On the border between localization and delocalization: tris(iminoxolene)titanium( iv )
On the border between localization and delocalization: tris(iminoxolene)titanium( iv )
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定位与离域的边界：tris(iminoxolene)titanium( iv )
DOI：
10.1039/c8dt04528c
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发表时间：
2019
影响因子：
4
通讯作者：
Brown, Seth N.
中科院分区：
文献类型：
--
作者：
Marshall-Roth, Travis;Yao, Kun;Parkhill, John A.;Brown, Seth N.
三（氨基苯酚）配体三（4-甲基-2-（3′，5 ′-二叔丁基-2 ′-羟基苯胺基）苯基）胺MeClampH 6与Ti（OiPr）4反应，在暴露于空气中后得到深紫色、中性、抗磁性配合物（MeClamp）Ti。该化合物是六配位的，具有未配位的中心氮（Ti-N = 2.8274（12）N），并且含有钛（IV）和双氧化配体，形式上是双（亚氨基半醌）-单（酰胺基苯酚）。该化合物在固态下是不对称的，尽管三个配体在溶液中的NMR时间尺度上是等价的。从头计算结果表明，基态是一个多组态单重态，与一个低洼的多组态三重态。变温NMR测量结果与1200 ± 70 cm−1的单重态-三重态间隙一致，与计算结果吻合良好。三重对称性的扭曲使得一个低位的、部分占据的配体中心π非键轨道与大部分占据的金属-配体π成键轨道混合。这种畸变的能量可达性与金属-配体π键相互作用的强度成反比。
The tris(aminophenol) ligand tris(4-methyl-2-(3′,5′-di-tert-butyl-2′-hydroxyphenylamino)phenyl)amine, MeClampH6, reacts with Ti(OiPr)4 to give, after exposure to air, the dark purple, neutral, diamagnetic complex (MeClamp)Ti. The compound is six-coordinate, with an uncoordinated central nitrogen (Ti–N = 2.8274(12) Å), and contains titanium(IV) and a doubly oxidized ligand, formally a bis(iminosemiquinone)-mono(amidophenoxide). The compound is unsymmetrical in the solid state, though the three ligands are equivalent on the NMR timescale in solution. Ab initio calculations indicate that the ground state is a multiconfigurational singlet, with a low-lying multiconfigurational triplet state. Variable-temperature NMR measurements are consistent with a singlet–triplet gap of 1200 ± 70 cm−1, in good agreement with calculations. The distortion from threefold symmetry allows a low-lying, partially populated ligand-centered π nonbonding orbital to mix with largely occupied metal–ligand π bonding orbitals. The energetic accessibility of this distortion is inversely related to the strength of the metal–ligand π bonding interaction.