Dinuclear Group 4 Metal Complexes Bearing Anthracene-Bridged Bifunctional Amido-Ether Ligands: Remarkable Metal Effect and Cooperativity toward Ethylene/1-Octene Copolymerization.

Two types of bifunctional amido-ether ligands ( and ) with the rigid anthracene skeleton were designed to support dinuclear group 4 metal complexes. All organic ligands and organometallic complexes ( and ; M = Hf, Zr, and Ti) were fully characterized by H and C NMR spectroscopies and elemental analyses. The complex showed two confirmations at room temperature with -symmetry or -symmetry that can inter-exchange, as indicated by VT NMR, while only a -symmetric isomer was observed for complex at room temperature. However, for Zr and Ti analogues, both and complexes exhibited only one conformation at room temperature. The molecular structures of complexes , , and in the solid state were further determined by single-crystal X-ray diffraction, revealing the distances between two metal centers in from 7.138 Å () to 7.321 Å () but a much farther separation in (8.807 Å in -symmetric ). The mononuclear complex (2-CHO-CH-N-CH)Zr(NMe) () was also prepared for control experiments. In the presence of alkyl aluminum (AlEt) as the alkylating agent and trityl borate ([PhC][B(CF)]) as the co-catalyst, all metal complexes were tested for copolymerization of ethylene with 1-octene at high temperature (130 °C). The preliminary polymerization results revealed that the activity was highly dependent upon the nature of metal centers, and showed the highest activity of 9600 kg(PE)·mol (Zr)·h, which was about 17- and 2.2-fold higher than those of and , respectively. Benefitting from both steric proximity and electronical interaction of two metal centers, exhibited significant cooperativity in comparison to and , with regard to activity and molecular weight and 1-octene incorporation of resultant copolymers.