Samarium Polystibides Derived from Highly Activated Nanoscale Antimony

Zintl ions in molecular compounds are of fundamental interest for basic research and application. Two reactive antimony sources are presented that allow direct access to molecular polystibide compounds. These are Sb amalgam (Sb/Hg) and ultrasmall Sb⁰ nanoparticles (d=6.6±0.8nm), which were used independently as precursors for the synthesis of the largest f-element polystibide, [(Cp*₂Sm)₄Sb₈]. Whereas the reaction of the nanoparticles with [Cp*₂Sm] directly led to [(Cp*₂Sm)₄Sb₈], Sm/Sb/Hg intermediates were isolated when using Sb/Hg as the precursor. These Sm/Sb/Hg intermediates [((Cp*₂Sm)₂Sb)₂(μ-Hg)] and [((Cp*₂Sm)₃(μ⁴,η^1:2:2:2-Sb₄))₂Hg] were synthetically trapped and structurally characterized, giving insight in the formation mechanism of polystibide compounds.