Based on these experimental observations and inferences, we propose a plausible mechanism in Scheme 4. Initially, upon addition of silyl triflate and alkyne into a catalyst mixture containing Ir[(R)-L1]2Cl (I), complex II is generated by halide abstraction and alkyne coordination. Complex II then undergoes electrophilic addition of "R3Si + ", likely through an SN2-type attack of the silyl triflate by the Ir center, to give dicationic Ir(III) species III. Dicationic iridium complexes with similar ligand environments have previously been structurally characterized or invoked as catalytically active intermediates. The enhanced electron deficiency of the dicationic Ir center could then facilitate the turnover-limiting deprotonation of the propargylic proton and afford allenyliridium complex IV, which then undergoes C-Si bond-forming reductive elimination on the Ir center to give the product and regenerate the Ir(I) catalyst as coordinatively unsaturated species V.