Thermolysis of Iron <i>N</i>-Allylaminocarbene Complexes: Formation of η³-1-Azaallylirontricarbonyl Complexes. Synthetic and Theoretical Study

Abstract

Both chelated and nonchelated N-allyl-N-methylaminocarbene complexes of iron unsubstituted at the 1- and 3-positions of an allyl substituent afforded by thermolysis new η3-iron tricarbonyl complexes of 2,3-dihydropyrrole. The proposed mechanism of these reactions involves bicyclo[2.1.1]-2-aza-5-ferrahexane as an intermediate formed by [2+2] cycloaddition. Formation of this intermediate requires antiparallel arrangement of FeC and CC double bonds in the cycloaddition step. This mechanism was supported by reaction of deuterium-labeled complexes and by the density functional calculations of B3LYP quality. The structure of tricarbonyl[(η3-N-methyl-2-(biphenyl-4-yl)-4,5-dihydropyrrole]iron(0) (4f) has been determined by X-ray diffraction.