On the lack of correlation between bond lengths, dissociation energies, and force constants: the fluorine-substituted ethane homologues

Accurate ab initio coupled-cluster (CCSD) calculations have been used to evaluate systematically the E–E bond lengths, homonuclear dissociation energies, and force constants of a series of fluorine-substituted ethane homologues H3 − nFnE–EH3 − nFn (n=0–3), H3E–EF3, and H3E–EH2F (E=C, Si, Ge, Sn) in their staggered ethane-like conformations. The pronounced lack of correlation between bond lengths, dissociation energies, and force constants observed previously with E=Sn has also been found for the lighter group 14 homologues. However, each element in the group exhibits a different behavior. Attempts are made to interpret the findings in the context of electronegativity, hybridization defects, as well as negative and geminal hyperconjugation.