The Hypersilyl Substituent in Heavier Low‐Valent Group 14 Chemistry

Abstract

The isolation of unusual compounds with low‐valent main‐group elements would not have been possible without the development of a series of sterically demanding ligands with bulky substituents. While early literature recognizes the advent of the sterically demanding tris(trimethylsilyl)silyl (SiMe3)3Si‐group, also known as hypersilyl group, to stabilize species with new coordination modes for the main group elements, it has largely been more recent studies that have utilized this group for isolating stable compounds with low‐valent main‐group elements. Such compounds are not only interesting from the structure‐bonding point of view but showcase potential for small molecule activation under ambient conditions. This review will cover the recent developments in stabilizing unusual compounds with group 14 elements using the exceptionally strong σ‐donor properties and pronounced steric effects of the hypersilyl moiety, emphasizing their synthesis, structure, and reactivity.

A Barium Complex of the Silanide SiH3–: Hydride Surrogate and Source of Silicon

“…Barium complexes of bulky silanides were reported by Ruhlandt-Senge already in 2003. , Sarazin recently reported on a tridentate bis­(imino)­carbazolate Dipp Carb ligand that was employed in barium chemistry and prepared among others, a complex bearing a bulky tris­(trimethylsilyl)­silanide ligand . Silyl groups such as tris­(trimethylsilyl)­silyl or tri- tert -butylsilyl are also used in low-valent group 14 chemistry, − but to date no SiH 3 – -substituted tetrylenes are known.…”

Ligand-enforced geometric constraints and associated reactivity in p-block compounds

“…The development of increasingly large substituents for providing kinetic protection of reactive sites has contributed significantly to this approach. [24][25][26][27] Finally, electron-donation can also stabilize non-classical geometries by partial occupation of any lowlying vacant orbitals that are exposed upon distortion (Fig. 1d).…”

Synthesis of Si(IV)- and Ge(II)-Substituted Amines, Hydrazone, and Hydrazine from Hypersilyl Germylene

“…Several research teams have utilized the hypersilyl (–Si­(SiMe 3 ) 3 ) group as a ligand or substituent to stabilize a range of compounds containing low-valent Si atoms or various molecular clusters . This choice is motivated not only by its ability to act as a strong σ-donor and its notable steric bulk, but also by the convenience of readily available precursors and the potential for additional functionalization due to the presence of SiMe 3 moieties . In this line, we have synthesized a series of tetrylenes functionalized with a hypersilyl group − and investigated their reactions with dialkylchlorophosphines.…”

“…6 This choice is motivated not only by its ability to act as a strong σ-donor and its notable steric bulk, but also by the convenience of readily available precursors and the potential for additional functionalization due to the presence of SiMe 3 moieties. 7 In this line, we have synthesized a series of tetrylenes functionalized with a hypersilyl group 8−10 and investigated their reactions with dialkylchlorophosphines. While reactions with silylene produced unsymmetrical disilenes, 11,12 the Ge−Si bond was ruptured in the case of germylene.…”