Treatment with Alkylaluminum Compounds

Treatment with alkylaluminoxanes, MAO, or alkylaluminum compounds such as AIR3 (R = methyl [Me], ethyl [Et], or tertiary isobutyl [i-Bu]) can remove the residual water on the day surface and protect the upcoming coordination catalyst from deactivation because alkylaluminum compounds react strongly with water due to the strength of Al-O bonds (—350kJ mol ) as compared to Al-C bonds (—255kJ mol ) [53]. The complete removal of water from day requires thermal treatment at temperatures of about 400-600 °C, which leads to the partial collapse of the clay structure and CEC reduction. Even after thermal treatment, alkylaluminum compounds may still be used to scavenge residual water. 

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In this activation method, water molecules present on the surface of pristine clay react with alkylaluminum compounds to produce MAO oligomers on the clay surface [6, 50, 62, 81, 89]. The modified clay can then be used directly as a polymerization cocatalyst, or impregnated with a catalyst solution prior to polymerization. The high temperature thermal treatment to remove surface-bonded water molecules is not required in this case, albeit it has been used by some researchers [6, 50]. 

B,) Treatment of an organo- or a hydrido-nickel(II) compound with a Lewis acid. Organometallic compounds, such as alkylaluminum halides, which have Lewis acid properties, can also be used. 

A highly convenient and versatile cyclopropanation method has been devised which involves treatment of olefins with different organoaluminum compounds and alkylidene iodide under mild conditions [93]. Although Miller found that cyclopropane formation by use of EtsAl-methylene iodide in cyclohexene proceeds in quite disappointing yields [94], Yamamoto and Maruoka reached the conclusion that the intermediate dialkyl(iodomethyl)aluminum species 97 is responsible for the cyclopropanation of olefins and that it readily decomposes in the absence of olefins or in the presence of excess trialkylaluminum. Hence the use of equimolar amounts of trialkyl-aluminum and methylene iodide in the presence of olefins is essential for the achievement of reproducible results in the cyclopropanation process. In addition, because di-alkylaluminum halide can also be used as a cyclopropanation agent, the use of half an equivalent of trialkylaluminum is not detrimental (Sch. 61). 

Ziegler-Natta catalysts, which are of many different formulations, are organ ometallic transition-metaJ complexes prepared by treatment of an alkylaluminum with a titanium compound. Triethyl aluminum and titanium tetrachloride form a typical preparation. 

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