Molecular properties of a bis(ketoiminato)-bis(tricarbonyliron) complex obtained by symmetric cleavage from acetophenone azine. Idealized symmetry inanti and syn isomers studied by X-ray diffraction, NMR and density functional theory

Distinct anti and syn isomers of the bis(mu (2)-acetophenoniminato)-bis(tri carbonyliron) obtained from iron dodecacarbonyl and 1,4-dimethyl-1,4-diphen yl-2,3-diazabuta-1,3-diene by symmetric cleavage of the azine have been com pared in terms of molecular deviations from symmetry. The study was carried out by the analysis of intra- and intermolecular close contacts in crystal s, quantum chemical DFT calculations for the isolated molecules and by NMR in solution. In the crystalline state the intramolecular contacts and also the symmetry perturbations were more strongly expressed in the syn form as compared with anti, and the same relation was perceived in the DFT-optimize d single molecules. However, in solution only symmetric conformations were observed for both isomers anti and syn by H-1 and C-13 NMR at room temperat ure and at -70 degreesC. (C) 2001 Elsevier Science B.V. All rights reserved .