Synthesis and Structures of Cyclopropanedicarboxylate Gallium Complexes

A series of novel gallium dimethylmalonate
and cyclopropane-1,1-dicarboxylate complexes have been synthesized
using gallium halides as Lewis acids. The structure and properties
of the resulting complexes as well as the mechanisms of reactions
involved have been studied. Some complexes have ionic structures and
consist of ligand-bound Ga cations and tetrahalogallate anions. The
structures of gallium complexes were studied by multinuclear NMR spectroscopy,
including that on 71Ga nuclei. Furthermore, X-ray diffraction
analysis was carried out for the six complexes. Dimethyl cyclopropanedicarboxylate
was considered as the simplest analogue of donor–acceptor cyclopropanes.
It is a convenient model for studying such cyclopropanes, while the
complexes obtained are analogues of intermediates in their reactions
catalyzed by Lewis acids. In particular, elongation of the C–CH2 bond in the cyclopropane ring and activation of the latter
by gallium halides have been shown experimentally. The data obtained
are a new step in studies on this very interesting and promising class
of substrates.

一系列新型镓二甲基丙二酸酯和环丙烷-1,1-二羧酸酯络合物已被合成，其中采用卤化镓作为路易斯酸。研究涉及了所得络合物的结构、性质以及反应机理。部分络合物具有离子结构，由配体结合的镓阳离子和四卤化镓酸根阴离子组成。通过多核核磁共振波谱技术，包括对71Ga核的研究，对镓络合物的结构进行了研究。此外，对六种络合物进行了X射线衍射分析。二甲基环丙烷二羧酸酯被视为供体-受体环丙烷的 simplest analogue（最简单类似物）。它是一种研究此类环丙烷的便捷模型，而所得络合物则是其反应中由路易斯酸催化的中间体的类似物。特别是，环丙烷环中C-CH2键的延长以及由卤化镓激活的实验结果已得到证实。所获得的数据是研究这一非常有趣且极具潜力的底物类别的又一新进展。