalytic influence of the benzhydryl group†

Downloaded by Institute of Chemistry, CAS on 22 September 2012 Published on 08 August 2012 on http://pubs.rsc.org | doi:10.1039/C2DT30989K

Wen-Hua Sun,*a Shengju Song,a Baixiang Li,b Carl Redshaw,*c Xiang Hao,a Yue-Sheng Lib and Fosong Wanga Received 7th May 2012, Accepted 7th August 2012 DOI: 10.1039/c2dt30989k

A series of 2-(2-benzhydrylbenzenamino)pyridine ligands (L1–L13) was synthesized and used as bidentate N^N ligands with nickel halides to afford the corresponding nickel dihalide complexes L2Ni2Cl4 C1–C13 and L2NiBr2 D1–D13. All ligands and complexes were characterized by IR and NMR spectroscopy, and by elemental analysis. The molecular structures of the representative complexes C1·2CH3OH, C5·2H2O, D4, D7 and D9 were confirmed by single-crystal X-ray diffraction studies. Upon activation with either methylaluminoxane (MAO) or ethylaluminium sesquichloride (Et3Al2Cl3, EASC), these nickel pre-catalysts exhibited high activities (up to the range of 107 g mol−1 (Ni) h−1) towards ethylene polymerization, producing branched polyethylenes with narrow polydispersity.

Introduction Great progress has been made in the area of late-transition metal complexes as catalysts for polyolefin production over the last decade or so.1 Significant features can be incorporated into the resultant polyethylenes (PE) by employing different classes of pre-catalysts in the homo-polymerization of ethylene, namely iron and cobalt-based pre-catalysts for highly linear PE2 or nickel and palladium-based systems for branched PE.3 Furthermore, such systems have also enjoyed some success in the somewhat more challenging area of the co-polymerization of ethylene with polar monomers.4 The search for useful nickel complex pre-catalysts has included the use of various ligand sets, which can act as bi-dentate chelates based on PÔ,5 P^P,6 NÔ,7 P^N,8 and N^N9,10 ligation and tri-dentate chelates based on N^NÔ,11 N^P^N,12 P^N^N,13 and N^N^N14 ligation. In general, N^N bidentate nickel pre-catalysts provided more variation for both ethylene oligomerization and polymerization via the fine-tuning of substituents on their ligands.9,10 Recently, benzhydryl-substituted anilines were used in successfully modifying both bis(imino)pyridine ligands for the corresponding iron and cobalt complexes15 and imino-based bidentate ligands for the a

Key Laboratory of Engineering Plastics and Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China. E-mail: [email protected]; Fax: +86 10 62618239; Tel: +86 10 62557955 b State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China c Energy Materials Laboratory, School of Chemistry, University of East Anglia, Norwich, NR4 7TJ, UK. E-mail: [email protected]; Fax: +44 (0)1603 592003; Tel: +44 (0)1603 593137 † CCDC 877850, 877851, 877852, 877853, and 877854 for C1·2CH3OH, C5·2H2O, C17, C20 and C22. For crystallographic data in CIF or other electronic format see DOI: 10.1039/c2dt30989k

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corresponding nickel complexes,16 and all resulting complex pre-catalysts showed an enhancement of both their catalytic activity and thermo-stability. With this in mind, benzhydryl-substituted anilines have been used in reactions with picolinaldehyde or 2-acetylpyridine to form a series of 2-iminopyridine compounds, and two series of nickel halide complexes have been isolated and characterized. When activated with various alkylaluminium co-catalysts, all such nickel complex pre-catalysts performed with high activities (up to the range of 107 g mol−1 (Ni) h−1) in ethylene polymerization. The synthesis and characterization of the 2-iminopyridine ligands and their nickel halide complexes are reported herein and are discussed along with investigations of the catalytic behavior of the nickel complexes in ethylene polymerization.

Results and discussion Synthesis and characterization of ligands and nickel complexes

The condensation reaction of benzhydryl-substituted anilines with picolinaldehyde readily affords 2-((benzhydryl-phenylimino)methyl)pyridine compounds in good isolated yields (L1–L7, Scheme 1), whilst similar reactions with 2-acetylpyridine produced 2-((benzhydryl-phenylimino)ethyl)pyridine compounds (L8–L13, Scheme 1) with the exception of L14, which proved difficult to purify. All compound formulations were consistent with the recorded FT-IR and NMR spectra and the obtained elemental analyses. The series of 2-iminopyridine compounds (L1–L13, Scheme 1) when reacted with an equivalent of nickel chloride (NiCl2·6H2O) or half an equivalent of (1,2-dimethoxyethane)nickel bromide [(DME)NiBr2] in ethanol afforded a yellow precipitate of the respective nickel complex on addition of diethyl ether. These nickel complexes were characterized by FT-IR Dalton Trans., 2012, 41, 11999–12010 | 11999


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Fig. 2 Molecular structure of C5·2H2O thermal ellipsoids are shown at 30% probability level. Hydrogen atoms have been omitted for clarity.

Scheme 1 Synthetic procedure.

Fig. 1 Molecular structure of C1·2CH3OH thermal ellipsoids are shown at 30% probability level. Hydrogen atoms have been omitted for clarity.

spectra, which revealed that the νCvN stretching frequencies shifted to lower values with weaker intensity on comparison with those of the corresponding free ligands, for example the νCvN stretching frequency is 1644 cm−1 for the 2-iminopyridine compound L1 cf 1631 cm−1 for the nickel chloride C1 and 1630 cm−1 for the nickel bromide D1. However, their elemental analysis data indicated different structural features for the chloride compounds, i.e. L2Ni2Cl4 (C1–C13, Scheme 1) versus the bromide compounds, viz. L2NiBr2 (D1–D13, Scheme 1). Single crystals of the representative nickel complexes C1·2CH3OH, C5·2H2O, D4, D7 and D9 were grown by slow diffusion of diethyl ether into their methanol solutions, and the molecular structures were confirmed by single crystal X-ray diffraction. The nickel chloride complexes C1·2CH3OH and C5·2H2O were found to be chloride-bridged bimetallic dimers (Fig. 1 and 2), whilst the bromide analogs D4, D7 and D9 possessed a bischelate structure around the nickel center along with two bromide ligands (Fig. 3–5). 12000 | Dalton Trans., 2012, 41, 11999–12010

Fig. 3 Molecular structure of D4 thermal ellipsoids are shown at 30% probability level. Hydrogen atoms have been omitted for clarity.



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Table 2

Selected bond lengths (Å) and angles (°) for D4, D7 and D9 D4


Bond lengths (Å) Ni(1)–N(1) Ni(1)–N(2) Ni(1)–N(1A) Ni(1)–N(2A) Ni(1)–Br(1)


Bond angles (°) N(1A)–Ni(1)–N(2A) N(1A)–Ni(1)–N(1) N(2A)–Ni(1)–N(1) N(1A)–Ni(1)–N(2) N(2A)–Ni(1)–N(2) N(1)–Ni(1)–N(2) N(1A)–Ni(1)–Br(1) N(2A)–Ni(1)–Br(1) N(1)–Ni(1)–Br(1) N(2)–Ni(1)–Br(1)

2.037(3) 2.275(3) 2.037(3) 2.275(3) 2.5508(11) 78.36(10) 180.000(1) 101.64(10) 101.64(10) 180.0 78.36(10) 86.75(8) 88.64(7) 93.25(8) 91.36(7)

D7 2.057(5) 2.310(4) 2.057(5) 2.310(4) 2.5346(8) 77.59(17) 180.0 102.41(17) 102.41(17) 180.00(12) 77.59(17) 90.67(11) 84.88(11) 89.33(11) 95.12(11)

D9 2.067(7) 2.069(6) 2.045(7) 2.061(7) 2.3961(15) 79.6(3) 109.4(3) 93.5(3) 94.3(3) 168.3(3) 79.1(2) 122.5(2) 96.6(2) 128.08(19) 95.05(18)

Table 1 Selected bond lengths (Å) and angles (°) for C1·2CH3OH and C5·2H2O C1·2CH3OH Bond lengths (Å) Ni(1)–N(1) Ni(1)–N(2) Ni(1)–Cl(1) Ni(1)–Cl(2) Ni(1)–O(1) Bond angles (°) N(1)–Ni(1)–N(2) N(1)–Ni(1)–O(1) N(2)–Ni(1)–O(1) N(1)–Ni(1)–Cl(1) N(2)–Ni(1)–Cl(1) O(1)–Ni(1)–Cl(1) N(1)–Ni(1)–Cl(2) N(2)–Ni(1)–Cl(2) O(1)–Ni(1)–Cl(2) Cl(1)–Ni(1)–Cl(2)

C5·2H2O

2.082(3) 2.103(3) 2.3831(10) 2.4111(9) 2.108(2) 78.55(11) 97.39(10) 90.57(10) 87.16(8) 95.92(8) 172.72(7) 171.90(8) 93.54(8) 84.30(7) 91.99(3)

2.063(4) 2.150(4) 2.3631(16) 2.4773(15) 2.186(4) 79.10(17) 88.23(17) 91.89(15) 91.36(14) 98.71(12) 169.12(11) 95.71(13) 171.17(11) 80.74(11) 88.49(5)

Crystal structures

Molecular structures of the nickel chloride complexes C1·2CH3OH (Fig. 1) and C5·2H2O (Fig. 2) revealed centrosymmetric dimers with a distorted octahedral geometry at the nickel center. The metal is coordinated by two nitrogen atoms of the ligand (N1 and N2), one terminal chlorine (Cl1), two bridging chlorine atoms (Cl2 and Cl2A) and one additional oxygen from the solvent (C1, methanol; C5, water). Selected bond lengths and angles are tabulated in Table 1. Chloro-bridged nickel dimers are common, and reported examples include complexes bearing bidentate ligands such as 2-(arylimino)pyridines10a,b as well as N-(5,6,7-trihydroquinolin8-ylidene)arylaminonickel dichlorides.9n,o,p,16c For the nickel complex C1, the coordination of nickel with the bidentate ligand provided a five-membered heterocyclic ring comprising Ni1, N1, C5, C6 and N2, in which the nickel atom deviates by 0.289 Å from the co-plane of the four atoms N1, C8, C9 and N2. The pyridyl and phenyl planes are near perpendicular with a dihedral angle of 85.97°, whilst the dihedral angles are −89.0(4)° for C6– N2–C7–C8 and 94.2(4)° for C6–N2–C7–C12. The Ni1⋯Ni1A This journal is © The Royal Society of Chemistry 2012

distance is 3.363 Å, though slightly shorter than the literature data,10a,b indicating no direct bonding between the two nickel atoms. On comparison with analogous reported complexes,10a,b the two nickel–nitrogen bonds were enlarged along with a smaller nitrogen–nickel–nitrogen angle, which is possibly caused by the benzhydryl-substituents, which act as better electron-withdrawing groups than do alkyl substituents. The same structural features are exhibited by complex C5, and so there is no need to discuss them further. Fig. 3 shows how the nickel centre of complex D4 is surrounded by four nitrogen atoms of two bi-dentate ligands and two bromide ligands to give an octahedral geometry, similar to reported analogues.9o,10e The Ni–N bonds are of different lengths with the Ni–Npyridine shorter than the Ni–Nimino, for example Ni1–N1, 2.037(3) Å and Ni1–N2, 2.275(3) Å (see Table 2). The same structural features are also observed in the molecular structure of complex D7 (Fig. 4 and Table 2). As shown in Fig. 5, however, complex D9 adopted a distorted square-based pyramidal geometry about the nickel center. The nickel atom was coordinated by four nitrogen atoms of two ligands and one bromide, leaving a bromide as a free-anion. In addition, the Ni–N bond distances were short, but of quite similar lengths with Ni–Npyridine shorter than the Ni–Nimino.

Ethylene polymerizaion

The ligands used herein can be divided into the two groups 2-((benzhydryl-phenylimino)methyl)pyridine derivatives (i.e. R = H, L1–L7) and 2-((benzhydryl-phenylimino)ethyl)pyridine derivatives (i.e. R = Me, L8–L13), whilst their nickel complexes can also be considered separately as two groups with R = H for chloride complexes C1–C7 and bromide complexes D1–D7, and R = Me for chloride complexes C8–C13 and bromide complexes D8–D13. The reaction conditions were optimized by considering the reaction parameters such as the cocatalyst type, the molar ratio of co-catalyst to nickel complex (Al/Ni), the ethylene pressure, reaction temperature and the polymerization lifetime. Dalton Trans., 2012, 41, 11999–12010 | 12001

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Table 3

Ethylene polymerization by pre-catalyst C1 with various co-catalystsa

Run

Co-cat

T/°C

Al/Ni

Poly./g

Act.b

Mw c

Mw/Mn c

Tm d

Branchese

1 2 3 4 5 6 7

MAO MAO MMAO Et2AlCl Et2AlCl EASC EASC

20 30 20 20 30 20 30

1000 1000 1000 200 200 200 200

15.5 15.3 12.0 12.6 11.6 11.0 9.80

9.30 9.18 7.20 7.56 6.96 6.60 5.88

1.58 1.30 1.93 1.53 1.08 1.59 1.21

2.00 1.86 1.93 1.85 1.77 2.50 1.91

103 85.1 100 104 86.2 105 88.7

63.1 54.9 46.5 61.9 55.8 45.8 56.2

Conditions: 5 μmol Ni, 20 min, 10 bar ethylene, 100 mL of toluene. b Activity, 106 g mol−1 (Ni) h−1. c Molecular weights were determined by GPC, kg mol−1. d Determined by DSC, °C. e Determined by IR,17 Branches/1000C. Downloaded by Institute of Chemistry, CAS on 22 September 2012 Published on 08 August 2012 on http://pubs.rsc.org | doi:10.1039/C2DT30989K

a

Table 4

Catalytic results of ethylene polymerization with C1/MAOa

Run

Al/Ni

T/°C

t/min

Poly./g

Act.b

Mw c

Mw/Mn c

Tm d

Branchese

1 2 3 4 5 6 7 8 9 10f 11g 12h

500 1000 1500 2000 3000 1500 1500 1500 1500 1500 1500 1000

20 20 20 20 20 30 40 20 20 20 20 20

20 20 20 20 20 20 20 40 60 20 20 120

11.3 15.5 15.9 15.8 15.6 15.4 7.23 21.7 25.3 0.97 8.75 225

6.78 9.30 9.54 9.48 9.36 9.24 4.34 6.51 5.06 0.58 5.25 4.50

1.14 1.58 1.58 1.64 1.57 1.39 1.00 1.42 1.49 1.39 1.48 1.55

1.81 2.00 1.96 2.01 2.10 1.88 1.75 1.93 1.96 1.87 1.95 1.99

99.4 103 100 103 102 86.0 Wax 99.4 101 101 102 102

47.5 63.1 53.9 65.1 56.6 56.3 42.3 19.8 53.8 54.2 55.3 55.1

a Conditions: 5 μmol Ni, 10 bar ethylene, 100 mL of toluene. b Activity, 106 g mol−1 (Ni) h−1. c Molecular weights were determined by GPC, kg mol−1. d Determined by DSC, °C. e Determined by IR,17 Branches/1000C. f Conditions: 5 μmol Ni, 1 atm. ethylene, 30 mL of toluene. g Conditions: 5 μmol Ni, 5 atm. ethylene, 100 mL of toluene. h Conditions: 25 μmol Ni, 10 atm. ethylene, 3000 mL of toluene.

Ethylene polymerization by nickel complexes bearing 2-((benzhydryl-phenylimino)methyl)pyridine derivatives (R = H). In order to determine the most suitable co-catalyst, initial

investigations of pre-catalyst C1 were conducted with various alkylaluminium reagents, such as methylaluminoxane (MAO), modified methylaluminoxane (MMAO), diethylaluminium chloride (Et2AlCl) and ethylaluminium sesquichloride (Et3Al2Cl3, EASC), at 20 °C and 30 °C under 10 atm ethylene (in Table 3). The polymers obtained possessed low molecular weight, but with narrow distribution. Upon activation with methylaluminoxane (MAO), the nickel pre-catalyst C1 showed high catalytic activities (up to 9.30 × 106 g mol−1 (Ni) h−1) for ethylene polymerization. Therefore, MAO was the most effective co-catalyst and the catalytic behavior of C1/MAO was investigated further. The catalytic behavior of complex C1 was evaluated for optimum conditions using the co-catalyst MAO under 10 atm ethylene. In the presence of MAO, the effects of these parameters on activities of the pre-catalysts, molecular weights and PDIs of the resultant polyethylenes were evaluated and are presented in Table 4. From the data, it was observed that the catalytic activity was enhanced on increasing the Al/Ni ratio from 500 up to 1500 (runs 1–3 in Table 4), and for the C1/MAO catalyst system, the highest activity was 9.54 × 106 g mol−1 (Ni) h−1 within 20 min (run 3 in Table 4). However, a slight decrease of activity was observed on further increasing the Al/Ni ratio from 12002 | Dalton Trans., 2012, 41, 11999–12010

1500 to 3000 (runs 3–5 in Table 4). Thus, the most suitable molar ratio of Al : Ni was 1500 : 1 (run 3 in Table 4), whilst the best performance was observed at 20 °C (runs 3 and 6–7 in Table 4). Further elevating the temperature from 20 °C to 40 °C led to a marked decrease of activity, while the molecular weights exhibited the same trend, which is similar to previously reported pyridinylimine catalyst systems and might be caused by the instability of the active species or possibly a lower concentration of ethylene in the reaction solution at the elevated reaction temperature.9k,10a At higher temperatures, the nickel catalysts undergo irreversible decomposition. Although highly dependent on the polymerization temperature, the molecular weight of the materials produced by these Ni(II) complexes (Mw in the range 1001–1640) remains remarkably lower than that obtained with analogous α-diimine systems under similar conditions,3 indicating that so-called chain walking (a chain end isomerization involving repetitive β-H elimination and rotation/reinsertion of the eliminated olefin) was less frequent.1b,18 In general, all polyethylene products possessed narrow polydispersity in the range of 1.75–2.10, indicative of single site active species. The other pre-catalysts were also found to have high activity for ethylene polymerization and the data is summarized in Table 5. Ethylene polymerizations with the catalytic system C1/MAO were conducted under different pressures of ethylene (runs 3, 10, 11 in Table 4). The ethylene concentration significantly affected the catalytic behavior. As depicted in Table 4, the higher the This journal is © The Royal Society of Chemistry 2012

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Table 5 Catalytic results of ethylene polymerization with C1–C7, D1–D7/MAOa Run

Pre-cat.

Poly./g

Act.b

Mw c

Mw/Mn c

Tm d

Branchese

1 2 3 4 5 6 7 8 9 10 11 12 13f 14

C1 C2 C3 C4 C5 C6 C7 D1 D2 D3 D4 D5 D6 D7

15.9 13.4 12.2 15.4 14.6 17.0 13.8 23.2 21.5 20.0 22.3 20.8 23.3 21.3

9.54 8.04 7.32 9.24 8.76 10.2 8.28 13.8 12.5 12.0 13.4 12.9 13.9 12.8

1.58 2.15 1.38 2.56 2.12 2.15 1.73 1.55 1.38 2.13 2.03 2.83 2.56 2.08

1.96 2.17 2.03 2.47 2.42 2.50 2.40 2.16 2.11 2.30 2.45 2.47 2.52 2.34

100 106 97.2 98.7 98.2 99.6 98.5 103 102 103 103 102 102 103

53.9 55.8 67.1 54.9 62.7 64.1 54.2 43.2 40.2 45.8 45.3 27.1 49.6 60.9

Conditions: 5.0 μmol Ni, 1500 equiv. MAO, 20 °C, 20 min, 10 bar ethylene, 100 mL of toluene. b 105 g mol−1 (Ti) h−1. c Molecular weights were determined by GPC, kg mol−1. d Determined by DSC, °C. e Determined by IR,17 Branches/1000C. f Determined by NMR,20 Branches/1000C. a

Fig. 6

The correlation between catalytic activity and time.

ethylene pressure, the higher the catalytic activity; the higher pressure increased the chain propagation, leading to higher molecular weights. In terms of the lifetime for the C1/MAO system, the ethylene polymerization was conducted over different time periods, namely 20, 40 and 60 min (runs 3 and 8, 9 in Table 4). On prolonging the reaction time from 20 to 60 min, the activities for ethylene polymerization slightly decreased. The ethylene was continually absorbed on prolonging of the reaction time (120 min, run 12 in Table 4). Given the lifetime of the active species is relatively long (shown in Fig. 6), such systems could have potential industrial application. To compare the influence of the ligand environment on the catalytic behaviour of these nickel pre-catalysts, the pre-catalysts C1–C7 and D1–D7 were investigated under the optimum conditions (Al/Ni molar ratio of 1500 : 1 at 20 °C) under 10 atm ethylene, and the data is tabulated in Table 5. The catalytic activities were likely affected by both steric and electronic influences of the ligands (substituents R1 and R2). For the nickel(II) complexes C1–C7 and D1–D7, when R2 = benzhydryl (C1–C3 This journal is © The Royal Society of Chemistry 2012

and D1–D3), the ethylene polymerization activities decreased with the size of the R1 substituents in the order C1 (R1 = Me) > C2 (R1 = Et) > C3 (R1 = iPr) (runs 1–3 in Table 5). This implied that the less bulky R1 (R1 = Me) group was favorable for enhanced activity. It is assumed that the factors controlling the reaction speed mostly relies on the insertion of ethylene at the active metal center, and a less bulky group allows for a faster insertion reaction and consequently higher activity. The parasubstituent (R2) also affected the catalytic activities of these nickel complexes, and the observed activity order was C4 (R2 = Me) > C5 (R2 = iPr) (runs 4–5 in Table 5). The introduction of chloro substituents at the phenyl group (R2 = Cl) led to higher catalytic activity, which was attributed to the electron withdrawing groups. These phenomena are consistent with the trend of ‘the higher the net charge of the late-transition metal complexes, the higher the catalytic activity of the complex pre-catalysts’.19 The complexes C4–C6 with steric hindrance (benzhydryl) at the ortho aryl position produced polymers with much higher molecular weight and wider distribution than complexes C1–C3, which was attributed to the dibenzhydryl steric protection at the ortho aryl. Bulky anilines with an ortho-dibenzhydryl substituent either on both sides or only one side can be employed, however only one ortho-dibenzhydryl-substituent proved enough to provide effective steric protection for achieving higher activities and lower molecular weight products, which is supported by our results on the unsymmetrical ligand/nickel systems reported and is consistent with the literature.10f,g In a similar manner to the chloride analogues, ethylene polymerization by the bromide systems D1–D7/MAO was investigated under the optimum conditions (Al/Ni molar ratio of 1500 : 1 at 20 °C in Table 5). Relatively higher activities were exhibited relative to those of the chloride analogues, presumably because of the better solubility associated with the former. Other bis-ligated bromide complexes of the type (L)2Ni in literature were inactive or of low activity for polymerization because no sites are available for the olefin insertion reaction.7a,18a,b However, the nickel bromide complexes (L)2NiBr2 herein were active when combined with co-catalysts such as MAO or other alkylaluminiums in the presence of olefins, where they are possibly transformed into a mono-ligated complex of the type (L)NiBr2.9d,10e The nickel(II) bromide precatalysts demonstrated a significant influence on the activity, the molecular weight and branching frequency of the obtained PEs. The trend for catalytic activities was such that the order D6 > D1 > D4 > D5 > D7 > D2 > D3 was observed. The presence of an electron withdrawing group ( p-Cl) on the aryl system affects the catalytic activities. Compared with other analogs containing the ortho-alkyl substituted arylamine unit that produce branched oligomers, PEs or mixture thereof,9d,10a,c,d,f the current nickel pre-catalysts derived from bulky ortho-benzhydryl substituted arylamines showed increased activities. Apparently, the bulky benzhydryl unit herein provided steric protection, which favoured chain propagation over β-H transfer and thereby enhanced activities. The mononuclear systems showed much higher activities than those observed for the binuclear systems.9f,10h The attainment of low molecular weight polyethylenes is likely due to the fact that the (imino)pyridine ligands provide only half of the ortho aryl steric protection (compared to symmetric α-diimine ligands), thus increasing the chain transfer rate.9j Compared with N-(5,6,7-trihydroquinolin-8-ylidene)Dalton Trans., 2012, 41, 11999–12010 | 12003

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arylaminonickel dichlorides,9n,o,p,q,16c these catalysts have higher activity in ethylene polymerization. The melting point of the polyethylenes obtained were found to be lower than 110 °C and gradually decreased on elevating the polymerization reaction temperature. The extent of branching was a function of both the temperature and the ethylene pressure. Such unusual properties were caused by the formation of polyethylenes with moderate branching, as confirmed by the 13 C NMR measurements. As shown in Fig. 7, the number of

Fig. 7

13

C-NMR spectrum of polyethylene (run 13 in Table 5).

branches was calculated according to the literature,20 and it was found that polyethylene with 49.6 branches/1000 carbons (Fig. 7) was obtained at 20 °C (run 13 in Table 5). Ethylene polymerization by nickel complexes bearing 2-((benzhydryl-phenylimino)ethyl)pyridine derivatives (R = Me). On changing from the aldimine (R = H) to the ketimine (R

= Me) derivative (for a given aryl group), a reduction in the activity of the catalyst system was observed along with a higher molecular weight and narrow distribution for the polymer. In a similar procedure, complex D11 was used to explore suitable co-catalysts (runs 1–4 in Table 6) for optimum polymerization conditions. The D11 catalytic system displayed high catalytic activities for ethylene polymerization with various alkylaluminium reagents (MAO, MMAO, Et2AlCl and EASC). In the presence of EASC, the highest activity was obtained, and produced high molecular weight polyethylene. Based on catalytic activity and economic considerations (less co-catalyst), EASC was selected for further investigation, and the catalytic system under 10 bar ethylene was typically investigated, with varying reaction parameters (Table 6). On changing the reaction parameters, it was observed that nickel bromide complex D11 has higher activity under the optimum conditions (10 atm ethylene, Al/Ni = 300 : 1 at 20 °C in Table 6). In the D11/EASC system, ethylene polymerization was steadily maintained over 60 min (runs 8, 13 and 14 in Table 6). Therefore, the catalytic behavior of all the nickel complexes were investigated under these optimum conditions, and the results are summarized in Table 6. Similar catalytic behavior was observed for these nickel complexes (Table 6), but relatively

Table 6

Catalytic results of ethylene polymerization with C8–C13, D8–D13a

Run

Pre-cat. (μmol)

Co-cat.

T/°C

t (min)

Al/Ni

Poly./g

Act.b

Mw c

Mw/Mn c

Tm d

Branchese

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15f 16 17 18 19 20 21 22 23 24 25 26g

D11(3.0) D11(3.0) D11(3.0) D11(3.0) D11(1.5) D11(4.5) D11(3.0) D11(3.0) D11(3.0) D11(3.0) D11(3.0) D11(3.0) D11(3.0) D11(3.0) C8(5.0) C9(5.0) C10(5.0) C11(5.0) C12(5.0) C13(5.0) D8(3.0) D9(3.0) D10(3.0) D12(3.0) D13(3.0) D11(3.0)

MAO MMAO Et2AlCl EASC EASC EASC EASC EASC EASC EASC EASC EASC EASC EASC EASC EASC EASC EASC EASC EASC EASC EASC EASC EASC EASC EASC

20 20 20 20 20 20 20 20 20 20 30 40 20 20 20 20 20 20 20 20 20 20 20 20 20 20

20 20 20 20 20 20 20 20 20 20 20 20 40 60 20 20 20 20 20 20 20 20 20 20 20 20

1000 1000 200 200 200 200 100 300 400 500 300 300 300 300 300 300 300 300 300 300 300 300 300 300 300 300

3.05 2.23 2.68 3.33 1.21 4.15 2.99 3.49 3.02 1.81 2.98 1.45 6.50 9.62 9.85 6.12 5.23 3.23 3.15 3.45 6.78 5.29 4.50 2.72 3.51 3.50

3.05 2.23 2.68 3.33 2.42 2.77 2.99 3.49 3.02 1.81 2.98 1.45 3.25 3.21 5.91 3.67 3.14 1.94 1.89 2.07 6.78 5.29 4.50 2.72 3.51 3.50

2.83 3.23 3.31 3.66 4.63 3.67 3.98 3.82 3.25 2.88 3.72 2.13 3.72 3.62 1.59 2.09 2.28 4.05 3.95 4.55 1.85 2.12 2.29 3.83 3.99 3.79

2.17 2.00 2.16 2.09 2.00 2.01 2.03 1.99 2.00 1.91 1.99 1.87 2.19 2.07 1.90 1.92 2.00 2.00 2.00 2.00 1.87 1.89 2.01 2.03 1.90 1.97

87.7 84.0 89.0 88.6 93.7 82.2 93.4 92.5 88.2 96.3 Wax Wax 94.7 96.0 97.7 96.0 99.2 95.6 98.7 97.2 98.4 98.5 102 104 97.5 98.9

43.5 45.7 53.2 39.3 29.4 20.1 53.3 44.1 53.1 49.6 53.3 42.2 63.1 29.8 43.3 44.1 63.1 54.7 42.7 56.1 74.4 19.5 13.4 49.6 29.6 32.9

a d

Conditions: 10 bar ethylene, 100 mL of toluene. b Activity, 106 g mol−1 (Ni) h−1. c Molecular weights were determined by GPC, kg mol−1. Determined by DSC, °C. e Determined by IR,17 Branches/1000C. f Determined by NMR,20 Branches/1000C. g With adding 3.0 μmol(DME)NiBr2.

12004 | Dalton Trans., 2012, 41, 11999–12010



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lower activities and higher molecular weights were exhibited relative to those of their analogues (Table 5). A clear trend for catalytic activities was displayed in regard to the nature of the ligands present, such that the order C8 > C9 > C10, C13 > C11 > C12, D8 > D9 > D10 and D13 > D11 > D12 was observed. However, the complexes C8–C10 and D8–D10 displayed higher polymerization activity than did complexes C11–C13 and D11–D13, which suggested that a reduction in the steric bulk at the ortho-aryl position or replacement of the para-aryl proton with a chlorine can increase the activity. Furthermore, complexes C11–C13 and D11–D13 with increased steric hindrance at the ortho-aryl, produced polymers of much higher molecular weight than those by pre-catalysts C8–C10 and D8–D11. From the crystal structures, the nickel center of D9 appears to be restricted/hindered from interacting with ethylene and this leads to the poorer catalytic properties, which is similar to other reports.14g On introducing one equivalent of (DME)NiBr2, complex D11 did not show higher activity, which indicated that there were no new active species formed during the ethylene polymerization. The polyethylene obtained was analyzed by 13 C-NMR measurements and the number of branches was calculated according to the literature,20 and it was found that polyethylene with 43.3 branches/1000 carbons (Fig. 8) was obtained at 20 °C (run 15 in Table 6).

Conclusion A series of ligands (L1–L13) and nickel complexes (C1–C13, D1–D13) were synthesized and fully characterized. Single crystal X-ray crystallographic studies for representative complexes C1·2CH3OH, C5·2H2O, D4, D7 and D9 were performed. These nickel complexes exhibited high activities of up to 1.39 × 107 g mol−1 (Ni) h−1 in ethylene polymerization under optimum conditions, and produced moderately branched polyethylene of low molecule weight and narrow PDI, indicative of single-site active species. The catalytic activities and the molecular weights decreased on elevating the reaction temperature. Further research efforts indicated that the ligand substituents present had a remarkable influence on the observed activities. The highest activity was obtained with the complex D6 having R as hydrogen, R1 as benzhydryl and R2 as chlorine. Such pre-catalysts could have application in the industrialized production of polyethylene waxes.

Experimental section Syntheses and characterization of the organic compounds and nickel complexes 2-((2,4-Dibenzhydryl-6-methylphenylimino)methyl)pyridine (L1). A mixture of picolinaldehyde (0.540 g, 5.0 mmol), 2,4-

dibenzhydryl-6-methylbenzenamine (2.19 g, 5.0 mmol) and a catalytic amount of p-toluenesulfonic acid in toluene (80 mL) were refluxed for 6 h. After solvent evaporation at reduced pressure, the crude product was purified by column chromatography on alumina with the eluent of petroleum ether–ethyl acetate (v : v = 10 : 1) to afford a white solid in 78% isolated yield. Mp: 163–164 °C. δH (400 MHz; CDCl3; Me4Si) 8.61 (1H, d, J = 7.6 Hz), 8.04 (1H, d, J = 7.9 Hz), 7.81 (1H, s), 7.56 (1H, t, J = 10.2 Hz), 7.32 (1H, t, J = 8.1 Hz), 7.23 (4H, t, J = 9.7 Hz), 7.17 (2H, d, J = 7.3 Hz), 7.14–7.08 (6H, m), 7.04 (4H, d, J = 7.3 Hz), 6.94 (4H, d, J = 7.8 Hz), 6.87 (1H, s), 6.57 (1H, s), 5.54 (1H, s), 5.39 (1H, s), 2.06 (3H, s, –CH3). δC (100 MHz; CDCl3; Me4Si) 164.2, 154.2, 149.5, 148.3, 144.2, 143.5, 139.0, 136.5, 134.1, 129.8, 129.5, 129.3, 128.9, 128.2, 128.1, 126.1, 126.0, 125.9, 125.2, 121.3, 56.34, 52.01, 18.52. Anal. Calcd for C39H32N2 (528.26) C, 88.60; H, 6.10; N, 5.30; Found: C, 88.53; H, 6.17; N, 5.20. FT-IR (Diamond disk, cm−1): 3022, 1644, 1598, 1568, 1469, 1448, 1203, 1128, 1077, 745, 698. 2-((2,4-Dibenzhydryl-6-ethylphenylimino)methyl)pyridine (L2).

In a manner similar to that described for L1, L2 was prepared as a light yellow solid in 75% yield. Mp: 165–166 °C. δH (400 MHz; CDCl3; Me4Si) 8.62 (1H, d, J = 7.6 Hz), 8.03 (1H, d, J = 8.0 Hz), 7.76 (2H, m), 7.34 (1H, t, J = 10.1 Hz), 7.22 (4H, d, J = 7.6 Hz), 7.18 (2H, d, J = 7.9 Hz), 7.14–7.10 (6H, m), 7.04 (4H, d, J = 7.5 Hz), 6.91 (5H, d, J = 7.8 Hz), 6.56 (1H, s), 5.49 (1H, s), 5.41 (1H, s), 2.45–2.38 (2H, m), 0.87 (3H, t, J = 8.9, –CH3). δC (100 MHz; CDCl3; Me4Si) 164.1, 154.3, 149.7, 148.2, 144.4, 143.7, 139.1, 136.6, 133.7, 132.3, 129.6, 129.5, 129.4, 129.0, 128.3, 128.2, 126.2, 125.9, 125.3, 121.5, 56.59, 52.22, 24.68, 14.87. Anal. Calcd for C40H34N2 (542.27) C, 88.52; H, 6.31; N, 5.16; Found: C, 88.42; H, 6.41; N, 5.06. FT-IR (Diamond disk, cm−1): 3022, 1644, 1598, 1567, 1469, 1447, 1199, 1072, 741, 697. 2-((2,4-Dibenzhydryl-6-isopropylphenylimino)methyl)pyridine (L3). In a manner similar to that described for L1, L3 was pre-

pared as a light yellow solid in 79% yield. Mp: 168–169 °C. δH (400 MHz; CDCl3; Me4Si) 8.63 (1H, d, J = 7.6 Hz), 8.01 (1H, d, J = 8.1 Hz), 7.77 (1H, t, J = 10.2 Hz), 7.72 (1H, s), 7.34 (1H, t, J = 10.1 Hz), 7.24 (12H, m), 7.04 (4H, d, J = 7.7 Hz), 6.97 (1H, s), 6.91 (4H, d, J = 7.6 Hz), 6.53 (1H, s), 5.46 (1H, s), 5.41 (1H, s), 2.90–2.83 (1H, m, –CH–), 1.06 (6H, d, J = 8.3 Hz, 2 × –CH3). δC (100 MHz; CDCl3; Me4Si) 164.2, 154.3, 149.7, 147.7, 144.6, 143.8, 139.1, 137.1, 136.6, 133.4, 129.7, 129.5, 128.9, 128.3, 128.2, 126.2, 125.3, 121.6, 56.78, 52.41, 27.97, 23.74. Anal. Calcd for C41H36N2 (556.29) C, 88.45; H, 6.52; N, 5.03; Found: C, 88.35; H, 6.63; N, 4.99. FT-IR (Diamond disk, cm−1): 3024, 1639, 1585, 1567, 1494, 1444, 1079, 776, 739, 692. 2-((2,6-Dibenzhydryl-4-methylphenylimino)methyl)pyridine (L4).

Fig. 8

13

C-NMR spectrum of polyethylene (run 15 in Table 6).


In a manner similar to that described for L1, L4 was prepared as Dalton Trans., 2012, 41, 11999–12010 | 12005

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a light yellow solid in 70% yield. Mp: 258–259 °C. δH (400 MHz; CDCl3; Me4Si) 8.58 (1H, d, J = 7.6 Hz), 7.68 (2H, t, J = 9.9 Hz), 7.58 (1H, d, J = 7.6 Hz), 7.28 (2H, m), 7.21–7.08 (14H, m), 7.00 (7H, d, J = 8.6 Hz), 6.64 (1H, s), 5.53 (1H, s), 2.04 (3H, s, –CH3). δC (100 MHz; CDCl3; Me4Si) 165.1, 153.6, 149.6, 148.1, 143.8, 142.9, 136.5, 133.2, 132.6, 129.8, 129.7, 129.4, 129.2, 128.8, 128.6, 128.2, 128.0, 126.7, 126.3, 125.2, 122.3, 121.8, 52.04, 21.53. Anal. Calcd for C39H32N2 (528.26) C, 88.60; H, 6.10; N, 5.30; Found: C, 88.45; H, 6.25; N, 5.15. FT-IR (Diamond disk, cm−1): 3024, 1560, 1589, 1566, 1492, 1445, 1203, 1077, 1030, 872, 741, 700. 2-((2,6-Dibenzhydryl-4-isopropylphenylimino)methyl)pyridine (L5). In a manner similar to that described for L1, L5 was pre-

pared as a yellow solid in 75% yield. Mp: 201–202 °C. δH (400 MHz; CDCl3; Me4Si) 8.58 (1H, d, J = 7.8 Hz), 7.68 (1H, t, J = 10.2 Hz), 7.61 (1H, d, J = 8.4 Hz), 7.28 (1H, t, J = 9.8 Hz), 7.20–7.09 (12H, m), 7.04 (1H, s), 7.00 (8H, d, J = 7.4 Hz), 6.69 (2H, s), 5.45 (2H, s), 2.73–2.66 (1H, m), 1.06–0.93 (6H, d, J = 8.3 Hz, 2 × –CH3). δC (100 MHz; CDCl3; Me4Si) 165.1, 153.8, 149.6, 148.3, 143.9, 143.5, 136.3, 132.9, 129.7, 128.5, 128.2, 126.2, 125.0, 122.1, 52.16, 33.65, 24.13. Anal. Calcd for C41H36N2 (556.29) C, 88.45; H, 6.52; N, 5.03; Found: C, 88.27; H, 6.62; N, 4.99. FT-IR (Diamond disk, cm−1): 3026, 1634, 1585, 1493, 1468, 1444, 1031, 884, 741, 696. 2-((2,6-Dibenzhydryl-4-chlorophenylimino)methyl)pyridine (L6).

In a manner similar to that described for L1, L6 was prepared as a yellow solid in 70% yield. Mp: 256–257 °C. δH (400 MHz; CDCl3; Me4Si) 8.58 (1H, d, J = 8.0 Hz), 7.69 (1H, t, J = 10.1 Hz), 7.51 (1H, d, J = 8.3 Hz), 7.31 (1H, t, J = 9.9 Hz), 7.19–7.09 (13H, m), 6.99 (8H, d, J = 7.4 Hz), 6.89 (1H, s), 6.81 (2H, s). δC (100 MHz; CDCl3; Me4Si) 165.8, 153.3, 149.8, 149.0, 148.3, 142.9, 141.9, 136.5, 135.5, 129.7, 129.5, 129.2, 129.0, 128.8, 128.5, 128.4, 128.2, 128.0, 127.1, 126.6, 125.4, 122.5, 52.08. Anal. Calcd for C38H29ClN2 (548.2) C, 83.12; H, 5.32; N, 5.10; Found: C, 82.99; H, 5.45; N, 4.96. FT-IR (Diamond disk, cm−1): 3025, 1649, 1566, 1493, 1450, 1433, 1260, 1176, 1077, 1026, 802, 738, 697.

5.54 (1H, s), 5.39 (1H, s), 2.06 (3H, s, –CH3), 1.55 (3H, s). δC (100 MHz; CDCl3; Me4Si) 168.7, 156.3, 148.6, 146.7, 144.6, 144.5, 143.7, 142.7, 138.2, 136.4, 133.3, 129.9, 129.5, 128.9, 128.4, 128.3, 128.1, 126.3, 126.2, 126.0, 125.2, 124.8, 121.3, 56.50, 52.45, 18.11, 16.75. C40H34N2 (542.27) C, 88.52; H, 6.31; N, 5.16. Found: C, 88.43; H, 6.43; N, 4.04. FT-IR (Diamond; cm−1): 3024, 1643, 1599, 1566, 1493, 1468, 1449, 1362, 1225, 1104, 1075, 1033, 781, 696. 2-((2,4-Dibenzhydryl-6-ethylphenylimino)ethyl)pyridine (L9).

In a manner similar to that described for L1, L9 was prepared as a yellow solid in 59% yield. Mp: 127–128 °C. δH (400 MHz; CDCl3; Me4Si) 8.61 (1H, d, J = 8.1 Hz), 8.29 (1H, d, J = 7.9 Hz), 7.78 (1H, t, J = 9.1 Hz), 7.35 (1H, t, J = 9.2 Hz), 7.24–7.04 (16H, m), 6.96 (2H, s), 6.88 (3H, s), 6.59 (1H, s), 5.42 (1H, s), 5.36 (1H, s), 2.22 (2H, m), 1.54 (3H, s), 1.03 (3H, t, J = 9.9 Hz, –CH3). δC (100 MHz; CDCl3; Me4Si) 168.6, 156.4, 148.7, 146.3, 144.7, 144.6, 143.8, 142.7, 138.2, 136.4, 132.8, 131.0, 129.9, 129.5, 128.9, 128.6, 128.3, 128.2, 128.0, 127.5, 126.3, 126.2, 126.0, 124.8, 121.3, 56.65, 52.48, 24.38, 16.97, 13.70. C41H36N2 (556.29) C, 88.45; H, 6.52; N, 5.03. Found: C, 88.35; H, 6.70; N, 4.99. FT-IR (Diamond; cm−1): 3023, 1638, 1599, 1567, 1493, 1448, 1364, 1305, 1105, 743, 697. 2-((2,4-Dibenzhydryl-6-isopropylphenylimino)ethyl)pyridine (L10). In a manner similar to that described for L1, L10 was

prepared as a yellow solid in 65% yield. Mp: 164–165 °C. δH (400 MHz; CDCl3; Me4Si) 8.63 (1H, d, J = 8.1 Hz), 8.31 (1H, d, J = 8.0 Hz), 7.80 (1H, t, J = 8.0 Hz), 7.37 (1H, t, J = 8.2 Hz), 7.24–7.07 (15H, m), 7.00 (2H, s), 6.92 (2H, s), 6.86 (1H, s), 6.59 (1H, s), 6.27 (1H, s), 5.44 (1H, s), 5.37 (1H, s), 2.61 (1H, m, –CH–), 1.53 (3H, s), 1.03 (6H, d, J = 8.4 Hz, 2 × –CH3). δC (100 MHz; CDCl3; Me4Si) 168.6, 156.4, 148.6, 145.5, 144.8, 144.7, 143.8, 142.7, 138.2, 136.4, 135.7, 132.6, 129.9, 129.5, 128.8, 128.3, 128.2, 128.0, 126.2, 126.1, 126.0, 125.0, 124.8, 121.4, 56.76, 52.62, 28.07, 23.80, 22.72, 17.16. C42H38N2 (570.3) C, 88.38; H, 6.71; N, 4.91. Found: C, 88.32; H, 5.00; N, 4.80. FT-IR (Diamond; cm−1): 3023, 1650, 1584, 1566, 1493, 1467, 1444, 1363, 1104, 780, 745, 696.

2-((2-Benzhydryl-4,6-dimethylphenylimino)methyl)pyridine (L7).

In a manner similar to that described for L1, L7 was prepared as a yellow solid in 76% yield. Mp: 116–117 °C. δH (400 MHz; CDCl3; Me4Si) 8.62 (1H, d, J = 7.8 Hz), 8.02 (1H, d, J = 8.1 Hz), 7.77 (1H, t, J = 10.2 Hz), 7.34 (1H, t, J = 10.1 Hz), 7.21–7.12 (6H, m), 7.04 (4H, d, J = 8.8 Hz), 6.95 (1H, s), 6.59 (1H, s), 6.58 (2H, s), 2.22 (3H, s, –CH3), 2.10 (3H, s, –CH3). δC (100 MHz; CDCl3; Me4Si) 164.5, 154.4, 149.7, 148.0, 143.9, 136.6, 134.3, 133.2, 130.0, 129.8, 128.3, 128.1, 126.2, 125.9, 125.3, 121.5, 52.08, 21.26, 18.45. Anal. Calcd for C27H24N2 (376.19) C, 86.13; H, 6.43; N, 7.44; Found: C, 86.01; H, 6.55; N, 7.31. FT-IR (Diamond disk, cm−1): 3021, 1642, 1585, 1492, 1470, 1434, 1202, 1135, 990, 740, 696.

2-((2,6-Dibenzhydryl-4-methylphenylimino)ethyl)pyridine (L11).

In a manner similar to that described for L1, L11 was prepared as a yellow solid in 66% yield. Mp: 181–182 °C. δH (400 MHz; CDCl3; Me4Si) 8.58 (1H, d, J = 8.1 Hz), 8.01 (1H, d, J = 8.0 Hz), 7.70 (1H, t, J = 8.0 Hz), 7.32 (1H, t, J = 8.1 Hz), 7.24–7.11 (12H, m), 7.01 (8H, t, J = 10.2 Hz), 6.68 (2H, s), 5.26 (2H, s), 2.17 (3H, s, –CH3), 1.07 (3H, s, –CH3). δC (100 MHz; CDCl3; Me4Si) 169.7, 156.2, 148.6, 146.3, 143.9, 142.7, 136.2, 132.4, 131.7, 130.0, 129.6, 128.8, 128.4, 128.2, 126.4, 126.1, 124.7, 121.5, 52.26, 21.53, 17.07. C40H34N2 (542.27) C, 88.52; H, 6.31; N, 5.16. Found: C, 88.42; H, 6.43; N, 5.00. FT-IR (Diamond; cm−1): 3025, 1646, 1599, 1582, 1493, 1445, 1238, 1106, 769, 697.

2-((2,4-Dibenzhydryl-6-methylphenylimino)ethyl)pyridine (L8).

In a manner similar to that described for L1, L8 was prepared as a yellow solid in 58% yield. Mp: 123–124 °C. δH (400 MHz; CDCl3; Me4Si) 8.61 (1H, d, J = 8.0 Hz), 8.31 (1H, d, J = 7.9 Hz), 7.80 (1H, t, J = 8.8 Hz), 7.37 (1H, t, J = 8.2 Hz), 7.23–7.08 (16H, m), 7.00 (2H, s), 6.92 (2H, s), 6.86 (1H, s), 6.62 (1H, s), 12006 | Dalton Trans., 2012, 41, 11999–12010

2-((2,6-Dibenzhydryl-4-isopropylphenylimino)ethyl)pyridine (L12). In a manner similar to that described for L1, L12 was

prepared as a yellow solid in 67% yield. Mp: 145–146 °C. δH (400 MHz; CDCl3; Me4Si) 8.58 (1H, d, J = 8.1 Hz), 8.02 (1H, d, J = 8.0 Hz), 7.70 (1H, t, J = 8.0 Hz), 7.32 (1H, t, J = 8.0 Hz), This journal is © The Royal Society of Chemistry 2012

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7.24–7.11 (12H, m), 7.00 (8H, t, J = 10.1 Hz), 6.72 (2H, s), 5.26 (2H, s), 2.70 (1H, m, –CH–), 1.06 (9H, d, J = 7.9 Hz, 3 × –CH3). δC (100 MHz; CDCl3; Me4Si) 169.5, 156.2, 148.6, 146.5, 144.0, 142.9, 142.7, 136.2, 132.1, 130.0, 129.6, 128.4, 128.1, 126.4, 126.2, 126.1, 124.7, 121.5, 52.44, 33.70, 24.32, 17.14. C42H38N2 (570.3) C, 88.38; H, 6.71; N, 4.91. Found: C, 88.25; H, 6.98; N, 4.84. FT-IR (Diamond; cm−1): 3026, 1646, 1600, 1585, 1566, 1493, 1467, 1362, 1105, 767, 745, 696.


2-((2,6-Dibenzhydryl-4-chlorophenylimino)ethyl)pyridine (L13).

In a manner similar to that described for L1, L13 was prepared as a yellow solid in 68% yield. Mp: 142–143 °C. δH (400 MHz; CDCl3; Me4Si) 8.58 (1H, d, J = 8.1 Hz), 7.98 (1H, d, J = 8.0 Hz), 7.71 (1H, t, J = 8.0 Hz), 7.34 (1H, t, J = 8.2 Hz), 7.24–7.13 (12H, m), 7.01–6.97 (8H, m), 6.84 (2H, s), 5.24 (2H, s), 1.04 (3H, s, –CH3). δC (100 MHz; CDCl3; Me4Si) 170.2, 155.7, 148.7, 147.1, 142.9, 141.8, 136.3, 134.5, 129.8, 129.5, 128.6, 128.3, 128.1, 126.7, 126.5, 125.0, 121.5, 52.22, 17.16. C39H31ClN2 (562.22) C, 83.18; H, 5.55; Cl, 6.30; N, 4.97. Found: C, 83.00; H, 5.65; N, 4.85. FT-IR (Diamond; cm−1): 3025, 1645, 1581, 1563, 1493, 1427, 1302, 1180, 1105, 769, 695. 2-((2,4-Dibenzhydryl-6-methylphenylimino)methyl)pyridyl nickel dichloride (C1). The ligand L1 (0.264 g, 0.5 mmol) and

NiCl2·6H2O (0.118 g, 0.5 mmol) were added to a Schlenk tube together with 10 ml of dried ethanol. The reaction mixture was then stirred for 12 h at room temperature and diethyl ether (10 ml) was added to precipitate the complex. The precipitate was washed with diethyl ether and dried in vacuum to obtain a yellow powder in 83% yield. Anal. Calcd for C39H32Cl2N2Ni (656.13) C, 71.16; H, 4.90; N, 4.26; Found: C, 71.00; H, 5.00; N, 4.36. FT-IR (Diamond; cm−1): 2971, 1631, 1596, 1494, 1448, 1078, 1045, 770, 746, 700. 2-((2,4-Dibenzhydryl-6-ethylphenylimino)methyl)pyridyl nickel dichloride (C2). In a manner similar to that described for C1, C2

was prepared as a yellow powder in 86% yield. Anal. Calcd for C40H34Cl2N2Ni (670.15) C, 71.46; H, 5.10; N, 4.17%. Found: C, 71.36; H, 5.30; N, 4.00. FT-IR (Diamond; cm−1): 3225, 1631, 1596, 1494, 1448, 1192, 1077, 1043, 772, 746, 701. 2-((2,4-Dibenzhydryl-6-isopropylphenylimino)methyl)pyridyl nickel dichloride (C3). In a manner similar to that described for

C1, C3 was prepared as a yellow powder in 81% yield. Anal. Calcd for C41H36Cl2N2Ni (684.16) C, 71.75; H, 5.29; N, 4.08; Found: C, 71.65; H, 5.39; N, 4.00. FT-IR (Diamond; cm−1): 3027, 1633, 1596, 1494, 1447, 1302, 1077, 1040, 775, 745, 701. 2-((2,6-Dibenzhydryl-4-methylphenylimino)methyl)pyridyl nickel dichloride (C4). In a manner similar to that described for

C1, C4 was prepared as a yellow powder in 88% yield. Anal. Calcd for C39H32Cl2N2Ni (656.13) C, 71.16; H, 4.90; N, 4.26; Found: C, 71.00; H, 4.98; N, 4.14. FT-IR (Diamond; cm−1): 3025, 1633, 1597, 1494, 1447, 1197, 1029, 765, 702. 2-((2,6-Dibenzhydryl-4-isopropylphenylimino)methyl)pyridyl nickel dichloride (C5). In a manner similar to that described for

C1, C5 was prepared as a yellow powder in 92% yield. Anal. Calcd for C41H36Cl2N2Ni (684.16) C, 71.75; H, 5.29; N, 4.08; This journal is © The Royal Society of Chemistry 2012

Found: C, 71.65; H, 5.39; N, 4.00. FT-IR (Diamond; cm−1): 3023, 1632, 1597, 1493, 1447, 1157, 1027, 761, 700. 2-((2,6-Dibenzhydryl-4-chlorophenylimino)methyl)pyridyl nickel dichloride (C6). In a manner similar to that described for

C1, C6 was prepared as a yellow powder in 87% yield. Anal. Calcd for C38H29Cl3N2Ni (676.07) C, 67.25; H, 4.31; N, 4.13; Found: C, 67.15; H, 4.44; N, 4.00. FT-IR (Diamond; cm−1): 3021, 1632, 1597, 1571, 1494, 1446, 1302, 1172, 1028, 765, 699. 2-((2-Benzhydryl-4,6-dimethylphenylimino)methyl)pyridyl nickel dichloride (C7). In a manner similar to that described for

C1, C7 was prepared as a yellow powder in 85% yield. Anal. Calcd for C27H24Cl2N2Ni (504.07) C, 64.08; H, 4.78; N, 5.54; Found: C, 63.99; H, 4.88; N, 5.44. FT-IR (Diamond; cm−1): 3023, 1633, 1596, 14446, 1196, 1131, 1026, 770.745, 700. 2-((2,4-Dibenzhydryl-6-methylphenylimino)ethyl)pyridyl nickel dichloride (C8). In a manner similar to that described for C1, C8

was prepared as a yellow powder in 86% yield. Anal. Calcd for C40H34Cl2N2Ni (670.15) C, 71.46; H, 5.10; N, 4.17; Found: C, 71.26; H, 5.16; N, 4.10. FT-IR (Diamond; cm−1): 3208, 1611, 1596, 1493, 1444, 1315, 1259, 1029, 743, 698. 2-((2,4-Dibenzhydryl-6-ethylphenylimino)ethyl)pyridyl nickel dichloride (C9). In a manner similar to that described for C1,

C9 was prepared as a yellow powder in 88% yield. Anal. Calcd for C41H36Cl2N2Ni (684.16) C, 71.75; H, 5.29; N, 4.08; Found: C, 71.65; H, 5.49; N, 4.00. FT-IR (Diamond; cm−1): 3024, 1613, 1593, 1493, 1451, 1374, 1320, 1259, 743, 697. 2-((2,4-Dibenzhydryl-6-isopropylphenylimino)ethyl)pyridyl nickel dichloride (C10). In a manner similar to that described

for C1, C10 was prepared as a yellow powder in 89% yield. Anal. Calcd for C42H38Cl2N2Ni (698.18) C, 72.03; H, 5.47; N, 4.00; Found: C, 72.00; H, 5.57; N, 3.90. FT-IR (Diamond; cm−1): 3025, 1614, 1592, 1493, 1452, 1373, 1257, 743, 697. 2-((2,6-Dibenzhydryl-4-methylphenylimino)ethyl)pyridyl nickel dichloride (C11). In a manner similar to that described for C1,

C11 was prepared as a yellow powder in 85% yield. Anal. Calcd for C40H34Cl2N2Ni (670.15) C, 71.46; H, 5.10; N, 4.17; Found: C, 71.26; H, 5.30; N, 4.07. FT-IR (Diamond; cm−1): 3024, 1614, 1595, 1494, 1445, 1372, 1317, 1258, 1029, 769, 700. 2-((2,6-Dibenzhydryl-4-isopropylphenylimino)ethyl)pyridyl nickel dichloride (C12). In a manner similar to that described

for C1, C12 was prepared as a yellow powder in 89% yield. Anal. Calcd for C42H38Cl2N2Ni (698.18) C, 72.03; H, 5.47; N, 4.00; Found: C, 72.13; H, 5.57; N, 3.95. FT-IR (Diamond; cm−1): 2959, 1615, 1596, 1494, 1445, 1317, 1258, 1028, 769, 700. 2-((2,6-Dibenzhydryl-4-chlorophenylimino)ethyl)pyridyl nickel dichloride (C13). In a manner similar to that described for C1,

C13 was prepared as a yellow powder in 91% yield. Anal. Calcd for C39H31Cl3N2Ni (690.09) C, 67.62; H, 4.51; N, 4.04%; Found: C, 67.52; H, 4.71; N, 4.00. FT-IR (Diamond; cm−1): 3060, 1616, 1596, 1568, 1495, 1429, 1318, 1180, 1027, 768, 698. Dalton Trans., 2012, 41, 11999–12010 | 12007


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Bis(2-((2,4-dibenzhydryl-6-methylphenylimino)methyl)pyridyl)nickel dibromide (D1). The ligand L1 0.264 g (0.5 mmol) and

Bis(2-((2,4-dibenzhydryl-6-ethylphenylimino)ethyl)pyridyl)nickel dibromide (D9). In a manner similar to that described for

(DME)NiBr2 0.154 g (0.25 mmol) was added to a Schlenk tube together with 10 ml of dried ethanol. The reaction mixture was then stirred for 12 h at room temperature and diethyl ether (10 ml) was added to precipitate the complex. The precipitate was washed with diethyl ether and dried in vacuum to obtain a yellow powder in 83% yield. Anal. Calcd for C78H64Br2N4Ni (1272.29) C, 73.43; H, 5.06; N, 4.39; Found: C, 73.24; H, 5.26; N, 4.21. FT-IR (Diamond; cm−1): 3025, 1630, 1596, 1494, 1446, 1301, 1077, 1037, 770, 744, 699.

D1, D9 was prepared as a yellow powder in 85% yield. Anal. Calcd for C82H72Br2N4Ni (1328.35) C, 73.94; H, 5.45; N, 4.21; Found: C, 74.00; H, 5.55; N, 4.01. FT-IR (Diamond; cm−1): 3058, 1621, 1596, 1494, 1446, 1375, 1321, 1259, 1026, 738, 698.

Bis(2-((2,4-dibenzhydryl-6-ethylphenylimino)methyl)pyridyl)nickel dibromide (D2). In a manner similar to that described for

D1, D2 was prepared as a yellow powder in 85% yield. Anal. Calcd for C80H68Br2N4Ni (1300.32) C, 73.69; H, 5.26; N, 4.30; Found: C, 73.56; H, 5.35; N, 4.14. FT-IR (Diamond; cm−1): 3024, 1629, 1595, 1493, 1447, 1301, 1077, 1037, 770, 744, 698. Bis(2-((2,4-dibenzhydryl-6-isopropylphenylimino)methyl)pyridyl)nickel dibromide (D3). In a manner similar to that described for

D1, D3 was prepared as a yellow powder in 83% yield. Anal. Calcd for C82H72Br2N4Ni (1331.98) C, 73.94; H, 5.45; N, 4.21; Found: C, 73.85; H, 5.68; N, 4.13. FT-IR (Diamond; cm−1): 2959, 1627, 1596, 1494, 1446, 1301, 1034, 768, 743, 699. Bis(2-((2,6-dibenzhydryl-4-methylphenylimino)methyl)pyridyl)nickel dibromide (D4). In a manner similar to that described for

D1, D4 was prepared as a yellow powder in 88% yield. Anal. Calcd for C78H64Br2N4Ni (1272.29) C, 73.43; H, 5.06; N, 4.39; Found: C, 73.34; H, 5.16; N, 4.21. FT-IR (Diamond; cm−1): 3295, 1630, 1597, 1493, 1446, 1197, 1028, 760, 698. Bis(2-((2,6-dibenzhydryl-4-isopropylphenylimino)methyl)pyridyl)nickel dibromide (D5). In a manner similar to that described for

D1, D5 was prepared as a yellow powder in 81% yield. Anal. Calcd for C82H72Br2N4Ni (1331.98) C, 73.94; H, 5.45; N, 4.21; Found: C, 73.80; H, 5.63; N, 4.12. FT-IR (Diamond; cm−1): 2960, 1635, 1597, 1492, 1444, 1157, 1075, 747, 699. Bis(2-((2,6-dibenzhydryl-4-chlorophenylimino)methyl)pyridyl)nickel dibromide (D6). In a manner similar to that described for

D1, D6 was prepared as a yellow powder in 82% yield. Anal. Calcd for C76H58Br2Cl2N4Ni (1312.18) C, 69.33; H, 4.44; N, 4.26; Found: C, 69.50; H, 4.51; N, 4.15. FT-IR (Diamond; cm−1): 3321, 1630, 1596, 1493, 1446, 1168, 1027, 760, 700. Bis(2-((2-benzhydryl-4,6-dimethylphenylimino)methyl)pyridyl)nickel dibromide (D7). In a manner similar to that described for

D1, D7 was prepared as a yellow powder in 83% yield. Anal. Calcd for C54H48Br2N4Ni (968.16) C, 66.76; H, 4.98; N, 5.77; Found: C, 66.75; H, 5.00; N, 5.61. FT-IR (Diamond; cm−1): 2894, 1631, 1591, 1493, 1444, 1305, 1129, 1025, 770, 744, 698. Bis(2-((2,4-dibenzhydryl-6-methylphenylimino)ethyl)pyridyl)nickel dibromide (D8). In a manner similar to that described for

D1, D8 was prepared as a yellow powder in 85% yield. Anal. Calcd for C80H68Br2N4Ni (1300.32) C, 73.69; H, 5.26; N, 4.30; Found: C, 73.59; H, 5.36; N, 4.20. FT-IR (Diamond; cm−1): 3033, 1622, 1595, 1493, 1445, 1372, 1319, 1259, 1026, 742, 698. 12008 | Dalton Trans., 2012, 41, 11999–12010

Bis(2-((2,4-dibenzhydryl-6-isopropylphenylimino)ethyl)pyridyl)nickel dibromide (D10). In a manner similar to that described for

D1, D10 was prepared as a yellow powder in 87% yield. Anal. Calcd for C84H76Br2N4Ni (1356.38) C, 74.18; H, 5.63; N, 4.12; Found: C, 74.08; H, 5.83; N, 4.02. FT-IR (Diamond; cm−1): 2967, 1620, 1596, 1494, 1446, 1371, 1261, 1032, 747, 700. Bis(2-((2,6-dibenzhydryl-4-methylphenylimino)ethyl)pyridyl)nickel dibromide (D11). In a manner similar to that described

for D1, D11 was prepared as a yellow powder in 88% yield. Anal. Calcd for C80H68Br2N4Ni (1300.32) C, 73.69; H, 5.26; N, 4.30; Found: C, 73.55; H, 5.32; N, 4.20. FT-IR (Diamond; cm−1): 3027, 1618, 1595, 1493, 1442, 1316, 1256, 1032, 767, 700. Bis(2-((2,6-dibenzhydryl-4-isopropylphenylimino)ethyl)pyridyl)nickel dibromide (D12). In a manner similar to that described for

D1, D12 was prepared as a yellow powder in 89% yield. Anal. Calcd for C84H76Br2N4Ni (1356.38) C, 74.18; H, 5.63; N, 4.12; Found: C, 74.00; H, 5.73; N, 4.02. FT-IR (Diamond; cm−1): 3025, 1621, 1596, 1493, 1442, 1255, 1070, 1035, 767, 700. Bis(2-((2,6-dibenzhydryl-4-chlorophenylimino)ethyl)pyridyl)nickel dibromide (D13). In a manner similar to that described

for D1, D13 was prepared as a yellow powder in 88% yield. Anal. Calcd for C78H62Br2Cl2N4Ni (1340.21) C, 69.67; H, 4.65; N, 4.17; Found: C, 69.77; H, 4.85; N, 4.07. FT-IR (Diamond; cm−1): 3025, 1618, 1596, 1493, 1437, 1320, 1257, 1176, 1031, 767, 700. General considerations

All manipulations of air- and moisture-sensitive compounds were performed under a nitrogen atmosphere using standard Schlenk techniques. Toluene was refluxed over sodium–benzophenone and distilled under nitrogen prior to use. Methylaluminoxane (MAO, 1.46 M solution in toluene) and modified methylaluminoxane (MMAO, 1.93 M in heptane, 3A) were purchased from Akzo Nobel Corp. Diethylaluminium chloride (Et2AlCl, 1.7 M in toluene) and ethylaluminium sesquichloride (Et3Al2Cl3, 0.87 M in toluene) were purchased from Acros Chemicals. High-purity ethylene was purchased from Beijing Yansan Petrochemical Co. and used as received. Other reagents were purchased from Aldrich, Acros, or local suppliers. 1H and 13 C-NMR spectra were recorded on a Bruker DMX 400 MHz instrument at ambient temperature using TMS as an internal standard. FT-IR spectra were recorded on a Perkin-Elmer System 2000 FT-IR spectrometer. Elemental analyses were carried out using a Flash EA 1112 microanalyzer. The molecular weights and molecular weight distributions of the polymers were determined by gel permeation chromatography (GPC) using a Waters Alliance GPC 2000 instrument equipped with a refractive index This journal is © The Royal Society of Chemistry 2012

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Table 7

Crystal data and structure refinement for C1·2CH3OH, C5·2H2O, D4, D7 and D9

Cryst. color Empirical formula Fw T (K) Wavelength (Å) Cryst. syst. Space group a (Å) b (Å) c (Å) α (°) β (°) γ (°) V (Å3) Z Dcalcd (mg m−3) μ (mm−1) F(000) Cryst size (mm) θ range (°) Limiting indices No. of rflns collected No. unique rflns [R(int)] Completeness to θ (%) Abs corr Data/restraints/params Goodness of fit on F2 Final R indices [I > 2σ(I)] R indices (all data) Largest diff peak and hole (e Å−3)

C1·2CH3OH

C5·2H2O

D4

D7

D9

Yellow C80H70Cl4N4Ni2O2 1380.64 173(2) 0.71073 Monoclinic P2(1)/n 18.888(16) 10.107(2) 20.625(4) 90 97.49(3) 90 3903.9(13) 2 1.175 0.664 1440 0.27 × 0.20 × 0.15 1.38–27.52 −24 ≤ h ≤ 15 −13 ≤ k ≤ 12 −26 ≤ l ≤ 26 19 692 8898 (0.0477) 99.2 Empirical 8898/0/403 1.114 R1 = 0.0637, wR2 = 0.1680 R1 = 0.0763, wR2 = 0.1779 0.537 and −0.519

Yellow C246H230Cl12N12Ni6O6 4228.08 173(2) 0.71073 Triclinic P1ˉ 18.912(4) 20.045(4) 22.057(4) 103.16(3) 109.38(3) 111.43(3) 6738(2) 1 1.042 0.578 2210 0.18 × 0.10 × 0.08 1.07–25.34 −22 ≤ h ≤ 22 −22 ≤ k ≤ 24 −26 ≤ l ≤ 25 54 230 24 513 (0.0615) 99.3 Empirical 24 513/11/1240 1.039 R1 = 0.0942, wR2 = 0.2709 R1 = 0.1276, wR2 = 0.2996 0.734 and −1.179

Yellow C54H48Br2N4Ni 971.49 173(2) 0.71073 Monoclinic P2(1)/c 14.822(3) 15.439(3) 9.767(2) 90 95.39(3) 90 2225.2(8) 2 1.450 2.274 996 0.20 × 0.12 × 0.10 1.38–27.55 −18 ≤ h ≤ 19 −20 ≤ k ≤ 12 −12 ≤ l ≤ 12 11 332 5083 (0.0512) 98.9 Empirical 5083/0/277 1.172 R1 = 0.0823, wR2 = 0.1943 R1 = 0.1072, wR2 = 0.2149 0.752 and −0.625

Yellow C78H64Br2N4Ni 1275.82 173(2) 0.71073 Triclinic P1ˉ 11.955(2) 12.075(2) 14.474(3) 94.80(3) 112.89(3) 93.79(3) 1907.0(6) 1 1.111 1.342 658 0.42 × 0.36 × 0.26 1.54–27.48 −15 ≤ h ≤ 15 −14 ≤ k ≤ 15 −26 ≤ l ≤ 26 17 090 8677 (0.0358) 99.2 Empirical 8677/0/385 1.070 R1 = 0.0538, wR2 = 0.1486 R1 = 0.0635, wR2 = 0.1538 0.570 and −0.552

Green C82H71Br2N4Ni 1330.96 173(2) 0.71073 Monoclinic P2(1) 15.921(3) 12.415(3) 18.706(3) 90 112.93(3) 90 3405.3(12) 2 1.299 1.506 1380 0.18 × 0.15 × 0.05 1.18–26.02 −19 ≤ h ≤ 19 −15 ≤ k ≤ 13 −23 ≤ l ≤ 20 15 957 11 537 (0.0466) 99.2% Empirical 11 537/40/882 1.076 R1 = 0.0779, wR2 = 0.1413 R1 = 0.0960, wR2 = 0.1536 0.600 and −0.419

(RI) detector and a set of u-Styragel HT columns of 106, 105, 104 and 103 pore size in series. The measurement was performed at 135 °C with 1,2,4-trichlorobenzene as the eluent at a flow rate of 0.95 mL min−1. Narrow-molecular-weight PS samples were used as standards for calibration.

Ethylene polymerizations were performed in a 250 mL autoclave stainless steel reactor equipped with a mechanical stirrer and a temperature controller. A 100 mL amount of toluene containing the catalyst precursor was transferred to the fully dried reactor under an ethylene atmosphere. The required amount of co-catalyst (MAO, MMAO or Et2AlCl) was then injected into the reactor via a syringe. At the desired reaction temperature, the reactor was sealed and pressurized to high ethylene pressure, and the ethylene pressure was maintained by feeding in ethylene. After the reaction mixture was stirred for the desired period, the pressure was released, and then the residual reaction solution was quenched with 5% hydrochloric acid in ethanol.

on a Rigaku Saturn724+ CCD with graphite monochromated Mo Kα radiation (λ = 0.71073 Å). Cell parameters were obtained by global refinement of the positions of all collected reflections. Intensities were corrected for Lorentz and polarization effects and empirical absorption. The structures were solved by direct methods and refined by full-matrix least squares on F2. All hydrogen atoms were placed in calculated positions. Structure solution and refinement were performed by using the SHELXTL-97 package.20 During structure refinement of C1·2CH3OH, C5·2H2O, D7 and D9, there were several disordered solvents that could neither be identified unambiguously nor be refined well. Therefore, it was impossible to determine the number and the identity of these disordered solvents definitively by means of single-crystal X-ray diffraction. The SQUEEZE option of the crystallographic program PLATON21 was used to remove these disordered solvents from the structures of C1·2CH3OH, C5·2H2O, D7 and D9; the geometry of the main compounds remained unaffected by employing SQUEEZE. Crystal data and processing parameters for C1·2CH3OH, C5·2H2O, D4, D7 and D9 are summarized in Table 7.

X-ray crystallography

Acknowledgements

Single-crystals of C1·2CH3OH, 3(C5·2H2O), D4, D7 and D9 suitable for X-ray diffraction were obtained by the slow diffusion of diethyl ether into the methanol solution. Data were collected

This work is supported by NSFC No. 20904059 as well as the MOST 863 program No. 2009AA034601. The EPSRC are thanked for the award of a travel grant (to CR).

Procedure for polymerization at higher ethylene pressure


Dalton Trans., 2012, 41, 11999–12010 | 12009

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References 1 (a) G. J. P. Britovsek, V. C. Gibson and D. F. Wass, Angew. Chem., Int. Ed., 1999, 38, 428; (b) S. D. Ittel, L. K. Johnson and M. Brookhart, Chem. Rev., 2000, 100, 1169; (c) S. Mecking, Coord. Chem. Rev., 2000, 203, 325; (d) V. C. Gibson and S. K. Spitzmesser, Chem. Rev., 2003, 103, 283; (e) F. Speiser, P. Braunstein and L. Saussine, Acc. Chem. Res., 2005, 38, 784; (f) W.-H. Sun, D. Zhang, S. Zhang, S. Jie and J. Hou, Kinet. Catal., 2006, 47, 278; (g) C. Bianchini, G. Giambastiani, G. I. Rios, G. Mantovani, A. Meli and A. M. Segarra, Coord. Chem. Rev., 2006, 250, 1391; (h) V. C. Gibson, C. Redshaw and G. A. Solan, Chem. Rev., 2007, 107, 1745; (i) Y. Song, S. Zhang, Y. Deng, S. Jie, L. Li, X. Lu and W.-H. Sun, Kinet. Catal., 2007, 48, 664; ( j) S. Jie, W.-H. Sun and T. Xiao, Chin. J. Polym. Sci., 2010, 28, 299; (k) C. Bianchini, G. Giambastiani, L. Luconi and A. Meli, Coord. Chem. Rev., 2010, 254, 431; (l) T. Xiao, W. Zhang, J. Lai and W.-H. Sun, C. R. Chim., 2011, 14, 851. 2 (a) B. L. Small, M. Brookhart and A. M. M. Bennett, J. Am. Chem. Soc., 1998, 120, 4049; (b) B. L. Small and M. Brookhart, J. Am. Chem. Soc., 1998, 120, 7143; (c) G. J. P. Britovsek, V. C. Gibson, B. S. Kimberley, P. J. Maddox, S. J. McTavish, G. A. Solan, A. J. P. White and D. J. Williams, Chem. Commun., 1998, 849; (d) G. J. P. Britovsek, M. Bruce, V. C. Gibson, B. S. Kimberley, P. J. Maddox, S. Mastroianni, S. J. McTavish, C. Redshaw, G. A. Solan, S. Strömberg, A. J. P. White and D. J. Williams, J. Am. Chem. Soc., 1999, 121, 8728. 3 (a) L. K. Johnson, C. M. Killian and M. Brookhart, J. Am. Chem. Soc., 1995, 117, 6414; (b) C. M. Killian, D. J. Tempel, L. K. Johnson and M. Brookhart, J. Am. Chem. Soc., 1996, 118, 11664; (c) S. A. Svejda, L. K. Johnson and M. Brookhart, J. Am. Chem. Soc., 1999, 121, 10634; (d) D. P. Gates, S. A. Svejda, E. Oñate, C. M. Killian, L. K. Johnson, P. S. White and M. Brookhart, Macromolecules, 2000, 33, 2320. 4 (a) L. K. Johnson, S. Mecking and M. Brookhart, J. Am. Chem. Soc., 1996, 118, 267; (b) S. Mecking, L. K. Johnson, L. Wang and M. Brookhart, J. Am. Chem. Soc., 1998, 120, 888; (c) S. R. Foley, R. A. Stockland, H. Shen and R. F. Jordan, J. Am. Chem. Soc., 2003, 125, 4350; (d) E. Drent, R. van Dijk, R. van Ginkel, B. van Oort and R. I. Pugh, Chem. Commun., 2002, 744; (e) E. Drent, R. van Dijk, R. van Ginkel, B. van Oort and R. I. Pugh, Chem. Commun., 2002, 964; (f) S. Luo and R. F. Jordan, J. Am. Chem. Soc., 2006, 128, 12072; (g) S. Luo, J. Vela, G. R. Lief and R. F. Jordan, J. Am. Chem. Soc., 2007, 129, 8946; (h) T. Kochi, S. Noda, K. Yoshimura and K. Nozaki, J. Am. Chem. Soc., 2007, 129, 8948; (i) W. Weng, Z. Shen and R. F. Jordan, J. Am. Chem. Soc., 2007, 129, 15450; ( j) C. Chen, S. Luo and R. F. Jordan, J. Am. Chem. Soc., 2008, 130, 12892; (k) S. Ito, K. Munakata, A. Nakamura and K. Nozaki, J. Am. Chem. Soc., 2009, 131, 14606; (l) C. Chen, S. Luo and R. F. Jordan, J. Am. Chem. Soc., 2010, 132, 5273; (m) K. Nozaki, S. Kusumoto, S. Noda, T. Kochi, L. W. Chung and K. Morokuma, J. Am. Chem. Soc., 2010, 132, 16030; (n) A. Nakamura, S. Ito, K. Munakata, T. Kochi, L. W. Chung, K. Morokuma and K. Nozaki, J. Am. Chem. Soc., 2011, 133, 6761; (o) S. Ito, M. Kanazawa, K. Munakata, J.-I. Kuroda, Y. Okumura and K. Nozaki, J. Am. Chem. Soc., 2011, 133, 1232. 5 (a) J. Pietsch, P. Braunstein and Y. Chauvin, New J. Chem., 1998, 22, 467; (b) W. Liu, J. M. Malinoski and M. Brookhart, Organometallics, 2002, 21, 2836. 6 N. A. Cooley, S. M. Green and D. F. Wass, Organometallics, 2001, 20, 4769. 7 (a) T. R. Younkin, E. F. Connor, J. I. Henderson, S. K. Friedrich, R. H. Grubbs and D. A. Bansleben, Science, 2000, 287, 460; (b) T. Hu, L.-M. Tang, X.-F. Li, Y.-S. Li and N.-H. Hu, Organometallics, 2005, 24, 2628; (c) L. Wang, W.-H. Sun, L. Han, Z. Li, Y. Hu, C. He and C. Yan, J. Organomet. Chem., 2002, 650, 59; (d) A. Kermagoret and P. Braunstein, Dalton Trans., 2008, 1564; (e) C. Carlini, M. Isola, V. Liuzzo, A. M. R. Galletti and G. Sbrana, Appl. Catal., A, 2002, 231, 307. 8 (a) W. Keim, S. Killat, C. F. Nobile, G. P. Suranna, U. Englert, R. Wang, S. Mecking and D. L. Schröder, J. Organomet. Chem., 2002, 662, 150; (b) F. Speiser, P. Braunstein and L. Saussine, Organometallics, 2004, 23, 2633; (c) F. Speiser, P. Braunstein, L. Saussine and R. Welter, Inorg. Chem., 2004, 43, 1649; (d) Z. Weng, S. Teo and T. S. A. Hor, Organometallics, 2006, 25, 4878; (e) Z. Guan and W. J. Marshall, Organometallics, 2002, 21, 3580. 9 (a) S. A. Svejda and M. Brookhart, Organometallics, 1999, 18, 65; (b) B. Y. Lee, X. Bu and G. C. Bazan, Organometallics, 2001, 20, 5425; (c) Z. L. Li, W. H. Sun, Z. Ma, Y. L. Hu and C. X. Shao, Chin. Chem.

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Lett., 2001, 12, 691; (d) J. M. Benito, E. De Jesús, F. J. de la Mata, J. C. Flores, R. Gómez and P. Gómez-Sal, Organometallics, 2006, 25, 3876; (e) X. Tang, W.-H. Sun, T. Gao, J. Hou, J. Chen and W. Chen, J. Organomet. Chem., 2005, 690, 1570; (f ) S. Jie, D. Zhang, T. Zhang, W.-H. Sun, J. Chen, Q. Ren, D. Liu, G. Zheng and W. Chen, J. Organomet. Chem., 2005, 690, 1739; (g) C. Shao, W.-H. Sun, Z. Li, Y. Hu and L. Han, Catal. Commun., 2002, 3, 405; (h) J. Li, T. Gao, W. Zhang and W.-H. Sun, Inorg. Chem. Commun., 2003, 6, 1372; (i) X. Tang, Y. Cui, W.-H. Sun, Z. Miao and S. Yan, Polym. Int., 2004, 53, 2155; ( j) G. J. P. Britovsek, S. P. D. Baugh, O. Hoarau, V. C. Gibson, D. F. Wass, A. J. P. White and D. Williams, Inorg. Chim. Acta, 2003, 345, 279; (k) R. Gao, L. Xiao, X. Hao, W.-H. Sun and F. Wang, Dalton Trans., 2008, 5645; (l) F. Yang, Y. Chen, Y. Lin, K. Yu, Y. Liu, Y. Wang, S. Liu and J.-T. Chen, Dalton Trans., 2009, 1243; (m) S. Song, T. Xiao, T. Liang, F. Wang, C. Redshaw and W.-H. Sun, Catal. Sci. Technol., 2011, 1, 69; (n) J. Yu, Y. Zeng, W. Huang, X. Hao and W.-H. Sun, Dalton Trans., 2011, 40, 8436; (o) L. Zhang, X. Hao, W.-H. Sun and C. Redshaw, ACS Catal., 2011, 1, 1213; ( p) J. Yu, X. Hu, Y. Zeng, L. Zhang, C. Ni, X. Hao and W.-H. Sun, New J. Chem., 2011, 35, 178; (q) W. Chai, J. Yu, L. Wang, X. Hu, C. Redshaw and W.-H. Sun, Inorg. Chim. Acta, 2012, 385, 21; (r) X. Hou, T. Liang, W.-H. Sun, C. Redshaw and X. Chen, J. Organomet. Chem., 2012, 708–709, 98. (a) T. V. Laine, U. Piironen, K. Lappalainen, M. Klinga, E. Aitola and M. Leskel, J. Organomet. Chem., 2000, 606, 112; (b) T. V. Laine, M. Klinga and M. Leskelä, Eur. J. Inorg. Chem., 1999, 959; (c) T. V. Laine, M. Klinga, A. Maaninen, E. Aitola and M. Leskel, Acta Chem. Scand., 1999, 53, 968; (d) A. Köppl and H. G. Alt, J. Mol. Catal. A: Chem., 2000, 154, 45; (e) Z. Huang, K. Song, F. Liu, J. Long, H. Hu, H. Gao and Q. Wu, J. Polym. Sci., Part A: Polym. Chem., 2008, 46, 1618; (f) T. V. Laine, K. Lappalainen, J. Liimatta, E. Aitola1, B. Löfgren and M. Leskelä, Macromol. Rapid Commun., 1999, 20, 487; (g) G. J. P. Britovsek, S. P. D. Baugh, O. Hoarau, V. C. Gibson, D. F. Wass, A. J. P. White and D. J. Williams, Inorg. Chim. Acta, 2003, 345, 279; (h) V. C. Gibson, C. M. Halliwell, N. J. Long, P. J. Oxford, A. M. Smith, A. J. P. White and D. J. Williams, Dalton Trans., 2003, 918. (a) Q.-Z. Yang, A. Kermagoret, M. Agostinho, O. Siri and P. Braunstein, Organometallics, 2006, 25, 5518; (b) P. Hao, S. Zhang, W.-H. Sun, Q. Shi, S. Adewuyi, X. Lu and P. Li, Organometallics, 2007, 26, 2439. F. Speiser, P. Braunstein and L. Saussine, Dalton Trans., 2004, 1539. (a) J. Hou, W.-H. Sun, S. Zhang, H. Ma, Y. Deng and X. Lu, Organometallics, 2006, 25, 236; (b) C. Zhang, W.-H. Sun and Z.-X. Wang, Eur. J. Inorg. Chem., 2006, 4895. (a) L. Wang, W.-H. Sun, L. Han, H. Yang, Y. Hu and X. Jin, J. Organomet. Chem., 2002, 658, 62; (b) F. A. Kunrath, R. F. Souza, Jr., O. L. Casagrande, N. R. Brooks Jr. and V. G. Young, Organometallics, 2003, 22, 4739; (c) N. Ajellal, M. C. A. Kuhn, A. D. G. Boff, M. Hörner, C. M. Thomas, J.-F. Carpentier, Jr. and O. L. Casagrande, Organometallics, 2006, 25, 1213; (d) W.-H. Sun, S. Zhang, S. Jie, W. Zhang, Y. Li, H. Ma, J. Chen, K. Wedeking and R. Fröhlich, J. Organomet. Chem., 2006, 691, 4196; (e) W.-H. Sun, K. Wang, K. Wedeking, D. Zhang, S. Zhang, J. Cai and Y. Li, Organometallics, 2007, 26, 4781; (f ) R. Gao, M. Zhang, T. Liang, F. Wang and W.-H. Sun, Organometallics, 2008, 27, 5641; (g) K. Wang, R. Gao, X. Hao and W.-H. Sun, Catal. Commun., 2009, 10, 1730. (a) J. Yu, H. Liu, W. Zhang, X. Hao and W.-H. Sun, Chem. Commun., 2011, 47, 3257; (b) W. Zhao, J. Yu, S. Song, W. Yang, H. Liu, X. Hao, C. Redshaw and W.-H. Sun, Polymer, 2012, 53, 130; (c) J. Yu, W. Huang, L. Wang, C. Redshaw and W.-H. Sun, Dalton Trans., 2011, 40, 10209. (a) H. Liu, W. Zhao, X. Hao, C. Redshaw, W. Huang and W.-H. Sun, Organometallics, 2011, 30, 2418; (b) H. Liu, W. Zhao, J. Yu, W. Yang, X. Hao, C. Redshaw, L. Chen and W.-H. Sun, Catal. Sci. Technol., 2012, 2, 415; (c) X. Hou, Z. Cai, X. Chen, L. Wang, C. Redshaw and W.-H. Sun, Dalton Trans., 2012, 41, 1617; (d) J. Lai, X. Hou, Y. Liu, C. Redshaw and W.-H. Sun, J. Organomet. Chem., 2012, 702, 52. T. Usami and S. Takayama, Polym. J., 1984, 16, 731. (a) E. F. Connor, T. R. Younkin, J. I. Henderson, A. W. Waltman and R. H. Grubbs, Chem. Commun., 2003, 2272; (b) V. C. Gibson, C. K. A. Gregson, C. M. Halliwell, N. J. Long, P. J. Oxford, A. J. P. White and D. J. Williams, J. Organomet. Chem., 2005, 690, 6271. G. B. Galland, R. F. de Souza, R. S. Mauler and F. F. Nunes, Macromolecules, 1999, 32, 1620. G. M. Sheldrick, SHELXTL-97 Program for the Refinement of Crystal Structures, University of Göttingen, Germany, 1997. A. L. Spek, Acta Crystallogr., Sect. D: Biol. Crystallogr., 2009, D65, 148.
