This invention relates to a catalyst compound represented by the formula: ##STR00001## wherein: M is a Group 3 to 12 transition metal; each R.sup.a is, independently, a hydrogen, a hydrocarbyl group, a substituted hydrocarbyl group or halogen; each of R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.7, R.sup.8, R.sup.9, R.sup.10, and R.sup.11 is, independently a hydrogen, a hydrocarbyl group, a substituted hydrocarbyl group or halogen; R.sup.6 is hydrogen, a hydrocarbyl group, or a substituted hydrocarbyl group; x is 0, 1, 2, 3 or 4; and each Z is, independently, a group 15 atom. This invention also relates to catalyst systems comprising the above catalyst compound and a activator and the use of such catalyst systems to polymerize monomers, including olefin monomers.