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Facile and Reversible Formation of Iron(III)–Oxo–Cerium(IV) Adducts from Nonheme Oxoiron(IV) Complexes and Cerium(III)
Author(s) -
Draksharapu Apparao,
Rasheed Waqas,
Klein Johannes E. M. N.,
Que Lawrence
Publication year - 2017
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201704322
Subject(s) - cerium , ceric ammonium nitrate , chemistry , oxidation state , adduct , solvent , redox , spin states , inorganic chemistry , medicinal chemistry , crystallography , catalysis , organic chemistry , polymer , grafting
Abstract Ceric ammonium nitrate (CAN) or Ce IV (NH 4 ) 2 (NO 3 ) 6 is often used in artificial water oxidation and generally considered to be an outer‐sphere oxidant. Herein we report the spectroscopic and crystallographic characterization of [(N4Py)Fe III ‐O‐Ce IV (OH 2 )(NO 3 ) 4 ] + ( 3 ), a complex obtained from the reaction of [(N4Py)Fe II (NCMe)] 2+ with 2 equiv CAN or [(N4Py)Fe IV =O] 2+ ( 2 ) with Ce III (NO 3 ) 3 in MeCN. Surprisingly, the formation of 3 is reversible, the position of the equilibrium being dependent on the MeCN/water ratio of the solvent. These results suggest that the Fe IV and Ce IV centers have comparable reduction potentials. Moreover, the equilibrium entails a change in iron spin state, from S =1 Fe IV in 2 to S =5/2 in 3 , which is found to be facile despite the formal spin‐forbidden nature of this process. This observation suggests that Fe IV =O complexes may avail of reaction pathways involving multiple spin states having little or no barrier.