Three compounds containing the [Mo2O2(mu-E)(2)](2+) (E = O, S) cores ligated by [Fe2S2(CO)(6)](2-) have been prepared and structurally characterized : (Ph(4)As)(2){Mo2O2(mu-S)(2)[Fe2S2(CO)(6)]2} ((Ph(4)As)(2)I, triclinic, space group (No. 2), a = 14.266(12) Angstrom, b = 14.746(12) Angstrom, c = 16.643(15) Angstrom, alpha = 101.9(2)degrees, beta = 98.2(2)degrees, gamma = 99.1(2)degrees, Z = 2, R = R(w) = 0.058, 6196 reflections with I > 2.5 sigma(I)), (Ph(4)P)(2){Mo2O2(mu-O)(mu-S)[Fe2S2(CO)(6)](2)} ((Ph(4)P)(2) II, monoclinic, space group P2(1)/c (No. 14), a = 15.33(1) Angstrom, b = 15.10(1) Angstrom, c = 18.00(2) Angstrom, alpha = gamma = 90 degrees, beta = 100.6(5)degrees, Z = 2, R = 0.067, R(w) = 0.047, 3183 reflections with I > 3 sigma(I)), and (Ph(4)P)(2){Mo4O8(mu-OCH3)(2)[Fe2S2(CO)(6)](2)}. THF ((Ph(4)P)(2)III . THF, triclinic, space group (No. 2), a = 16.599(4) Angstrom, b = 16.963(4) Angstrom, c = 15.465(3) Angstrom, alpha = 113.90(2)degrees, beta = 102.06(2)degrees, gamma = 109.29(2)degrees, Z = 2, R = 0.044, R(w) = 0.066, 5043 reflections with I > 3 sigma(I)). Clusters I and II contain the cis-bis(oxomolybdenum) core bridged by either two sulfide ligands or one sulfide and one oxo ligand, respectively. Cluster III contains two cis-[Mo2O4](2+) cores connected by two methoxy bridges to give the [Mo4O8(mu-OCH3)(2)](2+) structural fragment. Clusters I and III undergo reactions with sulfide reagents to yield products that are indistinguishable from one another by IR spectroscopy, and the nature of the possible common product is discussed.