A Combined Experimental and Theoretical Study of the Versatile Reactivity of an Oxocerium(IV) Complex: Concerted vs. Reductive Addition

: A combined experimental and theoretical investigation on the cerium(IV) oxo complex [(LOEt )2 Ce(=O)(H2 O)]⋅MeC(O)NH2 (1; LOEt- =[Co(η5 -C5 H5 ){P(O)(OEt)2 }3 ]- ) demonstrates that the intermediate spin-state nature of the ground state of the cerium complex is responsible for the versatility of its reactivity towards small molecules such as CO, CO2 , SO2 , and NO. CASSCF calculations together with magnetic susceptibility measurements indicate that the ground state of the cerium complex is of multiconfigurational character and comprised of 74 % of CeIV and 26 % of CeIII . The latter is found to be responsible for its reductive addition behavior towards CO, SO2 , and NO. This is the first report to date on the influence of the multiconfigurational ground state on the reactivity of a metal-oxo complex.