Synthesis, Characterization of Zinc Complexes with Neutral ?-Diimine Ligands and Application in Ring-opening Polymerization of ?-Caprolactone

Abstract

A series of neutral α-diimine ligands with diacetyl and acenaphthenequinone skeletons were prepared by the reaction between diacetyl and the corresponding aromatic amine. These ligands reacted with ZnCl2 to generate symmetric α-diimine zinc complexes C1-C10. Experimental results indicated that the α-diimine zinc complexes with a diacetyl skeleton (C1-C4) were active in ring-opening polymerization (ROP) of ε-caprolactone (ε-CL). The complexes with an acenaphthenequinone skeleton showed a small steric effect (C5, C8 and C9) but the complex substituted with an electron-withdrawing group (C10) showed high activity in the monomer conversion rate during ROP of ε-CL. The ROP catalysts of ε-CL demonstrated the mechanism of monomer activation in the presence of benzyl alcohol.

Zinc 8-aminotrihydroquinolines appended with pendant N-diphenylphosphinoethyl arms as exceptionally active catalysts for the ROP of ε-CL

“…As a general point, it should be emphasized that these tri-component zinc catalysts, comprising Zn /2LiN(SiMe 3 ) 2 /BnOH, are to the knowledge of the authors among the most active reported for the zinc-mediated ROP of ε-CL. 57…”

“…As a general point, it should be emphasized that these tricomponent zinc catalysts, comprising Zn/2LiN(SiMe 3 ) 2 /BnOH, are to the knowledge of the authors among the most active reported for the zinc-mediated ROP of ε-CL. 57 Given the exceptionally high activity displayed by Zn1-Zn5 for the ROP of ε-CL following pre-treatment with LiN(SiMe 3 ) 2 , we were interested in the role played by the diphenylphosphino group in the polymerization. As noted earlier, the molecular structures of procatalysts Zn2 and Zn5 indicated that the diphenylphosphino group in each case was not coordinated to the metal center.…”

Zinc complexes bearing BIAN ligands as efficient catalysts for the formation of cyclic carbonates from CO2 and epoxides

“…24–26 Despite its common use for the past three decades as intermediates to obtain the aryl-BIAN ligands, other applications of the Zn( ii ) aryl-BIAN complexes were scarce and limited to photosynthesizers 27 or catalysts in the ROP reaction of ε-caprolactone. 28–30…”