Structural Systematics of Metal Acetylide Complexes: X-Ray Studies of Some 'Extended-Chain' Gold σ-Acetylide Complexes

Abstract

The structures of Au(4-C≡CC6H4XYC6H 4-4′NO2)(PPh3) (XY = (E)-CH=CH (1), (Z)-CH=CH (2), C≡C (3), N=CH (4)) have been determined by single-crystal X-ray diffraction analyses, refining by full-matrix least-squares analysis. For (1), crystals are triclinic, space group P1̄, with a 8.847(1), b 17.870(4), c 19.705(3) Å, α 116.25(1), β93.33(1), γ 92.64(2)°, Z 4, 6747 unique reflections (703 parameters), converging at R 0.025 and Rw 0.029. For (2), crystals are monoclinic, space group P2 1/a, with a 10.718(6), b 19.398(5), c 14.469(3) Å, β 108.96(2)°, Z 4, 3295 unique reflections (352 parameters), converging at R 0.040 and Rw 0.034. For (3), crystals are triclinic, space group P1̄, with a 10.671(4), b 17.599(7), c 18.220(8) Å, α 116-31(3), β105.00(4), γ 95.08(4)°, Z 4, 4828 unique reflections (703 parameters), converging at R 0.043 and Rw 0.030. For (4), crystals are triclinic, space group P1̄, with a 8.8314(6), b 17.834(2), c 20.001(2) Å, α 115.249(7), β 90.930(7), γ 94.082(7)°, Z 4, 4724 unique reflections (703 parameters), converging at R 0.035 and Rw 0.034. Despite the [ligated metal donor]-bridge-[nitro acceptor] composition of these complexes, Au-C and C≡C distances are normal and consistent with minimal allenylidene contribution to the ground-state geometry. Within the 3σ confidence limits, the structural data do not provide evidence for π*-back-bonding in these complexes.