Synthesis and Characterization of Neutral Hexanuclear Iron Sulfur Clusters Containing Stair-like [Fe6(3-S)4
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- 作者：Frank Osterloh ; Wolfgang Saak ; Siegfried Pohl ; Monika Kroeckel ; Christian Meier ; and Alfred X. Trautwein
- 刊名：Inorganic Chemistry
- 出版年：1998
- 出版时间：July 13, 1998
- 年：1998
- 卷：37
- 期：14
- 页码：3581 - 3587
- 全文大小：156K
- 年卷期：v.37,no.14(July 13, 1998)
- ISSN：1520-510X
文摘
The binuclear iron complex [{Fe("EtN2S2")}2] (1b, "EtN2S2" = N,N'-diethyl-3,7-diazanonane-1,9-dithiolate) wasprepared from the free ligand and ferrous bis[bis(trimethylsilyl)amide] in toluene. In dichloromethane 1b reactswith the [Fe4S4I4]2- cubane cluster to displace two iodo ligands and to form the neutral hexanuclear cluster[{Fe("EtN2S2")}2Fe4S4I2] (2), which is isolated as black crystals in 87% yield. As elucidated by an X-ray structureanalysis, 2 contains the novel hexanuclear stair-like [Fe6(
3-S)4(2-SR)4] core, which exhibits crystallographicinversion symmetry. The compound crystallizes as a solvate with two molecules of CH2Cl2 per formula unit inthe monoclinic space group P21/n with a = 1570.5(2) pm, b = 1060.2(1) pm, c = 1604.0(2) pm, 
= 114.93(1)
,and Z = 2. In the aprotic polar solvents DMF, 1,2-propylenecarbonate, and DMSO, 2 dissolves with decompositionand formation of the cluster [{Fe("EtN2S2")}2Fe4S5] (3), which is isolated as black needles from DMF. 3·2DMFcrystallizes in the triclinic space group P
with a = 950.9(1) pm, b = 1086.0(1) pm, c = 2381.5(2) pm, 
=101.81(1), = 91.94(1), 
= 97.01(1), and Z = 2. The neutral compound contains a nest-like [Fe6(4-S)(3-S)2(2-S)2(2-SR)4] core of idealized C2v symmetry that is closely related to that of other well-known clusters,e.g., the cluster anion [Fe6S9(SR)2]4-. The zero-field 57Fe Mössbauer spectrum of 3 is in accordance with fourFe2.5+S4 centers (
= 0.46 mm/s; 
EQ = 1.14 mm/s) and two N2S3-bound high-spin Fe2+ sites ( = 0.83 mm/s;EQ = 3.64 mm/s). A total cluster spin of 0 is deduced from the Mössbauer spectrum at 4.2 K and 5.3 T, whichyields magnetic splitting from the applied field only. For 2, three subspectra are observed in the Mössbauerspectrum (a, = 0.45 mm/s, EQ = 1.05 mm/s; b, = 0.55 mm/s, EQ = 1.61 mm/s, c, = 0.80 mm/s; EQ= 3.83 mm/s) reflecting different coordination environments of the iron atoms rather than different oxidationstates. The electrochemical properties of 1b, 2, and 3 were determined by cyclic voltammetry. 1b can be quasi-reversibly oxidized in dichloromethane solution at -75 mV (vs SCE). Whereas 2 shows only an irreversibleredox behavior in N,N'-dimethylimidazolidin-2-one solution, 3 in the same solvent can be quasi-reversibly reducedin two consecutive steps at -830 and -1630 mV (vs SCE) to the dianion, which consists entirely of Fe(II).
3-S)4(2-SR)4] core, which exhibits crystallographicinversion symmetry. The compound crystallizes as a solvate with two molecules of CH2Cl2 per formula unit inthe monoclinic space group P21/n with a = 1570.5(2) pm, b = 1060.2(1) pm, c = 1604.0(2) pm, = 114.93(1),and Z = 2. In the aprotic polar solvents DMF, 1,2-propylenecarbonate, and DMSO, 2 dissolves with decompositionand formation of the cluster [{Fe("EtN2S2")}2Fe4S5] (3), which is isolated as black needles from DMF. 3·2DMFcrystallizes in the triclinic space group P with a = 950.9(1) pm, b = 1086.0(1) pm, c = 2381.5(2) pm, =101.81(1), = 91.94(1), = 97.01(1), and Z = 2. The neutral compound contains a nest-like [Fe6(4-S)(3-S)2(2-S)2(2-SR)4] core of idealized C2v symmetry that is closely related to that of other well-known clusters,e.g., the cluster anion [Fe6S9(SR)2]4-. The zero-field 57Fe Mössbauer spectrum of 3 is in accordance with fourFe2.5+S4 centers ( = 0.46 mm/s; EQ = 1.14 mm/s) and two N2S3-bound high-spin Fe2+ sites ( = 0.83 mm/s;EQ = 3.64 mm/s). A total cluster spin of 0 is deduced from the Mössbauer spectrum at 4.2 K and 5.3 T, whichyields magnetic splitting from the applied field only. For 2, three subspectra are observed in the Mössbauerspectrum (a, = 0.45 mm/s, EQ = 1.05 mm/s; b, = 0.55 mm/s, EQ = 1.61 mm/s, c, = 0.80 mm/s; EQ= 3.83 mm/s) reflecting different coordination environments of the iron atoms rather than different oxidationstates. The electrochemical properties of 1b, 2, and 3 were determined by cyclic voltammetry. 1b can be quasi-reversibly oxidized in dichloromethane solution at -75 mV (vs SCE). Whereas 2 shows only an irreversibleredox behavior in N,N'-dimethylimidazolidin-2-one solution, 3 in the same solvent can be quasi-reversibly reducedin two consecutive steps at -830 and -1630 mV (vs SCE) to the dianion, which consists entirely of Fe(II).