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Preparation of Chromium Complexes for Ethylene Tetramerization Catalyst

  • 박준형 (Jun Hyeong Park, 아주대학교 일반대학원)

초록/요약

A persistent challenge in bringing a highly efficient and cost-effective ethylene tetramerization catalyst, denoted as [1CrCl2]+[B(C6F5)4]– (1 = iPrN[P(C6H4Si(Octyl)3)2]2), to commercial fruition lies in the occurrence of undesired polyethylene (PE) formation. To tackle this issue, we investigated various activator alternatives and determined that (Octyl)3Al emerged as the most effective choice for minimizing PE production. Furthermore, we considered the possibility that incomplete conversion of [1CrCl2]+[B(C6F5)4]– to [1CrR2]+[B(C6F5)4]– might be the root cause of PE formation. As part of a model study, we initiated a reaction between [iPrN(PPh2)2]CrCl3(THF) and an excess of Me3Al, leading to the formation of dinuclear Cr(II) species, ([iPrN(PPh2)2]Cr(2-Cl)(ClMe2AlClAlMe3))2, which we confirmed through X-ray crystallography. Building upon this observation, we synthesized [ortho-(MeO)C6H4CH2-1C:O]3Cr and verified its structure via X-ray crystallography. We then devised a catalytic system comprising this precursor, PNP ligand 1, a soluble borate salt [MeN(H)(C18H37)2]+[B(C6F5)4]–, and iBu3Al. However, despite its high activity comparable to [1CrCl2]+[B(C6F5)4]–, this catalytic system exhibited a prolonged induction period (~30 min) and generated a significant amount of PE. Returning to the catalytic system of [1CrCl2]+[B(C6F5)4]–, we successfully accomplished the conversion of [(EtOH)4CrCl2]+[B(C6F5)4]– to [(CH3CN)4CrCl2]+[B(C6F5)4]–, a crucial step in the large-scale synthesis of [1CrCl2]+[B(C6F5)4]–, through the design and implementation of a specialized glass apparatus. Finally, we found that adjusting the reaction conditions during the synthesis of [1CrCl2]+[B(C6F5)4]– could effectively reduce the generation of PE. Keywords : ethylene tetramerization, 1-octene production, chromium catalyst, bis(phosphine) ligand, tetrakis(pentafluorophenyl)borate

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목차

1. Introduction 1
2. Results and Discussion 3
2.1 Activation reaction 3
2.2 Preparation of [(CH3CN)4CrCl2]+[B(C6F5)4]- 8
2.3 Preparation of [1-CrCl2]+[B(C6F5)4]- and oligomerization studies 10
3. Experimental Section 13
3.1 General remarks 13
3.2 Preparation of ([iPrN(PPh2)2]Cr(2-Cl)(ClMe2AlClAlMe3))2 13
3.3 Preparation of [ortho-(MeO)C6H4CH2-1C:O]3Cr 14
3.4 Large scale synthesis of [(EtOH)4CrCl2]+[B(C6F5)4]– 14
3.5 Preparation of [(CH3CN)4CrCl2]+[B(C6F5)4]– 15
3.6 Preparation of [1CrCl2]+[B(C6F5)4]– 16
3.7 Ethylene tetramerization reaction (entry 6 in Table 2) 17
3.8 X-ray Crystallography 18
4. Conclusions 19
5. Acknowlegmetnts 20
6. References 20

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