We developed dinuclear molybdenum cluster-catalyzed radical addition and polymerization reactions by tuning the redox potential of the Mo₂ core. A 2,4,6-triisopropylbenzoate-supported Mo₂ complex acts as a catalyst for radical addition reactions of polyhaloalkanes to 1-alkenes and cyclopentene, while amidinate- and guanidinate-supported Mo₂ clusters are effective catalysts for the radical polymerization reaction of methyl methacrylate.