Complexes of niobium(V) and tantalum(V) halides with dinitriles—II: Glutaronitrile and adiponitrile

Abstract

Complexes of niobium(V) and tantalum(V) chlorides and bromides with glutaronitrile and adiponitrile have been synthesized and characterized. Two types of complexes having stoichiometry MX 5 . L(1:1) and 2 MX 5 . L(2:1) [ M = Nb, Ta; X = Cl, Br; L = dinitrile] have been isolated in the case of glutaronitrile, whereas only 2 MX 5 . L type is formed with adiponitrile. Conductivity measurements in acetonitrile have shown that they are virtually non-ionic in this solvent. Spectrophotometric studies in the i.r. region (4000−650 cm −1) have been carried out to determine the coordination site and the possible rotational isomers of the ligand molecules in these complexes. A positive shift in the ν(CN) on complexation suggests bonding of the cyano group through the lone pair of electrons. The i.r. results also indicate that glutaronitrile assumes TG conformation in the 1:1 adducts and TT form in the 2:1 adducts. Adiponitrile, which forms only the 2:1 adducts assumes GTG′ conformation.