Synthesis and Olefin Polymerization Catalysis of New Divalent Samarium Complexes with Bridging Bis(cyclopentadienyl) Ligands

Abstract

This paper deals with the preparation and olefin polymerization catalysis of six new divalent samarium complexes. These bridged bis(cyclopentadienyl) (Cp) complexes exhibit various structures with regard to the bridging group and the position of substituents on the Cp rings: rac-tBu, Me2Si(2-Me3Si-4-tBuC5H2)2Sm(THF)2 (7); rac-tBuMe2Si, Me2Si(2-Me3Si-4-tBuMe2SiC5H2)2Sm(THF)3 (8); C 1 symmetric, Me2Si[2,4-(Me3Si)2C5H2][3,4-(Me3Si)2C5H2]Sm(THF)2 (9); meso, [1,2-(Me2Si)(Me2SiOSiMe2)](3-tBuC5H2)2Sm(THF)2 (10); C 2 v symmetric (Ph2Si), Ph2Si[3,4-(Me3Si)2C5H2]2Sm(THF)2 (11); C 2 v symmetric [(SiOSi)2], [1,2-(Me2SiOSiMe2)2](3-tBuC5H2)2Sm(THF)2 (12). The structures of 7, 8, 10, and 12 were confirmed by X-ray crystallographic analysis. Among these divalent complexes, meso type complex 10 showed the highest activity for polymerizations of ethylene (5 × 105 g of PE/(mol h)) and C 1-symmetric 9 afforded the highest molecular weight of polyethylene (M n = 145 × 104). Only racemic complexes 7 and 8 could polymerize 1-olefins such as 1-pentene and 1-hexene, giving highly isotactic polymers. Moreover, rac-7 induces catalytic cyclopolymerization of 1,5-hexadiene to give poly(methylene-1,3-cyclopentane).

The synthesis and X-ray structure of a phenoxyimine catalyst tailored for living olefin polymerisation and the synthesis of ultra-high molecular weight polyethylene and atactic polypropylene

“…After Doi's pioneering contributions, different metal complexes were used as catalysts for living olefin polymerisation, including bridged lanthanide cyclopentadienyl complexes [15][16][17][18], cobalt half sandwich complexes [19,20], niobium diene complexes [21] and nickel-a-diimine complexes [22]. Yasuda et al managed to synthesise block copolymers of ethylene and polar comonomers in which the polymerisation mechanism changes during the reaction [23].…”

Stereospecific Olefin Polymerization Catalyzed by Metallocene Complexes

“…It is interesting that achiral monocyclopentadienylaryloxyyttrium 10 gives isotactic polymerization of hexene ([mmmm]>85%), presumably by chain-end control [53]. Divalent ansa-samarocene analogues, on the other hand, exhibited poor activity, albeit with high isotacticity ([mmmm]>0.95) [54].…”

New approach to block copolymerization of ethylene with polar monomers by the unique catalytic function of organolanthanide complexes

“…5 Here we have explored the block and random copolymerizations of ethylene with various kinds of polar monomers, such as alkyl methacrylates, CL, and cyclic carbonates. As a result of polymerizations, the block copolymerization of ethylene with MMA proceeded successfully, affording the desired copolymer along with a homopoly(MMA) after quenching the reaction mixture with excess methanol [Eq.…”

“…5 Complex 2 exhibits only a low catalytic activity. Therefore we have explored the removal of coordinated THF by dissolving complex 2 (purple color) into toluene, followed by heating to 100°C under reduced pressure, which results in the formation of complex 2b as a green complex.…”