SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF BINUCLEAR (ETA-6-BENZENE)RUTHENIUM(II) COMPLEXES WITH ONE OR 2 BRIDGING N-DONOR LIGANDS

Reaction of [(eta-6-C6H6)RuCl2]2 with pyrazole (Hpz) in appropriate molar ratio at room temperature in H2O/CH3OH yields the products [(eta-6-C6H6)Ru(mu-Cl)(mu-pz)2Ru(eta-6-C6H6)]Cl (1a) and [(eta-6-C6H6)Ru(mu-Cl)2(mu-pz)Ru(eta-6-C6H6)]Cl (2a), the structures of which were established by an X-ray study. Analogous binuclear complexes 3a and 4a were prepared with 4-methylpyrazole (4MepzH). The facile Cl-/OH- exchange in these complexes has been studied by H-1 NMR spectroscopy at elevated temperatures. The hydroxo-bridged complexes [(eta-6-C6H6)Ru(mu-OH)(mu-pz)2Ru(eta-6-C6H6)]Cl (1b) and [(eta-6-C6H6)Ru(mu-OH)2(mu-pz)Ru(eta-6-C6H6)]Cl (2c) were also be prepared directly from [(eta-6-C6H6)RuCl2]2 and pyrazole by refluxing in H2O/CH3OH solution. Reaction of [(eta-6-C6H6)RuCl2]2 with 6-azauracil (6auraH2) in H2O/CH3OH solution at room temperature yields [(eta-6-C6H6)Ru(mu-OH)2(mu-6auraH)Ru(eta-6-C6H6)]Cl (6), the crystal structure of which is reported. A chloro-bridged binuclear complex could not be prepared; the analogous reaction in methanol alone gives [(eta-6-C6H6)Ru-Cl2(6auraH2)] (7).