Unexpected NO Transfer Reaction between trans-[RuII(NO+)(NH3)4(L)]3+ and Fe(III) Species: Observation of a Heterobimetallic NO-Bridged Intermediate

• Published in: Inorganic chemistry 2014-05, Vol.53 (9), p.4475-4481
• Main Authors: Metzker, Gustavo, Lopes, Pietro P, da Silva, Augusto C. H, da Silva, Sebastiao C, Franco, Douglas W
• Format: Article
• Language: English
• Subjects: Electrochemistry; Electron Spin Resonance Spectroscopy; Ferric Compounds - chemistry; Kinetics; Metmyoglobin - chemistry; Nitric Oxide - chemistry; Ruthenium Compounds - chemistry
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/ic500122b

The reaction between trans-[RuII(NO+)(NH3)4(L)]3+, L = ImN, IsN, Nic, P(OMe)3, P(OEt)3, and P(OH)(OEt)2, and the Fe(III) species [FeIII(TPPS)], metmyoglobin, and hemoglobin was monitored by UV–vis, EPR, and electrochemical techniques (DPV, CV). No reaction was observed when L = ImN, IsN, Nic, and P(OH)(OEt)2. However, when L = P(OMe)3 and P(OEt)3, the reaction was quantitative and the products were trans-[RuIII(H2O)(NH3)4(P(OR)3)]3+ and [FeII(NO+)] species. Reaction kinetics data and DFT calculations suggest a two-step reaction mechanism with the initial formation of a bridged [Ru–(μNO)–Fe] intermediate, which was confirmed through electrochemical techniques (E 0′ = −0.47 V vs NHE). The calculated specific rate constant values for the reaction were in the ranges k 1 = 1.1 to 7.7 L mol–1 s–1 and k 2 = 2.4 × 10–3 to 11.4 × 10–3 s–1 for L = P(OMe)3 and P(OEt)3. The oxidation of the ruthenium center (Ru(II) to Ru(III)) containing the nitrosonium ligand suggests that NO can act as an electron transfer bridge between the two metal centers.