Controlled Triol-Derivative Bonding and Decoration Transformation on Cu-Centered Anderson–Evans Polyoxometalates

To create new types of organic ligands
covalently grafted onto polyoxometalates and identify the reaction
mechanism, we selected CuII as the central heteroatom for
the synthesis of a series of disklike Anderson–Evans clusters
bearing different triol derivatives on both their faces via one-pot
and/or step-by-step routes. By using a [(n-C4H9)4N]4[Mo8O26] precursor
cluster and copper acetate as the starting materials, several organically
modified χ isomers with CuII heteroatom centers were
obtained. Starting from a [(n-C4H9)4N]2[Mo2O7] subcluster, however,
a half-malposition coordination fashion of triol ligands with a δ
isomer on one face and a χ isomer on the other face of the Anderson–Evans
cluster was obtained. By changing the reaction solvent from acetonitrile
to methanol, we realized a secondary organic modification of the triol-grafted
clusters and obtained a triol ligand/methanol codecoration on the
Anderson–Evans polyoxometalate. In addition, by changing the
reaction environment, we succeeded in modulating the transformation
of triol ligands from one site to another on the polyoxometalate cluster.
Importantly, by control of the reaction condition, the methanol molecules
were also taken off from the cluster.