Methyl-, Ethenyl-, and Ethynyl-Bridged Cationic Digold Complexes Stabilized by Coordination to a Bulky Terphenylphosphine Ligand

Reactions of the gold(I) triflimide complex [Au(NTf2)(PMe2ArDipp2)] (1) with the gold(I) hydrocarbyl species [AuR(PMe2ArDipp2)] (2a-2c) enable the isolation of hydrocarbyl-bridged cationic digold complexes with the general composition [Au-2(mu-R)(PMe2ArDipp2)(2)][NTf2], where Ar-Dipp2 = C6H3-2,6-(C6H3-2,6-iPr(2))(2) and R= Me (3), CH=CH2 (4), or C CH (5). Compound 3 is the first alkyl-bridged digold complex to be reported and features a symmetric [Au(mu-CH3)Au](+) core. Complexes 4 and 5 are the first species of their kind that contain simple, unsubstituted vinyl and acetylide units, respectively. In the series of complexes 3-5, the bridging carbon atom systematically changes its hybridization from sp(3) to sp(2) and sp. Concomitant with this change, and owing to variations in the nature of the bonding within the [Au(mu-R)Au](+) unit, there is a gradual decrease in aurophilicity, that is, the strength of the Au center dot center dot center dot Au bonding interaction decreases. This change is illustrated by a monotonic increase in the Au-Au distance by approximately 0.3 angstrom from R=CH3 (2.71 angstrom) to CH=CH2 (3.07 angstrom) and C CH (3.31 angstrom).