The interaction of nitric oxide with peralkyl compounds of Zn, Cu, Re, Cr, Mo, W, and Zr and with the phosphine complexes Ni(η-C₅H₅)Me(PPh₃), CoMe₃(PMe₃)₃, and RhMe(PPh₃)₃, and RhMe(PPh₃)₃ has been studied. In addition to N-alkyl-N-nitrosohydroxylaminate, ON(R)NO, complexes normally formed from diamagnetic alkyls, and η² or bridged nitrosoalkane, ONR, compounds usually obtained from paramagnetic alkyls, complexes with MO or M–O–M groups may be formed from the latter or from the interaction of NO with certain diamagnetic complexes that may give para-magnetic intermediates, e.g. by dissociation. Among new compounds characterised by i.r. and n.m.r. spectra are the tetrameric {Cu[ON(CH₂SiMe₃)NO]}₄, the nitric oxide adduct of hexamethylrhenium, ReMe₆(NO), the complex Re₂O₃Me₄(ONMe)₂, and the oxo-compounds of molybdenum and tungsten of stoicheiometry M₂O₃(NO)₂(ONR)₂, R = CH₂SiMe₃ or CH₂CMe₃. The interaction of molybdenum and tungsten hexacarbonyls with nitrobenzene and nitromethane gives oxo-species with ONR groups.