Voltammetry of half-sandwich manganese group complexes of η 6-PhC 3B 7H 9 and η 5-C 60Bn 2PhH 2, two ligands that are cyclopentadienyl mimicks

• Published in: Inorganica Chimica Acta Vol. 364; no. 1; pp. 251 - 254
• Main Authors: Stewart, Michael P., Butterick, Robert, Sneddon, Larry G., Matsuo, Yutaka, Geiger, William E.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 2010
• Subjects: Anodic oxidation; Cathodic reduction; Cyclopentadienyl mimick; Electrochemical ligand parameter; Electrochemistry; Fullerene; Half-sandwich; Manganese carbonyl; Perfluorotetraphenyl borate; Rhenium carbonyl; Tricarbadecaborane; Weakly coordinating anion; Fullerene; Anodic oxidation; Tricarbadecaborane; Half-sandwich; Weakly coordinating anion; Manganese carbonyl; Electrochemistry; Electrochemical ligand parameter; Perfluorotetraphenyl borate; Rhenium carbonyl; Cyclopentadienyl mimick; Cathodic reduction
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/j.ica.2010.05.040

The E 1/2 potentials of both the oxidation and reduction of manganese and rhenium half-sandwich complexes have been measured in CH 2Cl 2 and THF containing [NBu 4][B(C 6F 5) 4]. Three tricarbadecaboranyl compounds and one penta-organo fullerene compound were studied. The one-electron oxidation of the Re compounds give radical cations that do not dimerize on the voltammetry time scale. A ligand electronic parameter of 0.63 has been determined for the PhC 3B 7H 9 ligand in these complexes, 0.30 V positive of that of the cyclopentadienyl ligand. The potentials of a series of one-electron oxidation and reduction reactions have been determined for manganese group half-sandwich complexes of the tricarbadecaboranyl ligand PhC 3B 7H 9 and the penta-organo fullerene ligand C 60Bn 2PhH 2 (Bn = benzyl). The anodic processes were studied in CH 2Cl 2 and the cathodic processes were studied in both CH 2Cl 2 and THF, the supporting electrolyte being [NBu 4][B(C 6F 5) 4]. The manganese complex Mn(CO) 2(PMe 3)(PhC 3B 7H 9) ( 1) is a member of a three-electron transfer series which includes oxidation to 1 + (0.51 V versus ferrocene) and successive reductions to 1 − (−1.66 V) and 1 2− (−1.77 V). Both the oxidation and reduction of the closely-related complex Mn(CO) 2(PPh 3)(PhC 3B 7H 9) ( 2) are chemically irreversible under slow-scan cyclic voltammetry conditions. The rhenium complex Re(CO) 2(PPh 3)(PhC 3B 7H 9) ( 3) oxidizes ( E 1/2 = 0.82 V versus ferrocene) to a radical cation which, unlike its cyclopentadienyl analogue, shows no evidence of dimerization. Oxidation of the fullerene-based complex Re(CO) 3(C 60Bn 2PhH 2) is more facile than that of its cyclopentadienyl analogue, in contrast to previous findings in this class of metal-fullerene derivatives. An electrochemical ligand factor, E L, of 0.63 is calculated for the PhC 3B 7H 9 ligand in manganese group half-sandwich complexes.