ELECTRON-TRANSFER SERIES INVOLVING SULFUR-RICH, POLYNUCLEAR IRON DITHIOLENE COMPLEXES

Synthetic, polarographic, and other physicochemical studies of several polynuclear dithiolene complexes have demonstrated the ability of these systems to undergo electron-transfer reactions without a breakdown of the polynuclear unit. Treatment of (CF3)2C2S2Fe2(CO)6 or Ph2C2S2Fe2(CO)6 with sulfur in boiling xylene produces the terminal oxidized member (z = 0) of a five-membered (z = 0, -1, -2, -3, and -4) electron-transfer related series based on the [Fe4S4(S2C2R2)4]z unit (R = Ph, CF3). In addition the reduced members with z = – 1 (R = CF3, Ph) and z = – 2 (R = CF33) have been isolated. The conductivity, magnetic properties, and electrochemistry of these species are consistent with formulation of the fundamental unit involved in the electron-transfer reactions as a quadrimer, although it has been impossible to obtain direct molecular weight data for the neutral species. The reactions of the quadrinuclear unit with a variety of Lewis bases is described. Small amounts of [Fe3S2(S2C2- {CF3}2)4] have also been isolated from the reaction of (CF3)2C2S2Fe2(CO)6 and sulfur. This trinuclear complex undergoes polarographic reduction to form [Fe3S2(S2C2{CF3)2)3]z (z = -1 and -2); the monoanion has been generated but not isolated. Similarities between these synthetic, sulfur-rich complexes and the biologically important ferredoxins are pointed out. The trimers [(CO)3Co3(S2C2 {CF3} 2)3] and [(NO)3Fe3(S2C2 {CF3} 2)3], which have been previously characterized, are capable of being reduced polarographically to a monoanion and to a monoanion and a dianion, respectively. © 1969, American Chemical Society. All rights reserved.