SOME TRANSITION-METAL COMPLEXES OF THE DIACETYLENIC DIPHOSPHINE PH2PC2C2PPH2 - SYNTHESIS AND CRYSTAL-STRUCTURES

Several complexes of the acetylenic ditertiary phosphine, Ph2PC2C2PPh2, containing Mo, W, Fe, Ru or Au have been prepared; one C = C triple bond in the Mo, W or Fe derivatives has been co-ordinated to Co2(CO)6 or Pt(PPh3)2 groups. Crystal structure determinations of [{Fe(CO)4}2(mu-PPh2C2C2PPh2)] 3 and [Co2{mu-eta-2-[(OC)5W(PPh2)]C = C[C2(PPh2)W(CO)5]}(CO)6] 7 show that the P-bonded M(CO)n groups take up transoid positions; in 3, the PCCCCP chain, which is situated about a centre of inversion, is nearly linear [P-C-C, 173.2(5); C-C-C 179.7(6) for molecule a and 174.7(5) and 177.6(6)-degrees, respectively, for molecule b] with C = C distances of 1.192(7) angstrom [1.201(6) angstrom, molecule b]. in 7, co-ordination of the Co2(CO)6 group to one C = C bond lengthens that bond by 0.13 angstrom, compared with the unco-ordinated C = C bond, and induces bend-back of the substituents of 141-143(1)-degrees (PPh2) and 145-146(1)-degrees (C2PPh2) Crystals of 3 are triclinic, space group P1BAR, a = 11.261(1), b = 12.456(2), c = 13.061(2) angstrom, alpha = 79.23(2), beta = 75.73(1), gamma = 78.75(2)-degrees, Z = 2; 2870 data were refined to R = 0.042, R' = 0.046. Crystals of 7 are triclinic, space group P1BAR, a = 17.940(4), b = 19.695(4), c = 16449(2) angstrom, alpha = 111.92(1), beta = 108.83(1), gamma = 100.29(2)-degrees, Z = 4; 5942 data were refined to R = 0.055, R = 0.056.