Reaction of a trithiol ligand, 2-(mercaptomethyl)-2-methylpropane-1,3-dithiol (H<sub>3</sub>L), with tri-iron dodecacarbonyl in toluene produces two hexa-iron clusters (1 and 2). The two clusters are characterised crystallographically and spectroscopically. NMR spectroscopy reveals that the cluster 2 exists in two conformations in equilibrium 2<sub>anti</sub> ⇔ 2<sub>syn</sub> and the equilibrium constant K<sub>eq</sub> = 0.55 under CO atmosphere. In the cluster 2, the central {Fe<sub>2</sub>S<sub>2</sub>(CO)<sub>6</sub>} sub-unit is flanked by two identical {Fe<sub>2</sub>S<sub>2</sub>(CO)<sub>6</sub>} satellite sub-units through thiolate linkages whereas one of the thiolate linkages can further form Fe-S bond with the proximal Fe atom in one of the two satellite sub-units to produce the cluster 1 by expelling one CO. This conversion can be entirely reversed by continuously purging CO through the solution of the cluster 1. As suggested by DFT calculations, the conversion features a key step, the rotation of the Fe<sub>prox</sub>(CO)<sub>3</sub> to expose a vacant site for exogenic ligand binding (the S atom from the central sub-unit in this case) with concomitant switch for one of the three CO ligands in the unit of Fe<sub>prox</sub>(CO)<sub>3</sub> from terminal to bridging orientation. The conversion from the clusters 1-2 involving one CO uptake is much faster than its reverse process since the latter is an endergonic process characterised by large reaction barriers, as revealed by the DFT calculations. © 2008 Elsevier B.V. All rights reserved.
Zhong, W., Zampella, G., Li, Z., DE GIOIA, L., Liu, Y., Zeng, X., et al. (2008). Synthesis, characterisation of two hexa-iron clusters with {Fe2S2(CO)x} (x = 5 or 6) fragments and investigation into their inter-conversion. JOURNAL OF ORGANOMETALLIC CHEMISTRY, 693(25), 3751-3759 [10.1016/j.jorganchem.2008.09.021].
Synthesis, characterisation of two hexa-iron clusters with {Fe2S2(CO)x} (x = 5 or 6) fragments and investigation into their inter-conversion
ZAMPELLA, GIUSEPPE;DE GIOIA, LUCA;
2008
Abstract
Reaction of a trithiol ligand, 2-(mercaptomethyl)-2-methylpropane-1,3-dithiol (H3L), with tri-iron dodecacarbonyl in toluene produces two hexa-iron clusters (1 and 2). The two clusters are characterised crystallographically and spectroscopically. NMR spectroscopy reveals that the cluster 2 exists in two conformations in equilibrium 2anti ⇔ 2syn and the equilibrium constant Keq = 0.55 under CO atmosphere. In the cluster 2, the central {Fe2S2(CO)6} sub-unit is flanked by two identical {Fe2S2(CO)6} satellite sub-units through thiolate linkages whereas one of the thiolate linkages can further form Fe-S bond with the proximal Fe atom in one of the two satellite sub-units to produce the cluster 1 by expelling one CO. This conversion can be entirely reversed by continuously purging CO through the solution of the cluster 1. As suggested by DFT calculations, the conversion features a key step, the rotation of the Feprox(CO)3 to expose a vacant site for exogenic ligand binding (the S atom from the central sub-unit in this case) with concomitant switch for one of the three CO ligands in the unit of Feprox(CO)3 from terminal to bridging orientation. The conversion from the clusters 1-2 involving one CO uptake is much faster than its reverse process since the latter is an endergonic process characterised by large reaction barriers, as revealed by the DFT calculations. © 2008 Elsevier B.V. All rights reserved.
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