Versatile, Selective, and Switchable Coordination Modes of Pincer Click Ligands

Ligands possessing multiple complexation modes are an interesting class of compounds. Here we report that our recently established pincer click ligands (PCLs), prepared by copper-catalyzed cycloaddition of azides to alkynes, exhibit unique versatility in coordination ability. Nitrogens of the triazole-based backbone can actively participate in metal ligation rather than being a spectator backbone. Under selection of the reaction conditions these ligands can selectively acquire either bi- or tridentate coordination upon reaction with a metal precursor. Both palladium and platinum complexes with different coordination modes were prepared and fully characterized including X-ray analysis. Moreover, the “rollover switch” of kinetically preferred bidentate complexes to the thermodynamically controlled tridentate species is demonstrated.