A method of using a dielectric fluid composition comprising a poly-α-olefin or a poly(co-ethylene/α-olefin) having a weight average molecular weight more than 200 and less than 5,000 daltons (Da) said method including a step of contacting together a monomer selected from (a) an α-olefin; or (b) a combination of an α-olefin and ethylene; and a catalytic amount of a catalyst wherein the catalyst includes a mixture or reaction product of ingredients and that is prepared before the contacting step, wherein ingredient is 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 of 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; 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, 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)hetero-aryl; each of the aforementioned aryl, heteroaryl, hydrocarbyl, heterohydrocarbyl, hydrocarbylene, and hetero-hydrocarbylene 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; and wherein ingredient is at least one activating co-catalyst, 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 product selected from a poly-α-olefin and a poly(co-ethylene-α-olefin) is formed, the product having molecular weight distribution components and a backbone weight average molecular weight (Mw) that are more than 200 Da and less than 5,000 Da, the product including at least two isomers in each distribution component above 300 Da, the method comprising operating at least one of a transformer containing a transformer oil comprising the dielectric fluid composition; transmission and distribution cable insulation fluids; switchgear fluids; dielectric fluids for telecommunications cables; and dielectric fluids for an electronic device or an electrical apparatus.