A Joint Experimental/Theoretical Investigation of the Statistical Olefin/Conjugated Diene Copolymerization Catalyzed by a Hemi‐Lanthanidocene [(Cp*)(BH₄)LnR]

Abstract

Statistical copolymerization of ethylene and isoprene was achieved by using a borohydrido half-lanthanidocene complex. Under copolymerization conditions, activation of [(Cp*)(BH(4))(2)Nd(thf)(2)] (Cp*=η(5)-C(5)Me(5)) by an appropriate alkylating agent affords trans-1,4-poly-isoprene-co-ethylene. Analysis of the microstructure of the copolymer revealed the presence of successive short sequences of ethylene/ethylene, trans-1,4-isoprene/ethylene, and trans-1,4-isoprene/trans-1,4-isoprene. A small amount of 1,2-insertion of isoprene was observed, and no cyclic structures within the chain were characterized. Test runs showed that these catalysts are unable to copolymerize α-olefins (such as hex-1-ene) with isoprene. The probable initial steps in the copolymerization have been computed at the DFT level of theory. Analysis of the energy profile provides insight into the catalyst's activity and selectivity. Our theoretical results highlight the key role played by the allyl intermediate, in which diene insertion, and to a lesser extent olefin insertion, is the rate-determining step of the process. These results also illustrate the coordination behavior of the allyl ligand during the insertion of an incoming monomer, which directly inserts, after pre-coordination to the metal center, into the η(3)-allyl ligand without inducing an η(3) to η(1) haptotropic shift. Finally, the inactivity of this family of catalysts towards the copolymerization of hex-1-ene was rationalized on the basis of the free-energy profile of the copolymerization.

Trans‐1,4‐stereospecific copolymerization of ethylene and isoprene catalyzed by MgCl2‐supported Ziegler–Natta catalyst

“…More recently, ethylene–isoprene copolymerization with half‐metallocene and nonmetallocene organometallic catalysts have been reported . Rare‐earth organometallic catalysts have been found to be capable of catalyzing ethylene/conjugated diene copolymerizations, but the products usually contain higher conjugated diene units than ethylene . There have been no literature reports on ethylene/conjugated diene copolymerizations catalyzed by supported Ziegler–Natta catalysts or supported metallocene catalysts that are currently used in industrial production of polyethylene resins.…”

Grafting of Lanthanum Complexes on a Functionalized Graphene Surface: Theoretical Investigation on Ethylene and 1,3‐Butadiene Homo‐ and Co‐Polymerization

“…In view of their stronger Lewis acidity,t herefore, we expected graphene-supported La complexes to act as active polymerization catalysts and we decided to study their catalytic activity in the homo-a nd co-polymerization of ethylene and 1,3-butadiene. [58,[68][69][70][71][72] Ethylenep olymerization…”

“…Lanthanide-based molecular complexes, finally,a lso lead to the formation of mainly 1,4-cis polybutadiene polymers,m olecular catalysts showing both high activity and trans-1,4-selectivity being rathers carce. [68,69,72,73] Ethylene 1,3-butadiene co-polymerization…”

Precisely Controlled Polymerization of Styrene and Conjugated Dienes by Group 3 Single‐Site Catalysts

“…Lowering the reaction temperature ( T =−10 °C) made the polymerization more controllable and the cis ‐1,4‐selectivity increased to 97.2 % and molecular weight distribution down to 1.7 . The DFT calculations revealed that catalytic activity and stereoselectivity on the ternary system were controlled by kinetic favorable transition state of intermediate formed by initiator and monomer . In 2009, Hou and co‐workers reported a series of scandium dialkyl complexes: Cp′Sc(CH 2 SiMe 3 ) 2 (THF) (Cp′=C 5 H 5 ( 61 ), C 5 MeH 4 ( 62 ), C 5 Me 4 H ( 63 ), C 5 Me 5 ( 64 ), C 5 Me 4 SiMe 3 ( 4 Sc )) and CGC complexes, (C 5 Me 4 R)Sc(CH 2 SiMe 3 ) 2 (R=CH 2 CH 2 PPh 2 ( 65 ), C 6 H 4 OMe‐ o ( 22 )) .…”