Cyclopentadienyl‐Metallverbindungen. 1. Zusammenhang zwischen Stabilität und Dissoziationsenergien von Metall‐Kohlenstoffbindungen in M 5 H 5 ‐Komplexen

The existence and thermal stability of CH( 3 ) M(σC 5 H 5 ) compounds has been viewed in terms of the bond dissociation energies involved, which predict the two‐center covalent two‐electron metal‐σC 5 H 5 bond to be ∼30 kcal/mole less stable than the parent metal‐CH 3 bond. The available experimental data are shown to be consistent with this prediction. Electron donating ligands can lead to stable two‐center diene‐type covalent metal‐C 5 H 5 bonds, even where the two‐electron σ‐bond would not be stable. With the exception of group IIB, transition metals are not capable of forming stable metal‐σC 5 H 5 complexes.