Photochemistry of Transition‐Metal Atoms: Reactions with Molecular Hydrogen and Methane in Low‐Temperature Matrices

Reactions of metal atoms with molecular hydrogen and alkanes are prototypical of more complex systems involving metal‐mediated reactions in solution, on supports, and on surfaces. The simplicity of metal‐atom reactions makes them particularly attractive for fundamental experimental and theoretical studies. Following the first reports of H2 and CH4 activation by photoexcited metal atoms in cryogenic matrices, the behavior of a number of transition‐metal atoms in their ground and selected electronically excited states has been examined with molecular hydrogen, methane, and ethane. A wealth of structural, electronic, reactivity, and selectivity information is emerging from these studies and it is now becoming possible to recognize the controlling factors at work in these fundamental chemical reactions. In this article, some experimental results for a number of metal‐atom systems, in particular, those involving silver, copper, manganese, and iron atoms, are presented along with a discussion of the factors that are believed to be important in the understanding of the observed physical and chemical behavior.