SYNTHESIS, STRUCTURE, AND REACTIVITY OF HOMOLEPTIC CERIUM(IV) AND CERIUM(III) ALKOXIDES

The reaction of Ce(OCtBu3)3 (1) with the following oxidants has been studied: benzoyl peroxide, BzP; di-tert-butyl peroxide, DTBP; tert-butyl peroxybenzoate, BPB; benzoquinone, Bq; 2,6-di-tert-butylbenzoquinone, DBBq. Ce(OCtBu3)3(OC(O)Ph) (2) was formed in the reaction of 1 with BzP. 1 and DTBP reacted in 1:1 ratio to generate the unstable Ce(IV) species Ce(OCtBu3)2(OtBu)2 (3). On the other hand, a 1:0.5 ratio of reactants resulted in the formation of the Ce(III) compound [Ce(OCtBu3)2(OtBu)]2 (4). The X-ray crystal structure of 4 (P2(1)/c; a = 11.783 (2) angstrom, b = 23.606 (6) angstrom, c = 11.544 (2) angstrom, beta = 95.19 (2)-degrees; 3240 independent reflections with F(o) greater-than-or-equal-to 6-sigma(F(o)); R(F) = 3.79%, R(w)(F) = 4.08%; GOF = 1.126) indicated it to be dimeric with a pseudotetrahedral geometry around each cerium atom. The interconversions between 1, 3, and 4 were examined. The reaction of 1 with BPB caused the formation of equal amounts of 2 and 3. 1 was found to react with Bq to form (tBu3CO)3CeOC6H4OCe(OCtBu3)3 (5). 5 was structurally characterized (P1BAR; a = 12.629 (4) angstrom, b = 12.736 (5) angstrom, c = 18.148 (8) angstrom, alpha = 83.60 (3)-degrees, beta = 76.83 (3)-degrees, gamma = 61.57 (3)-degrees; 6403 independent reflections with F(o) greater-than-or-equal-to 5-sigma(F(o)); R(F) = 7.70%, R(w)(F) = 7.97%; GOF = 1.466). The two cerium atoms in the molecule are bridged by a hydroquinonediolate moiety. As expected, the Ce(IV)-O distances were shorter than the Ce(III)-O bond lengths. Finally, the reaction of 1 with DBBq resulted in the formation of the radical (tBu3CO)3CeOC6H2tBu2O. (6).