Syntheses and electrochemical characterization of heteroleptic cyclopentadienyl-bis(dithiolene) complexes of niobium and tantalum

Diamagnetic niobium and tantalum complexes of general formula [M(η5-C5Me5)(dithiolene)2] have been prepared (M = Nb, dithiolene = dddt2– (5,6-dihydro-1,4dithiine-2,3-dithiolate) (1); M = Ta, dithiolene = dddt2– (2); M = Nb, dithiolene = dddt2– and dmit2– (1,3-dithiole-2-thione-4,5-dithiolate) (3)). All these complexes exhibit temperature-dependent 1H NMR spectra which result from a fluxional behavior of the dithiolene ligands. Their redox properties have been investigated by cyclic voltammetry and reversible oxidation processes involving the dithiolene ligands have been evidenced for the complexes 1 and 2.Key words: niobium, tantalum, dithiolene, voltammetry cyclic, variable-temperature 1H NMR.