Titanium complexes halide complex reductions

Bis(cyclopentadienyl)titanium(II) dicarbonyl complexes, preparation and reactivity, 4, 250 Bis(cyclopentadienyl)titanium(II) dinitrogen complexes, preparation and reactivity, 4, 250 Bis(cyclopentadienyl)titanium halides ligand metathesis reactions, 4, 537 olefin polymerization, 4, 538 organic reactions, 4, 540 properties, 4, 530 reductions, 4, 532 synthesis, 4, 510... 

Diamagnetic titanium(ll) arene complexes ( ) -C6H6)Ti[(ju,-X)2(AlX2)]2 (X = C1, Br, 1) (20) have been prepared by the reduction of TiX4 (X = Cl, Br, 1) with A1 in the presence of AICI3 in CeHe (equation 17). The arene ligands in these complexes are rf coordinated to the titanium, which exhibits square pyramidal coordination with four halides of... 

In general, the compounds of the Group 4 metals, such as halides and alkoxides, are well known as Lewis acids to catalyze two-electron electrophilic reactions, and their metallocenes coupled with alkylation and/or reduction agents were effective catalysts for the coordination polymerization of olefins. For the transition metal-catalyzed radical polymerization, their alkoxides, such as Ti(Oi-Pr)4, have also been employed as an additive for a better control of the products. Contrary to the common belief that the Group 4 metals rarely undergo a one-electron redox reaction under mild conditions, there have been some reports on the controlled radical polymerization catalyzed or mediated by titanium complexes, although the conflict in the mechanism between the (reverse) ATRP and OMRP is also the case with the Group 4 metal complexes. 

The complications which result from the hydrolysis of alkali metal cyanides in aqueous media may be avoided by the use of non-aqueous solvents. The one most often employed is liquid ammonia, in which derivatives of some of the lanthanides and of titanium(III) may be obtained from the metal halides and cyanide.13 By addition of potassium as reductant, complexes of cobalt(O), nickel(O), titanium(II) and titanium(III) may be prepared and a complex of zirconium(0) has been obtained in a remarkable disproportion of zirconium(III) into zirconium(IV) and zirconium(0).14 Other solvents which have been shown to be suitable for halide-cyanide exchange reactions include ethanol, methanol, tetrahydrofuran, dimethyl sulfoxide and dimethylformamide. With their aid, species of different stoichiometry from those isolated from aqueous media can sometimes be made [Hg(CN)3], for example, is obtained as its cesium salt form CsF, KCN and Hg(CN)2 in ethanol.15... 

Vinyl halides add to allylic amines in the presence of Ni(cod)2 where cod=l, 5-cyclooctodine, followed by reduction with sodium borohydride. Aryl iodides add to alkynes using a platinum complex in conjunction with a palladium catalyst. A palladium catalyst has been used alone for the same purpose, and the intramolecular addition of a arene to an aUcene was accomplished with a palladium or a GaCl3 catalyst, " AUcyl iodides add intramolecularly to aUcenes with a titanium catalyst, or to alkynes using indium metal and additives. The latter cyclization of aryl iodides to alkenes was accomplished with indium and iodine or with Sml2. " ... 

The complexes TiXMe(salen) (Scheme 24) are obtained when the dichloro parent compound TiCl2(salen) reacts with AlMe3 by further addition of OEt2 with additional formation of titanium(m) species (salen = N,N -bis(salicyli-dene)ethylenediamine). The reactivity of these compounds has been studied toward magnesium reduction, halide abstraction with SbCl5 and AgBF4, S02 insertion and hydrolysis reactions.73,74... 

Transition metal halides LmMX (L = ligand, X = halogen, m = 0, 1, 2. . . ) undergo multiple reduction with BSD. The reaction products are transition metal halides LmMX p in lower oxidation states, complexes such as LmM, or the metal itself (49). The products, LmMX p, LmM, or M can, in some cases, react further with BSD to form complexes (cf. Section VII). In this way, BSD in methylene chloride transforms titanium tetrachloride, TiCl4, to titanium dichloride which, being a very mild oxidizing agent, is incapable of further reduction (with BSD) to the metallic state (50) [Eq. (90)]. Complete reduction to the metallic state, on the other hand, has been observed... 

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