New SiO2-attached ?Mo-pair? catalysts?Preparations, surface structures, and chemical nature

New attached molybdenum-pair catalysts with well-defined surface structures were molecularly prepared by taking advantage of the reaction between a Mo2(η3-C3H5)4 complex and surface OH groups of SiO2 followed by chemical treatments. The surface-Mo2 structures were characterized by means of ultraviolet diffuse reflection, photoluminescence, x-ray photoelectron spectroscopy, infrared, electron spin resonance, temperature-programmed hydrogenolysis, volumetry, and chemical analysis. The Mo(II)-pair chemically attached on a silica functioned as a reversible dioxygen carrier at 273–428 K. The high catalytic activities of the attached Mo2 catalysts are also described.