Beiträge zum Koordinationsverhalten von Oxidionen in anorganischen Feststoffen. III [1] Mn2P2O7, Mn2P4O12 und Mn2Si(P2O7)2 — Kristallzüchtung,Strukturverfeinerungen und Elektronenspektren von Mangan(II)‐Phosphaten

Contributions on the Bonding Behaviour of Oxygen in Inorganic Solids. III [1] Mn₂P₂O₇, Mn₂P₄O₁₂ und Mn₂Si(P₂O₇)₂ — Crystal Growth, Structure Refinements and Electronic Spectra of Manganese(II) Phosphates By chemical vapour transport reactions in a temperature gradient single crystals of Mn₂P₂O₇ (1050 → 950 °C) and Mn₂P₄O₁₂ (850 → 750 °C) have been obtained using P/I mixtures as transport agent. Mn₂Si(P₂O₇)₂ was crystallized by isothermal heating (850 °C, 8d; NH₄Cl as mineralizer) of Mn₂P₄O₁₂ und SiO₂. In Mn₂Si(P₂O₇)₂ [C 2/c, a = 17.072(1)Å, b = 5.0450(4)Å, c = 12.3880(9)Å, β = 103.55(9)°, 1052 independent reflections, 97 variables, R1 = 0.023, wR2 = 0.061] the Mn²⁺ ions show compressed octahedral coordination (d¯_Mn—O = 2.19Å). The mean distance d¯_Mn—O = 2.18Å was found for the radially distorted octahedra [MnO₆] in Mn₂P₄O₁₂ [C 2/c, Z = 4, a = 12.065(1)Å, b = 8.468(1)Å, c = 10.170(1)Å, β = 119.29(1)°, 2811 independent reflections, 85 variables, R1 = 0.025, wR2 = 0.072]. Powder reflectance spectra of the three pink coloured manganese(II) phosphates have been measured. The spectra show clearly the influence of the low‐symmetry ligand fields around Mn²⁺. Observed d—d electronic transition energies and the results of calculations within the framework of the angular overlap model (AOM) are in good agreement. Bonding parameters for the manganese‐oxygen interaction in [Mn²⁺O₆] chromophors as obtained from the AOM treatment (B, C, Trees correction α, e_σ, e_π) are discussed.