A process for preparing an olefin homopolymer or copolymer, comprising contacting ethylene, an alpha-olefin, or a combination thereof, and a catalytic amount of a metal-ligand complex catalyst of the formula: wherein M is titanium, zirconium, or hafnium, each independently being in a formal oxidation state of +2, +3, or +4; n is an integer of from 0 to 3, wherein when n is 0, X is absent; each X is independently a monodentate ligand that is neutral, monoanionic, or dianionic, or two X are taken together to form a bidentate ligand that is neutral, monoanionic, or dianionic; X and n are selected such that the metal-ligand complex is neutral; each Z moiety independently is O, S, N(C 1 -C 40) hydrocarbyl, or P(C 1 -C 40) hydrocarbyl; L is (C 1 -C 40)hydrocarbylene or (C 1 -C 40)heterohydrocarbylene, provided such has a portion that comprises a 2- to 8-carbon atom linker backbone linking the Z moieties, each atom of such 2- to 8-atom linker being independently a carbon atom or a heteroatom, wherein each heteroatom independently is O, S, S, S 2, Si(R C) 2, Ge(R C) 2, P(R p), or N(R N), wherein independently each R C is unsubstituted (C 1 -C 18)hydrocarbyl or the two R C are taken together to form a (C 2 -C 19)alkylene, each R P is unsubstituted (C 1 -C 18)hydrocarbyl; and each R N is unsubstituted (C 1 -C 18)hydrocarbyl, a hydrogen atom or absent; R 1a, R 1b, or both is a halogen atom; R 2a, R 3a, R 4a, R 2b, R 3b, R 4b, R 6c, R 7c, R 8c, R 6d, R 7d, and R 8d independently is a hydrogen atom; (C 1 -C 40)hydrocarbyl; (C 1- C 40)heterohydrocarbyl; Si(R C) 3, Ge(R C) 3, P(R P) 2, N(R N) 2, OR C, SR C, NO 2, CN, F 3 C, F 3 CO, RCS -, RCS 2 -, 2 C=N-, RCC O-, RCOC -, RCC N -, 2 NC - or halogen atom; and R 5c and R 5d is independently selected from 2,7-di(tertiary-butyl)-carbazol-9-yl; 2,7-di(tertiary-octyl)-carbazol-9-yl; 2,7-diphenylcarbazol-9-yl; and 2,7-bis(2,4,6-trimethylphenyl)-carbazol-9-yl; under conditions such that an ethylene homopolymer, an alpha-olefin homopolymer, or an ethylene/alpha-olefin copolymer is formed, such having a weight average molecular weight that is reduced by at least 20 percent when compared with an otherwise identical ethylene homopolymer, alpha- olefin homopolymer or ethylene/alpha-olefin copolymer prepared under identical conditions with a catalyst that is otherwise identical but wherein neither R 1a nor R 1b is a halogen atom. wherein M is titanium, zirconium, or hafnium, each independently being in a formal oxidation state of +2, +3, or +4; n is an integer of from 0 to 3, wherein when n is 0, X is absent; each X is independently a monodentate ligand that is neutral, monoanionic, or dianionic, or two X are taken together to form a bidentate ligand that is neutral, monoanionic, or dianionic; X and n are selected such that the metal-ligand complex is neutral; each Z moiety independently is O, S, N(C 1 -C 40) hydrocarbyl, or P(C 1 -C 40) hydrocarbyl; L is (C 1 -C 40)hydrocarbylene or (C 1 -C 40)heterohydrocarbylene, provided such has a portion that comprises a 2- to 8-carbon atom linker backbone linking the Z moieties, each atom of such 2- to 8-atom linker being independently a carbon atom or a heteroatom, wherein each heteroatom independently is O, S, S, S 2, Si(R C) 2, Ge(R C) 2, P(R p), or N(R N), wherein independently each R C is unsubstituted (C 1 -C 18)hydrocarbyl or the two R C are taken together to form a (C 2 -C 19)alkylene, each R P is unsubstituted (C 1 -C 18)hydrocarbyl; and each R N is unsubstituted (C 1 -C 18)hydrocarbyl, a hydrogen atom or absent; R 1a, R 1b, or both is a halogen atom; R 2a, R 3a, R 4a, R 2b, R 3b, R 4b, R 6c, R 7c, R 8c, R 6d, R 7d, and R 8d independently is a hydrogen atom; (C 1 -C 40)hydrocarbyl; (C 1- C 40)heterohydrocarbyl; Si(R C) 3, Ge(R C) 3, P(R P) 2, N(R N) 2, OR C, SR C, NO 2, CN, F 3 C, F 3 CO, RCS -, RCS 2 -, 2 C=N-, RCC O-, RCOC -, RCC N -, 2 NC - or halogen atom; and R 5c and R 5d is independently selected from 2,7-di(tertiary-butyl)-carbazol-9-yl; 2,7-di(tertiary-octyl)-carbazol-9-yl; 2,7-diphenylcarbazol-9-yl; and 2,7-bis(2,4,6-trimethylphenyl)-carbazol-9-yl; under conditions such that an ethylene homopolymer, an alpha-olefin homopolymer, or an ethylene/alpha-olefin copolymer is formed, such having a weight average molecular weight that is reduced by at least 20 percent when compared with an otherwise identical ethylene homopolymer, alpha- olefin homopolymer or ethylene/alpha-olefin copolymer prepared under identical conditions with a catalyst that is otherwise identical but wherein neither R 1a nor R 1b is a halogen atom.