Organometallics 1982,1, 1640-1644
1640
Two Reactions of Bis(d1phenylphosphino)acetylene with Ta,CI,( SMe,),. Dlnuclear Products with Coupled Acetylenes and or Ringst F. Albert Cotton,' Larry R. Falvello, and Robert C. Najjar Department of Chemistry, Texas ABM University, College Station, Texas 77843
Received May 11, 1982
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The tantalum compound Ta2C&(SMeZ),reacts with Ph2PC=CPPh2to give either of two producb, 1 or 2, depending on the mole ratio of reactants used. If a 1:l ratio is used, 1, with a molecular formula Cl4Ta-CH(PPh2)C(PPh2)-C(PPh2)CH(PPh2)-TaC1,.2CH2Cl2, is obtained. When a mole ratio of 1:2 is used, the related compound 2, having two fewer hydrogen atoms and two Ta=C double bonds, r (M@)Cl,Ta=C (PPh2)C(PPh2)=C (PPh2)C(PPh2)=TaC13(SMed,is obtained. Both compounds have been identified and structurally characterized by X-ray crystallography. 1 forms monoclinic crystals in space group P2,/n with unit-cell dimensions a = 11.884 (2)A,b = 14.143 (4)A,c = 17.681 (5)A,0 = 94.26 (1)O, V = 2963 (2)A,, and 2 = 2. Compound 2 also forms monoclinic crystals in space group ??&Inwith a = 14.851 (4)A,b = 12.245 (6)A,c = 15.848 (4)A,/3 = 97.32', V = 2858 (3)A3, and Z = 2. In each compound the starting acetylene has dimerized to form a four-carbon chain and the tantalum has increased ita oxidation state from I11 to V. In each case the molecule resides on a crystallographic inversion center. In 1 each Ta atom has distorted octahedral coordination supplied by four C1 atoms, one P atom, and a Ph2P-CHgroup that forms a three-membered Ta-C-P ring with Ta-P = 2.555 (5)A and Ta-C = 2.326 (13)A. In 2 the coordination is similar except that there is a Ph2P-C- group coordinated and trans to it a Me2Sligand in place of C1. The three-membered Ta-C-P ring has Ta-P = 2.471 (3)A and Ta=C = 2.018 (10)A. The reactions leading to these compounds are not understood mechanistically. Systematic names for 1 and 2 are octachloro[~-[1,2,3,4tetrakie(diphenylphosphino)-2-butne-1,4diyl-C1Q1QB:CU~~]]ditantalum and hexachloro[r-[1 , 2 , 3 , 4 t e t r a k i s ( d i p h e n y l p h o s p h i n o ) - 2 - b ~ ~ n ~ l , 4 ~ y ~ d e n ~ C ~ ~ ~ ~ ~ ~ ~ ] ] b ~ ( d ~ e sulfide)ditantalum,respectively. The structure of 1 was refined with 2480 data to fiial least-squares residuals R = 0.061 and R, = 0.068. The refinement of 2 involved 2971 reflections and gave final residuals R = 0.061 and R , = 0.074.
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Introduction Previous studies in this laboratory have examined the reactions of acetylenes with the tantalum and niobium compounds of the type M2C&(THT),, where T H T represents tetrahydrothiophene.14 In several caseslJ the isolated products were mono- or dinuclear complexes containing the acetylene molecules coordinated to one or two metal atoms. With certain acetylenes, however, polymerization occurred' to form either cyclic trimers (substituted benzenes) or high molecular weight linear polymers. In addition to these studies we have been exploring the chemistry of tantalum(II1) more g e n e r a l l ~and , ~ in the course of this work we have found that the compound Ta2Cl@Me2), is a convenient and useful reagent6 for preparing a variety of tantalum(II1) compounds. In this paper we report the results of an investigation of the reaction of Ta2C&(SMd3with the unusual acetylene Ph2PC=CPPh2. The results are quite different from any previously obtained. Neither polymers nor simple (alkynelmetal complexes have been isolated. Instead, complex reactions occur in which the acetylene is dimerized to give a 1,2,3,4-tetraphosphinobut-2-enediyl chain, which then complexes tantalum with the formation of P-C-Ta or P-C=Ta rings. The compounds to be described in this paper are 1, octachloro[p-[1,2,3,4-tetrakis(diphenylphosphino)-2-butene-1,4-diyl-C1Q1QB:C4gP,P]]ditantalum and 2, hexachloro[p-[1,2,3,4-tetrakis(diphenylphosphino)-2-butene-l,4-diylidene-C1,P1~C4,P~]] bis(dimethyl su1fide)ditantalum.
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'Dedicated to the memory of Rowland G. Pettit.
Experimental Section Bis(diphenylphoephino)acetylene,dppa, was prepared according to the literature method.' TazC&(SMez)3 was prepared as previously described! Dichloromethane and hexane were distilled over PzO6 and potassium benzophenone ketyl, respectively. All manipulationsof materials were carried out under anaerobic and anhydrous conditions by using vacuum line, syringe, and Schlenk methods. The infrared spedra were recorded on a Unicam SPllOO spectrometer. , Preparation of Cl,Ta+H(PPh2)C(PPh2)=C(PPh2)CH-
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(PPhz)-TaC1,.2(CH2C12), 1. TazCl&3Me2)3,100 mg (0.13 mmol), WBB dissolved in 5 mL of dichloromethaneand the solution transferred to a Schlenk tube via syringe. Dichloromethane (15 mL) was carefully layered over the Ta2C&(SMe2)3 solution. One equivalent of dppa, 50 mg (0.13mmol), was dissolved in 5 mL of dichloromethane and the solution layered on top of the dichloromethane stratum in the Schlenk tube. The diffusion of the reactants proceeded over a period of approximately 1 week, which yielded a maroon solution and a small amount of light brown precipitate. The solution was filtered through a Celite pad, and about 8 mL of the filtrate was transferred to another Schlenktube. The maroon filtrate was covered with a layer of 20 mL of hexane. As diffusion proceeded, the maroon solution turned brown within ~~~
(1) Cotton, F. A.; Hall, W. T. J. Am. Chem. SOC. 1979,101,5094; Inorg. Chem. 1980,19, 2352. (2) Cotton, F. A.; Hall, W. T. Inorg. Chem. 1980, 19, 2354. (3) Cotton, F. A.; Hall, W. T. Znorg. Chem. 1981,20, 1285. (4) Cotton, F. A.; Hall, W. T.; Cam, K. J.; Karol, F.J. Macromolecules 1981, 14, 233. (5) Cotton, F. A.; Falvello, L. R.; Najjar, R. C., two reports in preas in Inorg. Chem. (6)Cotton, F. A.; Najjar, R. C. Inorg. Chem. 1981,20, 2716. (7) Carty, A. J.; Efraty, A. Inorg. Chem. 1969, 8, 543.
0276-7333/82/2301-l640$01,25/00 1982 American Chemical Society
Two Reactions of Ph2pC=CPPh2 with Ta2C16(SMe2)3
Organometallics, Vol. 1, No. 12, 1982 1641
Table I. Crystallographic Parameters for 1 and 2 parameter 1 2 ~~
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space group a, A b, A c, A 0, deg d" A , glcm3
P2,ln 11.884 ( 2 ) 14.143 (4) 17.681 (5) 94.26 ( 1 ) 2963 (.2 .) 1.81
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fw crystsize,mm. ~ ( M oKa), cm-' range 2e, deg no. of unique data no. of data, Fo2 > 3p(FO2) no. of variables
1605.99 0.20X0.31X0.25 43.358 0-50 3143
1463.44 0.28X0.32X0.40 42.81 0-48 3463
24 80
2971
326 0.061 0.068 1.622 0.05
315 0.061 0.074 2.062 0.26
v. A 3
Rl a
P2,ln 14.851 ( 4 ) 12.245 (6) 15.848 ( 4 ) 97.32 ( 2 ) 2858 ( 3 ) 1.73
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n
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Figure 1. The molecular structure of 1. There is a crystallographic inversion center at the midpoint of the C(l)=C(l)' bond. Atoms are represented by 40% thermal ellipsoids. Phenyl rings have been omitted for clarity.
sured after every hour of X-ray exposure for each compound. Total losses in intensity for compounds 1 and 2 were 15.4% and 17.6%, respectively. Corrections for anisotropic decay were apa R , = X I P O I - IFcIIXIFoI;R2= [XW(lFgI.- IFCI)'I plied to the data in each case. Largest parameter shiftlesd in final refine~wlF,( Solution a n d Refinement of Structures." Crystals of 1 Quality of fit = [ C W (IFo\ - IFcI )'/ ment cycle. and 2 were found to be monoclinic. The cell volume was consistent (Nobsd - Nparameters)11'2* in each Case with 2 = 2. In each set of data there were systematic absences for h01,h + 1 = 2n + 1, and OkO,k = 2n + 1 that uniquely 24 h, and a fine brown precipitate was formed. Lustrous brown determined the space group as P2,/n. crystalsappropriate for X-ray analysis were obtained after 3 days Metal atom positions for 1 were obtained by direct methods in ca. 5% yield. Crystals of 1were moderately air sensitive (
