Dizinc Lactide Polymerization Catalysts: Hyperactivity by Control of Ligand Conformation and Metallic Cooperativity

Understanding how to moderate and improve catalytic activity is critical to improving degradable polymer production. Here, di‐ and monozinc catalysts, coordinated by bis(imino)diphenylamido ligands, show remarkable activities and allow determination of the factors controlling performance. In most ca...

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Bibliographic Details
Published in:Angewandte Chemie (International ed.) 2016-07, Vol.55 (30), p.8680-8685
Main Authors: Thevenon, Arnaud, Romain, Charles, Bennington, Michael S., White, Andrew J. P., Davidson, Hannah J., Brooker, Sally, Williams, Charlotte K.
Format: Article
Language:English
Subjects:
Communication
Communications
dinuclear zinc complexes
homogeneous catalysis
Ligands
metal-metal cooperativity
ring-opening polymerization
structure-activity relationship
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Summary:Understanding how to moderate and improve catalytic activity is critical to improving degradable polymer production. Here, di‐ and monozinc catalysts, coordinated by bis(imino)diphenylamido ligands, show remarkable activities and allow determination of the factors controlling performance. In most cases, the dizinc catalysts significantly out‐perform the monozinc analogs. Further, for the best dizinc catalyst, the ligand conformation controls activity: the catalyst with “folded” ligand conformation shows turnover frequency (TOF) values up to 60 000 h−1 (0.1 mol % loading, 298 K, [LA]=1 m), whilst that with a “planar” conformation is much slower, under similar conditions (TOF=30 h−1). Dizinc catalysts also perform very well under immortal conditions, showing improved control, and are able to tolerate loadings as low as 0.002 mol % whilst conserving high activity (TOF=12 500 h−1). Ring‐opening polymerization: Dinuclear and analogous mononuclear zinc complexes embedded in bis(imino)diphenylamido ligands were synthesized and used as catalysts for the ring‐opening polymerization (ROP) of racemic lactide (LA). The catalysts with “folded” ligands show high turnover frequency (TOF) values, which are up to 5500 times higher than those for “flat” ligands (see picture).
ISSN:1433-7851
1521-3773
DOI:10.1002/anie.201602930