Carbene complexes of pnictogen pentafluorides and boron trifluoride

Synthesis, characterization, and solid state X-ray crystallographic structu res for 12-Pn-6 complexes derived from carbene 4,5-dichloro-1,3-dimesitylim idazol-2-ylidene and phosphorus, arsenic, or antimony pentafluoride are rep orted. The adducts show octahedral geometries at the pnictogen centers with C-Pn bond distances of 189.8 (P), 199.9 (As), and 217.5 (Sb) pm. The struc tures are those of internal zwitterions with imidazolium ion character in t he heterocyclic ring and a pentafluoropnictanide anion bonded to C-2. Adduc ts of BF3 with 1,3-dimesitylimidazol-2-ylidene and 4,5-dichloro-1,3-dimesit ylimidazol-2-ylidene are also reported for comparison. Although the reactiv ity of chlorinated and non-chlorinated carbenes Varies considerably, the sp ectroscopic and structural properties of analogous adducts are remarkably s imilar.