Reactions of several metal carbonyls with chelating ligands containing active protons have been carried out. The reactions of hexacarbonylchromium and hexacarbonylmolybdenum with N-methylsalicylideneimine led to the formation of the corresponding N-methylsalicylideneiminato-complexes of chromium(III) and molybdenum(III). These are most probably monomeric octahedral complexes as suggested by the magnetic moments which are somewhat lower than the spin-only value, as expected for a d3 octahedral configuration. Reactions of decacarbonyldimanganese with NN′-ethylenebis(salicylideneimine), SaEnH2, and with NN′-trimethylenebis(salicylideneimine) yielded the corresponding manganese(II) complexes; the NN′-trimethylenebis(salicylideneiminato)-derivative was found to absorb one mol. of oxygen as previously announced but no confirmation could be found of a similar absorption of molecular nitrogen. Pentacarbonyliron and SaEnH2 gave the air-sensitive FeSaEn together with some reaction by-products which were not fully identified. FeSaEn is a high-spin compound of d6 configuration and is converted by molecular oxygen into the µ-oxo-iron(III) derivative. If the trans-effect is of some importance in octahedral complexes, it seems that for bivalent metals and with bidentate ligands co-ordination of carbonyl groups to the metal should lead preferentially to cis-octahedral structures, whereas with quadridentate planar ligands the co-ordination of two carbonyl groups, necessarily occupying trans-positions, is probably not very likely to occur. These ideas have been tested with ruthenium and found to be reasonably well confirmed. Dodecacarbonyltriruthenium and acetylacetone, acacH, give the first example of a bis(acetylacetonato)carbonyl derivative, namely cis-Ru(acac)2(CO)2. Dodecacarbonyltriruthenium and the Schiff's base N-phenylsalicylideneimine, Ph–SaEnH, gave cis-Ru(Ph–SaEn)2(CO)2, a rather labile complex in polar solvents. Dodecacarbonyltriruthenium and SaEnH2 gave a very robust compound of probable formula RuSaEn,CO; a dimeric structure with terdentate oxygens has been suggested for this complex. Octacarbonyldicobalt and SaEnH2 gave CoSaEn in dimethylformamide. Octacarbonyldicobalt and NN′-ethylenebis(acetylacetoneimine), acacimH2, by gentle heating in heptane gave the tetracarbonylcobaltate [Co(acacimH2)3][Co(CO)4]2. The cobalt(II) derivative Co acacim reacts promptly with nitric oxide to give the nitrosyl derivative Co acacim NO.