Reduction–oxidation properties of organotransition-metal complexes. Part 31. Reductive elimination, oxidative addition and substitution, and migratory insertion in pentaphenylcyclopentadienylruthenium nitrosyl chemistry

Abstract

The complexes [RuBr(CO)L(η-C₅Ph₅)][1; L = PPh₃, PEt₃, P(OMe)₃, or P(OPh)₃] react with [NO][PF₆] in CH₂Cl₂ to give [RuBrL(NO)(η-C₅Ph₅)][PF₆][2; L = PPh₃, PEt₃, P(OMe)₃, or P(OPh)₃]; an excess of [NO][PF₆] with (1; L = PEt₃) yields [Ru(CO)(PEt₃)(NO)(η-C₅Ph₅)][PF₆]₂(3). The chemical reduction of (2) with [Co(η-C₅H₅)₂] gives [RuL(NO)(η-C₅Ph₅)][4; L = PEt₃, P(OMe)₃, or P(OPh)₃], but electrolytic reduction gives (4) and [RuX₂(NO)(η-C₅Ph₅)](5; X = Br), the latter via the reaction of (2) with Br^– ions. Cyclic voltammetry shows that [4, L = P(OPh)₃] is reversibly oxidised, but in the presence of PPh₃ oxidative substitution gives (4; L = PPh₃). Complex (4) also undergoes oxidative addition with halogens to give (5; X = Br or I). The reaction between [RuMe(CO)L(η-C₅Ph₆)][6; L = PEt₃, P(OMe)₃, P(OPh)₃, or CNBu^t] and [NO][PF₆] results in migratory insertion, giving [Ru(COMe)L(NO)(η-C₅Ph₅)][PF₆][7; L = PEt₃, P(OMe)₃, P(OPh)₃, or CNBu^t]. The one-electron reduction of (7) gives the neutral radicals [Ru(COMe)L(NO)(η-C₅Ph₅)][8; L = PEt₃, P(OMe)₃, P(OPh)₃, or CNBu^t] the e.s.r. spectra of which show extensive localisation of the unpaired electron on the nitrosyl ligand.