Preparation, Characterization, and Reactivity of Azido Complex Containing a Tp(tBuNC)(PPh3)Ru Fragment and Ruthenium-Catalyzed Cycloaddition of Organic Azides with Alkynes in Organic and Aqueous Media

Treatment of the TpRu complex (PPh3)[Ru]-Cl (1, [Ru] = Tp(tBuNC)Ru) with an excess of sodium azide affords the yellow ruthenium azido complex (PPh3)[Ru]-N3 (2). The triazolato complexes (PPh3)[Ru]-N3C2(R)2 (3a, R = Me; 3b, R = Et) are synthesized via [3+2] cycloadditions of 2 with RO2CC≡CCO2R. Complete characterization of these triazolato complexes elucidates the structures and establishes the N(2)-bonding type of the addition products. Alkylation of 3a with organic bromides causes cleavage of the Ru–N bond and affords 1,4,5-trisubstituted triazoles. Moreover, addition of CS2 to 2 produces thermally unstable thiothiatriazolate (PPh3)[Ru]-N3CS(S) (5), which converts to the isothiocyanate complexes (PPh3)[Ru]-NCS (6) and (tBuNC)[Ru]-NCS (7). Other reagents also react with 2, but the products do not result from [3+2] cycloadditions. Terminal alkynes undergo ligand substitution reactions rather than a [3+2] cycloaddition with 2 in the presence of H2O to produce the carbonyl complexes (CO)[Ru]-CH2R (8a, R = Ph...