Metal Clusters in the Solid State

Abstract

In solid state compounds metal clusters and metal-metal bonded arrays occur in both binary and ternary or quaternary phases. Among transition element compounds, cluster and metal-metal bonded species occur in binary halides (Nb, Ta, Mo, W, Re),^1–8 oxides (Nb, Mo, W, Tc, Re),^1,7,9 chalcogenides (Zr, Nb, Ta, Mo, Re)^7,10–13 and pnictides (Zr, Hf, Nb, Ta, Mo, W, Re).^3,7,10 Ternary and quaternary phases containing a broad representation of metal ions Aⁿ⁺ (or Bⁿ⁺), as in A_n(M_xX_y) or A_mB_n(M_xX_y), or two different anions M_xX_yY_z, as in oxide halides and sulfide halides,¹⁴ are even more abundant. Most recently the J. Corbett and A. Simon groups have demonstrated a prolific chemistry of octahedral cluster species having either a nonmetallic or metallic element strongly bonded in the center of the unit. The “interstitial” element provides electrons in stabilized cluster orbitals resulting from strong interaction of the nonmetal p-orbitals (Be, B, C, N, Al, Si)¹⁵ or metal d-orbitals (Fe, Ru)¹⁶ with cluster orbitals of the same symmetry. Electron poor elements⁷ such as Sc, Y, Ln (lanthanoids) and Zr can thereby be induced to form stable clusters, e.g., Cs₃Zr₆Cl₁₆C, Y₆I₁₀Ru, Gd₁₀Cl₁₈(C₂)₂ and Sc(Sc₆I₁₂(B, C)).