Journal of Organometallic Chemistry 869 (2018) 26e36
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Synthesis of strained complexes of arene d6 metals with benzoylthiourea and their spectral studies Ibaniewkor L. Mawnai a, Sanjay Adhikari a, Werner Kaminsky b, Mohan Rao Kollipara a, * a b
Centre for Advanced Studies in Chemistry, North Eastern Hill University, Shillong 793 022, India Department of Chemistry, University of Washington, Seattle, WA 98195, USA
a r t i c l e i n f o
a b s t r a c t
Article history: Received 29 March 2018 Received in revised form 21 May 2018 Accepted 27 May 2018 Available online 30 May 2018
Halide bridged arene d6 platinum group metal precursors on treatment with thiourea derivatives (L1 and L2) yielded a series of neutral mono-dentate complexes (1e8). In general complexes have been formulated as [(arene)M(L)к1(S)Cl2] where L ¼ L1, M ¼ Ru, arene ¼ p-cymene 1; benzene 2; arene ¼ Cp*, M ¼ Rh 3 and Ir 4; L ¼ L2, M ¼ Ru, p-cymene 5; benzene 6; arene ¼ Cp*, M ¼ Rh 7 and Ir 8. Structural studies revealed that thiourea ligand coordinate to the metal in a mono-dentate fashion via S atom. Further treatment of mono-dentate complexes 1 and 5 with NaN3 in polar solvent resulted in the formation of highly strained к2(N,S) azido complexes 9 and 10 whereas reaction of complex 7 yielded a six membered ring к2(S,O) azido complex 11. Reaction of complex 9 with dimethylacetylene dicarboxylate (DMAD) and diethylacetylene dicarboxylate (DEAD) leads to the formation of nitrogen (N2) bound triazolato complexes 12 and 13 whereas reaction of complex 11 with the same yielded nitrogen (N1) bound triazolato complexes 14 and 15. However reaction of complex 10 with both DMAD and DEAD leads to decomposition of the products. All these complexes have been characterized by various spectroscopic techniques. The molecular structures of the representative complexes 1, 2, 3, 6, 7, 9, 11 and 12 have been determined by single crystal X-ray diffraction study. © 2018 Elsevier B.V. All rights reserved.
Keywords: Ruthenium Rhodium Iridium Thiourea Triazole
1. Introduction Arene metal complexes have emerged as versatile intermediates in the organic synthesis due to the availability of three labile coordinate sites and rigid arene ring occupying another three coordinate sites [1,2]. Considering the hydrocarbon ligand occupying a three coordination site, the geometry about the metal center in these complexes is pseudo octahedral. Besides their applications as catalyst precursors for hydrogen transfer [3,4], ring opening metathesis polymerization [5,6], and olefin oxidation [7], the organometallic complexes of arene ruthenium [8,9] and Cp* rhodium and Cp*iridium complexes have attracted considerable current interest due to their potential anticancer activity [10e14]. Some of the d6 metal complexes of ruthenium(II) [15,16], rhodium(III) [17] and iridium(III) [18,19] have also been found to inhibit the tumors by their selective interactions towards the biomolecules. We are currently interested in the coordination chemistry of N,
* Corresponding author. E-mail addresses:
[email protected],
[email protected] (M.R. Kollipara). https://doi.org/10.1016/j.jorganchem.2018.05.023 0022-328X/© 2018 Elsevier B.V. All rights reserved.
N di(alkyl/aryl)-N0 -benzoylthiourea ligands in view of the interesting and versatile coordination behavior of these ligands towards transition metals. The coordination chemistry of the N, N-dialkylN-aroylthioureas with transition metals was first explored by the €nig et al. [21]. groups of Hoyer and co-workers [20], and later by Ko The presence of sulfur and oxygen as soft and hard donors provides multitude of bonding possibilities to thiourea derivatives [22,23]. The thiourea ligand coordinates to the metal center by four coordination modes viz., monobasic bidentate (O, S) [24], neutral monodentate (S) [25], neutral bidentate (O, N) [26] and monobasic bidentate (N, S). Among these, the monobasic bidentate (O and S) coordination mode is very common, but the coordination through S and N, S are uncommon and are observed only in few transition metal complexes. The mono-dentate coordination mode was explained mainly on the basis of intramolecular hydrogen bond formation between the carbonyl O atom and the thiourea NH group [27]. The recent interest towards these complexes has arisen mainly due to their biological activities such as anticancer, antimicrobial, antifungal, antimalarial, antibacterial and antituberclosis [28e31]. Previous studies in this laboratory have reported half-sandwich arene ruthenium, rhodium and iridium complexes with pyridyl
I.L. Mawnai et al. / Journal of Organometallic Chemistry 869 (2018) 26e36
thiourea ligands [32,33]. The chemosensitivity of arene d6 metal complexes with N-phenyl-N0 -(pyridyl/pyrimidyl) thiourea derivatives has also been studied by our group [34]. In continuation to our previous work, herein we report the synthesis and characterization of a series of neutral mono-dentate half-sandwich arene ruthenium, rhodium and iridium complexes containing alkyl/aryl thiourea derivatives and their reactivities with azide and alkynes. Ligands used in this study are shown in (Chart 1). 2. Experimental 2.1. Materials and methods The reagents were of commercial quality and used without further purification. Metal salts RuCl3.nH2O, RhCl3.nH2O and IrCl3.nH2O were purchased from Arora Matthey Limited. a-phellandrene, pentamethylcyclopentadiene, were purchased from Sigma Aldrich. Benzoyl chloride, ammonium thiocyanate, diethylamine, diphenylamine, sodium azide, DMAD and DEAD were obtained from Spectrochem, Alfa Aesar and s. d. fine Chem. Pvt. Ltd. The solvents were dried and distilled prior to use according to standard procedures [35]. Precursor metal complexes [(arene) RuCl2]2 (arene ¼ p-cymene/benzene) and [Cp*MCl2]2 (M ¼ Rh/Ir) were prepared according to the published procedures [36,37]. The thiourea ligands N-(diphenylcarbamothioyl)benzamide L1, and N-(diethyl -carbamothioyl)benzamide, L2 were prepared according to reported procedures [38]. 1H NMR spectra were recorded on a Bruker Avance II 400 MHz spectrometer using CDCl3 as solvent; chemical shifts were referenced to TMS. Infrared spectra (KBr pellets; 400-4000 cm1) were recorded on a Perkin-Elmer 983 spectrophotometer. Mass spectra were recorded with WATERS (ZQ4000) using acetonitrile as solvent. Absorption spectra were recorded on a Perkin-Elmer Lamda 25 UVeVis spectrophotometer in the range of 200e800 in acetonitrile at room temperature. All these complexes were synthesized and characterized by using FTIR, 1H NMR, ESI Mass, UV- Vis, and single-crystal X-ray diffraction techniques. 2.2. Structure determination by X-ray crystallography Single crystal data for the complexes were collected with an Oxford Diffraction Xcalibur Eos Gemini diffractometer using graphite monochromated Mo-Ka radiation (l ¼ 0.71073 Å). The strategy for the data collection was evaluated using the CrysAlisPro CCD software. Crystal data were collected by standard ‘‘phieomega scan’’ techniques and were scaled and reduced using CrysAlisPro RED software. The structures were solved by direct methods using SHELXS-97 and refined by full-matrix least squares with SHELXL97 refining on F2 [39,40]. The positions of all the atoms were obtained by direct methods. Metal atoms in the complex were located from the E-maps and all non-hydrogen atoms were refined anisotropically by full-matrix least-squares. Hydrogen atoms were placed in geometrically idealised positions and constrained to ride
Chart 1. Ligands used in this study.
27
on their parent atoms with C-H distances in the range 0.95e1.00 A. Isotropic thermal parameters Ueq were fixed such that they were 1.2Ueq of their parent atom Ueq for CH's and 1.5Ueq of their parent atom Ueq in case of methyl groups. Crystallographic and structure refinement parameters for the complexes are summarized in Tables 1 and 2 and selected bond lengths and bond angles are presented in Tables 3 and 4. Figs. 1e3 were drawn with ORTEP-3 program. Crystal structure of complex 6 contains two molecules of CHCl3 in the solved structure. Due to low theta value the molecular structure of complex 11 is presented here to know the composition of the molecule. 2.3. General procedure for synthesis of metal complexes (1e8) A mixture of metal precursor [(arene)MCl2]2 (arene ¼ p-cymene/benzene) and [Cp*MCl2]2 (M ¼ Rh/Ir) complexes (0.1 mmol) and thiourea derivatives (L1 and L2) (0.2 mmol) were dissolved in dry dichloromethane (10 ml) and stirred at room temperature for 8 h (Scheme 1). The solution was filtered through a bed of celite to remove unreacted material. The solvent was concentrated under reduced pressure to 2e3 ml and on addition of 30 ml hexane, red orange compound precipitated out. The precipitate was then washed with hexane (2 5 ml) and diethyl ether (3 10 ml) and air dried. 2.3.1. [(p-cymene)Ru(к1(S)-L1)Cl2] (1) Color: Red; Yield: 65%; FT-IR (KBr, cm1): 3421 (ʋN-H), 1697 (ʋC] ), 1228 (ʋC]S); 1H NMR (400 MHz, CDCl3): d ¼ 11.30 (s, 1H, NH), O 8.14 (d, J ¼ 8 Hz, 2H), 7.67 (t, J ¼ 8 Hz, 1H), 7.58 (t, J ¼ 4 Hz, 2H), 5.28 (d, J ¼ 8 Hz, 2H, CH(p-cym)), 4.95 (d, J ¼ 4 Hz, 2H, CH(p-cym)), 4.12 (q, J ¼ 2 Hz, 2H), 3.57 (q, J ¼ 4 Hz, 2H), 2.80 (sept, 1H, CH(p-cym)), 1.97 (s, 3H, CH(p-cym)), 1.50 (t, J ¼ 6 Hz, 3H), 1.29 (t, J ¼ 8, 3H), 1.23 (d, J ¼ 8, 6H); ESI-MS (m/z): 471.03 [M 2Cl]2þ; UVeVis {Acetonitrile, lmax nm (ε/104 M1 cm1)}: 240 (4.527), 287 (2.494), 422 (0.185). 2.3.2. [(benzene)Ru(к1(S)-L1)Cl2] (2) Color: Red; Yield: 70%; FT-IR (KBr, cm1): 3433 (ʋN-H), 1690 (ʋC] ), 1192 (ʋC]S); 1H NMR (400 MHz, CDCl3): d ¼ 11.25 (s, 1H, NH), O 8.13 (d, J ¼ 8 Hz, 2H), 7.69 (t, J ¼ 8 Hz, 1H), 7.60 (t, J ¼ 8 Hz, 2H), 5.48 (s, 6H, CH(benzene)), 4.14 (q, J ¼ 8 Hz 2H), 3.58 (q, J ¼ 4 Hz 2H), 1.50 (t, J ¼ 8 Hz, 3H), 1.29 (t, J ¼ 8 Hz, 3H); ESI-MS (m/z): 414.88 [M 2Cl]2þ; UVeVis {Acetonitrile, lmax nm (ε/104 M1 cm1)}: 240 (2.779), 287 (1.696), 422 (0.113). 2.3.3. [Cp*Rh(к1(S)-L1)Cl2] (3) Color: Red; Yield: 72%; FT-IR (KBr, cm1): 3432 (ʋN-H), 1687 (ʋC] 1 O), 1230 (ʋC]S); H NMR (400 MHz, CDCl3): d ¼ 11.57 (s, 1H, NH), 8.08 (d, J ¼ 8 Hz, 2H), 7.59 (t, J ¼ 8 Hz, 1H), 7.51 (t, J ¼ 8 Hz, 2H), 4.11 (q, J ¼ 2 Hz, 2H), 3.51 (q, J ¼ 4 Hz, 2H), 1.52 (s, 15H, CH(Cp*)), 1.47 (t, J ¼ 8 Hz, 3H), 1.27 (t, J ¼ 8 Hz, 3H); ESI-MS (m/z): 473.03 [M 2Cl]2þ; UVeVis {Acetonitrile, lmax nm (ε/104 M 1 cm-1)}: 233 (1.649), 258 (1.568), 422 (0.154). 2.3.4. [Cp*Ir(к1(S)-L1)Cl2] (4) Color: Yellow orange; Yield: 68%; FT-IR (KBr, cm1): 3433 (ʋN-H), 1673 (ʋC]O),1230 (ʋC]S); 1H NMR (400 MHz, CDCl3): d ¼ 11.65 (s, 1H, NH), 8.07 (d, J ¼ 4 Hz, 2H), 7.60 (t, J ¼ 8 Hz, 1H), 7.52 (t, J ¼ 8 Hz, 2H), 4.09 (q, J ¼ 2 Hz, 2H), 3.53 (q, J ¼ 4 Hz, 2H), 1.67 (t, J ¼ 8 Hz, 3H), 1.49 (s, 15H, CH(Cp*)), 1.28 (t, J ¼ 8 Hz, 3H); ESI-MS (m/z): 563.18 [M 2Cl]2þ; UVeVis {Acetonitrile, lmax nm (ε/104 M1 cm1)}: 244 (3.298), 351 (0.780). 2.3.5. [(p-cymene)Ru(к1(S)-L2)Cl2] (5) Color: Red; Yield: 73%; FT-IR (KBr, cm1): 3433 (ʋN-H), 1638 (ʋC] 1 O), 1235 (ʋC]S); H NMR (400 MHz, CDCl3): d ¼ 11.69 (s, 1H, NH),
28
Table 1 Crystal data and structure refinement parameters of complexes. 1
2
3
6
7
Empirical formula Formula weight Temperature (K) Wavelength (Å) Crystal system Space group a (Å)/a ( ) b (Å)/b ( ) c (Å)/g ( ) Volume (Å3) Z Density (calc) (Mg/ m3) Absorption coefficient (m) (mm1) F(000) Crystal size (mm3) Theta range for data collection Index ranges
C22H30Cl2N2ORuS 542.53 293(2) 0.71073 triclinic Pı 9.4914(3)/72.006(4) 13.7486(6)/81.992(3) 19.1107(8)/89.164(3) 2347.65(17) 2 1.535
C18H22Cl2N2ORuS 486.42 293(2) 0.71073 monoclinic P 21/n 15.5421(10)/90 7.4931(5)/108.933(7) 17.7913(12)/90 1959.9(2) 4 1.648
C22H31Cl2N2ORhS 545.36 293(2) 0.71073 monoclinic P 21/c 7.1419(6)/90 26.466(2)/94.439(7) 13.4584(9)/90 2536.2(4) 4 1.428
C26H22Cl2N2ORuS,2(CHCl3) 821.22 293(2) 0.71073 triclinic Pı 11.0165(6)/79.064(4) 11.7169(6)/70.326(4) 14.2278(5)/77.663(4) 1675.47(15) 2 1.628
C30H31Cl2N2ORhS 641.46 293(2) 0.71073 Monoclinic P21/c 11.0679(4)/90 24.5959(10)/99.057(4) 21.3741(10)/90 5746.0(4) 4 1.483
1.000
1.188
0.981
1.194
0.879
1112.0 0.25 0.19 0.12 3.236e29.054
984 0.29 0.25 0.12 3.113e29.085
1120 0.29 0.25 x 0.12 3.079e29.059 .
820 0.23 0.21 x 0.15 3.201e29.064
2624 0.25 0.13 x 0.12 3.328e29.019 .
12 h 12, 18 k 18, 25 l 23 21 h < 21, 10 k
