Formation of Gallium Monofluoride in the Coordination Sphere of Nickel

Monovalent gallium halides are intrinsically unstable compounds at room temperature and can only be generated in the gas phase at temperatures of about 1000 °C. Although they are isoelectronic to carbon monoxide, dinitrogen, and the cyanide ion, which are pivotal ligands in coordination chemistry, monovalent gallium halides are largely unexplored as ligands with transition metals. Herein, we report the isolation of a dicationic nickel complex bearing a gallium monofluoride ligand. The +I oxidation state of the gallium centre is supported by NMR-spectroscopic methods, X-ray photoelectron spectroscopy, as well as density functional theory calculations. Analysis of the bonding situation between the GaF ligand and the central nickel atom suggests strong σ-donating, but negligible π-accepting properties for the supported GaF fragment. The GaF moiety forms as a product of C(sp³)-F bond activation of the weakly coordinating BAr^F24 (tetrakis[(bis-3,5-trifluoromethyl)phenyl]borate) anion and serves as a fluorine source for silicon and carbon electrophiles. This leads to facile defluorination, forming the fluoride-free complex and fluorinated products such as fluorotrimethylsilane or benzoyl fluoride.