Phosphine-Scavenging Role of Gold(I) Complexes from Pd(P^tBu₃)₂ in the Bimetallic Catalysis of Carbostannylation of Alkynes

Density functional theory (DFT) at the M06 level was utilized to compare the reactivity of Pd(P^tBu₃)₂ with that of Pd₂(dba)₃ in catalyzing carbostannylation of alkynes in the presence of [AuL]⁺, where L is a phosphine ligand. In both cases, a common active catalyst is found to be responsible for conducting the reaction. The underlying reason for this is that [AuL]⁺ is capable of acting as a phosphine scavenger and removing both phosphines from Pd(P^tBu₃)₂. The phosphine scavenger property of the cationic gold complexes may find applications in other catalytic coupling reactions. We also found that other Lewis acids such as AuCl, CuCl, and ZnCl₂ might have potential for use as phosphine scavengers from palladium(0) bis(phosphine) complexes.