The α,α′-bis(imino)-2,3:5,6-bis(pentamethylene)pyridyl-cobalt(II) chlorides, [2,3:5,6-{C₄H₈C(N(2-R¹-4-R³-6-R²C₆H₂))}₂C₅HN] CoCl₂ (R¹ = Me, R² = R³ = CH(p-FPh)₂Co1; R¹ = Et, R² = R³ = CH(p-FPh)₂Co2; R¹ = i-Pr, R² = R³ = CH(p-FPh)₂Co3; R¹ = Cl, R² = R³ = CH(p-FPh)₂Co4; R¹ = F, R² = R³ = CH(p-FPh)₂Co5; R¹ = F, R² = R³ = CHPh₂Co5′′, R¹ = R² = Me, R³ = CH(p-FPh)₂Co6; R¹ = R³ = Me, R² = CH(p-FPh)₂Co7), have been synthesized by a one-pot template reaction of α,α′-dioxo-2,3:5,6-bis(pentamethylene)pyridine, cobalt(II) chloride and the respective aniline in n-butanol. By contrast, the mixed cobalt(II) chloride/acetate complex, [2,3:5,6-{C₄H₈C(N(2-F-4,6-(CH(p-FPh)₂)₂C₆H₂))}₂C₅HN]CoCl(OAc) (Co5′), was isolated when the corresponding template reaction was carried out in acetic acid. Structural characterization of Co4, Co5 and Co5′′ revealed distorted square pyramidal geometries while six-coordinate Co5′, incorporating a chelating acetate ligand, exhibited a distorted octahedral geometry. On activation with either MAO or MMAO, 2-fluoride-4,6-bis{di(p-fluorophenyl)methyl}-substituted Co5 showed maximum catalytic activity for ethylene polymerization at a high operating temperature of 60 °C (up to 2.1 × 10⁷ g (PE) mol⁻¹ (Co) h⁻¹), producing highly linear (T_ms > 121 °C), low molecular weight polyethylene waxes (M_w range: 1.5–5.0 kg mol⁻¹) with narrow dispersity (M_w/M_n range: 1.7–2.9). End-group analysis of the waxes reveals β-H elimination as the dominant chain transfer process.

A novel robust diphosphine–ruthenium( ii ) complex has been developed that can efficiently catalyze both the hydrogenation of CO ₂ to methanol and its in situ condensation with carboxylic acids to give methyl esters.

A one-pot template strategy has been utilized to synthesize sterically enhanced bis(imino)cyclohepta[b]pyridine-cobalt(II) chlorides, [2-{(Ar)NCMe}-9-{N(Ar)}C₁₀H₁₀N]CoCl₂ (Ar = 2-(C₅H₉)-4,6-(CHPh₂)₂C₆H₂Co1, 2-(C₆H₁₁)-4,6-(CHPh₂)₂C₆H₂Co2, 2-(C₈H₁₅)-4,6-(CHPh₂)₂C₆H₂Co3, 2-(C₁₂H₂₃)-4,6-(CHPh₂)₂C₆H₂Co4, 2,6-(C₅H₉)₂-4-(CHPh₂)C₆H₂Co5). All five complexes have been characterized by a combination of FT-IR spectroscopy, elemental analysis and single crystal X-ray diffraction. The molecular structures of Co1, Co3 and Co5 highlight the substantial steric hindrance imparted by the 2-cycloalkyl-6-benzhydryl or 2,6-dicyclopentyl ortho-substitution pattern; distorted square pyramidal geometries are exhibited in each case. On activation with methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), all the complexes (apart from Co4/MAO) were active ethylene polymerization catalysts (up to 3.70 × 10⁶ g PE per mol (Co) per h for Co5/MMAO), operating effectively at temperatures between 50 °C and 60 °C, producing polyethylenes with high molecular weights (up to 589.5 kg mol⁻¹ for Co3/MAO). Furthermore, all polymers were highly linear (T_m > 130 °C) with narrow dispersities (M_w/M_n range: 2.0–3.0). The coexistence of two chain termination pathways, β-H elimination and transfer to aluminum, has been demonstrated using ¹³C/¹H NMR spectroscopy.

Five examples of bis(arylimino)tetrahydrocyclohepta[b]pyridine dichloroiron(II) complex, [2-{(Ar)N=CMe}-9-{N(Ar)}C₁₀H₁₀N]FeCl₂ (Ar = 2-(C₅H₉)-4,6-(CHPh₂)₂C₆H₂Fe1, 2-(C₆H₁₁)-4,6-(CHPh₂)₂C₆H₂Fe2, 2-(C₈H₁₅)-4,6-(CHPh₂)₂C₆H₂Fe3, 2-(C₁₂H₂₃)-4,6-(CHPh₂)₂C₆H₂Fe4, and 2,6-(C₅H₉)2-4-(CHPh₂)C₆H₂Fe5), incorporating ortho-pairings based on either benzhydryl/cycloalkyl (ring sizes ranging from 5 to 12) or cyclopentyl/cyclopentyl groups, have been prepared in reasonable yield by employing a simple one-pot template strategy. Each complex was characterized by FT-IR spectroscopy, elemental analysis, and for Fe3 and Fe5 by single crystal X-ray diffraction; pseudo-square pyramidal geometries are a feature of their coordination spheres. On treatment of Fe1–Fe5 with modified methylaluminoxane (MMAO) or methylaluminoxane (MAO), a range in catalytic activities for ethylene polymerization were observed with benzhydryl/cyclopentyl-containing Fe1/MMAO achieving the maximum level of 15.3 × 10⁶ g PE mol⁻¹ (Fe) h⁻¹ at an operating temperature of 70 °C. As a key trend, the activity was found to drop as the ortho-cycloalkyl ring size increased: Fe1_C5H9/CHPh2~Fe5_C5H9/C5H9 > Fe2_C6H11/CHPh2 > Fe3_C8H15/CHPh2 > Fe4_C12H23/CHPh2. Furthermore, strictly linear polyethylenes (T_m > 126 °C) were formed with molecular weights again dependent on the ortho-cycloalkyl ring size (up to 55.6 kg mol⁻¹ for Fe1/MAO); narrow dispersities were a characteristic of all the polymers (M_w/M_n range: 2.3–4.7), highlighting the well-controlled nature of these polymerizations.