Ring-tension adjusted ethylene polymerization by aryliminocycloheptapyridyl nickel complexes

Abstract

The stoichiometric reactions of 5,6,7,8-tetrahydrocycloheptapyridin-9-one (cycloheptapyridin-9-one) with various anilines lead to corresponding mixtures of 9-aryliminocycloheptapyridine and the isomeric 9-arylamino-5,6,7-trihydrocycloheptapyridine derivatives; these compounds further reacted with nickel dichloride to form 9-aryliminocycloheptapyridyl nickel chlorides, respectively. The new organic compounds were analyzed by the NMR measurements, and all the organic and complex compounds were characterized by the FT-IR spectroscopy and elemental analysis. In addition, the molecular structures of representative nickel complexes and , determined by means of single-crystal X-ray diffraction, were found to be binuclear dimers with distorted square-pyramidal geometry around the nickel centers. On activation with either ethylaluminium sesquichloride (Et3Al2Cl3) or methylaluminoxane (MAO), all nickel complex pre-catalysts exhibited high activities of up to 7.80 × 10(6) g PE mol(-1) (Ni) h(-1) toward ethylene polymerization and produced highly branched polyethylenes in narrow polydispersity. The title nickel complexes showed comparable activities with 8-arylimino-5,6,7-trihydroquinolyl nickel analogues; whilst both exhibited higher activities than did the 2-iminopyridyl nickel analogues due to the enhancement of the ring-tension of cyclic-fused pyridine derivatives.

Targeting polyethylene waxes: 9-(2-cycloalkylphenylimino)-5,6,7,8-tetrahydrocycloheptapyridylnickel halides and their use as catalysts for ethylene polymerization

“…11 According to the GPC curves in Fig. 10,11 All GPC curves of the resulting polyethylenes ( Fig. 4,15 These phenomena were consistent with observations of their analogs.…”

“…In all cases, the real temperature was commonly higher than the setting temperature due to the exothermal reaction of the ethylene polymerization. 11 According to the GPC curves in Fig. The thermo-stability of this system was better than those obtained from the 9-arylamino-5,6,7-trihydrocycloheptapyridylnickel complexes.…”

Recent advances in Ni-mediated ethylene chain growth: Nimine-donor ligand effects on catalytic activity, thermal stability and oligo-/polymer structure

“…< Figure 22> The impact of strain within the fused cycloalkyl ring of the N,N-ligand framework has been thoroughly investigated and shown to affect the catalytic performance of the nickel pre-catalyst [107][108][109][110][111]. For example, the nickel complexes, 42, chelated by a 9-aryliminocycloheptapyridine N^N ligand have been synthesized and assessed for their ability to promote ethylene enchainment (Fig.…”

Synthesis and Evaluation of New Bis(imino) Pyridine Based Catalysts for Ethylene Polymerization

“…This value is considered low and it is possibly caused by the absence of stereohindrance in the ortho position on the aniline moieties of the catalyst skeleton, which causes the increase in chain termination reactions forming more terminal groups, especially vinyl groups, with relatively high absorption in the region of 908 cm -1 , due to β H transfer reaction. As reported in the literature [18], bulky substituents in the ortho-position suppress the chain migration process and also the chain termination reactions.…”