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

IIQ

M.F. Espada, J. Campos, J. López-Serrano, M.L. Poveda, E. Carmona Angew. Chem. Int. Ed. 2015, Vol. 0, doi:10.1002/anie.201508931

Reactions of the gold(I) triflimide complex [Au(NTf₂)(PMe₂Ar)] (1) with the gold(I) hydrocarbyl species [AuR(PMe₂Ar)] (2 a–2 c) enable the isolation of hydrocarbyl-bridged cationic digold complexes with the general composition [Au₂(μ-R)(PMe₂Ar)₂][NTf₂], where Ar=C₆H₃-2,6-(C₆H₃-2,6-iPr₂)₂ and R=Me (3), CHCH₂ (4), or CCH (5). Compound 3 is the first alkyl-bridged digold complex to be reported and features a symmetric [Au(μ-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 sp³ to sp² and sp. Concomitant with this change, and owing to variations in the nature of the bonding within the [Au(μ-R)Au]⁺ unit, there is a gradual decrease in aurophilicity, that is, the strength of the Au⋅⋅⋅Au bonding interaction decreases. This change is illustrated by a monotonic increase in the Au–Au distance by approximately 0.3 Å from R=CH₃ (2.71 Å) to CHCH₂ (3.07 Å) and CCH (3.31 Å).