Boranes Paving the Way to Anionic Cyclic (Alkyl)(amino)carbenes (Ani-cAACs).

First examples of anionic cyclic (alkyl)(amino)carbenes (Ani-cAACs) that contain borane substituents have been synthesized. The nature of the borane substituents allows a modulation of the σ-donor or π-acceptor abilities compared to their neutral analogues. A B(CN) 3 -substituted Ani-cAAC has been generated and used in situ. The corresponding C 2 F 5 BF 2 -Ani-cAAC 6 was obtained in high yield on a multigram scale. First reactions of these novel ligands with elemental selenium and chloro(triphenylphosphine)gold(I) led to the anionic selenium adducts 7 and 8 and the Ani-cAAC gold complex 9. The properties of these compounds and data derived from theoretical calculations provide an insight into the electronic and steric properties of these novel anionic cAACs. Especially the ease of synthesis and the combination of properties such as negative charge, large buried volume, and good σ-donor and π-acceptor ability renders Ani-cAACs unique and promising new building blocks.