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The novel pH dependences of both the activation process and catalysis by activated Achromobacter cycloclastes [N.sub.2]OR, which has indicated that the enzyme might use multiple mechanisms for [N.sub.2]O reduction, are presented. The results have shown that the transition state is stabilized by H-bonding interactions between the active site and an [N.sub.2]O-derived intermediate bound to the catalytic [Cu.sub.z] cluster.

The nickel (I) complex [PhTt(super Ad]Ni(CO) (PhTt(super Ad)), phenyltris((1-adamantylthio)methyl)borate) reacts with O(sub 2) generating a 1:1 species identified as a side-on dioxygen adduct based on its spectroscopic properties as supported by DFT computational results and by its reactivity. The successful pursuit of the strategy, which led to the discovery of a side-on dioxygen complex of nickel, is reported.

Research has been conducted on Ni (super)+ four-coordinate complex. Results demonstrate that this complex serves as a Ni-CO reaction intermediate in the acetyl-CoA synthase catalytic cycle.

Nitrous oxide reductase (N2OR) from Achromobacter cycloclastes (Ac) can be reductively activated with reduced methyl viologen over a broad range of pH. Activated Ac N2OR displays a complex activity profile as a function of the pH at which catalytic turnover is measured. Spectroscopic and steady-state kinetics data suggest that [H+] has multiple effects on both the activation and the catalytic reactions. These experimental results are in good agreement with previous theoretical studies, which suggested that the transition state is stabilized by H-bonding interactions between the active site and an N2O-derived intermediate bound to the catalytic Cuz cluster. [ABSTRACT FROM AUTHOR]

The nickel(I) complex [PhTtAd]Ni(CO) (PhTtAd, phenyltris((1-adamantylthio)methyl)borate reacts with O2 generating a 1:1 species identified as a side-on dioxygen adduct based on its spectroscopic properties as supported by DFT computational results and by its reactivity. The Ni EXAFS data are fit to a S2O2 coordination environment with short Ni-O distances, 1.85 Å. The brown complex displays a rhombic EPR signal with g values of .24, 2.19, 2.01. DFT and INDO/S-CI computations replicate the EXAFS and EPR features and suggest that 2 is a side-on [NiO2]+ complex with geometric and electronic properties that are best rationalized in terms of a highly covalent Ni(II)-suprexo description. (PhTtAd]-Ni(O2) oxidizes PPh3 to OPPh3-, and [PhTttBu]Ni(CO) to the nonsymmetric [PhTtAdNi(μ-O) 2Ni[PhTttBu]dimer. [ABSTRACT FROM AUTHOR]

Two highly reactive heterodinuclear bis(mu-oxo) complexes were prepared by combining mononuclear peroxo species with reduced metal precursors at -80 degrees C and were identified by UV-vis, EPR/NMR, and resonance Raman spectroscopy, with corroboration in the case of the CuPd system from density functional calculations.