How well does the Hartree–Fock model predict equilibrium geometries of transition metal complexes? Large-scale LCAO–SCF studies on ferrocene and decamethylferrocene

Abstract

Large scale ab initio LCAO–SCF calculations performed on ferrocene show that the Hartree–Fock model is unable to account for the experimentally observed metal to ring distance. The present results, using basis sets of better than triple zeta quality, show that both the equilibrium geometry and the orbital energies have converged already at the double zeta level (metal-ring distance;1.89 Å, i.e., 15% larger than the experimental value of 1.65 Å). A comparative calculation on decamethylferrocene yields essentially the same results. These findings raise some doubts as to the adequacy of the Hartree–Fock model for predictions of equilibrium geometries of transition metal complexes in general.