Enhancing Isolated Ti(Ⅳ) Framework Sites in HMS

Ti-HMS materials were prepared by grafting titanocene onto the inner walls of hexagonal mesoporous silica (HMS). The materials were characterized via powder X-ray diffraction, N2 adsorption-desorption isotherms, diffuse reflectance UV-Vis spectroscopy, and thermo-gravimetric analysis. The template of HMS was removed by calcination,ethanol-extraction, and ethanol-extraction followed by hydrolysis. The available grafting sites of OH groups depend on the different template removal methods of HMS. Ethanol-extraction followed by hydrolysis favors site-isolated Ti atoms in HMS. The catalytic performances of Ti-HMS materials were tested in the oxidation of 4-tert-butyltoluene with aqueous hydrogen peroxide. Ti-HMS prepared from HMS via the processing of ethanol-extraction followed by hydrolysis as support gave a maximum conversion of 7. 5% and a complete selectivity to 4-tert-butyl-benzaldehyde, and showed a higher activity compared with those prepared by calcination and ethanol-extraction.     

手性恶唑啉—Ti（Ⅳ）配合物催化硫醚的不对称氧化反应研究

设计合成了系列恶唑啉－Ti(O^iPr)4配合物催化剂，首次成功地用这类催化剂催化一系列硫醚的不对称氧化，获得了e.e。值为70％－96％的亚砜；考察了溶剂、催化剂用量、抗衡离子等因素对反应的影响。     

Catalytic oxidation of 4-tert-butyltoluene over Ti-MCM-41

The surface-grafted titanium MCM-41 materials were prepared by anchoring titanocene onto the inner walls of MCM-41. The materials were characterized by powder X-ray diffraction (XRD), N2 adsorption-desorption isotherm and diffuse reflectance UV-visible (UV-vis) spectroscopies. The catalytic properties of Ti-MCM-41 were tested in oxidation of 4-tert-butyltoluene with tert-butylhydroperoxide (TBHP) in liquid phase. MCM-41 with loading 4.8 mol% Ti gave the maximal conversions of 23.6% of 4-tert-butyltoluene with a complete selectivity to 4-tert-butylbenzaldehyde.     

Oxidation of methyl phenyl sulfide with hydrogen peroxide catalyzed by Ti(IV)-substituted heteropolytungstate

Alkylammonium salts of Ti(IV)-substituted heteropolytungstate, PW₁₁TiO ₁₀ ⁵⁻ , catalyze the oxidation of methyl phenyl sulfide with hydrogen peroxide. The yield of the corresponding sulfoxide and sulfone is practically quantitative. A³¹P NMR study confirms the formation and reactivity of the PW₁₁O₃₉TiO ₂ ⁵⁻ peroxo complex in organic media.     

Ion pairing in Ti(IV) trisamidotriazacyclononane compounds

[Ti[N(Ph)SiMe2]3-tacn]X complexes (X = Cl, 1; I, 2; PF6, 3; BPh4, 4) were studied by NMR and electron absorption and emission methods, which showed that these compounds exist in bromobenzene and dichloromethane solutions as ion pairs. The significant modifications observed in the proton resonances of tacn in C6D5Br, which follow the sequence BPh(4-) > or = PF(6-) > or = I- approximately Cl-, are a qualitative indication of the strength of the interactions that depend on the anion. The reaction of 2 with LiNMe2 led to [Ti(NPh)[NPh(SiMe2)]2-tacn], 5, that forms upon attack of Me2N- at one SiMe2 group. The formation of 5 is discussed on the basis of the interactions identified in solution.     

Ti(IV)-centered dynamic interconversion between Pd(II), Ti(IV)-containing ring and cage molecules

Heteronuclear, supramolecular ring and cage complexes have been constructed from a pyridyl catechol ligand, TiO(acac)2, and PdCl2(CH3CN)2. These two complexes are quantitatively interconvertible, in which Ti4+-centered coordination changes take place between a well-known Ti(catecholato)3 and a newly established TiH(catecholato)2(acetylacetonato) structures. The Ti4+-centered structural changes arise from the changes in the component fraction and basicity condition.     

Aqueous Ti(IV)-catalyzed Diels-Alder reaction

The aqueous Diels-Alder reaction of 1,3-cyclohexadiene with 1,4-benzoquinone was compared and contrasted to the same reaction catalyzed with Flextyl P, a novel Ti(IV) performance catalyst. The catalyst improved conversion by 22% versus the uncatalyzed reaction and represents a rare example of a Ti(IV) catalyzed Diels-Alder reaction in water.     

Analytical applications of Zr(IV) and Ti(IV) arsenophosphates as ion-exchangers

The distribution of 27 metal ions between zirconium and titanium arsenophosphate and demineralized water, perchloric acid and nitric acid has been studied. On the basis of the results, several binary and ternary separations can be designed. The data have been used in application of these materials to the analysis of certain alloys and rocks.     

Reconsideration of serum Ti(IV) transport: albumin and transferrin trafficking of Ti(IV) and its complexes

The trafficking of titanium(IV) by human serum transferrin (HsTf) has been implicated in the physiology of this hydrolysis-prone metal. The current work broadens to include the further interactions of Ti(IV) in serum that bear on this model. Ti2HsTf (2 equiv) binds the transferrin receptor TfR1 with Kd1 = 6.3 +/- 0.4 nM and Kd2 = 410 +/- 150 nM, values that are the tightest yet measured for a metal other than iron but weaker than the corresponding ones for Fe2HsTf due to both slightly slower on rates and slightly faster off rates. Comparing the affinities of metals for HsTf with the affinities of the resulting M2HsTf species for TfR1, we speculate that the formation of an M2HsTf complex of high affinity may predict a lobe-closed conformation that leads to a favorable interaction with TfR1. Human serum albumin (HSA), an important serum competitor for metal binding, can bind up to 20 equiv of Ti(IV) supplied in several forms. With some ligands, Ti(IV) may bind to the N-terminal metal binding site of albumin, forming a ternary complex. However, the dominant type of HSA binding is via Ti(IV) in complex form, probably at surface sites. Notably, HSA greatly stabilizes the titanocene moiety of the drug candidate Cp2TiCl2 with respect to hydrolysis and precipitation. HSA binds Ti(IV) citrate supplied as a hydrolyzed or unhydrolyzed source, with 1 equiv of citrate remaining bound. Titanium(IV) monocitrate neither competes with the binding of reporter molecules known to dock at canonical drug sites I or II nor binds at the N-terminus. HsTf outcompetes HSA for soluble Ti(IV) in a direct competition, but once bound to albumin, the transfer of Ti(IV) from HSA to HsTf is quite slow. Each of these findings has implications for the metabolism of Ti(IV) in human serum.     

Oxovanadium(IV) and copper(II) complexes of 1,2-diaminocyclohexane based ligand encapsulated in zeolite-Y for the catalytic oxidation of styrene, cyclohexene and cyclohexane

N,N′-Bis(salicylidene)cyclohexane-1,2-diamine (H₂sal-dach) reacts with oxovanadium(IV) and copper(II) exchanged zeolite-Y in refluxing methanol to yield the corresponding zeolite-Y encapsulated metal complexes, abbreviated herein as [VO(sal-dach)]-Y and [Cu(sal-dach)]-Y. Spectroscopic studies (IR, electronic and ¹H NMR), thermal analysis, scanning electron micrographs (SEM) and X-ray diffraction patterns have been used to characterise these complexes. These encapsulated complexes catalyse the oxidation, by H₂O₂, of styrene, cyclohexene and cyclohexane efficiently in good yield. Under the optimized conditions, the oxidation of styrene catalysed by [VO(sal-dach)]-Y and [Cu(sal-dach)]-Y gave 94.6 and 21.7% conversion, respectively, where styreneoxide, benzaldehyde, benzoic acid, 1-phenylethane-1,2-diol and phenylacetaldehyde being the major products. Oxidation of cyclohexene catalysed by these complexes gave cyclohexeneoxide, 2-cyclohexene-1-ol, cyclohexane-1,2-diol and 2-cyclohexene-1-one as major products. Conversion of cyclohexene achieved was 86.6% with [VO(sal-dach)]-Y and 18.1% with [Cu(sal-dach)]-Y. A maximum of 78.1% conversion of cyclohexane catalysed by [Cu(sal-dach)]-Y and only 21.0% conversion by [VO(sal-dach)]-Y with major reaction products of cyclohexanone, cyclohexanol and cyclohexane-1,2-diol have been obtained.     

Assigning Possible Ion Exchange Sites in Cerium(IV) Antimonates

Empirical formulae, based upon thermo-analytical investigations, have been assigned for different cerium(IV) antimonate samples prepared under varying conditions of precipitation. Equilibria and apparent Na⁺-capacity measurements at different pH values were carried out to throw more light on their sorption behavior. From the general curve shape analysis of the capacity-pH curves, the possible ion exchange site acidity and site group concentration were characterized. The samples showed almost bifunctional cation exchange behavior. The results obtained are discussed in detail referring to some conclusions.