Reactivity of Digermylenes toward Potassium Graphite: Synthesis and Characterization of Germylidenide Anions

The synthesis and characterization of the digermylenes
[LGe–GeL]
[L = L1 (3A), L2 (3B)] supported by the 2,6-diiminophenyl (L1) and 2-imino-5,6-methylenedioxylphenyl
(L2) ligands are described. Their
reactivities toward potassium graphite are also reported. The reaction
of [LGeCl] [L = L1 (2A), L2 (2B)] with KC8 in tetrahydrofuran
(THF) at room temperature afforded the digermylenes [LGe–GeL]
[L = L1 (3A), L2 (3B)], which are the first examples of diaryldigermylenes
stabilized by o-imino donor­(s). The treatment of 3A with 2 equiv of KC8 in Et2O, followed
by the addition of excess tetramethylethylenediamine (TMEDA), results
in cleavage of the GeI–GeI bond to afford
the germylidenide anion [L1GeK·TMEDA]
(4A). Similarly, the reaction of 3B with
excess KC8 in THF afforded the germylidenide anion [L2GeK] (4B). The molecular structures
of compounds 4A and 4B as determined by
single-crystal X-ray diffraction analysis show that the K atoms are
η1-coordinated with the low-valent Ge atoms. Moreover,
the negative charges at the Ge atoms in compounds 4A and 4B are stabilized by electron delocalization in the germanium
heterocycles.

本文报道了由2,6-二亚氨基苯基（L1）和2-亚氨基-5,6-亚甲二氧基苯基（L2）配体稳定的二锗烯[LGe–GeL]（L = L1（3A）、L2（3B））的合成与表征，并研究了其与钾石墨的反应活性。将[LGeCl]（L = L1（2A）、L2（2B））与KC8在四氢呋喃（THF）中于室温下反应，得到二锗烯[LGe–GeL]（L = L1（3A）、L2（3B）），这是首例由邻亚氨基供体稳定的二芳基二锗烯。在乙醚（Et2O）中用2当量的KC8处理3A，随后加入过量的四甲基乙二胺（TMEDA），可使Ge(I)–Ge(I)键发生断裂，得到锗宾负离子[L1GeK·TMEDA]（4A）。同理，将3B与过量KC8在THF中反应，得到锗宾负离子[L2GeK]（4B）。通过单晶X射线衍射分析确定的化合物4A和4B的分子结构表明，钾原子（K）与低价锗原子以η¹配位模式结合。此外，化合物4A和4B中锗原子上的负电荷通过锗杂环内的电子离域作用得到稳定。