Synthesis and Structures of CyclopropanedicarboxylateGallium Complexes.

A series of novel gallium dimethylmalonateand cyclopropane-1,1-dicarboxylate complexes have been synthesizedusing gallium halides as Lewis acids. The structure and propertiesof the resulting complexes as well as the mechanisms of reactionsinvolved have been studied. Some complexes have ionic structures andconsist of ligand-bound Ga cations and tetrahalogallate anions. Thestructures of gallium complexes were studied by multinuclear NMR spectroscopy,including that on 71Ga nuclei. Furthermore, X-ray diffractionanalysis was carried out for the six complexes. Dimethyl cyclopropanedicarboxylatewas considered as the simplest analogue of donor–acceptor cyclopropanes.It is a convenient model for studying such cyclopropanes, while thecomplexes obtained are analogues of intermediates in their reactionscatalyzed by Lewis acids. In particular, elongation of the C–CH2bond in the cyclopropane ring and activation of the latterby gallium halides have been shown experimentally. The data obtainedare a new step in studies on this very interesting and promising classof substrates. [ABSTRACT FROM AUTHOR]