Electron‐Rich Diferrous–Phosphane–Thiolates Relevant to Fe‐only Hydrogenase: Is Cyanide “Nature's Trimethylphosphane”?

Abstract

The two-step one-pot oxidative decarbonylation of [Fe2(S2C2H4)(CO)4(PMe3)2] (1) with [FeCp2]PF6, followed by addition of phosphane ligands, led to a series of diferrous dithiolato carbonyls 2-6, containing three or four phosphane ligands. In situ measurements indicate efficient formation of 1(2+) as the initial intermediate of the oxidation of 1, even when a deficiency of the oxidant was employed. Subsequent addition of PR3 gave rise to [Fe2(S2C2H4)(mu-CO)(CO)3(PMe3)3]2+ (2) and [Fe2(S2C2H4)(mu-CO)(CO)2(PMe3)2(PR3)2]2+ (R = Me 3, OMe 4) as principal products. One terminal CO ligand in these complexes was readily substituted by MeCN, and [Fe2(S2C2H4)(mu-CO)(CO)2(PMe3)3(MeCN)]2+ (5) and [Fe2(S2C2H4)(mu-CO)(CO)(PMe3)4(MeCN)]2+ (6) were fully characterized. Relevant to the H(red) state of the active site of Fe-only hydrogenases, the unsymmetrical derivatives 5 and 6 feature a semibridging CO ligand trans to a labile coordination site.

Terahertz, infrared and Raman vibrational assignments of [FeFe]-hydrogenase model compounds

“…Interest in these compounds quickly waned, however, as no practical applications were readily apparent. These compounds became the subject of renewed interest when it was discovered that their structure (for example, Fe 2 (-S 2 C 3 H 6 )(CO) 6 (1), Fig. 1b) closely matches that of the active site of the [FeFe]-hydrogenases (Fig.…”

Electrochemical Synthesis of Mono‐ and Disubstituted Diiron Dithiolate Complexes as Models for the Active Site of Iron‐Only Hydrogenases

“…On the other hand, it was shown that electron transfer (reduction or oxidation) could also lead to substituted diiron dithiolates. [38,41,42] For example, the formation of [Fe 2 (S 2 C 2 H 4 )(CO) 5 {P(OMe) 3 }] by an electron-transfercatalyzed chain reaction was detected upon the electrochemical reduction of the all-CO parent compound in the presence of P(OMe) 3 . [41] A similar approach allowed us to selectively prepare [Fe 2 (S 2 C 6 H 4 )(CO) 5 {P(OMe) 3 }] in good yield.…”

Synthesis and structural characterization of sulfur rich iron (II) carbonyl dimers: Facile reversible reaction with carbon monoxide

“…2). The [2Fe-2S] core of complex 1 is planar, unlike the other reported diferrous carbonyl complexes, which exhibit the butterfly core present in the Fe 2 hydrogenases [13][14][15]. The Fe-S distances in complex 1 are in the range typical of low-spin Fe(II) thiolate and thioether complexes.…”