Abstract
The greenhouse gas N2O is converted to N-2 by a mu-sulfido-tetracopper active site in the enzyme nitrous oxide reductase (N2OR) via a process postulated to involve mu-1,3 coordination of N2O to two Cu(I) ions. In efforts to develop synthetic models of the site with which to test mechanistic hypotheses, we have prepared a localized mixed valent Cu(II)Cu(I)(2) cluster bridged in a mu.eta(2):eta(1):eta(1) fashion by disulfide, [L3Cu3(mu(3)-S-2)]X-2 (L = 1,4,7-trimethyl-triazacyclononane, X = O3SCF3- or SbF6-). This cluster exhibits spectroscopic features superficially similar to those of the active site in N2OR and reacts with N2O to yield N-2 in a reaction that models the function of the enzyme. Computations implicate a transition state structure that features mu-1,1-bridging of N2O via its O-atom to a [L2Cu2(mu-S-2)](+) fragment and provide chemical precedence for an alternative pathway for N2O reduction by N2OR.