title: Reduction of nitrous oxide to dinitrogen by a mixed valent tricopper-disulfido cluster.
abstract: The greenhouse gas N(2)O is converted to N(2) by a mu-sulfido-tetracopper active site in the enzyme nitrous oxide reductase (N(2)OR) via a process postulated to involve mu-1,3 coordination of N(2)O 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, [L(3)Cu(3)(mu(3)-S(2))]X(2) (L = 1,4,7-trimethyl-triazacyclononane, X = O(3)SCF(3)(-) or SbF(6)(-)). This cluster exhibits spectroscopic features superficially similar to those of the active site in N(2)OR and reacts with N(2)O 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 N(2)O via its O-atom to a [L(2)Cu(2)(mu-S(2))](+) fragment and provide chemical precedence for an alternative pathway for N(2)O reduction by N(2)OR.
authors.affiliation: Department of Chemistry, Center for Metals in Biocatalysis, and Supercomputing Institute, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, USA.
authors.forename: Itsik
authors.initials: I
authors.lastname: Bar-Nahum
authors.forename: Aalo K
authors.initials: AK
authors.lastname: Gupta
authors.forename: Stefan M
authors.initials: SM
authors.lastname: Huber
authors.forename: Mehmed Z
authors.initials: MZ
authors.lastname: Ertem
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Cramer
authors.forename: William B
authors.initials: WB
authors.lastname: Tolman
mesh_terms: D001372:Aza Compounds / Q000737:chemistry; D001547:Benzaldehydes / Q000737:chemistry; D020134:Catalytic Domain; D003300:Copper / Q000737:chemistry*; D004220:Disulfides / Q000737:chemistry*; D008958:Models, Molecular; D009584:Nitrogen / Q000737:chemistry*; D009609:Nitrous Oxide / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D021241:Spectrometry, Mass, Electrospray Ionization; D013056:Spectrophotometry, Ultraviolet
chemical_list: C499747:1,4,7-trimethyl-1,4,7-triazacyclononane; D001372:Aza Compounds; D001547:Benzaldehydes; D004220:Disulfides; D009942:Organometallic Compounds; C064768:nitroveratraldehyde; D003300:Copper; D009609:Nitrous Oxide; D009584:Nitrogen