Synthesis and catalytic activity of manganese(II) complexes of heterocyclic carboxylic acids:: X-ray crystal structures of [Mn(pyr)2]n, [Mn(dipic)(bipy)2]•4.5H2O and [Mn(chedam)(bipy)]•H2O(pyr = 2-pyrazinecarboxylic acid; dipic = pyridine-2,6-dicarboxylic acid; chedam = chelidamic acid(4-hydroxypyridine-2,6-dicarboxylic acid); bipy = 2,2-bipyridine)

Reactions of manganese(II) acetate with 2-pyrazine carboxylic acid, 2,6-pyridinedicarboxylic acid and chelidamic acid (4-hydroxypyridine-2,6-dicarboxylic acid) yielded [Mn(pyr)(2)](n) (1), [Mn(dipic)](.)1.5H(2)O (2) and [Mn(chedam)](H2O)-H-. (6), respectively. Reaction of 2 with 2,2'-bipyridine and 1,10-phenanthroline results in the synthesis of [Mn(dipic)(bipy)](.)2H(2)O (3), [Mn(dipic)(bipy)(2)](.)4.5H(2)O (4) and [Mn(dipic)(phen)(2)](.)2H(2)O (5). Complex 6 reacted with 2,2'-bipyridine and 1,10-phenanthroline to give [Mn(chedam)(bipy)](H2O)-H-. (7) and [Mn(chedam)(phen)(2)](.)3H(2)O (8), respectively. Molecular structures for 1, 4 and 7 were determined by X-ray crystallography. In 1 the structure is essentially polymeric with each pyrazine carboxylate anion coordinated to the manganese ion in a bidentate fashion using one carboxylate oxygen atom and the adjacent nitrogen. The second nitrogen is uncoordinated. For 4 the asymmetric unit consists of one tridentate dipicolinate ligand, two bidentate bipyridine molecules, four full-occupancy water molecules and one half-occupancy water molecule. The structure of 7 contains monomeric [Mn(dicarboxylate)(bipy)H2O] units in which the Mn(II) ions have very irregular six-coordinate geometry. Spectroscopic, magnetic and physical data for the complexes are presented. All of the manganese complexes catalytically disproportionate hydrogen peroxide in the presence of imidazole. (C) 2002 Published by Elsevier Science Ltd.