Synthesis of N-bonded enolatoruthenium(II) by oxidative addition of alkyl cyanocarboxylate to a ruthenium(0) complex

Abstract

Reaction of a zero-valent ruthenium complex [Ru(cot)(cod)] 1 (cod = 1,5-cyclooctadiene; cot = 1,3,5-cyclooctatriene) with alkyl cyanoacetate in the presence of mono- and bi-dentate tertiary phosphines gave a series of hydrido(enolato)ruthenium(II) complexes: mer-[RuH(NCCHCO₂Et)(NCCH₂CO₂Et)(PPh₃)₃] 2; trans-[RuH(NCCHCO₂Et)(cod)(dppe)] 3 (dppe = Ph₂PCH₂CH₂PPh₂); trans-[RuH(NCCR¹CO₂R²)(dppe)₂] (R¹ = H, R² = Et 4a: or Prⁱ 4b; R¹ = Me, R² = Et 4c) and trans-[RuH(NCCMeCO₂Et)(PMePh₂)₄] 5. The molecular structure of 3 shows that the enolato ligand co-ordinates to the ruthenium centre via the cyano group in an octahedral geometry. These hydrido(enolato)ruthenium(II) complexes catalyse Michael and Knöevenagel reactions under neutral and mild conditions.