Carbocations in gold chemistry

For almost a century, carbocations have remained elusive species that have attracted the attention of generations of scientists. With this historical and contemporary background, it was surprising to find that gold-substituted carbocations proved to be readily available and even exceedingly stable, open to investigation by physical methods under standard conditions. This chapter shows that polyaurated alkanes, alkenes, and arenes represent true carbocationic species with the central carbon atom engaged in hypercoordinate covalent bonding. The structures arising as the auration progresses gain in stability owing to the growing shell of metal atoms. An aurophilicity phenomenon is a very general feature of gold chemistry, and carbocation chemistry is therefore just another example for the striking influence of gold atoms in molecular and supramolecular arrays.