Copping Roy, Jonasson Leif, Gaunt Andrew J, Drennan Dennis, Collison David, Helliwell Madeleine, Pirttijarvi Ross J, Jones Chris J, Huguet Anne, Apperley David C, Kaltsoyannis Nikolas, May Iain
Centre for Radiochemistry Research, School of Chemistry, The University of Manchester, UK.
Inorg Chem. 2008 Jul 7;47(13):5787-98. doi: 10.1021/ic800101t. Epub 2008 Jun 3.
We report the synthesis, spectroscopic and structural characterization, and computational analysis of a series of phosphomolybdate complexes with tetravalent metal cations. The reaction between Ce (IV) and Th (IV) with phosphomolybdate at the optimum pH for the stabilization of the lacunary heteropolyoxometalate anion, [PMo 11O 39] (7-), results in the formation of compounds containing the anions [Ce(PMo 11O 39) 2] (10-) and [Th(PMo 11O 39) 2] (10-), respectively. Single crystal X-ray diffraction analysis was performed on salts of both species, Cs 10[Ce(PMo 11O 39) 2].20H 2O and (NH 4) 10[Th(PMo 11O 39) 2].22H 2O. In both anionic complexes the f-block metal cation is coordinated to the four unsaturated terminal lacunary site oxygens of each [PMo 11O 39] (7-) anion, yielding 8 coordinate sandwich complexes, analogous to previously prepared related complexes. Spectroscopic characterization points to the stability of these complexes in solution over a reasonably wide pH range. Density functional analysis suggests that the Ce-O bond strength in [Ce(PMo 11O 39) 2] (10-) is greater than the Th-O bond strength in [Th(PMo 11O 39) 2] (10-), with the dominant bonding interaction being ionic in both cases. In contrast, under similar reaction conditions, the dominant solid state Zr (IV) and Hf (IV) complexes formed contain the anions [Zr(PMo 12O 40)(PMo 11O 39)] (6-) and [Hf(PMo 12O 40)(PMo 11O 39)] (6-), respectively. In these complexes the central Group 4 d-block metal cations are coordinated to the four unsaturated terminal lacunary site oxygens of the [PMo 11O 39] (7-) ligand and to four bridging oxygens of a plenary Keggin anion, [PMo 12O 40] (3-). In addition, (NH 4) 5{Hf[PMo 12O 40][(NH 4)PMo 11O 39]}.23.5H 2O can be crystallized as a minor product. The structure of the anion, {Hf[PMo 12O 40][(NH 4)PMo 11O 39]} (5-), reveals coordination of the central Hf (IV) cation via four bridging oxygens on both the coordinated [PMo 11O 39] (7-) and [PMo 12O 40] (3-) anions. Unusually, the highly charged lacunary site remains uncoordinated to the Hf metal center but instead interacts with an ammonium cation. (31)P NMR indicates that complexation of the Keggin anion, [PMo 12O 40] (3-), to Hf (IV) and Zr (IV) will stabilize the Keggin anion to a much higher pH than usually observed.
我们报告了一系列含四价金属阳离子的磷钼酸盐配合物的合成、光谱和结构表征以及计算分析。在有利于缺位杂多金属氧酸盐阴离子[PMo₁₁O₃₉]⁷⁻稳定的最佳pH值下，铈（IV）和钍（IV）与磷钼酸盐反应，分别生成了含有阴离子[Ce(PMo₁₁O₃₉)₂]¹⁰⁻和[Th(PMo₁₁O₃₉)₂]¹⁰⁻的化合物。对这两种物质的盐Cs₁₀[Ce(PMo₁₁O₃₉)₂]·20H₂O和(NH₄)₁₀[Th(PMo₁₁O₃₉)₂]·22H₂O进行了单晶X射线衍射分析。在这两种阴离子配合物中，f区金属阳离子均与每个[PMo₁₁O₃₉]⁷⁻阴离子的四个不饱和末端缺位位点氧原子配位，形成8配位夹心配合物，类似于先前制备的相关配合物。光谱表征表明这些配合物在相当宽的pH范围内在溶液中具有稳定性。密度泛函分析表明，[Ce(PMo₁₁O₃₉)₂]¹⁰⁻中的Ce - O键强度大于[Th(PMo₁₁O₃₉)₂]¹⁰⁻中的Th - O键强度，在这两种情况下，主要的键合相互作用均为离子键。相比之下，在类似反应条件下，形成的主要固态锆（IV）和铪（IV）配合物分别含有阴离子[Zr(PMo₁₂O₄₀)(PMo₁₁O₃₉)]⁶⁻和[Hf(PMo₁₂O₄₀)(PMo₁₁O₃₉)]⁶⁻。在这些配合物中，第4族d区中心金属阳离子与[PMo₁₁O₃₉]⁷⁻配体的四个不饱和末端缺位位点氧原子以及完整的Keggin阴离子[PMo₁₂O₄₀]³⁻的四个桥连氧原子配位。此外，(NH₄)₅{Hf[PMo₁₂O₄₀][(NH₄)PMo₁₁O₃₉]}.23.5H₂O可以作为次要产物结晶出来。阴离子{Hf[PMo₁₂O₄₀][(NH₄)PMo₁₁O₃₉]}⁵⁻的结构揭示了中心铪（IV）阳离子通过配位的[PMo₁₁O₃₉]⁷⁻和[PMo₁₂O₄₀]³⁻阴离子上的四个桥连氧原子进行配位。不同寻常的是，高电荷的缺位位点未与铪金属中心配位，而是与一个铵阳离子相互作用。³¹P NMR表明，Keggin阴离子[PMo₁₂O₄₀]³⁻与铪（IV）和锆（IV）的络合将使Keggin阴离子在比通常观察到的更高的pH值下保持稳定。
