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

摘要

The synergistic effect of trivacant B-α-Ge W_(9)O_(34)fragments as structure-directing agents and inorganic B-O segments as intramolecular decoration afforded an unprecedented 28-Ni-added huge cluster K_(2)Na_(14)H_(10)[{Ni_(6)(OH)_(3)(H_(2)O)_(6)(Ge W_(9)O_(34))}{Ni_(8)-(μ_(6)-O)(OH)_(3)(H_(2)O)(BO(OH)_(2))(B_(2)O_(3)(OH)_(2))(Ge W_(9)O_(34))_(2)}]_(2)·46H_(2)O(1)under hydrothermal conditions.The polyoxoanion of 1contains two half-units,[{Ni_(6)(OH)_(3)(H_(2)O)_(6)(Ge W_(9)O_(34))}{Ni_(8)(μ_(6)-O)(OH)_(3)(H_(2)O)(BO(OH)_(2))(B_(2)O_(3)(OH)_(2))(Ge W_(9)O_(34))_(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)(H_(2)O)_(6)(B-α-Ge W_(9)O_(34))({Ni_6Ge W_(9)})and a previously unobserved sandwiched Ni_(8)(μ_(6)-O)(OH)_(3)(H_(2)O)(BO(OH)_(2))(B_(2)O_(3)-(OH)_(2))(B-α-Ge W_(9)O_(34))_(2)({(Ni_(8)BB_(2))@(Ge W_(9))_(2)}),in which the{Ni_(8)BB_(2)}cluster contains a Lindqvist-type{Ni_(6)}core capped by two Ni O_(6)octahedra and further decorated by a BO(OH)_(2)({B})group and a binuclear B_(2)O_(3)(OH)_(2)({B_(2)})cluster.Furthermore,1 as a heterogeneous catalyst,has good catalytic activity for Knoevenagel condensation under mild reaction conditions.