Ligand effect on ethylene trimerisation with [NNN]-heteroscorpionate pyrazolyl Cr(III) catalysts
作者:Jun Zhang、Aifang Li、T. S. Andy Hor
DOI:10.1039/b909685j
日期:——
Cr(III) complexes with [NNN]-heteroscorpionate pyrazolyl ligands of the type Pz’2CHX (Pz’ = pyrazol-l-yl (Pz), or 3,5-dimethylpyrazol-1-yl (PzMe); X = N-containing heterocyclic ring or amine CH2NR1R2; R1, R2 = H or alkyl) have been prepared. Upon activation with MAO, they are active for selective ethylene trimerisation to 1-hexene. The effects of the hetero-functional group and chelate ring size on the catalytic performance have been examined. The pre-catalysts with an N-heterocycle substituent show highest activity [32400–53000 g/(g Cr h−1)] and total C6 selectivities (>97.6%) as well as 1-hexene selectivity (>96.0%) among hexenes. The X-ray single-crystal crystallographic analysis of CrCl3[PzMe2CH2NCH2Ph] and CrCl3[PzMe2CH2NCH2Fc] (Fc = ferrocenyl) shows a tridentate coordination on the fac-octahedral Cr(III) sphere with the Cr-N bond length dependent on the N-substituent.
我们制备了具有 [NNN]- 异蝎酸吡唑配体的 Pz'2CHX 型 Cr(III) 复合物(Pz' = 吡唑-l-基 (Pz) 或 3,5-二甲基吡唑-1-基 (PzMe);X = 含 N 的杂环或胺 CH2NR1R2;R1、R2 = H 或烷基)。在 MAO 的活化作用下,它们具有选择性乙烯三聚成 1-己烯的活性。我们研究了杂官能团和螯合环尺寸对催化性能的影响。具有 N-杂环取代基的前催化剂显示出最高的活性[32400-53000 g/(g Cr h-1)]和总 C6 选择性(>97.6%),以及在己烯中的 1-己烯选择性(>96.0%)。CrCl3[PzMe2CH2NCH2Ph]和 CrCl3[PzMe2CH2NCH2Fc](Fc = 二茂铁基)的 X 射线单晶晶体分析表明,在面八面体 Cr(III) 球上存在三叉配位,Cr-N 键的长度取决于 N 取代基。