Synthesis, characterization and reactivity of trans-[RuCl(NO)(bpydip)]2+{bpydip = N,N-bis(7methyl-2-pyridylmethylene)-1,3-diiminopropane}: a novel nitrosyl ruthenium complex displaying high electronic delocalization

A novel trans-[RuCl(NO)(bpydip)]2+ species has been obtained by the reaction of nitrite ions with trans-[RuCl2 (bpydip)]{bpydip =N,N-bis(7-methyl-2-pyridylmethylene)-1,3-diiminopropane}, and extensively characterized by means of elemental analysis, cyclic voltammetry, UV/Visible, FTIR, 1H NMR and EPR spectroscopy. The electrochemistry in acetonitrile solution, consists of two sets of reversible redox processes ascribed to the RuIII/II(E1/2=+1.92 V versus NHE) and NO+/(E1/2=+0.34 V) redox couples. A relatively high (NO) stretching frequency (1920 cm–1) has been observed in the FTIR spectra, indicating a NO+ character, while the absence of EPR signals is also consistent with the RuII–NO+ formulation. The reduction of the complex was monitored spectroelectrochemically, exhibiting a shift of (NO) to 1890 cm–1; and giving rise to characteristic EPR signals which evidence the NO character in the product. The nitrosyl (NO+) species reacts with H2O according to the equation [RuCl(NO)(bpydip)]2++ H2O [RuCl(NO2)(bpydip)]+ 2H+, leading to a pseudo-first order rate constant of 1.40 (± 0.02)× 10–2 s–1, H= 47 (± 1) kJ mol–1 and S= 122 (± 4) J K–1 mol–1.