Aminolysis of Dicationic Ruthenium Thiophene Complexes

Dicationic sandwich complexes containing thiophene, 2-methylthiophene7 2,5-dimethylthiophene, and tetramethylthiophene react with ammonia to give salts of the formula [(ring)Ru(SC4R4NH2)lX where ring = CsMe6 or cymene. The thiophene, 2-methylthiophene, and 2,5-dimethylthiophene complexes undergo C-S cleavage to give iminium-thiolato derivatives. In the case of the 2,5-dimethylthiophene complex, a kinetic isomer was isolated which slowly isomerized to a thermodynamic isomer. The ammonia adducts of the tetramethylthiophene complexes [(cymene)Ru(C4Me4S)I2+ and [(CsMe5)Rh(C4Me4S)12+ do not undergo C-S cleavage. These 2-NH2C4Me4S complexes react with protic acids to regenerate the starting dication [(ring)M(C4Me4S)12+. The aniline adducts of thiophene, 2-methylthiophene, and 2,5-dimethylthiophene are similar t o the ammonia derivatives. The structures of the kinetic isomer of [(C~M~~)RU(SC~H~M~CHNHP~)IPF~ and the thermodynamic isomer of [(cymene)Ru(SC3HzMeCMeNHPh)lOTf were established by single-crystal X-ray diffraction. The crystallographic study proves that the isomerization in this family of compounds arises from the relative configuration a t the terminal carbon of the alkenyl thiolate ligand. Bond distance data indicate an interaction between the iminium carbon center and the Ru atom in the kinetic isomer.