The present invention provides a catalyst precursor and catalyst system comprising the precursor, an embodiment of the precursor is selected from the following structures:
wherein T is a bridging group; M is selected from Groups 3 to 7 atoms, and the Lanthanide series of atoms the Periodic Table of the Elements; Z is a coordination ligand; each L is a monovalent, bivalent, or trivalent anionic ligand; X and Y are each independently selected from nitrogen, oxygen, sulfur, and phosphorus; R is a non-bulky substituent that has relatively low steric hindrance with respect to X; and R′ is a bulky substituent that is sterically hindering with respect to Y.
本发明提供了一个催化剂前驱体和催化剂系统,包括所述前驱体,前驱体的一个实施例选自以下结构:其中T是桥接基团;M选自元素周期表的3至7族元素和
镧系元素;Z是配位
配体;每个L是一价、二价或三价阴离子
配体;X和Y各自独立选自氮、氧、
硫和
磷;R是一个与X相对具有相对较低的立体位阻的非臃肿取代基;R′是一个与Y相对具有立体位阻的臃肿取代基。