Maleate-fumarate conversion and other novel aspects of the reaction of a Co(II) maleate with pyridine and bipyridine.

Reaction of a molecular Co(II) maleate, [Co(Hmal)2(H2O)4], with pyridine yields a Co(II) fumarate, [Co(fum)(H2O)4], with a chain structure and a chiral pyridylsuccinic acid zwitter ion, −OOC–CH(N+C5H5)–CH2–COOH, in almost quantitative yields, while the reaction of 4,4′-bipyridine (bipy) with the Co(II) maleate, on the other hand, almost quantitatively generates a polylmeric Co(II) maleate, [Co(mal)(bipy)]n·(n/2)H2O along with the adduct of fumaric acid with bipyridine.