Syntheses, crystal structures, and electrochemical studies of dinuclear coordination compounds with the Fe2(CO)6 core
Reaction of 2-C5H4 NCOSPh, generated from 2-C5H4NCO2H and PhSH in the presence of DCC, with Fe3(CO)12 affords (μ-κ2C,N-2-C5H4N)(μ-PhS)Fe2(CO)6 (1) and (μ-PhS)2Fe2(CO)6 (2). Reaction of (NC)2C=C(SMe)2, formed from NCCH2CN, CS2, and MeI in the presence of NaOH, with Fe3(CO)12 provides (μ-κ2C,S-(NC)2C=CSMe)(μ-MeS)Fe2(CO)6 (3) and (μ-MeS)2Fe2(CO)6 (4). All complexes have been fully characterized by EA, IR, 1H NMR, and 13C NMR spectroscopy and structurally determined by X-ray crystallography. In 1 and 3, the group attached to the bridging S is at the equatorial position. In 2, two phenyl groups are at equatorial positions. Two isomers of 4, ae-4 and ee-4, can be separated by thin-layer chromatography. DFT calculations reveal that the Gibbs energy difference between ae-4 and ee-4 is −2.17 kcal mol−1 in THF and −2.29 kcal mol−1 in benzene, and the isomerization barrier between ae-4 and ee-4 is 14.92 kcal mol−1 in THF and 16.84 kcal mol−1 in benzene. All these results suggest that ae-4 is more stable than ee-4 in either THF or benzene, and the two isomers do not interconvert. Electrochemical studies of 1 and 3 demonstrate that using HOAc as a proton source 1 and 3 can catalyze H2 production.
