BINUCLEAR CHROMIUM(III), MANGANESE(III), IRON(III) AND COBALT(III) COMPLEXES BRIDGED BY DIAMINOPYRIDINE

Trivalent chromium, manganese, iron and bivalent cobalt salts react wi th 2,6-diaminopyridine and acetylacetone to give complexes of the type [M(C15H17N3O2)X] [where X = Cl, Br, NO3 or NCS for M = chromium(III) and iron(III); X = Cl, Br, OAc or NCS for manganese(III)]. Conductance measurements show the complexes to be nonelectrolytes. Molecular weig hts determined cryoscopically suggest the dimeric nature of these comp lexes. Magnetic measurements above 85 K reveal the presence of some an tiferromagnetic exchange via 2,6-diaminopyridine moieties. The complex es are dimeric five-coordinate square-pyramidal with 2,6-diaminopyridi ne residues acting as bridges. The electronic spectra are interpreted in terms of the normalized spherical harmonic Hamiltonian theory and t he DT/DQ values which indicate that chromium complexes are slightly di storted, whereas those of manganese are severely distorted.