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Updated: Feb 17, 2026

Isolating Free Carbenes, their Mixed Dimers and Organic Radicals
Published on: April 19, 2019
Dimerization of a mixed-carbene PdII dibromide complex by elemental iodine
Christian Jandl1, Alexander Pöthig1
1Catalysis Research Center & Department of Chemistry, Technische Universität München, Ernst-Otto-Fischer-Strasse 1, D-85747 Garching b. München, Germany.
Abstract:
A monomeric PdII complex bearing a mixed carbocyclic/N-heterocyclic carbene ligand and two bromides was reacted with an excess of elemental iodine, which resulted in the surprising removal of one bromide ligand and dimerization of the mixed-carbene complex to form di-μ-bromido-bis{[1-(cyclohepta-2,4,6-trien-2-yl-1-ylidene-κC1)-3-(2,6-diisopropylphenyl)imidazol-2-ylidene]palladium(II)} bis(pentaiodide) dichloromethane monosolvate, [Pd2Br2(C22H24N2)2](I5)2·CH2Cl2. The dimeric complex features a slightly distorted square-planar core of two PdII centres bridged by two bromide ligands, which lie in the same plane as the seven- and five-membered rings of the bidentate carbene ligand. The counter-ions in the single crystal were found to be pentaiodide monoanions featuring their typical V-shape, whereas for the bulk material, a mixture of Br/I interhalides is proposed.
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