Planar Subporphyrin Borenium Cations

Subporphyrin borenium cations with a carborane counterion have been prepared by treatment of B-methoxy subporphyrins with the silylium reagent Et<sub>3</sub>Si(CH<sub>6</sub>B<sub>11</sub>Br<sub>6</sub>). In contrast to the distinctly domed subphthalocyanine borenium cation, a nearly planar structure with <i>sp</i><sup><i>2</i></sup> hybridized boron is found in the X-ray structure of the triphenylsubporphyrin borenium cation. The cations exhibit absorption and fluorescence spectra that are quite similar to those of B-methoxy subporphyrins. B-phenyl subporphyrins were prepared in good yield by reaction of subporphyrin borenium cations with phenyllithium.