The base-catalyzed hydrostannation of di-ethynyl sulfide with dibutylstannane affords 4,4-dibutyl-1,4-thiastannin, which reacts with methylboron dibromide to give 4-methyl-1,4-thiaborin. The thiaborin has been converted to tricarbonyl(eta(6)-4-methyl-1,4-thiaborin)-molybdenum, which has been characterized by single-crystal X-ray diffraction.