Reaction of Fe(CO)(2)(NO)(2) and [(ON)Fe(S,S-C6H3R)(2)](-) (R = H (1), CH3 (1-Me))/[(ON)Fe(SO2,S-C6H4)(S,S-C6H4)](-) (4) in THF afforded the diiron thiolate/sulfinate nitrosyl complexes [(ON)Fe(S,S-C6H3R)(2)Fe(NO)(2)](-) (R = H (2), CH3 (2-Me)) and [(ON)Fe(S,SO2-C6H4)(S,S-C6H4)Fe(NO)(2)](-) (3), respectively. The average N-O bond lengths ([Fe(NO)(2)] unit) of 1.167(3) and 1.162(4) angstrom in complexes 2 and 3 are consistent with the average N-O bond length of 1.165 angstrom observed in the other structurally characterized dinitrosyl iron complexes with an {Fe(NO)(2)}(9) core. The lower v((NO)-N-15) value (1682 cm(-1) (KBr)) of the [((NO)-N-15)FeS4] fragment of [((NO)-N-15)Fe(S,S-C6H3CH3)(2)Fe(NO)(2)](-) (2-Me-N-15), compared to that of [((NO)-N-15)Fe(S,S-C6H3CH3)(2)](-) (1-Me-N-15) (1727 cm(-1) (KBr)), implicates the electron transfer from {Fe(NO)(2)}(10) Fe(CO)(2)(NO)(2) to complex 1-Me/1 may occur in the process of formation of complex 2-Me/2. Then, the electronic structures of the [(NO)FeS4] and [S2Fe(NO)(2)] cores of complexes 2, 2-Me, and 3 were best assigned according to the Feltham-Enemark notation as the {Fe(NO)}(7)-{Fe(NO)(2)}(9) coupling (antiferromagnetic interaction with a J value of -182 cm(-1) for complex 2) to account for the absence of paramagnetism (SQUID) and the EPR signal. On the basis of Fe-N(O) and N-O bond distances, the dinitrosyliron {L2Fe(NO)(2)} derivatives having an Fe-N(O) distance of similar to 1.670 angstrom and a N-O distance of -1.165 angstrom are best assigned as {Fe(NO)(2)}(9) electronic structures, whereas the Fe-N(O) distance of -1.650 angstrom and N-O distance of -1.190 angstrom probably imply an {Fe(NO)(2)}(10) electronic structure.