Visible Light-Driven Catalytic Reaction Catalyzed By the B12-Rhodium-Titanium Oxide Hybrid Catalyst

Abstract

Organometallic B12 compounds are unique metal complexes having a cobalt-carbon σ-bond present in biological systems [1]. Cleavage of the metal-organic σ-bond initiates many B12 dependent enzymatic reactions. Based on unique properties of B12 enzymes, many B12-inspired reactions were developed [2]. Here we report the visible light-driven new B12 inspired reaction for the fine chemical synthesis [3]. The hybrid catalyst composed of the B12 complex and rhodium ion modified titanium oxide was synthesized for the visible light-driven B12 inspired reaction. Visible light irradiation (λ≧420 nm) of the hybrid catalyst in the presence of a sacrificial reagent showed absorption at 390 nm, typical for the Co(I) state of the B12 complex monitored by diffuse reflectance UV-vis analysis, which imply that electron transfer from the titanium oxide to Co(III) center of the B12 complex occurred by the visible light irradiation. Benzotrichloride was converted to N,N-diethylbenzamide by the visible light irradiation in the presence of triethylamine catalyzed by the hybrid catalyst in air at room temperature. Both the conduction band electron and valence band hole of the catalyst were utilized for the reaction to form the amide product. The reaction mechanism of the duet reaction was proposed. The B12-inspired photocatalyst shown here can be used for the sustainable production of fine chemicals with the possible expense of energy economy.[1] Review: H. Shimakoshi, Y. Hisaeda, Current Opinion in Electrochem. 2018, 8, 24.[2] K. Proinsias, A. Jackowska, K. Radzewicz, M. Giedyk, D. Gryko, Org. Lett., 2018, 20, 296.[3] K. Shichijo, M. Fujitsuka, Y. Hisaeda, H. Shimakoshi, J. Organomet. Chem. 2020, in press. Figure 1