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.