anti- and gauche-W2Et2(NMe2)4 react with 1,3-diaryltriazenes, ArNNNHAr, where Ar = phenyl (Ph) and p-tolyl in hydrocarbon solvents to give W2Et2(NMe2)2(ArN3Ar)2 compounds in three isomeric forms, A, B, and C. Isomers A and B are formed kinetically from gauche- and anti-1,2-W2Et2(NMe2)4, respectively. With time, isomer A is converted to isomer B, which reacts further to give an equilibrium mixture of B and C. The isomer B, where Ar = Ph, and isomer C, where Ar = p-tol, have been characterized by single-crystal X-ray studies. In both isomers each tungsten atom is coordinated to three nitrogen atoms and one carbon atom in a roughly square-planar manner and united to the other tungsten atom by a W=W bond. For isomer B (Ar = Ph) the W=W bond is unbridged, W-W = 2.304 (1) Å, while for C (Ar = p-tol) there is a pair of cis-bridging triazenido ligands, W-W = 2.267 (1) Å. On the basis of the observed solid-state structures and NMR studies of the reaction between W2Et2(NMe2)4 and 1,3-diaryltriazenes, a reaction sequence accounting for the kinetic sequence of events is proposed. Crystal data follow for the compounds W2Et2(NMe2)2(ArN3Ar)2. For Ar = Ph, at –159 °C: a = 19.504 (5) Å, b = 8.650 (1) Å, c = 19.385 (5) Å, Z = 4, dcalcd = 1.841 g cm-3, space group Pbcn, For Ar = p-tol, at –161 °C: a =12.728 (5) Å, b = 13.990 (7) Å, c =— 21.274 (10) Å, ß = 98.17 (2)°, dcalcd =1.705 g cm-3, space.