NEW PF3 AND CARBONYL CHEMISTRY OF TANTALUM

Reduction of [TaCl5] by six equivalents of alkali metal naphthalenide in 1,2-dimethoxyethane at -60 degrees C followed by treatment with gas eous PF3 provides the first homoleptic phosphane complex containing ta ntalum in the -1 oxidation state, [Ta(PF3)(6)](-). This can be protona ted by concentrated sulfuric acid to yield the previously unknown high ly acidic and volatile hydride [HTa(PF3)(6)]. An improved normal-press ure 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 [HT a-(CO)(5)](2-) and [Ph(3)SnTa(CO)(5)](2-), respectively. The hydride i s a useful precursor to [(Ph(3)PAu)(3)Ta(CO)(5)], the only known gold cluster of tantalum.