Unsaturated five-membered selenium–germanium containing heterocycles based on the reactions of selenium di- and tetrahalides with diorganyl diethynyl germanes

Regio- and stereoselective reactions of selenium dihalides with diorganyl diethynyl germanes in CHCl3 afford in yields from preparative to quantitative the first representatives of a new class of selenium–germanium containing heterocycles - 3,6-dihalogen-4,4-diorganyl-1,4-selenagermafulvenes. The reaction of selenium tetrachloride under the same conditions leads to the first representatives of a new class of selenium–germanium containing cyclopentene heterocycles - 2-dichloromethyl-2,4-dichloro-3,3-diorganyl-1-selena-3-germacyclopentenes-4 as well as to the unknown 3,6,6-trichloro-4,4-dialkyl-1,4-selenagermafulvenes formed as a result of a spontaneous dehydrochlorination of the cyclopentene heterocycles. In a case of SeBr4 the process of dehydrobromination is dominating. The structures of the heterocycles were proved by multinuclear (1H, 13C, 77Se) spectroscopy and mass-spectrometry. In the 1H NMR spectra of Z-isomers of 1,4-selenagermafulvenes a long-range spin–spin interaction between exo- and endocyclic olefinic protons through five bonds is revealed lacking in the E-isomers.