Controlled Heterometallic Composition in Linear Trinuclear [LnCeLn] Lanthanide Molecular Assemblies.

The combination of two different ß-diketone ligands facilitates the size-controlled assembly of pure heterometallic [LnLn'Ln] linear compounds thanks to two different coordination sites present in the molecular scaffold. [HoCeHo], [ErCeEr], and [YbCeYb] analogues are presented here and are characterized both in the solid state and in solution, demonstrating the selectivity of this unique method to produce heterometallic 4f molecular entities.

Highly Active and Readily Accessible Proline-Based Dizinc Catalyst for CO2 /Epoxide Copolymerization.

In the pursuit of CO2 -based materials, the development of efficient catalysts for the alternating copolymerization of CO2 and epoxides to give polycarbonates is receiving particular attention. Desirable attributes for such catalysts are high copolymerization activity at low CO2 pressure, as well as chemo- and stereocontrol over the formed polymer. Here, we report a novel chiral zinc catalyst that can be isolated in 97 % yield from commercial sources, and that produces polycarbonates selectively from neat cyclohexene oxide under 1 bar of CO2 pressure at temperatures above 50 °C. At 80 °C reaction temperature, TONs of 1684 and initial TOFs up to 149 h-1 were measured, producing an isotactic-enriched polycarbonate with a probability Pm of 65 % for the formation of a meso diad. Insight into the dinuclear nature of the active species and the copolymerization progress has been gained from structural and spectroscopic studies.

Linear or cyclic clusters of Cu(II) with a hierarchical relationship.

The polydentate ligand 2,6-bis(5-(2-hydroxyphenyl)-pyrazol-3-yl)-pyridine, H4L, exhibits a series of coordination pockets favoring the establishment of metal sequences with predetermined motifs, together with a degree of flexibility for the formation of clusters with various overall topologies. With Cu(II) under strong basic conditions it has a marked tendency to stabilize a cyclic [Cu16L8] cluster. The sequential formation of this compound via [Cu7L8](2-) intermediates, recognized in its structure, is suggested by crystallographic evidence, which shows the persistent formation of the complex salt (NBu4)2[Cu7L8] in the presence of the organic cation. Also, the crystallographic identification of the related cluster [Cu11L5(OH)2(py)12] from similar reaction conditions underscores the rich multiplicity of species attainable from this simple reaction system.