A catalyst system comprising a metal-ligand complex according to formula: where M is a metal chosen from titanium, zirconium, or hafnium, the metal having a formal oxidation state of +2, +3, or +4; each X is a monodentate or bidentate ligand independently chosen from unsaturated (C 2 -C 20)hydrocarbon, unsaturated (C 2 -C 50)heterohydrocarbon, (C 1 -C 50)hydrocarbyl, (C 6 -C 50)aryl, (C 6 -C 50)heteroaryl, cyclopentadienyl, substituted cyclopentadienyl, (C 4 -C 12)diene, halogen, -N(R N) 2, and -NCOR C; n is 1, 2 or 3; m is 1 or 2; the metal-ligand complex has 6 or fewer metal-ligand bonds; each Y is independently selected from oxygen or sulfur; each R 1, R 2, R 3, and R 4 is independently selected from the group consisting of (C 1 -C 50)hydrocarbyl, (C 1 -C 50)heterohydrocarbyl, (C 6 -C 50)aryl, (C 4 -C 50)heteroaryl, -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 -, halogen, and -H; each R 5 is independently chosen from (C 1 -C 50)hydrocarbyl, (C 1 -C 50)heterohydrocarbyl, (C 6 -C 50)aryl, (C 4 -C 50)heteroaryl, -Si(R C) 3, and -Ge(R C) 3, and, when m is 2, two R 5 are optionally covalently linked; for each individual ring containing groups z 1, z 2, and z 3, each of z 1, z 2, and z 3 is independently selected from the group consisting of sulfur, oxygen, -N(R R)-, or -C(R R)-, provided that at least one and not more than two of z 1, z 2, and z 3 are -C(R R)-, where R R is -H or (C 1 -C 30)hydrocarbyl, wherein any two R R groups bonded to neighboring atoms are optionally linked; each R C, R N, and R P in formula is independently a (C 1 -C 30)hydrocarbyl. M is a metal chosen from titanium, zirconium, or hafnium, the metal having a formal oxidation state of +2, +3, or +4; each X is a monodentate or bidentate ligand independently chosen from unsaturated (C 2 -C 20)hydrocarbon, unsaturated (C 2 -C 50)heterohydrocarbon, (C 1 -C 50)hydrocarbyl, (C 6 -C 50)aryl, (C 6 -C 50)heteroaryl, cyclopentadienyl, substituted cyclopentadienyl, (C 4 -C 12)diene, halogen, -N(R N) 2, and -NCOR C; n is 1, 2 or 3; m is 1 or 2; the metal-ligand complex has 6 or fewer metal-ligand bonds; each Y is independently selected from oxygen or sulfur; each R 1, R 2, R 3, and R 4 is independently selected from the group consisting of (C 1 -C 50)hydrocarbyl, (C 1 -C 50)heterohydrocarbyl, (C 6 -C 50)aryl, (C 4 -C 50)heteroaryl, -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 -, halogen, and -H; each R 5 is independently chosen from (C 1 -C 50)hydrocarbyl, (C 1 -C 50)heterohydrocarbyl, (C 6 -C 50)aryl, (C 4 -C 50)heteroaryl, -Si(R C) 3, and -Ge(R C) 3, and, when m is 2, two R 5 are optionally covalently linked; for each individual ring containing groups z 1, z 2, and z 3, each of z 1, z 2, and z 3 is independently selected from the group consisting of sulfur, oxygen, -N(R R)-, or -C(R R)-, provided that at least one and not more than two of z 1, z 2, and z 3 are -C(R R)-, where R R is -H or (C 1 -C 30)hydrocarbyl, wherein any two R R groups bonded to neighboring atoms are optionally linked; each R C, R N, and R P in formula is independently a (C 1 -C 30)hydrocarbyl.