Palladium complexes containing imino phenoxide ligands: synthesis, luminescence, and their use as catalysts for the ring-opening polymerization of rac-lactide

Abstract

The preparation, structural characterization, luminescence, and catalytic activity of three palladium(II) complexes bearing imino phenoxide ligands are reported. The X-ray studies revealed that the complexes are mononuclear with palladium centres coordinated in a square-planar coordination environment. Two of the complexes are emissive in solution at room temperature. The catalytic activities towards the ring-opening polymerization of rac-lactide (rac-LA) were tested. Polymers with moderate molecular weights and relatively broad dispersity (Ð) were obtained. Kinetic studies revealed that the polymerization followed first-order kinetics.Graphical abstract Electronic supplementary materialThe online version of this article (10.1007/s00706-017-2119-1) contains supplementary material, which is available to authorized users.

Recent Trends in Catalytic Polymerizations

“…The development of the ROP of lactones saw a large surge in popularity in the 1990s with the growing public awareness of environmental issues and rising prices of petroleum (Scheme ). The periodic table in Figure highlights any element that bonds or coordinates with an active site for lactone polymerization, and illustrates the massive number of catalysts reported for the ring opening polymerizations of lactones. ,− The most commonly used metals are zinc, aluminum, tin, yttrium, and lanthanides. New metal catalysts providing higher polymerization rates at lower loadings, while maintaining molecular weight and stereocontrol are continuously being reported. ,− Additionally, the development of highly active catalysts has enabled the polymerization of novel monomers, like (un)­substituted butyrolactones, that can be easily depolymerized, opening up new possibilities for fully recyclable polymeric systems. − …”

“…Elements with catalytic activity for the ROP of lactones (colored), including metals (orange) and nonmetals (green). Gray lettering designates synthetically prepared elements. ,− …”

The preparation of new palladium (II) complexes with Schiff base type ligands and its impregnated Al2O3 materials: As the catalysts for degradation/reduction of organic dyes

“…The PdO and PdN distances of 1.988(5) and 2.025(6) Å [2.003(6) and 2.053(6) Å] in C2 and of 1.9910(17) and 2.0329(19) Å in C3 are comparable with those observed in the other closely related Pd (II) complexes with N 2 O 2 Schiff base ligands. [ 36–40 ]…”

Structural, Luminescent and Thermal Properties of Heteronuclear PdII–LnIII–PdII Complexes of Hexadentate N2O4 Schiff Base Ligand

“…The absorption spectra of the synthesized Pd II –Ln III –Pd II complexes with H 4 L are characterized by two absorption maxima in the ultraviolet region between 210–290 nm and an additional small band centered at approximately 375 nm, as shown in Figure S9. The higher-energy bands are attributable to the intra-ligand transitions while the small bands could be assigned to metal-to-ligand charge transfer or a mixture of metal-to-ligand charge transfer and ligand-centered transitions [22,23,24]. No absorption bands due to f-f transitions were observed in the absorption spectra of these compounds due to the fact that the f-f transitions in Ln III ions are very weak [25].…”