Mixed Phosphane η5-CpRuCl(PR3)2 Complexes as Ambifunctional Catalysts for Anti-Markovnikov Hydration of Terminal Alkynes

The catalytic activity of [CpRu(L)2(MeCN)]PF6 (L = 2-diphenylphosphinopyridine with bulky groups at C-6) for anti-Markovnikov hydration of terminal alkynes to aldehydes is retained when one heterocyclic ligand L is replaced by L′ = PPh3. Equal amounts of CpRuCl(PPh3)2 (1) and phosphane L in acetone solution equilibrate to a mixture of 1, CpRuCl(L)(PPh3) (2), and CpRuCl(L)2 (3), which acts as highly active in situ catalyst for preparative anti-Markovnikov hydration of alkynes in water-rich media (2 mol % [Ru], 60 °C, 3–18 h in 4:1 (v/v) acetone/water). Reactions were completed in <15 min at 160 °C.