Nitrito‐O,O‐copper complexes and dinitrogen oxide are the products of the reaction of excess NO with the nitrosyl complexes [LCu(NO)] (L = substituted tris(pyrazolyl)hydroborate), a process that models environmentally important transformations carried out by copper ions in proteins and zeolites. According to the results of kinetic studies, the involvement of dimeric copper species in the rate‐determining step is ruled out, which suggests that NO coupling occurs at a single metal ion. Copyright © 1994 by VCH Verlagsgesellschaft mbH, Germany