Polymerizations of methyl methacrylate and <i>rac</i>-lactide by zinc(II) precatalyst containing <i>N</i>-substituted 2-iminomethylpyridine and 2-iminomethylquinoline
Creators: name: Heo, Joung
name: Hyosun Lee
name: Saira Nayab
Publisher: name: Taylor & Francis
Year: 2017
Subjects: subject: Biophysics
subject: Biochemistry
subject: Microbiology
subject: FOS: Biological sciences
subject: FOS: Biological sciences
subject: Cell Biology
subject: Genetics
subject: Molecular Biology
subject: Pharmacology
subject: Biotechnology
subject: 39999 Chemical Sciences not elsewhere classified
subject: FOS: Chemical sciences
subject: FOS: Chemical sciences
subject: Plant Biology
subject: 60506 Virology
subject: Computational Biology

description: The reaction of <b>[ZnCl</b><sub><b>2</b></sub><b>]</b> with <i>N</i>-cyclopentyl-1-(quinolin-2-yl)methanimine (<b>L</b><sub><b>A</b></sub>), <i>N</i>-cyclohexyl-1-(quinolin-2-yl)methanimine (<b>L</b><sub><b>B</b></sub>), <i>N</i>-cyclohexyl-1-(pyridin-2-yl)methanimine (<b>L</b><sub><b>C</b></sub>), 2,6-diethyl-<i>N</i>-(pyridin-2-ylmethylene)aniline (<b>L</b><sub><b>D</b></sub>), <i>N</i>-cyclopentyl-1-(pyridin-2-yl)methanimine (<b>L</b><sub><b>E</b></sub>), and <i>N</i>-phenyl-(pyridin-2-yl)methanimine (<b>L</b><sub><b>F</b></sub>) in ethanol produced the bidentate <b>[(<i>NN</i>′)ZnCl</b><sub><b>2</b></sub><b>]</b> complexes, <b>[L</b><sub><b>A</b></sub><b>ZnCl</b><sub><b>2</b></sub><b>]</b>, <b>[L</b><sub><b>B</b></sub><b>ZnCl</b><sub><b>2</b></sub><b>]</b>, <b>[L</b><sub><b>C</b></sub><b>ZnCl</b><sub><b>2</b></sub><b>]</b>, <b>[L</b><sub><b>D</b></sub><b>ZnCl</b><sub><b>2</b></sub><b>]</b>, <b>[L</b><sub><b>E</b></sub><b>ZnCl</b><sub><b>2</b></sub><b>]</b> and <b>[L</b><sub><b>F</b></sub><b>ZnCl</b><sub><b>2</b></sub><b>]</b>, respectively. The molecular structures revealed that the zinc in <b>[L</b><sub><b>n</b></sub><b>ZnCl</b><sub><b>2</b></sub><b>]</b> (L<sub>n</sub> = L<sub>A</sub> − L<sub>D</sub>) showed a distorted tetrahedral geometry involving two nitrogens of <i>N,N’</i>-bidentate ligands and two chloride ligands. Most of these initiators were effective for polymerization of methyl methacrylate (MMA) and polymerization of rac-lactide (<i>rac</i>-LA). <b>[L</b><sub><b>C</b></sub><b>ZnCl</b><sub><b>2</b></sub><b>]</b> (with <i>N</i>-cyclohexyl substituted at imine-pyridine moiety) exhibited the highest catalytic activity for MMA polymerization in the presence of modified methylaluminoxane (MMAO) with an activity of 3.33 × 10<sup>4</sup> g PMMA/mol·Zn·h at 60 °C, giving moderate syndiotactic poly methyl methacrylate (PMMA) with high molecular weight (9.62 × 10<sup>5</sup> g/mol). The dimethyl derivatives <b>[L</b><sub><b>n</b></sub><b>ZnMe</b><sub><b>2</b></sub><b>]</b> (L<sub>n</sub> = L<sub>A</sub> − L<sub>F</sub>), generated <i>in situ</i>, polymerized <i>rac</i>-LA with moderate activity and yielded a polylactide (PLA) with good number-average molecular weights and narrower polydispersity indices (PDIs). <b>[L</b><sub><b>A</b></sub><b>ZnMe</b><sub><b>2</b></sub><b>]</b> effectively initiates the ring-opening polymerization (ROP) of <i>rac</i>-LA to attain heterotactic PLA (<i>P</i><sub>r</sub> = 0.91).