Tin–Ruthenium Cooperative Catalyst for Disproportionation of Formic Acid to Methanol

The disproportionation of formic acid to methanol and CO2 offers a renewable route to methanol avoiding the use of high-pressure H2. Previous studies have identified competent transition-metal catalysts that nonetheless experienced unsatisfactory methanol selectivity because of competing formic acid dehydrogenation, motivating further catalyst improvement. Herein we report a bimetallic cooperative catalyst based on tin­(II) oxide and a ruthenium complex for the disproportionation of formic acid to methanol. The diruthenium complex [(Cp*Ru)2(μ-NPh)­(μ-CH2)] (Cp* = η5-C5Me5) combined with tin­(II) oxide gave methanol (and methyl formate) in up to 28% selectivity and 191 turnovers under optimized conditions. The isolation of a Ru2Sn heterotrimetallic complex [{Cp*Ru­(CO)2}2Sn­(O2CH)2] from a catalytic reaction mixture indicated the generation of an active Ru–Sn bonded species in situ. Reaction pathways involving a tin­(II) formate unit supported by Ru–Sn bonds are discussed with the aid of computational results.