Structural, far-infrared and 31P nuclear magnetic resonance studies of two-co-ordinate complexes of tris(2,4,6-trimethoxyphenyl)phosphine with gold(I) halides

Abstract

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)Å and 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)Å(iodide). The complexes [AuX(tmpp)] were characterized by far-IR spectroscopy [ν(Au–X) 313, 218, 183 cm^–1.; X = Cl, Br, I] and by ³¹P NMR spectroscopy in acetonitrile [δ(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]⁺[δ(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.