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

Reaction of A-α-PW9O349- with YCl3 in an aqueous Na2CO3
solution produces a dianion-encapsulated A-type sandwich polyoxometalate, (YOH2)3(CO3)(A-α-PW9O34)211-. The X-ray structure
of this complex reveals that three Y(III) ions are sandwiched
between two A-α-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.