Reactions of some metal carbonyls with chelating compounds containing active protons, especially Schiff's bases

Abstract

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.