Homogeneous catalytic photochemical functionalization of alkanes by polyoxometalates

Progress in the last 5 years toward the activation and functionalization of alkanes, the most abundant but least reactive class of organic compounds, has been substantial. Thorough investigations of several homogeneous liquid-phase systems for alkane activation or functionalization at 25/sup 0/C have now been reported. These include organometallic systems that effect stoichiometric alkane C-H bond activation with unusual C-H cleavage selectivities (least hindered positions most reactive) and metalloporphyrin systems that effect catalytic alkane functionalization with conventional C-H cleavage selectivities (tertiary C-H most reactive). Reported here, as part of the continuing efforts to develop soluble metal oxides species as superior catalysts for energetic and synthetic transformations of interest, is a new methodology for the homogeneous liquid-phase activation and functionalization of alkanes. This chemistry involves the irradiation of heteropolytungstic acids and alkanes in acetonitrile solution. The heteropolytungstic acids, unlike all alkane-activating organometallic and metalloporphyrin species in the literature, contain no oxidizable organic structure. The very high oxidative stability of the soluble and completely inorganic polyoxometalates, recently documented for catalytic thermal epoxidation processes, is now demonstrated for catalytic photochemical organic oxidation processes.