A process for preparing a low molecular weight polyethylene, poly-α-olefin or poly(co-ethylene-α-olefin) comprising a step of contacting together a monomer selected from (a) ethylene; (b) a non-ethylene α-olefin; or (c) a combination thereof; and a catalytic amount of a catalyst; wherein the catalyst comprises a mixture or reaction product of ingredients and that is prepared before the contacting step, wherein ingredient is at least one metal-ligand complex, and wherein ingredient is at least one activating co-catalyst; the metal-ligand complex of ingredient being at least one metal-ligand complex of 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 from 0 to 3, wherein when n is 0, X is absent; each X independently is 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 chosen in such a way that the metal-ligand complex of formula is, overall, neutral; each Z 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, wherein the (C 1 -C 40)hydrocarbylene has a portion that comprises a 2-carbon atom linker backbone linking the Z atoms in formula and the (C 1 -C 40)heterohydrocarbylene has a portion that comprises a 2-atom atom linker backbone linking the Z atoms in formula, wherein each atom of the 2-atom linker of the (C 1 -C 40)heterohydrocarbylene independently is 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; at least one of R 1a, R 2a, R 1b, and R 2b independently is a (C 1 -C 40)hydrocarbyl, (C 1 -C 40)heterohydrocarbyl, N(R N) 2, NO 2, OR C, SR C, Si(R C) 3. Ge(R C)3, CN, CF 3, F 3 CO, halogen atom; and each of the others of R 1a, R 2a, R 1b, and R 2b independently is a hydrogen, (C 1 -C 40)hydrocarbyl, (C 1 -C 40)heterohydrocarbyl, N(R N)2, NO 2, OR C, SR C, Si(R C) 3, CN, CF 3, F 3 CO or halogen atom; each of R 3a, R 4a, 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, CF 3, R C S -, R C S 2 -, (R C) 2 C=N-, R C C O-, R C OC -, R C C N -, (R C) 2 NC - or halogen atom; each of R 5c and R 5d independently is a (C 6 -C 40)aryl or (C 1 -C 40)heteroaryl; each of the aforementioned aryl, heteroaryl, hydrocarbyl, heterohydrocarbyl, hydrocarbylene, and heterohydrocarbylene groups independently is unsubstituted or substituted with one or more substituents R S; and each R S independently is a halogen atom, polyfluoro substitution, perfluoro substitution, unsubstituted (C 1 -C 18)alkyl, F 3 C-, FCH 2 O-, F 2 HCO-, F 3 CO-, R 3 Si-, R 3 Ge-, RO-, RS-, RS -, RS 2 -, R 2 P-, R 2 N-, R 2 C=N-, NC-, RC O-, ROC -, RC N -, or R 2 NC -, or two of the R S are taken together to form an unsubstituted (C 1 -C 18)alkylene, wherein each R independently is an unsubstituted (C 1 -C 18)alkyl; such that the ratio of total number of moles of the at least one metal-ligand complex to total number of moles of the at least one activating co-catalyst is from 1:10,000 to 100:1; under conditions such that a polyethylene, poly-α-olefin, or poly(co-ethylene-α-olefin), having a backbone weight average molecular weight (Mw) that is less than 2500 daltons (Da), is formed.