Electronic Stabilization Effects: Three New K−In−T (T = Mg, Au, Zn) Network Compounds

The ternary
compounds K34In91.05(9)Mg13.95(9) (I), K34In96.19(6)Au8.81(6) (II), and K34In89.95(1)Zn13.05(7) (III) have been
synthesized by high-temperature means and structurally characterized
by single-crystal X-ray diffraction methods. All are analogues of
earlier products in which Li is substituted for some In in a hypothetical
K34In105 lattice. They consist of complex three-dimensional
anionic networks built of In12 icosahedra and M28 triply fused icosahedra (M = In or In/T and T = Mg, Au, or Zn).
The K atoms bridge between cluster faces or edges and form K136 clathrate-ΙΙ type networks. Two neighboring M28 units are interconnected by an M atom to form a sandwich complex
(M28)M(M28) in I and II or by a Zn−Zn dimer in (M28)ZnZn(M28) in III. Mixed In/T sites only occur in the M28 portions. Phase stabilization through electronic tuning is present
in all three via substitution of the electron-poorer T elements for
In. Extended Hückel analyses indicate that all metal−metal
bonding within the M28 cluster appears to be optimized
in I and III even though both are metallic.
The size of the substituted element is also important in the structural
features, as is especially shown by the Zn compound.