Efficient Synthesis, Redox Characteristics, and Electronic Structure of a Tetravalent Tris(cyclopentadienyl)cerium Alkoxide Complex

The complex Cp3Ce(O-i-Pr) (Cp = η5-C5H6) can be efficiently prepared from cerium tetrakis(isopropoxide) and Me3SnCp. It is shown to be a genuine Ce(IV) complex by 1H/13C NMR, elemental analysis, and cyclic voltammetry/controlled potential coulometry in Bu4N+BF4~/THF. The latter data indicate that Cp3Ce(O-i-Pr) is a relatively strong oxidizing agent (E1/2-+0.32 vs SSCE) and that one-electron reduction is both electrochemically and chemically reversible. Electronic structure calculations at the nonrelativistic Xα-DVM level suggest nonnegligible Ce-Cp f orbital covalency and yield transition state ionization energies in good agreement with He I/He II photoelectron spectra. There are substantial differences in redox properties and metal-ligand bonding between Cp3Ce(O-i-Pr) and the other known tetravalent cerium organometallic complex Ce(C8H8)2.