Synthesis, Isolation, and Reactivity of an Aluminum Triiodide Supported by an NHC/cAAC-Based Carbodicarbene Ligand

Along the research journey towards novel low-valent aluminum compounds, bulky σ-donor ligand adducts of aluminum(III) halides are prevalent synthons. These ligands’ steric and electronic properties contribute to stabilizing the highly reactive aluminum center. Herein, we addressed the coordination ability of two carbodicarbene (CDC) ligands to Al(III) center to extend the scope of the σ-donor ligands from the conventionally adopted N-heterocyclic carbene (NHC) and cyclic(alkyl)(amino)carbene (cAAC). An unsymmetrical NHC/cAAC-based CDC ligand-coordinated AlI₃ adduct ^NHC/cAACCDC → AlI₃ (1, NHC = 1,3-dimethyl-2,3-dihydro-1H-benzoimidazole 2-ylidene, cAAC = 1,3,3-trimethylindoline 2-ylidene) was isolated and characterized, while the reaction of AlI₃ with a cAAC-only based CDC resulted in the formation of the ionic product 2.