Relativistic effects in gas-phase ion chemistry: an experimentalist's view.

Gas-phase experiments provide information which, in conjunction with results from electronic structure calculations, help to unravel the critical role relativistic effects play in many areas of transition-metal chemistry. Examples include the thermochemical data of gold halides in different oxidation states, the fascinating structural properties of gold(I) complexes, the dramatic effects of ligands on the ionization energy of gold, or the binding in cationic metal-carbene complexes. Furthermore, in the context of methane functionalization, special emphasis is paid to the chemistry of cationic metal-carbene complexes, and at uncovering the mechanistic details of important carbon-heteroatom coupling reactions. It is the interplay of conducting experiments of "isolated" molecules under well-defined conditions with reliable electronic structure calculations that has considerably improved our understanding of the role relativistic effects play in the context of transition-metal chemistry, catalysis, and beyond.