The SuzukiMiyaura coupling reaction of brominated butyl rubber (BIIR) and/or chlorinated butyl rubber with a mixture of 4-vinylphenylboronic acid and phenylboronic acid was carried out in THF under various conditions using a di-mu-chlorobis [5-hydroxy-2-[1-(hydroxyimino-kappa N)ethyl]phenyl kappa C] palladium(II) dimer, which is a type of cyclopalladated complex, as a catalyst. When BIIR and a small amount (Pd/Br approximate to 1/1000) of complex were used as the substrate and catalyst, respectively, a 4-vinylphenyl and phenyl group could be introduced to butyl rubber in a high yield. Isomerization of the exo carboncarbon double bond in BIIR was observed during the coupling reaction to give a cis and trans endo structure. The peroxide curing behavior of the resulting polymer at 170 degrees C indicated that the polymer could be cured by dicumyl peroxide, and the maximum torque of the resulting material, which reflects the crosslink density, was controllable by the composition of the boronic acids used. (c) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 50: 659-664, 2012