Electrochemistry and spectroelectrochemistry of [Re(1,2-bis(dimethylphosphino)ethane) 3]

• Published in: Inorganica Chimica Acta 1997-10, Vol.262 (2), p.195-202
• Main Authors: Kirchhoff, Jon R., Allen, Melanie R., Cheesman, Bruce V., Ken-ichi Okamoto, Heineman, William R., Deutsch, Edward
• Format: Article
• Language: English
• Subjects: Diphosphine complexes; Electrochemistry; Rhenium complexes; Spectroelectrochemistry
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/S0020-1693(97)05523-0

The electrochemical properties of [Re(dmpe) 3] +, where dmpe is 1,2-bis(dimethylphosphino)ethane, have been investigated in aqueous and non-aqueous solutions by cyclic and square wave voltammetry as well as by thin-layer electrochemical and spectroelectrochemical techniques. The redox behavior in N, N-dimethylformamide (DMF) is described in terms of three interrelated one-electron oxidations and the chemistry from decomposition of electrogenerated Re(III) species. The first and third redox processes are assigned to the oxidation of [Re(dmpe) 3] + to [Re(dmpe) 3] 2+ and [Re(dmpe) 3] 2+ to [Re(dmpe) 3] 3+; the corresponding E p values from square wave voltammetry are +0.336 and +1.120 V versus Ag/AgCl (3 M NaCl). The second redox process (+0.884 V) is described as the oxidation of an Re(II) species, [Re(dmpe) 2(η 1-dmpe)S] 2+ (S=a solvent molecule), which is proposed as an intermediate in the dissociation of a dmpe ligand. Complete dissociation of dmpe occurs from the Re(III) complexes to yield a species denoted as [Re(dmpe) 2S 2] 3+, which is reduced with a peak potential from square wave voltammetry at −0.288 V in DMF. Identification of this species as a bis(dmpe) complex is accomplished by comparison of its FAB mass spectrum, UV–Vis spectrum, HPLC retention time, and electrochemical properties to those of an independently synthesized complex, where S is replaced by Cl −.