Interaction of titanium(III) zwitterionic complex Cp[η5-C5H4B(C6F5)3]Ti with organic halides: Synthesis and X-ray crystal structure determination of zwitterionic titanocene monohalides Cp[η5-C5H4B(C6F5)3]TiX (X = Cl, Br) and their catalytic activity in th

The reaction of the titanium(III) zwitterionic complex Cp[η5-C5H4B(C6F5)3]Ti (1) with CCl4 at 20 °C under Ar results in the formation of hexachloroethane and the zwitterionic titanocene monochloride Cp[η5-C5H4B(C6F5)3]TiCl (3) containing a B(C6F5)3 moiety in the η5-cyclopentadienyl ring. Under similar conditions, the reaction of 1 with 1,2-dibromoethane affords ethylene and the corresponding zwitterionic monobromide Cp[η5-C5H4B(C6F5)3]TiBr (4). An X-ray diffraction study of 3 and 4 revealed the presence of a coordinative bond between the ortho-fluorine atom of one of the C6F5 substituents and the positively charged titanium centre. In the interaction of 1 with n-propyl iodide at 20 °C, titanocene diiodide, B(C6F5)3 and propylene are produced. The mechanism of this interesting reaction is discussed. The synthesized zwitterions 3 and 4 are able to catalyze the ring-opening polymerization of ε-caprolactone in a toluene solution and in bulk. The highest activity in this process is exhibited by 3. The first X-ray diffraction study of Cp2TiI2 has been carried out.

Graphical abstractThe synthesis of zwitterionic titanocene monohalides Cp[η5-C5H4B(C6F5)3]TiX (X = Cl, Br) by the interaction of Cp[η5-C5H4B(C6F5)3]Ti (1) with CCl4 and 1,2-dibromoethane, respectively, is reported. The synthesized zwitterions contain a coordinative bond between the ortho-fluorine atom of one of the C6F5 substituents and the titanium centre. The both zwitterions catalyze the ring-opening polymerization of ε-caprolactone. The interaction of 1 with n-propyl iodide affords Cp2TiI2, B(C6F5)3 and propylene. The mechanism of this interesting reaction is discussed.Figure optionsDownload full-size imageDownload as PowerPoint slide