Titanocene dichloride complexes

The titanocene dichloride complexes derived from the camphor- and pinene-annulated ligands 126 and 127 were tested as enantioselective hydrogenation catalyst and using 2-phenylbutene as substrate 2-phenylbutane was obtained with ee up to 34% [148, 149]. 

HeO)2Si(CH2)3CjH5 (LU) gives an Tt -LRhlCOD) complex effective as a cyclotri-merisation catalyst, the titanocene dichloride complex on silica, after reduction, is efficient and selective for hydrogenation of alk-1-enes, while... 

In 1985, Eisch et al. isolated a cationic alkenyltitanium complex (55) by the insertion of an alkyne into the cationic Ti-C bond generated from titanocene dichloride and methylaluminum dichloride (Eq. 2) [77], Similarly, a mixture of Cp2TiCl(CH2SiMe3) and A1C13 afforded the solvent-separated ion pairs,... 

Methylenative dimerization takes place when terminal alkynes are treated with the tita-nocene/methylidene/zinc halide complex generated from titanocene dichloride and CH2(ZnI)2. The process is believed to involve the formation of a titanacyclobutene intermediate [75],... 

Other metal complexes also have promising anticancer activity. Two Ti(IV) complexes are on clinical trial, an acetylacetonate derivative (budotitane) and titanocene dichloride, and the antimetastic activity of octahedral Ru(III) complexes is attracting attention, one of which is now on clinical trial. Ru(III), like several other metal ions, can be delivered to cells via the iron transport protein transferrin. 

Hydroalumination. Titanocene dichloride is an effective catalyst for hydro-uluminution of alkenes and alkynes with his(dialkylamino)alancs5 and various complex aluminum hydrides. The adducts can be quenched with water or iodine. The reaction is satisfactory for terminal alkenes and internal alkynes, but is not clcun for internal alkenes and terminal alkynes. 

Titanocene dichloride was the first metallocene derivative to be converted53 into dithiolato complexes, for example compound (38). Some other examples of this structural type exist, and their structural features are described in Section 16.5.3.1. 

It should be noted that titanocene-catalyzed carbosilylation of alkenes and dienes, which uses alkyl halides and chlorosilanes, involves alkyl radical addition to styrenes and dienes [68]. The reaction uses butylmagnesiumchloride and a catalytic amount of titanocene dichloride, which would form the complex... 

The nucleophilic 7i-allyltitanium complex 67 is prepared by the reaction of the conjugated diene 65 with titanocene hydride 66, generated in situ by the treatment of titanocene dichloride with 2 moles of z-PrMgCl [21]. The complex is nucleophilic and reacts with aldehydes regio- and stereoselectively to give homoallylic alcohols [22]. 

Dimethyltitanocene (213), called the Petasis reagent, can be used for alkenation of carbonyls (aldehydes, ketones, esters, thioesters and lactones). This reagent is prepared more easily than the Tebbe reagent by the reaction of titanocene dichloride with MeLi. However, this reagent may not be a carbene complex and its reaction may be explained as a nucleophilic attack of the methyl group at the carbonyl [67], Alkenylsilanes are prepared from carbonyl compounds. Tri(trimethylsilyl)titanacyclobutene (216), as a... 

Instead of titanocene dichloride, zirconocene dichloride can be used for the preparation of the carbene complex 219. The Lewis acidity of Zr is lower than that of Ti, and the Zr reagent 219 reacts smoothly with aldehydes and ketones, but not with esters [69]. 

Similarly, tethered titanacyclobutane complex 74 also undergoes protonolysis with 1 and 2 equiv of HC1 in toluene to give alkyltitanium chloride 75 and titanocene dichloride 76, respectively, in excellent yield (Scheme 10). Titanacyclobutane complex 74 can undergo also intramolecular proton transfer from one of the ligand methyl groups, presumably via a cr-bond metathesis, to give the 76-tetramethylfulvene alkyl complex 77 <19950M5481>. 

After formation of complex by combination of the titanocene dichloride and trialkyl aluminum, alkylation of the titanium component is presumed to take place. 

Titanocene dichloride, [TiIV(q5-C5H5)2Cl2], will be remembered in the history of metal-based drugs as a pioneer in the field of organometallic complexes with anticancer activity. 

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