Application of Solid-State Molybdenum Sulfide Clusters with an Octahedral Metal Framework to Catalysis: Ring-Opening of Tetrahydrofuran to Butyraldehyde

Abstract

Solid-state molybdenum sulfide clusters with an octahedral metal framework, the superconducting Chevrel phases, are applied to catalysis. The cluster of copper salt, Cu x Mo6S8 (x = 2.94), stored in air is treated in a hydrogen stream above 300 °C. The activated cluster exhibits catalytic activity for the ring-opening of tetrahydrofuran, yielding butyraldehyde. Cyclic ethers such as trimethylene oxide and tetrahydropyran are also converted to the corresponding aldehydes. The cluster contains nonstoichiometric defects of sulfur atoms. Oxygen atoms are incorporated at the sulfur-deficient sites upon storage in air, but they are removed from the sites by the activation in a hydrogen stream. The resulting coordinatively unsaturated molybdenum atoms are catalytically active for the ring-opening reaction. The molybdenum atom in an intermediate oxidation state around 2+ is moderately coordinated by the oxygen of tetrahydrofuran and favorably releases the produced aldehyde. The neutral cluster Mo6S8, which has such sulfur-deficient sites, also catalyzes the reaction.