TY - JOUR
T1 - MAO-free and extremely active catalytic system for ethylene tetramerization
AU - Kim, Tae Hee
AU - Lee, Hyun Mo
AU - Park, Hee Soo
AU - Kim, Sung Dong
AU - Kwon, Su Jin
AU - Tahara, Atsushi
AU - Nagashima, Hideo
AU - Lee, Bun Yeoul
N1 - Funding Information:
This research was supported by the Commercialization Promotion Agency for R&D Outcomes (COMPA) funded by the Ministry of Science, ICT and Future Planning (MISP) and additionally by the Ajou University Research Fund.
Funding Information:
Ajou University Research Fund; Ministry of Science, ICT and Future Planning (MISP); Commercialization Promotion Agency for R&D Outcomes (COMPA)
Publisher Copyright:
© 2019 John Wiley & Sons, Ltd.
PY - 2019/4
Y1 - 2019/4
N2 - The original Sasol catalytic system for ethylene tetramerization is composed of a Cr source, a PNP ligand, and MAO (methylaluminoxane). The use of expensive MAO in excess has been a critical concern in commercial operation. Many efforts have been made to replace MAO with non-coordinating anions (e.g., [B(C 6 F 5 ) 4 ] − ); however, most of such attempts were unsuccessful. Herein, an extremely active catalytic system that avoids the use of MAO is presented. The successive addition of two equivalent [H(OEt 2 ) 2 ] + [B(C 6 F 5 ) 4 ] − and one equivalent CrCl 3 (THF) 3 to (acac)AlEt 2 and subsequent treatment with a PNP ligand [CH 3 (CH 2 ) 16 ] 2 C(H)N(PPh 2 ) 2 (1) yielded a complex presumably formulated as [1-CrAl (acac)Cl 3 (THF)] 2+ [B(C 6 F 5 ) 4 ] − 2 , which exhibited high activity when combined with iBu 3 Al (1120 kg/g-Cr/h; ~4 times that of the original Sasol system composed of Cr (acac) 3 , iPrN(PPh 2 ) 2 , and MAO). Via the introduction of bulky trialkylsilyl substituents such as –SiMe 3 , –Si(nBu) 3 , or –SiMe 2 (CH 2 ) 7 CH 3 at the para-position of phenyl groups in 1 (i.e., by using [CH 3 (CH 2 ) 16 ] 2 C(H)N[P(C 6 H 4 -p-SiR 3 ) 2 ] 2 instead of 1), the activities were dramatically improved, i.e., tripled (2960–3340 kg/g-Cr/h; more than 10 times that of the original Sasol system). The generation of significantly less PE (<0.2 wt%) even at a high temperature is another advantage achieved by the introduction of bulky trialkylsilyl substituents. NMR studies and DFT calculations suggest that increase of the steric bulkiness on the alkyl-N and P-aryl moieties restrict the free rotation around (alkyl)N–P (aryl) bonds, which may cause the generation of more robust active species in higher proportion, leading to extremely high activity along with the generation of a smaller amount of PE.
AB - The original Sasol catalytic system for ethylene tetramerization is composed of a Cr source, a PNP ligand, and MAO (methylaluminoxane). The use of expensive MAO in excess has been a critical concern in commercial operation. Many efforts have been made to replace MAO with non-coordinating anions (e.g., [B(C 6 F 5 ) 4 ] − ); however, most of such attempts were unsuccessful. Herein, an extremely active catalytic system that avoids the use of MAO is presented. The successive addition of two equivalent [H(OEt 2 ) 2 ] + [B(C 6 F 5 ) 4 ] − and one equivalent CrCl 3 (THF) 3 to (acac)AlEt 2 and subsequent treatment with a PNP ligand [CH 3 (CH 2 ) 16 ] 2 C(H)N(PPh 2 ) 2 (1) yielded a complex presumably formulated as [1-CrAl (acac)Cl 3 (THF)] 2+ [B(C 6 F 5 ) 4 ] − 2 , which exhibited high activity when combined with iBu 3 Al (1120 kg/g-Cr/h; ~4 times that of the original Sasol system composed of Cr (acac) 3 , iPrN(PPh 2 ) 2 , and MAO). Via the introduction of bulky trialkylsilyl substituents such as –SiMe 3 , –Si(nBu) 3 , or –SiMe 2 (CH 2 ) 7 CH 3 at the para-position of phenyl groups in 1 (i.e., by using [CH 3 (CH 2 ) 16 ] 2 C(H)N[P(C 6 H 4 -p-SiR 3 ) 2 ] 2 instead of 1), the activities were dramatically improved, i.e., tripled (2960–3340 kg/g-Cr/h; more than 10 times that of the original Sasol system). The generation of significantly less PE (<0.2 wt%) even at a high temperature is another advantage achieved by the introduction of bulky trialkylsilyl substituents. NMR studies and DFT calculations suggest that increase of the steric bulkiness on the alkyl-N and P-aryl moieties restrict the free rotation around (alkyl)N–P (aryl) bonds, which may cause the generation of more robust active species in higher proportion, leading to extremely high activity along with the generation of a smaller amount of PE.
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U2 - 10.1002/aoc.4829
DO - 10.1002/aoc.4829
M3 - Article
AN - SCOPUS:85060946959
SN - 0268-2605
VL - 33
JO - Applied Organometallic Chemistry
JF - Applied Organometallic Chemistry
IS - 4
M1 - e4829
ER -