Crystal structures of [NEt3H]5[XCoIIW11O39]·3H2O (X = P or As)

Abstract

The orthorhombic crystal structures of [NEt₃H]₅[XCo^IIW₁₁O₃₉]·3H₂O for X = P and As have been determined with data collected at room temperature, and for X = P at –100 °C, using Mo-Kα radiation. For the latter the space group is Pna2₁, a= 21.670(11), b= 14.805(4), c= 20.393(5)Å and Z= 4. The structure consists of chains of α-Keggin-type molecules joined by W–O–links aligned in the a-axis direction. The Co/W occupancy at the link is disordered, with 61% Co on one side and 39% on the other. Further probable disorder, by lamellar merohedral twinning on (001) and by misorientation of the triethylammonium ions, has obscured the ethyl groups and the water molecules. In polarized light the crystals are deep wine-red normal to the chains (in the b direction), but nearly colourless in the a and c directions. The structure of the arsenate is similar to that of the phosphate.