Cyclotrigermenes synthesis

The first landmark was the successful synthesis and structural characterization of the cyclotrigermylium cations 2 and 19 by Sekiguchi and co-workers. This was achieved by reaction of trityl cation with the cyclotrigermenes 20 in the presence of weakly coordinating borate anions (Scheme 8). The trityl cation acts here as a one-electron oxidizing reagent and the resulting radical cation of 20 decomposes to the... 

The synthesis of the first cyclotrisilenes has required a longer time than for the cyclotrigermenes due to the lack of suitable stable silylenes, in contrast, for example, to the well-known dichlorogermylene-dioxane complex25. Therefore, the preliminary preparation of the silylene precursors, which can generate silylenes in situ, was necessary for the successful synthesis of cyclotrisilenes. Until now, only two examples of cyclotrisilenes have been reported in the literature, of which only one was structurally characterized. 

Summary The synthesis, structural characteristics, and physical properties of unsaturated three-membered rings containing heavier group 14 elements with endocyclic metal-metal double bonds, including cyclotrigermenes, cyclotrisilenes, cyclotristannene, and disilagermirenes, is summarized. 

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