HOMOGENEOUS PLATINUM(2)-CATALYZED EXCHANGE OF HYDROGEN IN POLYCYCLIC AROMATIC HYDROCARBONS AND HETEROCYCLIC MOLECULES

The homogeneous exchange of several classes of polycyclic aromatic hydrocarbons has been studied in acetic acid media in the presence of catalytic amounts of PtII salts. The rate of exchange was found to increase with decreasing double-bond localization energy for the condensed polycyclics. Polyphenyl compounds exhibit a predominance of multiple exchange whereas condensed polycyclic compounds exchange by a stepwise mechanism. Heterocyclic molecules and polycyclic hydrocarbons with delocalized double bonds exchange more slowly and inhibit exchange in benzene due to strong complex formation. The orientation of incorporation of deuterium indicates that the exchange is not acid catalyzed. Factors influencing stability of the catalyst are discussed.