Main group metal hydrides are interesting research targets in inorganic chemistry. For example, alkali metal pnictogenides (MEH₂, M = alkali metal, E = N, P, As) are important starting materials in this field. They provide access to, e.g., a variety of phosphorus and arsenic compounds. The analogous antimony chemistry, however, is less accessible. Potassium antimonide (KSbH₂), for example, is unstable, which prevents its isolation and hinders its use as a transfer reagent for SbH₂ groups.

Carsten von Hänisch, University of Marburg, Germany, and colleagues have developed an approach for the synthesis and isolation of alkali metal antimonides. The team synthesized antimonides of the type [M(L)_xSbH₂] (M = Li, Na, K, Rb, Cs; L = pmdta, crown ether; pmdta = pentamethyldiethylentriamine). They started from stibine (SbH₃), which was reacted with n-butyllithium and M(hmds) (hmds = hexamethyldisilazane) or MO^tBu in the presence of pmdta.

The resulting compounds of the type [Li(pmdta)_xSbH₂] decompose at temperatures above –50 °C. The use of an appropriate crown ether instead of pmdta allowed the team to isolate the desired alkali metal antimonides in the form [M(crown ether)_xSbH₂]. These products (example pictured) are stable at room temperature (except for the lithium compound), and were fully characterized. In addition, the researchers prepared the 1,4-dioxane adduct [Na(dioxane)_xSbH₂], which was used as a starting compound for the synthesis of the first primary silylstibane, (Me₃Si)₃SiSbH₂.

• Synthesis and Application of Alkali Metal Antimonide ‐ A New Approach to Antimony Chemistry,
  Kevin Dollberg, Selina Schneider, Roman-Malte Richter, Tobias Dunaj, Carsten von Hänisch,
  Angew. Chem. Int. Ed. 2022.
  https://doi.org/10.1002/anie.202213098