A series of new zirconium dichloride complexes bearing bulky cis-bis (amino) cyclodiphosph(III) azane ligands, [(RN)(2)-(tBuNP)(2)]ZrCl2 [R = phenyl (7), diphenylmethyl (8), 2,6-diethylphenyl (9), 2,5-di-tert-butylphenyl (10), and 2,6-diisopropylphenyl (11)] were prepared in high yields by a two-step synthetic route. The structure of cis-[(Ph2CHN)-(tBuNP)](2)Zr(NMe2)(2) (8a), determined by X-ray analysis, shows that the zirconium atom has a distorted trigonal-bipyramidal configuration consisting of four equidistant metal-amido nitrogen bonds and an additional coordination between the metal and a nitrogen atom from the cyclodiphosph(III)azane ring. After methylaluminoxane activation, these complexes exhibit moderate to high activities in ethene polymerization and produce high molar mass polyethene (M-w up to 1100 kg/mol). Polymerization experiments reveal that the behavior of his (amido) cyclodiphosph(III) azane-based Zr-IV catalysts depends on the nature and steric bulkiness of the amido substituents, reaction temperature, MAO/zircomurn ratio, as well as monomer pressure.
Fields of Science
- 116 Chemical sciences