A New Route to the Synthesis of Phosphine-Substituted Diiron Aza- and Oxadithiolate Complexes

Abstract

Diiron dithiolate complexes have received special attention because of their structural similarity to the active site of [FeFe]-hydrogenases, which are the most efficient and fastest catalysts for the generation of dihydrogen in nature. Recently, we established a novel and efficient way to prepare phosphinesubstituted diiron aza-and oxadithiolate complexes. Reaction of Fe 2 (μ-SCH 2 OH) 2 (CO) 6 and several phosphine ligands L (L = PPh 3 , PPh 2 (2-C 5 H 4 N), P(C 6 H 4 -4-CH 3 ) 3 ) affords the intermediate Fe 2 (μ-SCH 2 OH) 2 (CO) 5 L, while the intermediate in situ reacts with primary amines RNH 25 [PPh 2 (2-C 5 H 4 N)] (5), Fe 2 [(μ-SCH 2 ) 2 NCH 2 CH 2 CH 2 SCH 3 ](CO) 5 [P(C 6 H 4 -4-CH 3 ) 3 ] (6), Fe 2 [(μ-SCH 2 ) 2 N C 6 H 4 -4-CH 3 ](CO) 5 [PPh 2 (2-C 5 H 4 N)] (7), and Fe 2 [(μ-SCH 2 ) 2 N C 6 H 4 -4-CH 3 ](CO) 5 [P(C 6 H 4 -4-CH 3 ) 3 ] (8) in moderate yields. A novel complex Fe 2 [(μ-SCH 2 ) 2 NCH 2 CH 2 PPh 2 ](CO) 5 (9) can be obtained by reaction of Fe 2 (μ-SCH 2 OH) 2 (CO) 6 and Ph 2 PCH 2 CH 2 NH 2 . In addition, according to the same strategy, phosphine-substituted diiron oxadithiolate complexes Fe 2 [(μ-SCH 2 ) 2 O](CO) 5 [P(C 6 H 4 -4-F) 3 ] (10), Fe 2 [(μ-SCH 2 ) 2 O](CO) 5 [P(C 6 H 4 -4-CH 3 ) 3 ] (11), and Fe 2 [(μ-SCH 2 ) 2 O](CO) 5 (Ph 2 PCH 2 CH 3 ) ( 12) have been successfully synthesized. All of the new complexes 1−12 were fully characterized by elemental analysis, IR, and NMR spectroscopy, and particularly for 1−4, 6, 7, and 9−11 by X-ray single diffraction analysis. Moreover, complexes 1 and 10 were found to be catalysts for H 2 production under electrochemical conditions.

Electrocatalytic properties of diiron ethanedithiolate complexes containing benzoate ester

“…As shown in Figures , complexes 3 – 7 consist of a butterfly diiron cluster with a bridging ethanedithiolate containing a benzoate ester, five terminal carbonyls and a tertiary phosphine ligand. The phosphine ligands occupy an apical position of the distorted square‐pyramidal coordination sphere of the iron atom, in good agreement with the monophosphine‐substituted diiron derivatives . The Fe1Fe2 bond distances (2.4994(8) Å for 3 , 2.5156(8) Å for 4 , 2.4985(5) Å for 5 , 2.5041(8) Å for 6 and 2.5086(12) Å for 7 ) are shorter than those of the natural enzyme .…”

Synthesis, characterization, and electrochemistry of monophosphine‐containing diiron propane‐1,2‐dithiolate complexes related to the active site of [FeFe]‐hydrogenases

“…The IR spectra of complexes 2 – 6 show three absorption bands in the region of 2050–1933 cm −1 for the stretching vibration modes of the terminal carbonyls C ≡ O, shifting to lower frequencies as compared with those of the parent complex 1 (2076, 2035, 2005, 1991, 1981 cm −1 ) because of the phosphine ligand having a stronger electron‐donating characteristic than CO . In addition, the ν C ≡ O values are consistent with the monophosphine‐substituted diiron analogs, but much smaller than those of the diphosphine‐chelated diiron analogs . The 31 P{ 1 H} NMR spectra of complexes 2 – 6 show a single resonance in the range of δ 61–65 ppm, similar to the phosphine‐substituted diiron analogs, but notably larger than those of the free ligands due to the different coordination environment.…”

Unexpected Reaction of Fe3(CO)12 with Dialkyldithiophosphate: The Case of P–S Bond Activation

“…Upon addition of TFA, the current intensity of the reduction peak at –1.84 V grows up obviously with increasing concentration of TFA. All together, these observations imply that complex 2 has the ability to electrocatalytic reduction of proton to dihydrogen …”