Spectroscopy and Metal Atom Chemistry

In the burgeoning field of cryochemistry, analytical spectroscopy has played an important role in helping us to understand the reactions of high temperature chemical species in low temperature condensation reactions. Reactions with transition metal atoms in particular have become an important synthetic method in inorganic and organometallic chemistry. Fascinating new compounds for which there are often no alternative methods of synthesis have been obtained by this technique. The potential importance of the work in terms of catalytic applications and chemical synthesis is very great indeed. Commercial evaporators and cryogenic equipment in compact and convenient forms are now commonly available and it will not be very long before metal vapor synthesis will enter the category of a routine laboratory procedure. Even at this early stage ICI (UK), duPont de Nemours (USA) and Merck (Germany) have initiated exploratory programs in metal vapor chemistry and it is only a matter of time before industrial evaporation plants are modified for large-scale metal vapor synthesis. As the field develops it is becoming increasingly evident that the seemingly unrelated methods of the preparative cryochemist and the matrix spectroscopist are intimately related. In areas such as reaction intermediates, product identification, reaction pathways, thermodynamics and kinetics, reaction feasibility and yields matrix and preparative cryochemistry cover much common ground. An intelligent marriage of the two techniques is proving to be most fruitful. In this survey lecture I will attempt to place in perspective some of the contributions that matrix isolation spectroscopy can make to the field of metal atom chemistry. In order to do this effectively in a 60-minute lecture I will restrict the reaction chemistry to that of Cu, Ag, and Au atoms. The areas to be described will include the controlled aggregation of transition metal atoms, the synthesis and characterization of coordinatively unsaturated transition metal molecular fragments and elusive binuclear compounds, and reaction kinetics using the matrix isolation technique.