The diazido complex [Na][Ru-(N-3)(2){kappa(3)(N,N,N)-Tpms}(PPh3)] (1) (Tpms = tris(pyrazolyl)methanesulfonate) has been synthesized, and its reactivity toward dipolarophiles has been investigated. Thus, the reaction of 1 with alkynes leads to complexes with one or two triazolate ligands depending on the alkyne and the reaction conditions. Complex 1 also reacts with nitriles. Thus, the reaction with RCN (R = Me, Ph) leads to the substitution products [Ru(N-3)(NCR){kappa(3)(N,N,N)-Tpms}(PPh3)]. However, when fumaronitrile is used, a complex containing a new kappa(2)(N-1,N-3)-5-(1,2,3-triazol-4-yl)-1,2,3,4-tetrazolate ligand is obtained as the result of two consecutive cycloaddition reactions. The mechanism for this unusual reaction has been unambiguously established through the isolation of the intermediate complex resulting from a first cycloaddition between a coordinated azide and the C=C double bond.