Cis-Dicarbonylbis(tributylphosphan)molybdän-Komplexe der vier isomeren bidiazine

Abstract

Abstract The complexes cis-Mo(CO)2(PBu3)2(bdz) which have the four isomeric bidiazine (bdz) ligands 3,3′-bipyridazine, 2,2′-bipyrazine, 2,2′- and 4,4′-bipyrimidine, can undergo reversible one-electron oxidation and reduction and show small redox potential differences of less than 1.5 V. The small HOMOLUMO gap gives rise to long-wavelength metal-to-ligand charge transfer absorptions, an assignment which is supported by ESR studies. Guidelines for the construction of complexes with small charge-transfer absorption energies by CO/PR3 exchange are presented. Although a ligand-centered MO is occupied during reduction, the small g factors of the radical complexes indicate low-lying ligand-field-excited states which are believed to be responsible for the pronounced light-sensitivity of the compounds.