Monomeric peroxo titanate coordinated with cyclohexanediaminetetraacetate: Towards the active oxygen species of the Ti(IV) site hosted in the titanium silicalite catalyst TS-1
- 化学化工－已发表论文 
Hexadentate chelated trans-1,2-cyclohexanediaminetetraacetato titanate(IV) was used as a model of the Ti(IV) species in the constrained environment of TS-1 (H(4)cdta = trans-1,2-cyclohexanediaminetetraacetic acid, C14H22O8N2; TS, titanium silicalite). Several complexes were isolated and well characterized, including (Ti(cdta)(H2O)]center dot 2H(2)O (1), Na-2[Ti(O-2)(cdta)]center dot H2O (2) and (NH4)(2)[TiO(cdta)](.)center dot 1.5H(2)O (3). Octadentate cdta peroxo titanate(IV) (2) is obtained quantitatively from the reaction of the hydrated titanium cdta complex 1 with hydrogen peroxide. The bond distances between O-O and Ti-(O-2) are 1.464(3) and 1.908(2)A, respectively. Transformation of the peroxo titanium(IV) complex with excess H(4)cdta and heating results in the formation of an interesting oxotitanate in H2O-H2O2 solution. The catalytic activity of 2 was studied for phenol hydroxylation using 30% H2O2, and this was monitored by H-1 and C-13 NMR techniques. The main product of the reaction is catechol. (C) 2012 Elsevier Ltd. All rights reserved.