Lanthanide Complexes Supported by a Trizinc Crown Ether as Catalysts for Alternating Copolymerization of Epoxide and CO₂: Telomerization Controlled by Carboxylate Anions

Abstract

A new family of heterometallic catalysts based on trimetalated macrocyclic tris(salen) ligands and rare-earth metals was prepared and structurally characterized. The LaZn system containing anionic ligands such as acetate plays a critical role in catalyzing the alternating copolymerization of cyclohexene oxide (CHO) and CO with a high proportion of carbonate linkages. Among the lanthanide metals, the CeZn system exhibits high catalytic activity with a turnover frequency (TOF) of over 370 h . NMR analysis of the complex and end-group analysis of the polymer suggest that the acetate ligands are rapidly exchanged, not only among coordinated acetates, but also between coordinated acetates and added carboxylate anions. These unique properties make this the first example of telomerization for the copolymerization of CHO and CO .

Unexpected Macrocyclic Multinuclear Zinc and Nickel Complexes that Function as Multitasking Catalysts for CO2 Fixations

“…In view of the quite unique static and dynamic structures of the Zn II and Ni II complexes 2 and 3,w ed ecided to investigate the latent catalytic activity of 2 and 3.I nt he context of our ongoing research for CO 2 fixations, [13] we tested these metal complexes for the synthesis of cyclic carbonate 7a from CO 2 and epoxide 6a ( Table 1). [14] We screened combinations of 2 or 3 (2 mol %) and tetrabutylammonium halide (TBAX) at 50 8 8Cu nder solvent-free conditions (entries 1-6), expecting that the metal ions and halide anions act as aLewis acid and anucleophile,respectively.The simultaneous use of complex 2 or 3 and TBAI yielded 7a in high yield (73-95 %, entries 3a nd 6). Ther eaction did not proceed significantly in the presence of either metal complex alone or TBAI alone (entries 7and 8).…”

Izatt‐Christensen Award: L. De Cola / Cram Lehn Pedersen Prize: X. Li / Humboldt Research Award: K. Mashima

“…Mashima's recent research includes asymmetric hydrogenation and allylic alkylation reactions as well as selective transesterification and amide alcoholysis processes. The results of a cooperative venture of Mashima's group and Jun Okuda's group at RWTH Aachen (Germany), on lanthanide complexes supported by a trizinc crown ether as catalysts for the copolymerization of epoxides and CO 2 , were recently published in a Communication in Angewandte Chemie …”

Izatt‐Christensen‐Preis: L. De Cola / Cram‐Lehn‐Pedersen‐Preis: X. Li / Humboldt‐Forschungspreis: K. Mashima

“…Mashimas jüngere Forschung umfasst asymmetrische Hydrierungen und allylische Alkylierungen sowie selektive Umesterungen und Amidalkoholysen. Über die Ergebnisse einer Kooperation von Mashimas Gruppe mit der Gruppe von Jun Okuda (RWTH Aachen) zu Lanthanoidkomplexen eines Trizink‐Kronenethers als Katalysatoren für die Kopolymerisation von Epoxiden mit CO 2 war in einer Zuschrift in der Angewandten Chemie zu lesen …”