Novel ring compounds of bidentate phosphines with gold(I). Two-, three-, and four-co-ordination

Abstract

With n-butyldiphenylphosphine and gold(I), salts [AuBr(PPh₂Buⁿ)_x]⁺(x= 1 or 2) and [Au(PPh₂Buⁿ)_x]⁺(x= 2,3, or 4) are formed in solution and in the solid state. A range of short-chain and long-chain diphosphines (L), Ph₂P(CH₂)_n,PPh₂(n= 1,2,4,6,8,10, or 12) have been employed to prepare the neutral complexes, [(AuBr)₂L_x](x= 1 or 2), in which the gold is two-, and three-co-ordinate, respectively, and the cationic compounds [Au₂L_x][ClO₄]₂(x= 2, 3, or 4) in which the gold is two-, three-, and four-co-ordinate. However, it was only possible to isolate the novel [Au₂L₄][ClO₄]₂ complexes with the short-chain diphosphines, Ph₂P(CH₂)_nPPh₂(n= 2,3, or 4). A ³¹ P-{¹H} n.m.r. study employing Ph₂P(CH₂)₆PPh₂ and Au Br₂^– at different ratios in CD₂Cl₂, shows the presence of two-, three-, and four-co-ordinate gold, and these species exchange with one another at temperatures > –50 °C. A similar study at –90 °C with the other diphosphines gave similar results, except that three- and four-co-ordination exist in the case of the short-chain ligands Ph₂P(CH₂)_nPPh₂(n= 1 or 2) even at very low ligand: gold ratios.