| prov:value
| - e represented by the formula:wherein R.sup.5 is hydrocarbon of 1-12 carbon atoms, X is halogen or hydrogen, and n is 1-3.In the above-mentioned formula, R.sup.5 is hydrocarbon of 1-12 carbon atoms, for example, alkyl, cycloalkyl or aryl, including concretely methyl, ethyl, n-propyl, isopropyl, isobutyl, pentyl, hexyl, octyl, cyclopentyl, cyclohexyl, phenyl, tolyl,etc.The organoaluminum compounds o
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