Titanium tetramethyl

My own credentials are mixed. On the credit side is a refusal to predict concerted rrans-addition less impressive is a clear explanation of facile free radical loss from titanium tetramethyl complexes, shortly before evidence began to accu-mulate that such species decompose by internal or mutual abstraction. 

Oiganometallic usage is shown in the piepaiation of titanium- oi vanadium-containing catalysts foi the polymerisation of styrene or butadiene by the reaction of dimethyl sulfate with the metal chloride (145). Free-radical activity is proposed for the quaternary product from dimethylaruline and dimethyl sulfate and for the product from l,l,4,4-tetramethyl-2-tetra2ene and dimethyl sulfate (146,147). 

Sodium hydride Sodium hydrosulfite Sulfur chlorides Sulfuric acid Sulfuryl chloride Tetraethyl lead Tetramethyl lead Thionyl chloride Titanium tetrachloride Toluene diisocyanate Trichlorosilane Triethylaluminum Triethylborane Triisobutylaluminum Trimethylaluminum Trimethylchlorosilane Tripropyl aluminum Vanadium tetrachloride Vinyl trichlorosilane Zirconium tetrachloride... 

A new enantiopure, bidentate ligand (35, 45 )-2,2,5,5-tetramethyl-3,4-hexanediol [(35, 45)-186] was developed by Yamanoi and Imamoto and investigated as asymmetric inductor in the titanium-catalyzed sulfoxidation reaction with various hydroperoxides as oxygen donors (Scheme 107). The catalytically active species was then prepared in situ from Ti(OPr-/)4 and ligand (35,45)-186. The most efficient hydroperoxide in terms of enantio-selectivity turned out to be cumyl hydroperoxide (95% ee compared to 30% ee in the case of methyl p-tolyl hydroperoxide), and molecular sieves 4 A had a beneficial effect on the... 

Asymmetric pinacol coupling reactions with a stoichiometric amount of titanium salts have been observed using a combination of TiGL and chiral amines such as A,A,A,A-tetramethyl-l,2-cyclohexanediamine and 2-methoxy-methylpyrrolidine. " " In these reports, the titanium salt is considered to be TiGl2- However, the titanium salt prepared by reduction of TiGU with McsSiSiMcs has proved to be TiGL. The enantioselectivities of the reactions using the chiral amines are modest (Table 2). 

Octahedral coordination of Tiiv is also present in the titanium silicates ETS-4 and ETS-10. The structure of these materials is reported to be similar to that of zorite, and they can be described as microporous crystals with uniform pores similar in dimensions to classical small- and large-pore zeolites. In ETS-4 and ETS-10, there are two monovalent cations or one divalent cation for each Tilv ion (Kuznicki, 1989, 1990 Kuznicki et al., 1991a, 1991b, 1991c, 1993 Deeba et al., 1994). A recent report of the synthesis of ETS-10 with tetramethyl-ammonium chloride indicates a ratio of monovalent cations to Tilv of 1.6 (Valtchev et al., 1994). The acidic properties of these materials have not been reported. A material modified by the addition of Al3+ has been obtained, ETAS-10, which, after exchange with NH4 salts, exhibits acidic properties but these are due to the presence of Al3+ and not to the Tilv (Deeba et al., 1994). 

A difference in the relationship between UCV and degree of substitution x has recently been reported in connection with the use of tetramethyl orthosilicate (TMOS) as the silicon source instead of TEOS. The Ti content can be increased up to a value of 0.05 without evidence for extra-framework titanium species in the UV-visible spectra. However the UCV increases do not follow the relationship of Eq. (5) and the maximum value obtained, 5390 A3 at x = 0.05, is the... 

Abbreviations AD, asymmetric dihydroxylation BPY, 2,2 -bipyridine DMTACN, 1,4-dimethyl-l,4,7-triazacyclonane EBHP, ethylbenzene hydroperoxide ee, enantiomeric excess HAP, hydroxyapatite LDH, layered double hydroxide or hydrotalcite-type structure mCPBA, meta-chloroperbenzoic acid MTO, methyltrioxorhenium NMO, A-methylmorpholine-A-oxide OMS, octahedral molecular sieve Pc, phthalocyanine phen, 1,10-phenantroline PILC, pillared clay PBI, polybenzimidazole PI, polyimide Por, porphyrin PPNO, 4-phenylpyridine-A-oxide PS, polystyrene PVP, polyvinylpyridine SLPC, supported liquid-phase catalysis f-BuOOH, tertiary butylhydroperoxide TEMPO, 2,2,6,6-tetramethyl-l-piperdinyloxy TEOS, tetraethoxysilane TS-1, titanium silicalite 1 XPS, X-ray photoelectron spectroscopy. 

Hydrolysis and Condensation. The rate of hydrolysis of the tetraalkyl titanates is governed by the nature of the alkoxy groups. The lower titanium alkoxides, with the exception of tetramethyl titanate [992-92-7], are rapidly hydrolyzed by moist air or water, giving a series of condensed titanoxanes, (Ti— O—Ti— O—) (17). As the chain length of the alkyl group increases, the rate of hydrolysis decreases. Titanium methoxides, aryloxides, and C-10 and higher alkyl titanates are hydrolyzed much more slowly. 

The patterned amino-silica is used as a support for immobilizing a titanium constrained geometry catalyst, shown in Scheme 2. The amine sites are first reacted with chlorodimethyl-(2,3,4,5-tetramethyl-2,4-cyclopentadien-l -yl)... 

Applications The most important application sectors for metallic sodium in the USA are in the production of sodium borohydride (ca. 38%), which is used as a reducing agent, and in the manufacture of herbicides (ca. 25%). A further important sector accounting for 20% of the consumption of sodium, is the production of metals which are difficult to reduce such as uranium, thorium, zirconium, tantalum and titanium. Its utilization in the production of titanium has, however, declined of late. Tetramethyl- and tetraethyl lead... 

For the production of ethylene/l-octene copolymers, metallocenes in combination with oligomeric methylalumoxanes or other compounds are now used [31, 63]. Half-sandwich transition metal complexes such as [(tetramethyl- / -cyclopentadienyl) (A-/-butylamido)dimethylsilyl]titanium dichloride are applied to synthesize linear low-density copolymers and plastomers, called constrained geometry catalysts [31]. Ethylene and styrene can be copolymerized to products ranging from semicrystalline mbber-like elastomers to highly amorphous rigid materials at room temperature [64]. 

Indenyl-alkoxo derivatives have been employed to catalyze the syndiospecific polymerization of styrene.985 Ab initio investigations of the synthesis of the tetramethyl-Gp-propoxo dichloro titanium complex Ti[C5Me4(CH2)30]Cl2 from Ti[G5Me4(CH2)30Me]Gl3 have been reported.986... 

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