Syntheses, Structures And Properties Of Transition-Metal-Substituted Polyoxoniobate Derivatives

Under appropriate conditions, six novel polyoxoniobates were obtained by the reaction of basicligands, transition metal cations and hexaniobate K₇HNb₆O₁₉·nH₂O, which were fully characterized byelemental analyses, X-ray powder diffraction (XRPD), UV spectroscopy, IR spectroscopy, magneticproperty, EDX-SEM, thermogravimetric analyses and single-crystal X-ray diffraction analyses.1. A gaint36-niobium [H₂₀Co₁₄O₈(H₂O)168(Nb₆O₁₉)6]containing fourteen cobalt(II) ions wassynthesized by the hydrothermal treatment, Na₁₆[H₂0Co₁₄O₈(H₂O)₈(Nb₆O₁₉)₆]77H₂O (1). The giantcompound1with the dimensions of16.1×16.9consists of a novel {Co14O8(H₂O)8} clusteranchored by six Lindqvist-type [Nb8–6O19]units in the trigonal antiprism distribution. As far as weknow,1is the first highest-nuclear cobalt-cluster in polyoxoanion chemistry.2. Two novel organic–inorganic hybrids containing [Nb6O]8–19building blocksK₆(Hen)2[HNb₆O₁₉Fe(en)]247H₂O (2) and H₃[Ni(en)₃]₂(HNb₆O₁₉)8H₂O (3) have been successfullysynthesized by using the conventional aqueous solution method.2exhibits an novel[HNb₄–₆O₁₉Fe(en)]unit, which is linked by O Fe O to form a dimer polyanion {[HNb₆O₁₉Fe(en)]₂},the dimer polyanion is further to form2D layer structure via K O K bond. Furthermore, adjacentchains in2is further interacted through K O K bond stacking interactions resulting in athree-dimensional (3D) network.3is constructed from [Nb₆O₁₉]^8–unit and dissociated two [Ni(en)3]2+units.3. Three polyoxoniobates Na₂[Cu(en)₂(H₂O)]{[Cu(en)₂(H₂O)][Cu(en)₂](NaNb₂₄O₇₂H₁₅)(H₂O)5}18H₂O(4),[H₂(en)]₂[Ni(en)₃]₅[H₁₀Nb₂₄O₇₂(H₂O)₃]35H₂O (5) and K₅₇H₃₃(H₉Nb₂₄O₇₂)₆238.5H₂O (6) havebeen succeessfully synthesized using the conventional aqueous solution method or diffusion method. Three compounds exhibit different structure.