Copper(I) Nitrosyls from Reaction of Copper(II) Thiolates with <i>S</i>‑Nitrosothiols: Mechanism of NO Release from RSNOs at Cu

<i>S</i>-nitrosothiols (RSNOs) serve as ready sources of biological nitric oxide activity, especially in conjunction with copper centers. We report a novel pathway for the generation of NO within the coordination sphere of copper model complexes from reaction of copper­(II) thiolates with <i>S</i>-nitrosothiols. Reaction of tris­(pyrazolyl)­borate copper­(II) thiolates ^iPr2TpCu–SR (R = C₆F₅ or CPh₃) with ^tBuSNO leads to formation of ^iPr2TpCu­(NO) and the unsymmetrical disulfide RS–S^tBu. Quantum mechanical investigations with B3LYP-D3/6-311G­(d) suggest formation of a κ¹-N–RSNO adduct ^iPr2TpCu­(SR)­(R′SNO) that precedes release of RSSR′ to deliver ^iPr2TpCu­(NO). This process is reversible; reaction of ^iPr2TpCu­(NO) (but not ^iPr2TpCu­(NCMe)) with C₆F₅S–SC₆F₅ forms ^iPr2TpCu–SC₆F₅. Coupled with the facile, reversible reaction between ^iPr2TpCu­(NO) and C₆F₅SNO to give ^iPr2TpCu–SC₆F₅ and 2 equiv NO, we outline a new, detailed catalytic cycle for NO generation from RSNOs at Cu