The crystal structure of the title compound, thylideneamino-3-methylpt
eridin-4(3H)-onato(2-)-S, S']cobalt(III) monohydrate, [Co(C5H5)(C12H12
N6OS2)].H2O, shows the sulfur/cobalt-containing ring, the pteridine ri
ng system and the pteridine-2-amino protecting group to be coplanar.