Triazolato Pd(II) and Pt(II) complexes of 2,6-bis(1-ethylbenzimidazol-2′-yl)pyridine formed via catalyst-free [3 + 2] click reactions.

[Display omitted] • DMSO and metal ion have roles in regulating the triazolate isomers ratio of the iClick reaction. • A non-equivalent mixture of N1 and N2 triazolate isomers in the case of symmetrical alkyne. • The nature of the alkyne affects the ratio of the formed triazolate Pd(II) isomers. At the ambient temperature and under catalyst-free conditions, reactions between [MN 3 (LET)]PF 6 (M = Pd(II) and Pt(II); LET = 2,6-bis(1-ethylbenzimidazol-2′-yl)pyridine) and substituted alkynes (dimethyl acetylene-dicarboxylate and 4,4,4-trifluoro-2‑butynoic acid ethyl ester) afforded the corresponding triazolate complexes. These reactions produced a mixture of triazolate bound isomers. The N1 triazolate isomer of the Pt(II) complexes, which first appeared in the [3 + 2] coupling, eventually isomerized to the N2-analogue during the incubation in DMSO. The reactions of [MN 3 (LET)]PF 6 with asymmetric alkyne, 4,4,4-trifluoro-2‑butynoic acid ethyl ester, produced a mixture of the three anticipated triazolate isomers, according to 19F NMR spectroscopy. The stability of the triazolate complexes was investigated, along with the cycloaddition reaction's mechanism and the nature of the intermediates, using NMR spectroscopy. [ABSTRACT FROM AUTHOR]