The chemistry of Fe-2(mu-SH)(2)(CO)(4)(PPh3)(2) (2(HH)) is described with attention to S-S coupling reactions. Produced by the reduction of Fe-2(mu-S-2)(CO)(4)(PPh3)(2) (2), 2HH is an analogue of Fe-2(mu-SH)(2)(CO)(6) which exhibits well-behaved S-centered redox. Both 2(HH) and the related 2(MeH) exist as isomers that differ with respect to the stereochemistry of the mu-SR ligands (R = H, Me). Compounds 2(HH), 2(MeH), and 2 protonate to give rare examples of Fe-SH and Fe-S-2 hydrides. Salts of [H2](+), [H2(HH)](+), and [H2(MeH)](+) were characterized crystallographically. Complex 2(HH) reduces O-2, H2O2, (PhCO2)(2), and Ph2N2, giving 2. Related reactions involving 1(HH) gave uncharacterizable polymers. The differing behaviors of 2(HH) and 1(HH) reflect stabilization of the ferrous intermediates by the PPh3 ligands. When independently generated by the reaction of 2(HH) with 2,2,6,6-tetramethyl-1-piperidinyloxy, 2* quantitatively converts to 2 or, in the presence of C2H4, is trapped as the ethanedithiolate Fe-2(mu-S2C2H4)(CO)(4)(PPh3)(2). Evidence is presented that the Hieber-Gruber synthesis of 1 involves polysulfido intermediates [Fe-2(mu-S-n)(2)(CO)(6)](2-) (n > 1). Two relevant experiments are as follows: (i) protonation of [Fe-4(mu-S)(2)(mu-S-2)CO)(12)](2-) gives 1 and 1(HH), and (ii) oxidation of 1(HH) by sulfur gives 1.