Carbon Monoxide in Main-Group Chemistry

The usage of carbon monoxide (CO) as a C1 feedstock for carbonylation has been an important subject of numerous studies for over a century. The chemistry in this field has evolved significantly, and several processes (e.g., Fischer–Tropsch, Monsanto, and Cativa process) have even been industrialized to serve humankind in our daily lives. CO is also a crucial ligand (carbonyl) in organometallic chemistry, and transition-metal carbonyl complexes have been widely used as homogeneous catalysts in various chemical transformations. Historically, transition-metal carbonyls have been considered to be dominant for these purposes. In recent decades, main-group elements, especially naturally abundant elements in the Earth’s crust such as silicon and aluminum, have gained much attention, as they are eco-friendly and have low toxicity compared to the late transition metals. Recent developments in main-group chemistry have revealed reactivity which can mimic that of transition-metal complexes toward small molecules such as H2, alkenes, and alkynes, along with carbon monoxide. This Perspective highlights CO activation by main-group compounds which leads to the formation of carbonyl complexes or CO insertion into the main-group element center as well as the reductive homologation of CO.