Low-Coordinate Germylene and Stannylene Heterocycles featuring Sterically Tunable Bis(amido)silyl Ligands

A series of monomeric heterocyclic metallylenes [{<sup><i>i</i></sup>Pr<sub>2</sub>Si(NR)<sub>2</sub>}M:] (M = Ge and Sn; R = Dipp = 2,6-<i><sup>i</sup></i>Pr<sub>2</sub>C<sub>6</sub>H<sub>3</sub> or SiPh<sub>3</sub>) have been prepared. Preliminary atom-transfer chemistry involving the new low-valent germylenes with the chalcogen sources Me<sub>3</sub>NO and S<sub>8</sub> yielded the corresponding dimeric oxo- and sulfido complexes (e.g., [{<i><sup>i</sup></i>Pr<sub>2</sub>Si(NDipp)<sub>2</sub>}Ge(μ-E)]<sub>2</sub>; E = O and S). Structural analyses of the metallylenes and their oxidized products reveal that incorporation of the umbrella-shaped triarylsilyl groups (SiPh<sub>3</sub>) within the NSiN chelate confers additional steric protection about the group 14 centers relative to a Dipp group. The inclusion of sterically modifiable −SiAr<sub>3</sub> (Ar = aryl) units as part of a bis(amido) ligand array represents a new approach in this field and holds considerable promise with regard to attaining increasingly higher degrees of steric bulk.