Structural and Electronic Variations of sp/sp2 Carbon-Based Bridges in Di- and Trinuclear Redox-Active Iron Complexes Bearing Fe(diphosphine)2X (X = I, NCS) Moieties

Abstract

Starting from the mononuclear precursor trans-Fe(depe)2I2 (depe = 1,2-bis(diethylphosphino)ethane), four dinuclear complexes IFe(depe)2–R–Fe(depe)2I, with R = 1,4-(−C≡C–C6H4–C≡C−) 1, 1,3-(−C≡C–C6H4–C≡C−) 2, 4,4′-(−C≡C–C6H4–C6H4–C≡C−) 3, and 2,5-(−C≡C–thiophene–C≡C−) 4, as well as a trinuclear complex, {I–Fe(depe)2(C≡C−)}3(1,3,5-C6H3)} 5, were prepared in a facile way by transmetalation from stannylated precursors. Substitution of the terminal iodides applying an excess of NaSCN yielded the corresponding isothiocyanate complexes 6–10 in very good yields. All complexes 1–10 are intrinsically functional due to the redox-active Fe centers embedded in a structurally rigid and covalent sp/sp2 framework. 1–10 were characterized by NMR, IR, and Raman spectroscopy, as well as elemental analyses. X-ray diffraction studies were carried out for 1, 2, 4, 5, 6, 8, and 9. Cyclic voltammetry was employed to explore the redox behavior of 1–10. The 1,4-(−C≡C–C6H4–C≡C−) and the 2,5-(−C≡C–thiophene–C≡C−) bridged compounds 1,...