koxide or aryloxide group and R2 is an alkoxide or aryloxide group or halogen, with a halide of tetravalent titanium in the presence...http://www.google.es/patents/US4414132?utm_source=gb-gplus-sharePatente US4414132 - Olefin polymerization catalyst compositions and a process for the polymerization of olefins employing such compositions B???squeda avanzada de patentes N???mero de publicaci???nUS44