Ultrasound-assisted synthesis of water-soluble monosubstituted diruthenium compounds

The elusive monosubstituted diruthenium complexes Ru₂Cl(DAniF)(O₂CMe)₃] (1), Ru₂Cl(DPhF)(O₂CMe)₃] (2), Ru₂Cl(D-p-CNPhF)(O₂CMe)₃] (3), Ru₂Cl(D-o-TolF)(O₂CMe)₃] (4), Ru₂Cl(D-m-TolF)(O₂CMe)₃] (5), Ru₂Cl(D-p-TolF)(O₂CMe)₃] (6) and Ru₂Cl(p-TolA)(O₂CMe)₃] (7) have been synthesized using for the first time ultrasound-assisted synthesis to carry out a substitution reaction in metal–metal bonded dinuclear compounds (DAniF^? = N,N′-bis(4-anisyl)formamidinate; DPhF^? = N,N′-diphenylformamidinate; D-p-CNPhF^? = N,N′-bis(4-cyanophenyl)formamidinate; D-o/m/p-TolF^? = N,N′-bis(2/3/4-tolyl)formamidinate; p-TolA^? = N-4-tolylamidate). This is a simpler and greener method than the tedious procedures described in the literature, and it has permitted to obtain water-soluble complexes with good yields in a short period of time. A synthetic study has been implemented to find the best experimental conditions to prepare compounds 1–7. Two different types of ligands, formamidinate and amidate, have been used to check the generality of the method for the preparation of monosubstituted complexes. Five new compounds (2–6) have been obtained using a formamidinate ligand, the synthesis of the previously described compound 1 has been improved, and an unprecedented monoamidate complex has been achieved (7). The crystal structures of compounds 3 and 7 have been solved by single crystal X-ray diffraction. These compounds show the typical paddlewheel structure with three acetate ligands and one formamidinate (3) or amidate (7) bridging ligand at the equatorial positions. The axial positions are occupied by the chloride ligand giving rise to one-dimensional polymer structures that were previously unknown for monosubstituted compounds.