in which R1 and R2 denote each a hydrocarbon group containing usually 1-15 carbon atoms, preferably 1-4 carbon atoms, which may be identical with or different from each other, X is a halogen atom, 0<m???3, 0???n<3, 0???p<3 and 0???q<3, with m+n+p+q=3; and organoaluminum complex compounds represented by the general formula (14)