SYNTHESIS AND PROPERTIES OF OCTAETHYLPORPHINATO(ARENETHIOLATO)IRON(III) COMPLEXES WITH INTRAMOLECULAR NH-S HYDROGEN-BOND - CHEMICAL FUNCTION OF THE HYDROGEN-BOND

Iron(III) porphinate complexes of arenethiolate having single or doubl e NH ... S hydrogen bonds at the axial position, [Fe-III(OEP){S-2,6-(R CONH)(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 the se complexes is confirmed by their crystal structures in the solid sta te, the IR shift of the amide NH band and the direct through-bond cont act-shift of the amide H-2 NMR signal in benzene. The NH ... S hydroge n bond elongates the Fe-S bond distance, stabilizes the Fe(III) state, protects the complexes from decomposition by air and moisture, and sh ifts the redox to more positive potentials. These functions by the hyd rogen bond are more significant than the effect of steric hindrance.