Shupp J Patrick, Rose Amber R, Rose Michael J
Department of Chemistry, The University of Texas at Austin, USA.
Dalton Trans. 2017 Jul 18;46(28):9163-9171. doi: 10.1039/c7dt01506b.
We report the synthesis, interconversions and X-ray structures of a set of [mFe-nS]-type carbonyl clusters (where S = S, S or RS; m = 2-3; n = 1-2). All of the clusters have been identified and characterized by single crystal X-ray diffraction, IR and C NMR. Reduction of the parent neutral dimer [μ-(SPh)Fe(CO)] (1) with KC affords an easily separable ∼1 : 1 mixture of the anionic, dimeric thiolate dimer K[Fe(SPh)(CO)(μ-CO)] (2) and the dianionic, sulfido trimer [K(benzo-15-crown-5)][Fe(μ-S)(CO)] (3). Oxidation of 2 with diphenyl-disulfide (PhS) cleanly returns the starting material 1. The Ph-S bond in 1 can be cleaved to form sulfide trimer 3. Oxidation of sulfido trimer 3 with Fc in the presence of S cleanly affords the all-inorganic persulfide dimer [μ-(S)Fe(CO)] (4), a thermodynamically stable product. The inverse reactions to form 3 (dianion) from 4 (neutral) were not successful, and other products were obtained. For example, reduction of 4 with KC afforded the mixed valence Fe(i)/Fe(ii) species [((FeS)(CO))Fe] (5), in which the two {FeS(CO)} units serve as bidendate ligands to a Fe(ii) center. Another isolated product (THF insoluble portion) was recrystallized in MeCN to afford [K(benzo-15-crown-5)][((FeS)(CO))(μ-S)] (6), in which a persulfide dianion bridges two {2Fe-S} moieties (dimer of dimers). Finally, to close the interconversion loop, we converted the persulfide dimer 4 into the thiolate dimer 1 by reduction with KC followed by reaction with the diphenyl iodonium salt PhI, in modest yield. These reactions underscore the thermodynamic stability of the dimers 1 and 4, as well as the synthetic and crystallization versatility of using the crown/K counterion system for obtaining structural information on highly reduced iron-sulfur-carbonyl clusters.
