STRUCTURAL SYSTEMATICS OF METAL ACETYLIDE COMPLEXES - II - X-RAY STUDIES OF SOME NICKEL SIGMA-ACETYLIDE COMPLEXES

The structures of Ni(C=CR)(PPh3) (eta-C5H5) (R = Ph (1) C6H4-4-NO2 (2) , 4-C6H4C6H4-4'-NO2 (3), (E)-4-C6H4CH=CHC6H4-4'-NO2 (4), 4-C6H4C=CC6H4 -4'-NO2 (5), 4-C6H4N=CHC6H4-4'-NO2 (6)) have been determined by single -crystal X-ray diffraction studies, refining by full-matrix least-squa res analysis. For (1), crystals are triclinic, spate group P (1) over bar, with a 10.094(2), b 13.429(3), c 18.835(5) Angstrom, alpha 103.24 (2), beta 91.50(2), gamma 90.10(2)degrees, Z 4, 5844 unique reflection s (595 parameters), converging at R 0.033 and R-w 0.024. For (2), crys tals are orthorhombic, space group Pna2(1): with a 16.799(2), b 8.681( 2), c 17.485(2) Angstrom, Z 4, 1774 unique reflections (325 parameters ), converging at R 0.031 and R-w 0.029. For (3), crystals are monoclin ic, space group P2(1)/c, with a 11.140(3), b 18.282(4), c 15.296(2) An gstrom, beta 105.18(2)degrees, Z 4, 3132 unique reflections (397 param eters), converging at R 0.039 and R-w 0.024. For (4), crystals are mon oclinic, space group P2(1)/n, with a 12.929(7), b 16.953(8), c 15.601( 7) Angstrom: beta 112.55(3)degrees, Z 4, 3023 unique reflections (397 parameters), converging at R 0.039 and R-w 0.025. For (5), crystals ar e monoclinic, space group P2(1)/n, with a 12.710(5), b 16.882(3): c 15 .693(4) Angstrom, beta 111.37(3)degrees, Z 4, 3216 unique reflections (397 parameters), converging at R 0.035 and R-w 0.030. For (6), crysta ls are monoclinic, space group P2(1)/n, with a 12.594(1), b 16.936(2), c 15.611(1) Angstrom, beta 112.476(5)degrees, Z 4, 3564 unique reflec tions (397 parameters), converging at R 0.038 and R-w 0.041. For struc turally characterized 18-electron (cyclopentadienyl) nickel(II) acetyl ide complexes, statistically insignificant decreases in the average Ni -C(1) distance and trains influence and an increase in the average C(1 )-C(2) parameter are observed on introduction of an acceptor substitue nt at the alkynyl ligand.