Catalyst-controlled selectivity in the C–H borylation of methane and ethane

The C–H bonds of methane are generally more kinetically inert than those of other hydrocarbons, reaction solvents, and methane functionalization products. Thus, developing strategies to achieve selective functionalization of CH₄ remains a major challenge. Here, we report transition metal–catalyzed C–H borylation of methane with bis-pinacolborane (B₂pin₂) in cyclohexane solvent at 150°C under 2800 to 3500 kilopascals of methane pressure. Iridium, rhodium, and ruthenium complexes all catalyze the reaction. Formation of mono- versus diborylated methane is tunable as a function of catalyst, with the ruthenium complex providing the highest ratio of CH₃Bpin to CH₂(Bpin)₂. Despite the high relative concentration of cyclohexane, minimal quantities of borylated cyclohexane products are observed. Furthermore, all three metal complexes catalyze borylation of methane with >3.5:1 selectivity over ethane.