Insertion reaction of carbon dioxide into Sn-OR bond. Synthesis, structure and DFT calculations of di- and tetranuclear isopropylcarbonato tin(IV) complexes

The reaction of carbon dioxide with the stannane (Bu2Sn)-Bu-n((OPr)-Pr-i)(2) and distannoxane [Bu-n(2)((PrO)-Pr-i) Sn](2)O leads to the selective insertion into one Sn - (OPr)-Pr-i bond generating the corresponding (Bu2Sn)-Bu-n((OPr)-Pr-i)(OCO2 Pr-i) and Bu-n(2)((PrO)-Pr-i) SnOSn(OCO2 Pr-i)Bu-n(2) species. Both compounds are characterised by multinuclear NMR, FT-IR and single-crystal X-ray crystallography. In the solid state, they adopt a dimeric arrangement with bridging isopropoxy and terminal isopropylcarbonato ligands. The X-ray crystal structure of the dinuclear stannane shows that the Sn2O2 ring and the two Sn - OCO2C fragments are nearby coplanar. The same holds for the ladder-type tetranuclear distannoxane. The dimeric structures are also evidenced by solution NMR in non-coordinating solvents. Interestingly, the assignment of the exo and endo tin resonances of the dimeric distannoxane is unambiguous using a labeled (CO2)-C-13 experiment. The stability of the dimeric association has been probed in the stannane series on the basis of DFT calculations.