Synthesis, Structure, and Reactivity of a Tetranuclear Cerium(IV) Oxo Cluster Supported by the Klaui Tripodal Ligand [Co(5-C5H5){P(O)(OEt)2}3]-

A tetranuclear Ce-IV oxo cluster compound containing the Klaui tripodal ligand [Co((5)-C5H5){P(O)(OEt)(2)}(3)](-) (L-OEt(-)) has been synthesized and its reactions with H2O2, CO2, NO, and BrOnsted acids have been studied. The treatment of [Ce(L-OEt)(NO3)(3)] with Et4NOH in acetonitrile afforded the tetranuclear Ce-IV oxo cluster [Ce-4(L-OEt)(4)O7H2] (1) containing an adamantane-like {Ce-4((2)-O)(6)} core with a (4)-oxo ligand at the center. The reaction of 1 with H2O2 resulted in the formation of the peroxo cluster [Ce-4(L-OEt)(4)((4)-O)((2)-O-2)(4)((2)-OH)(2)] (2). The treatment of 1 with CO2 and NO led to isolation of [Ce(L-OEt)(2)(CO3)] and [Ce(L-OEt)(NO3)(3)], respectively. The protonation of 1 with HCl, ROH (R=2,4,6-trichlorophenyl), and Ph3SiOH yielded [Ce(L-OEt)Cl-3] (3), [Ce(L-OEt)(OR)(3)] (4), and [Ce(L-OEt)(OSiPh3)(3)] (5), respectively. The chloride ligands in 3 are labile and can be abstracted by silver(I) salts. The treatment of 3 with AgOTs (OTs-=tosylate) and Ag2O afforded [Ce(L-OEt)(OTs)(3)] (6) and 1, respectively. The electrochemistry of the Ce-L-OEt complexes has been studied by using cyclic voltammetry. The crystal structures of complexes 1-5 have been determined.