Ruthenium‐Catalyzed Methanol Production from Aqueous Paraformaldehyde and Mechanistic Study

Abstract A series of water‐soluble arene‐Ru(II) complexes, [( η 6 ‐ p ‐cymene)RuCl( L )] + Cl ‒ ( [Ru]‐7 – [Ru]‐12 ) (L = substituted bis‐imidazole methane) exhibited efficient and selective methanol production from paraformaldehyde in water. The findings inferred a crucial role of the ligand in tuning the catalytic performance. A pH‐dependent behavior of this series of catalysts was observed, where the amount of base was influential in methanol production from paraformaldehyde. The catalyst [Ru]‐7 ( L1 = 4,4′‐((2‐hydroxyphenyl)methylene)bis(2‐ethyl‐5‐methyl‐1 H ‐imidazole) was the most efficient among the explored catalysts giving a turnover number (TON) of 1200 at 90 °C. A mechanistic cycle has also been proposed for the catalytic reaction based on the mass and NMR investigations including those using deuterium‐labelled molecules.