Abstract: A catalyst precursor having the formula: ##STR1## wherein M is a Group IVB metal; each L is a monovalent, bivalent, or trivalent anion;X and Y are each heteroatoms;each Cyclo is a cyclic moiety;each R.sup.1 is a group containing 1 to 50 atoms selected from the group consisting of hydrogen and Group IIIA to Group VIIA elements, and two or more adjacent R.sup.1 groups may be joined to form a cyclic moiety;each R.sup.2 is a group containing 1 to 50 atoms selected from the group consisting of hydrogen and Group IIIA to Group VIIA elements, and two or more adjacent R.sup.2 groups may be joined to form a cyclic moiety;W is a bridging group; andeach m is independently an integer from 0 to 5.