Preparation of bistrimethylsilylmethylniobiumtetrafluoride and the application of KHF2 and n-Bu4NHF2 as fluorinating reagents

BisTiCl3 (1), BisNbCl4 (2) and BisNbBr4 (3) were prepared by alkylation of NbCl5, NbBr5 and TiCl4 with Bis2Zn (4) (Bis=(SiMe3)2CH). Compounds 2 and 3 were obtained as solids in moderate yields and are sensitive to moisture and air. In addition, the corresponding fluoride derivative of 2, i.e. BisNbF4 (5) was prepared in moderate yield via chlorine–fluorine metathesis employing Me3SnF (6) as a fluorinating reagent. In another attempt Ti(Oi-Pr)4 was reacted with KHF2 to give the fluorine-containing titanium cluster μ3-fluoro-μ3-oxo-tris(μ-isopropoxy)-hexakis(isopropoxy)-tri-titanium (7). The fluorine-free tantalum cluster bis(μ3-oxo)-hexakis(μ-ethoxy)-octakis(μ-oxo)-tetradecakis(ethoxy)-octa-tantalum (8) was obtained from n-Bu4NHF2 and Ta(OEt)5. The identity of all new compounds was documented by analytical/spectroscopic (IR, 1H-, 29Si-, 19F-NMR, MS) data. The crystal structures of 2, 7 and 8 were determined by single crystal X-ray diffraction.