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

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 CNBut] 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 CNBut]. 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 CNBut] the e.s.r. spectra of which show extensive localisation of the unpaired electron on the nitrosyl ligand.