The molecular structure of ferrocene

The vertical iron–cyclopentadienyl distance in ferrocene has been determined using ab initio coupled-cluster theory. At the CCSD level, a TZV2P basis set yields a metal–ligand distance of 1.664 Å with all 96 electrons correlated and 1.672 Å with 66 electrons correlated. With 66 electrons correlated at the CCSD(T) level the equilibrium distance is 1.660 Å, in agreement with experiment (1.66 Å).