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

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 nucleophilic 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.