Chemistry of some dihalogallium(III) β-diketonate derivatives. Crystal and molecular structures of GaCl2(acac), GaCl2(tmhd), and [trans-Ga(acac)2(THF)2+] [GaCl4-]

The dichlorogallium(III) β-diketonato derivatives GaCl2(bdk) [bdk = acac (2,4-pentanedionato) and tmhd (2,2,6,6-tetramethylheptanedionato)] have been prepared and characterized in hydrocarbon solutions by NMR spectral studies and cryoscopic molecular weight measurements and in the solid state by X-ray structural studies. These compounds, which have chelated β-diketonato ligands and four-coordinate gallium, react with THF to form species of composition GaCl2(bdk)·THF. A single-crystal X-ray diffraction study identified GaCl2(acac)·THF as the ion-pair [trans-Ga(acac)2(THF)2+][GaCl4-]. The gallium atom in the cation is six-coordinate, whereas in the anion it is four-coordinate. Variable-temperature 1H NMR spectral studies in CD2Cl2 solution suggest that multiple processes including (i) a stereochemical rearrangement, (ii) THF exchange, and (iii) equilibria between [Ga(bdk)2(THF)2+][GaCl4-], GaCl2(bdk), and at least one other species such as [Ga(bdk)2(THF)+][GaCl4-] are occurring in solution. In contrast, GaX...