Dialkylgallium Complexes with Alkoxide and Aryloxide Ligands Possessing N‑Heterocyclic Carbene Functionalities: Synthesis and Structure

Methods for the synthesis
of dialkylgalium compounds with alkoxide
or aryloxide ligands possessing N-heterocyclic carbene functionalities
have been established. As a result, the synthesis of a series of dialkylgallium
complexes Me2Ga­(O,C) (1, 3–5), and Me2Ga­(O,C)·Me3Ga (2, 6) is described, where (O,C) represents an
alkoxide or aryloxide monoanionic chelate ligand with an N-heterocyclic
carbene functionality. All complexes have been fully characterized
using spectroscopic and X-ray techniques. The presence of a strongly
basic NHC functionality in alkoxide or aryloxide ligands resulted
in the formation of monomeric Me2Ga­(O,C) species. The reaction
of those complexes with the Lewis acid Me3Ga leads to Me2Ga­(O,C)·Me3Ga adducts (2 and 6) with a strong Me3Ga–O dative bond. The
effect of (O,C) ligands with various steric and electronic properties
on the structure of obtained Me2Ga­(O,C) and Me2Ga­(O,C)·Me3Ga has been discussed on the basis of
spectroscopic data. Finally, the bond valence vector model has been
used to estimate the effect of a chelating (O,C) ligand on strains
in complexes 1–6 on the basis of
X-ray data.