Cyclic (Alkyl)(amino)silylene Aluminum(III) Iodide Complex and Its Nucleophile Dependent Reactivities

Exploration of bonding motifs and reactivity modes of molecules that contain an Al–Si core is of particular interest in terms of broadening the application of two of the most abundant elements in the Earth’s crust. Here we report on the synthesis of cyclic (alkyl)(amino)silylene CAASi-ligated aluminum(III) triiodide (AlI₃) complex 1 and investigate its reactivity differences depending on the nucleophile of choice. While the reaction of complex 1 with the anionic nucleophile, Ph₂NLi, selectively results in substitution on Al(III) to afford the CAASi-AlI₂NPh₂ complex (2), treatment of the neutral nucleophiles, N-heterocyclic carbenes (NHCs), results in irreversible ligand exchanges to give the corresponding NHC-AlI₃ complexes. Compound 1, in the presence of 1.0 equiv of CAASi, forms an unusual AlISi₂-heterocyclic compound 6 in the solid state, which was characterized by single crystal XRD analysis. DFT calculations and trapping experiments in solution revealed that 6 exists as a 1:1 equilibrium mixture of 1 and CAASi in solution.