Biscyclopentadienyltitanium(III) chloride dimer

Abstract

[123526-85-2] C20H20Cl2Ti2 (MW 425.99) InChI = 1S/4C5H5.2ClH.2Ti/c4*1-2-4-5-3-1;;;;/h4*1-5H;2*1H;;/q;;;;;;2*+1/p-2 InChIKey = VZIFHIFDDXIKEL-UHFFFAOYSA-L (reagent used for generation of carbon radicals from epoxides and organic halides, and as a precursor for preparation of η3-allyltitanium compounds and PhMe2SiTiCp2) Physical Data: yellowish-green solid; does not melt below 250 °C; d 1.53 g cm−3. Solubility: soluble in ether, THF, benzene, and most organic solvents. Biscyclopentadienyltitanium(III) chloride (Cp2TiCl) exists as a chloride-bridged dimer in its solid state but dissociates to a monomeric species in the presence of a donor solvent such as THF. Preparative Methods: reduction of biscyclopentadienyltitanium(IV) dichloride (Cp2TiCl2) with Al foil or wire in ether for 16 h at room temperature gives a green solution of (Cp2TiCl)2.3 A solution of (Cp2TiCl)2 is also prepared by refluxing a mixture of TiCl3 and 2 equiv of cyclopentadienylthallium in THF for 1 h.4 The compound (Cp2TiCl)2 thus generated can be isolated by filtration of the reaction mixture and subsequent concentration. A solution of (Cp2TiCl)2 is conveniently generated in situ by reduction of Cp2TiCl2 with an alkyl-Grignard reagent,5 zinc,6-8 or SmI2,9 and can be used directly in subsequent reactions. Purification: sublimed in an evacuated sealed tube at 150 °C or recrystallized from THF–ether. Handling, Storage, and Precautions: store and handle under an atmosphere of dry nitrogen or argon either in a dry box or using Schlenk-tube techniques, because (Cp2TiCl)2 is very air-sensitive.