Division of Chemistry and Biological Chemistry, Nanyang Technological University, 21 Nanyang Link, Singapore 637371 (Singapore).
Angew Chem Int Ed Engl. 2014 Aug 4;53(32):8455-8. doi: 10.1002/anie.201404357. Epub 2014 Jun 12.
The two-electron reduction of a Group 14-element(I) complex [RË⋅] (E=Ge, R=supporting ligand) to form a novel low-valent dianion radical with the composition [RË:]˙(2-) is reported. The reaction of [LGeCl] (1, L=2,6-(CH=NAr)2C6H3, Ar=2,6-iPr2C6H3) with excess calcium in THF at room temperature afforded the germylidenediide dianion radical complex [LGe]˙(2-)⋅Ca(THF)3(2+) (2). The reaction proceeds through the formation of the germanium(I) radical [LGe⋅], which then undergoes a two-electron reduction with calcium to form 2. EPR spectroscopy, X-ray crystallography, and theoretical studies show that the germanium center in 2 has two lone pairs of electrons and the radical is delocalized over the germanium-containing heterocycle. In contrast, the magnesium derivative of the germylidendiide dianion radical is unstable and undergoes dimerization with concurrent dearomatization to form the germylidenide anion complex [C6H3-2-{C(H)=NAr}Ge-Mg-6-{C(H)-NAr}]2 (3).
报道了一种新型低价二阴离子自由基[RË:]˙(2-)的形成，它是通过 14 族元素（I）配合物[RË⋅]（E=Ge，R=配体）的二电子还原得到的。[LGeCl]（1，L=2,6-（CH=NAr）2C6H3，Ar=2,6-iPr2C6H3）与过量钙在 THF 中于室温下反应，得到了亚氨基二芳基二阴离子自由基配合物[LGe]˙(2-)⋅Ca(THF)3(2+)（2）。该反应通过形成锗（I）自由基[LGe⋅]进行，然后该自由基与钙发生两电子还原反应，生成 2。电子顺磁共振光谱、X 射线晶体学和理论研究表明，2 中的锗中心具有两对孤对电子，自由基在含锗杂环上离域。相比之下，亚氨基二芳基二阴离子自由基的镁衍生物不稳定，会发生二聚化反应，同时发生去芳构化，形成亚氨基二阴离子配合物[C6H3-2-{C(H)=NAr}Ge-Mg-6-{C(H)-NAr}]2（3）。
