Synthesis of the first 2H-selenete complexes, decomplexation and dimerization to dihydro-1,2-diselenine

Pentacarbonyltungsten-coordinated selenobenzaldehydes, (CO)5W[SeC(C6H4R-p)H](R = QMe, H, CF3), react with ButS–CC–SBut by addition of the CC to the SeC bond to give 2H-selenete complexes; treatment of the selenete complex (RH) with NEt4Br affords the uncoordinated 2H-selenete and a 3,4-dihydro-1,2-diselenine.