inorganics Article Transmetalation from Magnesium–NHCs—Convenient Synthesis of Chelating π-Acidic NHC Complexes Julian Messelberger 1, Annette Grünwald 1, Philipp Stegner 2, Laura Senft 3, Frank W. Heinemann 1 and Dominik Munz 1,* 1 Lehrstuhl für Anorganische und Allgemeine Chemie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstr. 1, 91058 Erlangen, Germany;
[email protected] (J.M.);
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[email protected] (F.W.H.) 2 Lehrstuhl für Anorganische und Metallorganische Chemie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstr. 1, 91058 Erlangen, Germany;
[email protected] 3 Lehrstuhl für Bioanorganische Chemie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstr. 1, 91058 Erlangen, Germany;
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[email protected]; Tel.: +49-9131-85-27464 Received: 6 May 2019; Accepted: 19 May 2019; Published: 22 May 2019 Abstract: The synthesis of chelating N-heterocyclic carbene (NHC) complexes with considerable π-acceptor properties can be a challenging task. This is due to the dimerization of free carbene ligands, the moisture sensitivity of reaction intermediates or reagents, and challenges associated with the workup procedure. Herein, we report a general route using transmetalation from magnesium–NHCs. Notably, this route gives access to transition-metal complexes in quantitative conversion without the formation of byproducts. It therefore produces transition-metal complexes outperforming the conventional routes based on free or lithium-coordinated carbene, silver complexes, or in situ metalation in dimethyl sulfoxide (DMSO). We therefore propose transmetalation from magnesium–NHCs as a convenient and general route to obtain NHC complexes. Keywords: NHC; transmetalation; magnesium; palladium; carbene 1. Introduction N-heterocyclic carbene (NHC) ligands have become the powerhouse of modern transition metal chemistry [1–13].