Stoichiometric Compounds of Magnesium Dichloride with Ethanol for the Supported Ziegler-Natta Catalysis: First Recognition and Multidimensional MAS NMR Study

Ethanol assocs. easily with MgCl2 to form adducts of complex architecture, but until now available characterization methods have failed to identify the pure stoichiometric compds. and their structures. To remedy this, we set about applying homonuclear and heteronuclear 2D correlated solid-state NMR spectroscopy to identify the pure compds. and the ethanol-to-magnesium coordination pattern. High spinning speed and Lee-Goldburg sequences were able to reduce the hydrogen spin-diffusion and homonuclear coupling in the cryst. solid, thus achieving high resoln. also in the hydrogen domain. On this basis, the pure adducts, of interest as catalyst supports for Ziegler-Natta polymn., were isolated for the first time. Magnesium coordination sites with given nos. of ligands and their multiplicity in the crystal cells were detd. in the new-found stoichiometric complexes. Variable temp. and 2D carbon-carbon exchange NMR, as well as relaxation times in the fast motion regime, revealed the disordering phenomena generated by ethanol dynamics in the crystal. Decoding the intriguing polymorphism of the precursors permits to trace the genealogy of tailored MgCl2 titanate granules, active as highly productive catalysts for the stereospecific polymn. of olefins.