iClick Reactions of Square-Planar Palladium(II) and Platinum(II) Azido Complexes with Electron-Poor Alkynes: Metal-Dependent Preference for N1 vs N2 Triazolate Coordination and Kinetic Studies with H and F NMR Spectroscopy.

Two square-planar palladium(II) and platinum(II) azido complexes [M(N)(L)] with L = phenyl-2-[1-(2-pyridinyl)ethylidene]hydrazine carbothioamide reacted with four different electron-poor alkynes R-C≡C-R' with R = R' = COOCH, COOEt, COOCHCHOCH or R = CF, R' = COOEt in a [3 + 2] cycloaddition "iClick" reaction. The resulting triazolate complexes [M(triazolate)(L)] were isolated by simple precipitation and/or washing in high purity and good yield. Six out of the eight new compounds feature the triazolate ligand coordinated to the metal center via the N2 nitrogen atom, but fortuitous solubility properties allowed isolation of the N1 isomer in two cases from acetone.