Syntheses, crystal structures, and electrochemical studies of dinuclear coordination compounds with the Fe<sub>2</sub>(CO)<sub>6</sub> core

<p>Reaction of 2-C<sub>5</sub>H<sub>4</sub> NCOSPh, generated from 2-C<sub>5</sub>H<sub>4</sub>NCO<sub>2</sub>H and PhSH in the presence of DCC, with Fe<sub>3</sub>(CO)<sub>12</sub> affords (μ-κ<sup>2</sup>C,N-2-C<sub>5</sub>H<sub>4</sub>N)(μ-PhS)Fe<sub>2</sub>(CO)<sub>6</sub> (<b>1</b>) and (μ-PhS)<sub>2</sub>Fe<sub>2</sub>(CO)<sub>6</sub> (<b>2</b>). Reaction of (NC)<sub>2</sub>C=C(SMe)<sub>2</sub>, formed from NCCH<sub>2</sub>CN, CS<sub>2</sub>, and MeI in the presence of NaOH, with Fe<sub>3</sub>(CO)<sub>12</sub> provides (μ-κ<sup>2</sup>C,S-(NC)<sub>2</sub>C=CSMe)(μ-MeS)Fe<sub>2</sub>(CO)<sub>6</sub> (<b>3</b>) and (μ-MeS)<sub>2</sub>Fe<sub>2</sub>(CO)<sub>6</sub> (<b>4</b>). All complexes have been fully characterized by EA, IR, <sup>1</sup>H NMR, and <sup>13</sup>C NMR spectroscopy and structurally determined by X-ray crystallography. In <b>1</b> and <b>3</b>, the group attached to the bridging S is at the equatorial position. In <b>2</b>, two phenyl groups are at equatorial positions. Two isomers of <b>4</b>, ae-<b>4</b> and ee-<b>4</b>, can be separated by thin-layer chromatography. DFT calculations reveal that the Gibbs energy difference between ae-<b>4</b> and ee-<b>4</b> is −2.17 kcal mol<sup>−1</sup> in THF and −2.29 kcal mol<sup>−1</sup> in benzene, and the isomerization barrier between ae-<b>4</b> and ee-<b>4</b> is 14.92 kcal mol<sup>−1</sup> in THF and 16.84 kcal mol<sup>−1</sup> in benzene. All these results suggest that ae-<b>4</b> is more stable than ee-<b>4</b> in either THF or benzene, and the two isomers do not interconvert. Electrochemical studies of <b>1</b> and <b>3</b> demonstrate that using HOAc as a proton source <b>1</b> and <b>3</b> can catalyze H<sub>2</sub> production.</p>