The reactions of selected aryldiazonium tetrafluoroborates with Fe(CO)3(PR3)2, [Fe(mnt)2]−, [Fe(cystH)2]2+, and [Fe(CO)2(cyst)2] (mnt = S2C2(CN)2, cyst = SCH2CH(NH2)CO2H ) result in abstraction of the ligand to yield arenediazophosphonium ions, S-(arenediazo)cysteine or the dinitrogen extrusion product ArS(CN)C=C(CN)SAr. Arylazo complexes of iron were not obtained. The products have been characterized and compounds related to S-(arenediazo)cysteine, namely S-(arenediazo)triphenylmethyl mercaptan and S-(arenediazo)sulfones, have been synthesized for a detailed comparison of their Raman spectra. Assignments of ν(N=N) are made on the basis of 15N- and 2H-substitution experiments. The possible involvement of nucleophilic sulfur as a site for the activation and or reduction of complexed dinitrogen in biological nitrogen fixation is proposed.