Dicyclopentadienyl titanium dichloride

Since the hemiacetal 3, can now readily be prepared from cheap commercially available starting materials (vide supra, Eq. (1))7), this reaction constitutes a convenient source of 1-vinylcyclopropanols. Otherwise, the 1-ethynyl-cyclopropanols 9, also easily available from 3 or from its magnesium salt 10 (vide supra, Eq. (4) and (6) underwent either lithium aluminium hydride reduction in refluxing THF to lead exclusively to the E-1-vinylcyclopropanols 69 or reduction with dicyclopentadienyl-titanium hydride in ether at 0.°C, prepared from isobutylmagnesium halides and a catalytic amount of dicyclopentadienyl titanium dichloride (r -CjH TiCk), to yield exclusively the Z isomer 70, Eq. (22) 15,39). 

Metal cyclopentadienyls have already proved to be of considerable technical interest. According to investigations carried out mainly in the United States, ferrocene is able to bring about smokeless combustion of fuel oil when added in amounts of 0.05% (1). Its use as an oil additive for jet motors and as an antiknock has also been proposed. Liquid ferrocene is said to have advantages as a thermally stable heat-transfer medium. Dicyclopentadienyl nickel also has possible applications, and dicyclopentadienyl titanium-dichloride has been studied in association with aluminum alkyls for the polymerization of ethylene (15, 133, 134). Finally, the carbonyl CHsC5H4Mn(CO)3 has been considered as a fuel additive in conjunction with tetraethyl lead (0). Other information is given in the patent literature (40). 

Bis(7 --cyclopentadienyl)bis [bis(trifluoromethyl)phosphinoxy Jtitanium, (vr- 5116)2X1 OP(CFs)2 2, is obtained quantitatively from dicyclopentadienyl-titanium dichloride and (CF3)2P 0 P(CF3)2 at 85 °C in toluene in a sealed tube in contrast, titanium tetrachloride undergoes a complex reaction leading to unidentified products under the same conditions. 

When TT-dicyclopentadienyl titanium dichloride is irradiated in the presence of carbon tetrachloride, 7r-cyclopentadienyl titanium trichloride is obtained in sufficient yield to be considered a new preparative method, equation (6-88). 

Aryl, alkyl, and vinyl halides can be reduced to hydrocarbons by the use of dicyclopentadienyl titanium dichloride and magnesium (Nelson and Tufar-iello, 1975) or isopropylmagnesium bromide (Colomer and Corriu, 1975). 

Titanium bis-enolate 19, readily available by transmetallation of the lithium enolate of acetaldehyde with dicyclopentadienyl titanium dichloride (Cp2TiCl2), was characterized by a crystal structure analysis [53, 54]. Mono-enolates of titanium and zirconium 20 were obtained analogously from Cp2Ti(Me)Cl and... 

The previously isolated1654 / // -/rtitanium dichloride has been prepared by a new route, involving the reductive dimerization of 6-phenylfulvene with activated calcium powder followed by treatment with TiCl3/AlCl3 (1 3) and oxidation in air. This complex has been used to synthesize a variety of other // -derivatives through ligand replacement (Scheme 642). The reaction of 6,6-diphenylfulvene... 

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