Crystalline phosphino-functionalized mesoionic olefins (p-MIOs)

Abstract

Phosphino-functionalized mesoionic olefins (p-MIOs), (iMIC)CHR (iMIC = PhC{N(Dipp)}₂C(PPh₂)C, Dipp = 2,6-iPr₂C₆H₃; 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 (Me₂S)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 PhBCl₂ yields the boronium cation [(4a)BPhCl]Cl (6).