New PF₃ and Carbonyl Chemistry of Tantalum

AbstractReduction of [TaCl5] by six equivalents of alkali metal naphthalenide in 1,2‐dimethoxyethane at −60°C followed by treatment with gaseous PF3 provides the first homoleptic phosphane complex containing tantalum in the −1 oxidation state, [Ta(PF3)6]−. This can be protonated by concentrated sulfuric acid to yield the previously unknown highly acidic and volatile hydride [HTa(PF3)6]. An improved normal‐pressure synthesis of [Ta(CO)6]− is described. Reduction of the latter species by sodium in liquid ammonia gives the carbonyl trianion [Ta(CO)5]3− which undergoes monoprotonation and stannylation to form [HTa(CO)5]2− and [Ph3SnTa(CO)5]2−, respectively. The hydride is a useful precursor to [(Ph3PAu)3Ta(CO)5], the only known gold cluster of tantalum.