Structural Systematics of Metal Acetylide Complexes. II. X-Ray Studies of Some Nickel σ-Acetylide Complexes

Abstract

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′-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-squares analysis. For (1), crystals are triclinic, space group P^-₁, with a 10·094(2), b13·429(3), c 18·835(5) Å,α 103·24(2), β 91·50(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 Pna2₁, 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 P 2₁/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 P 2₁/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 P 2₁/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 P 2₁/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(1) 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.