Grafting of [W(2)(NMe(2))(6)] onto dehydroxylated silica affords the well-defined surface species [([triple bond, length as m-dash]Si-O)W(2)(NMe(2))(5)], characterized by elemental analysis, and infrared, Raman and NMR spectroscopies, and the catalytic reactivity of this supported tungsten(III) d(3)-d(3) dimer and of its alkoxide derivatives towards alkynes has been probed.