CO2 and SnII Adducts of N‐Heterocyclic Carbenes as Delayed‐Action Catalysts for Polyurethane Synthesis
- 6 March 2009
- journal article
- research article
- Published by Wiley in Chemistry – A European Journal
- Vol. 15 (13), 3103-3109
- https://doi.org/10.1002/chem.200802670
Abstract
Catalytic rivals: Both CO2-protected tetrahydropyrimidin-2-ylidene-based N-heterocyclic carbenes (NHCs) and SnII-1,3-dimesitylimidazol-2-ylidene, as well as SnII-1,3-dimesitylimidazolin-2-ylidene complexes (example displayed), have been identified as truly latent catalysts for polyurethane (PUR) synthesis rivaling all existing systems both in activity and latency. A series of CO2-protected pyrimidin-2-ylidenes as well as 1,3-dimesitylimidazol-2-ylidene and dimesitylimidazolin-2-ylidene complexes of SnII have been prepared. Selected single-crystal X-ray structures are reported. The new compounds were investigated for their catalytic behavior in polyurethane (PUR) synthesis. All compounds investigated showed excellent catalytic activity, rivaling the industrially most relevant catalyst dibutyltin dilaurate. Even more important, all compounds displayed pronounced latent behavior, in selected cases rivaling and exceeding the industrially relevant latent catalyst phenylmercury neodecanoate both in terms of latency and catalytic activity. This allows for creating one-component PUR systems with improved pot lifetimes. Pseudo-second-order kinetics were found for both CO2-protected tetrahyropyrimidin-2-ylidenes and for [SnCl2(1,3-dimesityldihydroimidazol-2-ylidene)], indicating a fast pre-catalyst decomposition prior to polyurethane formation. 1,3-Di(2-propyl)tetrahydropyrimidin-2-ylidene was additionally found to be active in the cyclotrimerization of various isocyanates, offering access to a broad variability in polymer structure, that is, creating both urethane and isocyanurate moieties within the same polymer.Keywords
This publication has 20 references indexed in Scilit:
- Zwitterionic Polymerization of Lactide to Cyclic Poly(Lactide) by Using N‐Heterocyclic Carbene OrganocatalystsAngewandte Chemie-International Edition, 2007
- Zwitterionic Polymerization of Lactide to Cyclic Poly(Lactide) by Using N‐Heterocyclic Carbene OrganocatalystsAngewandte Chemie, 2007
- Alcohol Adducts of N-Heterocyclic Carbenes: Latent Catalysts for the Thermally-Controlled Living Polymerization of Cyclic EstersMacromolecules, 2006
- Latent, Thermally Activated Organic Catalysts for the On‐Demand Living Polymerization of LactideAngewandte Chemie-International Edition, 2005
- Latent, Thermally Activated Organic Catalysts for the On-Demand Living Polymerization of LactideAngewandte Chemie, 2005
- A General and Versatile Approach to Thermally Generated N‐Heterocyclic CarbenesChemistry – A European Journal, 2004
- In Situ Generation of Carbenes: A General and Versatile Platform for Organocatalytic Living PolymerizationJournal of the American Chemical Society, 2003
- Polyurethanes: A class of modern versatile materialsJournal of Chemical Education, 1992
- Das Aufbauprinzip der Urethan‐Elastomeren „Vulkollan”︁Angewandte Chemie, 1960
- Das Di‐Isocyanat‐Polyadditionsverfahren (Polyurethane)Angewandte Chemie, 1947