Titanasilsesquioxanes

A series of titanasilsesquioxane alkoxides, including [R7Si70i2Ti0zPr] (107, R = C-C5H9 108, c-CfiHn = 1,2) and [Cy7Si70i2Ti(p-0Me)(Me0H)]2 (109) were published by Crocker and co-workers. " Treatment of Cy7Si70i2Ti(0Pr) (108) with methanol affords the six-coordinate titanasilsesquioxane dimer [Cy7Si70i2 Ti(p-OMe)(MeOH)]2 (109), which was structurally characterized. The monomer/ dimer equilibrium of 108 and the formation of 109 are depicted in Scheme 34. " ... 

Crocker and co-workers reported the use of 108 as starting material in the preparation of monomeric titanasilsesquioxane phenoxide derivatives. Heating of the isopropoxide precursor with phenols resulted in elimination of i-PrOH and formation of the corresponding titanium phenoxide complexes (Scheme 36). 

Crocker, M., Herold, R.H.M. (Shell Oil Company, USA) (1998) Preparation of oxirane compounds with titanasilsesquioxane catalysts. US PCT 97/783965. 

Dibenzyl complexes with calcium, strontium, barium, 2, 120 with Ti(IV), 4, 343, 4, 349 with Zr(IV), 4, 783, 4, 785-786 with Zr(IV) mono-Cp complexes, 4, 833 Dibenzylgallium azides, for semiconductor growth, 12, 17 Dibenzyl imido complexes, with Ti(IV), 4, 352-353 Dibenzyl phosphoranimino carbenes, with Zr(IV), 4, 798 Dibenzyl titanasilsesquioxanes, synthesis, 4, 493 Dibenzyo-tetramethyltetraaza[14]-annulenes, with Zr(IV),... 

Figure 28.5. Catalytic cycle in the epoxidation of alkenes by cubic titanasilsesquioxanes (represented by (=SiO)3TiOR).

Substitution at the silicon atoms has been investigated with the cubic titanasilsesquioxanes 1 and 3 as representative examples. If Cp substitution takes place, then in most cases it is with concomitant degradation of the core... 

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