Diaryl Bismuthides and Acyl Bismuthanes Enable Visible-Light-Induced Reversible Carbon Monoxide Insertion and Extrusion

Carbon monoxide (CO) is one of the simplest and most fundamental molecules that has fascinated chemists for decades. Early-on, chemists have recognized and exploited its favorable properties as a key reagent in large-scale metallurgical processes, productions of base- and fine chemicals, and (more recently) potential medical applications. Most of these transformations rely on reactions that proceed in the coordination sphere of transition metals, with reversible reactions playing a crucial role in catalytic transformations. Recent endeavors have brought main group elements on the stage of carbonyl chemistry (carbonyl = metal-bound CO), but reversible reactions (especially insertion and extrusion reactions) are very rare and remain limited to examples of thermal initiation. Here we show that an innovative access to acyl-bismuth compounds, R₂Bi-C(O)R', can be granted in a stepwise redox approach. The target compounds could be isolated and fully characterized. As a unique feature, these complexes enable the visible-light-driven reversible CO extrusion and insertion of carbon monoxide in the coordination sphere of a main group metal.