Entrapment of THF-Stabilized Iridacyclic IrIII Silylenes from Double H-Si Bond Activation and H2 Elimination.

The reaction of H3 SiR (R=Ph, nBu) with cationic η5 -C5 Me5 - (Cp*) and benzo[h]quinolinyl-based iridacycle [1 b]+ gives rise to new [(IrH)→SiRH2 ]+ adducts. In the presence of THF these adducts readily undergo elimination of H2 gas at subambient temperature to form THF-stabilized metallacyclic IrIII silylene complexes, which were characterized in situ by NMR spectroscopy, trapped in minute amounts by reactive crystallization, and structurally characterized by XRD. Theoretical investigations (static DFT-D reaction-energy profiling, ETS-NOCV) support the promoting role of THF in the H2 elimination step and the consolidation of the Ir-to-Si interaction in the spontaneous (ΔG<0) formation of Ir silylenes in the presence of THF. Mechanistic insights indicate that the Ir silylene species arising from the [1 b]+ /phenylsilane system are relevant catalytic species in the hydrodefluorination of fluoroalkanes.