| Abstract
| - The influence of the nature of alkali metal cations on the structure of the species obtained from the trivacantprecursor A-α-[SiW9O34]10- has been studied. Starting from the potassium salt 1, K10A-α-[SiW9O34]·24H2O, thesandwich-type complex 2, K10.75[Co(H2O)6]0.5[Co(H2O)4Cl]0.25A-α-[K2{Co(H2O)2}3(SiW9O34 )2]·32H2O, has beenobtained. The crystal structures of these two compounds consist of two A-α-[SiW9O34]10- anions linked by a setof potassium (1) or cobalt plus potassium cations (2), and the relative orientation of the two half-anions is thesame. Attempts to link two A-α-[SiW9O34]10- anions by tungsten atoms instead of cobalt failed whatever the alkalimetal cation. Moreover, the nondisordered structure of Cs15[K(SiW11O39)2]·39H2O is described. Two [SiW11O39]8-anions are linked through a potassium cation with a “trans-oid” conformation, and the potassium occupies a cubiccoordination site.
- The A-α-type sandwich complex [{Co(H2O)2}3(SiW9O34)2]14- is prepared by the reaction of K10A-α-[SiW9O34] with an aqueous solution of CoCl2. This complex is not obtained if the sodium salt Na10A-α-[SiW9O34] is utilized. The solid-state structures of the cobalt complex and K10A-α-[SiW9O34] show that the trivacant species are associated in both cases to form sandwich-like complexes, showing that interaction of the oxygen atoms of the vacancy with cations does not strongly depend on the nature of the cations.
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