Reactivity of azido terpyridine Pd(ii) and Pt(ii) complexes towards 4,4,4-trifluoro-2-butynoic acid: structural insight into the triazolato coordination mode

The mono- and binuclear azido terpyridine square-planar complexes of ionic formulas, [Pd₂(N₃)₂L]²⁺ and [Pt(N₃)L]⁺ (L = 1,4-bis(2,2′:6′,2′′-terpyridin-4′yl)benzene), underwent the catalyst-free [3 + 2] cycloaddition coupling with 4,4,4-trifluoro-2-butynoic acid at ambient temperature affording the corresponding triazolate complexes. A mixture of triazolate isomers was generated by these inorganic click reactions. An increase in the solubility of the compounds was achieved by replacing the azido ligand with a triazolato ligand. By calculating the vibrational modes and comparing the total electronic and zero-point energy values, the local minimum structures of the complexes and the nature of the predominant triazolate isomer were verified. The theoretical work was complemented with natural bond analysis to get an insight into the natural charge and electronic arrangement of the metal ion, the hybridization of M-L bonds and strength of M-N bonds.