QUANTUM-MECHANICAL AND MOLECULAR MECHANICS CONFORMATIONAL-ANALYSIS OF1,5-CYCLOOCTADIENE

The 1,5-cyclooctadiene (COD) molecule can easily form complexes with t ransition metals with the molecular structure of various of these comp lexes being proposed with the aid of X-ray diffraction methods. The fa ct that the complexes exhibit weak metal-GOD bonds makes it very impor tant in inorganic synthesis and catalysis. In this work the potential energy surface (PES) for the GOD molecule was comprehensively investig ated first with molecular mechanics (casing the MM3 force field); and, in a second stage, at the ab initio Hartree-Fock level of theory empl oying the 3-21G, 6-31G, and 6-31G* basis sets and also including elec tron correlation effects at the Moller-Plesset second-order perturbati on theory level. This work revealed that there are three distinct conf ormers of the COD molecule with the predicted lowest energy conformati on being in agreement with the proposed structure based on experimenta l electron diffraction data. (C) 1997 by John Wiley & Sons, Inc.