Tetraethylammonium 7-dimethylsulfanyl-nido-dodecahydroundecaborate, [Et(4)N][7-Me(2)S-nido-B(11)H(12)] or C(8)H(20)N(+).C(2)H(18)B(11)S(-), is a product of the deprotonation of [7-Me(2)S-nido-B(11)H(13)] with KHBEt(3) and precipitation with tetraethylammonium chloride. The effect of removing one endo-terminal H atom is to cause a general contraction of the open-face B-B distances.