Lead and tin β-diketiminato amido/anilido complexes: competitive nucleophilic reactivity at the β-diketiminato γ-carbon.

The β-diketiminatolead(II)-amido and -anilido complexes, [(BDI)Pb(NRR')] (BDI = [{N(2,6-iPr2C6H3)C(Me)}2CH]; NRR' = NH(2,6-iPr2C6H3), N(iPr)2), react at the amido/anilido nitrogen atom with simple saturated electrophiles such as methyltriflate. Addition of unsaturated electrophiles to these complexes either results in the formation of a complex mixture of products, or in the case of phenylisocyanate, reaction at the γ-carbon of the β-diketiminato ligand to form a complex that is the net result of a nucleophilic attack by the γ-carbon atom of the β-diketiminato ligand at the electrophilic carbon centre of phenylisocyanate. As this reactivity contrasts with that of β-diketiminatolead(II) alkoxo complexes as well as β-diketiminatotin(II) alkoxo complexes, we examined the reactivity between phenylisocyanate and the isostructural β-diketiminatotin(II)-amido and -anilido complexes. Reactivity at the γ-carbon was also observed in these systems. Density functional calculations were performed to help understand the differences in reactivity.