Diiminopyrrolide copper alkoxide complexes, LCuOR (OR(1)=N,N-dimethylamino ethoxide, OR(2)=2-pyridyl methoxide), are active for the polymerization of rac-lactide at ambient temperature in benzene to yield polymers with M(w)/M(n)=1.0-1.2. X-ray diffraction studies showed bridged dinuclear complexes in the solid state for both complexes. While LCuOR(1) provided only atactic polylactide, LCuOR(2) produced partially isotactic polylactide (P(m)=0.7). The difference in stereocontrol is attributed to a dinuclear active species for LCuOR(2) in contrast to a mononuclear species for LCuOR(1).

We present the high catalytic activity of an in situ generated palladium(II)/metformin complex in neat water for the Suzuki-Miyaura and Sonogashira cross-coupling reactions. These reactions were performed in pure water without any co-solvent or mass transfer agent. The palladium(II)/metformin complex gave excellent to good yields for the Suzuki-Miyaura coupling reaction and catalyzed with a certain specificity to the aryl iodide coupling in the Sonogashira reaction. The methodology showcases a recyclability up to four catalytic runs for the Suzuki-Miyaura cross-coupling reaction, performed with only 0.5 mol% palladium loading.

We report here the synthesis and thorough characterization of a new family of alkylbiguanides and alkylbiguanidium chlorides by 1 H and 13 C NMR and X-ray diffraction. Their critical micelle concentration was first determined by surface tension measurements. Hexylbiguanide was then studied as a surfactant in the micellar Suzuki–Miyaura cross-coupling reaction. The unexpected low reactivity of the system at high Pd/hexylbiguanide ratios was due to the change of the size and the shape of the aggregates, observed by transmission electron microscopy. The best catalytic activity was obtained for a 1:1 Pd/hexylbiguanide ratio for which the micellar conditions were conserved. Better results were obtained for several substrates, when compared to those previously obtained with metformin under the same reaction conditions. Higher yields and a better recyclability were obtained under micellar conditions with hexylbiguanide.

and Nbenzyl (L9, R = H) were reacted with Cu(OMe) 2 and pyridylmethanol (R 1 OH) or dimethylaminoethanol (R 2 OH) to yield the corresponding dinuclear complexes L 2 Cu 2 (μ-OR) 2 . Reactions in the absence of chelating R 1 OH or R 2 OH only yielded homoleptic L 2 Cu or L 2 Cu 2 . Complexes with R 2 OH were obtained with all ligands but L4, complexes with R 1 OH for all ligands but L3, L4, and L6. All complexes but those with L7 displayed dinuclear crystal structures with pentacoordinated copper centers and bridging alkoxy groups. The alkoxy group and the pyrrolide ligand were consistently found in equatorial positions. Imine, pyridine, or amine occupied the axial position. L7 coordinated both imino groups to copper, yielding a distorted-octahedral coordination geometry. All complexes containing R 1 OH, with the exception of L7, showed an isotactic bias in the polymerization of rac-lactide, with a maximum P m value of 0.7. Complexes containing R 2 OH provided atactic PLA or, in the case of L3 and L6, heterotactic PLA. Reduced stereocontrol in monoiminopyrrolide copper complexes and lack of stereocontrol with octahedrally coordinated L7 indicate that the catalytic site needs to adapt to chain-end chirality and is participating in enantiomer selection.