Chloro and Azido Diruthenium complexes Bearing Electron-Rich N,N′,N-Triphenylguanidinate Ligands

The reaction of Ru-2(OAc)(4)Cl with N,N'N ''-triphenylguanidine (HTPG) produces one of two different compounds depending on the reaction conditions. In acetone in the presence of triethyl amine, the reaction produces tri-substituted Ru-2(TPG)(3)(OAc)Cl, and in refluxing xylene, the tetra-substituted Ru-2(TPG)(4)Cl is produced. Both of these new complexes can be cleanly converted into their corresponding azido analogues by reaction with sodium azide in methanol. The X-ray crystal structures of Ru-2(TPG)(3)(OAc)Cl, Ru-2(TPG)(3)(OAc)N-3, and Ru-2(TPG)(4)Cl are presented, along with magnetic, electrochemical, and spectral measurements for each compound. Studies in solution show that, in contrast to Ru-2(TPG)(3)(OAc)Cl, Ru-2(TPG)(4)Cl is sterically hindered at the axial positions, and readily dissociates a chloride ion at high ionic strength. Equilibrium constants for chloride association and dissociation have been estimated. Mass spectrometric data suggest that the two azido complexes are precursors to new diruthenium nitrido species.