A general strategy for synthesizing Fe(III) complexes of ligands containing carboxamido-N and thiolato-S donors has been described. Reaction of the doubly deprotonated ligand PyPepS(2-) (where PyPepSH(2) = N-2-mercaptophenyl2'-pyridinecarboxamide) with Fe(III) salts in DMF had previously afforded the Fe(III) complex (Et4N)[Fe(PyPePS)(2)] without any problem(s) associated with autoredox reactions of the thiolate functionality. In the present work, similar reactions with the doubly deprotonated ligand PiPepS(2-) (where PiPepSH(2) = 2-mercapto-N-pyridin-2-yl-methylbenzamide) with Fe(III) salts, however, fail to afford any Fe(III) complex because of autoredox reactions. The break in the conjugation in the PiPepSH(2) ligand frame is the key reason for this difference in behavior between these two very similar ligands. This is demonstrated by the fact that the same reaction with AqPepS(2-) (where AqPepSH(2) = 2-mercapto-N-quinolin-8-yl-benzamide), another ligand with extended conjugation, affords the Fe(III) complex (Et4N)[Fe(AqPePS)(2)] (1) without any synthetic complication. It is therefore evident that ligands in which the carboxamide and thiolate functionalities are kept in conjugation could be used to isolate Fe(III) complexes with carboxamido-N and thiolato-S coordination. This finding will be very helpful in future research work in the area of modeling the active site of Fe-containing nitrile hydratase.