Generating and Trapping Metalla-N-Heterocyclic Carbenes

• Published in: Angewandte Chemie International Edition 2015-03, Vol.54 (14), p.4212-4216
• Main Authors: Ruiz, Javier, García, Lucía, Vivanco, Marilín, Berros, Ángela, Van der Maelen, Juan Francisco
• Format: Article
• Language: English
• Subjects: Affinity; carbene ligands; Carbenes; Chemical bonds; density functional calculations; Derivatives; Electronics; Fragments; manganese; N-heterocyclic carbenes; R&D; Reagents; Research & development; rhodium; Trapping
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201411647

By means of a combined experimental and theoretical approach, the electronic features and chemical behavior of metalla‐N‐heterocyclic carbenes (MNHCs, N‐heterocyclic carbenes containing a metal atom within the heterocyclic skeleton) have been established and compared with those of classical NHCs. MNHCs are strongly basic (proton affinity and pKa values around 290 kcal mol−1 and 36, respectively) with a narrow singlet–triplet gap (around 23 kcal mol−1). MNHCs can be generated from the corresponding metalla‐imidazolium salts and trapped by addition of transition‐metal complexes affording the corresponding heterodimetallic dicarbene derivatives, which can serve as carbene transfer agents. Caught in a trap: Metalla‐imidazolium salts have been prepared and are used in the generation of highly nucleophilic singlet metalla‐N‐heterocyclic carbenes (MNHCs). MNHCs were trapped by addition of transition‐metal fragments, such as CuCl. [Mn]=[Mn(bipy)(CO)2]; LiHDMS=lithium hexamethyldisilazide.