Yttrium Polyoxometalates. Synthesis and Characterization of a Carbonate-Encapsulated Sandwich-Type Complex

Reaction of A-(alpha)-PW9O349- with YCl3 in an aqueous Na2CO3 solution produces a dianion-encapsulated A-type sandwich polyoxometalate, (YOH2)3(CO3)(A-(alpha)-PW9O34)211-. The X-ray structure of this complex reveals that three Y(III) ions are sandwiched between two A-(alpha)-PW9O349- moieties and that a carbonate dianion is encapsulated in the same plane as the three Y (III) atoms. The oxygen atoms of the CO32- are sitting at the midpoints of the sides of the triangle formed by the three Y(III) ions. 31P and 13C NMR studies confirm that this complex is significantly more stable than the analogous A-type sandwich polyoxometalates containing divalent metals.