Au(I) Complexes Supported by Donor-Functionalized Indene Ligands: Synthesis, Characterization, and Catalytic Behavior in Aldehyde Hydrosilylation

New Au(I) complexes featuring ligands of the type κ 1 -3-R 2 P -indene (κ 1 - 1a, R = i Pr; κ 1 - 1b, R = Ph) and κ 1 -1-R 2 P -2-Me 2 N -indene (κ 1 - 1c, R = i Pr; κ 1 - 1d, R = Ph) were prepared and structurally characterized. Dicoordinate neutral complexes (κ 1 - 1 )AuCl ( 2 − 5 ) were prepared by reacting 1 with Me 2 SAuCl, with isolated yields ranging from 56 to 88%. Addition of a second equivalent of 1a to 2 resulted in formation of the tricoordinate neutral species (κ 1 - 1a ) 2 AuCl ( 6; 69%). By treating 6 with AgOTf, the corresponding cationic complex [(κ 1 - 1a ) 2 Au] + OTf - ([ 7 ] + OTf -; 72%) was obtained. The catalytic performance of these new Au(I) compounds in the hydrosilylation of various aldehydes was compared to that of catalyst systems derived from a combination of R 3 P (R = Et, n Bu, t Bu, Cy, or Ph) or N -heterocyclic carbene ligands and Me 2 SAuCl. While for the phosphine-substituted indene complexes, a catalyst mixture of 3 mol % 2 and 20 mol % 1a was found to be optimal, a catalyst derived from 3 mol % Me 2 SAuCl and 20 mol % Et 3 P, n Bu 3 P, or t Bu 3 P proved to be the most effective overall, especially for reactions conducted at 24 °C. Single-crystal X-ray diffraction data are provided for 2, 4, 6, and [ 7 ] + OTf - .