μ-3,3'-Diisopropyl-1,1'-(propane-1,3-di-yl)bis-(1,3-diazinan-2-yl-idene)]bis-[bromido-(η(4)-cyclo-octa-1,5-diene)rhodium(I).

The title compound, [Rh2Br2(C8H12)2(C17H32N4)], was obtained by the reaction of 3,3'-(propane-1,3-di-yl)bis-(1-isopropyl-3,4,5,6-tetra-hydro-pyrimidin-1-ium) bromide and [{Rh(cod)Cl}2] (cod is cyclo-octa-1,5-diene) in tetra-hydro-furan. The two Rh(I) atoms each have a distorted square-planar coordination environment, defined by a bidentate cod ligand, a bromide anion and one C atom of the bridging bidentate bis-N-heterocyclcic carbene (NHC) ligand. The average Rh-CNHC distance is 2.

CO2 and Sn(II) adducts of N-heterocyclic carbenes as delayed-action catalysts for polyurethane synthesis.

Catalytic rivals: Both CO(2)-protected tetrahydropyrimidin-2-ylidene-based N-heterocyclic carbenes (NHCs) and Sn(II)-1,3-dimesitylimidazol-2-ylidene, as well as Sn(II)-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 CO(2)-protected pyrimidin-2-ylidenes as well as 1,3-dimesitylimidazol-2-ylidene and dimesitylimidazolin-2-ylidene complexes of Sn(II) have been prepared. Selected single-crystal X-ray structures are reported.