Preparation of new diazene complexes of ruthenium and osmium

The hydrazine complexes [Ru(NH2NH2)L-5](BPh4)(2) 1, 8 or [Ru(NH2NH2)L'L-4](BPh4)(2) 2 [L = P(OEt)(3), L' = PPh(OEt)(2)] were prepared by allowing the corresponding hydride species [RuHL5]BPh4 or [RuHL'L-4]BPh4 to react first with HBF4 and then with hydrazine. Oxidation of these hydrazine complexes or [Os(NH2NH2)L-5](BPh4)(2) with Pb(OAc)(4) at -30 degreesC led to the corresponding stable and isolable 1,2-diazene complexes [M(NH=NH) L-5](BPh4)(2) 3, 5 (M = Ru, Os) or [Ru(NH=NH) L'L-4](BPh4)(2) 4. The phenyldiazene derivatives [M(PhN=NH) L-5](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 NH=NH ligand in [Ru(NH=NH)L-5](BPh4)(2) and was characterised by X-ray crystal structure determination. Oxidation reactions of the bis( hydrazine) complexes [Ru(NH2NH2)(2)L-4](BPh4)(2) or [Ru(CH3NHNH2)(2)L-4](BPh4)(2) [L = P(OEt)(3)] with Pb(OAc)(4) were reinvestigated and were found to give the diazene complexes [Ru(NH=NH)(2)L-4](BPh4)(2) 9, [Ru(CH3N-NH)(2)L-4](BPh4)(2) 11 or [Ru(CH3N= NH)(CH3NHNH2)L-4](BPh4)(2) 10.