Titanium complexes with mono

Reaction of the bis(allyl) titanium complexes 16 and 18 with aldehydes occurs in a step-wise fashion with intermediate formation of the corresponding mono (allyl) titanium complex containing the alcoholate derived from 4 and 5 as a ligand at the Ti atom. Then the mono(allyl)titanium complexes combine with a second molecule of the aldehyde. Both the bis (allyl) titanium complexes and the mixed mono(allyl)titanium complexes react with the aldehydes at low temperatures with high regio- and diastereoselectivities. Interestingly, control experiments revealed that for the reaction of the bis (allyl) titanium complexes with the aldehyde to occur the presence of Ti(OiPr)4 is required, and for that of the intermediate mono(allyl)titanium complexes the addition of ClTi(OiPr)3 is mandatory (vide infra). 

Scheme 1.3.16 Mechanistic scheme for the reactions of the sulfonimidoyl-substituted mono(allyl)titanium complexes with aldehydes.

Scheme 350 shows the structures of a number of mono-Cp titanium complexes with more elaborately substituted aryloxo ligands. The compounds are formed by the reaction of Cp TiCl3 with 1 equiv. of the substituted phenol in the presence of an excess of pyridine or by treatment of the lithium phenoxide with Cp TiCl3 some of them have been... 

The synthesis of mono-Gp triphenoxo titanium complexes with the chelating tris(2-hydroxyphenyl)amine and tris(2-hydroxy-3,5-dimethylbenzyl)amine has been reported (Scheme 378). Electrochemical experiments provide useful information on the reduction potentials of the compounds, from which it is clear that tris(2-hydroxy-3,5-dimethylbenzyl)amine is a stronger donor than tris(2-hydroxyphenyl)amine. The chelate ring size is also important while the reduction of complex containing tris(2-hydroxyphenyl)amine is largely reversible, the reduction of the tris(hydroxybenzyl)amine derivative is irreversible. In the presence of MAO these compounds show high activity and appreciable selectivity for the preparation of syndiotactic polystyrene.909... 

Allyltitanium compounds and Ti enolates derived from mono-Gp chloro titanium complexes with two chiral alkoxo ligands add to aldehydes with high enantioface discrimination.973... 

Attempts to synthesize Gp titanium complexes with a terminal Ti=Te moiety have met with difficulties. One of the principal factors for this is the particularly weak Ti=Te interaction. Ti=E bond energies for Cp2Ti=0 (152.6 kj mol 1) and Cp2Ti=Te (130.3 kj mol-1) have been calculated. The hydrido titanium(m) complex Gp 2TiH reacts with elemental selenium or tellurium to give mono- and diselenido and tellurido complexes. The possible involvement of monomeric terminal chalcogenides Cp 2Ti(E) (E = O, S, Se, Te) in these reactions has been probed experimentally and computationally by means of DFT calculations. 

Table 14. Mono(cyclopentadienyl)titanium and titanium complexes with nucleobases ...

The i5p-titanium(IV) atom is hard, ie, not very polarizable, and can be expected to form its most stable complexes with hard ligands, eg, fluoride, chloride, oxygen, and nitrogen. Soft or relatively polarizable ligands containing second- and third-row elements or multiple bonds should give less stable complexes. The stabihty depends on the coordination number of titanium, on whether the ligand is mono- or polydentate, and on the mechanism of the reaction used to measure stabihty. 

Mixtures of a titanium complex of saturated diols, such as TYZOR OGT, and a titanium acylate, such as bis- -butyl-bis-caproic acid titanate, do not have a yellowing or discoloring effect on white inks used to print polyolefin surfaces (506). The complexes formed by the reaction of one or two moles of diethyl citrate with TYZOR TPT have an insignificant color on their own and do not generate color with phenol-based antioxidants (507). The complexes formed by the addition of a mixture of mono- and dialkyl phosphate esters to TYZOR TBT are also low color-generating, adhesion-promoting additives for use in printing polyolefin films (508). 

SiO)3Ti-H and (=SiO)3Ti species react very easily with alcohols to give titanium tris-siloxy mono-alkoxy. Step by step, following the methods described in Scheme 2.10, it is thus possible to obtain well-defined mono-, bi- or tripodal complexes that have been characterized by chemical analysis and by chemical and spectroscopic methods such as IR and solid-state NMR ( H and C). 

We were particularly interested to see whether a regio- and stereoselective hy-droxyalkylation and amrnoalkylation of 1 and 2 with aldehydes and imino esters, perhaps by choice of the substituent X at the Ti atom, with formation of the corresponding sulfonimidoyl-substituted homoallyl alcohols 4-7 and the homoallyl amines 8-11 (Fig. 1.3.3) could be achieved. Reggelin et al. had already demonstrated that the sulfonimidoyl-substituted mono(allyl)titanium complexes 3, the... 

The lithiation of the T-configured acyclic allyl sulfoximines T-13 with n-BuLi gave the corresponding lithiated allyl sulfoximines -15 [15] which upon treatment with 1.1 equiv ofClTi(OiPr)3 at-78 to 0 °C in THF furnished the bis (allyl) titanium complexes -16, admixed with equimolar amounts of Ti(OiPr)4, in practically quantitative yields (Scheme 1.3.5) [14, 16]. Surprisingly the bis (allyl) titanium complexes -16 together with Ti(OiPr)4 and not the corresponding mono (allyl) titanium complexes were formed. 

The treatment of the lithiated allyl sulfoximines E-15 with 1.1-1.2 equiv of ClTi(NEt2)3 at -78 to 0°C in THF or ether afforded the corresponding mono (allyl) titanium complexes E-19 in practically quantitative yields (Scheme 1.3.7) [14, 16]. Similarly the Z-configured complexes Z-19 were obtained from the Z-configured allyl sulfoximines Z-15. Reaction of the titanium complexes E-19 with aldehydes at -78 °C took place at the a-position and gave the corresponding homoallyl alcohols 6 with >98% diastereoselectivity in medium to good yields (Scheme 1.3.8) [14, 16]. 

However, a more detailed study of the reaction of the mono(allyl)titanium complexes -19 carrying different alkyl groups at the double bond with different aldehydes revealed in some cases the highly diastereoselective (>98%) formation of significant amounts of the isomeric homoallyl alcohols 4 besides 6 (Table 1.3.1). 

Table 1.3.1 Reaction of the acyclic mono(allyl)titanium complexes -19 with aldehydes.

Table 1.3.3 Reaction of the cyclic mono(allyl)titanium complexes 20 (n = 1) with aldehydes.

Surprisingly, the mono (allyl) titanium complexes 19 reacted with the imino ester 23c also at the y-position with high diastereoselectivities and gave the unsaturated... 

Amidocarbonylation aldehydes, 11, 512 enamides, 11, 514 overview, 11, 511-555 Amido complexes with bis-Cp titanium, 4, 579 Group 4, surface chemistry on oxides, 12, 515 Group 5, surface chemistry on oxides, 12, 524 with molybdenum mono-Cp, 5, 556 with mono-Cp titanium(IV) alkane elimination, 4, 446 amine elimination, 4, 442 characteristics, 4, 413 via dehalosilylation reactions, 4, 448 HCL elimination, 4, 446 metathesis reactions, 4, 438 miscellaneous reactions, 4, 448 properties, 4, 437... 

Imidazolium ligands, in Rh complexes, 7, 126 Imidazolium salts iridium binding, 7, 349 in silver(I) carbene synthesis, 2, 206 Imidazol-2-ylidene carbenes, with tungsten carbonyls, 5, 678 (Imidazol-2-ylidene)gold(I) complexes, preparation, 2, 289 Imidazopyridine, in trinuclear Ru and Os clusters, 6, 727 Imidazo[l,2-a]-pyridines, iodo-substituted, in Grignard reagent preparation, 9, 37—38 Imido alkyl complexes, with tantalum, 5, 118—120 Imido-amido half-sandwich compounds, with tantalum, 5,183 /13-Imido clusters, with trinuclear Ru clusters, 6, 733 Imido complexes with bis-Gp Ti, 4, 579 with monoalkyl Ti(IV), 4, 336 with mono-Gp Ti(IV), 4, 419 with Ru half-sandwiches, 6, 519—520 with tantalum, 5, 110 with titanium(IV) dialkyls, 4, 352 with titanocenes, 4, 566 with tungsten... 

Differences between the heats of formation of titanium halide complexes with aliphatic mono- and di-sulphides (n-C3H7) TiX4 (x = 1 or 2 X = Cl or Br) and Bu S(CH2)3SBunTiBr4, in aliphatic and aromatic solvents have been attributed to weak molecular complex formation between the titanium sulphide adduct and the aromatic molecule.178 Variations in the donor ability of the aromatic solvent did not produce any corresponding variation in AH. ... 

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