Heteropolymetalate clusters of the subvalent main group elements BiIII and SbIII

The heteropolyanions [Bi2W22O74(OH)(2)](12-) (1) and [X2W20M2O70(H2O)(6)]((14-2n)-) (X = Sb3+, Bi3+; Mn+ = Fe3+, Co2+, Zn2+) (2-7) have been synthesized as alkali metal and ammonium salts, respectively, and characterized by elemental analysis, infrared spectroscopy, and X-ray crystallography. These tungsto bismutates and antimonates reveal one common feature: the trivacant beta-B-XW9O33 Keggin fragment as the structural building unit. Formally, the unit can be derived from the Keggin structure by removing one trimetalate fragment, W3O13, and a 60 degrees rotation of one of the remaining W3O13 subunits around the X-O-W3X bond vector (the subscript indicates the element(s) bonded). The unshared pair of electrons of the respective central, pyramidally coordinated heteroatom Sb-III or Bi-III prevents formation of the complete spherical structure. In the presented heteropolyanions 1-7, two beta-B-XW9O33 units are connected by two WO2 groups. Further stabilization of this hitherto unknown bis-decatungsto ion [X2W20O70](14-) is reached either by addition of two formal fac-WO3 anti-Lipscomb's rule units to give the bis-undecatungsto bismutate [Bi2W22O74(OH)(2)](12-) (1) or by addition of two Mn+(H2O)(3) groups (Mn+ = Fe3+, Co2+, Zn2+) forming the large, transition-metal-substituted heteropolyanion clusters [X2W20M2O70(H2O)(6)]((14-2n)-) (X = Sb3+, Bi3+; Mn+ = Fe3+, Co2+, Zn2+) (2-7).