Diorganogallium β-Diketonates and Their Lewis Acid−Base Adducts. Crystal and Molecular Structures of Mes2Ga(hfac) and Me2Ga(hfac)·NC5H5

Abstract

Compounds of the type R2Ga(bdk) (R = Me, Et, Mes (mesityl); bdk = 2,4-pentanedionato (acac), 1,1,1-trifluoro-2,4-pentanedionato (tfac), 1,1,1,5,5,5-hexafluoro-2,4-penatedionato (hfac), 2,2,6,6-tetramethyl-3,5-heptanedionato (tmhd)) have been prepared by multiple routes, including hydrocarbon elimination, metathesis, and ligand redistribution reactions, and fully characterized by elemental analyses, cryoscopic molecular weight studies in benzene, and IR and multinuclear NMR spectroscopic studies. An X-ray structural study of Mes2Ga(hfac) demonstrated four-coordinate gallium with σ bonds to the two mesityl rings and to the two oxygen atoms of the β-diketonate ligand. The Lewis acidities of the diorganogallium β-diketonate derivatives toward NMe3 and/or pyridine were also investigated. Two adducts, Me2Ga(hfac)·NMe and Me2Ga(hfac)·py, were stable to dissociation at room temperature and thus were fully characterized by elemental analysis, cryoscopic molecular weight studies in benzene, vapor pressure−temperature studies, and IR and multinuclear NMR (including variable temperature) spectroscopic studies. The compound Me2Ga(hfac)·py was also characterized by an X-ray structural study. The structure involved five-coordinate gallium with one Ga−N, two (inequivalent) Ga−O, and two Ga−C bonds.