The 5-oxaporphyrin macrocycle is a modified porphyrin that has an oxygen atom in place of one meso-methine group. These 5-oxaporphyrins are readily produced from heme degradation by both chemical and biological processes. Treatment of metal complexes of 5-oxaporphyrins with nucleophiles can lead to reactions either at the metal or on the ligand. Here we report that the diamagnetic zinc(II) verdoheme analogue [Zn-II(OEOP)](O2CCH3) {OEOP is the monoanion of octaethyl-5-oxaporphyrin} reacts with dimethylamide and with methanethiolate to form ring-opened products Zn-II(OEBNMe2) and Zn-II(OEBSMe). The ring-opened products have been subjected to crystallographic study. In both complexes the helical tetrapyrrole ligand imposes a structure in which the zinc ion is trapped between planar and tetrahedral coordination. The structures of these two complexes are compared with that of Zn-II(OEBOMe), which has a similar helical shape.