Auriophilicity in Polynuclear (Phosphane)gold(I) Thiolates {Me 3 CS[Au(PPh 3 )] 2 } + BF ‐ 4 and {(CH 2 S) 2 [Au(PPh 3 )] 3 } + BF ‐ 4

Abstract

The reaction of tert-butanethiol with tris[(triphenylphosphane)gold(I)]oxonium tetrafluoroborate in dichloromethane in the presence of sodium tetrafluoroborate gave quantitative yields of a product {Me3CS[Au(PPh3)]2}+ BF-4 (1). In the crystal lattice of this salt, the sulfonium cations are associated into dimers through close Au…Au contacts. The centrosym-metrical tetranuclear unit has Au…Au distances of 3.292(1) and 3.206(1) A, and the Au-S-Au angles are exactly 90.0(1)°. Both data are indicative of significant intra- and intercationic Au…Au attractions. The analogous reaction of ethane-1, 2–dithiol afforded high yields of a product {(CH2S)2[Au(PPh3)]3}+ BF-4 (2). The compound is fluxional in CD2Cl2 solution and shows only one 31P-NMR signal at -60°C. In the crystal, the quasi C2-symmetrical trinuclear cations feature the sulfur atoms in bridging positions between two gold atoms. The central gold atom is thus three-coordinate; the peripheral gold atoms are two-coordinate with Au…Au contacts at 3.284(1) and 3.129(1) A and Au-S-Au angles as small as 86.5(1) and 81.0(1)°. This provides clear evidence for “auriophilic” bonding.