Krebs-Type {M2(WO2)2[B-β-SbW9O33]2}n- (M = SbIII, (WO3)) Tungstoantimonate Possessing Unique Pseudo-Seesaw Sb-O Structure.

Two new Krebs-type tungstoantimonates (H2en)8H6{[Sb2(WO2)2(B-β-SbW9O33)2][(WO2)2(WO3)2(B-β-SbW9O33)2]}·22H2O (1) and (H2en)7[(WO2)2(WO3)2(B-β-SbW9O33)2]·12H2O (2) were synthesized and characterized. Notably, crystal 1 possesses a specific pseudo-seesaw SbO4 subunit in the central metal belt of [Sb2(WO2)2(B-β-SbW9O33)2]12- species, which is rare in reported Krebs-type polyoxometalates. One of the structural features is that there are two kinds of Krebs-type polyanionic clusters in crystal 1 labeled as {(WO2)2(WO3)2(B-β-SbW9O33)2} (part A) and {Sb2(WO2)2(B-β-SbW9O33)2} (part B), respectively. The subunits A and B are alternately connected through Sb-O-W bonds into a chain-like structure of inorganic clusters. Moreover, the catalytic property of crystals 1 and 2 for electron-transfer reaction were investigated by transferring K3[Fe(CN)6] into K4[Fe(CN)6].