Multicomponent Polyanions. 54. Crystal Structure of Tetracaesium Monohydrogen Phosphato(phosphito)pentamolybdate Dihydrate, Cs4[H(HP)PMo5O22].2H2O.

The crystal structure of tetracaesium monohydrogen phosphato (phosphito)pentamolybdate dihydrate was determined by single-crystal X-ray diffraction. The compound crystallises in the triclinic space group P (1) over bar, a=10.284(2), b= 10.791(2) and c=13.047(3) Angstrom, alpha=109.34(2), beta=99.92(2) and gamma=102.85(2)degrees, V=1283.4(5) Angstrom(3) and Z=2. The final R-values are R=0.066, wR=0.039 and S=1.3667. The H(HP)PMo5O224- anion has common features with the Strandberg X2M5-type heteropolyanion. The five MoO6 octahedra form a five-membered ring by one corner-sharing and four edge-sharing connections, and the tripodal phosphate and phosphite ligands protrude from each side of this ring in opposite directions. This is the first example of the structure of the heteropolyoxometalate having both P-III and P-V as heteroatoms.