New PF 3 and Carbonyl Chemistry of Tantalum

Reduction of [TaCl 5 ] by six equivalents of alkali metal naphthalenide in 1,2‐dimethoxyethane at −60°C followed by treatment with gaseous PF 3 provides the first homoleptic phosphane complex containing tantalum in the −1 oxidation state, [Ta(PF 3 ) 6 ] − . This can be protonated by concentrated sulfuric acid to yield the previously unknown highly acidic and volatile hydride [HTa(PF 3 ) 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 [Ph 3 SnTa(CO) 5 ] 2− , respectively. The hydride is a useful precursor to [(Ph 3 PAu) 3 Ta(CO) 5 ], the only known gold cluster of tantalum.