| 초록 |
The original Sasol catalytic system for ethylene tetramerization is composed of a Cr source, a PNP ligand, and MAO (methylaluminoxane). Without using MAO, The successive addition of 2eq [H(OEt2)2]+[B(C6F5)4]- and 1eq CrCl3(THF)3 to (acac)AlEt2 and 1eq PNP ligand [CH3(CH2)16]2C(H)N(PPh2)2 (1) yielded a complex presumably formulated as [1-CrAl(acac)Cl3(THF)]2+[B(C6F5)4]-2, which exhibited high activity when combined with iBu3Al (1120 Kg/g-Cr/h; ~4 times that of the original Sasol system). Via the introduction of bulky trialkylsilyl substituents such as –Si(nBu)3 at the para-position of phenyl groups in 1 (i.e., by using [CH3(CH2)16]2C(H)N[P(C6H4-p-SiR3)2]2, the activities were dramatically improved, i.e., tripled (3340 Kg/g-Cr/h; more than 10 times). 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. |
