Homogeneous water oxidation by a di-μ-oxo dimanganese complex in the presence of Ce4+

O-2 evolution was observed upon mixing aqueous [(terpy)(H2O)Mn(O)(2)Mn(H2O)(terpy)](NO3)(3) (1, terpy = 2,2':6',6-terpyridine) with aqueous solutions of Ce4+. However, when the solution of 1 was incubated at pH 1 (by dissolving in dilute HNO3) before mixing with Ce4+, very small amounts of O-2 were observed. This observation of acid-induced deactivation suggests an explanation, both for the previously reported lack of O-2 evolution from aqueous solutions of 1 with Ce4+ as oxidant, and the present observation of low amounts of O-2 production with the very acidic Ce4+ reagent. Evidence is provided for water being the source of evolved O-2, and for the requirement of a high valent multinuclear Mn species for O-2 evolution. We test the possibility of complications in the use of ceric ammonium nitrate (CAN) in oxidation chemistry due to the presence of the oxidizable NH4+ ion. (c) 2007 Elsevier B.V. All rights reserved.