Carbonyl complexes are very common in coordination chemistry and are used, e.g., in catalysis. However, main group elements generally do not readily form CO complexes. For example, relatively little is known about silicon carbonyl complexes.

Chunming Cui, Nankai University and Haihe Laboratory of Sustainable Chemical Transformations, Tianjin, China, and colleagues have synthesized the first 1,2-disilicon dicarbonyl complex (pictured, Ar = 2,6-ⁱPr₂C₆H₃). The team started from the N-heterocyclic boryl-substituted disilyne (NHB)Si≡Si(NHB) (NHB = [ArN(CMe)₂NAr]B), which was reacted with CO (1 atm) at room temperature without a solvent. This reaction gave the disilicon dicarbonyl complex (pictured) as a red solid in a yield of 85 %.

The disilicon dicarbonyl complex was fully characterized using NMR, IR, and UV-Vis spectroscopy, as well as single-crystal X-ray diffraction. The team also performed density functional theory (DFT) calculations and found evidence for pronounced backbonding from the lone pairs of Si to CO. The dicarbonyl complex can undergo hydrolysis or methanolysis to give the corresponding disilacyclobutene hydroxyl derivatives via a C–C coupling.

• Disilicon Dicarbonyl Complex: Synthesis and Protonation of CO with O–H Bond,
  Yazhou Ding, Jianying Zhang, Yang Li, Chunming Cui,
  J. Am. Chem. Soc. 2022.
  https://doi.org/10.1021/jacs.2c10599