| Abstract: | The cyclization reaction of coordinated β‐functional phenyl isocyanides was used to generate coordinated anellated N‐heterocyclic carbenes. Coordinated 2‐trimethylsiloxyphenyl isocyanide reacts, after Si? O bond cleavage, to yield a complex with a coordinated benzoxazol‐2‐ylidene ligand. The cyclization reaction of coordinated 2‐aminophenyl isocyanide, obtained in situ from 2‐azidophenyl isocyanide, yields the coordinated benzimidazol‐2‐ylidene. Both ylidenes can be alkylated at the nitrogen atoms. Attempts to generate four benzimidazol‐2‐ylidenes at PtII and to bridge them by N‐alkylation leading to a crown ether‐like ligand with carbene donors are presented here. Free N‐heterocyclic carbenes derived from benzimidazole with large N‐substituents exist as monomers while they dimerize to dibenzotetraazafulvalenes when substituted with sterically less‐demanding substituents at the ring nitrogen atoms. A chemical equilibrium between the monomeric carbene and its dimerized enetetraamine exists for the N,N′‐isopropyl substituted derivative. © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:540–549, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10099 |
