N ‐Boron‐Functionalized Anionic N ‐Heterocyclic Carbenes (NBA‐NHCs)—A Case Study

The synthesis and characterization of a new family of N ‐ b oron‐functionalized a nionic NHCs (NBA‐NHCs), I i PrB(CN) 3 − ( 5 ), I i Pr(C 2 F 5 )BF 2 − ( 6 ), IMesB(CN) 3 − ( 7 ), and IMes(C 2 F 5 )BF 2 − ( 8 ), accessible on gram‐scale from air‐ and moisture‐stable precursors, is reported. Multinuclear NMR, IR spectroscopy, and single‐crystal X‐ray diffraction confirm highly electron‐rich carbenic carbon centers and strengthened B–N interactions in these molecules. Selenium adducts 9 – 12 of these NBA‐NHCs indicate an enhanced π ‐acceptor character relative to neutral NHCs, while Tolman electronic parameters of nickel tricarbonyl complexes [(NBA‐NHC)Ni(CO) 3 ] − K + 13 – 16 demonstrate their strong donor ability, similar to dianionic carbenes. Steric maps and buried volume (% V bur ) analyses of linear gold(I) complexes [(NBA‐NHC)Au(PPh 3 )] 17 – 20 reveal tunable steric profiles, ranging from anisotropic to strongly shielding environments by varying the N ‐substituents. These results establish NBA‐NHCs as a modular ligand platform enabling control of electronic properties and steric demand at the metal center for future applications in coordination chemistry and catalysis.