Isocyanide ligation at ruthenium(II) complexes with chelating tertiary amine and porphyrin ligands. Structural and electrochemical studies

Reaction of [Ru(Me(3)tacn)(PMe3)(2)(O2CCF3)]PF6 with one equivalent of t-BuNC or 4-cyano-1-isocyano-2,6-diisopropylbenzene (L') in refluxing 1,2-dichloroethane gave [Ru(Me(3)tacn)(PMe3)(t-BuNC)(O2CCF3)]PF6 (1) . PF6 and [Ru(Me(3)tacn)(PMe3)(L')(O2CCF3)]PF6 (3) . PF6, respectively. In the presence of zinc amalgam, reactions of [Ru(Me(3)tacn)(H2O)(2)(O2CCF3)](OTf)(2), trans-[Ru(16-TMC)Cl-2]Cl and cis-[Ru(2,2,2-tet-Me-6)Cl-2]PF6 with an excess of t-BuNC in 1,2-dichloroethane, followed by anion metathesis, afforded [Ru(Me(3)tacn)(t-BuNC)(2)(O2CCF3)]PF6 (2) . PF6, trans-[Ru(16-TMC)(t-BuNC)(2)](ClO4)(2) (4) .(ClO4)(2) and cis-[Ru(2,2,2-tet-Me-6)(t-BuNC)(2)](PF6)(2) (5) .(PF6)(2), respectively. Treatment of [Ru(Por)(CO)(MeOH)] (Por = TPP, 4-MeO-TPP or 4-F-TPP) with an excess of t-BuNC or L' gave [Ru(TPP)(t-BuNC)(2)] (6) or [Ru((4)-MeO-TPP)(L')(2)] (7) and [Ru(4-F-TPP)(L')(2)] (8), respectively. 1 . PF6-5 .(PF6)(2) display a quasi-reversible Ru(III/II) couple at potentials ranging from +0.65 to +1.42 V vs. FeCp2+/0. The E-1/2(RuIII/II) of 5 .(PF6)(2) (+1.42 V vs. FeCp2+/0) is notably high compared with that of 4 .(ClO4)(2)(+0.65 V), reflecting the strong pi-back-bonding in the cis-bis(tert-butyl isocyanide)ruthenium(II) complex. Irrespective of the overall charge, the cationic complex 4 and the neutral complexes 6-8 all exhibit a virtually linear RNC-Ru-CNR moiety. (C) 2000 Elsevier Science S.A. All rights reserved.