The reactions of pyridinyl thioesters with triiron dodecacarbonyl: their novel diiron carbonyl complexes and mechanistic investigations

Abstract

Reaction of Fe(3)(CO)(12) with pyridinyl thioester ligand PyCH(2)SCOCH(3) (L(1), Py = pyridin-2-yl) produced complex, [Fe(2)(κ-COCH(3))(μ-SCH(2)Py)(CO)(5)] (1) (PyCH(2)S = pyridin-2-ylmethanethiolate). When complex 1 reacted with PPh(3), a monosubstituted complex, [Fe(2)(κ-COCH(3))(μ-SCH(2)Py)(CO)(4)PPh(3)] (2), was derived. Reaction of the same precursor with analogous thioester ligand PyCH(2)SCOPy (L(2)) generated three novel diiron complexes, [Fe(2)(κ-Py)(μ-SCH(2)Py)(CO)(5)] (3), [Fe(2)(κ-Py)'(μ-SCH(2)Py)(CO)(5)] (4), and [Fe(2)(κ-Py)(μ-SCH(2)Py)(CO)(6)] (5). Complexes 3 and 4 are structural isomers. Complex 5 could be converted into complex 4 but the conversion from complex 5 to the isomer 3 was not observed. All the five complexes were fully characterised using FTIR, NMR, and other techniques. Their structures were determined using X-ray single crystal diffraction analysis. The oxidative formation of complexes 1, 3, 4, and 5 involved C-S and/or C-C bonds cleavages. To probe possible mechanisms for these cleavages, DFT calculations were performed. From the calculations, viable reaction pathways leading to the formation of all the isolated products were delineated. The results of the theoretic calculations also allowed rationalisation of the experimental observations.

[FeFe]‐Hydrogenase Mimic Employing κ2‐C,N‐Pyridine Bridgehead Catalyzes Proton Reduction at Mild Overpotential

“…Single crystals of 2 were obtained by slow evaporation of a pentane solution under argon at 5 °C. The crystal structures are similar to previously reported κ 2 ‐ C , N ‐pyridine bridged di‐iron compounds (Figure ) , . The Fe1–Fe2 bond lengths of 1 and 2 are 2.5741(5) and 2.5726(5) Å, respectively.…”

“…These bonds are slightly longer than the Fe–Fe bond length in [Fe 2 ( µ ‐bdt)(CO) 6 ] (2.480(2) Å) and [Fe 2 ( µ ‐pdt)(CO) 6 ] (2.5103(11) Å). The Fe2–C7 bond length is 1.996(3) Å for 1 and 1.992(2) Å for 2 and this is comparable to the Fe–C bond length in similar κ 2 ‐ C , N bridged hydrogenase mimics . The Fe1–N1 bond is 1.984(2) for 1 and a little shorter for 2 (1.9744(19) Å).…”

“…The class of hydrogenase mimics based on a bridging pyridine–monothiolato ligand is relatively unexplored. The synthesis of such complexes has been described from the corresponding thioester, and to the best of our knowledge there is only one earlier report on the catalytic activity in the presence of acetic acid…”

Synthesis of Diiron(I) Dithiolato Carbonyl Complexes

“…Pyridine-containing thioesters react with Fe(0) carbonyls to give thiolate/pyridyl-bridged diiron hexacarbonyl complexes. 279 …”

Diiron Azamonothiolates by the Scission of Dithiadiazacyclooctanes by Iron Carbonyls

“…Long has described a related Fe 2 (CO) 6 complex with a μ-pyridyl group. [9] The Fe-Fe distance in that complex is comparable to that in 1 Me .…”