Preparation of monomethyl-niobium(V) and -tantalum(V) halides and of some of their complexes
Abstract
Monoalkylated compounds MeNbCl4, MeTaCl4, and MeNbBr4 have been synthesized by treating the corresponding metal(V) halides with either HgMe2 or SnMe4. With the chlorides the reactions were rapid and simple: only the monoalkyl derivatives were formed and isolated in quantitative yields, along with either HgCl2 or ClSnMe3. No further substitution was observed in the presence of an excess of either of the alkylating agents. The reaction of HgMe2 with NbBr5 was much slower and MeHgBr was formed. The reaction of SnMe4 with NbBr5 does not go to completion. The new compounds have been characterized by elemental analysis, cryoscopic molecular-weight determinations, n.m.r. and i.r. spectroscopy, mass spectrometry, and by the identification of a range of adducts, several of which were isolated, i.e.[MeNbCl4],L (L = PPh3, Ph2PCH2CH2PPh2, or γ-picoline) and [MeNbBr4], L (L = Ph2PCH2CH2PPh2 or 2,2′-bipyridine).