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The first examples of diselenolate ligand-containing butterfly Fe/E (E = S, Se) complexes are now reported. When ca. 1 equiv of dilithium reagent 4-LiC6H4C6H4Li-4‘ containing n-BuBr (prepared from 1 equiv of 4,4‘-dibromobiphenyl and n-BuLi) was treated with 2 equiv of elemental selenium and Fe3(CO)12 followed by treatment with excess CS2 and MeI, both double-butterfly complex (4-μ-SeC6H4C6H4Se-μ-4‘)[(μ-SCSMe)Fe2(CO)6]2 (4) and single-butterfly complex (4-n-BuSeC6H4C6H4Se-μ-4‘)[(μ-SCSMe)Fe2(CO)6] (4*) were produced in 11% and 20% yields, respectively. However, when ca. 1 equiv of dilithium reagent 4-LiC6H4C6H4Li-4‘ without n-BuBr (n-BuBr was removed by evaporation of the initially prepared dilithium reagent containing n-BuBr) reacted with 2 equiv of elemental selenium and Fe3(CO)12 followed by treatment with excess CS2 and MeI, only the double-butterfly complex 4 was obtained in a higher yield (21%) without any single-butterfly complex being isolated. Other double-butterfly complexes, such as (4-μ-SeC6H4C6H4Se-μ-4‘)[(μ-SCSR)Fe2(CO)6]2 (5, R = Et; 6, PhCH2; 7, PhCNPh; 8, Cp(CO)2Fe), (4-μ-SeC6H4C6H4Se-μ-4‘)[(μ-SePh)Fe2(CO)6]2 (9), and (4-μ-SeC6H4C6H4Se-μ-4‘)[(μ-CH2SMe)Fe2(CO)6]2 (10), could be similarly prepared via the latter method by using electrophiles CS2/EtBr, CS2/PhCH2Br, CS2/PhC(Cl)NPh, CS2/Cp(CO)2FeI, PhSeBr, and MeSCH2Cl instead of CS2/MeI, respectively. A possible pathway for production of the double- and single-butterfly complexes 4−10 and 4* has been proposed, in which the versatile two-μ-CO-containing double-butterfly dianion (4-μ-SeC6H4C6H4Se-μ-4‘)[(μ-CO)Fe2(CO)6]2 2- (3) and the one-μ-CO-containing single-butterfly monoanion (4-n-BuSeC6H4C6H4Se-μ-4‘)[(μ-CO)Fe2(CO)6]- (3*) are involved. All the new complexes were fully characterized by elemental analysis and spectroscopy, as well as by X-ray crystallography for 4* and 10.

The butterfly Fe/S cluster anions (µ-RS)(µ-S -)Fe 2 (CO) 6 (A, R ) Et, p-MeC 6 H 4 ), (µ-S -) 2 Fe 2 (CO) 6 (C), [(µ-S -)Fe 2 (CO) 6 ] 2 (4-µ-SC 6 H 4 C 6 H 4 S-µ-4′) (D), and [(µ-S -)Fe 2 (CO) 6 ] 2 [4-µ-SC 6 H 4 OCH 2 CH 2 OC 6 H 4 Sµ-4′] (E) (generated in situ via reactions of (µ-S 2 )Fe 2 (CO) 6 with RMgBr, Et 3 BHLi, 4-LiC 6 H 4 C 6 H 4 Li-4′, and 4-LiC 6 H 4 OCH 2 CH 2 OC 6 H 4 Li-4′) were found to react with Ph 2 PCl to give a series of novel butterfly Fe/S/P cluster complexes. Treatment of monoanions A (R ) Et, p-MeC 6 H 4 ) with 1 equiv of Ph 2 PCl in THF from -78 °C to room temperature gave the single-butterfly Fe 2 S 2, whereas dianions C, D, and E reacted with 2 equiv of Ph 2 PCl to give single-butterfly Fe 2 S 2 P 2 complex (η 1 -Ph 2 PS-η 1 ) 2 Fe 2 (CO) 6 ( 11) and double-butterfly Fe 4 S 4 P 2 complexes [(η 1 -Ph 2 PS-η 1 )Fe 2 (CO) 6 ] 2 (4-µ-SC 6 H 4 C 6 H 4 S-µ-4′) ( 12) and [(η 1 -Ph 2 PS-η 1 )Fe 2 (CO) 6 ] 2 [4-µ-SC 6 H 4 OCH 2 CH 2 OC 6 H 4 S-µ-4′] (13), respectively. More interestingly, the novel µ 4 -S-containing doublebutterfly Fe 4 S 2 P complexes [(µ-RS)Fe 2 (CO) 6 ](µ 4 -S)[(µ-Ph 2 P)Fe 2 (CO) 6 ] (14, R ) Me; 15, R ) Ph; 16, R ) Et) could be prepared by reactions of single-butterfly complexes (µ-RS)(η 1 -Ph 2 PS-η 1 )Fe 2 (CO) 6 (1, R ) Me; 3, R ) Ph; 7 R ) Et) with excess Fe 2 (CO) 9 in THF at room temperature, whereas the quadruplebutterfly Fe 8 S 4 P 2 complexes [(µ-Ph 2 P)Fe 2 (CO) 6 (µ 4 -S)Fe 2 (CO) 6 ] 2 (4-µ-SC 6 H 4 C 6 H 4 S-µ-4′) ( 17) and [(µ-Ph 2 P)Fe 2 (CO) 6 (µ 4 -S)Fe 2 (CO) 6 ] 2 [4-µ-SC 6 H 4 OCH 2 CH 2 OC 6 H 4 S-µ-4′] (18) were similarly prepared by reactions of the corresponding double-butterfly complexes 12 and 13 with excess Fe 2 (CO) 9 , respectively. All the new complexes 7-18 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.

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