Interaction of hydrazines N2H4X+ (X = H/Ph) with [Ru(HL)(OH2)] (1) (L = 1,2-diaminopropanetetraacetate, PDTA) has been investigated by potentiometry, spectrophotometry and electrochemistry in aqueous solution at 25 degrees C. The deprotonation and hydrolysis constants of 1 and its hydrazinium adducts formed in 0.1 M Na2SO4 solution were determined by potentiometry, while the second order rate constant k(1) and k(2) for the formation of [Ru(HL)(N2H4X)](+) and [Rn(L)(N2H4X)] were determined kinetically by spectrophotometry. Ar pH 2.8, the complex 1 exhibited a quasi-reversible one-electron reduction step at (E-1/2) -0.251 V vs. SCE and the hydrazinium adducts obtained in situ in the presence of excess (100 equiv) N2H4X+ showed an additional multi-electron (two-electron per metal at a time) reduction step at (E-1/2) -0.046/-0.158 V (vs. SCE) in the case of X = H/Ph, respectively in sampled-de. The hydrazines, N2H4X+ were reduced electrolytically by holding the potential at - 0.150 and - 0.250 V (Hg-pool) vs. SCE, respectively, and chemically by using H-2 at atmospheric pressure, ascorbic acid, catechol, Zn-dust and NaBH4 in the presence of these hydrazinium adducts. The turnover numbers, moles of ammonia formed per mole of metal per hour, have been calculated, discussed and compared with those of EDTA (ethylenediaminetetraacetate) analogue. The plausible reaction mechanism for the chemical and the electrochemical reduction of N2H4X+ to ammonia and/or aniline and the implication of these results on the possible function of nitrogenases have also been proposed. The complex [Ru(HL)(N2H5)]HSO4 and [Ru(HL)(N2H4Ph)]Cl were synthesized and characterized.