SYNTHESES AND ELECTROCHEMICAL-BEHAVIOR OF NOVEL DITHIOLATONIOBIUM-(IV) AND DITHIOLATONIOBIUM-(V) COMPLEXES WITH 2 ETA(5)-CYCLOPENTADIENYL RINGS

Novel niobium(IV) complexes with two cyclopentadienyl rings and dmit, dmio or dddt were synthesized, and their voltammometric behaviour was investigated in acetonitrile and dichloromethane. These complexes in acetonitrile solution exhibited a reversible one-electron oxidation and a reversible one-electron reduction step, corresponding to niobium(V) and niobium(III) respectively, without any complicating side- or subsequent reactions. Among the three niobium(IV) complexes, the reduction potential of the complex with dddt was notably less negative than those of the complexes with dmit or dmio. This fact allows the preparation of the charge-transfer complexes with TCNQ. The niobium(V) dmit and dmio complexes with two cyclopentadienyl rings were also isolated as iodide salts by the oxidation of the corresponding niobium(IV) complex. These Nb-V complexes gave two one-electron reduction steps whose potentials were identical to those of Nh(IV) and Nb-III for niobium(IV) dmit and dmio complexes.