Reversible CO Insertion into the Si = Si Double Bond Enables a Disila-Bislactone Formation via Subsequent CO₂ Addition

Carbon monoxide inserts into the Si═Si double bond of an imino(silyl)disilene and tetra(silyl)disilene affording the corresponding 1,3-disilaallene oxides, characterized by NMR spectroscopy and X-ray crystallography and supported by quantum chemical calculations. In the case of imino(silyl)disilene, the CO insertion is less exergonic than for tetrasilyldisilene and, thus, is fully reversible in the presence of a CO trapping agent. The reaction mechanisms and reversibility facilitated by the imino-substituent were supported by quantum chemical calculations. The imino-supported 1,3-disilaallene oxide can react with low-pressure CO₂ to a disila-2,4-furandione; with increased CO₂ pressure, a 6-membered ring, disila-bislactone is formed. Their formation mechanisms were investigated via DFT calculations. Reaction of CO₂ with 1,3-disilaallene oxide was compared to the imino(silyl)disilene reacting with CO₂ in a [2 + 2] cycloaddition.