Scandium-catalyzed copolymerization of myrcene with ethylene and propylene: convenient syntheses of versatile functionalized polyolefins†
The copolymerization of myrcene with ethylene and propylene using half-sandwich scandium complexes bearing various auxiliary ligands has been examined. In the copolymerization of myrcene with ethylene, the THF-free aminobenzyl scandium complex bearing a relatively small cyclopentadienyl ligand (C5H5)Sc(CH2C6H4NMe2-o)2 (1) afforded diblock myrcene–ethylene copolymers with a high myrcene content and predominant cis-1,4-structure, whereas the analogous scandium complex with a larger cyclopentadienyl ligand (C5Me4SiMe3)Sc(CH2C6H4NMe2-o)2 (2) afforded multiblock myrcene–ethylene copolymers with different myrcene contents and a predominant 3,4-structure. In contrast, the THF-containing trimethylsilylmethyl scandium complex (C5Me4SiMe3)Sc(CH2SiMe3)2(THF) (3) afforded alternating myrcene–ethylene copolymers on using a sufficient amount of myrcene. More remarkably, the terpolymerization of myrcene with ethylene and propylene has also been realized using a scandium complex 3, yielding a new family of myrcene-based ethylene–propylene–diene rubbers (EPDM) with versatile CC double bonds in the main and side chains. By efficiently transforming the CC double bonds of the resulting myrcene-based EPDM into other polar groups, versatile functionalized polyolefins such as thioacetic acid, sulfoacid, and epoxidized, hydroxylated–chlorinated and furan functionalized polyolefins were obtained.