The reactions of 2,6-bis(3,5-dimethylpyrazol-1-ylmethyl)pyridine (L1) and 2,6-bis(3,5-di-tert-butylpyrazol-1-ylmethyl)pyridine (L2) with NiCl 2 or NiBr 2 gave the nickel(II) complexes [NiCl 2 (L1)] (1), [NiBr 2 (L1)] (2), [NiCl 2 (L2)] (3), and [NiBr 2 (L2)] (4) in high yields. Compounds 2-(3,5-dimethylpyrazol-1-ylmethyl)pyridine (L3) and 2-(3,5-di-tert-butylpyrazol-1-ylmethyl)pyridine (L4) on the other hand gave either mononuclear or dinuclear nickel(II) complexes, depending on the steric bulk of the substituents on the pyrazolyl unit. While L3 gave the dinuclear complexes [Ni 2 (µ 2 -Cl) 2 Cl 2 (L3) 2 ] (5) and [Ni 2 (µ 2 -Br) 2 Br 2 (L3) 2 ] (6), L4 gave the mononuclear complexes [NiCl 2 (L4)] ( 7) and [NiBr 2 (L4)] ( 8). Activation of 1-8 with EtAlCl 2 resulted in the oligomerization of ethylene to C 4 , C 6 , and C 8 alkenes, followed by subsequent Friedel-Crafts alkylation of the toluene solvent. Activities as high as 15 660 kg of alkylated products/mol Ni/h were observed for 5 at 40 bar. However, when hexane was used as solvent, only trace amounts of alkylated toluene products were observed.

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The structural and kinetic studies of polymerization reactions of ε-caprolactone (ε-CL) using (pyrazolylmethyl)pyridine Cu(II) and Zn(II) complexes as initiators is described. Reactions of 2-(3,5-dimethylpyrazol-1-ylmethyl)pyridine (L1) and 2-(3,5-diphenylpyrazol-1-ylmethyl)pyridine (L2) with Zn(Ac)2·2H2O or Cu(Ac)2·2H2O produced the corresponding complexes [Zn(Ac)2(L1)] (1), [Cu(Ac)2(L1)] (2), [Zn(Ac)2(L2)] (3) and [Cu2(Ac)4(L2)2] (4) respectively. Solid state structures of 1 and 4 confirmed that complexes 1 and 4 are monomeric and dimeric respectively and that L1 is bidentate in 1 while L2 is monodentate in 4. X-band EPR spectra of 2 and 4 revealed that complex 2 is monomeric both in solid and solution state, while the paddle-wheel structure of 4 is retained in solution. Complexes 1-4 formed active initiators in the ring opening polymerization of ε-CL. Zn(II) complexes 1 and 3 exhibited higher rate constants of 0.044 h(-1) and 0.096 h(-1) respectively compared to rate constants of 0.017 h(-1) and 0.031 h(-1) observed for the corresponding Cu(II) complexes 2 and 4 respectively at 110 °C. All the polymerization reactions follow pseudo first-order kinetic with respect to ε-CL monomer. Initiator 1 showed first-order dependency on the polymerization reactions and utilizes only one active site as the initiating group. The molecular weights of the polymers produced range from 1982 g mol(-1) to 14,568 g mol(-1) and exhibited relatively broad molecular weight distributions associated with transesterification reactions.