Isolation of monomeric MnIII/II-OH and MnIII-O complexes from water:: Evaluation of O-H bond dissociation energies
Isolation of monomeric MnIII/II-OH and MnIII-O complexes from water:: Evaluation of O-H bond dissociation energies
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DOI：
10.1021/ja016741x
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发表时间：
2002-02-20
影响因子：
15
通讯作者：
Borovik, AS
中科院分区：
文献类型：
--
作者：
Gupta, R;MacBeth, CE;Borovik, AS
报道了单体[MnIII/IIH31(OH)]-/2和[MnIIIH31（O)]2配合物的合成和性质，其中[H31]3为三脚配体[（N′-叔丁基脲醛）-N-乙基）]氨基。用H218O进行的同位素标记研究证实了水是末端氧和羟基配体中氧的来源。用x射线衍射法测定了[MnIIIH31(OH)]2和[MnIIIH31(O)]2配合物的分子结构，结果表明，配合物均具有三角双锥体配位几何。[MnIIIH31(O)]2-中的MnIII−O距离为1.771(4)Å，而[MnIIIH31(OH)]2-中的MnIIIH31−O距离为2.059(2)Å。结构研究还表明，[H31]3提供了一个围绕着MnIII−O(H)单元的氢键空腔。用热力学方法计算[MnIIIH31(O−H)] 2和[MnIIIH31(O−H)]-的键解离能分别为77(4)和110(4)kcal/mol。[MnIIIH31(O)]2-配合物的键能小于80 kcal/mol的能力支持了[MnIIIH31(O)]2-配合物的计算值为77 kcal/mol。
The syntheses and properties of the monomeric [MnIII/IIH31(OH)]-/2-and [MnIIIH31(O)]2-complexes are reported, where [H31]3-is the tripodal ligand tris[(N‘-tert-butylureaylato)-N-ethyl)]aminato. Isotope-labeling studies with H218O confirmed that water is the source of the terminal oxo and oxygen in the hydroxo ligand. The molecular structures of the [MnIIH31(OH)]2-and [MnIIIH31(O)]2-complexes were determined by X-ray diffraction methods and show that each complex has trigonal bipyramidal coordination geometry. The MnIII−O distance in [MnIIIH31(O)]2-is 1.771(4) Å, which is lengthened to 2.059(2) Å in [MnIIH31(OH)]2-. Structural studies also show that [H31]3-provides a hydrogen-bond cavity that surrounds the MnIII−O(H) units. Using a thermodynamic approach, which requires pKaand redox potentials, bond dissociation energies of 77(4) and 110(4) kcal/mol were calculated for [MnIIH31(O−H)]2-and [MnIIIH31(O−H)]-, respectively. The calculated value of 77 kcal/mol for the [MnIIH31(O−H)]2-complex is supported by the ability of [MnIIIH31(O)]2-complex to cleave C−H bonds with bond energies of <80 kcal/mol.