Monomeric peroxo titanate coordinated with cyclohexanediaminetetraacetate: Towards the active oxygen species of the Ti(IV) site hosted in the titanium silicalite catalyst TS-1

Terminal Titanyl Complexes of Tri- and Tetrametaphosphate: Synthesis, Structures, and Reactivity with Hydrogen Peroxide

“…The complex contains Ti–O peroxo and O–O distances of 1.795(8), 1.815(8), and 1.486(6) Å, respectively. These distances are in accord with data for related peroxotitanium­(V) complexes reported in the literature. , The identity of 3 was also confirmed by ESI-MS(−), with an m / z value of 197.95 (Figure S21 in the Supporting Information, calcd 197.89). The TiO vibration at 969 cm –1 in the IR spectrum of 1 is absent in the spectrum of 3 , and a new stretch attributed to the peroxo O–O vibration is located at 856 cm –1 (Figure S18 in the Supporting Information), consistent with a side-on η 2 coordination mode .…”

“…Dimer 1 contains a Ti•••Ti distance of 4.233(9) Å, with a titanyl TiO distance of 1.624(7) Å. While structurally characterized anionic titanium(IV) oxo complexes are rare, 20,21 the observed TiO distance in 1 agrees well with corresponding metrical parameters reported for other neutral titanium(IV) oxo complexes with distances spanning 1.61−1.68 Å. 22 The TiO distance observed in 1 is consistent with triplebond character, as predicted by the titanium and oxygen triplebond covalent radii, 23 as well as the electronic considerations associated with d 0 transition-metal oxos within tetragonal ligand fields.…”

Zeolite-Y Encapsulated Metal Picolinato Complexes as Catalyst for Oxidation of Phenol with Hydrogen Peroxide

“…Homolytic cleavage results in rapid dissociation to give catechol, regenerating the complex in the catalytic cycle. A similar kind of mechanism has been recently proposed by Modi et al and Liu et al 60,61 This step has a barrier of 8.2 and 21.3 kcal/mol for the Cu-and Co-complexes, respectively (Figure 8) and is found to be favorable by 33.3 and 34.4 kcal mol −1 for the Co-and Cu-complexes, respectively. It can be observed from Figure 8 that the formation of ML 2 * and ML 2 *S is not energetically costly in the case of Cu-complex.…”

“…An active species ML 2 *(M = Co or Cu, L = 2-pyridine carboxylate) is first generated quickly in the ML 2 –H 2 O 2 buffer solution, then the intermediate ML 2 *S is generated by coordination of phenol to M 2+ . Finally the catechol is obtained by transfer of oxygen from peroxide to phenol with the simultaneous release of H 2 O. , To establish the possible path of reactions, 10 –3 M solutions of neat cobalt and copper picolinato complexes are first dissolved separately in a minimum amount of acetonitrile and treated individually with a solution of 30% H 2 O 2 prepared in acetonitrile. Spectral changes in the electronic spectra of neat complexes on addition of hydrogen peroxide are monitored through UV–vis spectroscopy.…”

Wheel-Like Icosanuclear Peroxotitanate—A Stable Water-Soluble Catalyst for Oxygen Transfer Reactions

“…Plenty of well-defined titanium peroxo complexes (TPCs) have been isolated, which include titanium salalen, − phthalocyanines, polyoxometalate, aminocarboxylate, − citrate, − and glycollate . These complexes contain no more than four peroxo groups; some of them have exhibited high catalytic performances for various oxidations with μ-η 2 :η 2 - − , or η 2 -peroxo coordination .…”