N-heterocyclic carbene coordinated gallanes and chlorogallanes

The preparation of the N-heterocyclic carbene coordinated gallium complexes [GaH3(IXy)] (1), [GaH3(IDipp)] (2), [GaClH2(IMes)] (3) and [GaCl2H(IMes)] (4), where IXy = 1,3-bis(2,6-dimethylphenyl)imidazol-2-ylidene, IDipp = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene and IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene, are reported. All four complexes have been characterised by 1H, 13C NMR and IR spectroscopy and, for complexes 2, 3 and 4, single crystal X-ray structure determination. These compounds represent some of the most thermally stable molecular gallium hydrides known, with 4 being the most thermally stable gallium hydride reported (dec. 274 °C). These remarkable thermal stabilities translate to significant aerobic stability such that all four compounds may be handled in dry air without significant decomposition. Compounds 2, 3 and 4 exist as distorted tetrahedra in the solid state with gallium to carbene C-donor bonds that shorten with increasing Lewis acidity of the gallium centre. Compound 2 co-crystallizes with 1 equiv. of 2,6-diisopropylphenylaniline and exhibits several weak intermolecular bonding interactions in the solid-state.

Graphical abstractFour N-heterocyclic carbene coordinated gallanes and chlorogallanes are reported that represent some of the most thermally stable molecular gallium hydrides known. The remarkable thermal stabilities of these complexes translate to aerobic stability.Figure optionsDownload full-size imageDownload as PowerPoint slide