cqvip:The reddish--brown prismatic crystal of the title compoundK6PMo7V2W3O40., (H2O)16,, (Mr.= 2518. 8) crystallizes in tetragonal system, space groupP4n2(# 118), with a= 14. 083(1), b= 14. 083(2), c= 12. 572(3) A, V=2493. 6(l)A3 D.= 2. 72 g/cm’3 Z= 2.λ(MoKa) = 0. 71073 A, μ= 108. 9 cm-l, F(000) 1840, final R= 0. 038 and Rw= 0. 050 for 1388 observed reflections with I>3. 0σ(I).. The title compound contains heteropolyanion [(Mo7W3,V2)PO40]6- linked together byK+ ions and water molecules. The heteropolyanion has the well--known Keggin structure. The 12 metal atoms in the cage of the anion comprise seven Mo, three W and twoV atoms in a random distribution. The M--M (M= 7/12 Mo+ l/4W + l/6 V) average distance in the anion is 3. 535 A. The P--M distance is 3. 537A. The P--O distance is 1. 54 A, and the M--O distances are from 1. 64 to 2. 42A for O atoms coordinated to one, two and three M atoms respectively. Potassium ions are coordinated byeight O atoms from the anion and water molecules.
展开▼
