Titanium complexes dinuclear

Titanium, tetrakis(trimethysilyl)oxy-, 3, 334 Titanium, tetranitrato-stereochemistry, 1,94 Titanium, triaquabis(oxalato)-structure, I, 78 Titanium, tris(acetylacetone)-structurc, 1,65 Titanium alkoxides oligomeric structure, 2,346 synthesis ammonia, 2, 338 Titanium chloride photographic developer, 6,99 Titanium complexes acetylacetone dinuclear, 2, 372 alkyl... 

The chiral dinuclear titanium complexes depicted in Scheme 9 have been utilized as catalysts for the DCR between Al-benzyl and Al-diphenylmethyl nitrones and... 

A few dinuclear complexes are known, in which the a-CH bond of a metal-bonded alkyl group is tj2 coordinated to another metal moiety, similar to the previously discussed dinuclear silyl complexes. In the iron complex 22 (75) both metal moieties are the same, and therefore the Fe—C distances [202.5(3) and 211.3(3) pm] can be directly compared without correction. The relative lengthening of the M—C distance of the Fe—H—C three-center bond (4.5%) is comparable to that in the silane-bridged titanium complex 13 (6.5%), corresponding to a similar stage of the oxidative addition. 

The titanium complexes are sensitive to high temperatures and the presence of oxygen or water. A more robust catalyst system is based on Cu(I) and Cu(II) amidinate complexes. Also, dinuclear copper amidinate complexes are used in the polymerization of carbodiimides. 

Addition of [o-(CH2)2C6H4]Mg(THF)2 to Cp TiCb in toluene gives the expected o-xylidene complex Cp TiCl[o-(CH2)2C6H4], However, reaction of [o-(CH2)2C6H4]Mg(THF)2 with Cp TiCb in THF leads to the dinuclear bis(diene)titanium complex (15), in which two Cp TiCl fragments bond to o-xyhdene through its exo- and... 

One possibility is that heterochiral dimerization of the ligand or the titanium complex produces an inactive catalyst this tends to sequester the minor enantiomer cf. Scheme 4.6). Another is that the catalyst is a dinuclear species, which is more reactive when homochiral. 

The reduction of the dinuclear titanium complex Ti2(COT)3 leads to the formation of [Ti2(COT)3], which probably has a triple-decker structure (11.28). ... 

Cross-metathesis of the allyl-Cp substituted titanocene dichloride leads to the formation of dinuclear titanium complexes (Scheme 12.25, M = Ti, n= 1) [33]. The composition of the reaction mixture depends on the catalyst used. Treatment of the substrate with Ru-I (3 mol%) in benzene, toluene, or dichloromethane gave a mixture of Z and E isomers in a 1 1 ratio, while application of the Ru-II catalyst resulted with the formation of the pure E isomer. 

A similar nonlinearity is seen in the ene reaction of methyl glyoxylate and a-methylstyrene (Scheme 43) (69). Thus, the reaction catalyzed by a complex in situ formed from dibromo(diisopropoxy)titanium(IV) and (/ )-binaphthol in 33% ee affords the chiral adduct in 91% ee with the same enantioselectivity as would have been obtained had enantiomerically pure binaphthol been used. Molecular weight measurements suggest the catalyst is a dinuclear titanium compound, although the structure has not been elucidated. This nonlinear effect is interpreted by the difference in the dissociation constant of the diastereomeric dimers as... 

Scheme 1.3.2. Preparation of dinuclear titanium(IV) complexes M2[l2(OCH3)2Ti2].

Bis[7i-cyclopentadienyl]bis[benzenetellurolato]titanium(IV) reacted with bis[tricarbonyl-(nitrosyl)iron] mercury to produce a Ti — Te dinuclear complex bridged by benzenetelluro-lato groups2. 

Increasing the number of electrons reduces the activation of N2, because the electrons occupy the orbitals which are bonding with respect to the NN bond, and actually stabilize it. In agreement with this prediction dinitrogen is sufficiently activated to be reduced by protonation by dinuclear complexes of titanium(II), zirco-nium(Il), niobium(III), tantalum(III), molybdenum(IV), and tungsten(IV), whereas it is not reduced by protonation by certain d -d complexes, such as those of molybdenum(O), ruthenium(II), or rhodium(I). Apparently dinuclear complexes M-N=N-M in which M has the d electronic configuration can be intermediates in dinitrogen reduction in protic media, particularly if they represent part of polynuclear complexes (vide infra). 

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