INTERFACIAL COORDINATION CHEMISTRY - CONCEPTS AND RELEVANCE TO CATALYSIS PHENOMENA

The concepts of the so-called interfacial coordination chemistry (ICC) are established for complexes interacting with oxide surfaces and involving transition metal ions (TMIs). The latter can function either as probes of their own interaction with the oxide surface, as adsorption and/or catalytic sites or as precursors of oxide-supported metal particles in mono or polymetallic systems. The concepts of ICC are compared with those of solution- and solid state coordination chemistries and a general classification of the different coordination chemistry types is proposed. The analogies and differences are stressed and concern the mobility, accessibility and reactivity of the transition metal complexes. Those parameters, which are largely dependent on the bonding strength of the TMI with the oxide support and in turn on the role of the oxide support and choice of the preparation method, determine the catalytic properties. Examples of catalytic reactions will be given which involve the oligomerisation of olefins and the oxidation of methanol and can be described at a molecular level. Finally, the importance of the bonding strength of TMIs with the oxide support will be stressed in determining the preparation and properties of small supported metal particles which exhibit a strong memory effect with respect to their oxidized precursor state. The present molecular approach suggests that both the preparation and catalytic phenomena can be seen in a more predictive manner and that more effort should be devoted in the future to fundamental research in this area.