SYNTHESIS, X-RAY CRYSTAL-STRUCTURE AND CATALYTIC ACTIVITY OF THE MANGANESE(II) E-UROCANIC ACID (E-UROH) COMPLEX [MN(E-URO)(2)(H2O)(4)]

Manganese(II) chloride tetrahydrate reacted with the sodium salt of E- urocanic acid (E-uroH) in aqueous media giving the manganese(II) compl ex [Mn(E-uro)(2)(H2O)(4)] in high yield. The X-ray crystal structure o f the complex shows two distinct isomers of [Mn(E-uro)(2)(H2O)(4)]. On e isomer has the amine nitrogen atom of the imidazole ring lying in a cisoid orientation with respect to the carbon-carbon double bond which bears the pendant carboxylate group, whilst in the other isomer the s ame nitrogen atom is transoid to the double bond. Both species are cen trosymmetric, so that the asymmetric unit comprises two independent ha lf molecules. The geometry at manganese is approximately octahedral, w ith the metal coordinated by the imine nitrogen atoms from two urocana te anions trans td one another and also by four water molecules. Spect roscopic, magnetic and electrochemical data for the complex are given, together with its catalytic activity towards the disproportionation o f H2O2. Copyright (C) 1996 Elsevier Science Ltd.