The structure, binding energies, and vibrational frequencies have been determined for CuNO2 and AgNO2 in different coordination modes. Calculations have been performed using ab initio theoretical methods that include electron correlation and methods based on the density functional approach. Three structures are found to be stable minima on the potential energy surface: the C2v bidentate η2+O,O, , a Cs monodentate η1-O and the C2v monodentate η1-N structures. For both CuNO2 and AgNO2 systems the η1-O,O coordination is found to be the most stable structure. The computed dissociation energies of CuNO2 and AgNO 2 are 56 and 47 kcal/mol, respectively. © 1995 American Institute of Physics.