CATALYTIC CARBON-CARBON AND CARBON-HYDROGEN BOND CLEAVAGE IN LOWER ALKANES - LOW-TEMPERATURE HYDROXYLATIONS AND HYDROXYCARBONYLATIONS WITH DIOXYGEN AS THE OXIDANT

摘要

RhCl3, in the presence of several equivalents of Cl- and I- ions, catalyzed the direct formation of methanol and acetic acid from methane, carbon monoxide, and dioxygen at 80-85 degrees C in a 6:1 mixture of perfluorobutyric acid and water (approximate turnover rate: 2.9/h based on Rh). It was possible to selectively form either methanol or acetic acid by a simple change in the solvent system. As might be anticipated, ethane was more reactive than methane, and under similar reaction conditions formed methanol, ethanol, and acetic acid (approximate turnover rate: 7.5/h based on Rh). For both methane and ethane, the product alcohols were less reactive than the starting alkanes. Methyl iodide was also less reactive than methane. Most significantly, for ethane and higher alkanes products derived from C-C cleavage dominated over those derived from C-H cleavage on a per bond basis. Indeed, C-C cleavage products were virtually all that were observed with butane, isopentane, and 2,3-dimethylbutane. While the mechanism of the C-H and C-C cleavage steps remains to be elucidated, preliminary indications are that outer-sphere electron transfer or bond homolysis resulting in the formation of alkyl radicals did not occur.