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

Phosphino-functionalized mesoionic olefins (p-MIOs), (iMIC)CHR (iMIC = PhC{N(Dipp)} 2 C(PPh 2 )C, Dipp = 2,6-iPr 2 C 6 H 3 ; 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 -1 ) and 4b (288.1 kcal mol -1 ) support their remarkable basicity that exceeds that of classical NHCs. Treatment of 4a with (Me 2 S)AuCl (and AgOTf) affords the dinuclear gold compounds [(4a)Au](X) 2 (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 2 yields the boronium cation [(4a)BPhCl]Cl (6).