om800077c_si_002.cif (23.52 kB)

Synthetic and Structural Studies of Butterfly Fe/S/P Cluster Complexes Related to the Active Site of [FeFe]-Hydrogenases. Proton Reduction to H2 Catalyzed by (η1-Ph2PS-η1)2Fe2(CO)6

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posted on 11.08.2008, 00:00 by Li-Cheng Song, Guang-Huai Zeng, Shao-Xia Lou, Hui-Ning Zan, Jiang-Bo Ming, Qing-Mei Hu
The butterfly Fe/S cluster anions (μ-RS)(μ-S)Fe2(CO)6 (A, R = Et, p-MeC6H4), (μ-S)2Fe2(CO)6 (C), [(μ-S)Fe2(CO)6]2(4-μ-SC6H4C6H4S-μ-4′) (D), and [(μ-S)Fe2(CO)6]2[4-μ-SC6H4OCH2CH2OC6H4S-μ-4′] (E) (generated in situ via reactions of (μ-S2)Fe2(CO)6 with RMgBr, Et3BHLi, 4-LiC6H4C6H4Li-4′, and 4-LiC6H4OCH2CH2OC6H4Li-4′) were found to react with Ph2PCl to give a series of novel butterfly Fe/S/P cluster complexes. Treatment of monoanions A (R = Et, p-MeC6H4) with 1 equiv of Ph2PCl in THF from −78 °C to room temperature gave the single-butterfly Fe2S2P complexes (μ-RS)(η1-Ph2PS-η1)Fe2(CO)6 (7, R = Et; 9, R = p-MeC6H4) and (μ-RS)(η1-Ph2PS-η1)Fe2(CO)5(Ph2PY) (8, R = Et, Y = Cl; 10, R = p-MeC6H4, Y = p-MeC6H4), whereas dianions C, D, and E reacted with 2 equiv of Ph2PCl to give single-butterfly Fe2S2P2 complex (η1-Ph2PS-η1)2Fe2(CO)6 (11) and double-butterfly Fe4S4P2 complexes [(η1-Ph2PS-η1)Fe2(CO)6]2(4-μ-SC6H4C6H4S-μ-4′) (12) and [(η1-Ph2PS-η1)Fe2(CO)6]2[4-μ-SC6H4OCH2CH2OC6H4S-μ-4′] (13), respectively. More interestingly, the novel μ4-S-containing double-butterfly Fe4S2P complexes [(μ-RS)Fe2(CO)6](μ4-S)[(μ-Ph2P)Fe2(CO)6] (14, R = Me; 15, R = Ph; 16, R = Et) could be prepared by reactions of single-butterfly complexes (μ-RS)(η1-Ph2PS-η1)Fe2(CO)6 (1, R = Me; 3, R = Ph; 7 R = Et) with excess Fe2(CO)9 in THF at room temperature, whereas the quadruple-butterfly Fe8S4P2 complexes [(μ-Ph2P)Fe2(CO)64-S)Fe2(CO)6]2(4-μ-SC6H4C6H4S-μ-4′) (17) and [(μ-Ph2P)Fe2(CO)64-S)Fe2(CO)6]2[4-μ-SC6H4OCH2CH2OC6H4S-μ-4′] (18) were similarly prepared by reactions of the corresponding double-butterfly complexes 12 and 13 with excess Fe2(CO)9, respectively. All the new complexes 718 have been characterized by elemental analysis, by spectroscopy, and for 9, 11, and 14 by X-ray crystallography. In view of the structural similarity of these Fe/S/P complexes to the [FeFe]-hydrogenase active site, they might be regarded as H-cluster models. As a representative, model complex 11 was found to be able to catalyze proton reduction to hydrogen under CV conditions.