An isolable stannaimine and its cycloaddition/metathesis reactions with carbon dioxide.

An N-heterocyclic stannylene :Sn(NON Ad ) (NON Ad = [O(SiMe 2 NAd) 2 ] 2- , Ad = 1-adamantyl), reacts rapidly with 2,4,6-tricyclohexylphenyl azide (TCHP)N 3 , affording a stannaimine, (NON Ad )SnN(TCHP). Solutions of (NON Ad )SnN(TCHP) react immediately with carbon dioxide (CO 2 ) to give a [2+2]-cycloaddition product, which, upon heating, subsequently engages in a metathesis process to give [Sn(NON Ad )(μ-O)] 2 and the bulky isocyanate, (TCHP)NCO.