THEORETICAL-STUDY OF THE BINDING OF ETHYLENE TO 2ND-ROW TRANSITION-METAL ATOMS

The binding between ethylene and all second-row transition-metal atoms from yttrium to palladium has been studied by using size-consistent correlation methods and large basis sets. The binding energy curve as a function of atomic number of the metal shows the usual characteristic minimum in the middle of the row. This minimum is mainly due to the loss of exchange when the bonds are formed. The strongest bonds are formed by the atoms to the right, for which covalent and donation-back-donation bonding is optimally mixed. The atoms to the left form metallacyclopropanes in which the C-C pi-bond is entirely broken. Comparisons are made both to the corresponding reaction with methane and to the bonding between metal cations and ethylene.