LAUSR

Abstract Reaction between the platinum(IV) azido complex trans,trans,trans‐[Pt(py)2(N3)2(OH)2] (1) and 1,4‐diphenyl‐2‐butyne‐1,4‐dione 2 in MeCN produces the intermediate peroxide‐bridged dimeric platinum(IV) azido triazolato species (5), which has been characterised by X‐ray crystallography. However, if the reaction between 1 and 2 is conducted in MeOH it results in decomposition. Over time in MeCN, dimer (5) converts into mononuclear complexes trans,trans,trans‐[Pt(py)2(N3)(triazole)(OH)2] (3 a/3 b), which are in dynamic exchange. If resuspended in protic solvents (MeOH,H2O), 3 a/3 b undergo a slow (22 d) irreversible rearrangement to a cyclised platinum(IV) species 4 which contains a formally N,O‐chelated ligand. Conversion of 3 a/3 b to 4 in d 4‐MeOH can be accelerated (384x) by irradiation with visible light, although continued irradiation also produces N3 . and OH. radicals, and the [4‐N3]+ species can be readily detected by ESI‐MS. Solvent choice significantly effects both the cycloaddition reaction between 1 and 2, and the stability of the resultant complexes.