SYNTHESES AND ELECTROCHEMICAL-BEHAVIOR OF NOVEL DITHIOLATONIOBIUM-(IV) AND -(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 a cetonitrile 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 subs equent reactions. Among the three niobium(IV) complexes, the reduction potential of the complex with dddt was notably less negative than tho se of the complexes with dmit or dmio. This fact allows the preparatio n of the charge-transfer complexes with TCNQ. The niobium(V) dmit and dmio complexes with two cyclopentadienyl rings were also isolated as i odide salts by the oxidation of the corresponding niobium(IV) complex. These Nb-V complexes gave two one-electron reduction steps whose pote ntials were identical to those of Nh(IV) and Nb-III for niobium(IV) dm it and dmio complexes.