ABSTRACT

Platinum, palladium, nickel copper, zinc gallium, ruthenium and other transition metal atoms interacting with hydrogen, ethylene, methane, nitrogen and other small molecules are studied using ab-intio LCAO-MO-SCF calculations including extensive variational and perturbational configuration-interaction studies encompassing up to a million configurations. The calculations are done through the use of the PSHONDO-CIPSI sequence of programs that allow the calculation of many excited states simultaneously. The importance of the maximal d-shell occupation states is evident for all these metals, a fact systematically confirmed in matrix isolation experiments . Usually such  states are highly excited as compared with the ground state of the transition metal atoms but in fact become involved in the ground states for each of the transition metal-molecule complexes.

A necessary consequence is the appearance (with one exception) of multiple symmetry avoided crossings for the potential energy curves depicting the interactions of the molecules with the ground and excited states of the metal atoms. The picture derived for these calculations is quite valuable in predicting photochemical reactions and allows to obtain activation barriers, heats of reaction and the relative distribution of different reaction  products with good accuracy. This is all supported by visible–ultraviolet, infrared, electron-spin resonance and other spectroscopic techniques.