Synthesis and redox properties of a para-borylated phenylxanthenium cation\m{1}

Reaction of 4-(lithiophenyl)dimesitylborane with xanthone followed by reaction of the resulting alcohol with HBF $_{4}$ affords the cation 1-dimesitylboron-4-(9-xanthylium)-phenylene [1] $^{+}$ as a tetrafluoroborate salt. This salt has been fully characterized and its crystal structure determined. Cation [1] $^{+}$ can be reduced to produce a persistent radical that has been studied by EPR and whose reaction with dioxygen affords a peroxo derivative.