NEW ARYLRUTHENIUM(II) COMPLEXES OF THE P,C,P'-COORDINATING TERDENTATEMONOANIONIC ARYL LIGANDS [C6H2(CH(2)PPH(2))(2)-2,6-R-4](-) (PCP-R-4, R=PH,H) - SYNTHESIS OF 16-ELECTRON SPECIES [RU(II)X(PCP-R-4)(PPH(3))] (X=CL,I,OTF) AND THEIR REACTIVITY TOWARD THE NEUTRAL TERDENTATE N-DONOR LIGAND 2,2'6',2''-TERPYRIDINE (TERPY)

The synthesis and characterization of new, five-coordinate, diamagneti c, 16-electron arylruthenium(II) complexes [Ru(II)X{C6H2(CH(2)PPh(2))( 2)-2,6-R-4}(PPh(3))] (1, X = Cl, R = H; 2, X = Cl, R = Ph; 3, X = OSO2 CF3, R = H; 4, X = I, R = H) are described. These coordinatively unsat urated complexes contain a stable C-aryl-Ru sigma-bond resulting from pseudomeridional terdentate P,C,P'-bonding of the monoanionic {C6H2(CH (2)PPh(2))(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 cl osely related to the complexes [RuCl{C6H2(CH(2)NMe(2))(2)-2,6-R-4}(PPh (3))] (R = H, Ph) in which there is terdentate N,C,N'-coordination. Co mplexes 1 and 2 were synthesized via cyclometalation reactions of the respective neutral diphosphine compounds C6H3(CH(2)PPh(2))(2)-2,6-R-4 (general abbreviation PC(H)P-Rd; for R = H and R = Ph, abbreviated as PC(H)P and PC(H)P-Ph, respectively) with [(RuCl2)-Cl-II(PPh(3))(4)]. T he complex [Ru-II(OM(PCP)(PPh(3))], 3, prepared by reaction of 1 with AgOTf (OTf = OSO2CF3 = triflate), has the triflate anion bound to ruth enium in noncoordinating solvents. On the NMR time scale complex 3 in solution exhibits temperature-dependent fluxionality that is associate d 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 [Ru-II(PCP)(terpy)][OTf], 5. Howeve r, whereas the reaction of terpy with the PCP-Ph complex 2 affords [Ru -II(PCP-Ph)(terpy)]Cl, 6, its reaction with PCP chloro complex 1 gener ates a mixture of products. These reactivities of PCP and PCP-Ph compl exes (1-3) toward terpy are compared and contrasted with those of rela ted ruthenium complexes containing the monoanionic aryldiamine ligand {C6H2(CH(2)NMe(2))(2)-2,6-R-4}(-) (abbreviated as NCN-R-4).