Structural systematics of metal acetylide complexes. II - X-ray studies of some nickel σ-acetylide complexes

The structures of Ni(C≡CR) (PPh₃)(η-C₅H₅) (R = Ph (1), C₆H₄-4-NO₂ (2), 4-C₆H₄C₆H₄-4′-NO₂ (3), (E)-4-C₆H₄CH=CHC₆H₄-4′-N0 ₂ (4), 4-C₆H₄C≡CC₆H₄-4′-NO ₂ (5), 4-C₆H₄N=CHC₆H₄-4′-NO ₂ (6)) have been determined by single-crystal X-ray diffraction studies, refining by full-matrix least-squares analysis. For (1), crystals are triclinic, space group P1, with a 10-094(2), b 13.429(3), c 18-835(5) Å, α 103-24(2), β91-50(2), γ 90-10(2)°, Z 4, 5844 unique reflections (595 parameters), converging at R 0.033 and R_w 0.024. For (2), crystals are orthorhombic, space group P na2₁, with a 16-799(2), b 8-681(2), c 17.485(2) Å, Z 4, 1774 unique reflections (325 parameters), converging at R 0.031 and R_w 0.029. For (3), crystals are monoclinic, space group P2₁/c, with a 11.140(3), b 18.282(4), c 15.296(2) Å, β 105-18(2)°, Z 4, 3132 unique reflections (397 parameters), converging at R 0.039 and R_w 0.024. For (4), crystals are monoclinic, space group P2₁/n, with a 12.929(7), b 16.953(8), c 15.601(7) Å, β 112.55(3)°, Z 4, 3023 unique reflections (397 parameters), converging at R 0.039 and R_w 0.025. For (5), crystals are monoclinic, space group P2₁/n, with a 12.710(5), b 16.882(3), c 15.693(4) Å, β 111.37(3)°, Z 4, 3216 unique reflections (397 parameters), converging at R 0.035 and R_w 0.030. For (6), crystals are monoclinic, space group P2₁/n, with a 12.594(1), b 16.936(2), c 15.611(1) Å, β 112.476(5)°, Z 4, 3564 unique reflections (397 parameters), converging at R 0.038 and R_w 0.041. For structurally characterized 18-electron (cyclopentadienyl)nickel(II) acetylide complexes, statistically insignificant decreases in the average Ni-C(l) distance and trans influence and an increase in the average C(1)-C(2) parameter are observed on introduction of an acceptor substituent at the alkynyl ligand.