Pentamethylcyclopentadienyl half-sandwich hydrazine complexes of ruthenium: preparation and reactivity

Abstract

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)(NHNR1){P(OR)₃}L]BPh₄ (6–9) [R1 = Me, Ph; L = P(OR)₃, PPh₃]. Aryldiazene complexes [Ru(η⁵-C₅Me₅)(NHNAr){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.