New {Co9} cluster-added banana-shaped polyoxometalate modified by B atom

In this study, a new {Co9} cluster-added polyoxometalate (POM) Cs3K4Na5H6[BO(OH)2Co9O(OH)(H2O)3(GeW6O26)(B-α-GeW9O34)2]·22H2O (1) was successfully synthesized in the presence of inorganic boron sources under hydrothermal conditions. Its structural characterizaiton is realized using single-crystal X-ray diffraction, infrared spectroscopy, thermogravimetric analysis, and powder X-ray diffraction. Compound 1 represents the first Co-added POM bonded by a B atom, and its polyoxoanion is constructed by fusing together with one hexalacunary GeW6O26 and two trilacunary B-α-GeW9O34 fragments in an unprecedented V-shaped {Co9} cluster. Additionally, compound 1 is an efficient catalyst for accelerating the Knoevenagel condensation of various aldehydes with malonitrile.