DIOXYGEN-INDUCED DECARBOXYLATION AND HYDROXYLATION OF [NI-II(GLYCYL-GLYCYL-L-HISTIDINE)] OCCURS VIA NI-III - X-RAY CRYSTAL-STRUCTURE OF LYCYL-ALPHA-HYDROXY-D,L-HISTAMINE)]CENTER-DOT-3H2O

Electrochemical and EPR studies show that the dioxygen-induced decarbo xylation and hydroxylation of [Ni-II(GGH-H--2)](-), where GGH is glycy l-glycyl-L-histidine (HL), in aqueous solution occurs via a Ni-III int ermediate; the product I(Gly-Gly-alpha-hydroxy-D,L-histamine-H-2)].3H( 2)O is shown by X-ray crystallography to contain square-planar Ni-II c oordinated to the terminal amino group [Ni-N, 1:932(3) Angstrom], two deprotonated amide N's [1.884(3) and 1.831(3) Angstrom] and imidazole delta N [1.908(3) Angstrom].