Metal Complexes of Biologically Important Ligands, Part CLXXVIII. Addition of the Pentacarbonylrhenium Cation [(OC)5Re]+ to the Xanthine Alkaloids Caffeine, Theophylline, and Theobromine

By reaction of pentacarbonyltetrafluoroboratorhenium with the neutral methylated xanthine derivatives the cationic complexes [(OC)5Re‐L]+BF4– (L = caffeine, isocaffeine, theophylline, theobromine) were prepared and spectroscopically characterized.