Reductive cleavage of Zn–C bonds by group 14 Zintl anions: synthesis and characterisation of [E9ZnR]3− (E = Ge, Sn, Pb; R = Mes, iPr)

Abstract

The reaction of ethylenediamine solutions of K₄E₉ (E = Ge, Sn, Pb) with diaryl and dialkyl organozinc reagents ZnMes₂ and ZnⁱPr₂ yielded the functionalized Zintl ions, closo-[E₉ZnR]³⁻ (R = Mes: E = Ge (1), Sn (2), Pb (3); R = ⁱPr: E = Ge (4), Sn (5), Pb (6)). These reactions proceed via reductive zinc–carbon bond activation of the organometallic reagents by the free solvated electrons present in ethylenediamine solutions of intermetallic Zintl phases. The functionalized cluster anions 1, 2 and 4–6 were characterized in the solid-state as [K(2,2,2-crypt)]⁺ salts by single-crystal X-ray diffraction and elemental analysis, while the presence of all six cluster anions in solution was confirmed by ¹H and ¹³C{¹H} NMR spectroscopy and electrospray mass spectrometry.