Synthesis and characterization of chromium(III), molybdenum(III), ruthenium(III) and osmium(III) complexes with N2O2-Schiff bases of 2-hydroxy-1-naphthaldimines

Monomolybdenum, monochromium, triosmium and triruthenium clusters, containing weakly coordinated ligands, are valuable starting materials for the preparation of a wide variety of compounds because of the ease with which these ligands can be displaced by another substrate under mild conditions. Four widely used complexes of this type are Mo(CO)(6), Cr(CO)(6), Os-3(CO)(12) and Ru-3(CO)(12) respectively. These complexes react with 2-hydroxy-1-naphthaldimines to give octahedral complexes which are characterized by elemental analyses, i.r. and u.v.-vis. spectra, molar conductances, d.t.a. and t.g.a. analyses, cyclic voltammetry, magnetic and e.s.r. measurements. The molar conductances in DMF solution indicate that the complexes are non-ionic. The i.r. spectra of complexes (3), (7) and (10) show m(CO) bands due to bonded CO groups, however complexes (6) and (13) show m(CO) bands due to bonded, bridged and terminal CO groups. The g(11)-values of the complexes indicate that they have covalent bond character. Also, the electrochemical reduction of the complexes has been discussed.