Palladium-Catalyzed Reactions of [Et3NH]+ Salts of [(Î¼-RS)(Î¼-CO

Article pubs.acs.org/Organometallics

Palladium-Catalyzed Reactions of [Et3NH]+ Salts of [(μ-RS)(μCO)Fe2(CO)6]− Anions with Iodo-Aromatic Compounds To Give the Corresponding Butterfly μ‑Acyl Fe/S Cluster Complexes Li-Cheng Song,* Hao Tan, An-Guo Zhu, Yuan-Yuan Hu, and Hao Chen Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Nankai University, Tianjin 300071, People’s Republic of China S Supporting Information *

ABSTRACT: Interestingly, the intermediate salts A·[Et3NH] (A = (μ-RS)(μ-CO)Fe2(CO)6; R = i-Pr, sec-Bu, cy-C6H11, pMeC6H4) prepared from Fe3(CO)12, RSH, and Et3N were found to react in situ with iodobenzene or its substituted derivatives in the presence of the catalyst precursor Pd(PPh3)4 to give the benzoyl type μ-acyl complexes (μ-RS)(μ-ArCO)Fe2(CO)6 (Ar = phenyl or substituted phenyl), whereas the in situ reactions of A·[Et3NH] with iodo-substituted aromatic heterocycles under the same conditions afforded the corresponding heterocyclic type μ-acyl complexes (μ-RS)(μ-ArCO)Fe2(CO)6 (Ar = heterocyclic or benzoheterocyclic group). Particularly worth noting is that such Pd-catalyzed C−C bond cross-coupling reactions are the first examples of catalytic reactions regarding A·[Et3NH] salts reported so far. In addition, all the prepared new μ-acyl complexes and the three new intermediate salts A·[Et3NH] (R = i-Pr, sec-Bu, cy-C6H11) were isolated and structurally characterized, while a possible pathway for such type Pd-catalyzed reactions regarding A·[Et3NH] salts is suggested.

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INTRODUCTION

To develop the novel catalytic type reactions regarding A· [Et3NH] salts and particularly enlightened by the well-known C−C bond cross-coupling reactions catalyzed by Pd complexes,35−38 we decided to carry out reactions of the in situ prepared A·[Et3NH] with iodobenzene and its substituted derivatives in the presence of Pd(PPh3)4 to see if a phenyl group or a substituted phenyl group could couple with a CO ligand present in anions A to afford the corresponding butterfly μ-acyl complexes. Interestingly, such C−C bond cross-coupling reactions indeed occurred and resulted in the formation of a series of benzoyl type μ-acyl complexes with a general formula of (μ-RS)(μ-ArCO)Fe2(CO)6 (Ar denotes a phenyl group or a substituted phenyl group). Furthermore, in order to examine the generality of such Pd-catalyzed C−C bond cross-coupling reactions, we also carried out reactions of A·[Et3NH] with various iodo-aromatic heterocycles. As a result, the corresponding heterocyclic type μ-acyl complexes with the general formula (μ-RS)(μ-ArCO)Fe2(CO)6 (Ar denotes a heterocyclic group in aromatic heterocycles) were also produced. In this article, we report the novel Pd-catalyzed C−C bond cross-coupling reactions of anions A with the iodo-substituted benzenoid hydrocarbons or aromatic heterocycles, resulting in a series of benzoyl or heterocyclic type μ-acyl complexes. In addition, all of the newly prepared μ-acyl complexes and the three isolated

The butterfly Fe/S cluster complexes have received ever more attention in recent years, largely because of their unique structures and novel properties1−16 and particularly their important applications as biomimetic models for the active site of [FeFe]-hydrogenases.17−25 Among such butterfly complexes, the [Et3NH]+ salts of the μ-CO ligand containing anions [(μ-RS)(μ-CO)Fe2(CO)6]− (A) are of great interest in view of their easy preparation, high chemical reactivity, and widespread use in organic and organometallic synthesis.26−34 Since Seyferth and co-workers prepared the first intermediate salts A·[Et3NH] by reactions of Fe3(CO)12 with mercaptans RSH in the presence of Et3N (Scheme 1) in 1985,12 a wide variety of in situ reactions of such type complex salts has been reported to give various interesting organometallic compounds. However, it should be noted that all the previously reported reactions regarding A·[Et3NH] salts are stoichiometric; none of them are catalytic.26−34 Scheme 1

Received: March 19, 2015 Published: April 28, 2015 © 2015 American Chemical Society

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DOI: 10.1021/acs.organomet.5b00228 Organometallics 2015, 34, 1730−1741

Article

Organometallics new intermediate salts A·[Et3NH] (R = i-Pr, sec-Bu, cy-C6H11) are also described in this article.

Scheme 3

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RESULTS AND DISCUSSION Pd-Catalyzed in Situ Reactions of A·[Et3NH] with Iodobenzene and Its Substituted Derivatives Leading to Benzoyl Type μ-Acyl Complexes. Previously, Seyferth and co-workers reported that the butterfly μ-acyl Fe/S cluster complexes with a general formula of (μ-RS)(μ-R′CO)Fe2(CO)6 can be prepared by stoichiometric reactions of the in situ prepared [Et3NH]+ salts of anions A with acid chlorides RCOCl39 or organomercuric halides R′HgX.40 However, as mentioned above, we have recently found that the butterfly μacyl complexes can be also prepared by Pd-catalyzed reactions of the in situ prepared A·[Et3NH] salts with iodo-substituted aromatic compounds. Particularly noteworthy is that such Pdcatalyzed C−C bond cross-coupling reactions are the first examples of catalytic reactions regarding A·[Et3NH] salts, which are not only more atom economical but also more environmentally friendly than the previously reported stoichiometric reactions with RCOCl and R′HgX, which release either toxic CO gas or liquid Hg.39,40 At the beginning of this study, we first carried out the Pdcatalyzed reaction of the in situ prepared A·[Et3NH] (R = i-Pr) with iodobenzene under different conditions in order to optimize the yield of the μ-acyl complex (μ-i-PrS)(μ-PhCO)Fe2(CO)6 (1) (Scheme 2, Table 1). As shown in Table 1,

While complex 1 is known,43 complexes 2−10 are new and have been characterized by elemental analysis and various spectroscopic techniques. The IR spectra of 1−10, similar to those of the previously reported similar complexes,40b,44 showed three or four absorption bands in the range 2075− 1963 cm−1 for their terminal CO ligands and one band in the region 1479−1451 cm−1 for their μ-acyl ligands. The 1H and 13 C{1H} NMR spectra proved that such butterfly complexes might exist as two isomers of a-R and e-R in terms of their substituents R being attached to their bridging S atoms by an axial bond or an equatorial bond (Scheme 4).40b,45 For Scheme 4

Scheme 2 example, complex 10 was proved to exist as two isomers: namely, a-p-MeC6H4 and e-p-MeC6H4. In the 1H NMR spectrum of 10, the a-p-MeC6H4 isomer showed a singlet at 2.19 ppm for the methyl H atoms in its substituent a-pMeC6H4, whereas the e-p-MeC6H4 isomer displayed a singlet at 2.29 ppm for the methyl H atoms in its substituent e-pMeC6H4. Furthermore, in the 13C{1H} NMR spectrum of 10, the a-p-MeC6H4 isomer displayed a singlet at 289.9 ppm for its μ-acyl C atom, while the e-p-MeC6H4 isomer exhibited a singlet at 293.1 ppm for its μ-acyl C atom. The molecular structures of complexes 2, 7, and 10 were further confirmed by X-ray diffraction analysis. While their ORTEP plots are depicted in Figures 1−3, Table 2 gives their selected bond lengths and angles. As can be seen in Figures

Table 1. Optimization of Conditions for the Pd-Catalyzed Reactions of A·[Et3NH] (R = i-Pr) with PhI entry

Pd(PPh3)4 (mmol %)

temp (°C)

time (h)

PhI (equiv)

yield (%)

1 2 3 4 5

2.5 2.5 2.5 5 5

25 25 55 55 reflux

2 24 1.5 1.5 1.5

1 1 1 1.5 1.5

trace 26 44 58 38

under the conditions in entry 4, complex 1 was obtained with the highest yield (58%), whereas under the conditions in entries 1−3 and 5, the yields of complex 1 are lower (from 44% to trace). In addition, it is worth noting that no complex 1 was produced when the reactions were carried out under the conditions in entry 4 but without adding Pd(PPh3)4. After optimization of the reaction conditions, we continued to carry out the in situ reactions of A·[Et3NH] (R = i-Pr, sec-Bu, cy-C6H11, p-MeC6H4) with iodobenzene and its substituted derivatives by using the optimized conditions shown in Table 1, entry 4. Thus, as shown in Scheme 3, when the THF solutions of A·[Et3NH] salts were treated in situ with a slight excess of iodobenzene or its substituted derivatives, the desired μ-acyl complexes (μ-RS)(μ-ArCO)Fe2(CO)6 (2−10) were obtained in 37−60% yields, along with small amounts of byproducts (μRS)2Fe2(CO)6 (R = i-Pr, sec-Bu, cy-C6H11, p-MeC6H4)41,42 generated from decomposition of A·[Et3NH] salts during the reactions.40

Figure 1. ORTEP view of 2 with 10% probability level ellipsoids. 1731


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of the corresponding byproducts (μ-RS)2Fe2(CO)6 (Scheme 5). Complexes 11−20 are also new and have been characterized by elemental analysis and various spectroscopic methods. For example, the IR spectra of 11−20 displayed three or four absorption bands in the region 2074−1961 cm−1 for their terminal carbonyls and one absorption band in the range 1492−1465 cm−1 for their μ-acyl ligands.40b,44 The 1H NMR spectrum of 16, similarly to that of the benzoyl type complex 10, showed one singlet at 1.99 ppm for methyl H atoms in its ap-MeC6H4 isomer and one singlet at 2.27 ppm for the methyl H atoms in its e-p-MeC6H4 isomer, respectively. In addition, the 13C{1H} NMR spectrum of 16 exhibited two singlets at 282.1 and 288.4 ppm for μ-acyl C atoms in its a-isomer and eisomer, respectively. The molecular structures of complexes 14, 15, 17, and 20 were unequivocally confirmed by X-ray diffraction analysis. Their ORTEP plots are shown in Figures 4−7, whereas Table 3 gives their selected bond lengths and angles. Similar to the case for the benzoyl type μ-acyl complexes 2, 7, and 10, the four heterocyclic type μ-acyl complexes each have a butterfly cluster core that consists of a thiolate ligand, a heterocyclic type of μacyl ligand, and two Fe(CO)3 units. The μ-CO bond lengths (1.261−1.265 Å) and Fe−Fe bond lengths (2.5429−2.5545 Å) are respectively very close to those of 2, 7, 10, and the previously reported diiron μ-acyl complexes.46 In addition, Figures 4−7 show that the i-Pr, sec-Bu, and cy-C6H11 groups in these four complexes are all bound to their bridged S atoms by an equatorial type of bond.40b,45 Isolation and Characterization of New Intermediate Salts A·[Et3NH] (R = i-Pr, sec-Bu, cy-C6H11). Among the intermediate complex salts A·[Et3NH] prepared so far, only two of them (R = 2,4,6-Me3C6H2, p-MeC6H4) have been previously isolated and structurally characterized.39,47 To confirm the structures of the three new intermediate salts (R = i-Pr, sec-Bu, cy-C6H11), we decided to isolate them from their THF solutions. Fortunately, the three new complex salts could be successfully isolated as air-sensitive red solids in 60−70% yields and were fully characterized by elemental analysis, spectroscopy, and X-ray crystallography. The IR spectra of these three salts, similar to that of their analogue A·[Et3NH] (R = p-MeC6H4),47 showed three to four absorption bands in the range 2077−1969 cm−1 for their terminal carbonyls and one absorption band in the region 1739−1728 cm−1 for their bridging μ-CO ligands. In addition, the 1H NMR spectra each displayed a broad singlet in the region 8.83−8.90 ppm for NH groups in their [Et3NH]+ cations, while their 13C{1H} NMR spectra showed one singlet at 217.8 ppm for C atoms in their bridging μ-CO ligands. The X-ray crystallographic study on the three new complex salts (Figures 8−10 and Table 4) revealed that they are isostructural with the previously reported A· [Et3NH] (R = 2,4,6-Me3C6H2, p-MeC6H4,).39,47 They all contain the anionic butterfly cluster [(μ-RS)(μ-CO)Fe2(CO)6]− and the cation [Et3NH]+. The bridging CO bond lengths (1.199−1.208 Å) for the three new complexes are nearly the same as those of the previously reported A·[Et3NH] (R = 2,4,6-Me3C6H2, 1.208 Å; R = p-MeC6H4, 1.203 Å),39,47 whereas the Fe−Fe bond lengths (2.5280−2.5461 Å) are slightly longer than those of A·[Et3NH] (R = 2,4,6-Me3C6H2, 2.494 Å; R = p-MeC6H4, 2.5223 Å).39,47 In addition, as can be clearly seen in Figures 8−10, the groups i-Pr, sec-Bu, and cyC6H11 in the three complex salts are bound to their bridged S atoms by an equatorial type of bond, while the corresponding

Figure 2. ORTEP view of 7 with 30% probability level ellipsoids.


1−3, the three complexes each contain an organic thiolate ligand and a benzoyl type of μ-acyl ligand that bridge between two Fe(CO)3 units to form a butterfly cluster core. The μ-C O bond lengths (1.250−1.261 Å) and Fe−Fe bond lengths (2.5311−2.5668 Å) are respectively very close to those of the previously reported diiron μ-acyl complexes.46 In addition, as can be clearly seen in Figures 1−3, both of the i-Pr groups in 2 and 7 are attached to their bridging S atoms by an equatorial bond, whereas the p-MeC6H4 group in 10 is bound to its bridging S atom by an axial bond.40b,45 Pd-Catalyzed in Situ Reactions of A·[Et3NH] with IodoSubstituted Aromatic Heterocycles Leading to Heterocyclic Type μ-Acyl Complexes. In order to show the generality of the Pd-catalyzed reactions of A·[Et3NH] salts with iodo-aromatic compounds, we further carried out the in situ reactions of A·[Et3NH] with iodo-substituted aromatic heterocycles. When the THF solutions of the [Et3NH]+ salts of anions A (R = i-Pr, sec-Bu, cy-C6H11, p-MeC6H4) were treated with the iodo-substituted heterocycles ArI under the aforementioned optimized conditions, the expected heterocyclic type μ-acyl complexes (μ-RS)(μ-ArCO)Fe2(CO)6 (11−20) were produced in 35−53% yields, together with small amounts 1732


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Organometallics Table 2. Selected Bond Lengths (Å) and Angles (deg) for 2, 7, and 10 Complex 2 Fe(1)−S(1) Fe(2)−O(7) O(7)−C(7) C(7)−Fe(1)−Fe(2) O(7)−Fe(2)−S(1) C(7)−Fe(1)−S(1)

2.2506(9) 1.985(2) 1.261(3) 69.21(9) 81.63(7) 82.61(9)

Fe(1)−Fe(2) Fe(1)−C(7) Fe(2)−S(1) S(1)−Fe(1)−Fe(2) O(7)−Fe(2)−Fe(1) Fe(1)−S(1)−Fe(2)

2.5668(7) 1.968(3) 2.2336(11) 54.77(3) 71.99(6) 69.84(3)

Complex 7 Fe(1)−C(7) Fe(1)−Fe(2) Fe(2)−S(1) S(1)−Fe(1)−Fe(2) O(7)−Fe(2)−Fe(1) Fe(2)−S(1)−Fe(1)

1.960(2) 2.5606(7) 2.2394(7) 55.09(2) 72.33(5) 69.66(3)

Fe(1)−C(14) Fe(1)−Fe(2) O(7)−C(14) C(14)−Fe(1)−S(1) S(1)−Fe(1)−Fe(2) O(7)−Fe(2)−S(1)

1.948(3) 2.5311(6) 1.250(3) 87.98(8) 55.88(2) 87.31(6)

Fe(1)−S(1) Fe(2)−O(7) O(7)−C(7) C(7)−Fe(1)−Fe(2) O(7)−Fe(2)−S(1) S(1)−Fe(2)−Fe(1)

2.2439(7) 1.9975(15) 1.251(3) 68.81(7) 81.83(5) 55.253(19)

Fe(1)−S(1) Fe(2)−O(7) Fe(2)−S(1) C(14)−Fe(1)−Fe(2) O(7)−Fe(2)−Fe(1) Fe(1)−S(1)−Fe(2)

2.2528(9) 1.9825(18) 2.2548(8) 69.62(8) 72.16(6) 68.32(2)

Complex 10

Scheme 5



groups in their analogues A·[Et3NH] (R = 2,4,6-Me3C6H2, pMeC6H4) are attached to their bridging S atoms by equatorial and axial bonds,39,47 respectively. Possible Pathway for Formation of μ-Acyl Complexes by Pd-Catalyzed Reactions of A·[Et3NH] with IodoAromatic Compounds. Although many stoichiometric reactions regarding the [Et3NH]+ salts of anions [(μ-RS)(μ-


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Figure 8. ORTEP view of A·[Et3NH] (R = i-Pr) with 30% probability level ellipsoids.

As shown in Scheme 6, the suggested pathway includes the following seven elementary reaction steps. (i) Dissociation of the catalyst precursor PdL4 (L = PPh3) occurs to give the catalyst PdL2. (ii) Oxidative addition of ArI to PdL2 occurs to give trans-ArPdL2I. (iii) Nucleophilic attack at the Pd atom of trans-ArPdL2I by the negatively charged Fe atom of A·[Et3NH] occurs to give the Fe−Pd bond-containing A·(trans-ArPdL2). This step is very likely because similar nucleophilic attack at the Au atom of ClAuPPh3 by the negatively charged Fe atom of A· [Et3NH] is known to give the corresponding Fe−Au bond containing complexes.48 (iv) Isomerization of the Fe−Pd bond containing A·(trans-ArPdL2) occurs to give A·(cis-ArPdL2). (v) Intramolecular CO migratory insertion into the Fe−Pd bond of A·(cis-ArPdL2) occurs to give the corresponding heterotrinuclear metalloketones. It is noteworthy that although the


CO)Fe2(CO)6]− (A) are known,26−34 no catalytic reaction of A·[Et3NH] has been reported so far. However, as described above, the first catalytic reactions of A·[Et3NH] with the iodosubstituted aromatic compounds have been found by our group to produce a series of μ-acyl complexes. According to the wellknown chemical reactivity of A·[Et3NH]26−34 and the generally accepted mechanisms suggested for the classical Pd-catalyzed C−C bond cross-coupling reactions,35 we might suggest a possible pathway to account for the formation of the μ-acyl complexes 1−20 via reactions of A·[Et3NH] with the iodosubstituted aromatic compounds in the presence of Pd(PPh3)4.

Table 3. Selected Bond Lengths (Å) and Angles (deg) for 14, 15, 17, and 20 Complex 14 Fe(1) −C(1) Fe(1)−S(1) Fe(2)−C(7) O(7)−Fe(1)−S(1) S(1)−Fe(1)−Fe(2) Fe(1)−S(1)−Fe(2)

1.806(2) 2.2384(9) 1.970(2) 81.65(5) 56.01(2) 68.83(3)

O(7)−C(7) Fe(1)−S(1) Fe(2)−C(7) O(7)−Fe(1)−S(1) S(1)−Fe(1)−Fe(2) C(7)−Fe(2)−Fe(1)

1.263(3) 2.2384(7) 1.958(2) 82.02(5) 55.45(2) 69.92(7)

Fe(1)−Fe(2) Fe(2)−S(1) O(7)−C(7) O(7)−Fe(1)−Fe(2) C(7)−Fe(2)−S(1) S(1)−Fe(2)−Fe(1)

2.5429(7) 2.2609(9) 1.264(2) 72.61(5) 82.29(6) 55.17(3)

Fe(1)−O(7) Fe(1)−Fe(2) Fe(2)−S(1) O(7)−Fe(1)−Fe(2) C(7)−Fe(2)−S(1) Fe(1)−S(1)−Fe(2)

2.0119(19) 2.5545(6) 2.2473(8) 71.99(5) 81.69(7) 69.43(2)

Complex 15

Complex 17 Fe(1)−O(7) Fe(1)−Fe(2) O(7)−C(10) O(7)−Fe(1)−S(1) C(10)−Fe(2)−S(1) O(7)−Fe(1)−Fe(2)

1.9954(12) 2.5517(6) 1.2653(18) 80.40(4) 78.21(5) 71.85(3)

Fe(1)−C(1) Fe(1)−Fe(2) Fe(2)−S(1) S(1)−Fe(1)−Fe(2) O(7)−Fe(2)−Fe(1) Fe(2)−S(1)−Fe(1)

1.777(2) 2.5494(10) 2.2453(7) 55.37(2) 72.04(6) 69.12(3)

Fe(1)−S(1) Fe(2)−C(10) Fe(2)−S(1) S(1)−Fe(1)−Fe(2) C(10)−Fe(2)−Fe(1) Fe(2)−S(1)−Fe(1)

2.2527(5) 1.9716(16) 2.2457(5) 55.312(13) 70.24(4) 69.117(19)

Complex 20 Fe(1)−S(1) Fe(2)−O(7) O(7)−C(7) C(7)−Fe(1)−Fe(2) O(7)−Fe(2)−S(1) S(1)−Fe(2)−Fe(1) 1734

2.2490(8) 1.9773(15) 1.261(3) 69.97(7) 81.11(5) 55.51(3) DOI: 10.1021/acs.organomet.5b00228 Organometallics 2015, 34, 1730−1741

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Organometallics

Table 4. Selected Bond Lengths (Å) and Angles (deg) for A· [Et3NH] (R = i-Pr, sec-Bu, cy-C6H11) Salt A·[Et3NH] (R = i-Pr)

Figure 9. ORTEP view of A·[Et3NH] (R = sec-Bu) with 20% probability level ellipsoids.

Fe(1)−S(1) Fe(1)−Fe(2) Fe(2)−S(1) Fe(1)−C(4) S(1)−Fe(1)−Fe(2) S(1)−Fe(2)−Fe(1) Fe(2)−S(1)−Fe(1) Fe(1)−C(4)−Fe(2)

2.2562(19) N(1)−C(11) 2.5280(19) N(1)−C(13) 2.2508(19) Fe(2)−C(4) 1.928(6) C(4)−O(4) 55.78(4) C(4)−Fe(1)−S(1) 55.98(6) C(4)−Fe(2)−Fe(1) 68.24(6) C(11)−N(1)−C(13) 82.1(2) C(11)−N(1)−C(15) Salt A·[Et3NH] (R = sec-Bu)

1.493(8) 1.495(8) 1.921(6) 1.208(7) 78.58(18) 49.06(18) 113.9(5) 109.8(5)

Fe(1)−C(1) Fe(2)−S(1) Fe(1)−S(1) Fe(2)−C(1) C(2)−Fe(1)−S(1) C(3)−Fe(1)−S(1) C(4)−Fe(1)−S(1) C(1)−Fe(1)−S(1)

1.944(4) O(1)−C(1) 2.2927(12) N(1)−C(14) 2.2723(12) N(1)−C(12) 1.963(4) Fe(1)−Fe(2) 158.28(14) C(5)−Fe(2)−S(1) 98.41(15) C(6)−Fe(2)−S(1) 94.02(13) C(8)−S(1)−Fe(1) 78.26(13) S(1)−Fe(1)−Fe(2) Salt A·[Et3NH] (R = cy-C6H11)

1.207(4) 1.497(8) 1.490(8) 2.5461(8) 100.63(16) 94.50(14) 114.8(9) 56.48(3)

N(1)−C(14) Fe(1)−C(1) Fe(1)−Fe(2) Fe(2)−S(1) C(1)−Fe(1)−S(1) S(1)−Fe(1)−Fe(2) C(1)−Fe(2)−Fe(1) Fe(1)−C(1)−Fe(2)

1.451(5) 1.944(3) 2.5396(6) 2.2764(8) 78.09(8) 56.23(2) 49.20(8) 81.45(10)

N(1)−C(16) Fe(1)−S(1) Fe(2)−C(1) O(1)−C(1) C(1)−Fe(1)−Fe(2) C(1)−Fe(2)−S(1) S(1)−Fe(2)−Fe(1) Fe(1)−S(1)−Fe(2)

1.463(5) 2.2634(9) 1.948(3) 1.200(3) 49.35(8) 77.68(8) 55.74(2) 68.03(2)

Scheme 6

Figure 10. ORTEP view of A·[Et3NH] (R = cy-C6H11) with 20% probability level ellipsoids.

heterotrinuclear metalloketone is unprecedented, the homodinuclear metalloketone [Pd(dam)Cl]2CO is known.49 (vi) αReductive elimination from the Pd atom of the metalloketone intermediates occurs to give σ-aroyl intermediates (μ-RS)(μCO)Fe2(CO)5(σ-ArCO) with regeneration of the catalyst PdL2. (vii) Coordination of the σ-bonded aroyl group to the other Fe atom and migration of the bridging CO to a terminal position occur to give the benzoyl and heterocyclic type μ-acyl complexes 1−20. It should be emphasized that, although this suggested pathway appears to be reasonable, it is mainly based on some of the previously reported experimental facts,48,49 the well-known chemical reactivity regarding A·[Et3NH] salts,26−34 and the generally accepted mechanisms previously reported for the classical Pd-catalyzed C−C bond cross-coupling reactions.35

such Pd-catalyzed C−C bond cross-coupling reactions for production of μ-acyl complexes are not only simple and convenient but also more atom economical and more environmentally benign than the previously reported stoichiometric reactions of A·[Et3NH] with acid chlorides12,39 or organomercuric halides.40 In addition, all the prepared new μacyl complexes and the three new isolated intermediate salts A· [Et3NH] (R = i-Pr, sec-Bu, cy-C6H11) have been structurally characterized and a possible pathway including seven elementary reaction steps is suggested for such types of Pdcatalyzed reactions. This work would open a new way to develop Fe/S cluster chemistry based on A·[Et3NH] salts. Further study on the scope and limits for such types of Pd-

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SUMMARY AND CONCLUSION We have developed the first catalytic reactions of A·[Et3NH] salts, in which in situ prepared A·[Et3NH] salts (R = i-Pr, secBu, cy-C6H11, p-MeC6H4) react with iodo-substituted aromatic compounds in the presence of the Pd(0) catalyst precursor Pd(PPh3)4 to give the benzoyl and heterocyclic type μ-acyl complexes (μ-RS)(μ-ArCO)Fe2(CO)6 (1−20). Interestingly, 1735


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Organometallics

(vs), 1993 (vs), 1966 (s); νCO 1463 (m) cm−1. 1H NMR (400 MHz, CDCl3): 1.11−1.60 (m, 6H, 2CH3), 2.16 (br s, a-isomer, SCH), 2.68 (br s, e-isomer, SCH), 7.04−7.45 (m, 4H, C6H4) ppm. 13C{1H} NMR (100 MHz, CDCl3): 26.1, 26.4, 26.9, 27.2 (4 s, CH3), 36.2 (s, aisomer, SCH), 43.3 (s, e-isomer, SCH), 112.1−163.9 (m, C6H4), 207.5, 209.6, 209.7, 210.3, 211.2, 211.9 (6 s, CO), 288.6 (s, eisomer, CO), 291.0 (s, a-isomer, CO) ppm. 19F NMR (376 MHz, CDCl3, CFCl3): −111.6 (s), −111.9 (s) ppm. Preparation of (μ-i-PrS)(μ-p-CF3C6H4CO)Fe2(CO)6 (4). The same procedure was followed as for 1, except that p-CF3C6H4I (0.204 g, 0.75 mmol) was used instead of PhI. From the first red band, (μ-iPrS)2Fe2(CO)6 (0.012 g, 11%) was obtained. From the second red band, 4 (0.141 g, 53%) was obtained as a red oil (1/3 a/e isomer mixture by 1H NMR). Anal. Calcd for C17H11F3Fe2O7S: C, 38.67; H, 2.10. Found: C, 38.39; H, 2.02. IR (KBr disk): νCO 2075 (s), 2033 (vs), 1996 (vs), 1968 (s); νCO 1468 (m) cm−1. 1H NMR (400 MHz, CDCl3): 1.11−1.61 (m, 6H, 2CH3), 2.17 (br s, a-isomer, SCH), 2.69 (br s, e-isomer, SCH), 7.56, 7.64 (2 br s, 4H, C6H4) ppm. 13C{1H} NMR (100 MHz, CDCl3): 26.2, 26.4, 26.9, 27.2 (4 s, CH3), 36.3 (s, aisomer, SCH), 43.4 (s, e-isomer, SCH), 122.1 (s, a-isomer, CF3), 124.9 (s, e-isomer, CF3), 125.5−146.5 (m, C6H4), 207.4, 209.5, 209.6, 210.2, 211.2, 211.8 (6 s, CO), 290.4 (s, e-isomer, CO), 292.7 (s, aisomer, CO) ppm. 19F NMR (376 MHz, CDCl3, CFCl3): −63.2 (s) ppm. Preparation of (μ-i-PrS)(μ-p-MeO2CC6H4CO)Fe2(CO)6 (5). The same procedure was followed as for 1, except that p-MeO2CC6H4I (0.197 g, 0.75 mmol) was utilized in place of PhI. From the first red band, (μ-i-PrS)2Fe2(CO)6 (0.012 g, 11%) was obtained. From the second red band, 5 (0.142 g, 55%) was obtained as a red solid (1/3 a/e isomer mixture by 1H NMR), mp 90−91 °C. Anal. Calcd for C18H14Fe2O9S: C, 41.73; H, 2.72. Found: C, 41.89; H, 2.83. IR (KBr disk): νCO 2073 (s), 2030 (vs), 1993 (vs), 1966 (s); νOCO 1730 (s); νCO 1463 (m) cm−1. 1H NMR (400 MHz, CDCl3): 1.09−1.60 (m, 6H, CH(CH3)2), 2.18 (br s, a-isomer, SCH), 2.68 (br s, e-isomer, SCH), 3.92 (s, 3H, OCH3), 7.48−7.57, 8.01−8.10 (2m, 4H, C6H4) ppm. 13C{1H} NMR (100 MHz, CDCl3): 26.1, 26.4, 26.9, 27.2 (4 s, CH(CH3)2), 36.2 (s, a-isomer, SCH), 43.4 (s, e-isomer, SCH), 52.5 (s, OCH3), 126.3−147.1 (m, C6H4), 166.0 (s, OCO), 207.5, 209.5, 209.6, 210.2, 211.2, 211.9 (6 s, CO), 290.7 (s, e-isomer, CO), 293.1 (s, a-isomer, CO) ppm. Preparation of (μ-i-PrS)(μ-p-MeOC6H4CO)Fe2(CO)6 (6). The same procedure was followed as for 1, except that p-MeOC6H4I (0.176 g, 0.75 mmol) was utilized in place of PhI. From the first red band, (μ-iPrS)2Fe2(CO)6 (0.009 g, 8%) was obtained. From the second red band, 6 (0.148 g, 60%) was obtained as a red oil (1/3 a/e isomer mixture by 1H NMR). Anal. Calcd for C17H14Fe2O8S: C, 41.67; H, 2.88. Found: C, 41.67; H, 2.73. IR (KBr disk): νCO 2070 (s), 2027 (vs), 1990 (vs), 1963 (s); νCO 1451 (s) cm−1. 1H NMR (400 MHz, CDCl3): 1.11−1.59 (m, 6H, CH(CH3)2), 2.17 (br s, a-isomer, SCH), 2.67 (br s, e-isomer, SCH), 3.84 (s, 3H, OCH3), 6.84, 7.51 (2 s, 4H, C6H4) ppm. 13C{1H} NMR (100 MHz, CDCl3): 26.1, 26.5, 27.0, 27.2 (4 s, CH(CH3)2), 36.0 (s, a-isomer, SCH), 43.2 (s, e-isomer, SCH), 55.6 (s, OCH3), 113.4−164.0 (m, C6H4), 207.8, 209.8, 210.6, 211.1, 211.7, 212.4 (6 s, CO), 282.9 (s, e-isomer, CO), 285.6 (s, aisomer, CO) ppm. Preparation of (μ-i-PrS)(μ-2,4,6-Me3C6H2CO)Fe2(CO)6 (7). The same procedure was followed as for 1, except that 2,4,6-Me3C6H2I (0.185 g, 0.75 mmol) was employed instead of PhI. From the first red band, (μ-i-PrS)2Fe2(CO)6 (0.020 g, 19%) was obtained. From the second red band, 7 (0.095 g, 38%) was obtained as a red solid (only eisomer by 1H and 13C{1H} NMR), mp 90−91 °C. Anal. Calcd for C19H18Fe2O7S: C, 45.45; H, 3.61. Found: C, 45.38; H, 3.68. IR (KBr disk): νCO 2071 (s), 2029 (vs), 1992 (vs), 1968 (s); νCO 1479 (m) cm−1. 1H NMR (400 MHz, CDCl3): 1.55, 1.62 (2d, J = 6.0 Hz, 6H, CH(CH3)2), 2.11, 2.21 (2 s, 9H, 3CH3 attached to benzene ring), 2.68 (br s, 1H, SCH), 6.70 (s, 2H, C6H2) ppm. 13C{1H} NMR (100 MHz, CDCl3): 19.2, 20.9 (2 s, CH3 attached to benzene ring), 26.5, 26.8 (2 s, CH(CH3)2), 43.3 (s, SCH), 129.0, 138.3, 148.6 (3 s, C6H2), 208.7, 209.6, 212.4 (3 s, CO), 306.6 (s, CO) ppm.

catalyzed reactions will be carried out in this laboratory in the near future.

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EXPERIMENTAL SECTION

General Comments. All reactions were carried out using standard Schlenk and vacuum-line techniques under an atmosphere of nitrogen. THF was distilled under N2 from sodium/benzophenone ketyl. 2Ethyl-3-iodo-5-phenylfuran,50 3-iodo-2-methyl-5-phenylthiophene,51 3-iodo-4,5-dimethyl-2-phenylthiophene,52 3-iodo-2-phenylbenzo[b]furan,53 3-iodo-2-methylbenzo[b]thiophene,54 3-iodo-1-methyl-2methylindole,55 and Fe3(CO)1256 were prepared according to the published procedures. Other materials were available commercially and used as received without further purification. Preparative TLC was carried out on glass plates (26 × 20 × 0.25 cm) coated with silica gel H (10−40 μm). IR spectra were recorded on a Bruker Tensor 27 FTIR infrared spectrophotometer. 1H, 13C{1H}, and 19F NMR spectra were taken on a Bruker Avance 400 NMR spectrometer. Elemental analyses were performed with an Elementar Vario EL analyzer. Melting points were determined on a SGW X-4 microscopic melting point apparatus and were uncorrected. Standard in Situ Preparation of Complex Salts A·[Et3NH] (R = i-Pr, sec-Bu, cy-C6H11, p-MeC6H4) by Reactions of Fe3(CO)12, RSH, and Et3N. A 100 mL three-necked flask equipped with a serum cap, a magnetic stirbar, and a N2 inlet tube was charged with THF (15 mL), Fe3(CO)12 (0.252 g, 0.5 mmol), Et3N (0.070 mL, 0.5 mmol), and the appropriate RSH (0.5 mmol). The solution was stirred for 15 min at room temperature, during which time slow gas evolution and a gradual color change from green to brown-red were observed. The resulting THF solutions of A·[Et3NH] (R = i-Pr, sec-Bu, cy-C6H11, pMeC6H4) were utilized in situ to prepare the μ-acyl complexes 1−20. In addition, the in situ prepared THF solutions of the three new complex salts A·[Et3NH] (R = i-Pr, sec-Bu, cy-C6H11) were also utilized to isolate them in order to confirm their structures. Preparation of μ-Acyl Complexes 1−20 by Reactions of the Standard in Situ Prepared A·[Et3NH] (R = i-Pr, sec-Bu, cy-C6H11, p-MeC6H4) with Iodo-Substituted Aromatic Compounds. Preparation of (μ-i-PrS)(μ-PhCO)Fe2(CO)6 (1). To the above in situ prepared THF solution of A·[Et3NH] (R = i-Pr) from i-PrSH (0.047 mL, 0.5 mmol) were added PhI (0.084 mL, 0.75 mmol) and Pd(PPh3)4 (0.029 g, 5 mmol %). The mixture was stirred at 55 °C for 1.5 h, during which time a white precipitate and a color change from brown-red to bright red were observed. THF was removed in vacuo, and the residue was subjected to TLC separation using petroleum ether as an eluent. From the first and second red bands, (μ-iPrS)2Fe2(CO)6 (0.010 g, 9%) and 1 (0.134 g, 58%) were obtained as red solids, which were identified by comparison of their IR and 1H NMR spectra with those of the authentic samples prepared by other methods,41,43 respectively. Preparation of (μ-i-PrS)(μ-p-BrC6H4CO)Fe2(CO)6 (2). The same procedure was followed as for 1, except that p-BrC6H4I (0.212 g, 0.75 mmol) was used instead of PhI. From the first red band, (μ-iPrS)2Fe2(CO)6 (0.013 g, 12%) was obtained. From the second red band, 2 (0.135 g, 50%) was obtained as a red solid (1/5 a/e isomer mixture by 1 H NMR), mp 99−100 °C. Anal. Calcd for C16H11BrFe2O7S: C, 35.66; H, 2.06. Found: C, 35.83; H, 2.23. IR (KBr disk): νCO 2073 (s), 2030 (vs), 1993 (vs), 1965 (s); νCO 1461 (s) cm−1. 1H NMR (400 MHz, CDCl3): 1.10−1.60 (m, 6H, 2CH3), 2.15 (br s, a-isomer, SCH), 2.67 (br s, e-isomer, SCH), 7.35, 7.52 (2 br s, 4H, C6H4) ppm. 13C{1H} NMR (100 MHz, CDCl3): 26.1, 26.4, 26.9, 27.2 (4 s, CH3), 36.2 (s, a-isomer, SCH), 43.4 (s, e-isomer, SCH), 128.1−143.2 (m, C6H4), 207.5, 209.6, 209.9, 210.5, 211.3, 211.9 (6 s, CO), 287.9 (s, e-isomer, CO), 290.4 (s, a-isomer, C O) ppm. Preparation of (μ-i-PrS)(μ-m-FC6H4CO)Fe2(CO)6 (3). The same procedure was followed as for 1, except that m-FC6H4I (0.167 g, 0.75 mmol) was used instead of PhI. From the first red band, (μ-iPrS)2Fe2(CO)6 (0.011 g, 10%) was obtained. From the second red band, 3 (0.122 g, 51%) was obtained as a red oil (1/3 a/e isomer mixture by 1H NMR). Anal. Calcd for C16H11FFe2O7S: C, 40.20; H, 2.32. Found: C, 40.47; H, 2.33. IR (KBr disk): νCO 2074 (s), 2032 1736


Article

Organometallics

respectively. From the first red band, (μ-sec-BuS)2Fe2(CO)6 (0.016 g, 14%) was obtained. From the second red band, 12 (0.118 g, 42%) was obtained as a red oil (a/e isomer mixture by 13C{1H} NMR). Anal. Calcd for C23H20Fe2O8S: C, 48.62; H, 3.55. Found: C, 48.57; H, 3.53. IR (KBr disk): νCO 2070 (s), 2026 (vs), 1992 (vs), 1961 (s); νCO 1489 (m) cm−1. 1H NMR (400 MHz, CDCl3): 1.12 (s, 6H, CHCH2CH3, CH2CH3), 1.49, 1.56 (2 s, 3H, CHCH3), 1.74−1.95 (m, 2H, CHCH2CH3), 2.46−2.61 (m, 3H, SCH, CH2CH3), 7.02−7.66 (m, 6H, C6H5C4HO) ppm. 13C{1H} NMR (100 MHz, CDCl3): 10.0− 48.0 (m, CH3CHCH2CH3, CH2CH3), 105.4−155.6 (m, C6H5C4HO), 208.6, 209.4, 209.9, 210.6, 211.2 (6 s, CO), 277.0 (s, e-isomer, C O), 280.0 (s, a-isomer, CO) ppm. Preparation of (μ-i-Pr)(μ-2-Me-5-PhC4HS-3-CO)Fe2(CO)6 (13). The same procedure was followed as for 1, except that 3-iodo-2-methyl-5phenylthiophene (0.225 g, 0.75 mmol) was utilized in place of PhI. From the first red band, (μ-i-PrS)2Fe2(CO)6 (0.012 g, 11%) was obtained. From the second red band, 13 (0.138 g, 50%) was obtained as a red solid (1/7 a/e isomer mixture by 1H NMR), mp 111−113 °C. Anal. Calcd for C21H16Fe2O7S2: C, 45.35; H, 2.90. Found: C, 45.35; H, 2.89. IR (KBr disk): νCO 2073 (s), 2033 (vs), 1999 (vs); νCO 1488 (m) cm−1. 1H NMR (400 MHz, CDCl3): 1.26−1.60 (m, 6H, CH(CH3)2), 2.24 (s, 3H, CH3 attached to thiophene ring), 2.51 (s, aisomer, SCH), 2.66 (s, e-isomer, SCH), 7.30−7.67 (m, 6H, C6H5C4HS) ppm. 13C{1H} NMR (100 MHz, CDCl3): 16.0, 16.1, (2 s, CH3 attached to thiophene ring), 26.2, 26.6, 27.0, 27.4 (4 s, CH(CH3)2), 36.7 (s, a-isomer, SCH), 43.4 (s, e-isomer, SCH), 125.8− 146.0 (m, C6H5C4HS), 207.7, 209.7, 210.4, 211.1, 211.9, 212.5 (6 s, CO), 279.4 (s, e-isomer, CO), 282.3 (s, a-isomer, CO) ppm. Preparation of (μ-sec-BuS)(μ-2-Me-5-PhC4HS-3-CO)Fe2(CO)6 (14). The same procedure was followed as for 1, but the in situ prepared solution of A·[Et3NH] (R = sec-Bu) from sec-BuSH (0.055 mL, 0.5 mmol) and 3-iodo-2-methyl-5-phenylthiophene (0.225 g, 0.75 mmol) were employed in place of the A·[Et3NH] (R = i-Pr) solution and PhI, respectively. From the first red band, (μ-sec-BuS)2Fe2(CO)6 (0.010 g, 9%) was obtained. From the second red band, 14 (0.150 g, 53%) was obtained as a red solid (only e-isomer by 1H and 13C{1H} NMR), mp 123−125 °C. Anal. Calcd for C22H18Fe2O7S2: C, 46.34; H, 3.18. Found: C, 46.17; H, 2.98. IR (KBr disk): νCO 2069 (s), 2028 (vs), 1990 (vs), 1962 (s); νCO 1492 (m) cm−1. 1H NMR (400 MHz, CDCl3): 1.05−1.15 (m, 3H, CH2CH3), 1.45−1.58 (m, 3H, CHCH3), 1.74−1.92 (m, 2H, CH2CH3), 2.22−2.30 (m, 3H, CH3 attached to thiophene ring), 2.49 (br s, 1H, SCH), 7.29−7.76 (m, 6H, C6H5C4HS) ppm. 13C{1H} NMR (100 MHz, CDCl3): 11.5−49.2 (m, CH3CHCH2CH3), 16.0 (s, CH3 attached to thiophene ring), 125.8−146.1 (m, C6H5C4HS), 209.9, 210.5, 212.6 (3 s, CO), 279.4 (s, CO) ppm. Preparation of (μ-cy-C6H11S)(μ-2-Ph-4,5-Me2C4S-3-CO)Fe2(CO)6 (15). The same procedure was followed as for 1, but the in situ prepared solution of A·[Et3NH] (R = cy-C6H11S) from cy-C6H11SH (0.061 mL, 0.5 mmol) and 3-iodo-4,5-dimethyl-2-phenylthiophene (0.236 g, 0.75 mmol) were utilized instead of the A·[Et3NH] (R = iPr) solution and PhI, respectively. From the first red band, (μ-cyC6H11S)2Fe2(CO)6 (0.020 g, 16%) was obtained. From the second red band, 15 (0.106 g, 35%) was obtained as a red solid (only e-isomer by 13 C{1H} NMR), mp 121−123 °C. Anal. Calcd for C25H22Fe2O7S2: C, 49.20; H, 3.63. Found: C, 49.40; H, 3.55. IR (KBr disk): νCO 2070 (s), 2029 (vs), 1991 (vs), 1961 (s); νCO 1503 (m) cm−1. 1H NMR (400 MHz, CDCl3): 1.26−2.32 (m, 17H, C6H11, 2CH3), 7.30, 7.39 (2 s, 5H, C6H5) ppm. 13C{1H} NMR (100 MHz, CDCl3): 12.7, 13.3 (2 s, CH3), 25.5, 26.3, 26.4, 37.1, 37.5, 51.6 (6 s, C6H11), 128.3−149.3 (m, C6H5C4S), 207.4, 209.7, 211.4 (3 s, CO), 299.8 (s, CO) ppm. Preparation of (μ-p-MeC6H4S)(μ-2-PhC8H4O-3-CO)Fe2(CO)6 (16). The same procedure was followed as for 1, but the in situ prepared solution of A·[Et3NH] (R = p-MeC6H4) from p-MeC6H4SH (0.062 g, 0.5 mmol) and 3-iodo-2-phenylbenzo[b]furan (0.240 g, 0.75 mmol) were used in place of the A·[Et3NH] (R = i-Pr) solution and PhI, respectively. From the first red band, (μ-p-MeC6H4S)2Fe2(CO)6 (0.024 g, 18%) was obtained. From the second red band, 16 (0.122 g, 39%) was obtained as a red solid (1/4 a/e isomer mixture by 1H NMR), mp 63−65 °C. Anal. Calcd for C28H16Fe2O8S: C, 53.88; H,

Preparation of (μ-sec-BuS)(μ-2,4,6-Me3C6H2CO)Fe2(CO)6 (8). The same procedure was followed as for 1, but the in situ prepared solution of A·[Et3NH] (R = sec-Bu) from sec-BuSH (0.055 mL, 0.5 mmol) and 2,4,6-Me3C6H2I (0.185 g, 0.75 mmol) were utilized instead of the A· [Et3NH] (R = i-Pr) solution and PhI, respectively. From the first red band, (μ-sec-BuS)2Fe2(CO)6 (0.032 g, 28%)41 was obtained. From the second red band, 8 (0.096 g, 37%) was obtained as a red oil (only eisomer by 1H and 13C{1H} NMR). Anal. Calcd for C20H20Fe2O7S: C, 46.54; H, 3.91. Found: C, 46.30; H, 3.89. IR (KBr disk): νCO 2071 (s), 2027 (vs), 1990 (vs), 1967 (s); νCO 1479 (m) cm−1. 1H NMR (400 MHz, CDCl3): 1.12−1.17 (m, 3H, CH2CH3), 1.53, 1.60 (2d, J = 6.8 Hz, 3H, CHCH3), 1.80−2.00 (m, 2H, CH2), 2.12, 2.22 (2 s, 9H, 3CH3 attached to benzene ring), 2.49−2.60 (m, 1H, SCH), 6.71 (s, 2H, C6H2) ppm. 13C{1H} NMR (100 MHz, CDCl3): 11.2−49.0 (m, CH3CHCH2CH3, CH3), 129.0, 138.3, 148.6 (3 s, C6H2), 208.7, 209.7, 212.4 (3 s, CO), 306.6 (s, CO) ppm. Preparation of (μ-cy-C6H11S)(μ-PhCO)Fe2(CO)6 (9). The same procedure was followed as for 1, but the in situ prepared solution of A· [Et3NH] (R = cy-C6H11) from cy-C6H11SH (0.061 mL, 0.5 mmol) was employed instead of the A·[Et3NH] (R = i-PrS) solution. From the first red band, (μ-cy-C6H11S)2Fe2(CO)6 (0.010 g, 8%) was obtained as a red solid, mp 116−118 °C. Anal. Calcd for C18H22Fe2O6S2: C, 42.38; H, 4.35. Found: C, 42.51; H, 4.50. IR (KBr disk): νCO 2071 (s), 2027 (vs), 1991 (vs) cm−1. 1H NMR (400 MHz, CDCl3): 1.20−2.43 (m, 22H, 2C6H11) ppm. 13C{1H} NMR (100 MHz, CDCl3): 25.4−51.9 (m, C6H11), 209.2, 209.9 (2 s, CO) ppm. From the second red band, 9 (0.133 g, 53%) was obtained as a red solid (a/e isomer mixture by 13C{1H} NMR), mp 97−98 °C. Anal. Calcd for C19H16Fe2O7S: C, 45.63; H, 3.22. Found: C, 45.45; H, 3.21. IR (KBr disk): νCO 2071 (s), 2028 (vs), 1990 (vs), 1964 (s); νCO 1468 (s) cm−1. 1H NMR (400 MHz, CDCl3): 0.84−2.40 (m, 11H, C6H11), 7.35−7.50 (m, 5H, C6H5) ppm. 13C{1H} NMR (100 MHz, CDCl3): 25.5−51.7 (m, C6H11), 126.5−145.4 (m, C6H5), 207.8, 209.9, 210.2, 210.6, 211.6, 212.2 (6 s, CO), 289.0 (s, e-isomer, CO), 292.0 (s, a-isomer, C O) ppm. Preparation of (μ-p-MeC6H4S)(μ-PhCO)Fe2(CO)6 (10). The same procedure was followed as for 1, but the in situ prepared solution of A· [Et3NH] (R = p-MeC6H4) from p-MeC6H4SH (0.062 g, 0.5 mmol) was employed instead of the A·[Et3NH] (R = i-Pr) solution. From the first red band, (μ-p-MeC6H4S)2Fe2(CO)6 (0.020 g, 15%)42 was obtained. From the second red band, 10 (0.136 g, 54%) was obtained as a red solid (1/3 a/e isomer by 1H NMR), mp 105−106 °C. Anal. Calcd for C20H12Fe2O7S: C, 47.28; H, 2.38. Found: C, 47.47; H, 2.40. IR (KBr disk): νCO 2075 (s), 2033 (vs), 1998 (vs), 1964 (s); νCO 1469 (s) cm−1. 1H NMR (400 MHz, CD3COCD3): 2.19 (s, e-isomer, CH3), 2.29 (s, a-isomer, CH3), 6.93−7.67 (m, 9H, C6H4, C6H5) ppm. 13 C{1H} NMR (100 MHz, CDCl3): 20.9, 21.1 (2 s, CH3), 126.5− 145.8 (m, C6H4, C6H5), 207.4, 208.8, 210.0, 211.5, 212.1 (5 s, CO), 289.9 (s, e-isomer, CO), 291.3 (s, a-isomer, CO) ppm. Preparation of (μ-i-PrS)(μ-2-Et-5-PhC4HO-3-CO)Fe2(CO)6 (11). The same procedure was followed as for 1, except that 2-ethyl-3iodo-5-phenylfuran (0.224 g, 0.75 mmol) was used instead of PhI. From the first red band, (μ-i-PrS)2Fe2(CO)6 (0.015 g, 14%) was obtained. From the second red band, 11 (0.112 g, 40%) was obtained as a red oil (a/e isomer mixture by 13C{1H} NMR). Anal. Calcd for C22H18Fe2O8S: C, 47.68; H, 3.27. Found: C, 47.59; H, 3.44. IR (KBr disk): νCO 2070 (s), 2027 (vs), 1992 (vs), 1963 (s); νCO 1490 (w) cm−1. 1H NMR (400 MHz, CDCl3): 0.79, 1.01 (2 s, 3H, CH2CH3), 1.15−1.52 (m, 6H, CH(CH3)2), 2.11, 2.48 (2 br s, 3H, SCH, CH2CH3), 6.92−7.54 (m, 6H, C6H5C4HO) ppm. 13C{1H} NMR (100 MHz, CDCl3): 11.8, 11.9 (2 s, CH2CH3), 22.1 (s, CH2CH3), 26.2, 26.5, 27.0, 27.3 (4 s, CH(CH3)2), 36.4 (s, a-isomer, SCH), 43.3 (s, eisormer, SCH), 106.6−156.7 (m, C6H5C4HO), 207.7, 209.7, 210.5, 211.1, 211.7, 212.3 (6 s, CO), 278.1 (s, e-isomer, CO), 281.1 (s, a-isomer, CO) ppm. Preparation of (μ-sec-BuS)(μ-2-Et-5-PhC4HO-3-CO)Fe2(CO)6 (12). The same procedure was followed as for 1, but the in situ prepared solution of A·[Et3NH] (R = sec-Bu) from sec-BuSH (0.055 mL, 0.5 mmol) and 2-ethyl-3-iodo-5-phenylfuran (0.224 g, 0.75 mmol) were employed instead of the A·[Et3NH] (R = i-Pr) solution and PhI, 1737


Article

Organometallics

νCO 1490 (m) cm−1. 1H NMR (400 MHz, CDCl3): 0.90−2.36 (m, 11H, C6H11), 2.50 (s, e-isomer, CH3 attached to indole ring), 2.70 (s, a-isomer, CH3 attached to indole ring), 3.58 (s, e-isomer, NCH3), 3.64 (s, a-isomer, NCH3), 7.20−7.31, 7.98−8.10 (2m, 4H, C6H4) ppm. 13 C{1H} NMR (100 MHz, CDCl3): 12.9−51.8 (m, CH3, NCH3, C6H11), 109.2−141.6 (m, C8H4N), 209.8, 210.2, 210.8, 212.4, 213.8, 214.3 (6 s, CO), 270.8 (s, e-isomer, CO), 273.4 (s, a-isomer, C O) ppm. Isolation and Characterization of New Complex Salts A· [Et3NH] (R = i-Pr, sec-Bu, cy-C6H11). Isolation of A·[Et3NH] (R = iPr). The THF solution of A·[Et3NH] (R = i-Pr) prepared by the standard in situ method described above was evaporated at reduced pressure to leave a sticky brown-black residue. The residue was transferred to a drybox and washed thoroughly with n-hexane to remove the major impurities of (μ-RS)2Fe2(CO)6 (R = i-Pr) formed in situ by decomposition of A·[Et3NH] (R = i-Pr).40 After the washed residue was extracted with Et2O (3 × 10 mL), the combined extracts were evaporated at reduced pressure to leave a red solid, which was dissolved in CH2Cl2 (20 mL). To the CH2Cl2 solution was carefully added 40 mL of n-hexane to allow slow diffusion of n-hexane into the layer of CH2Cl2. After the system stayed at room temperature for 24 h, a red precipitate was formed. The precipitate was washed with nhexane and dried under vacuum to give A·[Et3NH] (R = i-Pr; 0.160 g, 66%) as a red solid, mp 78−80 °C (in a sealed capillary under N2). Anal. Calcd for C16H23Fe2NO7S: C, 39.70; H, 4.58; N, 2.89. Found: C, 39.75; H, 4.37; N, 2.85. IR (KBr disk): νCO 2077 (s), 2037 (s), 1974 (vs); νμ‑CO 1728 (w) cm−1. 1H NMR (400 MHz, DMSO-d6): 1.14 (s, 9H, 3CH2CH3), 1.29 (s, 6H, CH(CH3)2), 2.12−2.17 (m, 1H, CH), 3.02 (s, 6H, 3CH2CH3), 8.83 (br s, 1H, NH) ppm. 13C{1H} NMR (100 MHz, DMSO-d6): 9.5 (s, CH2CH3), 27.3 (s, CHCH3), 44.7 (s, CH), 46.2 (s, CH2), 217.8 (s, CO), 224.8 (s, CO) ppm. Isolation of A·[Et3NH] (R = sec-Bu). By the same isolation procedure as for A·[Et3NH] (R = i-Pr), A·[Et3NH] (R = sec-Bu; 0.150 g, 60%) was isolated from its THF solution as a red solid, mp 58−60 °C (in a sealed capillary under N2). Anal. Calcd for C17H25Fe2NO7S: C, 40.91; H, 5.05; N, 2.81. Found: C, 40.98; H, 4.77; N, 2.56. IR (KBr disk): νCO 2076 (m), 2035 (s), 1975 (vs); νμ‑CO 1730 (w) cm−1. 1 H NMR (400 MHz, DMSO-d6): 0.93 (br s, 3H, CHCH2CH3), 1.13− 1.27 (m, 12H, N(CH2CH3)3, CHCH3), 1.50, 1.74 (2 br s, 2H, CHCH2CH3), 2.10 (br s, 1H, CH), 2.98 (br s, 6H, N(CH2CH3)3), 8.93 (br s, 1H, NH) ppm. 13C{1H} NMR (100 MHz, DMSO-d6): 9.7 (s, CH2CH3), 11.7, 23.9, 33.6 (3 s, CH3CHCH2CH3), 46.2 (s, CH2CH3), 50.4 (s, CH), 217.8 (s, CO), 224.9 (s, CO) ppm. Isolation of A·[Et3NH] (R = cy-C6H11). Similarly, A·[Et3NH] (R = cy-C6H11; 0.184 g, 70%) was isolated from its THF solution as a red solid, mp 96−98 °C (in a sealed capillary under N2). Anal. Calcd for C19H27Fe2NO7S: C, 43.45; H, 5.18; N, 2.67. Found: C, 43.15; H, 5.19; N, 2.57. IR (KBr disk): νCO 2074 (m), 2031 (s), 1969 (vs); νμ‑CO 1739 (w) cm−1. 1H NMR (400 MHz, DMSO-d6): 1.14 (br s, 9H, 3CH2CH3), 1.33−2.08 (m, 11H, C6H11), 3.02 (br s, 6H, 3CH2CH3), 8.88 (br s, 1H, NH) ppm. 13C{1H} NMR (100 MHz, DMSO-d6): 9.2 (s, CH2CH3), 25.7, 26.5, 37.7, 53.1 (4 s, C6H11), 217.8 (s, CO), 224.9 (s, CO) ppm. X-ray Structure Determinations of μ-Acyl Complexes 2, 7, 10, 14, 15, 17, and 20 and A·[Et3NH] Salts (R = i-Pr, sec-Bu, cyC6H11). Single crystals of the μ-acyl complexes 2, 7, 10, 14, 15, 17, and 20 suitable for X-ray diffraction analyses were grown by slow evaporation of their CH2Cl2/n-pentane solution at room temperature, whereas single crystals of the A·[Et3NH] salts (R = i-Pr, sec-Bu, cyC6H11) were grown by slow diffusion of hexane into their CH2Cl2 solutions in a drybox. Each single crystal was mounted on a Rigaku MM-007 (rotating anode) diffractometer equipped with Saturn 724 CCD, a Rigaku SCX-mini diffractometer, or a Bruker D8quest CCD diffractometer. Data were collected at room temperature, using a confocal monochromator with Mo Kα radiation (λ = 0.71073 or 0.71075 Å) in the ω−ϕ scanning mode. Data collection, reduction, and absorption correction were performed with the CRYSTALCLEAR program.57 The structures were solved by direct methods using the SHELXS-97 program58 and refined by full-matrix least-squares techniques (SHELXL-97)59 on F2. Hydrogen atoms were located by

2.58. Found: C, 53.73; H, 2.65. IR (KBr disk): νCO 2074 (s), 2033 (vs), 1999 (vs), 1962 (s); νCO 1488 (m) cm−1. 1H NMR (400 MHz, CDCl3): 1.99 (s, a-isomer, CH3), 2.27 (s, e-isomer, CH3), 6.55−7.76 (m, 13H, C6H4, C6H5C8H4O) ppm. 13C{1H} NMR (100 MHz, CDCl3): 20.9, 21.1 (2 s, CH3), 110.8−157.7 (m, C6H4, C6H5C8H4O), 207.5, 207.8, 208.8, 209.1, 212.7, 213.4 (6 s, CO), 282.1 (s, aisomer, CO), 288.4 (s, e-isomer, CO) ppm. Preparation of (μ-i-PrS)(μ-2-MeC8H4S-3-CO)Fe2(CO)6 (17). The same procedure was followed as for 1, except that 3-iodo-2methylbenzo[b]thiophene (0.206 g, 0.75 mmol) was utilized instead of PhI. From the first red band, (μ-i-PrS)2Fe2(CO)6 (0.012 g, 11%) was obtained. From the second red band, 17 (0.135 g, 51%) was obtained as a red solid (only e-isomer by 1H and 13C{1H} NMR), mp 140−141 °C. Anal. Calcd for C19H14Fe2O7S2: C, 43.05; H, 2.66. Found: C, 43.08; H, 2.49. IR (KBr disk): νCO 2070 (s), 2029 (vs), 1992 (vs), 1960 (s); νCO 1493 (m) cm−1. 1H NMR (400 MHz, CD3COCD3): 1.55, 1.66 (2 d, J = 6.4 Hz, 6H, CH(CH3)2), 2.53 (s, 3H, CH3 attached to benzothiophene ring), 2.66−2.75 (m, 1H, SCH), 7.36, 7.44 (2 t, J = 8.0 Hz, 2H, 2β-H of benzene ring), 7.77, 7.84 (2 d, J = 8.0 Hz, 2H, 2α-H of benzene ring) ppm. 13C{1H} NMR (100 MHz, CDCl3): 15.5 (s, CH3 attached to benzothiophene ring), 26.6, 26.9 (2 s, CH(CH3)2), 43.7 (s, SCH), 121.7−143.6 (m, C8H4S), 208.7, 209.6, 213.2 (3 s, CO), 291.0 (s, CO) ppm. Preparation of (μ-sec-BuS)(μ-2-MeC8H4S-3-CO)Fe2(CO)6 (18). The same procedure was followed as for 1, but the in situ prepared solution of A·[Et3NH] (R = sec-Bu) from sec-BuSH (0.055 mL, 0.5 mmol) and 3-iodo-2-methylbenzo[b]thiophene (0.206 g, 0.75 mmol) were employed in place of the A·[Et3NH] (R = i-Pr) solution and PhI, respectively. From the first red band, (μ-sec-BuS)2Fe2(CO)6 (0.014 g, 12%) was obtained. From the second red band, 18 (0.136 g, 50%) was obtained as a red solid (1/1 a/e isomer mixture by 1H NMR), mp 86− 88 °C. Anal. Calcd for C20H16Fe2O7S2: C, 44.14; H, 2.96. Found: C, 44.04; H, 3.05. IR (KBr disk): νCO 2069 (s), 2034 (vs), 1988 (vs), 1972 (s); νCO 1495 (m) cm−1. 1H NMR (400 MHz, CDCl3): 1.08, 1.13 (2t, J = 7.4 Hz, 3H, CHCH2CH3), 1.48 (d, J = 6.4 Hz, a-isomer, CHCH3), 1.59 (d, J = 6.4 Hz, e-isomer, CHCH3), 1.74−2.00 (m, 2H, CH2CH3), 2.44−2.50 (m, 4H, SCH, CH3 attached to benzothiophene ring), 7.21−7.37, 7.62−7.73 (2 m, 4H, C6H4) ppm. 13C{1H} NMR (100 MHz, CDCl3): 11.6−49.5 (m, CH3CHCH2CH3, CH3), 121.7− 143.7 (m, C8H4S), 208.7, 208.8, 209.7, 209.8, 213.1, 213.2 (6 s, C O), 291.0 (s, a-isomer, CO), 291.5 (s, e-isomer, CO) ppm. Preparation of (μ-i-PrS)(μ-1-Me-2-MeC8H4N-3-CO)Fe2(CO)6 (19). The same procedure was followed as for 1, except that 3-iodo-1methyl-2-methylindole (0.203 g, 0.75 mmol) was used in place of PhI. From the first red band, (μ-i-PrS)2Fe2(CO)6 (0.018 g, 17%) was obtained. From the second red band, 19 (0.114 g, 43%) was obtained as a red solid (1/15 a/e isomer mixture by 1H NMR), mp 135 °C dec. Anal. Calcd for C20H17Fe2NO7S: C, 45.57; H, 3.25; N, 2.66. Found: C, 45.49; H, 3.38; N, 2.86. IR (KBr disk): νCO 2066 (vs), 2021 (vs), 1989 (vs), 1961 (s); νCO 1490 (m) cm−1. 1H NMR (400 MHz, CD2Cl2): 1.51, 1.62 (2d, J = 6.8 Hz, 6H, CH(CH3)2), 2.52 (s, 3H, CH3 attached to indole ring), 2.64−2.71 (m, 1H, SCH), 3.63 (s, eisomer, NCH3), 3.67 (s, a-isomer, NCH3), 7.25−7.32, 8.06−8.09 (2m, 4H, C6H4) ppm. 13C{1H} NMR (100 MHz, CD2Cl2): 13.1, 13.4 (2 s, CH3 attached to indole ring), 26.0, 26.6, 27.2, 27.8 (4 s, CH(CH3)2), 30.0, 30.1 (2 s, NCH3), 37.0 (s, a-isomer, SCH), 43.8 (s, e-isomer, SCH), 109.8−142.6 (m, C8H4N), 209.1, 210.6, 211.4, 212.0, 214.3, 214.8 (6 s, CO), 270.5 (s, e-isomer, CO), 272.6 (s, a-isomer, C O) ppm. Preparation of (μ-cy-C6H11)(μ-1-Me-2-MeC8H4N-3-CO)Fe2(CO)6 (20). The same procedure was followed as for 1, but the in situ prepared solution of A·[Et3NH] (R = cy-C6H11) from cy-C6H11SH (0.061 mL, 0.5 mmol) and 3-iodo-1-methyl-2-methylindole (0.203 g, 0.75 mmol) were used in place of the A·[Et3NH] (R = i-Pr) solution and PhI, respectively. From the first red band, (μ-cyC6H11S)2Fe2(CO)6 (0.030 g, 24%) was obtained. From the second red band, 20 (0.128 g, 45%) was obtained as a red solid (1/5 a/e isomer mixture by 1H NMR), mp 152 °C dec. Anal. Calcd for C23H21Fe2NO7S: C, 48.71; H, 3.73; N, 2.47. Found: C, 48.57; H, 3.57; N, 2.50. IR (KBr disk): νCO 2065 (s), 2021 (vs), 1985 (vs), 1952 (s); 1738


Article

Organometallics using the geometric method. Details of crystal data, data collection, and structure refinement are summarized in Tables 5−7.

Table 7. Crystal Data and Structure Refinement Details for A·[Et3NH] (R = i-Pr, sec-Bu, cy-C6H11) A·[Et3NH]

Table 5. Crystal Data and Structure Refinement Details for 2, 7, and 10 mol formula mol wt cryst syst space group a/Å b/Å c/Å α/deg β/deg γ/deg V/Å3 Z Dc/g cm−3 abs coeff/mm−1 F(000) index ranges

no. of rflns no. of indep rflns 2θmax/deg R Rw goodness of fit largest diff peak, hole/e Å−3

2

7

10

C16H11BrFe2O7S 538.92 monoclinic P21/c 9.1537(18) 22.628(5) 9.874(2) 90 94.09(3) 90 2040.1(7) 4 1.755 3.516 1064 −12 ≤ h ≤ 12 −30 ≤ k ≤ 30 −13 ≤ l ≤ 13 26992 5425 58.24 0.0485 0.1126 1.003 0.770, −0.723

C19H18Fe2O7S 502.09 monoclinic P21/n 8.5137(17) 34.780(7) 14.863(3) 90 105.20(3) 90 4247.0(15) 8 1.571 1.501 2048 −10 ≤ h ≤ 11 −42 ≤ k ≤ 45 −19 ≤ l ≤ 19 35543 10107 55.90 0.0384 0.0898 1.159 0.379, −0.605

C20H12Fe2O7S 508.06 monoclinic P21/c 21.648(2) 10.9504(11) 18.1944(18) 90 95.296(3) 90 4294.6(7) 8 1.572 1.486 2048 −28 ≤ h ≤ 27 −14 ≤ k ≤ 14 −23 ≤ l ≤ 22 73525 9919 55.18 0.0508 0.0874 1.059 0.344, −0.393

mol formula mol wt cryst syst space group a/Å b/Å c/Å α/deg β/deg γ/deg V/Å3 Z Dc/g cm−3 abs coeff/mm−1 F(000) index ranges


R = i-Pr

R = sec-Bu

R = cy-C6H11

C16H23Fe2NO7S 485.11 monoclinic P21/n 13.376(8) 11.910(7) 13.538(9) 90 95.474(9) 90 2147(2) 4 1.501 1.482 1000 −17 ≤ h ≤ 17 −15 ≤ k ≤ 15 −17 ≤ l ≤ 17 21122 5126

C17H25Fe2NO7S 499.14 monoclinic P21/n 8.8352(17) 24.754(5) 10.938(2) 90 92.084(4) 90 2390.5(8) 4 1.387 1.334 1032 −11 ≤ h ≤ 11 −31 ≤ k ≤ 31 −14 ≤ l ≤ 14 23680 5383

C19H27Fe2NO7S 525.18 monoclinic P21/n 8.9081(18)) 24.662(5) 11.073(2) 90 94.254(3) 90 2425.9(8) 4 1.438 1.318 1088 −10 ≤ h ≤ 7 −29 ≤ k ≤ 29 −13 ≤ l ≤ 13 12361 4278

55.82 0.0591 0.1720 1.105 1.045, −0.827

54.96 0.0592 0.1205 1.073 0.314, −0.374

50.00 0.0326 0.0824 1.023 0.728, −0.505

Table 6. Crystal Data and Structure Refinement Details for 14, 15, 17, and 20

mol formula mol wt cryst syst space group a/Å b/Å c/Å α/deg β/deg γ/deg V/Å3 Z Dc/g cm−3 abs coeff/mm−1 F(000) index ranges


14

15

17

20

C22H18Fe2O7S2 570.18 triclinic P1̅ 9.0089(18) 10.801(2) 12.333(3) 91.16(3) 92.53(3) 99.67(3) 1181.4(4) 2 1.603 1.445 580 −11 ≤ h ≤ 11 −14 ≤ k ≤ 12 −16 ≤ l ≤ 16 12139 5559 55.86 0.0293 0.0754 1.144 0.671, −0.662

C25H22Fe2O7S2 610.25 monoclinic P21/n 17.077(3) 9.1908(18) 18.698(4) 90 116.77(3) 90 2620.1(9) 4 1.547 1.309 1248 −20 ≤ h ≤ 22 −12 ≤ k ≤ 12 −24 ≤ l ≤ 24 26017 6247 55.96 0.0456 0.0998 1.043 0.816, −0.611

C19H14Fe2O7S2 530.12 orthorhombic, Pbcn 21.663(4) 12.539(3) 15.187(3) 90 90 90 4125.5(14) 8 1.707 1.648 2144 −28 ≤ h ≤ 28 −16 ≤ k ≤ 10 −19 ≤ l ≤ 19 37391 4916 55.74 0.0282 0.0602 1.088 0.380, −0.447

C23H21Fe2NO7S 567.17 triclinic P1̅ 8.7333(17) 15.600(3) 19.086(4) 109.39(3) 95.97(3) 98.96(3) 2388.9(8) 4 1.577 1.346 1160 −11 ≤h ≤ 11 −20 ≤k ≤ 20 −25 ≤l ≤ 25 26474 11217 55.64 0.0377 0.0721 1.120 0.410, −0.560

1739


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Organometallics

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ASSOCIATED CONTENT

S Supporting Information *

CIF files giving crystallographic data for 2, 7, 10, 14, 15, 17, 20, and A·[Et3NH] (R = i-Pr, sec-Bu, cy-C6H11). The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.organomet.5b00228.

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AUTHOR INFORMATION

Corresponding Author

*E-mail for L.-C.S.: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We are grateful to the Ministry of Science and Technology of China (973 programs 2014CB845604 and 2011CB935902) and the National Natural Science Foundation of China (21132001, 21272122, 21472095) for financial support of this work.

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REFERENCES

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Palladium-Catalyzed Reactions of [Et3NH]+ Salts of [(Î¼-RS)(Î¼-CO

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