1,3-Dipolar Cycloadditions of Ruthenium(II) Azido Complexes with Alkynes and Nitriles

The diazido complex [Na]­[Ru­(N3)2{κ3(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(N3)­(NCR)­{κ3(N,N,N)-Tpms}­(PPh3)]. However,
when fumaronitrile is used, a complex containing a new κ2(N1,N3)-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.