A new preparative approach to HgPbP ₁₄ structure type materials: Crystal structure of Cu _0.73(1)Sn _1.27(1)P ₁₄ and characterization of M _1-xSn _1+xP ₁₄ (M = Cu, Ag) and AgSbP ₁₄

A new preparative approach, using main group iodides as mineralization agents, was developed to prepare bulk quantities of HgPbP ₁₄ [(M1)(M2)P ₁₄] type polyphosphides containing group 11 cations on the M1 and main group elements Sn or formerly unseen Sb on the M2 position. The known (M1) ²⁺:(M2) ²⁺ combination of cations is extended with the combination (M1) ¹⁺:(M2) ³⁺ in AgSbP ₁₄. A single crystal structure determination was performed for Cu _1-xSn _1+xP ₁₄. Cu _0.73(1)Sn _1.27(1)P ₁₄ crystallizes orthorhombically, space group Pnma (No. 62) with lattice constants a = 12.513(2) Å, b = 9.800(1) Å, c = 10.445(1) Å, V = 1280.8(3) Å ³ and Z = 4. Small differences in the cell parameters between the single crystal and powder diffraction experiments of CuSnP ₁₄ are probably due to a small homogeneity range. Tetravalent tin postulated beside divalent tin for isostructural Au _0.64Sn _1.36P ₁₄ could not be detected by ¹¹⁹Sn-Mössbauer spectroscopic experiments for the copper tin polyphosphide. An ionic description like [(M1 ⁺) _1-x(M2 ⁴⁺)] ²⁺ [(M2 ²⁺)(P ⁰) ₁₀(P ^1-) ₄] ^2- with x = 0.33 according to a Zintl-Klemm concept has to be substituted by a more covalent description of [(M1 ⁺) _1-x(M2 ²⁺) _x] ^(1+x)+- [(M2 ²⁺)(P ₁₄)] ^(1+x)- for the copper tin polyphosphide.