THE CHEMISTRY OF (TETRAMETHYLTHIOPHENE)RU2+, (PARA-CYMENE)RU2+

Described are the compounds [(ring)Ru(OTf)2]x, where ring = 2,3,4, 5-tetramethylthiophene (TMT, 1), and p-cymene (2). These electrophilic reagents serve as precursors to [(ring)RuL3]2+, where L3 = (H2O)3, (NH3)3, and (PH3)3. Solutions of 1 and 2 react with carbon monoxide to give (ring)Ru(CO)(OTf)2. The addition of thiophenes to CH2Cl2 solutions of 1 or 2 leads to the precipitation of the sandwich compounds [(ring)(SC4R4)Ru](OTf)2, where SC4R4 = thiophene, 2,5-dimethylthiophene, and TMT. [(TMT)Ru(H2O)3](OTf)2 was characterized by single-crystal X-ray crystallography, which established a piano-stool geometry with a planar TMT ligand. [(TMT)Ru(D2O)3](OTf)2 decomposes in D2O solution at 150-degrees-C to give [(TMT)2Ru]2+, which undergoes selective deuteration at the 2,5-methyl groups. D2O solutions of [(TMT)2Ru]2+ undergo photochemical loss of one TMT ligand in water to give [(TMT)Ru(D2O)3]2+. Photolysis of an aqueous solution of [(TMT)(p-cymene)Ru]2+ gives primarily [(TMT)Ru(H2O)3]2+. A procedure is described for the reversible loading of 1 onto gamma-alumina, which in turn was characterized by C-13 CP-MAS NMR spectroscopy.