A new 28-Ni-added poly(polyoxometalate) with B atoms: synthesis, structure and catalysis for Knoevenagel condensation

The synergistic effect of trivacant B-alpha-GeW9O34 fragments as structure-directing agents and inorganic B-O segments as intramolecular decoration afforded an unprecedented 28-Ni-added huge cluster K2Na14H10[{Ni-6(OH)(3)(H2O)(6)(GeW9O34)}{Ni-8-(mu(6)-O)(OH)(3)(H2O)(BO(OH)(2))(B2O3(OH)(2))(GeW9O34)(2)}](2)center dot 46H(2)O (1) under hydrothermal conditions. The polyoxoanion of 1 contains two half-units, [{Ni-6(OH)(3)(H2O)(6)(GeW9O34)}{Ni-8(mu(6)-O)(OH)(3)(H2O)(BO(OH)(2))(B2O3(OH)(2))(GeW9O34)(2)}](13-), which joined together via Ni-O=W linkages. The most fascinating feature is that each half-unit can be regarded as the fusion of an Ni-6(OH)(3)(H2O)(6)(B-alpha-GeW9O34) ({Ni6GeW9}) and a previously unobserved sandwiched Ni-8(mu(6)-O)(OH)(3)(H2O)(BO(OH)(2))(B2O3-(OH)(2))(B-alpha-GeW9O34)(2) ({(Ni8BB2)@(GeW9)(2)}), in which the {Ni8BB2} cluster contains a Lindqvist-type {Ni-6} core capped by two NiO6 octahedra and further decorated by a BO(OH)(2) ({B}) group and a binuclear B2O3(OH)(2) ({B-2}) cluster. Furthermore, 1 as a heterogeneous catalyst, has good catalytic activity for Knoevenagel condensation under mild reaction conditions.

Automated summary

The combination of organic B-alpha-GeW9O34 and inorganic B-O segments resulted in the formation of a huge cluster K2Na14H10[{Ni-6(OH)(3)(H2O)(6)(GeW9O34)}{Ni-8-(mu(6)-O)(OH)(3)(H2O)(BO(OH)(2))(B2O3(OH)(2))(GeW9O34)(2)}](2)center dot 46H(2)O under hydrothermal conditions. The cluster contains two half-units joined together through Ni-O=W linkages. The cluster shows promising catalytic activity for Knoevenagel condensation under mild reaction conditions.