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首页> 外文期刊>Crystal growth & design >Lithium polyniobates. A lindqvist-supported lithium-water adamantane cluster and conversion of hexaniobate to a discrete keggin complex
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Lithium polyniobates. A lindqvist-supported lithium-water adamantane cluster and conversion of hexaniobate to a discrete keggin complex

机译：聚铌酸锂。受lindqvist支持的锂-水-金刚烷簇，并将己铌酸盐转化为离散的egggin复合物

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A Li7K salt of [Nb6O19](8-) and a Li13K salt of [SiNb12(OH)(2)O-38](14-) have been prepared and characterized by single-crystal X-ray diffraction and Li-6 MAS NMR. The structure of Li7K[Nb6O19]center dot 15H(2)O (a = 9.859(10) A, b = 17.500(17) A, c = 17.384(17) A, beta = 91.609(16)degrees, monoclinic, P2(1)/c, R1 = 4.94% based on 5343 reflections) consists of a super-octahedron of six edge-sharing NbO6 octahedra capped by a Li4O10 adamantane-like structure. The Li-6 MAS NMR data are consistent with five tetrahedral Li+ sites (delta = 0.20 ppm) and two octahedral Li+ sites (delta = -1.38 ppm). The reaction of Li7K[Nb6O19]center dot 15H(2)O and Si(OC2H5)(4) yields Li13K[SiNb12(OH)(2)O-38]center dot 17H(2)O (a = 20.341(4) A, b = 10.735(2) A, c = 21.438(4) A, beta = 105.41(3)degrees, monoclinic, P2(1)/c, R1 = 6.49% based on 6161 reflections), an alpha-Keggin ion ([SiNb12(OH)(2)O-38](14-)) linked by Li+ cations and a single K+ cation. Interpretation of structural data suggests that Li+ has weaker ion pairing to [Nb6O19](8-) in the solid state than do Na+, K+, Rb+, or Cs+ (i.e., ion pairing increases with an increase in the ionic radius of the alkali metal cation). Given the high charge density of [Nb6O19](8-), the increase in solubility of alkali salts of [Nb6O19](8-) in water from Li+ to Cs+ (Li+ < Na+ < K+ < Rb+ < Cs+) suggests that similar ion pairing in solution decreases the effective charge of the polyanion and increases stability as long as charge neutralization is not achieved. In addition, Li+ facilitates the formation of discrete [SiNb12(OH)(2)O-38](14-) clusters from a [Nb6O19](8-) precursor; the analogous reaction with Na-7[HNb6O19] produces a Keggin chain material.
机译：制备了[Nb6O19]（8-）的Li7K盐和[SiNb12（OH）（2）O-38]（14-）的Li13K盐，并通过单晶X射线衍射和Li-6 MAS进行了表征核磁共振。 Li7K [Nb6O19]中心点15H（2）O的结构（a = 9.859（10）A，b = 17.500（17）A，c = 17.384（17）A，beta = 91.609（16）度，单斜，P2 （1）/ c，基于5343次反射，R1 = 4.94％）由六边形NbO6八面体的超八面体组成，并由类似Li4O10的金刚烷结构封端。 Li-6 MAS NMR数据与五个四面体Li +位点（δ= 0.20 ppm）和两个八面体Li +位点（δ= -1.38 ppm）一致。 Li7K [Nb6O19]中心点15H（2）O与Si（OC2H5）（4）的反应产生Li13K [SiNb12（OH）（2）O-38]中心点17H（2）O（a = 20.341（4） A，b = 10.735（2）A，c = 21.438（4）A，beta = 105.41（3）度，单斜晶系，P2（1）/ c，R1 = 6.49％（基于6161次反射），α-Keggin离子（[SiNb12（OH）（2）O-38]（14-））由Li +阳离子和单个K +阳离子连接。结构数据的解释表明，与Na +，K +，Rb +或Cs +相比，固态的Li +与[Nb6O19]（8-）的离子配对较弱（即，离子配对随碱金属离子半径的增加而增加）阳离子）。鉴于[Nb6O19]（8-）的高电荷密度，[Nb6O19]（8-）碱金属盐在水中从Li +到Cs +的溶解度增加（Li +

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