COMPLEXES OF COPPER(I)

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structure with phosphine bridges between the copper atoms. Thus, the composition of the .... borate was recrystallized from diglyme. Ammonia was distilled at a ...
CO M PLEXES OF COPPER(I) TETRAH YD R O BO R ATE W ITH O RGA NO M ETA LLIC AND POLYDEN TATE PHOSPHINE LIGANDS V. D. Makhaev, A. P. Borisov, N. K. Baranetskaya, V. D. Vil'chevskaya, Yu. Yu. Gorelikova, A. I. Krylova, and D. N. Kravtsov UDC 541.49:542.91 546.56:547.1 '118 M e th o d s f o r sy n th esizin g com p lexes o f copper(I) tetrahydroborate w ith o rg a n o m eta llic a n d p o ly d en ta te p h o sp h in e lig a n d s L xC u B H 4 [L = d ip h enylferrocenylphosphine, p h en yld iferro c en ylp h o sp h in e (x = 2). 1,1 '-bis(d ip h en ylp h o sphino)ferrocene. b isfd ip h e n ylp h o sp h m o jm eth a n e. 1.4-bis(d ip h en ylp h o sp h in o )b u ta n e, l,6 -b is(d ip h en vlp h o sp h in o )h exa n e, b is(2 -d ip h e n yl-p h o sp h in o eth y l)p h e n y lp h o sp h in e (x - I), 1 ,2 -b is(d ip h enylphosphino)ethane (x = /. 1.5)] have been developed. The electro n ic a b so rp tio n sp ectra o f the com pounds o b ta in e d in the visible region a n d their IR sp e c tra in the 200-3 6 0 0 -cm 1 ra n g e have been studied. It has been d isco v ered that in m o st o f the co m p o u n d s o b ta in e d the B H 4 g ro u p s are bidentate, w hereas in the co m p lex w ith the trip h o sp h in e P h P (C H 2C H 2P P h^)2 th ey are m onodentate. The com plexes w ith 1.2-bis(diphenylphosphino)~ eth a n e co n ta in both b id en ta te a n d m onodentate B H 4 groups. T etrahydroborato com plexes o f coppcr(l) which arc stabilized by organop ho sph orus ligands arc o f great theo ­ retical and practical interest as selective reducing agents in fine organic synthesis [I], as light- and heat-sensitive materials [2J, and as co m po nents o f system s for the storage o f solar energy [3], The structure and properties o f these c om p ou nd s depend to a large extent on the nature o f the stabilizing organop ho sph orus ligands [4). Only a feu tetrahydroborato com p lexes o f c op per with polydcntate phosphincs arc know n: |( P h ?P C = C P P h 2)3] ( C u B H 4)^ !5 ].fP h 2P (C H 2)3P P h 2|C u B H 4 |6 ] . |( P h 2P C H 2)3C C H 3]C uB H 4 [ 7 ] .|( P h 2P C H 2C H 2)3N ] C u B H 4 [81 .an d(P h2P C H 2C H 2P P h 2)C u B H 4 [9], N o c o m p o u n d s with ferroceny! derivatives o f phosphincs are know n In this c o m m u nication we shall describe m ethods for obtaining tetrahydroborato com plexes o f copper(I) stabilized by som e polydcntate and organom ctallic phosphincs. viz., (C 6H 5)2P ( C H 2)„P(C6H 5)2, w here n = 1 [b is(diphenylphosphino)m ethane, d pp m ], 2 [ 1,2-bis(diphenylphosphino)ethanc, dppe], 4 [ 1,4-bis(diphenvIphosphino)butane, dppb], 6 [1.6-bis(diphenylphosphino)hexane, dpphj, [(C6H 5)2P C H 2C H 2]2P C 6H 5 (triphos). dppf, P F c P h ?, and PFc-,Ph,

1,1 '-bis(diphenylph osphino)fcrrocene (dppf)

diphenylferrocenylphosphine (P F cP h 2)

phenvldiferrocenyl phosp hine (P F c 2Ph)

and w e shall exam ine som e physicochem ical properties o f the com po un ds synthesized.

A. N. N e sm e y a n o v Institute o f Organom etallic C o m p ou nd s, Russian A cadem y o f Scicnces. Institute o f New Chem ical Problem s, Russian A cad em y o f Sciences. Translated from K oo rdinatsion nay a K him iya, Vol. 18, No. 5, pp. 481-485, M ay, 1992. Original article subm itted D ecem ber 5, 199].

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0 3 6 4 -46 26/92 /1 80 5-04 16 $ 12.50 € 1 9 9 2 Plenum Publishing Corporation

T he com plexes w ere synthesized in an inert atmosphere. The solvents (pentane, benzene, and T H F ) were m ade absolute according to know n procedures. The ligands dppm , dppe, dppb, and dpph w ere obtained by reacting lithium diphenylph osp hide with the corresponding chloroalkanes in TH F. F c P h 2P and F c 2P hP were obtained by phosphorylating ferrocene with diphenylchloro- and p henyldichlorophosphine, respectively [10]. Preparations o f d p p f and tn p h o s from Aldrich were used without additional purification. Calcium tetrahydroborate was obtained by reacting calcium chloride with N a B H 4 in T H F [11], T he synthesis o f te tra hy droboratobis(tnethyl phosphite)copper(I) was previously described in [4], The electronic absorption spcctra were recorded on a Specord U V VIS sp ectrophotom eter in methylene chloride in the 325-700-nm range (/ = 2 cm, c = 0.01 M). The IR absorption spectra were recorded on U R -20 and IK S-22V spectrophotometers. T e t r a h y d r o b o r a t o [ l , l '- b i s ( d i p h e n y l p h o s p h i n o ) f e r r o c e n e ] c o p p e r ( I ) ( d p p f ) C u B H 4. A solution o f 0.25 g (0.45 m m o le ) o f d p p f in 15 ml o f benzene was given an addition o f 0.2 g (0.5 m m o le ) o f tetrahydroboratobis(triethyl phosphite)copper(l). The solution was stirred and left to stand overnight. T he finely crystalline precipitate form ed w as filtered out, w ashed with benzene and pentane, and dried in a vacuum . This gave 0.25 g ( - 9 0 % relative to dppf) o f a finely crystalline yellow ish orange substance. The com plexes ( d p p m )C u B H 4, (d p p b )C u B H 4, ( d p p h )C u B H 4, (trip h o s)C u B H 4, and (dppe), 5C u B H 4 were obtained with high yields in a similar m anner by adding an equ im olar quantity o f tetrahydroboratobis(triethyl phosphite)copper(I) to a solution o f the respective phosphine in benzene. In the case o f dppe, after (dppe), 5C u B H 4 was separated, the filtrate was evacuated in a vacuum until a dry residue form ed, and the residue was washed with pentane and dried in a vacuum. This gave a finely crystalline substance w ith m p 192°C, i.e., (d p p e )C u B H 4. The yield was -1 0 % . According to the literature data, the m elting point is 192°C [9], T e t r a h y d r o b o r a t o b i s ( d i f e r r o c c n y l p h e n y l p h o s p h i n e ) c o p p e r ( I ) (F c 2P h P ) 2C u B H 4. A solution o f 0 5 g ( - 1 m m ole) o f diferrocenylphenylphosphine in 75 ml o f T H F was given an addition o f 0.05 g (0.5 m m ole ) o f copper(I) chloride. The reaction mixture was stirred on a m agnetic stirrer and filtered. The filtrate was given an addition o f 0.02 g ( - 0 .3 m m ole) o f calcium tetrahydroborate, and the m ixture was stirred and left to stand overnight. Then the solution was filtered, and the solvent was driven off in a vacuum. The residue was dissolved in 15 ml o f benzene, and the solution was filtered, concentrated to a volum e o f 3 ml. and left to crystallize. The crystals precipitating were filtered and dried in a vacuum. This gave 0.4 g (an - 7 0 % yield) o f the finely crystalline substance (F c 2P h P )2C u B H 4. T e t r a h y d r o b o r a t o b i s ( f e r r o c e n y l d i p h e n y l p h o s p h i n e ) c o p p e r ( I ) ( F c P h 2P )2C u B H 4 was obtained in analogy to the preceding com plex The results o f the elemental analysis and the melting points o f the substances obtained are presented in Table 1. R E S U L T S AND D ISC U SSIO N The general m ethod for synthesizing tetrahydroborato com plexes o f copper(I) stabilized by o rgan oph ospho rus ligands is based on the reaction o f the com plexes o f cuprous chloride LxCuCI (L is an organo ph osp ho ru s ligand)

T A B L E 1. M elting Points and Results o f the Elemental Analysis o f the C o m p ou nd s Content (found/calculated), % Compound

mp, °C

j ti

C.u

V

11

5,78/5,(1 6 5 .90,5.90 6 .5 VO,3 9 6 .9 8 /6 ,8 1 6 .1 4/6,08 5.38/5,17 5,4 8 /'.,8 8 5 .1 7 /5 ,1 0

1 3 , 5 2 /1 3 ,7 . ! 9 .3 9 /9 ,4 0 1 2 ,00/12.59 11.06/11,92 1 0 .35/10.37 7 .6 8 /7 .7 6 5 / i 6 / 6 , 14 lt.53'10.03

1 3 .2 9 /1 3 ,3 9 1 3 . 8 /1 3 ,7 i 1 1 ,90/12,27 11 .1 5 11.6 2 14.8 15.16 8.0 3 /7 .5 7

2 .9 2 /2 .3 3 1,02/1,60 2 ,3 5 /2 ,1 4 2 .2 1 /2 .0 3 1 . 7 7 / 1 .7 6 I / i 2/1.32 1 , 5 8 / 1 ,0 4 1 .7 7 /1 ,7 1

I

(dppm)CuB H4 (dppe), sC uB H4 (dppb)CuBH4 (dpph)CuB H4 (triphos)CuBH4 (FcPh2P)2CuB H4 (F c2PhP)2CuB H4 (dppf)CuBH4

If)2 - If.4 171 -17 :i 1Wi - 192 tllti 1117 1 66 169 i:;ti - 1 3 8 Mu - r .t 2Ufi -2H8

65,21 .0 4 .8 8 68.5 4 /6 9 ,2 9 67,1)9/61;,61 68.18 /( 17,6 1 6 7 . 8 0 /(1 6 ,6 2 6 2 ..' 1 2 /6 1 5 4 6 0 .4 4 /6 0 .3 5 6 4 .29/04.54

9 . 6 9 '9,79

417

(dpp m) CuB H4 (dp pe)CuB H4 (dppe), 5CuB H4 (dppb)CuBH4 (d pph)CuBH4 (triphos)CuBH4 (F cPh2P)2CuB H4 ( F c 2PhP)2CuB H4 (dppf)CuBH4

2 ; « 2 . 2 :n;o

2:s80, 2 Ho 2 2385. 2.188, 2315 23118. 23% , 2307.

2360 2360 2,'iiiO 23fi0 2.WO 2354

v(B H X

6: HH!

VI i 'll!

1

|

|

Compound

i a 1 X 1

T A B L E 2. A ssig n m e n t o f So m e A bsorption B ands in the IR Spectra o f the C o m p o u n d s O btained (c m -1)

2018. 1111)5 2010, 1U5M

113 0 1 140

2055

1068 1140 1 1-'ii i KKlO

1985 (1)82. 2065 2005, ?0t>5.

195(1 tll'lO 11)60 11)50

2013.

1970

.;')>< 355

1 I'll)

1 t'.o I 1311

168

with sodium , lithium , or calcium tetrahydroborate in various organic solvents (an e th a n o l-c h lo ro fo rm mixture, diethyl ether, T H F ) H ow ever, in som e cases this m ethod is unsuitable due to the poo r solubility' o f the starting com po und s, the need to rem ove sodium , lithium, or calcium chloride and the excess phosp hine from the products, and the instability o f the products form ed under the reaction conditions [4|. W e discovered that the polydcntate phosphincs undergo an exchange reaction in organic solvents with tetrahydroborato c o m po und s o f copper(I) containing a trialkyl phosphite to form the corresponding phosphine com plexes o f copper(I) tetrahydroborate: P h 2P ( C H 2)„PPh, + [P(O R )3]2C u B H 4 -> [Ph2P (C H 2)„PPh2] C u B H 4 + 2 P (O R )3.

(1)

w here n = 1, 4, 6. T he reaction takes place at room temperature. T he reaction products precipitate, w hile the starting c om po un ds and the trialkyl phosphite form ed remain in the solution W e obtained the co m plexes L C u B H 4, w here L -- dppm , dppb. dpph, dppf. and triphos. with high yields under mild conditions by m eans o f this reaction. However, in the reaction with dppe. the expected product, i.e., (d p p c )C u B H 4. forms with only a small yield. The main reaction product is a com p o u n d w hose com position corresponds to the formula (dppe), 5C u B H 4, i.c, there arc three p hosphorus atoms for each copper atom. This com p o u n d apparently has a dim eric or oligomeric structure with p h osph in e bridges between the copper atoms. Thus, the com positio n o f the products o f the reaction under consideration depends on the length o f the m ethylene chain between the p ho sph oru s atoms: w hen n = 1. 4. 6, com plexes w ith P:C u = 2:1 form, and when n = 2, the main reaction product is the com plex (dppe), 5C u B H 4 with P:Cu = 3:1, which has not previously been described. T he reaction u nder consideration also makes it possible to obtain com plexes with m o no den tate phosphincs, for exam ple, with triphenylphosphine. H owever, the attempts to obtain com plexes with the ferrocenylphenylphosphines Fc^Phj ^P (x = 1, 2, 3) by m eans o f this reaction w ere unsuccessful, i.e.. the original com p o u n d s were recovered from the reaction mixture. At the same time, the reaction o f calcium tetrahydroborate w ith the com plex o f copper(I) chloride with the corresponding phosphine in T H F results in the form ation o f the com plexes ( F c P h 2P)2C u B H 4 and (F c 2P hP )2C u B H 4. In our opinion, the difference betw een the reactivities o f the fcrrocenvlphenylp ho sph in es and 1,1 '-bis(diphenylphosphino)ferrocene (dppf) m ay be attributed to the influence o f the chelate effect, w hich is the reason w h y bidentate d p p f undergoes exchange reaction (1), w hile the m onodentate ferrocenylphosphincs do not. All the copper(I) com plexes obtained in the present work, with the exception o f (d p p e )C u B H 4, are new c om pounds that were not previously know n They are colorlcss (in the case o f the organic phosphincs) or yellow ish orange (in the case o f the organom etallic phosphincs) c o m p oun ds, which are stable in air, soluble in chlorinated hydrocarbons, and insoluble in saturated hydrocarbons. The com plexes w ith P:Cu = 2:1 are m oderately soluble in arom atic hydrocarbons, and the c om p ou nd s with P:Cu = 3:1 are considerably less soluble in aromatic hydrocarbons. A long with the absorption bands assigned to the phosphine ligands in the IR spectra o f the com plexes obtained, there are absorption bands o f B H 4 groups covalently bonded to c opper atom s (Table 2). It was previously [4] show n that tetrahydroborato com plexes in w hich the copper atom is bonded to two phosphorus

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v, cm "1

Fig. 1. IR spectra o f (dppe), 5C u B H 4 and (d p p f)C u B H 4 (b).

i' atoms are characterized by bidentate coordination o f the B H 4 group

j

Cm

!’ ■))..

I

and that com plex es in which

it

there are three phosphorus atoms for each copper atom are characterized by m on od entate coordination ( C u - H - B H 3). A ccording to the IR-spcctroscopic data, a sim ilar picture is observed in the case o f organom etallic and polydcntate organic phosphincs The IR spectra o f (dppe), 5C u B H 4 and (trip h o s)C u B H 4 contained broadened absorption bands in the region o f the stretching vibrations o f BH bonds at 2350 and 2050 c m "1, w hich are characteristic o f m o nodentate B H 4 groups. The IR spectra o f the rem aining c o m po un ds in the region corres­ ponding to the stretching vibrations o f BH bonds arc typical o f copper(I) com plexes with bidentate coordination o f the B H 4 groups: a sharp intense absorption band at 2400 cm""1 and two intense bands near 2000 cm™1 (Fig. 1) The latter co m p o u n d s have an intense absorption band in the low-frequency portion o f the spectrum at 360 cm ’,

which we assigned to the vibrations o f the CuB bonds in a

-i

: ring |4], i!

The electronic absorption spectra o f (dpp f)C uB H 4 and (Fc2P h P ) ,C u B H 4 and the corresponding free phosphincs exhibit an absorption band in the visible region at 450 nm, and no appreciable displacem ent o f this band occurs upon com plexation. The copper(I) com plexes which w e obtained with polydcntate organic phosphincs do not have absorption bands in the visible region. It has been reported that som e copper(I) com plexes catalyze the valence isomerization o f n o rb o m a d ie n e to quadricyclane [3, 12, 13], This proccss is the basis o f one o f the p rom ising m ethods for storing solar energy. W e suggest that the colored tetrahydroborato com plexes o f copper(I) with fe rrocenylphenylphosphine ligands that we obtained will display catalytic properties in this reaction. L I T E R A T U R E C I T ED 1. 2. 3. 4. 5.

G. W. J. Fleet and P. J. C. Harding, Tetrahedron Lett., 22, No. 7, 675 (1981). H. J. Gysling and R. S. Vinal, U.S.A. Patent No. 3,859,092; Referat. Zh. K him ., 2 0 N 2 5 2 P (1975). C. Kutal and P. A. Grutsch, Adv. Chcm. Ser., No. 173, 325 (1979). V. D. M akhaev, A. P. Borisov, E. B. Lobkovskii, et al., Izv. Akad. N au k S S S R , Ser. K him ., No. 8, 1881 (1985). A. J. Carty and A. Efraty, Inorg. Chem ., 8, No. 3, 543 (1969).

419

6. 7. 8. 9. 10. 11. 12. 13.

S. W. Orchard and C. Kutal, Inorg. Chim. Acta, 64, No. 2, L95 (1982). C. A. Ghilardi, S. M ido llim , and A. Orlanolini, Inorg. C hem ., 21, No. 11, 4096 (1982). C. Bianchini, C. A. Ghilardi, A. Meli, et al., Inorg. C hem ., 24, No. 6, 924 (1985). F. Cariati and L. N aldini, G azz Chim. Ital., 95, No. 1, 3 (1965). G. P. Sollott, H. E. M erw ov, S. Portnoy, and J. L. Snead, J. Org. Chem ., 28, No. 4, 1090 (1963). L. V. Titov, Zh. Neorg. K him ., 13, No. 7, 1797 (1968). P. A. Grutsch and C Kutal, J. Am. C hem . Soc., 108, No. 1 1 ,3 1 0 8 (1986). M. Onishi, K. Hiraki, H. Itoh, et al., Inorg. Chim. Acta, 145, No. 1, 105 (1988).

AM M IN ET ET R A H Y D R O BO R A T O CO M PLEXES OF 3d M ETALS V. D. Makhaev, A. P. Borisov, and L. A. Petrova

U D C 54 1.49:546.171:546.271:546.3

The rea ctio n s o f g a seo u s a m m o n ia w ith the tetra h vd ro fu ra n a tes M n(B H 4) n x T H F or the com plexes N a M " (B H 4) nk,-S D M E in the respective organic solvents, i.e., tetra h yd ro fu ra n or 1,2-dim ethoxyethane, g ive a m m in etetra h yd ro b o ra to com plexes o ftita n iu m (III), vanadium (111), chrom ium (II), a n d m anganese(II). The co m p o u n d s have been ch a ra cterized by data fro m ch em ica l a n a lysis a n d th erm o g ra p h ic a n d IR -sp ectro sco p ic investigations. The dependence o f the p ro p e rtie s o f the a m m in es on the n ature o f the centra! atom in the series o f 3 d m etals has been discussed. The a m m inetetrahydroborato com plexes o f transition metals M " (N H ,)m( B H 4),] arc o f great interest as potential sourccs o f gaseous hydrogen and as starting c om po un ds for the synthesis o f metal nitrides, metal borides, and boron nitride under mild conditions. In the case o f 3 d metals, hex aam m inetetrahy drob orato com p lex es o f scandium(III). c h ro m iu m (lll). cobalt(II), cobalt(III), nickel(II), and iron(II) have been obtained [1-4], In this com m u nicatio n we shall describe the synthesis o f the previously u n kn ow n hexaam m inctctrah> droborato com plexes o f titanium (III), titanium(I), vanadium(III), vanadium (II), chrom ium (II), chrom ium (III), m anganesc(II). and m angancse(IV ), we shall exam ine som e p hysicochem ical properties o f the c o m p oun ds obtained, and wc shall com pare them to the properties o f the know n a m m inetetrahydroborato com plexes o f 3 d metals. EXPERIMENTAL All the operations were earn e d out in an inert atm osphere (argon, nitrogen) or in a vacuum . D im etho xy ethanc (D M E ) and tetrahydrofuran (T H F) were distilled ov er lithium tetrahydroalum inatc before use. Pure-grade anhydrous chrom ium (I I) chloride w as used w ithout additional purification. Technical-grade sodium tetrahydro­ borate was recrystallized from diglyme. A m m o n ia was distilled at a reduced tem perature over metallic sodium. The tetrahydroborato com plexes o f titanium , vanadium , and m anganese were obtained according to know n methods [4-6], The IR spectra were recorded on U R -2 0 and IK S-22V spectrophotom eters. T he samples used to record the IR spectra w ere prepared in the form o f a suspension in liquid petrolatum (a capillary layer) or in the form o f a pow der between K B r or Csl w indows.

Institute o f New Chem ical Problem s, Russian A cadem y o f Sciences. T ranslated from K oordinatsio nnaya K him iya, Vol. 18. No. 5, pp. 486-491, M ay, 1992. Original article subm itted D ecem ber 11, 1991.

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