Catalysis of surface dispersed Cu2+ species on t-ZrO2: square-planar Cu catalyzed cross-coupling of arylboronic acid and imidazole

Abstract

We examined the Chan–Lam cross-coupling of imidazole and arylboronic acids under additive-free and mild conditions using heterogeneous CuO/MO_X catalysts such as metal oxide-supported CuO and Cu-doped metal oxides. Among them, CuO/t-ZrO₂ exhibited the best performance, which was more than ten times the turnover number in comparison with that of bulk CuO. By combining experimental and computational approaches, we elucidated the surface structure of CuO/t-ZrO₂. The catalyst contained abundant highly reducible Cu²⁺ species, in contrast to other Cu²⁺-containing catalysts. Notably, X-ray absorption spectroscopy and density functional theory calculations revealed that the Cu²⁺ species are square-planar [CuO₄]. Our results indicate that the highly active [CuO₄] species play a key role in the present coupling reaction.