Chemical Reduction of Metal-bound NO

Although both conversions are exergonic, they are kinetically disfavored, having large activation energies. Using heterogeneous catalysts has been an active area 

We start our discussions with reactions of CO with coordinated NO. In early studies, Johnson and Bhaduri demonstrated a stoichiometric CO reduction of iridium-bound NO to give free N2O while also producing CO2 [93]  

The authors postulated a reaction mechanism involving an O-atom transfer from a coordinated NO to the neighboring CO, followed by an intramolecular attack of the second coordinated NO group on the Ir-N system, invoking a ni-trene [94] intermediate. However, follow-up studies employing isotopically labeled NO ( NO) mled out this nitrene intermediate possibihty and provided evidence for dinitrogen dioxide (N2O2) as the reactive intermediate which transfers an O-atom to CO [90, 95, 96). 

A catalytic NO reduction was effected by the anionic complex [RhCl2(CO)2] using H2O, HCl and ethanol [90, 92). An 0 isotopic-Iabehng experiment indicated that one of the O-atoms in the CO2 product is derived from the water in the reaction medium and not directly from the NO reactant [97]. 

Kubota and coworkers [88, 89] developed a homogeneous NO reduction system, which utilized PdCl2 and CUCI2 (or CuCl) as catalysts in acidic aqueous medium. Their results rather resemble a Wacker chemistry process  

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