Metal Carbonyl Derivatives of Sulfur-Containing Quinones and Hydroquinones: Synthesis, Structures, and Electrochemical Properties

The reaction of CpMoMn(μ-S2)(CO)5, 1, with 1,4-benzoquinone in the presence of irradiation with visible light
yielded the quinonedithiolato complex CpMoMn(CO)5(μ-S2C6H2O2), 2. The new complex CpMoMn(CO)5(μ-S2C6Cl2O2) (4) was synthesized similarly from 1 and 2,3-dichloro-1,4-benzoquinone. Compounds 2 and 4 were reduced
with hydrogen to yield the hydroquinone complexes CpMoMn(CO)5[μ-S2C6H2(OH)2], 3, and CpMoMn(CO)5[μ-S2C6Cl2(OH)2], 5. UV−vis irradiation of solutions of Fe2(CO)6(μ-S2) and 1,4-benzoquinone yielded the hydroquinone
complex Fe2(CO)6[μ-S2C6H2(OH)2], 6. Compound 6 was oxidized to the quinone complex Fe2(CO)6(μ-S2C6H2O2),
7, by using 2,3-dichloro-5,6-dicyano-1,4-benzoquinone. Substitution of the CO ligands on 6 by PPh3 yielded the
derivatives Fe2(CO)5(PPh3)[μ-S2C6H2(OH)2], 8, and Fe2(CO)4(PPh3)2[μ-S2C6H2(OH)2], 9. The electrochemical properties
of 3, 5, 6, 8, and 9 were measured by cyclic voltammetry. The molecular structure of each of the new compounds
2−9 was established by single-crystal X-ray diffraction analyses.