Amido-Triazole Complexes, “Normal” Triazole-Based Imines and Metallo-Mesoionic Imines

Mesoionic compounds are hugely popular in fields such as organic chemistry, organometallic chemistry and homogeneous catalysis. A new sub-class are the mesoionic imines (MIIs). We present here 5-amino-4-pyridyl-1,2,3-triazole as a new and versatile synthon for generating first examples of metallo-MIIs. In this approach, we make use of metallation at the N-pyridyl/N3-triazole chelating pocket (instead of quarternisation of N3-triazole) and subsequent deprotonation to generate highly versatile and tunable metallo-MIIs. These unprecedented metallo-MIIs contain a highly nucleophilic N-donor site, and a tunable electrophilic metal site. Apart from displaying strong and directed H-bonding interactions like their “classical” MII analogues, the metallo-MIIs engage in aromatic C−F activation as well as meta−C−H activation reactions. Facile synthesis of homo and heterodincuelar complexes which contain a mixed coordinative saturation/unsaturation with these metallo-MIIs is presented. Apart from the metallo-MIIs we have also used 5-amino-4-pyridyl-1,2,3-triazole as a precursor to generate the first examples of amido-1,2,3-triazole complexes and the first example of a “normal” (and not mesoionic) 1,2,3-triazole based imine. Our results establish metallo-MIIs as a versatile new class of mesoionic compounds that combine the modularity of click reactions, with the functionality of metal fragments to generate electronically ambivalent compounds with a huge potential in synthetic chemistry, catalysis and beyond.