This invention relates to a catalyst composition of the formula: ##STR00001## where Z--O is a support material, where O is oxygen, preferably Z is Si, Ti, Al, Sn, Fe, Ga, Zr, B, Mg, or Cr; each X is, independently, N, O, P or S; each n is, independently, 1 or 2; each R is, independently, an alkyl group, a substituted alkyl group, an aryl group, or a substituted aryl group, provided at least one R group is an aryl or substituted aryl group.This invention also relates to the use of the above catalyst compound with an aluminum alkyl to polymerize olefins and other monomers.