Scandium catalysts, olefin polymerization

Group NIB and f-BIOCk Metallocenes. The need for expensive cocatalysts has always hampered the development of metallocene catalysts for olefin polymerization. It was recognized early on that substitution of the Group IVB metal with a lanthanide or Group IIIB element in the -1-3, state would represent a cocatalyst-free analogue of the Kaminsky system. Active catalysts are indeed obtained from bis-Cp lanthanocenes and yttrium- and scandium-based congeners. The lutetium dimer 29 has an activity of >7 kg/mmol(Lu)/h/atm for ethylene polymerization in cyclohexane (95). (This remarkable compound can also break the C—H bonds of alkanes.)... 

P. J. Shapiro, E. E. Bunef W. Schaefer, J. E. Beicaw, Scandium complex [ ((TlLC5Me4)Me2Si(T) -NCMe3) (PMc3)ScH]2 a unique example of a single-component a-olefin polymerization catalyst Organometallics 9, 1990 867. 

Recently Hou reported the first example of efficient COG synthesis by rare earth metal catalysts. Cationic rare earth (group 3 and lanthanide) metal alkyls is an emerging new class of catalysts for the polymerization and copolymerization of various olefins including cyclic olefins. The combination of half-sandwich scandium bis (alkyl) complexes such as... 

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