trichloride ferric chloride gallium trichloride molybdenum pentachloride phosphorus tribromide phosphorus pentachloride stannic chloride titanium tetrachloride titanium tetraiodide tungsten hexachloride and the like and 4 organometallic group iii b halides such as t butyl salicylaldehydrocerium iii chloride salicylaldehydrocerium iii chloride 5 cyclohexylsalicylaldehydrocerium iii chloride 2 acetylphenolatocerium iii chloride oxalatocerium iii chloride oxalatocerium iii bromide and the like 5 tertiary alkyl halides such as t butyl bromide and t octyl bromide 6 secondary alkyl halides such as isopropyl bromide and isopropyl chloride 7 aralkyl halides such as benzyl bromide and bromomethyl naphthalene and 8 allyl halides such as allyl bromide 3 chloro 2 methylpropene 1 bromobutene 2 and 1 bromopentene 2 the preferred compounds which contain labile halogen atoms are benzyl halides and allyl halides the polymerization temperature utilized can vary over a broad range of from about 0 u00b0 c to about 125 u00b0 c in most cases a temperature within the range of about 30 u00b0 c to about 85 u00b0 c will be utilized temperatures within the range of about 50 u00b0 c to about 75 u00b0 c are generally the most preferred polymerization temperatures the pressure used will normally be sufficient to maintain a substantially liquid phase under the conditions of the polymerization reaction the polymerization is conducted for a length of time sufficient to permit substantially complete polymerization of monomers in other words the polymerization is normally carried out until high conversions are attained the polymerization can then be terminated using a standard technique the isoprene butadiene rubbers which are made by utilizing the.