Modified polyoxometalate: A novel bi-antimony capped, highly reduced alpha-Keggin polyoxoanion, [(PMo7Mo5O40Sb2III)-Mo-V-O-VI](4-)

A novel modified POM [(H4PMo7Mo5O40Sb2III)-Mo-V-O-VI](im)(2)center dot 2H(2)O (im = imidazole) (1) has been hydrothermally synthesized from the system Sb2O3-H3PMo12O40-H2C2O4-im and characterized by elemental analysis, IR, UV-Vis, XPS, TGA and single crystal X-ray diffraction. The highly reduced polyoxoanion [(PMo7Mo5O40Sb2III)-Mo-V-O-VI](4-) represents the first example of bi-antimony capped alpha-Keggin phosphomolybdate, in which the Sb atoms exhibit novel Psi-rhombic pyramidal {SbO4E} hemidirected coordination geometry with coordination number 4. (C) 2009 Elsevier B.V. All rights reserved.