Institute of Chemistry, Carl von Ossietzky University of Oldenburg , Carl von Ossietzky-Str. 9-11, D-26129 Oldenburg, FRG, European Union.
J Am Chem Soc. 2018 Feb 28;140(8):3052-3060. doi: 10.1021/jacs.7b13536. Epub 2018 Feb 12.
2,5-Disilylsubstituted germole dianions 1 react with hafnocene dichloride to give hafnocene-based bicyclo[2.1.1]hexene germylenes 3. Their formation proceeds via hafnocene-germylene complexes 2 that were identified by NMR and UV spectroscopy. Germylenes 3 are stabilized by homoconjugation between the empty 4p(Ge) orbital and the π-bond of the innercyclic C═C double bond. This interaction can be understood as σ, π-coordination of the butadiene part to the dicoordinated germanium atom that leaves the 16e hafnocene moiety electronically unsaturated. We demonstrate that this new class of germylenes might serve as ligand to a variety of low-valent transition-metal complexes. The structure of the germylene ligand in complexes with Fe(0), Ni(0), and Au(I) and in reaction products with N-heterocyclic carbenes showed an intriguing structural flexibility that allows to accommodate different electronic situations at the ligating germanium atom. The origin of this structural adaptability is the interplay between the topological flexible unsaturated germanium ring and the hafnocene group.
2,5-二取代亚硅基二负离子 1 与二氯二茂锆反应生成基于二茂锆的双环[2.1.1]己烯锗叶立德 3。它们的形成通过 NMR 和 UV 光谱鉴定的锗叶立德配合物 2 进行。3 是通过空的 4p(Ge)轨道和内环 C═C 双键的π键之间的同共轭稳定的。这种相互作用可以理解为部分丁二烯与 d 配位的锗原子的σ,π-配位，留下 16e 的二茂锆部分电子不饱和。我们证明，这类新型的锗叶立德可能作为配体用于各种低价过渡金属配合物。与 Fe(0)、Ni(0)和 Au(I)的配合物以及与 N-杂环卡宾的反应产物中的锗叶立德配体的结构显示出一种有趣的结构灵活性，允许在配位的锗原子上适应不同的电子情况。这种结构适应性的起源是拓扑灵活的不饱和锗环和二茂锆基团之间的相互作用。
