Design Concepts for N-Heterocyclic Carbene Ligands

1,3‐Bis(tricyanoborane)imidazoline‐2‐ylidenate Anion—A Ditopic Dianionic N‐Heterocyclic Carbene Ligand

“…[37] Thereaction of nickel tetracarbonyl and Li 2 3•thf resulted in the formation of the dianionic nickel tricarbonyl complex 6, which was isolated as dilithium salt Li 2 6•2thf in 83 %y ield. Thecoordination of the carbene Catom to Ni is evident from the crystal structure analysis of 2 1 [Li 2 6(thf) 2 ]( Figure 6). Similar to the solid state structure of 2 1 [Li 2 5(thf) 2 ]•thf,t wo THF molecules are coordinated to lithium per formula unit.…”

“…Thecoordination of the carbene Catom to Ni is evident from the crystal structure analysis of 2 1 [Li 2 6(thf) 2 ]( Figure 6). Similar to the solid state structure of 2 1 [Li 2 5(thf) 2 ]•thf,t wo THF molecules are coordinated to lithium per formula unit. However,i nc ase of the Ni complex 6 each Li cation is coordinated by one THF molecule and three CN moieties.…”

“…Since then, N-heterocyclic carbenes were utilized for the stabilization of reactive compounds,for the activation of strong bonds,a nd as ligands in transition metal chemistry with awealth of applications,for example,in organocatalysis,t ransition metal catalysis,a nd as pharmacophores. [2] In contrast to neutral Arduengo carbenes (I, Figure 1), which are easily accessible from imidazolium cations by deprotonation, only few examples of anionic or even dianionic NHCs are known. [3] One approach for the synthesis of anionic NHCs is the deprotonation of neutral or anionic imidazole derivatives,w hich bear borane instead of alkyl or aryl substituents at nitrogen.…”

Das 1,3‐Bis(tricyanoboran)imidazolin‐2‐ylidenat‐Anion – Ein ditopischer dianionischer N‐heterocyclischer Carben‐Ligand

“…B. in der Organo-und der Übergangsmetall-Katalyse oder als Pharmakophore,e ingesetzt. [2] Im Gegensatz zu neutralen Arduengo-Carbenen (I,A bbildung 1), die durch Deprotonierung von Imidazolium-Salzen relativ einfach zugänglich sind, sind nur wenige anionische, insbesondere wenige dianionische NHCs bekannt. [3] Die Deprotonierung ungeladener oder anionischer Imidazol-Derivate mit Boran-Substituenten anstelle von Alkyl-oder Aryl-Substituenten an den N-Atomen des Heterozyklus ist ein mçglicher Zugang zu anionischen NHCs.D as anionische Tr iscarben II wurde dieser Synthesestrategie folgend 1996 erhalten (Abbildung 1).…”

NHC Polymeric Particles Obtained by Self-Assembly and Click Approach of Calix[4]Arene Amphiphiles as Support for Catalytically Active Pd Nanoclusters

“…During the last few decades, N-heterocyclic carbene (NHC) ligands have attracted considerable attention, owing to their high stability and outstanding applications in homogeneous catalysis [1][2][3]. The advantage of this class of ligands is the ease of their generation through deprotonation of appropriate precursors (most often, imidazolium salts are used) and easily regulated steric/electron donor properties of the ligand by substituents on the heterocyclic precursor core [4][5][6][7]. Amongst N-heterocyclic carbenes, polytopic ligands featuring more than one NHC unit are of high demand, as they impact the stability of the final metal complex, owing to their chelating abilities [8,9].…”