A solid, hydrocarbon-insoluble, catalyst component useful in polymerizing olefins containing magnesium, titanium, and halogen further contains an internal electron donor comprising a compound containing electron donating substituents with a structure: ##STR00001## wherein D.sup.1 and D.sup.2 are selected individually from ##STR00002## and R, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, and R.sup.7 individually are hydrocarbon or substituted hydrocarbon groups containing 1 to 20 carbon atoms and R.sup.2, R.sup.3, R.sup.4, R.sup.6, and R.sup.7 may be hydrogen; R.sup.4 may be --NR.sub.2; and wherein groups R.sup.1 and R.sup.2, R.sup.2 and R.sup.3, R.sup.3 and R.sup.4, R.sup.3 and R.sup.5, and groups R.sup.6 and R.sup.7 may be joined to form a cyclic structure.