Reactions of laser-ablated cobalt atoms with CO and NO mixtures in excess argon during condensation at 7 K generate a series of unsaturated cobalt carbonyl nitrosyls including Co(CO)(NO), Co(CO)[NO], OCo-(NCO), CO(CO)(2)(NO), Co(CO)(2)[NO], and Co(CO)(NO)(2), and the saturated Co(CO)(3)(NO) molecule. The observed infrared bands of reaction products are identified by isotopic substitution, isotopic ratios, and isotopic distributions ((CO)-C-13,(NO)-N-15,(NO)-N-15-O-18, and mixtures). DFT/BPW91 vibrational fundamental calculations reproduced the observed frequencies and isotopic shifts very well. The isocyanate OCo(NCO) is formed from the side-bonded Co[NO] reaction with CO, which is relevant to catalytic reduction processes.