Effect of the cis- and trans-[1,2-bis(diphenylphosphino)ethylene] ligands in the properties of diphosphine–polypyridyl complexes of ruthenium(II): Application to electrocatalytic oxidations of organic compounds

The ruthenium(II) complexes [Ru(cis-L)(totpy)(H2O)](PF6)2 (1) and [Ru(trans-L)2(totpy)(H2O)](PF6)2 (2) (L = 1,2-bis(diphenylphosphino)ethylene; totpy = 4′-(4-tolyl)-2,2′:6′,2″-terpyridine) were synthesized and characterized by elemental analysis, cyclic and differential pulse voltammetries and UV–vis, IR and 31P NMR spectra. The redox potentials of 2 are less anodic than those of 1. The redox potentials are a result of the different environments created by the phosphine ligands in the trans-complex, associated with their electron donating effect. Electrocatalytic oxidations of benzyl alcohol, cyclohexanol, 1-pentanol, 1,2-butanediol, 1,4-butanediol and cyclohexene were performed using complexes 1 and 2 both in solution and immobilized in carbon paste electrode.

Graphical abstractThe ruthenium(II) complexes [Ru(cis-L)(totpy)(H2O)](PF6)2 (a) and [Ru(trans-L)2(totpy)(H2O)](PF6)2 (b) (L = 1,2-bis(diphenylphosphino)ethylene; totpy = 4′-(4-tolyl)-2,2′:6′,2″-terpyridine) were synthesized. They were used, in solution and immobilized in carbon paste electrode, as catalysts in electrocatalytic oxidations of benzyl alcohol, cyclohexanol, 1-pentanol, 1,2-butanediol, 1,4-butanediol and cyclohexene. Figure optionsDownload full-size imageDownload as PowerPoint slide