Hydrogen peroxide is an environmentally friendly oxidizing agent but current synthetic methods are wasteful. This is a result of the high flammability of H 2 /O 2 mixtures and/or the requirement for cocatalysts. In this paper, we report the synthesis of H 2 O 2 by means of a homogeneous catalyst, which allows a safe, one-pot synthesis in water, using only H 2 and O 2 . This catalyst is capable of removing electrons from H 2 , storing them for the reduction of O 2 , and then permitting the protonation of the reduced oxygen to H 2 O 2 . The turnover number (TON) is 910 under an H 2 /O 2 (95/5) atmosphere (1.9 MPa) for 12 h at 23 °C, which is the highest of any homogeneous catalyst. Furthermore, we propose a reaction mechanism based on two crystal structures.

This paper reports the first example of CÀ H arylation of benzene under mild conditions, using H 2 as an electron source {turnover numbers (TONs) = 0.7-2.0 for 24 h}. The reaction depends on a Rh-based electron storage catalyst, and proceeds at room temperature and in aqueous solution. Furthermore, the H 2 is inactive during the radical transfer step, greatly reducing unwanted side reactions.