Pentamethylcyclopentadienyl Half-Sandwich Hydrazine Complexes of Ruthenium: Preparation and Reactivity

Hydrazine complexes [Ru(η5-C5Me5)(NH2NHR1){P(OR)3}L]BPh4 (1–4) [R1 = H, Me, Ph; L = P(OR)3, PPh3; R = Me, Et] were prepared by the reaction of chloro compounds [RuCl(η5-C5Me5){P(OR)3}L] with hydrazines in the presence of NaBPh4. When exposed to air in CH2Cl2 solution, the phenylhydrazine derivatives 1c–4c afforded the sandwich complex [Ru(η5-C5Me5)(η6-C6H6)]BPh4 (5). A reaction path involving the formation of a phenyldiazene complex as an intermediate compound is discussed. The oxidation of hydrazine complexes 1–4 with Pb(OAc)4 at −40 °C yielded diazene derivatives [Ru(η5-C5Me5)(NH[double bond, length as m-dash]NR1){P(OR)3}L]BPh4 (6–9) [R1 = Me, Ph; L = P(OR)3, PPh3]. Aryldiazene complexes [Ru(η5-C5Me5)(NH[double bond, length as m-dash]NAr){P(OR)3}L]BPh4 (7, 9) (Ar = Ph, p-tolyl) were also prepared by allowing hydride [RuH(η5-C5Me5){P(OR)3}L] (10, 11) to react with aryldiazonium salts ArN2+BF4− in CH2Cl2. The complexes were characterised by spectroscopy (IR, 1H, 31P, and 15N NMR) and the X-ray crystal structure of [Ru(η5-C5Me5)(NH2NH2){P(OEt)3}2]BPh4 (2a) and [Ru(η5-C5Me5)(η6-C6H6)]BPh4 (5) was determined