New arylruthenium(II) complexes of the P,C,P'-Coordinating terdentate monoanionic aryl ligands [C6H2(CH2PPh2)2-2,6-R-4]- (PCP-R-4; R = Ph, H). Synthesis of 16-electron species [RuIIX(PCP-R-4)(PPh3)] (X = Cl, L, OTf) and their reactivity toward the neutral terdentate N-donor ligand 2,2':6',2''-terpyridine (terpy)

Abstract

The synthesis and characterization of new, five-coordinate, diamagnetic, 16-electron arylruthenium(II) complexes [RuIIX{C6H2(CH2PPh2)2-2,6-R-4}(PPh3)] (1, X = Cl, R = H; 2, X = Cl, R = Ph; 3, X = OSO2CF3, R = H; 4, X = I, R = H) are described. These coordinatively unsaturated complexes contain a stable Caryl-Ru -bond resulting from pseudomeridional terdentate P,C,P'-bonding of the monoanionic {C6H2(CH2PPh2)2-2,6-R-4}- ligand (general abbreviation PCP-R-4; for R = H and R = Ph, abbreviated as PCP and PCP-Ph, respectively) that also provides two P Ru bonds. This bonding mode of the PCP-R-4 ligands adopted in complexes 1-4 means that these species are structurally closely related to the complexes [RuCl{C6H2(CH2NMe2)2-2,6-R-4}(PPh3)] (R = H, Ph) in which there is terdentate N,C,N'-coordination. Complexes 1 and 2 were synthesized via cyclometalation reactions of the respective neutral diphosphine compounds C6H3(CH2PPh2)2-2,6-R-4 (general abbreviation PC(H)P-R-4; for R = H and R = Ph, abbreviated as PC(H)P and PC(H)P-Ph, respectively) with [RuIICl2(PPh3)4]. The complex [RuII(OTf)(PCP)(PPh3)], 3, prepared by reaction of 1 with AgOTf (OTf = OSO2CF3 = triflate), has the triflate anion bound to ruthenium in noncoordinating solvents. On the NMR time scale complex 3 in solution exhibits temperature-dependent fluxionality that is associated with reversible changes of the complex stereochemistry. The triflate PCP complex 3 reacts cleanly with the neutral N-donor ligand 2,2':6',2''-terpyridine (terpy) to afford [RuII(PCP)(terpy)][OTf], 5. However, whereas the reaction of terpy with the PCP-Ph complex 2 affords [RuII(PCP-Ph)(terpy)]Cl, 6, its reaction with PCP chloro complex 1 generates a mixture of products. These reactivities of PCP and PCP-Ph complexes (1-3) toward terpy are compared and contrasted with those of related ruthenium complexes containing the monoanionic aryldiamine ligand {C6H2(CH2NMe2)2-2,6-R-4}- (abbreviated as NCN-R-4).