Carboxylate-bridged nonheme diiron(II) complexes, bearing free functional groups in general, and free thiol groups in particular, were sought. While the addition of sodium gamma-hydroxybutyrate into a mixture of Fe(BF4)(2)center dot 6H(2)O, HN-Et-HPTB, and Et3N afforded the complex [Fe-2(N-Et-HPTB)(mu-O2C-(CH2)(3)-OH)](BF4)(2) (2) (where N -Et- IIPTB is the anion of N,N,N ',N '-tetrakis(2-(1-ethylbenzimidazoly1))-2-hydroxy-1,3-diaminopropane), a similar, straightforward process could not be used for the synthesis of diiron(II) complexes with free thiol groups. In order to circumvent this problem, a new class of thiolate bridged diiron(II) complexes, [Fe-2(N-Et-HPTB)(mu-SR1)](BF4)(2) (R-1 = Me (1a), Et (1b), Bu-t (1c), Ph (1d)) was synthesized. Selective proton exchange reactions of,one representative compound, lb, with reagents of the type HS-R-2-COOH yielded the target compounds, [Fe-2(N-Et-HPTB)(mu-O2C-R-2-SH)]BF4)(2) (R-2 = C6H4 (3a), CH2CH2 (3b), CH2(CH2)(5)CH2 (3c)). Redox properties of the complexes 3a-3c were studied in comparison with the complex, [Fe-2(N-Et-HPTB)(mu-O2CMe)](BF4)(2) (5). Reaction of (Cp2Fe)(BF4) with lb yielded [Fe-2(II)(N-Et-HPTB)(DMF)(3)](BF4)(3)center dot DMF (4) (when crystallized from DMF/diethyl ether), which might indicate the formation of a transient ethanethiolate bridged {(FeFeIII)-Fe-II} species, followed by a rapid internal redox reaction to generate diethyldisulfide and the solvent coordinated diiron(II) complex, 4. This possibility was supported by a comparative cyclic voltarnmetric study of 1a-1c and 4. Prospects of the complexes of the type 3a -3c as potential building blocks for the synthesis of nonheme diiron(II) complexes covalently attached with other redox active metals has been substantiated by the synthesis of the complexes, [Fe-2(N-EtHPTB)(mu-O2C-R-2- S)Cu(Me(3)TACN)](BF4)(2) (R = p-C6H4 (7a), CH2CH2 (7b)). All the compounds were characterized by a combination of single ,crystal X-ray structure determinations and/or elemental analysis.