. . "Non-limiting examples of such compounds are titanium and vanadium halides, e.g. titanium tetrachloride, vanadium tetrachloride, vanadium oxytrichloride, titanium and vanadium alkoxides, wherein the alkoxide moiety has a branched or unbranched alkyl group of 1 to about 20 carbon atoms, preferably 1 to about 6 carbon atoms." . . . . .