Oxygen−Oxygen Bond Homolysis in a Novel Titanium(IV) Alkylperoxide Complex, Cp₂Ti(OO^tBu)Cl

Abstract

Cp2TiCl2 reacts with NaOOtBu to form the new titanium peroxide complex, Cp2Ti(OOtBu)Cl (1), which has been characterized both in solution and in the solid state. This complex is surprisingly unreactive towards olefins and phosphines, as it does not directly transfer an oxygen atom. Instead, decomposition occurs via initial homolysis of the oxygen-oxygen bond, yielding a tert-butoxyl radical. Decomposition of 1 in the presence of phosphines yields either phosphine oxides (e.g., OPPh3) or phosphinites (e.g., tBuOPEt2), products that result from tBuO* + PR3. O-O bond homolysis is surprising because the Ti(IV) center is d0 and cannot be oxidized, where all previous clear examples of homolytic cleavage of metal peroxide complexes are facilitated by oxidation of the metal center.

Synthesis and Reactivity of Oxo-Peroxo-Vanadium(V) Bipyridine Compounds

“…The V V O(O 2 ) would then be reduced by another equivalent of V IV O(OH) to form more V V O 2 . This reduction of V V O(O 2 ) is likely to occur via formation of vanadium-hydroperoxo intermediates, which may generate small amounts of reactive organic species via homolysis of a VO-OH bond24 or oxidation of THF. However, such a pathway does not explain the induction period or lack of autoxidation of V IV O(OH) in less oxidizable solvents.…”

Reaction of a monomeric titanium hydride with dioxygen does not produce a stable titanium hydroperoxide

“…It might be expected that if formed, a Ti-OOH species might rapidly undergo decomposition at room temperature. In support of this hypothesis a recently reported tert-butyl peroxide of Ti has been isolated and found to be stable only at temperatures below −20°C [21,22].…”

10 Titanium, zirconium and hafnium

“…The other product, Cp 2 Ti(Oؒ)Cl, is unexpectedly stable and does not go on to oxidize PEt 3 to Et 3 PO. 59 A comparison has been made of ab initio and DFT methods for studying chain propagation and chain termination processes with Group 4 polymerization catalysts, starting with the ansa-bis(cyclopentadienyl)zirconium catalyst. 60 Highly active cyclopentadienyl-arene titanium catalysts have been used to effect the catalytic trimerization of ethane.…”