Unexpected metal-mediated oxidation of hydroxymethyl groups to coordinated carboxylate groups by bis-cyclometalated iridium(iii) centers

Two different procedures of the ‘click’ reaction were applied to synthesize a library of 1-aryl- and 4-aryl-functionalized 1H-[1,2,3]triazoles as new ligands for phosphorescent iridium(III) complexes. For three examples, single crystal X-ray analysis was carried out and the structural properties were discussed. The reactive μ-dihydroxy-bridged iridium(III) precursor complex [(ppy)2Ir-μ-(OH)]2 (ppy = 2-phenylpyridinato) was prepared for the complexation of the herein described ligands. During these complexation studies, an unexpected metal-assisted oxidation pathway was observed for the hydroxymethyl-substituted 1-aryl-1H-[1,2,3]triazoles 2d–f leading selectively to a [carboxylate-N3,O]-coordination of the ligands to the iridium(III) centers.