Portal de Periódicos da CAPES

The Course of (R 2 R‘SiO) 3 TaCl 2 (R = t Bu, R‘ = H, Me, Ph, t Bu (silox); R = i Pr, R‘ = t Bu, i Pr) Reduction Is Dependent on Siloxide Size

2004; American Chemical Society; Volume: 43; Issue: 11 Linguagem: Inglês

10.1021/ic035407u

1520-510X

A.R. Chadeayne, Peter T. Wolczanski, Emil B. Lobkovsky,

Corrosion Behavior and Inhibition

Various sized siloxides (Cy(3)SiO > (t)Bu(3)SiO > (t)Bu(2)PhSiO > (t)Bu(2)MeSiO approximately (i)Pr(2)(t)BuSiO > (i)Pr(3)SiO > (t)Bu(2)HSiO) were used to make (R(2)R'SiO)(3)TaCl(2) (R = (t)Bu, R' = H (1-H), Me (1-Me), Ph (1-Ph), (t)Bu (1); R = (i)Pr, R' = (t)Bu (1-(i)Pr(2)); R = R' = (i)Pr (1-(i)Pr(3)); R = R' = (c)Hex (Cy)). Product analyses of sodium amalgam reductions of several dichlorides suggest that [(R(2)R'SiO)(3)Ta](2)(mu-Cl)(2) may be a common intermediate. When the siloxide is large (1-(t)Bu), formation of the Ta(III) species ((t)Bu(3)SiO)(3)Ta (6) occurs via disproportionation. When the siloxide is small, the Ta(IV) intermediate is stable (e.g., [((i)Pr(3)SiO)(3)Ta](2)(mu-Cl)(2) (2)), and when intermediate sized siloxides are used, solvent bond activation via unstable Ta(III) tris-siloxides is proposed to occur. Under hydrogen, reductions of 1-Me and 1-Ph provide Ta(IV) and Ta(V) hydrides [((t)Bu(2)MeSiO)(3)Ta](2)(micro-H)(2) (4-Me) and ((t)Bu(2)PhSiO)(3)TaH(2) (7-Ph), respectively.