1-Fluoro-4-methyl-1,4-diazoniabicyclo[2,2,2]octane bis(tetrafluoroborate) could be used to making a diaryliodonium compound (Ar1-I(X)2). Ar1-I(X)2 is widely used for preparing fluorinated and radiofluorinated aromatic compounds, aryl fluorides, preferably 18F labeled radiotracers; in pharmaceuticals and positron emission tomography (PET) tracers; for nucleophilic fluorination of electron-rich and electron-deficient arenes; for diagnosis of disease; and for noninvasive demonstration of physiologic or pathologic processes in vivo.