Synthesis, characterization and X-ray structures of enatiopure-diamine zinc(II) complexes as pre-catalysts for stereoselective production of poly(rac-lactide)

Synthesis, structures, and catalytic efficiency in ring opening polymerization of rac-lactide with tridentate vs. bidentate cobalt(ii), zinc(ii), and cadmium(ii) complexes containing N-substituted N,N-bis((3,5-dimethyl-1H-pyrazol-1-yl)methyl)amine ligands

“…Polymerization results indicated that the preference for heterotactic bias was relatively low when the reaction temperature was 25 C (P r ¼ 0.51-0.82 at 25 C, Table 2), which is consistent with our previously published ndings. 86,87 However, a drop in reaction temperature from 25 to À25 C resulted in increased heteroselectivity (P r ¼ 0.68-0.94). Polymerization data further revealed that the L B -containing complexes bearing the isopropylaniline moiety (i.e., [L B MCl 2 ]/MeLi) afforded superior heteroselectivities at 25 C to their L A -containing counterparts (Table 2).…”

“…These ndings are in good agreement with the results of our previously published studies. 50,86,87 The catalytic activity of the Zn(II) system in the context of rac-LA polymerization are comparable with those reported by our group for dimethyl Zn(II) complexes, but use of the hereby developed system yielded PLAs with higher heterotacticity than we reported at 25 C. 87 In comparison with the previously reported Zn(II) system bearing N,N 0 ,N-bis((1H-pyrazol-1-yl)methyl)amines derivatives as ligands (P r ¼ 0.95 at À50 C with 90% conversion), the current system exhibited higher activity and comparable heteroselectivity (97% conversion with P r ¼ 0.94 at À25 C). 49 Moreover, in comparison with the complexes of the tetradentate N,N,N,N-bis(pyrazolyl)methane ligand with Zn(II) and Fe(II) (P r ¼ 0.79) used as catalysts, 88 our system exhibited superior activity and stereoselectivity (P r ¼ 0.94).…”

Complexes of Zn(II) and Сu(II) with the Amino Derivatives of Deoxycholic Acid: Syntheses, Structures, and Properties

“…The τ 4 parameter characterizing the geometry of the coordination polyhedron (coordination number 4) is equal to 0.91 [14]. The values of the Zn-N and Zn-Cl bond lengths and bond angles in complex I are comparable with similar values in the Zn(II) complexes with the aliphatic diamine derivatives [15][16][17][18][19][20]. In a molecule of complex I, the steroid fragment consists of fused alicycles (three six-membered (А, B, С) and one fivemembered).…”

Polymerization of rac‐Lactide Using Zinc(II) and Copper(II) Complexes of N1,N1‐Dimethyl‐N2‐[(1R)‐Myrtenylmethyl]Ethane‐1,2‐Diamine

“…The non‐toxic and bioassimilable nature of PLAs to living tissue has prompted the need for catalysts based on biocompatible and environmentally benign metals for their synthesis via ROP. In this context, Zn(II) complexes reported by our group and others polymerized rac ‐LA in a controlled and stereoselective manner. Similarly, copper complexes, due to their high electron transfer ability, moderate Lewis acidity, biocompatibility, and stability in the presence of reactive intermediates, are gaining attention as catalysts for ROP of LA.…”