Study of the Coordination Abilities of Stibine Ligands to Gold(I)

Abstract

The reaction of [AuCl(tht)] (tht = tetrahydrothiophene) with SbMes(n)Ph(3-n) (n = 3 (1), 2 (2), 1 (3)) produces the 1:1 adducts [AuCl(SbMes(n)Ph(3-n))] (n = 3 (4), 2 (5), 1 (6)), with a Sb-Au-Cl environment, regardless of the molar ratio used (1:1 to 1:4). Addition of the same stibines to [Au(tht)(2)]ClO(4) (molar ratio 1:1 to 1:4) results in isolation of the 1:2 adducts [Au(SbMes(n)Ph(3-n))(2)]ClO(4) (n = 3 (7), 2 (10)), containing linear Sb-Au-Sb fragments, or the 1:3 adduct [Au(SbMesPh(2))(3)]ClO(4) (11), with a quasi trigonal planar AuSb(3) core. The same 1:2 cations are produced when [Au(tht)(2)]CF(3)SO(3) is reacted with 1 or following a rearrangement process when 4 is treated with AgSbF(6), that is, [Au(SbMes(3))(2)]X (X = CF(3)SO(3) (8), SbF(6) (9)). The compounds were characterized by spectroscopic methods, and the molecular structures of 2-4, 7, 8.2CDCl(3), 9, and 11 were established by single-crystal X-ray diffraction. Theoretical calculations were carried out on model systems of type ER(3) and [Au(ER(3))(n)](+) (E = P or Sb; R = Ph or Mes; n = 2, 3, or 4) to gain insight into the bonding nature of SbR(3) ligands in homoleptic gold-stibine adducts, in comparison with phosphine-gold(I) compounds. Steric effects govern the coordination of stibines with mesityl substituents. A preference for higher coordination numbers is observed for SbPh(3) when compared with PPh(3) and experimentally observed C-Sb-C and Sb-C structural distortions of stibines upon coordination are reproduced theoretically.