Tantalum-mediated substitution at germanium:: A germolyl-to-germole transformation leading to η4-C4Me4GeMeCl complexes

The germole reagent C4Me4GeMeSiMe3 (1), synthesized via reaction of K[C4Me4GeSiMe3] with Mel, reacted with TaCl5 to give [(eta (4)-C4Me4GeMeCl)TaCl3(Et2O)(x)](2) (2;x = 0.5-1.0) with loss of Me3SiCl. Complex 2 reacted with various two-electron donors to give stable adducts (eta (4)-C4Me4GeMeCl)TaCl3L (3, L = PPh3; 4, L = CNXyl; Xyl = 2,6-dimethylphenyl) and (eta (4)-C4Me4GeMeCl)TaCl3L (5, L = CNXyl; 6, L = pyridine). The X-ray structure of(eta (4)-C4Me4GeMeCl)TaCl3(CNXyl)(2) (5) confirmed eta (4)-coordination of the germole unit and the exo orientation of the Ge-Cl bond. Complex 2 also reacted with CpTl to give air-stable Cp(eta (C4Me4GeMeCl)-C-4)TaCl2 (7), which was also characterized by X-ray crystallography. Attempts to generate eta (5)-germolyl tantalum complexes are described.