Synthesis, characterization and crystal structures of carboxy-functionalized diiron propanedithiolate complexes

Four new carboxy-functionalized diiron propanedithiolate complexes 1–4 have been successfully synthesized and fully characterized. The all-carboxyl complexes [(μ-SCH2)2CHCO2CH2CH2Cl][Fe2(CO)6] (1) and [(μ-SCH2)2CHCO2C6H4I-p][Fe2(CO)6] (2) were prepared by the condensation reaction of the known complex [(μ-SCH2)2CHCO2H][Fe2(CO)6] (A) with ClCH2CH2OH and p-IC6H4OH in the presence of 4-dimethylaminopyridine (DMAP) and dicyclohexylcarbodiimide (DCC) in yields of 46% and 66%, whereas the phosphine-substituted complexes [(μ-SCH2)2CHCO2CH2CH2Cl][Fe2(CO)5PPh3] (3) and [(μ-SCH2)2CHCO2CH2CH2Cl][Fe2(CO)4(PPh3)2] (4) were further synthesized through the carbonyl substitution reaction of 1 with PPh3 using the decarbonylating agent Me3NO·2H2O in yields of 44% and 41%. The new complexes 1–4 were characterized by combustion analysis, IR and 1H, 13C and 31P NMR spectroscopic techniques. The molecular structures of 1–4 were unequivocally determined by single crystal X-ray diffraction analysis, in which the carboxy-functionalized substituent attached to the bridgehead-C atom resides in an equatorial position of the six-membered rings in the solid state.

Graphical abstractReactions of the known complex A with ClCH2CH2OH or p-IC6H4OH in the presence of DMAP and DCC gave the carboxy-functionalized all-carbonyl complex 1 or 2, respectively. Further treatment of 1 with PPh3 in the presence of Me3NO·2H2O afforded the PPh3-monosubstitued complex 3, together with the PPh3-disubstitued complex 4. The new complexes 1–4 were characterized by combustion analysis, IR and NMR spectroscopies, as well as by single crystal X-ray diffraction analysis.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► We prepared four carboxy-functionalized diiron propanedithiolate complexes. ► The new complexes were characterized by elemental analysis IR, and NMR spectroscopies. ► Their structures were determined by single crystal X-ray diffraction analysis.