Bis(triphenyIphosphine)nitrogen(l+) nitrite (PPN(NO2)) has been found to be very effective for converting metal carbonyls into nitrosyl carbonyl complexes. The reactions are conducted in dipolar aprotic solvents such as tetrahydrofuran (THF) or acetonitrile and characteristically give high yields with no side products. The reaction has been successfully applied to Fe(CO)5, [Mn(CO)6]+, [Mn(CO)5(CH3CN)]+, [Fe(CO)2(PPH3)2(NO)]+, Mn(CO)4(NO), Mn2(CO)10, Co2(CO)8, Fe3(CO)12, Ru3(CO)12, Os3(CO)12, and Ru6C(CO)17 to generate CO2, a two-electron donor ligand (L), and the product, resulting in replacement of CO and L with NO and a negative charge. A kinetic analysis of the reaction of Fe(CO)5 and PPN(NO2) in acetonitrile verifies that the reaction is first order in iron and nitrite with k = 0.111 - 0.007 M-1 s-1 at 26 + 1 °C. The addition of a 10-fold excess of PPH3 had no effect on the rate of the reaction. The new nitrosylcarbonylmetalate, [Mn(CO)2(NO)2]-, was characterized by a single-crystal X-ray crystallographic study (P21/a space group, Z = 4, a = 21.890 (5) Å, β = 9.194 (3) Å, c = 17.495 (3) Å, β = 96.25 (2)°), which shows that it has a tetrahedral geometry with disordered NO and CO ligands. Characterization of the new clusters [Ru3(CO)10(NO)]- and [Os3(CO)10(NO)]- establishes that the NO is bridging one edge of the metal triangle, while spectroscopic evidence suggests that [Ru6C(CO)15(NO)]- contains a terminal nitrosyl ligand. Nitrogen-15 magnetic resonance spectra of the bridging nitrosyls exhibit a 400 ppm downfield shift relative to the resonanee of mononuclear nitrosyl carbonyl compounds. In some cases PPN(NO2) simply substitutes a NO2- for a carbonyl. This occuss with Co(CO)3(NO) to give the new nitro nitrosyl product [Co(NO2)(C-O)2(NO)]-.