From a stable silanone complex to isolable, donor-supported silicoxonium halides [LSi(dmap)=O-SiMe3](+)X-.

The first donor-stabilized silylated silicoxonium species LSi=O-SiMe(3) (L=(RN)C(=CH(2))CH=CMe(NR), R=2,6-iPr(2)C(6)H(3)) have been synthesized from the reaction of the dmap-supported (dmap=p-dimethylaminopyridine) silanone complex [LSi(dmap)=O] (1) with trimethylsilyl halides. Although the reaction with Me(3)SiCl leads directly to the Si=O addition product [LSi(Cl)OSiMe(3)] (2), the ionic silicoxonium bromide L(dmap)Si=O-SiMe(3)Br(-) (3) can be obtained as a primary product of the reaction with Me(3)SiBr, which affords [LSi(Br)OSiMe(3)] (4) with release of the dmap ligand at room temperature in THF. In the case of Me(3)SiI, the reaction furnishes the silicoxonium iodide L(dmap)Si=O-SiMe(3)I(-) (5) as the most stable species. Compounds 2-5 were isolated and fully characterized through multinuclear NMR spectroscopy, mass spectrometry, elemental analyses, and single-crystal X-ray diffraction analyses.