Abstract
A series of novel half-titanocene complexes CpTiCl2[S-2-R-6-(PPh2)C6H3] (Cp = C5H5, 2a, R = H; 2b, R = Ph; 2c, R = SiMe3) have been synthesized by treating CpTiCl3 with the sodium of the ligands, 2-R-6-(PPh2)C6H3SNa, which were prepared by the corresponding ligands and NaH. These complexes have been characterized by 1H, 13C and 31P NMR as well as elemental analyses. Structures for 2a–b were further confirmed by X-ray crystallography. Complexes 2a–b adopt five-coordinate, distorted square-pyramid geometry around the titanium center, in which the equatorial positions are occupied by sulfur and phosphorus atoms of the chelating phosphine-thiophenolate and two chlorine atoms, and the cyclopentadienyl ring is coordinated on the axial position. The complexes 2a–c were investigated as the catalysts for ethylene polymerization and copolymerization of ethylene with norbornene in the presence of MMAO or Ph3CB(C6F5)4/iBu3Al as the cocatalyst. All complexes exhibited low to moderate activities towards homopolymerization of ethylene. However, they displayed moderate to high activities towards copolymerization of ethylene with norbornene.
Highlights
The development of well-defined, single-site group 4 metal catalysts has attracted much attention for olefin polymerization [1–3]
Nomura et al found that the half-titanocenes containing aryloxo ligands exhibited remarkable catalytic activity in olefin polymerization and efficient comonomer incorporation in ethylene/α-olefin copolymerization [10,29]
Our group found that high-temperature living ethylene/norbornene copolymerization could be achieved by using bis(phenoxy-phosphine)-titanium complexes as the catalysts in the presence of modified methylaluminoxane (MMAO) [43]
Summary
The development of well-defined, single-site group 4 metal catalysts has attracted much attention for olefin polymerization [1–3]. Non-bridged half-sandwich group 4 metal complexes containing anionic ancillary donor ligands have become a hot topic because of their easy modifications and remarkable catalytic activity for olefin (co)polymerization [9–40]. Nomura et al found that the half-titanocenes containing aryloxo ligands exhibited remarkable catalytic activity in olefin polymerization and efficient comonomer incorporation in ethylene/α-olefin copolymerization [10,29]. Gibson and his coworkers reported a series of bis(phosphanylphenoxide) group 4 metal dichloride complexes, and further suggested that the use of ancillary ligands with softer L donors, such as phosphorus and sulfur, might offer beneficial stabilization of the highly reactive metal center [41,42].
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