Reactions of a diborylstannylene with CO₂and N₂O: diboration of carbon dioxide by a main group bis(boryl) complex

The reactions of the boryl-substituted stannylene Sn{B(NDippCH)₂}₂(1) with carbon dioxide have been investigated and shown to proceedviapathways involving insertion into the Sn-B bond(s). In the first instance this leads to formation of the (boryl)tin(ii) borylcarboxylate complex Sn{B(NDippCH)₂}{O₂CB(NDippCH)₂} (2), which has been structurally characterized and shown to feature a κ²mode of coordination of the [(HCDippN)₂BCO₂]⁻ligand at the metal centre.2undergoes B-O reductive elimination in hexane solution (in the absence of further CO₂) to give the boryl(borylcarboxylate)ester {(HCDippN)₂B}O₂C{B(NDippCH)₂} (3)i.e.the product of formal diboration of carbon dioxide. Alternatively,2can assimilate a second equivalent of CO₂to give the homoleptic bis(borylcarboxylate) Sn{O₂CB(NDippCH)₂}₂(4), which can be preparedviaan alternative route from SnBr₂and the potassium salt of [(HCDippN)₂BCO₂]⁻, and structurally characterized as its DMAP (N,N-dimethylaminopyridine) adduct. Structural and reactivity studies also point to the possibility for extrusion of CO from the [(HCDippN)₂BCO₂]⁻fragment to generate the boryloxy system [(HCDippN)₂BO]⁻, a ligand which can be generated directly from1viareaction with N₂O.