Mononuclear Copper Complexes with Tridentate Tris(N-heterocyclic carbene): Synthesis and Catalysis of Alkyne–Azide Cycloaddition

Cu(triNHC)-catalyzed polymerization of glycidol to produce ultralow-branched polyglycerol

We have successfully synthesized a novel form of polyglycerol with an unprecedentedly low degree of branching (DB = 0.08-0.18), eliminating the need for glycidol protection. Leveraging the remarkable efficiency and selectivity of our Cu(triNHC) catalyst, comprising copper(i) ions and NHC ligands, we achieved a highly selective polymerization process. The proposed Cu-coordination mechanisms presented the formation of linear L1,3 units while effectively suppressing dendritic units. Consequently, our pioneering approach yielded polyglycerol with an ultralow DB and exceptional yields. To comprehensively assess the physical properties and topology of the synthesized polyglycerol, we employed 1H diffusion-ordered spectroscopy, size-exclusion chromatography, and matrix-assisted laser desorption/ionization-time of flight spectrometry. Remarkably, the ultralow-branched cyclic polyglycerol (DB = 0.08) synthesized at 0 °C showcased extraordinary characteristics, exhibiting the lowest diffusion coefficient and the highest molecular weight. This achievement establishes the significant potential of our polyglycerol with a low degree of branching, revolutionizing the field of biocompatible polymers.

[(Flu)-(CH2)2-(NHC)-CH2-(NHC)-(CH2)2-(Flu)]2−: an ‘all-organic’ hybrid and flexible ligand that enwraps a Ca2+ pseudo-tetrahedrally

A conformationally flexible ligand, [(Flu)-(CH2)2-(NHC)-CH2-(NHC)-(CH2)2-(Flu)]2− (L), that offers four sequential organic donor modules and enwraps a Ca2+ pseudo-tetrahedrally in a twisted ‘S’-shape is devised.

Direct Access to Palladium(II) Complexes Based on Anionic C,C,C-Phosphonium Ylide Core Pincer Ligand

The reaction of readily available imidazolium-phosphonium salt [MesIm(CH₂)₃PPh₃](OTf)₂ with PdCl₂ in the presence of an excess of Cs₂CO₃ afforded selectively in one step the cationic Pd(II) complex [(C,C,C)Pd(NCMe)](OTf) exhibiting an LX₂-type NHC-ylide-aryl C,C,C-pincer ligand via formal triple C-H bond activation. The replacement of labile MeCN in the latter by CNtBu and CO fragments allowed to estimate the overall electronic properties of this phosphonium ylide core pincer scaffold incorporating three different carbon-based donor ends by IR spectroscopy, cyclic voltammetry, and molecular orbital analysis, revealing its significantly higher electron-rich character compared to the structurally close NHC core pincer system with two phosphonium ylide extremities. The pincer complex [(C,C,C)Pd(CO)](OTf) represents a rare example of Pd(II) carbonyl species stable at room temperature and characterized by X-ray diffraction analysis. The treatment of isostructural cationic complexes [(C,C,C)Pd(NCMe)](OTf) and [(C,C,C)Pd(CO)](OTf) with (allyl)MgBr and nBuLi led to the formation of zwitterionic phosphonium organopalladates [(C,C,C)PdBr] and [(C,C,C)Pd(COnBu)], respectively.