Titanium complex, binuclear

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... 

The binuclear titanium complex shown in Scheme 364, supported by chiral diolate ligands, has been prepared as yellow crystals by the reaction of Cp TiCl3 with the corresponding diol in the presence of NEt3 in toluene at room temperature and its molecular structure determined by X-ray diffraction.888... 

For more examples of this type of complexes, see Section 4.05.6. The synthesis of homobinuclear and heterobi-nuclear bis-Cp titanium complexes is reviewed. The research about their activity on polymerization of cr-olefins is summarized. The mechanism about binuclear metallocene catalyst is also discussed in this chapter.1079... 

The synthesis of an alkylidene bridged binuclear titanium complex (Scheme 654 Section 4.05.5) has been described and its use in ethylene polymerization in the presence of MAO was investigated.1081... 

Many recent investigations in this field of chemistry have been directed toward the synthesis and study of diyne titanium complexes. The TiCp2 precursor compound Cp2Ti(Me3SiC2SiMe3) reacts with 1,4-disubstituted 1,3-butadiynes to give five-membered titanacyclocumulenes, the structures and stability of which depend strongly on the diyne substituents. Mononuclear or binuclear homobimetallic derivatives can be formed. For the mononuclear complexes, an equilibrium between the cyclocumulene and an alkyne structure is possible (Scheme 561). Binuclear complexes may exhibit different structural types (Scheme 562). 

The binuclear titanium complex Cp2TiCl(/x-0)TiCl(acac)2 is formed by the reaction of Gp2TiCl2 with 2 equiv. of 2,4-pentanedione in the presence of NEt3 in CH3CN at room temperature. Its molecular structure has been determined by X-ray diffraction. On activation with LiBu11, the compound catalyzes the reaction of phenylsilane with aldehydes to give O-silylation products.1531... 

The ionic fulvalene titanium complex [ CpTi(H2O) 2(/i-Ci0H8)(/i-O)]2+[OTP]2 l/2THF (Scheme 591) can be prepared as an air stable compound by the reaction of binuclear [CpTi(/i-H)]2(//-C10H8) with trifluoromethane-sulphonic acid in the presence of small amounts of water. A reaction intermediate is [TiCp(OTf)2]2(//-Ci0H8). The molecular structure of the fi-oxo aquo fulvalene complex has been confirmed by X-ray crystallography.1534... 

The structure of the catalyst has been studied by several spectroscopic methods [813], and it appears that a binuclear titanium complex 3.18 is the predominant species in solution. Tartramides 3.19 have been proposed as substitutes for dialkyl... 

Another example of a titanium complex is the binuclear titanocene complex 18 which is obtained by the insertion of titanocene dicarbonyl into the S-S bond of a fused ring compound 17, involving elimination of CO (Scheme 5)... 

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... 

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... 

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