Abstract: This description addresses a process for the preparation of polyolefins from one or more olefinic monomers comprising combining said olefins under olefin polymerization conditions with an organometallic catalyst compound that is activated for olefin polymerization by reaction with a Group 13 element cocatalyst complex comprising at least one halogenated, nitrogen-containing aromatic group ligand. High number-average molecular weight polymers and copolymers at high rates of productivity were observed from the use of metallocene catalysts complexes when activated with [(C6H5)3C][(C6F5)3B(C5F4N)].