Preparation of new diazene complexes of ruthenium and osmium

Abstract

The hydrazine complexes [Ru(NH₂NH₂)L₅](BPh₄)₂ 1, 8 or [Ru(NH₂NH₂)L′L₄](BPh₄)₂ 2 [L = P(OEt)₃, L′ = PPh(OEt)₂] were prepared by allowing the corresponding hydride species [RuHL₅]BPh₄ or [RuHL′L₄]BPh₄ to react first with HBF₄ and then with hydrazine. Oxidation of these hydrazine complexes or [Os(NH₂NH₂)L₅](BPh₄)₂ with Pb(OAc)₄ at −30 °C led to the corresponding stable and isolable 1,2-diazene complexes [M(NHNH)L₅](BPh₄)₂ 3, 5 (M = Ru, Os) or [Ru(NHNH)L′L₄](BPh₄)₂ 4. The phenyldiazene derivatives [M(PhNNH)L₅](BPh₄)₂ 6, 7 (M = Ru, Os) were also prepared by treating the hydride [MHL₅]BPh₄ species with phenyldiazonium tetrafluoroborate. The aquo-complex, [Ru(H₂O){P(OEt)₃}₅](BPh₄)₂ 8, was obtained by substitution of the NHNH ligand in [Ru(NHNH)L₅](BPh₄)₂ and was characterised by X-ray crystal structure determination. Oxidation reactions of the bis(hydrazine) complexes [Ru(NH₂NH₂)₂L₄](BPh₄)₂ or [Ru(CH₃NHNH₂)₂L₄](BPh₄)₂ [L = P(OEt)₃] with Pb(OAc)₄ were reinvestigated and were found to give the diazene complexes [Ru(NHNH)₂L₄](BPh₄)₂ 9, [Ru(CH₃NNH)₂L₄](BPh₄)₂ 11 or [Ru(CH₃NNH)(CH₃NHNH₂)L₄](BPh₄)₂ 10.