Novel Rare Earth Complexes And The Catalytic Activity In The Polymerization Of Conjugated Olefins

Investigation of novel rare earth complexes and the catalytic characteristics in the polymerization of conjugated olefins is an important subject in polymer synthesis. Conjugated dienes (butadiene, Bd; isoprene, Ip) and styrene (St) are important monomers in the polymerization of conjugated olefins. Because of the multiple units in the corresponding homo/copolymers with random distribution, the polymers exhibit excellent properties such as good behavior at low temperature, high traction, low abrasion and wear. St/Ip/Bd terpolymer rubber (SIBR) is considered to be the integral rubber with comprehensive characters. Bd/St copolymer rubber (SBR) occupies the largest output in synthetic rubber. Raising the content of cis1,4-and St in random copolymers is very crucial to enhance the elasticity and wear properties. Herein, we prepared a series of novel rare earth catalyst/MAO and rare earth catalyst/borate systems, giving random rare earth SBR with high cis1,4-and St content, as well as novel random rare earth SIBR and rare earth isoprene-butadiene copolymer rubber (IBR) with unique sequences of both cis l,4-polybutadiene(PB) and3,4-polyisoprene(PI) units. Moreover, the catalytic characteristics of Cp ligated rare earth carbene/methylidene was also explored.Research contents are as follows:1. The study showed that random rare earth SBR with high content of St and cis1,4-units were prepared with neodymium phosphate compound(Nd(P507)3)/MAO/Indene system. The catalyst system showed high activity in the copolymerization even at low MAO amount. The polymerization activity and regio/stereoselectivity could be controlled by changing the molar ratio of catalyst components and polymerization conditions. The cis1,4-content increased from34.4%to73.3%; the St content could be controlled in a wide range (～33.0%); the molecular weight distributions were narrow(MwMn:1.4～2.1).2. With isopropoxide neodymium(Nd(O’Pr)3)/MAO/Indene system, random rare earth SIBR with high content of St and cis1,4-structure were prepared. The catalyst system showed high activity in the terpolymerization even at low MAO amount. When varying the molar ratio of catalytic systems and polymerization conditions, the cis1,4-content increased from54.7%to82.3%; the St content could be controlled in a wide range (-30.4%); the molecular weight distributions were narrow(Mw/Mn:1.5-2.2).3. The reaction of2,6-’Pr2C6H3N(H)PPh2(HL) with equivalent rare earth trialkyl complexes Ln(CH2C6H4NMe2-o)3(Ln=Sc, Y, Lu), afforded a series of novel non-Cp ligated and non-solvent coordinated rare earth dialkyl complexes, LLn(CH2C6H4NMe2-o)2(Ln=Sc (3-1), Y (3-2), Lu (3-3)). LLn(CH2C6H4NMe2-o)2/[Ph3C][B(C6F5)4] systems showed high activity and excellent regio/stereoselectivity in the homo/copolymerization of Bd and Ip. This catalyst system exhibited high cis,4-selectivity of57.0%-82.4%in the homopolymerization of Bd and high3,4-selectivity of93.5%-98.2%in the homopolymerization of Ip; IBR with high content of cis1,4-PB and3,4-PI sequences were prepared; comparing with complex3-3,3-1and3-2showed higher cis1,4-selectivity toward PB sequence.4. The protonation of Cp’4Lu4(μ3-CH2)4(3-5) with [PhMe2NH][B(C6F5)4] generated cubane-type cationic Cp ligated rare earth carbene/methylidene complex,[Cp’4Lu4(μ3-CH2)3(μ3-Me)][B(C6F5)4](3-13). The catalytic activity and regio/stereoselectivity in the olefin polymerization were also examined. The results showed that3-13exhibited high catalytic activity and excellent regio/stereoselectivity. The unique reactivity of3-5toward unsaturated C—0, C—N, C—S bonds were also examined, as well as the reactivity in the hydrogenolysis and protonation reactions.The complexes were characterized with X-Ray single crystal diffraction, NMR and elemental analysis. The polymers were characterized with NMR, FTIR, GPC and DSC.