Low-temperature hydrogen transfer and cracking catalysis in molten SbCl₃-AlCl₃

Molten SbCl₃-10 mol% AlCl₃ has been found to catalyse unusual hydrogen transfer chemistry for the polycyclic aromatic hydrocarbon, naphthalene, under extremely mild, aprotic conditions. At 130 °C and in the absence of added hydrogen gas, naphthalene is rapidly hydrogenated and isomerized in the melt to form 1-methylindene, 1-methylindane, and tetralin. The hydrogen used in the formation of these products is generated internally from the coupling of a portion of the naphthalene to form condensed aromatics such as binaphthalenes, benzofluoranthenes, and perylene. Furthermore, many of these condensed products not only undergo similar hydrogenation and isomerization, but they are also severely cracked in this medium. Under these aprotic, low-temperature reaction conditions, the redox properties of SbCl₃ are believed to play a key role in the catalytic process, the effect of added AlCl₃ being to enhance the oxidizing power of the SbCl₃ in addition to increasing the Lewis acidity of the melt.