American Chemical Society
Browse

Redox and Photochemical Reactivity of Cerium(IV) Carbonate and Carboxylate Complexes Supported by a Tripodal Oxygen Ligand

Download (1.76 MB)
journal contribution
posted on 2025-01-15, 08:31 authored by Hoang-Long Pham, Xinxin Jiang, Qiaolin Yan, Yat-Ming So, Wan Chan, Herman H. Y. Sung, Ian D. Williams, Wa-Hung Leung
The protonolysis and redox reactivity of a Ce­(IV) carbonate complex supported by the Kläui tripodal ligand [(η5-C5H5)­Co­{P­(O)­(OEt)2}3] (LOEt) have been studied. Whereas treatment of [Ce­(LOEt)2(CO3)] (1) with RCO2H afforded [Ce­(LOEt)2(RCO2)2] (R = Me (2), Ph (3), 2-NO2C6H3 (4)), the reaction of 1 with PhCH2CO2H resulted in formation of a mixture of Ce­(IV) (5) and Ce­(III) (6) carboxylate species. In benzene in the dark, 5 was slowly converted into 6 via Ce­(IV)-O­(carboxylate) homolysis. Recrystallization of a mixture of 5 and 6 from hexane led to isolation of yellow crystals of 6 that were identified as [Ce­(LOEt)2(PhCH2CO2)]. Treatment of 1 with sulfamic acid, trifluoroacetamide, and trifluoromethanesulfonamide gave [Ce­(LOEt)2(SO3NH)2] (7), [Ce­(LOEt)2(CF3CONH)2] (8), and [Ce­(LOEt)2(CF3SO2NH)2] (9), respectively. The crystal structures of 2, 4, and 6–8 have been determined. H atom transfer (HAT) of 2,6-di-tert-butylphenol and 9,10-dihydroanthracene (DHA) with 1 afforded 3,3′,5,5′-tetra-tert-butyldiphenoquinone and anthracene, respectively. The oxidation of DHA with 1 under air yielded anthracene and anthraquinone. While 1 is stable in acetonitrile, it is readily reduced to a Ce­(III) species in tetrahydrofuran. In air, 1 reacted with tetrahydrofuran to produce tetrahydrofuran hydroperoxide that can reduce the Ce­(IV) carbonate rapidly. Upon irradiation with blue LED light, the Ce­(IV)-LOEt carboxylate complexes underwent facile decarboxylation via Ce–O homolysis. 1 proved to be an efficient catalyst precursor for decarboxylative oxygenation of arylacetic acids. For example, irradiation of phenylacetic acid with blue LED light in the presence of 5 mol % of 1 under air afforded benzyl alcohol and benzaldehyde in 10 and 90% yield, respectively.

History