The complexes [AuX(tmpp)][X = Cl, Br or I; tmpp = tris(2,4,6-trimethoxyphenyl)phosphine] were prepared by reaction of tmpp with [AuX(Me2S)] or [AuX2]-. The crystalline compounds are isomorphous with the corresponding complexes of Cu and Ag, with Au-P 2.253(5), 2.255(4), 2.239(7), Au-X 2.303(6), 2.413(2), 2.586(2)Šand P-Au-X 176.0(2), 175.9(1), 177.7(2)஠The Au O contacts involving the nearest o-methoxy oxygen atoms on the three phenyl groups in the ligand are: 3.15(1), 3.08(1), 2.92(2)(chloride); 3.13(2), 3.11(1), 2.96(1)(bromide); 3.01(2), 3.10(1), 3.09(2)Ũiodide). The complexes [AuX(tmpp)] were characterized by far-IR spectroscopy [(Au-X) 313, 218, 183 cm-1.; X = Cl, Br, I] and by 31P NMR spectroscopy in acetonitrile [(31P)-35.9, -31.8, -23.9]. All members of the series [MX(tmpp)](M = Cu, Ag or Au; X = Cl, Br or I) are now known (although the Agl complex has so far only been detected in solution). The M-X bond properties in this series show trends which reveal the presence of relativistic effects in the M = Au case. Reaction of [AuX(tmpp)] with tmpp in a 1 : 1 mole ratio in solution results in displacement of X- to yield [Au(tmpp)2]+[(31P)-24.9]. Unlike the corresponding PPh3complexes, [AuX(tmpp)] show no evidence of 1J(197Au31P) spin-spin splitting in their solid-state 31P cross polarization magic angle spinning NMR spectra. A simple one-pot synthesis of the known gold(I) complex [NBu4][Aul2] from metallic gold was achieved.