Mechanistic Studies of ε-Caprolactone Polymerization by (salen)AlOR Complexes and a Predictive Model for Cyclic Ester Polymerizations. Marlier, E. E., Macaranas, J. A., Marell, D. J., Dunbar, C. R., Johnson, M. A., DePorre, Y., Miranda, M. O., Neisen, B. D., Cramer, C. J., Hillmyer, M. A., & Tolman, W. B. ACS Catalysis, 6(2):1215-1224, 2016.
Mechanistic Studies of ε-Caprolactone Polymerization by (salen)AlOR Complexes and a Predictive Model for Cyclic Ester Polymerizations [link]Paper  doi  abstract   bibtex   
Aluminum alkoxide complexes (2) of salen ligands with a three-carbon linker and para substituents having variable electron-withdrawing capabilities (X = NO2, Br, OMe) were prepared, and the kinetics of their ring-opening polymerization (ROP) of ε-caprolactone (CL) were investigated as a function of temperature, with the aim of drawing comparisons to similar systems with two-carbon linkers investigated previously (1). While 1 and 2 exhibit saturation kinetics and similar dependences of their ROP rates on substituents X (invariant Keq, similar Hammett ρ = +1.4(1) and 1.2(1) for k2, respectively), ROP by 2 was significantly faster than for 1. Theoretical calculations confirm that, while the reactant structures differ, the transition state geometries are quite similar, and by analyzing the energetics of the involved distortions accompanying the structural changes, a significant contribution to the basis for the rate differences was identified. Using this knowledge, a simplified computational method for evaluating ligand structural influences on cyclic ester ROP rates is proposed that may have utility for future catalyst design.
@article{doi:10.1021/acscatal.5b02607,
  abstract = { Aluminum alkoxide complexes (2) of salen ligands with a three-carbon linker and para substituents having variable electron-withdrawing capabilities (X = NO2, Br, OMe) were prepared, and the kinetics of their ring-opening polymerization (ROP) of ε-caprolactone (CL) were investigated as a function of temperature, with the aim of drawing comparisons to similar systems with two-carbon linkers investigated previously (1). While 1 and 2 exhibit saturation kinetics and similar dependences of their ROP rates on substituents X (invariant Keq, similar Hammett ρ = +1.4(1) and 1.2(1) for k2, respectively), ROP by 2 was significantly faster than for 1. Theoretical calculations confirm that, while the reactant structures differ, the transition state geometries are quite similar, and by analyzing the energetics of the involved distortions accompanying the structural changes, a significant contribution to the basis for the rate differences was identified. Using this knowledge, a simplified computational method for evaluating ligand structural influences on cyclic ester ROP rates is proposed that may have utility for future catalyst design. },
  added-at = {2016-02-08T10:18:20.000+0100},
  author = {Marlier, Elodie E. and Macaranas, Joahanna A. and Marell, Daniel J. and Dunbar, Christine R. and Johnson, Michelle A. and DePorre, Yvonne and Miranda, Maria O. and Neisen, Benjamin D. and Cramer, Christopher J. and Hillmyer, Marc A. and Tolman, William B.},
  biburl = {http://www.bibsonomy.org/bibtex/27c9dede3676545773bd673661bbd5b94/sasha-markov},
  description = {Mechanistic Studies of ε-Caprolactone Polymerization by (salen)AlOR Complexes and a Predictive Model for Cyclic Ester Polymerizations - ACS Catalysis (ACS Publications)},
  doi = {10.1021/acscatal.5b02607},
  eprint = {http://dx.doi.org/10.1021/acscatal.5b02607},
  interhash = {865a17ff34a276d65fc495f64ced0715},
  intrahash = {7c9dede3676545773bd673661bbd5b94},
  journal = {ACS Catalysis},
  keywords = {catalysis},
  number = 2,
  pages = {1215-1224},
  timestamp = {2016-02-08T10:18:20.000+0100},
  title = {Mechanistic Studies of ε-Caprolactone Polymerization by (salen)AlOR Complexes and a Predictive Model for Cyclic Ester Polymerizations},
  url = {/brokenurl#         http://dx.doi.org/10.1021/acscatal.5b02607    },
  volume = 6,
  year = 2016
}
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