Titanium binuclear

Mono-Cp titanium binuclear complexes with trisiloxane bridges have been synthesized. In the presence of MMAO, these complexes initiate the polymerizations of ethylene and styrene.938... 

Another broad class of compounds are the bridged carbene complexes. These compounds contain two identical or two different metal centers with the carbene centers bonded to both of the metal atoms in a bridging relationship. However, these binuclear complexes generally do not show classical carbene reactivity and will therefore not be discussed further, except to mention briefly the special case of the titanium-aluminum complex (3) developed by Tebbe and Grubbs and their coworkers.101 This, and related complexes, has proven to be particularly useful in organic synthesis, although its principal importance is in reactions other than cyclopropanations. 

Figure 6C.1. Proposed preferred transition state for the asymmetric oxidation of phenyl methyl sulfide with binuclear titanium(peroxide)-taitrate complex.

Binding energy, pentacarbonyliron, 6, 3 Binuclear complexes bis-Cp titanium halides, 4, 522 with Ni-M and Ni-C cr-bonds heterometallic clusters, 8, 115 homometallic clusters, 8, 111 Binuclear dicarbonyl(cyclopentadienyl)hydridoiron complexes, with rand C5 ligands, 6, 178 Binuclear iridium hydrides, characteristics, 7, 410 Binuclear monoindenyl complexes, with Ti(IV), 4, 397 Binuclear nickel(I) carbonyl complexes, characteristics, 8, 13 Binuclear osmium compounds, with hydrocarbon bridges without M-M bonds, 6, 619... 

Dimethylantimony chloride, preparation, 3, 914 2,5-Dimethylazaferrocene, preparation, 6, 209-210 iV,iV-Dimethylbenzylamines, in cobalt(III) complexes, 7, 23 Dimethyl binuclear titanium compounds, preparation,... 

Amongst some specific reactions used in regioselective syntheses, we note the cyclometallation processes [Sec. 2.2.5.1, reaction (2.8) Sec. 3.1.1.2, reactions (3.40)-(3.44) Sec. 3.3.2.3, reactions (3.226)-(3.228)]. In this respect, we note that C,N-donor ligands form, depending on the nature of Lewis acids, two types of complexes. In the case of immediate interaction (4.35) of azomethines 859 with titanium or tin tetrachlorides (MC14), the molecular complexes with M—N bond 860 [101] were obtained (route A), while the cyclometallation reaction with the use of palladium diacetate leads to binuclear chelates 861, in which the Pd — N, C metal-cycles are formed (4.35) [11,114-116] ... 

In the same year, Fujita s group63 reported the asymmetric oxidation of aryl methyl sulfide by hydroperoxides (TBHP, CHP) and an optically active catalyst formed by a Schiff base-oxovanadium(IV) complex 32, giving (S)-sulfoxides in low ee (up to 40%) (Fig. 4). Later, they developed64 a more promising approach using 33, a binuclear Schiff base-titanium(IV) complex (4 mol% equiv) to catalyze the asymmetric oxidation of methyl phenyl sulfide by trityl hydroperoxide in methanol at 0 °C. The (ft)-methyl phenyl sulfoxide was obtained with 60% ee. 

The nature of the cocatalyst in the Ziegler-Natta systems exerts a significant effect on the polymerization rate and isotacticity of the polymer product Interesting data were obtained by Keii et al. when the cocatalyst was changed during polymerization. The pronounced effect of the cocatalyst is the basis of the concept on the bimetallic composition of ACg according to which the latter are represented, for example, as binuclear complexes including titanium and aluminium. 

Metal chloride complexes (59) with structures analogous to that of the samarium complex (50) have been obtained by the reaction of (57) with titanium or zirconium tetrachlorides via elimination of LiCl. Equimolar reaction of (57) and CrCl2(thf)2 has been shown to yield binuclear chromium complex (60), whilst reaction with a twofold excess of CrCl2(thf)2 affords a partially substituted tetranuclear complex (61). ... 

The dimethyl binuclear titanium compounds [TiMe(/x-OR)(ft3-tbop)]2 (R = Me, Et) tbop = 2,2 -thiobis[4-(l,l,3,3-tetramethylbutyl)phenoxo] are prepared by reaction of the alkoxo complexes[Ti(OR)(/x-OR)(ft3-tbop)]2... 

A series of mono-Gp phosphinimido mononuclear and binuclear titanium complexes have been obtained by reactions of Cp TiCl3 with trimethylsilyliminophosphines by a dehalosilylation (Scheme 242). The molecular structures of some of these complexes have been determined by X-ray diffraction.649... 

Reaction of the Cp-amidinato imido titanium complexes Cp Ti[MeC(NPr1)2](NR) (R = But, 2,6-C6H3Me2) with C02 proceed via initial cycloaddition reactions to give N-O-carbamato complexes. The Buc derivative does not react with an excess of C02 and it undergoes a retrocyclization process with the formation of BuNCO and the binuclear fi-oxo compound Cp Ti[MeC(NPr1)2] 2(/i-0). The aryl derivatives exhibit a double CO2 insertion process to give Cp Ti[MeC(NPri)2][0(C0)N(Ar)(C0)0] (Scheme 248).661... 

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