Dioxygen-induced decarboxylation and hydroxylation of [Ni II (glycyl-glycyl- L -histidine)] occurs via Ni III : X-ray crystal structure of [Ni II (glycyl-glycyl-α-hydroxy- D , L -histamine)]·3H 2 O

Electrochemical and EPR studies show that the dioxygen-induced decarboxylation and hydroxylation of [NiII(GGH-H–2)]–, where GGH is glycyl-glycyl-L-histidine (HL), in aqueous solution occurs via a NiIII intermediate; the product [NiII(Gly-Gly-α-hydroxy-D,L-histamine-H2)]·3H2O is shown by X-ray crystallography to contain square-planar NiII coordinated to the terminal amino group [Ni–N, 1.932(3)Å], two deprotonated amide N's [1.884(3) and 1.831(3)Å] and imidazole δN [1.908(3)Å].