The crystal and molecular structures of Ce 6Mo 10O 39 and K 2Mo 2O 7-H 2O and the refinement of the “lindqvist” octamolybdate (NH 4) 4Mo 8O 26-4H 2O

Abstract

Crystals of Ce 6Mo 10O 39 are triclinic, space group P 1 ̄ , z = 2 , with cell dimensions a = 10.148(5) A ̊ , b = 18.764(6) A ̊ , c = 9.566(5) A ̊ , α = 103.12(7) °, β = 78.07(7) °, γ = 107.69(7) ° . The structure was solved by direct methods using diffractometer data and was refined by least squares and Fourier methods to R 0.039 for 3113 reflections. The structure is of a new type and comprises eight [MoO 4] 2− tetrahedra and one [Mo 2O 7] 2− unit of two cornershared tetrahedra. The cerium(III) atoms have irregular eight-fold coordination. Crystals of K 2Mo 2O 7-H 2O are triclinic, space group P 1 ̄ , z = 2 , with cell dimensions a = 7.635(4) A ̊ , b = 8.906(4) A ̊ , c = 7.647(4) A ̊ , a = 109.44(7) °, β = 95.73(6) °, γ = 119.20(7) ° . The structure was solved by Patterson and Fourier methods using diffractometer data, and was refined by least squares techniques to R 0.044 for 1775 reflections. The chain structure of edgeshared octahedral MoO 6 and square pyramidal MoO 5 units is of a new type for dimolybdates. The potassium ions and water molecules are in interchain positions. Ammonium octamolybdate hydrate crystals are triclinic, space group P 1 ̄ , z = 1 , with cell dimensions a = 10.595(5) A ̊ , b = 10.047(4) A ̊ , c = 7.882(4) A ̊ , α = 105.66(5) °, β = 101.08(7) °, γ = 113.40(5) ° . The molybdenum atom positions suggested by Lindqvist were confirmed in a Patterson synthesis and the structure was refined by least squares and Fourier techniques using diffractometer data to a current R 0.08 for 3116 reflections. Lindqvist's structure for the octamolybdate anion has been confirmed. Efforts are being made at present to distinguish between ammonium ions and water molecules.