Synthesis and Reactivity of Thioether-Dithiolate-Bridged Multi-iron

Apr 23, 2015 - Ying Li, Yahui Zhang, Dawei Yang, Yang Li, Puhua Sun, Baomin Wang, and Jingping Qu*. State Key Laboratory of Fine Chemicals, School of ...
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Synthesis and Reactivity of Thioether-Dithiolate-Bridged Multi-iron Complexes Ying Li, Yahui Zhang, Dawei Yang, Yang Li, Puhua Sun, Baomin Wang, and Jingping Qu* State Key Laboratory of Fine Chemicals, School of Pharmaceutical Science and Technology, Faculty of Chemical, Environmental and Biological Science and Technology, Dalian University of Technology, 2 Linggong Road, Dalian 116024, People’s Republic of China S Supporting Information *

ABSTRACT: The novel thioether-dithiolate-bridged diiron complex [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt)FeCp*] (1, Cp* = η5-C5Me5; tpdt = S(CH2CH2S−)2) has been prepared by the reaction of [Cp*FeCl]2 with Li2(tpdt) in THF. Given the thermodynamic instability of 1, a one-electron oxidation was performed with Fc·PF6 (Fc = ferrocene) affording 1[PF6]. Treatment of 1[PF6] with CO or tBuNC in CH2Cl2 gave complexes [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt){Cp*Fe(η1-CO)}][PF 6 ] (2[PF 6 ]) and [Cp*Fe(μ-1 κ 3 SSS′:2 κ 2 SS-tpdt){Cp*Fe(η1-tBuNC)}][PF6] (3[PF6]). In addition, complex 1[PF6] can be further oxidized into [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt)FeCp*][PF6]2 (1[PF6]2) by Fc·PF6 in THF, while in the presence of MeCN resulting in the formation of complex [Cp*Fe(μ-1κ3SSS′:2κ2SStpdt){Cp*Fe(η1-MeCN)}][PF6]2 (4[PF6]2). When the solution of complex 1 in THF was warmed to room temperature, thioether-dithiolate-bridged trinuclear iron complex [Cp*Fe(μ1κ3SSS′:2κ2SS-tpdt)Fe(μ-2κ2SS:3κ3SSS′-tpdt)FeCp*] (5), which can be oxidized into complex [Cp*Fe(μ-1κ3SSS′:2κ2SStpdt)Fe(μ-2κ2SS:3κ3SSS′-tpdt)FeCp*][PF6]2 (5[PF6]2) with Fc·PF6, was obtained accompanied by byproduct Cp*2Fe. Complex 5 is sensitive to air and upon exposure to air in THF gave monoiron complex [Cp*Fe(tpdt)] (6) in moderate yield. Complex 6 is a good metallothiolato precursor for synthesis of homo- and heterobimetallic or trimetallic complexes. The binuclear complex [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt)FeCl2] (7) can be prepared by the reaction of complex 6 with anhydrous FeCl2 in CH2Cl2. Complex 5[PF6]2 can also be obtained by the reaction of complex 6 with FeCl2 or complex 7 in the presence of NH4·PF6. These complexes have been spectroscopically and crystallographically characterized.

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INTRODUCTION The continuingly increasing interest in iron−sulfur clusters is stimulated by their significant relevance to biological process such as electron transfer, catalysis, and regularization.1 In the past few decades, a variety of novel metal complexes containing different sulfur donor ligands were synthesized as nitrogenase2 or hydrogenase 3 biomimetic complexes. Thiolates play an important role in the construction of bi- or polynuclear compounds due to their high bridging tendency. Dinuclear iron−sulfur complexes using monothiolates (RS−) as sulfur ligands have been extensively studied.4−7 However, dinuclear iron−sulfur complexes with dithiolates (−SRS−),8,9 especially the tridentate dithiolate-thioether ligand incorporating both thioether and thiolate sulfur atoms, such as 3-thiapentane-1,5dithiolate, S(CH2CH2S−)2 (tpdt),9 are less common in comparison. Bidentate or multidentate thiolates can avoid the degradative fragmentation of multimetal complexes in a cooperative process of mimicking biological metalloproteins. The tpdt ligand has been found in other transition metal thiolatebridged dinuclear complexes of Ru,10a Ir,10d In,11 and Ni12 and trinuclear complexes of Pd12 and Ru10b,c wherein there is an endocyclic and transannular M···S (thioether) interaction as a stabilizing factor of the complex. Moreover, the tpdt ligand is also © XXXX American Chemical Society

applied in the biomimicry of the active sites of [NiFe]hydrogenase.13 In the course of our studies of structural and functional models of the active site of biological nitrogenase, we have reported monothiolate-bridged diiron complexes [Cp*Fe(μ-SR)3FeCp*] (R = Me, Et, Ph)6b and the dithiolate diiron complex [Cp*Fe(μbdt)FeCp*] (bdt = benzene-1,2-dithiolate)8 with their excellent properties. By application of our stepwise ligand exchange route, and with the use of a flexible S3 ligand, we have prepared a series of thioether-dithiolate iron clusters. In this article, the method of successful preparation of the thioether-dithiolate-bridged diiron complex [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt)FeCp*][PF6] (1[PF6]) together with its structure, brief reaction patterns with CO and t BuNC, and one- and two-electron oxidation of [Cp*Fe(μ1κ3SSS′:2κ2SS-tpdt)FeCp*] (1) are described. Moreover, we unexpectedly prepared another four iron complexes: trinuclear iron complex [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt)Fe(μ-2κ2SS:3κ3SSS′tpdt)FeCp*] (5), trinuclear iron complex [Cp*Fe(μ1κ3SSS′:2κ2SS-tpdt)Fe(μ-2κ2SS:3κ3SSS′-tpdt)FeCp*][PF6]2 (5[PF6]2), monoiron complex [Cp*Fe(tpdt)](6), and diiron Received: February 13, 2015

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DOI: 10.1021/acs.organomet.5b00118 Organometallics XXXX, XXX, XXX−XXX

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Organometallics complex [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt)FeCl2] (7). The spectral characterizations and X-ray diffraction analyses of the products have also been described in this paper.

center through the two thiolates (in a κ2SS fashion) and to the other through the two thiolates and thioether sulfur atom (κ3SSS′). This indicates an electron transfer from the thioether sulfur atom of the tpdt ligand to the metal center in order to stabilize the highly electron-deficient diiron core. The short Fe− Fe distance of 2.657(1) Å in the structure of 1+ is clear evidence of an intermetallic bond that falls in the 2.5−2.8 Å range.14 The greater electron deficiency of the diiron core in 1+ (33e species) makes the Fe−Fe distance shorter than any other dithiolatebridged diiron complexes reported by our group, [Cp*Fe(μbdt)FeCp*] (34e species) (2.7803(4) Å)8 and [Cp*Fe(μSEt)3FeCp*] (35e species) (2.7723(8) Å).6b There is a bonding interaction (2.8427(3) Å) between the two Ru atoms in Goh’s thioether-dithiolate complex [Cp*Ru(μ-1κ3SSS′:2κ2SS-tpdt){Cp*RuCl}][PF6]10a and no interaction between the two Ir atoms in [Cp*Ir(μ-1κ3SSS′:2κ2SS-tpdt){Cp*IrCl}][PF6].10d Two Cp* ligands coordinate to each Fe center, and the dihedral angle between the Cp* rings is 62.69(5)°. The nonplanar Fe2S2 core has a dihedral angle of 155.87(2)° along the Fe1−Fe2 single bond. All the Fe−C bond distances (2.031(2)−2.222(5) Å) fall in the normal range for an Fe−C single bond. The Fe−S (2.183(3)−2.233(3) Å) bond lengths are almost equal whether the S atoms are from thiolates or the thioether of the (SCH2CH2)2S group. Reactions of 1[PF6] with CO and tBuNC. In order to understand the reactivity of 1[PF6], we have further carried out a series of reactions and obtained two thiolate-bridged diiron complexes, [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt){Cp*Fe(η1-CO)}][PF6] (2[PF6]) and [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt){Cp*Fe(η1-tBuNC)}][PF6] (3[PF6]) (Scheme 2). These complexes are spectroscopically and crystallographically characterized, and the resulting crystallographic data are presented in Tables S1 and S2.

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RESULTS AND DISCUSSION Synthesis and Characterization of [Cp*Fe(μ1κ3SSS′:2κ2SS-tpdt)FeCp*][PF6] (1[PF6]). The diiron precursor [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt)FeCp*] (1) was prepared in a similar manner to the recently reported triply thiolate-bridged diiron complexes [Cp*Fe(μ-SR)3FeCp*]6b (R = Me, Et, Ph) and bidentate thiolate-bridged diiron complex [Cp*Fe(μbdt)FeCp*].8 As outlined in Scheme 1, treatment of [Cp*FeCl]2 Scheme 1. Synthesis of Complex 1[PF6]a

Reagents and conditions: (i) 1 equiv of Li2(tpdt), THF, −78 to −30 °C; (ii) 1 equiv of Fc·PF6, THF, −30 °C to room temperature, 72%. a

with 1 equiv of Li2(tpdt) in THF from −78 to −30 °C produces a violet solution of complex 1, which is difficult to separate due to its thermodynamic instability. A one-electron oxidation of 1 was then performed with Fc·PF6 (Fc = ferrocene) from −30 °C to room temperature, resulting in an orange-red complex, [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt)FeCp*][PF6] (1[PF6]), in 72% yield. Complex 1[PF6] displays large paramagnetic shifted and very broad 1H NMR signals, which were thus not very informative. The EPR spectrum of a powder sample exhibits a signal at g = 2.046. The ESI-HRMS spectrum of 1[PF6] shows a molecular ion peak with an m/z = 534.0823 (calcd 534.0835) for 1+. Complex 1[PF6] is unambiguously characterized by singlecrystal X-ray diffraction analysis, and its spectral features are fully consistent with its crystal structure. The crystallographic data are presented in Table S1. An ORTEP drawing of 1[PF6] is shown in Figure 1. The most distinctive structural feature of 1+ is that the tpdt ligand binds to the two iron centers in a μ-1κ3SSS′:2κ2SS manner: to one iron

Scheme 2. Reactivity of Complex 1[PF6]

When it was stirred under CO atmosphere from −78 °C to room temperature in CH2Cl2, the orange-red solution of 1[PF6] changed to a green solution, from which the analytically pure complex 2[PF6] was obtained in 88% yield as a green-brown powder. In order to make the S3 atom dissociate from the Fe1 center (see Figure 1), the reaction solution was stirred under an atmosphere of CO for a further, longer time. However, the coordination site occupied by the S3 atom cannot be replaced by another CO molecule even in refluxing THF for 24 h. The IR spectrum (KBr) of 2[PF6] shows a strong band at 1894 cm−1

Figure 1. ORTEP (ellipsoids at 50% probability) diagram of 1[PF6]. All hydrogen atoms and one PF6− anion are omitted for clarity. Selected bond lengths (Å) and angles (deg) for 1[PF6]: Fe1−Fe2 = 2.657(1); Fe1−S1 = 2.206(3); Fe1−S2 = 2.233(3); Fe1−S3 = 2.221(2); Fe2−S1 = 2.193(3); Fe2−S2 = 2.183(3); Fe1−Cp*1 = 1.755(1); Fe2−Cp*2 = 1.750(1); Fe1−S1−Fe2 = 73.84(1); Fe1−S2−Fe2 = 74.51(1); S1− Fe1Fe2−S2 = 155.87(2); Cp*1−Cp*2 = 62.69(5). B

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Organometallics attributed to CO stretching.15 The ESI-HRMS spectrum of 2[PF6] shows a molecular ion peak with an m/z = 562.0780 (calcd 562.0784) for 2+. In the same way, treatment of 1[PF6] with 1 equiv of tBuNC in CH2Cl2 from −78 °C to room temperature produces 3[PF6] in 86% yield as a green-brown powder. The νNC band at 2088 cm−1 is indicative of the terminal end-on coordination mode of the tBuNC ligand. The ESI-HRMS spectrum of 3[PF6] shows a molecular ion peak with an m/z = 617.1558 (calcd 617.1570) for 3+. The tBuNC stretching frequency is 194 cm−1 more than the CO stretching frequency, which is attributed to the stronger σ donor and poorer π acceptor properties of tBuNC than CO.5b They are all characterized by single-crystal X-ray diffraction analysis, and their spectral features are fully consistent with their crystal structures. The ORTEP diagrams of 2[PF6] and 3[PF6] are shown in Figures 2 and 3, respectively. The structure of 3+ resembles that

Figure 3. ORTEP (ellipsoids at 50% probability) diagram of 3[PF6]. All hydrogen atoms and one PF6− anion are omitted for clarity. Selected bond lengths (Å) and angles (deg) for 3[PF6]: Fe1···Fe2 = 3.126(1); Fe1−S1 = 2.239(2); Fe1−S2 = 2.239(2); Fe1−S3 = 2.208(2); Fe2−S1 = 2.288(2); Fe2−S2 = 2.269(2); Fe2−C25 = 1.834(6); N1−C25 = 1.148(8); N1−C26 = 1.470(8); Fe1−Cp*1 = 1.764(8); Fe2−Cp*2 = 1.762(7); Fe1−S1−Fe2 = 87.32(5); Fe1−S2−Fe2 = 87.78(5); Fe2− C25−N1 = 170.52(6); C25−N1−C26 = 177.63(7); S1−Fe1Fe2−S2 = 166.41(8); Cp*1−Cp*2 = 77.79(2).

{Cp* Fe(η1-MeCN)}][PF6]2 (4[PF6]2) (Scheme 2) was obtained in 90% yield as brown-yellow solids, which displayed excellent solubility in CH2Cl2. Complex 4[PF6]2 is spectroscopically and crystallographically characterized, and the resulting crystallographic data are presented in Table S2. The unit cell of 4[PF6]2 contains two crystallographically independent molecules, but they have similar structures (Table S8). The ORTEP drawing of 4[PF6]2 is shown in Figure 4. The two Cp* ligands are also in a mutually cis orientation with the dihedral angle being 74.01(5)°. The nonplanar Fe2S2 core has a dihedral angle of 166.28(2)° along the Fe1−Fe2 single bond (2.766(2) Å).12

Figure 2. ORTEP (ellipsoids at 50% probability) diagram of 2[PF6]. All hydrogen atoms and one PF6− anion are omitted for clarity. Selected bond lengths (Å) and angles (deg) for 2[PF6]: Fe1···Fe2 = 3.106(5); Fe1−S1 = 2.225(6); Fe1−S2 = 2.223(6); Fe1−S3 = 2.212(7); Fe2−S1 = 2.281(6); Fe2−S2 = 2.273(7); Fe2−C25 = 1.751(3); O1−C25 = 1.142(4); Fe1−Cp*1 = 1.755(3); Fe2−Cp*2 = 1.755(3); Fe1−S1−Fe2 = 87.14(2); Fe1−S2−Fe2 = 87.36(2); Fe2−C25−O1 = 170.82(3); S1− Fe1Fe2−S2 = 175.81(3); Cp*1−Cp*2 = 73.37(8).

of 2+. Two Cp* ligands coordinate to the Fe center in a mutually cis orientation, and the dihedral angles between the Cp* rings are 73.37(8)° and 77.79(2)°. The long Fe···Fe distances of 3.106(5) and 3.126(1) Å are indicative of the absence of a bonding interaction between the two Fe atoms,16 which are different from that of complex 1[PF6] (2.657(1) Å). The CO and tBuNC ligand occupy the remaining site of the Fe2 center with a Fe2−C25 distance of 1.751(3) and 1.834(6) Å, Fe2−C25−O1 angle of 170.82(3)°, and Fe2−C25−N1 angle of 170.52(6)°, which are similar to those in our previously reported CO-coordinated complex (1.738(6) Å and 172.35(3)°) and tBuNC-coordinated complex (1.802(4) Å and 172.51(3)°).6b The Fe2−C25 bond in 2[PF6] is considerably shorter than the corresponding bond in 3[PF6], which is probably explained by the steric hindrance in the tBuNC ligand. The C25−O1 bond length of 1.142(4) Å is comparable to that of free CO (1.128 Å). The virtually planar Fe2S2 ring is substantially puckered, with dihedral angles of 175.81(3)° and 166.41(8)° along the Fe1−Fe2 vector. Oxidation of 1[PF6] with Fc·PF6. Complex 1[PF6] can be further oxidized into 1[PF6]2 by Fc·PF6 in THF, while the product 1[PF6]2 was precipitated from the reaction solution. No suitable solvent was found to dissolve 1[PF6]2, as it decomposed readily with the addition of solvents such as CH2Cl2, acetone, and alcohols. However, in the presence of 1.5 equiv of MeCN relative to complex 1[PF6]2, complex [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt)-

Figure 4. ORTEP (ellipsoids at 50% probability) diagram of 4[PF6]2. All hydrogen atoms and two PF6− anions are omitted for clarity. Selected bond lengths (Å) and angles (deg) for 4[PF6]2: Fe1−Fe2 = 2.766(2); Fe1−S1 = 2.189(2); Fe1−S2 = 2.199(2); Fe1−S3 = 2.230(2); Fe2−S1 = 2.227(2); Fe2−S2 = 2.235(2); Fe2−N1 = 1.928(8); N1−C25 = 1.131(10); Fe1−Cp*1 = 1.775(1); Fe2−Cp*2 = 1.792(2); Fe1−S1− Fe2 = 77.56(8); Fe1−S2−Fe2 = 77.17(8); Fe2−N1−C25 = 163.60(8); N1−C25−C26 = 177.90(1); S1−Fe1Fe2−S2 = 166.28(2); Cp*1− Cp*2 = 74.01(5). C

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Organometallics Synthesis and Characterization of [Cp*Fe(μ1κ3SSS′:2κ2SS-tpdt)Fe(μ-2κ2SS:3κ3SSS′-tpdt)FeCp*] (5). The violet THF solution of [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt)FeCp*] (1) at −78 °C was allowed to warm to room temperature and stirred for 2 h, after which time it changed into a blue solution of trinuclear iron complex [Cp*Fe(μ1κ3SSS′:2κ2SS-tpdt)Fe(μ-2κ2SS:3κ3SSS′-tpdt)FeCp*] (5) together with byproduct Cp*2Fe, which can be removed by a small amount of n-hexane (Scheme 3). Complex 5 is paramagnetic at Scheme 3. Synthesis and Reactivity of Complex 5a

Figure 5. ORTEP (ellipsoids at 50% probability) diagram of 5. All hydrogen atoms are omitted for clarity. Selected bond lengths (Å) and angles (deg) for 5: Fe1−Fe2 = 2.930(6); Fe1−S1 = 2.311(1); Fe1−S2 = 2.314(1); Fe1−S3 = 2.208(1); Fe1−Fe2−Fe1A = 163.19(5); Fe2−S1 = 2.318(1); Fe2−S2 = 2.315(1); Fe1−Cp*1 = 1.701(6); Fe1−S1−Fe2 = 78.55(4); Fe1−S2−Fe2 = 78.53(4); S3−Fe1−S1 = 88.95(6); S3−Fe1− S2 = 87.98(6); S3−Fe1−Fe2 = 102.68(4); S1−Fe1Fe2−S2 = 154.70(7); Cp*1−Cp*2 = 75.25(2).

Figure 6. ORTEP (ellipsoids at 50% probability) diagram of 5[PF6]2. All hydrogen atoms and two PF6− anions are omitted for clarity. Selected bond lengths (Å) and angles (deg) for 5[PF6]2: Fe1−Fe3 = 2.657(8); Fe1−S1 = 2.242(1); Fe1−S2 = 2.221(1); Fe1−S3 = 2.235(1); Fe3−S1 = 2.253(1); Fe3−S2 = 2.259(3); Fe3−Fe2 = 2.636(8); Fe2−S4 = 2.239(2); Fe2−S5 = 2.233(2); Fe2−S6 = 2.237(3); Fe3−S4 = 2.279(2); Fe3−S5 = 2.244(2); Fe1−Cp*1 = 1.752(6); Fe2−Cp*2 = 1.757(6); Fe1−S1−Fe3 = 72.47(4); Fe1−S2−Fe3 = 72.74(4); S3−Fe1−S1 = 89.01(5); S3−Fe1−S2 = 88.51(5); S3−Fe1−Fe3 = 100.32(4); Fe1− Fe3−Fe2 = 159.38(3); Fe2−S4−Fe3 = 71.38(4); Fe2−S5−Fe3 = 72.13(4); S6−Fe2−S4 = 88.18(5); S6−Fe2−S5 = 88.63(5); S6−Fe2− Fe3 = 100.84(4); S1−Fe1Fe2−S2 = 161.72(6); S4−Fe2Fe3−S5 = 160.29(6); Cp*1−Cp*2 = 76.70(2).

Reagents and conditions: (i) THF, −30 °C to rt, 92%; (ii) 2 equiv of Fc·PF6, CH2Cl2, rt, 2 h, 93%; (iii) air (1 atm), THF, rt, 1 h, 76%; (iv) 1 equiv of FeCl2, CH2Cl2, rt, 2 h, 95%; (v) 1 equiv of Cp*Fe(tpdt) (6), 3 equiv of NH4·PF6, THF, rt, 2 h, 80%; (vi) 0.5 equiv of FeCl2, 1.5 equiv of NH4·PF6, CH2Cl2, rt, 4 h, 76%. a

room temperature. The EPR spectrum of a powder sample exhibits a signal at g = 2.060. Two-electron oxidation of 5 can be performed with 2 equiv of Fc·PF6, resulting in a brown-yellow solution of complex [Cp*Fe(μ-1 κ 3 SSS′:2 κ 2 SS-tpdt)Fe(μ2κ2SS:3κ3SSS′-tpdt)FeCp*][PF6]2 (5[PF6]2). Complex 5[PF6]2 is also paramagnetic at room temperature. The EPR spectrum of a powder sample exhibits a signal at g = 2.040. The ESI-HRMS spectrum of 5[PF6]2 shows a molecular ion peak with an m/z = 370.9987 (calcd 370.9989) for 52+. Complexes 5 and 5[PF6]2 are unambiguously characterized by single-crystal X-ray diffraction analysis, and their spectral features are fully consistent with their crystal structures. The crystallographic data are presented in Table S3. The ORTEP drawings of 5 and 5[PF6]2 are shown in Figures 5 and 6. The structure of 5 has a C2 axis of symmetry that passes through the central iron atom, which is coordinated to four S atoms of two tpdt ligands with a cis orientation. The two Cp* rings, which are in a mutually cis orientation with a dihedral angle of 75.25(2)°, are coordinated to two different Fe centers and oriented on opposite sides of the tpdt ligands, respectively. The dihedral angle of the butterfly-shaped S1Fe1Fe2S2 is 154.70(7)° along the Fe1−Fe2 single bond (2.930(6) Å),14,16 and the angle of the three iron centers is 163.19(5)°. However, the dihedral angle between the Cp* rings (76.70(2)°) and the dihedral angles of S1Fe1Fe3S2 (161.72(6)°) and S4Fe2Fe3S5 (160.29(6)°) in

the structure of 5[PF6]2 are larger than those of 5. However, the short Fe−Fe distances of 2.657(8) and 2.636(8) Å in the structure of 52+ are much smaller than those of 5, which is clear evidence of an intermetallic bond that falls in the 2.5−2.8 Å range.14 The angle of 159.38(3)° of the three iron centers is smaller than that of 5. In Goh’s complex [Cp*Ru(μ1κ3SSS′:2κ2SS-tpdt)Ru(MeCN)(μ-2κ2SS:3κ3SSS′-tpdt)RuCp*][PF6]2, the presence of two Ru−Ru bonds (Ru1−Ru2 = 2.7857(5) Å and Ru2−Ru3 = 2.8160(6) Å) creates a trimetallic array with a Ru1−Ru2−Ru3 angle equal to 162.54(2)°.10b Synthesis and Characterization of [Cp*Fe(tpdt)] (6). Upon exposure to air at room temperature for 2 h, the blue THF solution of [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt)Fe(μ-2κ2SS:3κ3SSS′tpdt)FeCp*] (5) changed into a green solution, from which the analytically pure complex [Cp*Fe(tpdt)] (6) was obtained in 76% yield as green-brown solids (Scheme 3). Complex 6 is paramagnetic at room temperature; the EPR spectrum of a powder sample exhibits a signal at g = 2.090. The 1H NMR D

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Organometallics spectrum of 6 in CD2Cl2 shows two broad signals at −25.63 and −8.94 ppm attributed to Cp* protons and CH2 protons, respectively, on the basis of their relative intensities. The valence electron count for the iron center (17e) is consistent with the observation of the paramagnetic character of 6 as deduced from its 1H NMR spectral characterization. Complex 6 is unambiguously characterized by single-crystal X-ray diffraction analysis, and its spectral features are fully consistent with its crystal structure. The crystallographlic data are presented in Table S4. The unit cell of 6 contains three crystallographically independent molecules, but they have similar structures (Table S11). An ORTEP drawing of 6 is shown in Figure 7. The mononuclear

Figure 8. ORTEP (ellipsoids at 50% probability) diagram of 7. All hydrogen atoms are omitted for clarity. Selected bond lengths (Å) and angles (deg) for 7: Fe1−Fe2 = 2.772(1); Fe1−S1 = 2.245(2); Fe1−S2 = 2.242(2); Fe2−Cl1 = 2.247(3); Fe1−S3 = 2.227(2); Fe2−S1 = 2.339(2); Fe2−S2 = 2.343(2); Fe2−Cl2 = 2.263(2); Fe1−Cp*1 = 1.752(8); Fe1−S1−Fe2 = 74.40(7); Fe1−S2−Fe2 = 74.36(7); S2− Fe1−S1 = 106.45(8); S3−Fe1−S1 = 88.19(8); S3−Fe1−S2 = 88.64(8); S3−Fe1−Fe2 = 100.92(6); Cl1−Fe2−Cl2 = 114.13(1); S1−Fe1Fe2− S2 = 160.12(9).

and one tpdt ligand, while the Fe2 center bonds to two bridged S atoms of the tpdt ligand and two Cl ligands, exhibiting a distorted [FeS2Cl2] tetrahedral coordination geometry. The nonplanar Fe2S2 core has a dihedral angle of 160.12(9)° along the Fe1−Fe2 single bond [2.772(1) Å].14

Figure 7. ORTEP (ellipsoids at 50% probability) diagram of 6. All hydrogen atoms are omitted for clarity. Selected bond lengths (Å) and angles (deg) for 6: Fe1−S1 = 2.228(2); Fe1−S2 = 2.220(2); Fe1−S3 = 2.241(2); Fe1−Cp*1 = 1.756(9); S1−Fe1−S2 = 102.09(9); S3−Fe1− S1 = 88.60(8); S3−Fe1−S2 = 88.14(9).

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CONCLUSION The goal of this study was to construct the dithiolate-bridged iron sulfur system with the flexible dithiolate-thioether ligand and exploit their reactivity features. This effort led to the preparation of a novel thiolate-bridged dinuclear iron complex bearing a tridentate dithiolate-thioether ligand, [Cp*Fe(μ-1κ3SSS′:2κ2SStpdt)FeCp*][PF6] (1[PF6]). Complex 1[PF6] reacts with CO or tBuNC to give two thiolate-bridged diiron complexes, [Cp*Fe(μ-1 κ 3SSS′:2 κ 2 SS-tpdt){Cp*Fe(η 1 -CO)}][PF 6] (2[PF 6 ]) and [Cp*Fe(μ-1 κ 3 SSS′:2 κ 2 SS-tpdt){Cp*Fe(η 1 - t BuNC)}][PF 6 ] (3[PF 6 ]). Complex [Cp*Fe(μ1κ3SSS′:2κ2SS-tpdt){Cp*Fe(η1-MeCN)}][PF6]2 (4[PF6]2) can be obtained through the reaction of 1[PF6] with Fc·PF6 in THF in the presence of MeCN. Unexpectedly, the trinuclear iron complex [Cp*Fe(μ-1 κ3SSS′:2κ 2SS-tpdt)Fe(μ-2 κ2SS:3κ3SSS′tpdt)FeCp*] (5) has been obtained when a solution of complex [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt)FeCp*] (1) in THF was warmed from −30 °C to room temperature accompanied by byproduct Cp*2Fe. Two-electron oxidation was performed with Fc·PF6, resulting in complex [Cp*Fe(μ-1 κ 3SSS′:2 κ 2SS-tpdt)Fe(μ2κ2SS:3κ3SSS′-tpdt)FeCp*][PF6]2 (5[PF6]2). Exposure of 5 to air in THF gives monoiron complex [Cp*Fe(tpdt)] (6). The diiron complex [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt)FeCl2] (7) has been prepared by the reaction of complex 6 with FeCl2. As an extension of thiolate-bridged diiron complexes in our group, such diiron complexes bearing a tridentate dithiolate-thioether ligand may show some properties in catalytic activation and transformation of small molecules. The study of these potential properties including unique catalysis and biological activities and investigations of monoiron complex 6 toward the synthesis of complexes with other heterometals are now in progress.

iron complex possesses a piano-stool configuration at Fe, with the Cp* ring oriented on opposite sides of the tpdt ligand. The Fe−S (2.220(2)−2.241(2) Å) bond lengths are almost equal irrespective of the S atoms being from thiolates or the thioether of the tpdt group, and all fall in the normal range for an Fe−S single bond. The S1−Fe1−S2 angle is 102.09(9)°, which is much bigger than that in Goh’s [Cp*Ru(tpdt)] (92.23(5)°)10a and [Cp*Ir(tpdt)] (90.80(6)°) complexes.10d Synthesis and Characterization of [Cp*Fe(μ1κ3SSS′:2κ2SS-tpdt)FeCl2] (7). The reaction of [Cp*Fe(tpdt)] (6) with 1 equiv of anhydrous FeCl2 in CH2Cl2 at room temperature for 2 h afforded a blue-green solution of diiron complex [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt)FeCl2] (7) in 95% isolated yield (Scheme 3). However, in the presence of excess NH4·PF6, the reaction of [Cp*Fe(tpdt)] (6) with 0.5 equiv of anhydrous FeCl2 afforded complex 5[PF6]2 in 76% yield (Scheme 3). Complex 5[PF6]2 can also be prepared by the reaction of complex 7 with 1 equiv of complex 6 in the presence of excess NH4·PF6 in 80% yield (Scheme 3). Complex 7 is also paramagnetic at room temperature; the EPR spectrum of a powder sample exhibits a signal at g = 2.046. The 1H NMR spectrum of 7 in CD2Cl2 shows two broad signals at −21.40 and −10.20 ppm attributed to Cp* and CH2 protons, respectively, on the basis of their relative intensities. Complex 7 is unambiguously characterized by single-crystal X-ray diffraction analysis, and its spectral features are fully consistent with its crystal structure. The crystallographlic data are presented in Table S4. The unit cell of 7 contains two crystallographically independent molecules, but they have similar structures (Table S12). An ORTEP drawing of 7 is shown in Figure 8. The Fe1 center is coordinated by one Cp* E

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residue was washed with n-hexane (10 mL × 2) to obtain a brown crystalline powder, [Cp*Fe(μ-1 κ 3 SSS′:2 κ 2 SS-tpdt){Cp*Fe(η1-tBuNC)}][PF6] (3[PF6], 366 mg, 0.48 mmol, 86%). Crystals suitable for X-ray diffraction were obtained from a THF solution layered with n-hexane at room temperature. ESI-HRMS: calcd for 3+ 617.1570; found 617.1558. Anal. Calcd for C29H47F6Fe2NPS3: C, 45.68; H, 6.21; N, 1.84. Found: C, 45.59; H, 6.28; N, 1.75. IR (KBr, cm−1): 2088(νNC). Preparation of [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt)FeCp*][PF6]2 (1[PF6]2). Complex [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt)FeCp*][PF6] (1[PF6], 380 mg, 0.56 mmol) can be further oxidized by Fc·PF6 (186 mg, 0.56 mmol) in THF (50 mL) at room temperature into complex [Cp*Fe(μ1κ3SSS′:2κ2SS-tpdt)FeCp*][PF6]2 (1[PF6]2, 444 mg, 0.54 mmol, 96%). The product was precipitated from THF, after decanting the supernatant, and the brownish-green residue was evaporated to dryness under reduced pressure. Anal. Calcd for C24H38F12Fe2P2S3: C, 34.97; H, 4.65. Found: C, 35.02; H, 4.73. Preparation of [Cp*Fe(μ-1 κ 3 SSS′:2 κ 2 SS-tpdt){Cp*Fe(η 1 MeCN)}][PF6]2 (4[PF6]2). In the presence of MeCN (1.5 equiv to 1[PF6]2), complex [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt)FeCp*][PF6]2 (1[PF6]2, 444 mg, 0.54 mmol) turns into [Cp*Fe(μ-1κ3SSS′:2κ2SStpdt){Cp*Fe(η1-MeCN)}][PF6]2 (4[PF6]2, 420 mg, 0.48 mmol, 90%) in THF (30 mL) at room temperature. The product was also precipitated from THF, and after decanting the supernatant, the yellow residue was evaporated to dryness under reduced pressure. Crystals suitable for X-ray diffraction were obtained from a CH2Cl2 solution layered with n-hexane at room temperature. Anal. Calcd for C26H41F12Fe2NP2S3: C, 36.08; H, 4.78; N, 1.62. Found: C, 35.99; H, 4.85; N, 1.53. Preparation of [Cp*Fe(μ-1 κ 3 SSS′:2 κ 2 SS-tpdt)Fe(μ2κ2SS:3κ3SSS′-tpdt)FeCp*] (5). As previously mentioned, to a stirred suspension of Cp*Li (2.14 g, 15 mmol) in THF (80 mL) was added anhydrous FeCl2 (1.90 g, 15 mmol), and the mixture was stirred at 0 °C for 1 h. The resulting olive-green [Cp*FeCl]2 solution was cooled to −78 °C. Then, a suspension of Li2(tpdt) in THF (50 mL), prepared by the reaction of nBuLi (6.80 mL, 2.2 M solution in n-hexane, 15 mmol) and S(CH2CH2SH)2 (1.17 g, 7.5 mmol) at 0 °C, was transferred via a cannula to the cooled solution of [Cp*FeCl]2. The mixture was placed in a −78 °C bath for 1 h and stirred as it warmed to −30 °C, resulting in a violet solution. When the violet solution of thermodynamically unstable complex [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt)FeCp*] (1) prepared freshly was warmed to room temperature and stirred at room temperature for 2 h, a blue solution was obtained. All volatiles were removed under vacuum, and the residue was washed with n-hexane (20 mL) to remove the byproduct FeCp*2, extracted with CH2Cl2 (150 mL), and then dried in vacuo. The product, [Cp*Fe(μ-1 κ 3 SSS′:2 κ 2 SS-tpdt)Fe(μ2κ2SS:3κ3SSS′-tpdt)FeCp*] (5, 2.56 g, 3.4 mmol, 92%), was obtained as a blue powder. n-Hexane was used to extract the product, after being concentrated and refrigerated to −30 °C; then the black needle crystals were isolated. EPR: g = 2.060. Anal. Calcd for C28H46F12Fe3P2S6: C, 32.43; H, 4.64. Found: C, 32.42; H, 4.73. Preparation of [Cp*Fe(tpdt)] (6). The blue THF (200 mL) solution of [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt)Fe(μ-2κ2SS:3κ3SSS′-tpdt)FeCp*] (5, 3.70 g, 5.0 mmol) was exposed to air for 2 h, resulting in a green solution with a light yellow insoluble substance. All volatiles were removed under vacuum, and the residue was extracted with n-hexane (250 mL). After being cooled to −30 °C for 2 days, the black needle crystals of [Cp*Fe(tpdt)] (6, 2.60 g, 7.6 mmol, 76%) were isolated. EPR: g = 2.090. 1H NMR (400 MHz, CD2Cl2, ppm): δ −8.94 (br, tpdtH), −25.63 (br, Cp*-CH3). Anal. Calcd for C14H23FeS3: C, 49.43; H, 6.64. Found: C, 49.37; H, 6.72. Preparation of [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt)FeCl2] (7). To a stirred suspension of [Cp*Fe(tpdt)] (6, 1.00 g, 3.0 mmol) in CH2Cl2 (100 mL) was added anhydrous FeCl2 (0.39 g, 3.0 mmol), and the mixture was stirred at room temperature for 2 h, after which time nhexane (200 mL) was added to the resulting blue-green solution with vigorous stirring, resulting in the precipitation of a black crystal powder. After decanting the supernatant, the powder was evaporated to dryness under reduced pressure. Crystals suitable for X-ray diffraction were obtained from a CH2Cl2 solution layered with n-hexane at room

EXPERIMENTAL SECTION

General Procedures. All manipulations were routinely carried out under an argon atmosphere, using standard Schlenk techniques. All solvents were dried and distilled over an appropriate drying agent under argon. Pentamethylcyclopentadiene (Cp*H)17 was prepared according to literature procedures. Anhydrous FeCl2 (Aldrich), tBuNC (Aldrich), and S(CH2CH2SH)2 (Aldrich) were used as received. Infrared spectra were recorded on a NEXVS FT-IR spectrometer. Elemental analyses were performed on a Vario EL analyzer. The 1H NMR spectra were recorded on a Brüker 400 Ultra Shield spectrometer. ESI-HRMS were recorded on a HPLC/Q-Tof Micro spectrometer. The EPR spectrum was recorded at room temperature on a Brüker EMX-6/1 EPR spectrometer. X-ray Crystallography Procedures. The data were obtained on a Brüker SMART APEX CCD diffractometer with graphite-monochromated Mo Kα radiation (λ = 0.710 73 Å). Empirical absorption corrections were performed using the SADABS program.18 Structures were solved by direct methods and refined by full-matrix least-squares based on all data using F2 with SHELX97.19 All of the non-hydrogen atoms were refined anisotropically. All of the hydrogen atoms were generated and refined in ideal positions. One Cp* ligand in 1[PF6], one tpdt ligand, one PF6 anion, and one C2H4Cl2 solvent in 5[PF6]2 were disordered and restrained during refinement of the structure. Disordered atomic positions were split and refined using one occupancy parameter per disordered group. We used SQUEEZE to help us solve the level B alert of solvent accessible voids in crystal 4[PF6]2 on checking the cif file through CheckCIF (http://checkcif.iucr.org). Crystal data and collection details for 1[PF6], 2[PF6], 3[PF6], and 4[PF6]2 are given in Tables S1 and S2; crystal data and collection details for 5, 5[PF6]2, 6, and 7 are given in Tables S3 and S4. Preparation of [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt)FeCp*][PF6] (1[PF6]). To a stirred suspension of Cp*Li (2.14 g, 15 mmol) in THF (80 mL) was added anhydrous FeCl2 (1.90 g, 15 mmol), and the mixture was stirred at 0 °C for 1 h. The resulting olive-green [Cp*FeCl]2 solution was cooled to −78 °C. Then, a suspension of Li2(tpdt) in THF (50 mL), prepared by the reaction of nBuLi (6.80 mL, 2.2 M solution in n-hexane, 15 mmol) and S(CH2CH2SH)2 (1.17 g, 7.5 mmol) at 0 °C, was transferred via a cannula to the cooled solution of [Cp*FeCl]2. The mixture was placed in a −78 °C bath for 1 h and stirred as it warmed to −30 °C, resulting in a violet solution. Fc·PF6 (2.11 g, 6.4 mmol) was added to the violet solution of [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt)FeCp*] (1) with vigorous stirring at −30 °C to room temperature. All volatiles were removed under vacuum, and the residue was washed with n-hexane (50 mL) to remove the FeCp*2, extracted with CH2Cl2 (150 mL), and then dried in vacuo. The product, [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt)FeCp*][PF6] (1[PF6], 3.67 g, 5.4 mmol, 72%), was obtained as an orange-red powder. Crystals suitable for X-ray diffraction were obtained from a THF solution layered with n-hexane at room temperature. EPR: g = 2.046. ESI-HRMS: calcd for 1+ 534.0835; found 534.0823. Anal. Calcd for C24H38F6Fe2PS3: C, 42.43; H, 5.64. Found: C, 42.50; H, 5.72. Preparation of [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt){Cp*Fe(η1-CO)}][PF6] (2[PF6]). When it was stirred under a CO atmosphere at −78 °C to room temperature in CH2Cl2 (50 mL), the orange-red solution of [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt)FeCp*][PF6] (1[PF6], 680 mg, 1.01 mmol) smoothly changed to a green solution. After removal of the volatiles under reduced pressure, the brownish-green residue was washed with n-hexane (15 mL × 2) to afford crystalline solids of [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt){Cp*Fe(η1-CO)}][PF6] (2[PF6], 622 mg, 0.88 mmol, 88%). Crystals suitable for X-ray diffraction were obtained from a THF solution layered with n-hexane at room temperature. ESI-HRMS: calcd for 2+ 562.0784; found 562.0780. Anal. Calcd for C25H38F6Fe2OPS3: C, 42.39; H, 5.55. Found: C, 42.32; H, 5.64. IR (KBr, cm−1): 1894(νCO). Preparation of [Cp*Fe(μ-1 κ 3 SSS′:2 κ 2 SS-tpdt){ Cp*Fe(η1-tBuNC)}][PF6] (3[PF6]). To a stirred solution of [Cp*Fe(μ1κ3SSS′:2κ2SS-tpdt)FeCp*][PF6] (1[PF6], 380 mg, 0.56 mmol) in CH2Cl2 (50 mL) was added dropwise tBuNC (88 μL, 0.68 mmol) at −78 °C via a microsyringe, followed by stirring for 2 h as the mixture warmed to room temperature. The resulting brownish-green solution was evaporated to dryness under reduced pressure. The brownish-green F

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Organometallics temperature. The product, [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt)FeCl2] (7, 1.34 g, 2.80 mmol, 95%), was obtained as block crystals. EPR: g = 2.046. 1 H NMR (400 MHz, CD2Cl2, ppm): δ −10.20 (br, tpdt-H), −21.40 (br, Cp*-CH3). Anal. Calcd for C14H23Cl2Fe2S3: C, 34.64; H, 5.24. Found: C, 34.71; H, 5.32. Preparation of [Cp*Fe(μ-1 κ 3 SSS′:2 κ 2 SS-tpdt)Fe(μ2κ2SS:3κ3SSS′-tpdt)FeCp*][PF6]2 (5[PF6]2). Method a: To the blue solution of [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt)Fe(μ-2κ2SS:3κ3SSS′-tpdt)FeCp*] (5, 742 mg, 1 mmol) in CH2Cl2 (40 mL) was added Fc·PF6 (662 mg, 2 mmol) with vigorous stirring at room temperature, resulting in a brown-yellow solution. All volatiles were removed under vacuum, and the residue was washed with n-hexane (20 mL) to remove the FeCp*2, extracted with CH2Cl2 (40 mL), and then dried in vacuo. The product, [Cp*Fe(μ-1κ 3SSS′:2κ2 SS-tpdt)Fe(μ-2 κ2 SS:3κ 3SSS′-tpdt)FeCp*][PF6]2 (5[PF6]2, 960 mg, 0.93 mmol, 93%), was obtained as a brown-yellow powder. Crystals suitable for X-ray diffraction were obtained from a CH2Cl2 solution layered with n-hexane at room temperature. Method b: To the green solution of [Cp*Fe(tpdt)] (6, 686 mg, 2 mmol) in CH2Cl2 (40 mL) was added anhydrous FeCl2 (125 mg, 1 mmol) with vigorous stirring for 1 h at room temperature, after which NH4PF6 (490 mg, 3 mmol) was added. The reaction mixture was stirred for 2 h, resulting in a brown-yellow solution. The solution was evaporated to dryness under reduced pressure. The residue was washed with n-hexane and extracted with CH2Cl2 (40 mL). A brown-yellow powder of [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt)Fe(μ-2κ2SS:3κ3SSS′-tpdt)FeCp*][PF6]2 (5[PF6]2, 780 mg, 0.76 mmol, 76%) was obtained after the volatiles were removed in vacuo. Method c: To the blue-green solution of [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt)FeCl2] (7, 470 mg, 1 mmol) in CH2Cl2 (50 mL) were added complex 6 (340 mg, 1 mmol) and NH4PF6 (490 mg, 3 mmol) with vigorous stirring for 2 h at room temperature, resulting in a brown-yellow solution. The solution was evaporated to dryness under reduced pressure. The residue was washed with n-hexane and extracted with CH2Cl2 (50 mL). A brown-yellow powder of [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt)Fe(μ-2κ2SS:3κ3SSS′-tpdt)FeCp*][PF6]2 (5[PF6]2, 826 mg, 0.8 mmol, 80%) was obtained after the volatiles were removed in vacuo. EPR: g = 2.040. ESI-HRMS: calcd for 52+ 370.9987; found 370.9989. Anal. Calcd for C28H46F12Fe3P2S6: C, 32.43; H, 4.64. Found: C, 32.38; H, 4.71.

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(c) Vela, J.; Stoain, S.; Flaschenriem, C. J.; Münck, E.; Holland, P. L. J. Am. Chem. Soc. 2004, 126, 4522−4533. (3) Hydrogenase model: (a) Tard, C.; Pickett, C. J. Chem. Rev. 2009, 109, 2245−2274. (b) Gloaguen, F.; Rauchfuss, T. B. Chem. Soc. Rev. 2009, 38, 100−108. (c) Simmons, T. R.; Berggren, G.; Bacchi, M.; Fontecave, M.; Artero, V. Coord. Chem. Rev. 2014, 270−271, 127−150. (4) Hogarth, G.; Kabir, S. E.; Richards, I. Organometallics 2010, 29, 6559−6568. (5) (a) Hsu, S. C. N.; Zheng, Y.-C.; Chen, H.-Y.; Hung, M.-Y.; Kuo, T.S. J. Organomet. Chem. 2008, 693, 3035−3042. (b) Lin, P.; Chen, H.; Chen, P.; Chiang, M.; Chiang, M. Y.; Kuo, T.; Hsu, S. C. N. Inorg. Chem. 2011, 50, 10825−10834. (6) (a) Chen, Y.; Zhou, Y.; Chen, P.; Tao, Y.; Li, Y.; Qu, J. J. Am. Chem. Soc. 2008, 130, 15250−15251. (b) Chen, Y.; Zhou, Y.; Qu, J. Organometallics 2008, 27, 666−671. (7) (a) Chen, Y.; Peng, Y.; Zhao, J.; Chen, P.; Liu, L.; Li, Y.; Chen, S.; Qu, J. Dalton. Trans. 2010, 39, 3020−3025. (b) Chen, P.; Peng, Y.; Jia, C.; Qu, J. Eur. J. Inorg. Chem. 2010, 33, 5239−5246. (c) Chen, Y.; Liu, L.; Peng, Y.; Chen, P.; Luo, Y.; Qu, J. J. Am. Chem. Soc. 2011, 133, 1147− 1149. (8) Li, Y.; Li, Y.; Wang, B.; Luo, Y.; Yang, D.; Tong, P.; Zhao, J.; Luo, L.; Zhou, Y.; Chen, S.; Cheng, F.; Qu, J. Nat. Chem. 2013, 5, 320−326. (9) (a) Kaasjager, V. E.; Henderson, R. K.; Bouwman, E.; Lutz, M.; Spek, A. L.; Reedijk, J. Angew. Chem., Int. Ed. 1998, 37, 1668−1670. (b) Chiang, C.; Miller, M. L.; Reibenspies, J. H.; Darensbourg, M. Y. J. Am. Chem. Soc. 2004, 126, 10867−10874. (10) (a) Goh, L. Y.; Teo, M. E.; Khoo, S. B.; Leong, W. K.; Vittal, J. J. J. Organomet. Chem. 2002, 664, 161−169. (b) Shin, R. Y. C.; Ng, S. Y.; Tan, G. K.; Koh, L. L.; Khoo, S. B.; Goh, L. Y. Organometallics 2004, 23, 547−558. (c) Shin, R. Y. C.; Goh, L. Y. Acc. Chem. Res. 2006, 39, 301− 313. (d) Xu, C.; Li, Y.; Goh, L. Y.; Pullarkat, S. A. J. Organomet. Chem. 2012, 696, 4207−4214. (11) Kim, J.-H.; Hwang, J.-W.; Park, Y.-W.; Do, Y. Inorg. Chem. 1999, 38, 353−357. (12) (a) Barclay, G. A.; McPartlin, E. M.; Stephenson, N. C. Inorg. Nucl. Chem. Lett. 1967, 3, 397−402. (b) Barclay, G. A.; McPartlin, E. M.; Stephenson, N. C. Aust. J. Chem. 1968, 21, 2669−2674. (13) (a) Tanino, S.; Li, Z.; Ohki, Y.; Tatsumi, K. Inorg. Chem. 2009, 48, 2358−2360. (b) Perra, A.; Wang, Q.; Blake, A. J.; Davies, E. S.; McMaster, J.; Wilson, C.; Schröder, M. Dalton Trans. 2009, 925−931. (c) Liaw, W.-F.; Chiang, C.-Y.; Lee, G.-H.; Peng, S.-M.; Lai, C.-H.; Darensbourg, M. Y. Inorg. Chem. 2000, 39, 480−484. (d) Ohki, Y.; Tatsumi, K. Eur. J. Inorg. Chem. 2011, 7, 973−985. (14) Frisch, P. D.; Lioyd, M. K.; Mccleverty, J. A.; Seddon, D. J. Chem. Soc., Dalton Trans. 1973, 2268−2272. (15) Dev, S.; Mizobe, Y.; Hidai, M. Inorg. Chem. 1990, 29, 4797−4801. (16) (a) Vergamini, P. J.; Kubas, G. J. Prog. Inorg. Chem. 1976, 21, 261− 282. (b) Paul, M. T.; Richard, A. C.; Crane, R. M.; Kathleen, R. B.; Douglas, P. J. Organomet. Chem. 1991, 402, 233−248. (c) Liaw, W.-F.; Tsai, W.-T.; Gau, H.-B.; Lee, C.-M.; Chou, S.-Y.; Chen, W.-Y.; Lee, G.H. Inorg. Chem. 2003, 42, 2783−2788. (d) Song, L.-C.; Cheng, J.; Hu, Q.-M.; Gong, F.-H.; Bian, H.-Z.; Wang, L.-X. Organometallics 2005, 24, 472−474. (17) Fendrick, C. M.; Schertz, L. D.; Mintz, E. A.; Marks, T. J.; Bitterwolf, T. E.; Horine, P. A.; Hubler, T. L.; Sheldon, J. A.; Belin, D. D. Inorg. Synth. 1992, 29, 193−198. (18) Sheldrick, G. M. SADABS, Program for Area Detector Adsorption Correction; Institute for Inorganic Chemistry, University of Göttingen: Germany, 1996. (19) (a) Sheldrick, G. M. SHELXL97, Program for Refinement of Crystal Structures; University of Göttingen: Germany, 1997. (b) Sheldrick, G. M. SHELXS97, Program for Solution of Crystal Structures; University of Göttingen: Germany, 1997.

ASSOCIATED CONTENT

S Supporting Information *

Characterization, structure, and spectroscopic data (CIF). This material is available free of charge via the Internet at http://pubs. acs.org.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China (No. 21231003), the Program for Changjiang Scholars and Innovative Research Team in University (No. IRT13008), and the “111” Project of the Ministry of Education of China.

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REFERENCES

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DOI: 10.1021/acs.organomet.5b00118 Organometallics XXXX, XXX, XXX−XXX