Structure of the ethylenediaminetetracetatoaquomagnesate(II) ion in a crystalline sodium salt. Comparative stereochemistry of the seven-coordinate chelates of magnesium(II), manganese(II), and iron(III)
Structure of the ethylenediaminetetracetatoaquomagnesate(II) ion in a crystalline sodium salt. Comparative stereochemistry of the seven-coordinate chelates of magnesium(II), manganese(II), and iron(III)
复制标题
结晶钠盐中乙二胺四乙酸水镁酸 (II) 离子的结构。
DOI：
10.1021/ic50126a009
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发表时间：
1973
影响因子：
4.6
通讯作者：
J. Hoard
中科院分区：
文献类型：
--
作者：
J. J. Stezowski;R. Countryman;J. Hoard
Na2 [H2OMgEDTA]- 5h20 （EDTA4-=乙二胺四乙酸酯）在单斜空间群C2中结晶，a= 11.504 (3), b= 9.801 (3), c= 8.816 (3) a, cos ß=-0.3565(3)或ß= 110.88， Z= 2。在计算机控制的四圆衍射仪上用zr滤波的Mo Ka辐射记录衍射强度。在(sin 6)/X< 0.98 A扫描的3800个独立反射中，保留的2791个作为客观观察，为各向异性，全矩阵，最小二乘结构精化提供了21的数据/参数比。七坐标[H2OMgEDTA] 2”离子具有所需的C2对称，携带两对非常长的键，Mg- n = 2.378(2)和Mg-0= 2.270 (3) A，以及相当短的一对键，Mg-0= 2.078 (2) A，以及独特的Mg- oh2键在2.060 (3)A.所有的配位多角体在Mg (II), Mn （II）和Fe （III）的EDTA螯合物中，也在[H]。（DCTA4-= 1,2 -二氨基环己烷- a ', jV ' -四乙酸酯），是Cw五角形双棱柱和Cm单头三角棱柱之间的C2杂化体，但在比例上占主导地位；只有[h2feedta]更适合被归类为五边形双锥体。定性相似的[H2OMgEDTA] 2”和[H2OMgEDTA] -离子之间的定量差异可以总结如下。[H2OMgEDTA] ~（和[h2omfeedta]”）中的键合使配体紧密地包裹在一起，而[H2OMgEDTA] 2”中的键合模式则适合于一种容易包裹的关系模式。镁锰螯合物稳定性常数的较大差异主要是由于阳离子大小的差异；较大的锰离子很好地适应于观察多重桥环体系施加的几何约束。
The salt, Na2 [H2OMgEDTA]-5H20 (EDTA4-= ethylenediaminetetraacetate), crystallizes in the monoclinic space group C2 with a= 11.504 (3), b= 9.801 (3), c= 8.816 (3) A, cos ß=-0.3565 (3) or ß= 110.88, and Z= 2. Diffracted intensities were recorded with Zr-filtered Mo Ka radiation on a computer-controlled four-circle diffractometer. Of the 3800 independ-ent reflections scanned for (sin 6)/X< 0.98 A," 1 the 2791 retained as objectively observed gave a data/parameter ratio of 21 for the anisotropic, full-matrix, least-squares refinement of structure. The seven-coordinate [H2OMgEDTA] 2" ion of re-quired C2 symmetry carries two pairs of very long bonds, Mg-N= 2.378 (2) and Mg-0= 2.270 (3) A, along with a fairly short pair, Mg-0= 2.078 (2) A, and the unique Mg-OH2 bond at 2.060 (3) A. All coordination polyhedra in the EDTA chelates of Mg (II), Mn (II), and Fe (III), as also in [H. OFeDCTA]"(DCTA4-= l, 2-diaminocyclohexane-A', jV’-tetraacetate), are C2 hybrids between a Cw pentagonal bipyramid and the Cm monocapped trigonal prism, but with one or the other predominating in the ratio'\/3: l; only [H2OFeEDTA]" is better classified as pentagonal bipyramidal. The quantitativedif-ferences between the qualitatively similar [H2OMgEDTA] 2" and [H2OFeDCTA]-ions may be summed up as follows. The bonding in [H2OFeDCTA]~(and in [H2OFeEDTA]") enforces very tight packing of the ligands, whereas the bonding pattern in [H2OMgEDTA] 2" is tailored to a pattern of easy packing relations. The large difference in the stability constants of the magnesium and manganese chelates is mostly attributable to the difference in size of the cations; the larger manganese ion is well-adapted to observe the geometrical constraints imposed by the multiply bridged ring system.