Iron(III) porphinate complexes of arenethiolate having single or double NH ... S hydrogen bonds at the axial position, [Fe-III(OEP){S-2,6-(RCONH)(2)C6H3}] (R = CF3 (1), CH3 (2)) or [Fe-III(OEP)(S-2-RCONHC6H4)] (R = CF3 (3), CH3 (4), t-Bu (5)), were synthesized as models of P-450 and chloroperoxidase. The presence of an NH ... S hydrogen bond in these complexes is confirmed by their crystal structures in the solid state, the IR shift of the amide NH band and the direct through-bond contact-shift of the amide H-2 NMR signal in benzene. The NH ... S hydrogen bond elongates the Fe-S bond distance, stabilizes the Fe(III) state, protects the complexes from decomposition by air and moisture, and shifts the redox to more positive potentials. These functions by the hydrogen bond are more significant than the effect of steric hindrance.