High-spin organometallic derivatives of iron(III) and iron(II) stabilised by a quadridentate Schiff's base ligand

Abstract

The preparation and properties of organometallic derivatives of the Schiff's base complex NN′-ethylenebis(salicylideneiminato)iron(III), Fe(saen)R (R = Ph, CH₂Ph) are reported. Experimental evidence exists for Fe(saen)COCH₃, but no pure product was obtained. Magnetic susceptibility measurements at different temperatures show that the compounds are high-spin, the first examples of high-spin organometallic compounds of iron(III). The preparations involve the treatment of the [Fe(saen)]^– anion with benzyl chloride or the reaction of the phenyl Grignard reagent with the iodo-derivative Fe(saen)l. NN′-Ethylenebis(salicylideneiminato)iron(II), Fe(saen), has been shown to undergo addition reactions with cyclohexyl isocyanide, giving the 1 : 1 adduct, Fe(saen)-CNC₆H₁₁. I.r. spectra and the failure to obtain the similar adduct with carbon monoxide confirm that isocyanides are in general poorer π-acceptors and better σ-donors than carbon monoxide.