Titanium theoretical studies

The theoretical studies " have been focused on TiSi2. Some attempts, with use of high-symmetry crystal structures, have been made to understand some of the other titanium silicides. This paper deals vith Ti,5Si.3. Because of the crucial interplay between structure and bonding we have studied the proposed stable low-symmetry crystal structure. This will give a better picture of the electronic structure and the bonding properties in this system. An investigation of seven members in the Ti-Si system will be presented in a future publication. ... 

A theoretical study of structure and reactivity of titanium chlorides 269... 

The one-pot condensation of an ester enolate with an imine is a very powerful synthetic procedure toward azetidin-2-ones (Equation 183). Various types of esters and imines can be utilized. Although in the vast majority the reactions have been mediated by lithium, various other metals mediate the reaction as well. Some examples include zinc, aluminium, tin, boron, indium, and titanium <1996MI119>. Theoretical studies on these reactions have been reviewed <1998JCC1826>. 

Poster 10. Young-Ah Jeon, Yang-Soo Kim and Kwangsoo No (Korea Advanced Institute of Science and Technology, Korea Basic Science Institute) Theoretical Study of Lithium Intercalation in Titanium Sulfides and Titanium Oxides... 

The work of Davis was, however, unable to distinguish which oxygen was attacked on the titanium peroxo complex when the alkene co-ordinates. Therefore, Neurock and Manzer conducted a theoretical study of the mechanism of alkene epoxidation using TS-1 with aqueous hydrogen peroxide.32 The workers concluded that their calculations to predict both the structure and relative bands in the IR spectra for TS-1 were in good agreement with experimental data. The calculations indicated that the oxygen closest to the titanium centre was the active site for alkene attack. The result was the direct formation of... 

THEORETICAL STUDY OF ADSORPTION OF SILVER DIMER ON TITANIUM DIOXIDE SURFACE COMPARISON OF CLUSTER AND PERIODIC MODELS... 

Theoretical study by DFT calculations for the insertion process of ethylene into the titanium-carbon chain for contact ion pair systems of the type [L1L2TiCH3(/x-CH3)B(C6F5)3], where Li and L2 are Gp, NPH3, and other ligands, has been performed.322... 

E. Karlsen, K. Schdffel, Titanium silicalite catalyzed epoxidation of ethylene with hydrogen peroxide. A theoretical study, Catal. Today 32 (1996) 107. 

Under kinetic control, the reactions of prochiral aldehydes with Z-enolates generally lead to syn aldols, while E-enolates lead to anti aldols. The presence of bulky R groups on the enolates, however, may alter these selectivities. The highest diastereoselectivities are observed with boron or titanium enolates. These selectivity trends are interpreted by a concerted cyclic mechanism. The favored transition state resembles a distorted chair, in line with the Zimmermann-Traxler proposals [57, 160, 253] (Figure 6.70). This model has been supported by theoretical studies [9, 40, 41, 125, 1249], Transition states analogous to C2 and C4 (Figure 6.70) are destabilized by 1,3-ecIipsing interactions between the C-R, M-L and C-R bonds, so that models Ci and C3 are more favorable. For the sake of simplification, only the reaction on one face of the enolates is shown in these models, but enolate face selectivity will be discussed later. In some cases, boatlike transition-state models are invoked to interpret selectivity inversions [401, 402, 666], Moreover, Heathcock and coworkers [105] obtained evidence for the influence of an excess of n-B BOTf on the stereoselectivity of the aldol reactions of Z-enolates. In such reactions, anti aldols can be formed preferentially (see bdow). 

Several complexes combining q2 and q3 - BH4 ligands in the coordination sphere have been reported with TP, TET, TBP and OCT geometries (Scheme 9). It is worth comparing the tetrahydrobrate coordination modes found in a series of M(BH4)3L2 (M = Sc, Ti, V) complexes. Despite the three compounds exhibiting TBP structures, vanadium shows the three BH4 coordinated q2, scandium prefers two q3 and one q2, and titanium prefers two q2 and one q3-BH4 ligands. These series have been theoretically studied in order to discuss the importance of electronic effects as a main factor... 

Kulinkovich himself proposed that the dialkoxytitanacyclopropanes as the key intermediate in the Kulinkovich cyclopropanation. Extensive theoretical study on mechanism was published in 2001. Eisch also provided detailed exploration of the mechanism for the Kulinkovich reaction in 2003. In 2007, Kulinkovich proposed a modified ate complex mechanism for titanium-mediated cyclopropanation of carboxylic esters with Grignard reagents. 

Froese, R. D. J. Musaev, D. G Morokuma, K. Theoretical studies of the factors controlling insertion barriers for olefin polymerization by the titanium-chelating bridged catalysts. A search for more active new catalysts. Organometallics 1999,18, 373-379. 

Minieri, G Corradini, R Guerra, G ZambeUi, A. Cavallo, L. A theoretical study of syndiospecific styrene polymerization with Cp-based and Cp-free titanium catalysts. 2. Mechanism of chain-end stereocontrol. Macromolecules 2001, 34,5379-5385. 

Fujimoto H, Yamasaki T, Mizutani H, Koga N (1985) A theoretical study of olefin insertions into titanium arbon and litanium ydrogen bonds. An analysis by paired interacting orbitals. J Am Chem Soc 107(22) 6157 161... 

The titaniuin oxides are of considerable technological interest, so different theoretical studies of electronic and atomic structure and properties have been performed both for Ti02 [100,323,596,597] and Ti20s [598,599] crystals. We are not aware of the existence of the electronic-structure calculations of TiO. The available publications focus attention primarily on description of the band structure and phase stabihty of titanium oxides and restrict the discussion of the nature of chemical bonding in these compounds to an analysis of Mulhken atomic charges and overlap populations. 

Theoretical studies mainly predict equal contributions of the 3d orbitals of the two nearest titanium ions (Fig. 10.3) into the wavefunction of the F center [729,730,734]. According to DFT calculations on a cubic phase of SrTiO perovskite [730], the Mulhken electron charge of 1.1 1.3 is localized in the neutral O vacancy (depending on the superceU size), and 0.6+1.8 are equally divided by the two nearest Ti ions if we consider the F center. This result does not confirm the formal conclusions that the F center is supposed to have released both electrons, whereas the nearest titanium... 

Titanium dioxide (in rutile and anatase structures) is the most investigated crystalline system in the surface science of metal oxides. The review article [783] summarizes the results of experimental and theoretical studies of titanium dioxide (bulk and surface) made up to 2002 inclusive. The information about calculations of the surface reconstruction, surface defects and growth of metals on Ti02 is also included. The results of the later theoretical studies of rntHe surfaces can be found in [784-795] and references therein. In the majority of the calculations the slab model was used for the study of periodic surface structures. 

Kholdeeva, O., Trubitsina, T, Maksimovskaya, R., et al. (2004). First Isolated Active Titanium Peroxo Complex Characterization and Theoretical Study, Inorg. Chem., 43, pp. 2284-2292. 

The same theoretical study shows that hoth chain propagation and p-hydrogen transfer responsible for the alkene liberation are favored decisively by the titanium d orbitals. 

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