Abstract
Nitric oxide (NO) is a key signaling molecule in health and disease. While nitrite acts as a reservoir of NO activity, mechanisms for NO release require further understanding. A series of electronically varied β-diketiminatocopper(II) nitrite complexes [Cu(II)](κ(2)-O(2)N) react with a range of electronically tuned triarylphosphines PAr(Z)(3) that release NO with the formation of O═PAr(Z)(3). Second-order rate constants are largest for electron-poor copper(II) nitrite and electron-rich phosphine pairs. Computational analysis reveals a transition-state structure energetically matched with experimentally determined activation barriers. The production of NO follows a pathway that involves nitrite isomerization at Cu(II) from κ(2)-O(2)N to κ(1)-NO(2) followed by O-atom transfer (OAT) to form O═PAr(Z)(3) and [Cu(I)]-NO that releases NO upon PAr(Z)(3) binding at Cu(I) to form [Cu(I)]-PAr(Z)(3). These findings illustrate important mechanistic considerations involved in NO formation from nitrite via OAT.