Abstract
The copolymerization of ethylene (E) with allyl ethyl ether (AEE) by [di(2-dianisyl)phosphine-2-yl]benzenesulfonato Pd(II) as a catalyst is investigated by DFT calculations and compared with the copolymerization of E with diallyl ether (DAE). For AEE, both 1,2- and 2,1-monomer insertions lead to a very stable O-Chelate product (a five-membered and a four-membered ring, respectively) that hinders any further ethylene insertion. As for DAE, a first 2,1-insertion (favored by 1.8 kcal mol vs the 1,2-insertion) leads to the four-membered O-Chelate product that easily evolves to the most stable intermediate with the second DAE C=C bond coordinated to the metal promoting the following 1,2-insertion. The 2,1 + 1,2 DAE insertion product, bearing a five-membered cyclic unit, is stabilized by a β-agostic interaction that easily opens in favor of E coordination and insertion. Based on the proposed copolymerization mechanism, the stereochemistry of the E/DAE copolymer is studied and the experimental microstructure explained. Finally, [di(2-anisyl)phosphine-2-yl]benzenesulfon(methyl)amido Pd(II) species showing a greater regioselectivity toward a first DAE 2,1-insertion (Δ ΔG of -3.6 kcal mol) are suggested to be a promising catalyst.
Original language | English (US) |
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Pages (from-to) | 4525-4531 |
Number of pages | 7 |
Journal | Macromolecules |
Volume | 51 |
Issue number | 12 |
DOIs | |
State | Published - Jun 7 2018 |
Bibliographical note
KAUST Repository Item: Exported on 2020-10-01Acknowledgements: F.P.W. thanks the KAUST visiting student research program for funding of his internship at KAUST. Support by the DFG (Me 1388/10-2) is gratefully acknowledged.