RE-POM Clusters

Two isomers [al-P2Wi706i] ° and [a2-P2Wi706i] ° can be derived from the parent Wells-Dawson anion [a-P2Wi8062] by removal of a belt or cap W = Od unit, respectively. Complexes of RE ions with a lacunary [a-P2Wi706i] ° anion were first reported by Peacock and Weakley in 1971, which is now known as [RE(a2-P2Wi706i)2] - The complex of the al isomer, [RE(al-P2Wi706i)] , has also been prepared, although it could not be isolated. Until 

The structures with four or more RE atoms sandwiched by POM units have also been reported. [ Y4( X3-0H)4(H20)8 (a-P2Wi5056)2] - and [ Yb6( X6-0)( X3-0H)6(H20)6  

Different to the above-mentioned compounds with mononuclear RE ion at the center, [H6Ce2(H20)Cl(W50i8)3] is an example of a polyanion with a central dinuclear RE unit. [H6Ce2(H20)Cl(W50i8)3] has an approximate C3 symmetry. The anion consists of a dinuclear cerium unit Ce20i3(H20)Cl and 15-memberedring of WOe units constructed by three 

RE-POM clusters with a large size are normally composed of several equivalent or nonequivalent POM building units (for example, XW9 and XWio in a large RE-tungstate cluster, M07 and Mog in a large RE-molybdate cluster) with RE atoms as linkers or decorate groups. 

Trivacant Keggin fragments [B-a-X(III)W9033] (X=As, Sb, Bi), formed when the heteroatom X possesses a lone pair of electrons, is the most common building unit of large 

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Ce(IV)03)3(H20)2(A-a-PW9034)2] [23] is an example of sandwich type RE-POM clusters with three central RE atoms. The structure is composed of two trivacant Keggin anions [A-a-PW9034] and a central belt of three cerium atoms alternating with three oxygen atoms. Three cerium atoms have two types of coordination one is six-coordinated while... 

At the end of this section, there are two points that should be stated, (i) The RE-POM clusters described here are mainly those with complete structural characterization among a... 

Various POM clusters can act as building units and are connected by RE linkers into one-, two-, three-dimensional structural RE-POM complexes. In reported extending structural RE-POMs complexes, various POM building blocks participate in the structural construction as discrete clusters, whereas RE linkers participate in the structural construction as diverse modes, including hydrated RE ions, discrete RE-organo clusters, and one-, two-, three-dimensional structural RE-organopolymers. 

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