Reductive NO Coupling at Dicopper Center via a [Cu₂(NO)₂]²⁺ Diamond-Core Intermediate

Abstract

Treatment of a dicopper(I,I) complex with excess amounts of NO leads to the formation of a dicopper dinitrosyl [Cu 2 (NO) 2 ] 2+ complex capable of (i) releasing two equivalents of NO reversibly in 90% yield and (ii) reacting with another equivalent of NO to afford N 2 O and dicopper nitrosyl oxo species [Cu 2 (NO)(O)] 2+ . Resonance Raman characterization of the [Cu 2 (NO) 2 ] 2+ complex shows a 15 N-sensitive N�O stretch at 1527.6 cm −1 and two Cu−N stretches at 390.6 and 414.1 cm −1 , supporting a symmetric diamond-core structure with bis-μ-NO ligands. The conversion of [Cu 2 (NO) 2 ] 2+ to [Cu 2 (NO)O] 2+ occurs via a rate-limiting reaction with NO and bypasses the dicopper oxo intermediate, a mechanism distinct from that of diFe-mediated NO reduction to N 2 O.

Reductive Coupling of Nitric Oxide by Cu(I): Stepwise Formation of Mono- and Dinitrosyl Species En Route to a Cupric Hyponitrite Intermediate

“…As described above, the next intermediate D evidenced by the stopped-flow analysis corresponds to the addition of a cuprous ion complex to the dinitrosyl species 1-(NO) 2 . The DFT modeling for this intermediate supports a Cu 2 (NO) 2 diamond-core structure (Figures and S56), as most recently described by Zhang and co-workers and also similar to a recent motif found in iron-nitrosyl chemistry . Our calculations (see pages S56 and S57) indicate a Cu I oxidation state with dissociation of one pyridine ring per copper (Cu–N distance of 3.01 Å) (Tables S5.3.1–S5.3.2) to facilitate the formation of the diamond core with pentacoordinate Cu I centers (Figure ).…”

Two-State Hydrogen Atom Transfer Reactivity of Unsymmetric [Cu2(O)(NO)]2+ Complexes

“…In our previous studies, we prepared the symmetric [ H L Cu 2 (O)­(NO)] 2+ species (Figure C) by activating nitrite or NO at the dicopper center. , This complex exhibits HAT, C–H hydroxylation, and S -nitrosation reactivity. , We initially assigned [ H L Cu 2 (O)­(NO)] 2+ as an S = 1/2 species based on the S = 1/2 EPR signal around 300 mT and the NO – stretch at 1554 cm –1 . However, a recent computational study by Yoshizawa and Shiota proposed an alternative S = 3/2 state for the [ H L Cu 2 (O)­(NO)] 2+ complex …”