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

Reaction of [Ru(Me₃tacn)(PMe₃)₂(O₂CCF ₃)]PF₆ with one equivalent of t-BuNC or 4-cyano-1-isocyano-2,6-diisopropylbenzene (L′) in refluxing 1,2-dichloroethane gave [Ru(Me₃tacn)(PMe₃)(t-BuNC)(O₂CCF ₃)]PF₆ (1)·PF₆ and [Ru(Me₃tacn)(PMe₃)(L′)(O₂CCF ₃)]PF₆ (3)·PF₆, respectively. In the presence of zinc amalgam, reactions of [Ru(Me₃tacn)(H₂O)₂(O₂CCF ₃)](OTf)₂, trans-[Ru(16-TMC)Cl₂]Cl and cis-[Ru(2,2,2-tet-Me₆)Cl₂]PF₆ with an excess of t-BuNC in 1,2-dichloroethane, followed by anion metathesis, afforded [Ru(Me₃tacn)(t-BuNC)₂(O₂CCF ₃)]PF₆ (2)·PF₆, trans-[Ru(16-TMC)(t-BuNC)₂](ClO₄)₂ (4)·(ClO₄)₂ and cis-[Ru(2,2,2-tet-Me₆)(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(Ru^III/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 π-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. © 2000 Elsevier Science S.A.