| abstract |
Compounds of the formula (I) wherein n is 1, 2, 3 or 4; X?1 and X2¿ are each, independently, chlorine or bromine; A is O or S; R1 is hydrogen or C¿1?-C16 alkyl; R?2 is C¿1-C16 alkyl, C6-C16 aryl, C1-C4 alkylidene, or CH2OR5; R3 is hydrogen, chlorine, bromine, or OR?6; R4 is C¿1-C16 alkyl, C7-C16 aralkyl, C2-C16 alkenyl, or C6-C18 aryl; R5 is hydrogen, C¿1?-C16 alkyl, C7-C16 aralkyl, C2-C16 alkenyl, or C6-C18 aryl; and R?6¿ is hydrogen or C¿1?-C16 alkyl. These compounds by themselves and in combination with certain halo-but-2-enoic acids and esters are useful as catalyst promoters in ethylene polymerization processes. |