Isocyanide ligation at ruthenium(II) complexes with chelating tertiary amine and porphyrin ligands. Structural and electrochemical studies
ABSTRACT Reaction of [Ru(Me3tacn)(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(Me3tacn)(PMe3)(t-BuNC)(O2CCF3)]PF6 (1)·PF6 and [Ru(Me3tacn)(PMe3)(L′)(O2CCF3)]PF6 (3)·PF6, respectively. In the presence of zinc amalgam, reactions of [Ru(Me3tacn)(H2O)2(O2CCF3)](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(O2CCF3)]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 E1/2(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 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.