Synthetic Modification of Acyclic Bent Allenes (Carbodicarbenes) and Further Studies on Their Structural Implications and Reactivities

Abstract

The paper describes the synthetic development of Bertrand-type acyclic carbodicarbene scaffolds derived from an unsymmetrical bis(benzimidazol-2-yl)methane bearing two sterically demanding pendant arms, isopropyl (6a) or cyclohexyl (6b). X-ray crystallographic analysis shows that the impact of these pendant arms on the overall structural parameters of carbodicarbenes is minimal. The chemical reactivity of the carbodicarbenes was evaluated with iodomethane to afford compound 7, illustrating its nudeophilic properties. Finally, experiments were also undertaken to investigate the coordination ability of carbodicarbene toward the formation of rhodium carbonyl (10) and palladium allyl complexes (11). The crystal structures of the metal complexes have been determined, revealing that their metal-carbene distances are elongated only slightly, this fact was rationalized on the basis of geometrical steric considerations with regard to the ligand.