Studies on Ziegler-Natta catalysts. Part III. Composition of the nonvolatile product of the reaction between titanium trichloride and trimethylaluminum or dimethylaluminum chloride
The surface product formed in the reaction between TiCl3 and Al(CH3)3 has been studied. Stoichiometric data, CH3/CD3 exchange, and infrared spectra permit the conclusion that the surface product is essentially a compound having the formula A model structure is proposed for this compound, valid for the 001 face of α-TiCl3. In it the titanium and chlorine atoms maintain the positions which they occupy in the α-TiCl3 lattice. One of the methyl groups protrudes from the surface whereas the other occupies the chlorine vacancy created during the reaction in the chlorine surface layer. A different sterism of the methyl groups is compatible with the experimental result that half of the methyl groups are very easily exchanged whereas the other half are not touched by the exchanging agent. According to this model it has to be assumed that the titanium atoms in the 001 plane, by far the largest face of the α-TiCl3 crystal, are not accessible. A similar model, loading to equivalence conclusions is proposed for β-TiCl3. The infrared spectra of Al(CH3)3, Al(CD3)3, AlCl(CH3)2, AlCl(CD3)2, AlCl2CH3, AlCl2CD3, TiCl3CH3, TiCl3CD3, Hg(CD3)2, and Zn(CD3)2 are discussed. Spectra of surface products formed on interaction of some of these compounds with TiCl3 are given.
