Cycloheptyl‐fused NNO‐ligands as electronically modifiable supports for M(II) (M = Co, Fe) chloride precatalysts; probing performance in ethylene oligo‐/polymerization

Abstract

The N,N,O‐cobalt(II), [2,3‐{C4H8C(NAr)}:5,6‐{C4H8C(O)}C5HN]CoCl2 (Ar = 2,6‐(CHPh2)2‐4‐MeC6H2 Co1, 2,6‐(CHPh2)2‐4‐EtC6H2 Co2, 2,6‐(CHPh2)2‐4‐ClC6H2 Co3, 2,6‐(CHPh2)2‐4‐FC6H2 Co4) and N,N,O‐iron(II) complexes, [2,3‐{C4H8C(NAr)}:5,6‐{C4H8C(O)}C5HN]FeCl2 (Ar = 2,6‐(CHPh2)2‐4‐MeC6H2 Fe1, 2,6‐(CHPh2)2‐4‐EtC6H2 Fe2, 2,6‐(CHPh2)2‐4‐ClC6H2 Fe3, 2,6‐(CHPh2)2‐4‐FC6H2 Fe4), each containing one sterically enhanced but electronically modifiable N‐2,6‐dibenzhydryl‐4‐R2‐phenyl group, have been prepared by a one‐pot template approach using α,α′‐dioxo‐2,3:5,6‐bis(pentamethylene)pyridine, the corresponding aniline along with the respective cobalt or iron salt in acetic acid. Distorted square pyramidal geometries are a feature of the molecular structures of Co1–Co4. Upon activation with MAO or MMAO, Co1–Co4 show good activities (up to 2.2 × 105 g mol−1(Co) h−1) affording short chain oligomers (C4–C30) with good α‐olefin selectivity. By contrast, Fe1–Fe4, in the presence of MMAO, displayed moderate activities (up 10.9 × 104 g(PE) mol−1(Fe) h−1) for ethylene polymerization forming low‐molecular‐weight linear polymers (up to 13.0 kg mol−1) incorporating saturated n‐propyl and i‐butyl chain ends. For both cobalt and iron, the precatalysts incorporating the more electron withdrawing 4‐R2‐substituents [Cl (Co3/Fe3), F (Co4/Fe4)] deliver the best catalytic activities, while with cobalt, these types of substituents additionally broaden the oligomeric distribution. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 3980–3989

Enhancing thermostability of iron ethylene polymerization catalysts through N,N,N-chelation of doubly fused α,α′-bis(arylimino)-2,3:5,6-bis(hexamethylene)pyridines

“…The FT-IR spectra of Fe1 -Fe5 show C=N stretching frequencies that fall in the range 1591 -1604 cm -1 , values that are quite typical of coordinated imine groups; no absorptions corresponding to coordinated C=O groups nor free diketone could be detected. 20 For Fe3' an absorption at 844 cm -1 can be assigned to an Fe-O-Fe asymmetric stretch as has been observed for a raft of related oxide-bridged iron(III) complexes. 19 Furthermore, the microanalytical data for the Fe1 -Fe5 and Fe3' are in agreement with the elemental compositions proposed.…”

Bis(imino)pyridines fused with 6- and 7-membered carbocylic rings as N,N,N-scaffolds for cobalt ethylene polymerization catalysts

“…In addition and similar to a previous report, 2b five broad upfield peaks ranging from δ -16.70 to -86.58 can be assigned to the isopropyl protons l (-16.70 and p ; the cycloalkyl methylene protons (CH2) are seen as a series of broad peaks (f -i and q) between δ 11.26 -1.20. In the FT-IR spectra of Co1 -Co5, stretching frequencies for the C=N Please do not adjust margins Please do not adjust margins bonds fall in the range 1613 -1624 cm -1 , characteristic of bound imino-nitrogen atoms; no absorption bands corresponding to a complexed ketonic C=O group 18 nor to free diketone 3 were visible. 13,14 Crystals of Co1, Co3 and Co4 suitable for the X-ray determinations were grown by slow diffusion of diethyl ether into a dichloromethane solution of the corresponding complex at ambient temperature.…”

Carbocyclic-fused N,N,N-pincer ligands as ring-strain adjustable supports for iron and cobalt catalysts in ethylene oligo-/polymerization

“…Conversely, iron-containing 69 in the presence of MMAO, displayed moderate activities (up 10.9 ×10 4 g(PE) mol -1 (Fe) h -1 ) for ethylene polymerization forming low molecular weight linear polymers (up to 13.0 Kg mol-1 ) containing saturated n-propyl and i-butyl chain ends. However, it should be emphasized that these complexes bearing N,N,O-tridentate ligands generally show lower activity than the corresponding ones bearing N,N,N-tridentate ligands[120,121,123]. Elsewhere it should be noted that cycloalkyl-fused N,N,N derivatives have not only proved effective supports for iron and cobalt complexes but have also shown great promise in chromium catalysis in which high activities toward ethylene oligo-/polymerization have been reported[124][125][126].<Figure 23>…”

“…Bis(arylimino)pyridine-iron complexes bearing bulky ortho-substituted N-aryl groups Benzhydryl-substituted bis(arylimino)pyridine-iron and -cobalt complexes 14-31 [70-81] Iron and cobalt complexes, 32-43, bearing phenanthroline-imines and related ligands [82-91] Aryl-fused N,N,N-iron and -cobalt pre-catalysts 44-50 [92-98] Related N,Npy,N-iron and -cobalt pre-catalysts 51-56 [83,99-105] Cyclohexyl-fused bis(arylimino)pyridines (B) as inspired by D and A [52-54,106-112] Singly cycloalkyl-fused (arylimino)pyridyl iron and cobalt pre-catalysts 57-63 [111-117] Doubly cycloalkyl-fused bis(arylimino)pyridine-iron and -cobalt pre-catalysts 64-Representative 1 H NMR spectrum of the vinyl-polyethylene obtained using cobalt complex 63 [Representative 13 C NMR spectrum of the vinyl-polyethylene obtained using cobalt complex 63 [Iron and cobalt complexes bearing cycloalkyl-fused N,N,O ligands[123] …”