Preparation, structure and decomposition of gold(I) and gold(III) acetylide complexes

Abstract

1-Alkynyl-dimethyl(triorganophosphine)gold(III) complexes of the type cis-Me 2(Ph 3P)Au–C C–R with R = H, Me, Ph ( 1– 3) have been prepared from the cis-Me 2(Ph 3P)AuX (X = Cl, I) complexes and lithium alkynyls. The crystal structures of 1 and 2 have been determined together with those of the reference compounds cis-Me 2(Ph 3P)AuX (X = Cl, I) and cis-Me 2(Me 3P)AuI. The molecules have a standard square planar geometry and are not associated into oligomers. Due to the different hybridization of the carbon orbitals, the Au–C( CR) bonds are found significantly shorter than the Au–CH 3 bonds. Compounds 1– 3 are stable colourless, crystalline solids at 20 °C but decompose on heating with selective ( cis) reductive elimination of ethane and formation of the gold(I) alkynyls (Ph 3P)Au–C C–R thus retaining the stronger gold-alkynyl bonds. Two complexes of this type have also been prepared by conventional routes from (R 3P)AuX complexes and the crystal structures of (Me 3P)Au–C C–Ph and [( p-Tol) 3P]Au–C C–H have been determined. The former with the small Me 3P ligand is associated into two different trimers via aurophilic bonding and further aggregated into chains via weak inter-trimer contacts, while the latter is a monomer owing to the steric bulk of the ( p-Tol) 3P ligand.