Whittall, Ian R.Humphrey, Mark G.Hockless, David C.R.2026-01-012026-01-010004-9425ORCID:/0000-0002-4433-6783/work/162949478https://hdl.handle.net/1885/733799924The 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.We thank the Australian Research Council (A.R.C.) for support. I.R.W. was the recipient of an Australian Postgraduate Research Award (Industry), and M.G.H. holds an A.R.C. Australian Research Fellowship.8en199710.1071/C970490011462011