Aryl-NHC-group 13 trimethyl complexes: structural, stability and bonding insights

Treatment of aromatic N-substituted N-heterocyclic carbenes (NHCs) with trimethyl-gallium and -indium yielded the new Lewis acid-base adducts, IMes·GaMe (1), SIMes·GaMe (2), IPr·GaMe (3), SIPr·GaMe (4), IMes·InMe (5), SIMes·InMe (6), IPr·InMe (7), and SIPr·InMe (8), with all complexes being identified by X-ray diffraction, IR, and multinuclear NMR analyses. Complex stability was found to be largely dependent on the nature of the constituent NHC ligands. Percent buried volume (%V ) and topographic steric map analyses were employed to quantify and elucidate the observed trends. Additionally, a detailed bond snapping energy (BSE) decomposition analysis focusing on both steric and orbital interactions of the M-NHC bond (M = Al, Ga and In) has been performed.