An unusual anionic oxo–(µ-oxo)–vanadium(V) network interlinked by cationic sodium chains

Abstract

The new compound 6-(1-cyano-2-hydroxyprop-1-enyl)pyridine-2-carboxylic acid (H₂L) has been prepared and the structure of its ethyl ester determined. The salt NaHL reacted with VO²⁺ to form the vanadium(V) complex [Na(MeOH)₂][VO₂L]. Crystal-structure analysis of the complex revealed octahedral co-ordination of both the sodium and vanadium ions. Vanadium is co-ordinated to enolate oxygen, carboxylate oxygen, pyridine nitrogen, and two doubly bonded oxo groups in cis positions. The sixth position is occupied by the oxo group of a neighbouring vanadium centre at a rather long distance of 2.214(2)Å. Anionic, asymmetrically oxo-bridged vanadium chains are thus formed. These are interlinked by cationic sodium chains with sodium bonded to two bridging methanols, the cyano nitrogen of one of the vanadate chains and the co-ordinated carboxylate of the alternate vanadate chain. The network is further stabilized by hydrogen bonds. The relevance of the complex to biogenic vanadium compounds is discussed.