Tropylium tetrafluoroborate is an organic compound with the formula C7H7BF4. Containing the tropylium cation and the non-coordinating tetrafluoroborate counteranion, tropylium tetrafluoroborate is a rare example of a readily isolable carbocation. It is a white solid. This compound may be prepared by the reaction of cycloheptatriene with phosphorus pentachloride, followed by tetrafluoroboric acid. See also Triphenylmethyl chloride, also known as trityl chloride. References Tetrafluoroborates Carbocations Non-benzenoid aromatic carbocycles