[4Fe-4S] clusters modeled after those in organisms having three cysteine thiolates and one carboxylate were synthesized by using the tridentate thiolato chelate. X-ray structural analysis reveals that the carboxylates coordinate to the unique irons in an eta(1) manner rather than eta(2). Redox potentials show a positive shift from that of the cluster having ethanethiolate and the tridentate thiolato chelate. These properties conform to the arrangement of the [4Fe-4S] clusters in the electron transfer systems included in Rc dark operative protochlorophyllide oxidoreductase (DPOR) and formaldehyde oxidoreductase (FOR) with Pf ferredoxin.