SYNTHESES AND STRUCTURES OF MIXED-LIGAND TETRAIRON-SULFUR CLUSTERS - CP-ASTERISK(2)(PH(R)C2S2)(2)FE4S4 (CP-ASTERISK=CP, R=PH, ET CP-ASTERISK=C(5)ME(5), R=PH, ME, PT) AND (C(5)ME(5))(3)(PH(2)C(2)S(2))FE4S5

Mixed-ligand tetrairon - sulfur clusters (C(5)Me(5))(2)(Ph(2)C(2)S(2))(2)Fe4S4 (1) and (C(5)Me(5))(3)(Ph(2)C(2)S(2))Fe4S5 (2) were synthesized by refluxing a mixture of (C(5)Me(5))(2)Fe-2(CO)(4), elemental sulfur, and PhC=CPh in mesitylene. Similar treatments using PhC=CMe and PhC=CEt instead of PhC=CPh afforded clusters corresponding to 1, namely (C(5)Me(5))(2)(Ph(Me)C2S2)(2)Fe4S4 (3) and (C(5)Me(5))(2)(Ph(Et)C2S2)(2)Fe4S4 (4). The reactions of Cp(2)Fe(2)(CO)(4) with elemental sulfur and alkynes (PhC=CPh and PhC=CEt) afforded mixed-ligand clusters Cp(2)(Ph(2)C(2)S(2))(2)Fe4S4 (5) and Cp(2)(Ph(Et)C2S2)(2)Fe4S4 (6), respectively, as well as the cubane cluster Cp(4)Fe(4)S(4). The structures of clusters 1 and 2 were determined by X-ray structural analyses. Cluster 1 bears two C(5)Me(5) and two diphenyldithiolene ligands on the four iron atoms, and there are three Fe-Fe bonds, so that Fe4S4 core is highly distorted. The Fe-Fe bonding distances are 2.711(1), 2.717(1), and 2.789(1) Angstrom. The remaining three distances are 3.400(1), 3.255(1), and 3.270(1) Angstrom. Cluster 2 contains an Fe4S5 core which consists of four iron atoms, three mu(3)-S ligands, and one mu(3)-S-2 ligand. Three iron atoms in the Fe4S5 core have C(5)Me(5) ligands and the fourth iron atom is coordinated by a diphenyldithiolene ligand. The mu(3)-S-2 ligand is located on the opposite side of the fourth iron atom. There are two Fe-Fe bonds, the lengths of which are 2.716(1) and 2.725(1) A. The other four distances are long, ranging from 3.300(1) to 3.769(1) Angstrom. Crystals of 1.CH2Cl2 (C49H52Cl2Fe4S8) belong to the monoclinic space group P2(1)/a with a = 20.679(3) Angstrom, b = 20.130(3) Angstrom, c = 12.742(2) Angstrom, beta = 104.97(2)degrees, V = 5124(1) Angstrom(3), Z = 4, and R(F-o) = 0.069 for 9193 reflections with \F-o\ greater than or equal to 3 sigma(F-o); those of 2.THF (C48H63Fe4OS7) belong to the monoclinic space group P2(1)/c with a 17.302(3) Angstrom, b = 17.639(2) Angstrom, c = 17.099(3) Angstrom, beta = 102.99(3)degrees, V = 5058(1) Angstrom(3), Z = 4 and R(F-o) = 0.058 for 8164 reflections with \F-o\ greater than or equal to 3 sigma(F-o).