Synthesis and Spectro‐electrochemical Aspects of [RuII(trpy)(pdt)(X)]n+ (trpy = 2,2′:6′,2″‐Terpyridine, pdt = 5,6‐Diphenyl‐3‐pyridyl‐as‐triazine, X = Cl–, CH3CN, NO2–, NO+, NO·) – Electrophilicity of {RuII–NO+} and Photolability of {RuII–NO·}

Abstract

AbstractNitrosylruthenium derivatives having NO+ and NO· states have been synthesized in a stepwise manner starting from [RuII(trpy)(pdt)(Cl)](ClO4) {[1](ClO4)} → [RuII(trpy)(pdt)(CH3CN)](ClO4)2 {[2](ClO4)2} → [RuII(trpy)(pdt)(NO2)](ClO4) {[3](ClO4)} → [RuII(trpy)(pdt)(NO+)](ClO4)3 {[4](ClO4)3} → [RuII(trpy)(pdt)(NO·)](ClO4)2 {[4](ClO4)2} [trpy = 2,2′:6′,2″‐terpyridine, pdt = 5,6‐diphenyl‐3‐pyridyl‐as‐triazine]. The molecular identity of [1](ClO4) and [2](ClO4)2 and the subsequent stereoretentive transformation of [1](ClO4) → [2](ClO4)2 have been authenticated by single‐crystal X‐ray structures. Electrochemical and spectral features are investigated as a function of the monodentate ligands (Cl–, CH3CN, NO2–, NO+, NO·). The kinetic and thermodynamic aspects of the reaction of the moderately strong electrophilic {RuII–NO+} center [ν(NO): 1944 cm–1] in [4]3+ with a nucleophile such as OH– have been studied. The nitrosyl species [RuII(trpy)(pdt)(NO+)]3+ ([4]3+) can be selectively reduced to [RuII(trpy)(pdt)(NO·)]2+ ([4]2+) electrochemically as well as chemically by hydrazine hydrate. On exposure to light an acetonitrile solution of [RuII(trpy)(pdt)(NO·)]2+ ([4]2+) undergoes slow photocleavage of the RuII–NO bond over a period of 4 h, resulting in the corresponding solvated species [RuII(trpy)(pdt)(CH3CN)]2+ ([2]2+). The rate of photolability of the RuII–NO bond in [4]2+ has been monitored spectrophotometrically. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)