Titanium complexes sulfur

Sulfur imides with a single NR functionality, S5NR (6.12), SeNR (6.13) (R = Oct), " SgNH (6.14), ° and S9NH (6.15) ° are obtained by a methodology similar to that which has been used for the preparation of unstable sulfur allotropes, e.g., S9 and Sio. Eor example, the metathesis reaction between the bis(cyclopentadienyl)titanium complexes 6.8-6.10 and the appropriate dichlorosulfane yields 6.14 and 6.15 (Eq. 6.4). °... 

Polysulfides of several metals can be prepared by reaction of the metals with excess sulfur in liquid NH3 (group IA metals) or by heating sulfur with the molten metal sulfide. The polysulfide ion binds to metals to form coordination compounds in which it is attached to the metal by both sulfur atoms (as a so-called bidentate ligand). One example is an unusual titanium complex containing the S52-ion that is produced by the following reaction (the use of h to denote the bonding mode of the cyclo-pentadienyl ion is explained in Chapter 16) ... 

Oxidation of the enantiotopic electron pairs at sulfur, mediated by chiral titanium complexes, to yield chiral sulfoxides with high enantiomeric excess14. 

Density functional calculations on the chain initiation reaction shown in Scheme 136 for the ethylene polymerization catalyzed by bis-alkoxo titanium complexes have been studied. Activation barriers of 6.4kcal mol-1 are found for the titanium sulfur-bridged catalysts with higher insertion barriers of 10-15 kcalmol-1 for the GH2-bridged catalysts. 

Titanium(IV) and vanadium(V) form colored complexes when treated with hydrogen peroxide in 1 M sulfuric acid. The titanium complex has an absorption maximum at 415 nm, and the vanadium complex has an absorption maximum at 455 nm. A 1.00 X 10 M solution of the titanium complex exhibits an absorbance of 0.805 at 415 nm and of 0.465 at 455 nm, while a... 

Sulfur imides with a single NR functionality, S5NR, SeNR (R=Oct), SgNH and SgNH are obtained by the metathesis reaction between the w(cyclopentadienyl)titanium complexes 71-73 and the appropriate di-... 

It is apparent that the highest ee s were obtained when the sulfur was flanked by an aryl group and a small alkyl group. This led to a simple model for prediction of absolute configuration (Figure 12). There are no exception to this rule, which may correspond to the oxidation via a binuclear titanium complex as r resented in Figure 12 with diethyl tartrate acting as a tridentate unit... 

Titanium ester enolates are not only versatile reagents for asymmetric aldol additions but also function as starters of methacrylate polymerization. A representative titanium complex 24 was characterized by crystal structure and NMR spectroscopy and reveals the monomeric O-bound enolate character. The six-coordinated titanium atom in 24 is bound to two phenolic traws-oriented oxygen atoms and two sulfur donors the remaining ligands, methyl group, and enolate moiety are c/s-configured. Upon exposure to acetone, a spontaneous aldol occurs, and the aldolate 25 thus formed was also characterized by a crystal structure. Due to its coordinative saturation, the titanium obviously does not form a chelate with the carbonyl oxygen (Scheme 3.9) [57]. 

It has been reported that the zinc hexasulfido complex, Zn(S6)(TMEDA) (TMEDA=] r,] T,N, N -tetramethylethylenediamine) acts as a sulfur transfer reagent in an analogous manner as the above-mentioned titanium polysulfido complexes. The sulfur transfer reaction between Zn(S6)(TMEDA) and TiCp2Cl2 cleanly proceeds at room temperature to afford ZnCl2(TMEDA) and TiCp2S5 together with Ss (Scheme 51) [132]. This result suggests that... 

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