Preparation of mono- and bis-(hydrazine) complexes of ruthenium(II) †

Hydrazine complexes [RuH(R1NHNH2)L4]BPh4 1–3, [Ru(R1NHNH2)2L4][BPh4]2 4–6 [R1 = H, Me, Ph, 4-MeC6H4 or 4-O2NC6H4; L = P(OEt)3, PPh(OEt)2 or P(OMe)3] were prepared by allowing the hydride species [RuH2L4] to react, first with triflic acid (CF3SO3H) and then with an excess of the appropriate hydrazine. The derivatives [RuH(Me2NNH2){P(OEt)3}4]BPh4 1f, [Ru(η1-OSO2CF3)(Me2NNH2){P(OEt)3}4]BPh4 9 and [Ru(η2-Ph-CONHNH2)L4][BPh4]2 7,8 [L = P(OEt)3 or PPh(OEt)2] were also obtained. The formulation and geometry in solution of the compounds were established by infrared and 1H and 31P NMR spectroscopy. The reaction of the bis(nitrile) complexes [Ru(R2CN)2L4][BPh4]2 [R2 = Me or MeC6H4; L = P(OEt)3 or PPh(OEt)2] with hydrazines depends not only on the experimental conditions, but also on the nature of the phosphite and the hydrazine used. Thus, nitrilehydrazine [Ru(R1NHNH2)(R2CN)L4][BPh4]2 10–13 [L = P(OEt)3 or PPh(OEt)2] or amidrazone derivatives [Ru{η2-NHC(R2)N(R1)NH2}{P(OEt)3}4][BPh4]2 14,15 (R1 = H or Me) were obtained together with the bis(hydrazine) compounds [Ru(R1NHNH2)2L4][BPh4]2. Reaction of the arylhydrazine complexes 1–6 and 10–13 with Pb(O2CMe)4 at –30 °C in CH2Cl2 resulted in selective oxidation of the arylhydrazine ligand giving the aryldiazene derivatives [RuH(R1NNH)L4]BPh4, [Ru(R1NNH)2L4][BPh4]2 and [Ru(R1NNH)(R2CN)L4][BPh4]2 (R1 = Ph, 4-MeC6H4 or 4-O2NC6H4). Treatment of hydrazine NH2NH2 and methylhydrazine MeNHNH2 complexes 1–6 with Pb(O2CMe)4, instead, afforded the acetate [Ru(η2-O2CMe)L4]BPh4 derivatives which were characterised by a crystal structure determination of [Ru(η2-O2CMe){P(OEt)3}4]BPh4. The co-ordination of ruthenium is distorted octahedral with approximate C2v symmetry and the acetate is bidentate.