Cover Feature: “Catch‐Store‐Release” Strategy for the Stabilization of 4,4′‐Methylene Diphenyl Diisocyanate (4,4′‐MDI) (Chem. Eur. J. 30/2023)

Abstract

4,4’‐Methylene diphenyl diisocyanate (4,4’‐MDI) is a key diisocyanate linker in the production of polyurethanes. 4,4’‐MDI is thermally unstable, undergoing dimerization to unreactive and insoluble uretdione. The “catch–store–release” strategy presented in the Research Article by S. Groysman and co‐workers (DOI: 10.1002/chem.202300924) allows 4,4’‐MDI to be stabilized in the form of an imidazolium amidate that is produced by the coordination of two equivalents of N‐heterocyclic carbene. The complex can be released by heating with CuCl (with or without sulfur); this forms a CuI carbene/urea complex and restores MDI. Artwork by the authors with help from Mary Iverson.