Pentahapto-bonded gold heteroborane clusters [3-(R3P)-closo-2,1-AuTeB10H10]− and [3-(R3P)-closo-3,1,2-AuAs2B9H9]−

Abstract

Gold acetylide compounds [(R₃P)AuCCC(Me)(OH)Et], where R = Ph 1 or cyclohexyl (Cy) 2, were synthesised and 2 was characterised using X-ray diffraction techniques. The solid-state structure of 2 contained a two-coordinate gold atom and a linear P–Au–CC–C bonding sequence. The reactions between 1 or 2 and [NR₄][nido-7,8-As₂B₉H₁₀] or [NR₄][nido-7-TeB₁₀H₁₀] in ethanol–acetone solvent afforded the twelve-vertex cluster species [NMe₄][3-(R₃P)-closo-3,1,2-AuAs₂B₉H₉], where R = Ph 5 or Cy 6, or [NEt₄][3-(R₃P)-closo-2,1-AuTeB₁₀H₁₀], where R = Ph 7 or Cy 8, in moderate or low yields (ca. 35% for 5, 6 and 8 and ca. 20% for 7). Compounds 5 and 7 were characterised with X-ray crystallographic techniques. Although there was crystallographic disorder in the {As₂B₃} and {TeB₄} rings to which the gold atoms were attached, the structures of 5 and 7 strongly suggested that the gold atoms were pentahapto bonded to all the atoms in the {As₂B₃} or {TeB₄} rings giving formally closo cluster geometries with closo cluster electron counts. The solution-phase NMR properties of 5, 6 and 7 were consistent with closo descriptions.