The hydroxido-bridged dinuclear ruthenium complex 4, which is supported by Tp ligands, has been prepared from protonation of the oxido-bridged dinuclear ruthenium complex 3. Additional protonation of 4, affording the aqua-bridged dinuclear ruthenium complex 5in situ, and subsequent treatment with NO gave rise to the dicationic dinitrosyl complex 2. These indicate completion of the NO reduction cycle on the dinuclear ruthenium complex.