Isolation and Reactivity of a Stannabismuthene.

Multiple-bonded compounds involving heavy group 14 elements (Si, Ge, Sn, Pb) and bismuth (Bi), as heavier analogs of imines, have not previously been isolated as stable entities. In this study, we report the successful isolation of a stannabismuthene (2), a Sn/Bi analog of imines, achieved through the kinetic stabilization provided by a bulky terphenyl substituent. The stannabismuthene was synthesized via a one-pot reduction of BiBr3 and carboranyl distannene (1) using two equivalents of KC8 in THF, and it has been unambiguously characterized through spectroscopic analysis, x-ray diffraction, and DFT calculations. This compound features a Sn═Bi double bond, which acts as a π donor, coordinating with AgNTf2 to form a π complex 3. DFT calculations reveal two significant interactions in 3: the donation from the Bi-Sn π-bonding orbital to the 5s orbital of the Ag atom, and the backdonation from the 4d orbital of Ag to the Bi-Sn π* orbital. These interactions conform to the Dewar-Chatt-Duncanson model for π-complexes, highlighting the unique bonding characteristics of stannabismuthene.