nctional group or atom which reacts with the above aluminum compound; (iv) a halide of the formula R3X, wherein R3 is a C1-8 alkyl radical and x is a halide selected from the group consisting of chlorine and bromine; (v) transition metal halide, preferably titanium tetrachloride, to provide a molar ratio of Mg to Al1 from 2.0:1 to 12:1; Mg:transition metal (e.g. Ti) from 3 to 8; a molar ratio of A