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

The N,N,O‐cobalt(II), [2,3‐{C 4 H 8 C(NAr)}:5,6‐{C 4 H 8 C(O)}C 5 HN]CoCl 2 (Ar = 2,6‐(CHPh 2 ) 2 ‐4‐MeC 6 H 2 Co1 , 2,6‐(CHPh 2 ) 2 ‐4‐EtC 6 H 2 Co2 , 2,6‐(CHPh 2 ) 2 ‐4‐ClC 6 H 2 Co3 , 2,6‐(CHPh 2 ) 2 ‐4‐FC 6 H 2 Co4 ) and N,N,O‐iron(II) complexes, [2,3‐{C 4 H 8 C(NAr)}:5,6‐{C 4 H 8 C(O)}C 5 HN]FeCl 2 (Ar = 2,6‐(CHPh 2 ) 2 ‐4‐MeC 6 H 2 Fe1 , 2,6‐(CHPh 2 ) 2 ‐4‐EtC 6 H 2 Fe2 , 2,6‐(CHPh 2 ) 2 ‐4‐ClC 6 H 2 Fe3 , 2,6‐(CHPh 2 ) 2 ‐4‐FC 6 H 2 Fe4 ), each containing one sterically enhanced but electronically modifiable N‐2,6‐dibenzhydryl‐4‐R 2 ‐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 × 10 5 g mol −1 (Co) h −1 ) affording short chain oligomers (C 4 –C 30 ) with good α‐olefin selectivity. By contrast, Fe1 – Fe4 , 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 ) incorporating saturated n ‐propyl and i ‐butyl chain ends. For both cobalt and iron, the precatalysts incorporating the more electron withdrawing 4‐R 2 ‐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