Electron transfer reactions of (C5R5)2(CO)2Ti (R=H or Me) with TCNE or TCNQ: Spectroelectrochemical assignment of metal and ligand oxidation states in [(C5Me5)2(CO)Ti(TCNX)]2−/−/o/+

The TCNX ligands TCNE (tetracyanoethene) and TCNQ (7,7,8,8-tetracyano-p-quinodimethane) react instantaneously with (C5R5)2(CO)2Ti, R=H or Me, to yield highly air-sensitive mononuclear complexes (C5R5)2(CO)Ti(TCNX) of which the soluble species (R=Me) were characterized also in the oxidized and reduced forms through cyclic voltammetry, EPR, IR and UV–vis spectroelectrochemistry. While oxidation at rather low potentials yields labile carbonyltitanium(IV) species of the TCNXradical dot− ligands, the reduction occurs stepwise at unusually negative potentials, first on the ligand (to yield coordinated TCNX2−) and then on the metal (to form TiII). For the neutral complexes (C5R5)2(CO)Ti2+q(TCNX−q) the results support a rather large amount of charge transfer 1