Synthesis and Structure of Binuclear O/S‐Bridged Organobismuth Complexes and Their Cooperative Catalytic Effect on CO 2 Fixation

In the synthesis of binuclear organobismuth complexes ( 1 – 6 ) through treatment of organobismuth chlorides with NaOH or Na 2 S⋅9H 2 O, the two 5,6,7,12‐tetrahydrodibenz [ c,f ][1,5]azabismocine frameworks are cross‐linked by either a sulfur or an oxygen atom. The complexes ( 1 – 6 ) show high catalytic efficiency in the synthesis of cyclic carbonates from 2‐(chloromethyl)oxirane and CO 2 . Compared with their precursor chlorides ( 7 – 9 ), methoxide 10 and methanethioate 11 which are mononuclear organobismuth complexes, the binuclear organobismuth complexes show higher cooperative catalytic effect. However, the complexes with an oxygen bridge ( 1 – 3 ) are not stable in air and lose their catalytic efficiency because of hydrolysis or CO 2 adsorption (forming organobismuth carbonates in the latter case). Nonetheless, the binuclear organobismuth complexes ( 4 – 6 ) with a sulfur bridge are highly stable in air and can be applied in the synthesis of cyclic carbonates (with the co‐presence of Bu 4 NI) across various kinds of epoxides, thus exhibiting satisfactory efficiency and selectivity.