Redox‐ and NIR‐Active Iron(III) Triradicals as Catalysts for Radical Polymerization of Acrylamides and Methacrylates

Abstract

Abstract Two unprecedented redox‐active, low‐spin Fe(III)‐triradical complexes, [Fe(III)(SS‐NHC═S •− ) 3 ]·NHC═S ( 1 ·NHC═S; E═S) and [Fe(III)(SS‐NHC═Se •− ) 3 ] ( 2 ; E═Se) have been synthesized and structurally characterized by SCXRD. They were further characterized spectroscopically using IR, Raman, EPR, and UV–vis‐NIR spectroscopy. The low‐spin electronic configuration of the central Fe(III) ion ( 1 ) and the nature of the magnetic interaction between the Fe(III) center and the three unpaired electrons in 1 have been investigated by magnetic measurements. In addition, the bonding stability and electron density distribution in 1 were studied by quantum chemical calculations and correlated with experimental results. Finally, a series of well‐defined functional homopolymers were synthesized via catalytic polymerization reactions using [Fe(III)(SS‐NHC═S •− ) 3 ] ( 1 ) as a catalyst at ambient temperature. These reactions yielded poly( N , N ‐dimethylacrylamide) (PDMA), poly( N ‐isopropyl acrylamide) (PNIPAM), poly(dimethyl amino ethyl methacrylate) (PDMAEMA), and poly(benzyl methacrylate) (PBzMA) with low dispersities ranging from 1.2 to 1.22. The successful synthesis of various diblock copolymers confirmed excellent chain‐end fidelity of the synthesized homopolymers. These homopolymers and diblock copolymers highlight the versatile catalytic polymerization reactions of these Fe‐radical complexes. Herein, we present a report on the polymerization of various acrylamides and methacrylates using a redox‐active Fe‐dithiolene complex for the first time.