Unexpected NO transfer reaction between trans -[RuII(NO +)(NH3)4(L)]3+ and Fe(III) species: Observation of a heterobimetallic no-bridged intermediate

Article abstract of DOI:10.1021/ic500122b

The reaction between trans-[Ru^II(NO⁺)(NH ₃)₄(L)]³⁺, L = ImN, IsN, Nic, P(OMe) ₃, P(OEt)₃, and P(OH)(OEt)₂, and the Fe(III) species [Fe^III(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-[Ru^III(H₂O)(NH₃) ₄(P(OR)₃)]³⁺ and [Fe^II(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 (E⁰′ = -0.47 V vs NHE). The calculated specific rate constant values for the reaction were in the ranges k₁ = 1.1 to 7.7 L mol^-1 s^-1 and k₂ = 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.