2,2′-Bipyridyl complexes of the niobium(V) and tantalum(V) halides
Methyl cyanide solutions of the pentahalides NbCl5, TaCl5, and TaBr5 react with 2,2′-bipyridyl (bipy) at ca. 0° to yield compounds of general formula MX5 bipy (MeCN). These are believed to be seven-co-ordinate and to contain a molecule of ‘lattice’ methyl cyanide. Under similar reactions conditions niobium(V) bromide and tantalum(V) iodide react to give MX5bipy2; no pure product was isolated from the related reaction involving niobium(V) iodide. At room temperature direct reaction of niobium(V) and tantalum(V) iodide with methyl cyanide leads to the formation of 1 : 1 adducts Ml5,MeCN. Compounds were characterised by their electronic and vibrational (i.r. and Raman) spectra.