Photooxidation of alkane under visible light irradiation catalyzed by ruthenium complexes

Photoreactions of chloro(Me2SO)bis(bipyridine)ruthenium(II) complex and the MeCN ruthenium(II) complexes having both a tridentate ligand, such as a tris(1-pyrazolyl)methane (=tpm), a tris(1-pyrazolyl)ethane (=tpe), or a 2,6-bis(1-pyrazolyl)pyridine (=bpp), and a bidentate ligand, bipyridine, have been investigated in Me2SO, MeCN, or 1,2-dichloroethane. A ligand, such as Me2SO or MeCN, dissociated and/or substituted by a solvent molecule selectively under irradiation. Furthermore, alkane oxidation catalyzed by ruthenium complexes in the presence of 2,6-dichloropyridine N-oxide under visible light irradiation (>385 nm) has been examined. Tertiary carbon(s) of adamantane was oxidized selectively to give 1-adamantanol and 1,3-adamantanediol. It was found that dicholorobis(bipyridine)ruthenium(II) complex was also an efficient catalyst on photooxidation of adamantane in the presence of 2,6-dichloropyridine N-oxide.