Disclosed are catalyst compositions for isoprene polymerization formed from components comprising (A) at least one titanium halide; (B) at least one organic aluminum compound comprising at least one alkyl aluminum of formula AlR3, wherein each of the three Rs is independently chosen from linear and branched C1-6 alkyl groups; and (C) at least one electron donor comprising at least one polyether compound of formula (I) and/or at least one tetrahydro-furfuryl ether compound of formula (II). Also disclosed are processes for preparation of the catalyst compositions and processes using the catalyst compositions for isoprene polymerization.