Ring‐opening polymerization of rac‐lactide catalyzed by Al(III) and Zn(II) complexes incorporating Schiff base ligands derived from pyrrole‐2‐carboxaldehyde

Abstract

A series of Al(III) chloride [LAl-Cl]; Al(III) alkoxide [LAl-OR] 2 ; and Zn(II) [LZn] 2 complexes with Schiff base ligands were obtained. 1 H NMR and X-ray diffraction studies indicate that [LAl-Cl] complexes have C s symmetry and the Al center is penta-coordinated. The Al(III) alkoxide complex [L 5 Al-O i Pr] 2 is a dimer bridged by O i Pr − with the Al center in a distorted octahedral environment. Zn complexes [LZn] 2 are double helix dimers with tetra-coordinated Zn centers. The catalytic activity for the ring-opening polymerization of rac-lactide was evaluated. The best activity in this series is shown by the aluminium chloride complex with a flexible three-carbon bridge; more flexible four-carbon bridges lower the activity.

Dinuclear Zn(II) and tetranuclear Co(II) complexes of a tetradentate N2O2 Schiff base ligand: Synthesis, crystal structure, characterization, DFT studies, cytotoxicity evaluation, and catalytic activity toward benzyl alcohol oxidation

“…Schiff base ligands contain multiple potential donor sites, which allow them to bind metal ions with diverse coordination geometries such as bidentate and tridentate . Tetradentate Schiff base ligands also provide a suitable coordination platform for metal ions to provide diverse metallic complexes …”

Alkali Blues: Blue‐Emissive Alkali Metal Pyrrolates

“…Alkali metal-ion complexes 1-3 of the 4-tert-butyl phenyl(pyrrol-2-ylmethylene)amine H tBu L [21] were convenientlyo btained by deprotonating the parentl igand with the corresponding alkali metal hexamethyldisilazides MHMDS (M = Li, Na, K; Scheme 2) in acetonitrile or toluene. Lithium derivative 1 crystallizes as ad imer,[ 1(CH 3 CN)] 2 ,w ith ac oordinated acetonitrile molecule when crystallizedf rom CH 3 CN, whereas the sodium and potassium derivatives crystallize as solvent-free polymers [2] [3] n ,s uitable for structure determination by X-ray diffraction( Figure 1), were obtained from concentrated acetonitrile solutions by slow evaporation of the solvent( Supporting Information, Ta bles S1-S4).…”

“…In the last decades, these ligands have attracted considerable attention in several fields of chemistry. For example, they have been applied in transition metal or lanthanide complexes, which are used as homogenous catalysts, especially for polymerization, and as biomimetic and bioinspired complexes [e.g. Mo( t Bu L) 2 O 2 or [Cu( t Bu L)] 2 ; H t Bu L=4‐ tert ‐butyl phenyl(pyrrol‐2‐ylmethylene)amine; Scheme ] .…”

“…2-Iminopyrrolates (L À )a re commonly and successfully employed as ligandsi naplethora of complexes with ab road range of applications. [1][2][3][4] The bidentate N,N'-proligands HL are conveniently prepared by Schiff-base condensation of pyrrole-2-carboxaldehydes with various amines. [4][5][6][7] The first examples of metal complexes with mainly late, bivalent transition metals (Co II ,N i II ,C u II ,Z n II , and Pd II )a rising from this class of ligands were described in the 1960's.…”

“…[4][5][6][7] The first examples of metal complexes with mainly late, bivalent transition metals (Co II ,N i II ,C u II ,Z n II , and Pd II )a rising from this class of ligands were described in the 1960's. [8] In the last decades, these ligands have attracted considerable attention in severalf ields of chemistry.F or example, they have been appliedi nt ransition metal [9][10][11] or lanthanide complexes, [12,13] which are used as homogenous catalysts, [1,[14][15][16][17][18] especially for polymerization, [2,3] and as biomimetic andb ioinspired complexes [e.g. Mo( tBu L) 2 O 2 or [Cu( tBu L)] 2 ;H tBu L = 4-tert-butyl phenyl(pyrrol-2-ylmethylene)amine;S cheme 1].…”