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 transitionmetal-catalyzed C-H borylation ofmethane with bis-pinacolborane (B(2)pin(2)) in cyclohexane solvent at 150 degrees C under 2800 to 3500 kilopascals of methane pressure. Iridium, rhodium, and ruthenium complexes all catalyze the reaction. Formation of mono-versus diborylatedmethane is tunable as a function of catalyst, with the ruthenium complex providing the highest ratio of CH(3)Bpin 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.