Backbone Phosphonamide-Functionalized Imidazol-2-ylidene Complexes

The synthesis of M(CO)5 complexes bearing 4-phosphonamide and 4,5-bis(phosphonamide)-imidazol-2-ylidene ligands (NHCP = phosphonamide-based N-heterocyclic carbene) is reported. Deprotonation of respective imidazolium hydrogensulfate salts with potassium tert-butoxide (KOtBu) in the presence of [M(CO)5(CH3CN)] afforded complexes with the formula [M(CO)5(NHCP)]. In a similar fashion, reaction of in situ generated NHCP with [Rh(cod)Cl]2 (cod = 1,5-cyclooctadiene) afforded a complex with the formula [Rh(cod)Cl(NHCP)]. Low-temperature deprotonation of the imidazolium NHCP·H2SO4 with potassium hexamethyldisilazide (KHMDS) in the presence of [AuCl(SMe2)] furnished the corresponding AuI NHC complex. All complexes were characterized by various spectroscopic and spectrometric methods. In addition, further structural confirmation is provided by key single-crystal X-ray structure determinations for three of the new complexes.