A silicon–carbonyl complex stable at room temperature

Main-group-element compounds with energetically high-lying donor and low-lying acceptor orbitals are able to mimic chemical bonding motifs and reactivity patterns known in transition metal chemistry, including small-molecule activation and catalytic reactions. Monovalent group 13 compounds and divalent group 14 compounds, particularly silylenes, have been shown to be excellent candidates for this purpose. However, one of the most common reactions of transition metal complexes, the direct reaction with carbon monoxide and formation of room-temperature isolable carbonyl complexes, is virtually unknown in main-group-element chemistry. Here, we show the synthesis, single-crystal X-ray structure, and density functional theory computations of a room-temperature-stable silylene carbonyl complex [L(Br)Ga] 2 Si:–CO (L = HC[C(Me)N(2,6- i Pr 2 -C 6 H 3 )] 2 ), which was obtained by direct carbonylation of the electron-rich silylene intermediate [L(Br)Ga] 2 Si:. Furthermore, [L(Br)Ga] 2 Si:–CO reacts with H 2 and PBr 3 with bond activation, whereas the reaction with cyclohexyl isocyanide proceeds with CO substitution. Compounds of main-group elements rarely undergo direct carbonylation reactions. Now, an electron-rich silylene intermediate has been shown to readily react with CO to form a silylene carbonyl complex that is stable at room temperature. This complex engages in CO substitution as well as oxidative addition reactions.