Homoleptic and heteroleptic ketodiiminate zinc complexes for the ROP of cyclic l-lactide

Eduard Glöckler; Leon Kapp; Christoph Wölper; Marcel Schumacher; André H Gröschel; Stephan Schulz

doi:10.1039/d3ra06529d

Homoleptic and heteroleptic ketodiiminate zinc complexes for the ROP of cyclic l-lactide

RSC Adv. 2023 Oct 12;13(43):29879-29885. doi: 10.1039/d3ra06529d. eCollection 2023 Oct 11.

Authors

Eduard Glöckler¹, Leon Kapp¹, Christoph Wölper¹, Marcel Schumacher², André H Gröschel², Stephan Schulz^{1

3}

Affiliations

¹ Faculty of Chemistry, University of Duisburg-Essen Universitätsstraße 7 45141 Essen Germany stephan.schulz@uni-due.de.
² Faculty of Chemistry, University of Münster and Center for Soft Nanoscience (SoN) Busso-Peus-Strasse 10 48149 Münster Germany.
³ Center for Nanointegration Duisburg-Essen (CENIDE) Carl-Benz-Straße 199 47057 Duisburg Germany.

Abstract

Homo- and heteroleptic ketodiiminate zinc complexes L¹₂Zn₂ (1, L¹ = [Me₂NC₂H₄NC(Me)CH]₂CO), L²(ZnCp)₂ (2, L² = [Me₂NC₃H₆NC(Me)CH]₂CO, Cp = C₅H₅) and L²HZnCp* (3, Cp* = C₅Me₅) were synthesized and characterized by ¹H and ¹³C NMR and IR spectroscopy as well as by elemental analysis and single crystal X-ray diffraction (sc-XRD, 2, 3). The catalytical activity of heteroleptic complexes 2 and 3 were tested in the ring-opening polymerization (ROP) of l-lactide. Homobimetallic complex 2 showed the highest activity and selectivity for the synthesis of cyclic polylactide (cPLLA; TOF = 17 460 h^-1) at 100 °C in toluene solution, while linear polymers are formed with mononuclear complex 3.