Catalysts for olefin polymeriztion comprising metal complexes corresponding to the formula: ##STR1## or a dimer, solvated adduct, chelated derivative or mixture thereof, wherein:L is a cyclic group or Y*, that is bound to M by means of a delocalized .pi.-bond, said group containing up to 50 nonhydrogen atoms;L' is a cyclic group or Y* that is bound to M by means of a delocalized .pi.-bond, said group containing up to 50 nonhydrogen atoms;M is a metal of Group 4 of the Periodic Table of the Elements;Z is a covalently bound, divalent substituent of up to 50 non-hydrogen atoms having the formula, --(ER.sub.2).sub.m --, wherein E independently each occurrence is carbon, silicon or germanium, R independently each occurrence is selected from the group consisting of hydrocarbyl, hydrocarbyloxy, silyl, and germyl of up to 20 atoms other than hydrogen, and m is an integer from 1 to 3;Y* is an allyl or a hydrocarbyl-, silyl- or germyl-substituted allyl group containing up to 20 nonhydrogen atoms bonded to Z and bonded via an .eta..sup.3 -.pi. bond to M;where Y' is an allyl group or a hydrocarbyl-, silyl-, or germyl-substituted allyl group containing up to 20 nonhydrogen atoms bonded via an .eta..sup.3 -.pi. bond to M;X' is a neutral conjugated diene ligand having up to 20 non-hydrogen atoms;X" independently each occurrence is a monovalent, anionic moiety selected from hydride, halo, hydrocarbyl, silyl, germyl, hydrocarbyloxy, amide, siloxy, halohydrocarbyl, halosilyl, silylhydrocarbyl, and aminohydrocarbyl having up to 20 non-hydrogen atoms, or two X" groups together form a divalent hydrocarbadiyl group;n is a number from 0 to 3; andp is an integer from 0 to 2.