Crystalline phosphino-functionalized mesoionic olefins (p-MIOs).

Phosphino-functionalized mesoionic olefins (p-MIOs), (iMIC)CHR (iMIC = PhC{N(Dipp)}C(PPh)C, Dipp = 2,6-iPrCH; R = H 4a or Ph 4b), derived from a 1,3-imidazole-based mesoionic carbene (iMIC) are reported. The p-MIOs 4a (blue) and 4b (green) are crystalline solids and have been characterized by NMR spectroscopy and X-ray diffraction as well as DFT calculations. The calculated proton affinities of 4a (291.3 kcal mol) and 4b (288.1 kcal mol) support their remarkable basicity that exceeds that of classical NHCs. Treatment of 4a with (MeS)AuCl (and AgOTf) affords the dinuclear gold compounds [(4a)Au](X) (5-X) (X = Cl or OTf) with a short Au⋯Au distance of 3.130(2) Å for 5-Cl. The reaction of 4a with the main-group reagent PhBCl yields the boronium cation [(4a)BPhCl]Cl (6).