Article pubs.acs.org/Organometallics
Several New [Fe]Hydrogenase Model Complexes with a Single Fe Center Ligated to an Acylmethyl(hydroxymethyl)pyridine or Acylmethyl(hydroxy)pyridine Ligand Li-Cheng Song,* Fu-Qiang Hu, Gao-Yu Zhao, Ji-Wei Zhang, and Wei-Wei Zhang Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, China Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300072, China S Supporting Information *
ABSTRACT: We have developed two novel synthetic methods, by which two types of mononuclear Fe model complexes for the active site of [Fe]hydrogenase are successfully synthesized. The first type of 2-acylmethyl-6-hydroxymethylpyridine-containing complexes, [2-COCH2-6-HOCH2C5H3N]Fe(CO)2G (1, G = PhCO2; 2, PhCOS; 3, PhCS2; 4, 2-S-6MeC5H3N), were prepared by a “one-pot” method involving reaction of 2-TsO-6HOCH2C5H3N (Ts = 4-MeC6H4SO2) with Na2Fe(CO)4 followed by treatment of the resulting Fe(0) intermediate [Na(2-CH2-6-HOCH2C5H3N)Fe(CO)4] (M1) with (PhCO2)2, (PhCOS)2, (PhCS2)2, and (2-S-6-MeC5H3N)2 in 49−72% yields, respectively. The second type of 2-acylmethyl-6hydroxypyridine-containing complexes, (2-COCH2-6-HOC5H3N)Fe(CO)2(2-SCO-6-RC5H3N) (9a, R = MeO; 9b, R = PhS), could be prepared via a multiple-step synthetic method. This method involves (i) treatment of 2-ClCO-6-RC5H3N (R = MeO, PhS) with NaSH followed by acidification with diluted HCl to give 2-HSCO-6-RC5H3N (5a, R = MeO; 5b, R = PhS); (ii) further treatment of 5a,b with KOH to afford 2-KSCO-6-RC5H3N (6a, R = MeO; 6b, R = PhS); (iii) treatment of 2-TsOCH2-6PMBOC5H3N (PMB = 4-MeOC6H4CH2) with Na2Fe(CO)4 followed by treatment of the resulting Fe(0) intermediate [Na(2CH2-6-PMBOC5H3N)Fe(CO)4] (M2) with Br2 or I2 to produce (2-COCH2-6-PMBOC5H3N)Fe(CO)3X (7a, X = Br; 7b, X = I); (iv) further treatment of 7a,b with 6a,b to yield (2-COCH2-6-PMBOC5H3N)Fe(CO)2(2-S-6-RC5H3N) (8a, R = MeO; 8b, R = PhS); and (v) finally, removal of the PMB groups from 8a,b under the action of deprotecting reagent CF3CO2H/EtSH to give complexes 9a,b. All compounds 1−4 and 5a,b−9a,b with the exception of 7b are new and have been characterized by elemental analysis, spectroscopy, and, particularly for 1, 4, and 7a−9a, X-ray crystallography.
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INTRODUCTION
iron center that is ligated to a cysteine S atom, two cis-terminal carbonyls, a bidentate 2-acylmethyl-6-hydroxypyridine moiety, and an as yet unknown ligand, which is probably a molecule of water (Scheme 2a). Since the successful elucidation of the active site structure of [Fe]hydrogenase, many biomimetic models for the active site of [Fe]hydrogenase have been prepared and structurally characterized.5,6,13−28 Among the previously reported model complexes, those with a 2-acylmethyl-6-hydroxymethylpyridine ligand prepared by us24 and particularly those with a 2-
[Fe]Hydrogenase (also known as Hmd) is the third hydrogenase that was discovered two decades ago by Thauer and coworkers from Methanothermobacter marburgensis.1 In contrast to the other two redox-active hydrogenases, [FeFe] and [NiFe]hydrogenases,2−4 [Fe]hydrogenase5,6 is not a redox-active enzyme that can catalyze the heterolytic cleavage of dihydrogen in the presence of methenyl-H4MPT+ to give methyleneH4MPT and a proton (Scheme 1). Spectroscopic7−9 and particularly X-ray crystallographic studies10−12 have revealed that the active site of [Fe]hydrogenase contains a unique single
Scheme 2. (a) Proposed Structure for the Active Site of [Fe]Hydrogenase and (b) Two Types of the Targeted Model Complexes, A and B
Scheme 1. Heterolytic Cleavage of Dihydrogen Catalyzed by [Fe]Hydrogenase
Received: September 10, 2014
© XXXX American Chemical Society
A
dx.doi.org/10.1021/om5009296 | Organometallics XXXX, XXX, XXX−XXX
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acymethyl-6-hydroxypyridine ligand prepared by Chen and Hu25 are of great interest. This is because the natural Hmd enzyme contains a 2-acylmethyl-6-hydroxypyridine moiety, and the hydroxy group in this moiety was reported to play an important role in the activation of dihydrogen.29,30 To further develop the synthetic methodology for the preparation of such [Fe]hydrogenase models and to get a deeper understanding of the structure and catalytic function of [Fe]hydrogenase, we decided to study the synthetic methods and structures for two types of the new Hmd models, one with a general formula of (2-COCH2-6-HOCH2C5H3N)Fe(CO)2G (A) and the other with a general formula of (2-COCH2-6-HOC5H3N)Fe(CO)2(2-SCO-6-RC5H4N) (B) (Scheme 2b). Now we wish to report the synthetic methods and structural characterization for the four new targeted type A (G = PhCO2, PhCOS, PhCS2, 2-S-6MeC5H3N) model complexes and the two new targeted type B (R = MeO, PhS) model complexes. In addition, the new precursor compounds used for the preparation of these targeted model complexes are also described.
Scheme 3. Synthesis of the Targeted Type A Model Complexes 1−4
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RESULTS AND DISCUSSION Synthesis and Structural Characterization of the Targeted Type A Model Complexes: [2-COCH2-6HOCH2C5H3N]Fe(CO)2G (1, G = PhCO2; 2, PhCOS; 3, PhCS2; 4, 2-S-6-MeC5H3N). On the basis of preparing the first example of a type A model complex with G = MeCOS,24 we further found that the four new targeted type A model complexes 1−4 could be prepared by a more convenient method involving two continuous steps carried out in one pot. As shown in Scheme 3, the first step of this method includes a nucleophilic substitution reaction of the disubstituted pyridine derivative 2-(TsOCH2)-6-HOCH2C5H3N with Collman’s reagent Na2Fe(CO)4·1.5(1,4-dioxane) to give the intermediate Fe(0) complex M1.24 In the second step, the intermediate complex M1 reacted in situ with the O−O and S−S bondcontaining dimers (PhCO2)2, (PhCOS)2, (PhCS2)2, and (2-S6-MeC5H3N)2 to afford the corresponding O and S ligandcontaining Fe(II) complexes 1−4 in 49−72% yields, respectively. It follows that the second step of the reaction to give 1−4 is similar to formation of the previously reported halide complexes by reaction of M1 with Br2 or I2,24 which might be regarded as via a new type of intramolecular CO migratory insertion reaction of the intermediate M1 followed by the intra- and intermolecular CO displacements by its hydroxy group and the cationic moiety generated by heterolytic cleavage of the O−O or S−S bond of the corresponding starting dimers, respectively. Complexes 1−4 are air-stable solids, which have been characterized by elemental analysis, IR, 1H NMR, and 13C{1H} NMR spectroscopy. The IR spectra of 1−4 showed two absorption bands in the region 2036−1955 cm−1 for their two cis terminal CO ligands, one band in the range 1680−1660 cm−1 for their acyl groups and one band in the region 3380− 3305 cm−1 for their hydroxy groups.21,24 The 1H NMR spectra of 1−4 displayed one singlet in the range 5−15 ppm for their hydroxy group and one singlet or two doublets in the region 4.02−4.83 ppm for their CH2CO groups dependent upon if the two H atoms in each of the CH2CO groups are diastereotopic or not under the determined conditions. The 13 C{1H} NMR spectra of 1−4 exhibited a signal in the range 253−264 ppm for their acyl C atoms and two signals in the region 207−213 ppm for their terminal carbonyl C atoms.21,24
The molecular structures of 1 and 4 have been further confirmed by X-ray crystallographic study. The ORTEP drawings of 1 and 4 are depicted in Figures 1 and 2, whereas Table 1 gives their selected bond lengths and angles. The X-ray crystallographic studies revealed that 1 and 4 are isostructural
Figure 1. Molecular structure of 1 with 30% probability level ellipsoids. B
dx.doi.org/10.1021/om5009296 | Organometallics XXXX, XXX, XXX−XXX
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= PhS). 1. Synthesis and Characterization of Precursor Ligands 2-HSCO-6-RC5H3N (5a, R = MeO; 5b, R = PhS)/2KSCO-6-RC5H3N (6a, R = MeO; 6b, R = PhS) and Precursor Complexes (2-COCH2-6-PMBOC5H3N)Fe(CO)3X (7a, X = Br; 7b, X = I)/(2-COCH2-6-PMBOC5H3N)Fe(CO)2(2-S-6-RC5H3N) (8a, R = MeO; 8b, R = PhS). According to our designed synthetic route to the targeted model complexes 9a,b, we should first prepare the precursor ligands 5a,b and 6a,b starting from 2,6-disubstituted pyridine derivatives 2-ClCO-6-RC5H3N (R = MeO, PhS). Thus, as shown in Scheme 4, when the Scheme 4. Synthesis of Precursor Ligands 5a,b and 6a,b
starting pyridine derivatives were treated with a saturated aqueous solution of NaSH followed by acidification of the resulting mixture with diluted HCl, precursor ligands 5a,b could be obtained in 83% and 87% yields, respectively. However, when 5a,b were further treated in THF with KOH, precursor ligands 6a,b were obtained in an almost quantitative yield. Precursor ligands 5a,b and 6a,b are new and have been characterized by elemental analysis and various spectroscopic methods. For example, the IR spectra of 5a,b displayed one absorption band at 1664 and 1678 cm−1 for their carbonyl groups and the 1H NMR spectra exhibited one singlet at 5.76 and 6.32 ppm for their thiohydroxy groups, respectively. The 13 C{1H} NMR spectra of 5a,b showed a signal at 192.2 and 193.4 ppm for their carbonyl C atoms, respectively. Similarly, the IR spectra of 6a,b showed one absorption band at 1626 and 1673 cm−1 for their carbonyl groups, whereas the 13C{1H} NMR spectra of 6a,b displayed a signal at 213.3 and 207.1 ppm for their carbonyl C atoms. According to the designed synthetic route to model complexes 9a,b, the precursor complexes 7a,b and 8a,b should be also prepared. As shown in Scheme 5, the PMB-protected
Figure 2. Molecular structure of 4 with 30% probability level ellipsoids.
with the previously reported type A model complex with G = MeCOS. 24 Both 1 and 4 contain a 2-acylmethyl-6(hydroxymethyl)pyridine ligand that is coordinated to their Fe1 centers to construct two five-membered ferracycles through their acylmethyl C10 atoms and hydroxymethyl O3 atom, respectively. The two terminal CO ligands in 1 and 4 are located in the positions cis to their acyl ligands, whereas the benzoyloxy O5 atom in 1 and thiolate S1 atom in 4 occupy the positions trans to one of their two CO ligands. Particularly interesting is that the acyl ligands in 1 and 4 are trans to a weakly coordinated hydroxy group, which is exactly the same as the geometric arrangement between the acyl ligand and the weakly coordinated solvent H2O molecule in the natural enzyme.10,11 It follows that 1−4 are good models for the active site of [Fe]hydrogenase. Synthesis and Structural Characterization of the Targeted Type B Model Complexes (2-COCH 2 -6HOC5H3N)Fe(CO)2(2-SCO-6-RC5H3N) (9a, R = MeO; 9b, R
Table 1. Selected Bond Lengths (Å) and Angles (deg) for 1 and 4 1 Fe(1)−N(1) Fe(1)−C(1) Fe(1)−O(5) O(4)−C(10) C(10)−Fe(1)−O(3) N(1)−Fe(1)−O(3) C(4)−N(1)−C(8) N(1)−Fe(1)−C(10)
1.952 (4) 1.777(5) 1.982(3) 1.187(7) 161.7(2) 77.35(16) 121.9(5) 85.1(2)
Fe(1)−O(5) Fe(1)−C(10) N(1)−C(4) N(1)−C(11) C(10)−Fe(1)−O(5) C(2)−Fe(1)−O(3) C(11)−O(5)−Fe(1) C(9)−C(10)−Fe(1)
1.982(3) 1.915(5) 1.330(7) 1.3464(19) 86.0(2) 96.1(2) 128.0(3) 110.5(4)
4 Fe(1)−N(1) Fe(1)−C(1) Fe(1)−O(3) O(4)−C(10) C(2)−Fe(1)−S(1) C(11)−S(1)−Fe(1) C(3)−O(3)−Fe(1) N(1)−Fe(1)−O(3)
1.9529(14) 1.7734(18) 2.1285(11) 1.204(2) 174.84(5) 107.43(6) 112.35(9) 78.83(6)
Fe(1)−S(1) Fe(1)−C(10) S(1)−C(11) N(2)−C(11) C(1)−Fe(1)−N(1) C(10)−Fe(1)−O(3) O(4)−C(10)−Fe(1) C(10)−Fe(1)−N(1) C
2.3511(8) 1.9281(16) 1.7503(17) 1.3464(19) 171.78(6) 163.37(6) 130.39(14) 84.56(7)
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Scheme 5. Synthesis of Precursor Complexes 7a,b and 8a,b
Figure 3. Molecular structure of 7a with 30% probability level ellipsoids.
7a,b could be prepared by reaction of the disubstituted pyridine derivative 2-TsOCH2-6-PMBOC5H3N with Na2Fe(CO)4 · 1.5(1,4-dioxane) in MeCN followed by treatment of the resulting intermediate Fe(0) complex M227 with Br2 and I2 in 34% and 45% yields, respectively. The five-membered FeSC2N ferracycle-containing complexes 8a,b were further obtained by reaction of 7a with 6a or 7b with 6b in 73% and 92% yields, respectively. While 7b was previously reported in our communication,27 complexes 7a and 8a,b are new and have been characterized by elemental analysis and spectroscopy. The IR spectrum of 7a, similar to that of its analogue 7b, showed four absorption bands in the range 2095−1997 cm−1 for its terminal CO ligands and one band at 1677 cm−1 for its acyl group, whereas 8a,b displayed two absorption bands in the range 2026−1957 cm−1 for their CO ligands, one band at 1648 or 1658 cm−1 for their acyl groups, and one band at 1611 or 1612 cm−1 for their SC O groups, respectively. The 1H NMR spectrum of 7a is also similar to that of 7b by displaying one doublet at 4.23 ppm and one singlet at 4.94 ppm for the diastereotopic methylene H atoms in its CH2CO group and one singlet at 5.48 ppm for the methylene H atoms in its protecting PMB group, whereas 8a,b exhibited two doublets in the region 3.70−4.49 ppm for the diastereotopic methylene H atoms and one singlet in the region 4.35−4.92 ppm for the methylene H atoms in their protecting PMB groups. In addition, while the 13C{1H} NMR spectrum of 7a showed one signal at 257.1 ppm characteristic of its acyl C atom and three signals in the range 119.5−209.5 ppm assigned to its three terminal carbonyl C atoms, 8a,b displayed one acyl C atom at 266.8 and 263.7 ppm, two terminal carbonyl C atoms in the region 209.6−213.6 ppm, and one SCO carbonyl C atom at 202.6 and 201.6 ppm, respectively. The molecular structures of 7a and 8a have been unambiguously confirmed by X-ray crystallography. While their ORTEP drawings are shown in Figures 3 and 4, the selected bond lengths and angles are presented in Table 2. As shown in Figures 3 and 4, both Fe1 centers in 7a and 8a are sixcoordinate and their 2-acylmethyl-6-PMBO-disubstituted pyridine ligands each constitute a five-membered ferracycle with their Fe1 centers via N1/C4 and N1/C3 atoms, respectively. The three terminal CO ligands in 7a occupy the facial positions of the Fe1 octahedral geometry, while the two terminal CO ligands in 8a are located in positions cis to its acyl ligand. Particularly noteworthy is that in 8a another five-membered ferracycle is formed by its Fe1 center and the bidentate 2mercaptoacyl-6-methoxy-disubstituted pyridine ligand via N2 and S1 atoms. Actually, the structures of 7a and 8a are very similar to 7b and the four-membered FeSCN ferracycle-
Figure 4. Molecular structure of 8a with 30% probability level ellipsoids.
containing Fe(II) complex (2-COCH2-6-PMBOC5H3N)Fe(CO)2(2-SC5H4N),27 respectively. 2. Synthesis and Characterization of the Targeted Model Complexes (2-COCH2-6-HOC5H3N)Fe(CO)2(2-SCO-6-RC5H3N) (9a, R = MeO; 9b, R = PhS). Finally, the targeted model complexes 9a,b were successfully prepared by removal of the protecting PMB groups from complexes 8a,b under the action of the combined deprotecting reagent CF3CO2H/EtSH31,32 in 43% and 45% yields, respectively (Scheme 6). It is worth pointing out that the presence of EtSH in the combined deprotecting reagent facilitated removal of the PMB groups from 8a,b (presumably due to formation of EtSPMB, which is more stable than CF3CO2PMB) and thus improved the yields of 9a,b. Previously, we communicated that the preparation of the 2acylmethyl-6-hydroxypyridine-containing model complex D was attempted by using the single deprotecting reagent CF3CO2H to remove the protecting PMB group from its precursor complex C; as a result, we did not get the expected mononuclear iron model complex D; instead, a dinuclear iron complex E with a 2-acylmethyl-6-hydroxypyridine ligand was obtained (Scheme 7).27 It is believed that the unexpected production of E is most likely due to the high instability of the four-membered FeSCN ferracycle in complex D relative to the corresponding FeSC2N five-membered ferracycle in complexes 9a,b. Therefore, the four-membered FeSCN ferracycle in one molecule of D could be opened by nucleophilic attack at its Fe center by the hydroxy group oxygen atom of another molecule of D and then via the intramolecular coordination of the D
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Table 2. Selected Bond Lengths (Å) and Angles (deg) for 7a and 8a 7a Fe(1)−C(1) Fe(1)−C(4) Fe(1)−N(1) Fe(1)−Br(1) C(1)−Fe(1)−C(4) C(3)−Fe(1)−N(1) C(2)−Fe(1)−C(1) C(1)−Fe(1)−Br(1)
1.910(4) 1.977(4) 2.041(3) 2.4752(8) 171.27(18) 170.79(16) 99.30(19) 87.26(13)
Fe(1)−C(1) Fe(1)−C(3) Fe(1)−N(1) Fe(1)−S(1) C(1)−Fe(1)−C(2) C(1)−Fe(1)−N(1) C(2)−Fe(1)−S(1) C(3)−Fe(1)−N(2)
1.800(5) 1.942(5) 2.085(3) 2.358(2) 92.08(19) 174.74(17) 176.23(15) 166.27(15)
O(4)−C(4) Fe(1)−C(2) Fe(1)−C(3) N(1)−C(6) O(4)−C(4)−Fe(1) C(4)−Fe(1)−N(1) C(4)−Fe(1)−Br(1) C(6)−N(1)−Fe(1)
1.211(5) 1.777(4) 1.787(4) 1.358(5) 128.4(3) 82.90(14) 84.01(11) 115.0(2)
O(3)−C(3) Fe(1)−N(2) C(5)−N(1) C(19)−N(2) C(4)−C(3)−Fe(1) C(18)−S(1)−Fe(1) C(5)−N(1)−Fe(1) C(3)−Fe(1)−N(1)
1.246(5) 2.100(4) 1.382(5) 1.375(5) 111.1(3) 95.93(15) 113.1(3) 82.34(16)
8a
ppm for the two diastereotopic H atoms in their acylmethyl groups, whereas the 13C{1H} NMR spectra displayed one signal at 267.4 or 264.5 ppm for their acyl C atoms, respectively. These NMR data are also very close to those of both terminal CO- and acylmethylpyridine-containing model complexes.21,24,27 Particularly worth noting is that the 1H NMR spectra of 9a,b, similar to those of 2-acylmethyl-6-hydroxypyridine ligand-containing complexes,25,27 exhibited a singlet at 10.08 and 11.62 ppm for their hydroxy groups directly attached to their pyridine rings. However, the two singlets for 9a,b immediately disappeared when D2O was added, apparently due to the rapid D/H exchange between 9a,b and D2O. The molecular structure of 9a has been unequivocally confirmed by X-ray diffraction analysis (Figure 5, Table 3). It should be noted that 9a is the first crystallographically characterized mononuclear iron Hmd model complex with an acylmethyl(hydroxy)pyridine ligand, although a few of this type of model complexes have been prepared and spectroscopically characterized by Chen and Hu.25 As can be seen clearly in
Scheme 6. Synthesis of the Targeted Type B Model Complexes 9a,b
Scheme 7. Brief Description of the Suggested Pathway for Formation of Dinuclear Complex E from the PMB-Protected Mononuclear Complex C
corresponding heteroatoms to the Fe centers followed by loss of one molecule of mercaptopyridine to give dinuclear complex E (for a detailed description of the suggested pathway for formation of E from D, see the Supporting Information of the previous communication).27 The targeted model complexes 9a,b have been characterized by elemental analysis, IR, 1H NMR, and 13C{1H} NMR spectroscopy. The IR spectra of 9a,b displayed two absorption bands in the range 2027−1966 cm−1 for their terminal CO ligands and one absorption band at 1654 and 1625 cm−1 for their acyl groups, which are very close to those of both previously reported terminal CO- and acylmethylpyridinecontaining model complexes.21,24,27 The 1H NMR spectra of 9a,b showed two doublets at 3.83 and 4.30 or 3.92 and 4.35
Figure 5. Molecular structure of 9a with 30% probability level ellipsoids. E
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Table 3. Selected Bond Lengths (Å) and Angles (deg) for 9a Fe(1)−C(1) Fe(1)−C(10) Fe(1)−N(2) Fe(1)−S(1) C(10)−Fe(1)−N(2) C(1)−Fe(1)−N(1) C(2)−Fe(1)−S(1) C(1)−Fe(1)−C(2)
1.770(12) 1.943(12) 2.107(10) 2.311(3) 83.0(4) 91.2(4) 1718(4) 91.3(5)
C(16)−O(6) Fe(1)−N(1) C(10)−O(5) S(1)−C(9) C(10)−Fe(1)−N(1) N(1)−Fe(1)−N(2) S(1)−Fe(1)−N(2) Fe(1)−S(1)−C(9)
1.320(13) 2.109(9) 1.219(14) 1.708(11) 170.9(4) 96.6(3) 88.8(3) 100.3(4)
indicates that (i) the most striking structural feature for 9a is to have a 2-acylmethyl-6-hydroxypyridine ligand that is coordinated to its Fe(II) center via its acyl C atom and pyridyl N atom to form a five-membered ferracycle; (ii) the second striking feature of 9a is, similar to 1 and 4, to have two terminal CO ligands cis to its acyl C atom; and (iii) the third feature of 9a is, different from 1 and 4, to contain another five-membered ferracycle constructed by coordination of the negatively charged S atom and the lone pair electrons on the N atom of the 2-mercaptoacyl-6-methoxypyridinate ligand with its Fe(II) center. It follows that the first and second types of targeted model complexes 1−4 and 9a,b are good structural models for the active site of [Fe]hydrogenase.
Figure 5, 9a indeed contains a 2-acylmethyl-6-hydroxypyridine ligand that is coordinated to an Fe center via its acyl C10 and pyridyl N2 atoms to form a five-membered ferracycle. The Fe1 center is also coordinated to the 2-mercaptoacyl-6-methoxypyridine S1 and N1 atoms to generate another five-membered ferracycle. The C16−O6 bond length (1.321 Å) associated with the free hydroxy group of 9a is almost identical with the corresponding one (1.323 Å) in the previously reported dinuclear iron complex E.27 Finally, it should be noted that (i) although model complexes 9a,b, with a 2-acylmethyl-6-hydroxypyridine ligand are of particular interest, the blocking of the solvato site on the Fe center by an extra pyridine ligand is unlikely to allow H2 binding/activation, and (ii) the formal oxidation state for the iron centers of model complexes 9a,b should be assigned as +2, since there are two negative ligands around their iron centers. This is in good agreement with the recent assignment of lowspin Fe(II) for the iron center of [Fe]hydrogenase.33,34
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EXPERIMENTAL SECTION
General Comments. All reactions were carried out using standard Schlenk and vacuum-line techniques under an atmosphere of highly purified nitrogen or argon. MeCN and CH2Cl2 were distilled under N2 from CaH2, while THF, from sodium/benzophenone ketyl. 2TsOCH2-6-PMBOC5H3N27 (PMB = 4-MeOC6H4CH2), Benzoyl persulfide,35 thiobenzoyl persulfide,36 2,2′-dithio-6,6′-dimethylpyridine,37 2-TsOCH2-6-HOCH2C5H3N (Ts = 4-MeC6H4SO2),38 2ClCO-6-RC5H3N (R = MeO, PhS),39 and Na2Fe(CO)4·1.5(1,4dioxane),40 were prepared according to the published methods. Benzoyl peroxide and other materials were available commercially and used as received. 1H and 13C{1H} NMR spectra were obtained on a Bruker Avance 400 NMR spectrometer. Elemental analyses were performed on an Elementar Vario EL analyzer. IR spectra were recorded on a Bruker Vector 22 infrared spectrophotometer. Melting points were determined on an SGW X-4 microscopic melting point apparatus and are uncorrected. Preparation of (2-COCH2-6-HOCH2C5H3N)Fe(CO)2(PhCO2) (1). To a stirred suspension of Na2Fe(CO)4·1.5(1,4-dioxane) (0.346 g, 1.0 mmol) in MeCN (20 mL) cooled to 0 °C was added 2-TsOCH2-6HOCH2C5H3N (0.293 g, 1.0 mmol), and then the mixture was stirred at this temperature for 0.5 h. After benzoyl peroxide (0.242 g, 1.0 mmol) was added, the new mixture was stirred at 0 °C for 0.5 h. After volatiles were removed at reduced pressure, the residue was subjected to column chromatography (silica gel) under anaerobic conditions. Elution with petroleum ether/acetone (2:1, v/v) developed a major yellow band, from which 1 (0.300 g, 72%) was obtained as a yellow solid, mp 87 °C (dec). Anal. Calcd for C17H13FeNO6·0.5CH2Cl2: C, 49.39; H, 3.32; N, 3.29. Found: C, 49.32; H, 3.19; N 3.37. IR (KBr disk): νOH 3380 (w), νCO 2036 (vs), 1965 (vs), νCH2CO 1680 (s), νOCO 1599 (s) cm−1. 1H NMR (400 MHz, d6-acetone): 4.47, 4.78 (dd, AX system, J = 20.8 Hz, 2H, CH2CO), 5.25, 5.38 (dd, AB system, J = 16.8 Hz, 2H, CH2OH), 7.32 (t, J = 7.4 Hz, 2H, 3-H/5-H of C6H5), 7.43 (t, J = 7.2 Hz, 1H, 4-H of C6H5), 7.58 (d, J = 7.2 Hz, 1H, 3-H of C5H3N), 7.71 (d, J = 7.6 Hz, 1H, 5-H of C5H3N), 7.81 (d, J = 7.6 Hz, 2H, 2-H/6-H of C6H5), 8.07 (t, J = 7.4 Hz, 1H, 4-H of C5H3N), 12.24 (s, 1H, OH) ppm. 13C{1H} NMR (100 MHz, d6-acetone): 62.8 (CH2CO), 68.4 (CH2OH), 118.4, 120.6, 129.1, 131.2, 135.1, 139.6, 159.9, 160.9 (C5H3N, C6H5), 178.1 (OCO), 208.3, 209.4 (CO), 253.4 (CH2CO) ppm. Preparation of (2-COCH2-6-HOCH2C5H3N)Fe(CO)2(PhCOS) (2). The same procedure was followed as for 1, except that benzoyl
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CONCLUSIONS We have successfully synthesized two closely related types of new Hmd model complexes, one with a 2-acylmethyl-6hydroxymethylpyridine ligand and the other with a 2acylmethyl-6-hydroxypyridine ligand by two novel synthetic methods. The first type of targeted model complexes (1−4) are prepared by a simple and convenient one-pot method involving reaction of the disubstituted pyridine derivative 2-TsOCH2-6HOCH2C5H3N with Na2Fe(CO)4 followed by treatment of the resulting Fe(0) intermediate M1 with (PhCO2)2, (PhCOS)2, (PhCS2)2, and (2-S-6-MeC5H3N)2 in good yields. The second type of targeted model complexes (9a,b) are prepared by a multiple-step synthetic method, which involves the following three main reaction steps: (i) the nucleophilic substitution reaction of 2-TsOCH2-6-PMBOC5H3N with Na2Fe(CO)4 followed by treatment of the resulting Fe(0) intermediate M2 with Br2 or I2 to give the halogenated precursor complexes 7a,b; (ii) treatment of 7a,b with precursor ligands 6a,b to give the five-membered FeSC2N ferracycle-containing precursor complexes 8a,b; and (iii) finally, removal of the protecting PMB groups from 8a,b in the presence of deprotecting reagent CF3CO2H/EtSH to give complexes 9a,b. The X-ray crystallographic study on the first type of models 1 and 4 reveals that (i) the most prominent structural feature for 1 and 4 is for each to have a 2-acylmethyl-6-hydroxymethylpyridine ligand that is coordinated to their Fe(II) centers to construct two fivemembered ferracycles via their acyl C atom, pyridyl N atom, and hydroxymethyl O atom; (ii) another prominent feature is for each to have two terminal CO ligands cis to their acyl groups; and (iii) the third feature for 1 and 4 is that the benzoyloxy ligand in 1 and the 2-mercapto-6-methylpyridinate ligand in 4 are trans to one of the two CO ligands. Another Xray crystallographic study on the second type of model 9a F
dx.doi.org/10.1021/om5009296 | Organometallics XXXX, XXX, XXX−XXX
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KOH (0.280 g, 5 mmol), and then the mixture was stirred at room temperature for 0.5 h. Solvent was removed at reduced pressure, and then the residue was washed thoroughly with Et2O (20 mL) to give 6a (1.014 g, 98%) as a yellowish solid, mp 138−139 °C. Anal. Calcd for C7H6KNO2S: C, 40.56; H, 2.92; N, 6.76. Found: C, 40.35; H, 3.04; N, 6.54. IR (KBr disk): νCO 1626 (m) cm−1. 1H NMR (400 MHz, D2O): 3.89 (s, 3H, CH3), 6.89 (d, J = 8.0 Hz, 1H, 3-H of C5H3N), 7.63 (d, J = 7.6 Hz, 1H, 5-H of C5H3N), 7.74 (t, J = 8.0 Hz, 1H, 4-H of C5H3N) ppm. 13C{1H} NMR (100 MHz, D2O): 54.0 (CH3), 115.5, 116.4, 140.4, 156.5, 163.0 (C5H3N), 213.3 (CO) ppm. Similarly, when 5b (1.240 g, 5.0 mmol) was employed in place of 5a, compound 6b (1.382 g, 97%) was obtained as an orange solid, mp 31−32 °C. Anal. Calcd for C12H8KNOS2: C, 50.50; H, 2.83; N, 4.91. Found: C, 50.38; H, 2.98; N, 4.95. IR (KBr disk): νCO 1673 (m) cm−1. 1H NMR (400 MHz, d6-DMSO): 6.50−6.80, 7.30−7.80 (2m, 8H, C6H5 and C5H3N) ppm. 13C{1H} NMR (100 MHz, d6-DMSO): 119.6, 120.2, 129.5, 130.4, 130.5, 131.7, 134.6, 137.3, 158.4 (C6H5 and C5H3N), 207.1 (CO) ppm. Preparation of (2-COCH2-6-PMBOC5H3N)Fe(CO)3X (7a, X = Br; 7b, X = I). To a stirred suspension of Na2Fe(CO)4·1.5(1,4dioxane) (0.346 g, 1.0 mmol) in MeCN (20 mL) cooled to 0 °C was added 2-TsOCH2-6-PMBOC5H3N (0.399 g, 1.0 mmol), and then the mixture was stirred at this temperature for 0.5 h. After a solution of Br2 in CH2Cl2 (1.0 mL, 1 M, 1.0 mmol) was added dropwise, the new mixture was stirred at 0 °C for ca. 10 min to give a red solution. After volatiles were removed at reduced pressure, the residue was subjected to column chromatography (silica gel). Elution with petroleum ether/ acetone (2.5:1, v/v) developed a major red band, from which 7a (0.160 g, 34%) was obtained as a red solid, mp 108−109 °C. Anal. Calcd for C18H14FeBrNO6: C, 45.41; H, 2.96; N, 2.94. Found: C, 45.35; H, 3.15; N, 3.13. IR (KBr disk): νCO 2095 (vs), 2053 (vs), 2039 (vs), 1997 (vs), νCO 1677 (s) cm−1. 1H NMR (400 MHz, d6acetone): 3.85 (s, 3H, OCH3), 4.23 (d, J = 20.0 Hz, 1H of COCH2), 4.94 (br s, 1H of COCH2), 5.48 (s, 2H, OCH2), 7.01 (d, J = 8.0 Hz, 2H, 3,5-H of C6H4), 7.26 (d, J = 8.0 Hz, 1H, 5-H of C5H3N), 7.36 (d, J = 7.2 Hz, 1H, 3-H of C5H3N), 7.54 (d, J = 7.6 Hz, 2H, 2,6-H of C6H4), 8.07 (t, J = 7.6 Hz, 1H, 4-H of C5H3N) ppm. 13C{1H} NMR (100 MHz, d6-acetone): 55.7 (OCH3), 65.9 (CH2CO), 72.8 (OCH2), 106.9, 115.0, 116.5, 127.3, 131.3, 142.7, 161.2, 162.0, 165.4 (C5H3N, C6H4), 119.5, 208.8, 209.5 (CO), 257.1 (CH2CO) ppm. Similarly, when I2 (0.254 g, 1.0 mmol) was used in place of Br2, 7b (0.235 g, 45%) was obtained as a red-brown solid,27 mp 104−105 °C. Anal. Calcd for C18H14FeINO6: C, 41.33; H, 2.70; N, 2.68. Found: C, 41.51; H, 2.81; N, 2.83. IR (KBr disk): νCO 2085 (vs), 2037 (vs), 2005 (vs), 1969 (m), νCO 1672 (s) cm−1. 1H NMR (400 MHz, d6acetone): 3.82 (s, 3H, OCH3), 4.37, 5.12 (dd, J = 20.8 Hz, 2H, COCH2), 5.56 (s, 2H, OCH2), 7.00 (d, J = 8.4 Hz, 2H, 3,5-H of C6H4), 7.23 (d, J = 8.0 Hz, 1H, 5-H of C5H3N), 7.33 (d, J = 7.6 Hz, 1H, 3-H of C5H3N), 7.57 (d, J = 8.4 Hz, 2H, 2,6-H of C6H4), 7.98 (t, J = 8.0 Hz, 1H, 4-H of C5H3N) ppm. 13C{1H} NMR (100 MHz, d6acetone): 55.8 (OCH3), 68.7 (CH2CO), 72.8 (OCH2), 107.3, 115.0, 116.5, 127.2, 131.3, 142.7, 161.2, 162.0, 165.6 (C5H3N, C6H4), 200.9, 210.7, 211.0 (CO), 258.2 (CH2CO) ppm. Preparation of (2-COCH2-6-PMBOC5H3N)Fe(CO)2(2-SCO-6RC5H3N) (8a, R = MeO; 8b, R = PhS). A mixture of 6a (0.104 g, 0.5 mmol) and 7a (0.238 g, 0.5 mmol) in MeCN (10 mL) was stirred at 0 °C for 1.5 h. After volatiles were removed at reduced pressure, the residue was subjected to column chromatography (silica gel). Elution with petroleum ether/acetone (1.5:1, v/v) developed a main yellow band, from which 8a (0.195 g, 73%) was obtained as a yellow solid, mp 145−146 °C. Anal. Calcd for C24H20FeN2O7S: C, 53.75; H, 3.76; N, 5.22. Found: C, 53.56; H, 3.82; N, 5.42. IR (KBr disk): νCO 2026 (vs), 1966 (vs), νCH2CO 1648 (s), νSCO 1611 (s) cm−1. 1H NMR (400 MHz, d6-acetone): 3.68 (s, 3H, C6H4OCH3), 3.74, 4.20 (dd, J = 20.6 Hz, 2H, CH2CO), 3.98 (s, 3H, CH3OC5H3N), 4.35, 4.71 (dd, J = 12.8 Hz, 2H, CH2O), 6.61 (d, J = 8.4 Hz, 1H, 5-H of CH3OC5H3N), 6.80 (d, J = 8.8 Hz, 2H, 3,5-H of C6H4), 6.94−6.99 (m, 3H, 2,6-H of C6H4 and 3-H of CH3OC5H3N), 7.02 (d, J = 7.6 Hz, 1H, 3-H of PMBOC5H3N), 7.37 (d, J = 7.2 Hz, 1H, 5-H of PMBOC5H3N), 7.63 (t, J = 8.0 Hz, 1H, 4-H of CH3OC5H3N), 7.88 (t, J = 8.0 Hz, 1H, 4-H
persulfide (0.247 g, 1.0 mmol) was used instead of benzoyl peroxide. From the major yellow band 2 (0.273 g, 68%) was obtained as a yellow solid, mp 79 °C (dec). Anal. Calcd for C17H13FeNO5S: C, 51.15; H, 3.28; N, 3.51. Found: C, 51.31; H, 3.46; N 3.47. IR (KBr disk): νOH 3307 (w), νCO 2028 (vs), 1970 (vs), νCH2CO 1660 (s), νOCO 1605 (m) cm−1. 1H NMR (400 MHz, d6-acetone): 4.37 (s, 2H, CH2CO), 5.23, 5.35 (dd, AB system, J = 16.4 Hz, 2H, CH2OH), 7.38−7.63, 7.98−8.05 (2m, 8H, C5H3N, C6H5), 10.77 (s, 1H, OH) ppm. 13C{1H} NMR (100 MHz, d6-acetone): 64.3 (CH2CO), 68.8 (CH2OH), 118.5, 120.7, 127.7, 128.0, 132.5, 139.2, 140.8, 159.0, 159.5 (C5H3N, C6H5), 206.1 (SCO), 210.4, 212.1 (CO), 254.5 (CH2CO) ppm. Preparation of (2-COCH2-6-HOCH2C5H3N)Fe(CO)2(PhCS2) (3). The same procedure was followed as for 1, except that thiobenzoyl persulfide (0.248 g, 1.0 mmol) was utilized in place of benzoyl peroxide. From the major brown band 3 (0.284 g, 59%) was obtained as a brown solid, mp 66 °C (dec). Anal. Calcd for C17H13FeNO4S2: C, 49.17; H, 3.16; N, 3.37. Found: C, 49.22; H, 3.21; N 3.34. IR (KBr disk): νOH 3306 (w), νCO 2024 (vs), 1965 (vs), νCO 1660 (s) (m) cm−1. 1H NMR (400 MHz, d6-acetone): 4.02, 4.83 (dd, AX system, J = 20.0 Hz, 2H, CH2CO), 5.15−5.38 (m, 3H, CH2OH), 7.43 (t, J = 7.0 Hz, 2H, 3-H/5-H of C6H5), 7.54 (d, J = 7.2 Hz, 1H, 3-H of C5H3N), 7.62 (t, J = 7.2 Hz, 1H, 4-H of C6H5), 7.81 (d, J = 7.6 Hz, 1H, 5-H of C5H3N), 7.97 (d, J = 7.4 Hz, 1H, 4-H of C5H4N), 8.09 (d, J = 8.0 Hz, 2H, 2-H/6-H of C6H5) ppm. 13C{1H} NMR (100 MHz, d6-acetone): 62.1 (CH2CO), 66.6 (CH2OH), 120.6, 122.1, 123.7, 128.4, 133.8, 138.7, 143.1, 162.1, 164.9 (C5H3N, C6H5), 210.7, 210.9 (CO), 248.3 (CS), 263.3 (CH2CO) ppm. Preparation of (2-COCH2-6-HOCH2C5H3N)Fe(CO)2(2-S-6MeC5H3N) (4). The same procedure was taken as for 1, but 2,2′dithio-6,6′-dimethylpyridine (0.248 g, 1.0 mmol) was employed instead of benzoyl peroxide. From the major yellow band 4 (0.188 g, 49%) was obtained as a yellow solid, mp 123 °C (dec). Anal. Calcd for C16H14FeN2O4S: C, 49.76; H, 3.65; N, 7.25. Found: C, 49.57; H, 3.45; N, 7.19. IR (KBr disk): νOH 3305 (w), νCO 2019 (vs), 1955 (vs), νCO 1661 (s) cm−1. 1H NMR (400 MHz, d6-acetone): 2.37 (s, 3H, CH3), 4.22 (s, 2H, CH2CO), 5.15, 5.29 (dd, AB system, J = 16.8 Hz, 2H, CH2OH), 6.77 (d, J = 7.6 Hz, 1H, 5-H of SC5H3N), 7.10 (d, J = 8.0 Hz, 1H, 3-H of SC5H3N), 7.27 (t, J = 7.6 Hz, 1H, 4-H of SC5H3N), 7.48 (d, J = 7.6 Hz, 1H, 3-H of C5H3N), 7.62 (d, J = 7.6 Hz, 1H, 5-H of C5H3N), 7.99 (t, J = 7.6 Hz, 1H, 4-H of C5H3N), 14.61 (s, 1H, OH) ppm. 13C{1H} NMR (100 MHz, d6-DMSO): 21.7 (CH3), 64.1 (CH2CO), 67.3 (CH2OH), 116.7, 117.8, 120.0, 125.0, 136.3, 138.4, 154.9, 158.9, 161.2, 173.4 (C5H3N, SC5H3N), 207.3, 212.2 (CO), 255.3 (CH2CO) ppm. Preparation of 2-HSCO-6-RC5H3N (5a, R = MeO; 5b, R = PhS). To a saturated aqueous solution of NaSH (30 mL) was added 2ClCO-6-MeOC5H3N (1.720 g, 10.0 mmol), and then the mixture was stirred at room temperature overnight. After the mixture was acidified to pH = 3 with diluted HCl, it was extracted with dichloromethane (2 × 50 mL), and then the combined extracts were washed with water (50 mL) and dried over anhydrous magnesium sulfate. After removal of solvent, the residue was subjected to column chromatography (silica gel) under anaerobic conditions. Elution with CH2Cl2/MeOH (10:1, v/v) gave 5a (1.403 g, 83%) as a white solid, mp 74−75 °C. Anal. Calcd for C7H7NO2S: C, 49.69; H, 4.17; N, 8.28. Found: C, 49.58; H, 4.21; N, 8.17. IR (KBr disk): νCO 1664 (s) cm−1. 1H NMR (400 MHz, CDCl3): 4.01 (s, 3H, CH3), 5.76 (br s, 1H, SH), 6.97 (d, J = 8.0 Hz, 1H, 3-H of C5H3N), 7.56 (d, J = 7.2 Hz, 1H, 5-H of C5H3N), 7.71 (t, J = 7.2 Hz, 1H, 4-H of C5H3N) ppm. 13C{1H} NMR (100 MHz, CDCl3): 53.0 (CH3), 112.7, 115.6, 138.7, 147.2, 162.3 (C5H3N), 192.2 (CO) ppm. Similarly, when 2-ClCO-6-PhSC5H3N (2.497 g, 10.0 mmol) was used instead of 2-ClCO-6-MeOC5H3N, 5b was obtained (2.148 g, 87%) as a colorless oil. Anal. Calcd for C12H9NOS2: C, 58.27; H, 3.67; N, 5.66. Found: C, 58.09; H, 3.55; N, 5.77. IR (KBr disk): νCO 1678 (vs), cm−1. 1H NMR (400 MHz, CDCl3): 6.32 (br s, 1H, SH), 7.22−7.68 (m, 8H, C6H5 and C5H3) ppm. 13C{1H} NMR (100 MHz, CDCl3): 116.3, 125.2, 129.2, 129.7, 129.8, 135.8, 137.8, 149.8, 160.8 (C6H5 and C5H3N), 193.4 (CO) ppm. Preparation of 2-KSCO-6-RC5H3N (6a, R = MeO; 6b, R = PhS). To a solution of 5a (0.845g, 5.0 mmol) in THF (20 mL) was added G
dx.doi.org/10.1021/om5009296 | Organometallics XXXX, XXX, XXX−XXX
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of PMBOC5H3N) ppm. 13C{1H} NMR (100 MHz, d6-DMSO): 55.6 (CH3OC6H4), 57.1, (CH3OC5H3N), 64.4 (CH2CO), 69.8 (CH2O), 106.7, 110.6, 114.4, 115.5, 115.6, 127.1, 129.3, 130.2, 141.6, 142.3, 153.2, 159.6, 160.9, 165.4, 165.6 (C6H4 and 2C5H3N), 202.6 (SC O), 210.2, 213.6 (CO), 266.8 (CH2CO) ppm. Similarly, when a mixture of 6b (0.143 g, 0.5 mmol) and 7b (0.262 g, 0.5 mmol) in MeCN was stirred at 0 °C for 0.5 h, 8b (0.282, 92%) was obtained as a brown solid, mp 131−132 °C. Anal. Calcd for C29H22FeN2O6S2: C, 56.69; H, 3.61; N, 4.56. Found: C, 56.51; H, 3.43; N, 4.22. IR (KBr disk): νCO 2024 (vs), 1957 (vs), νCH2CO 1658 (vs, νSCO 1612 (vs) cm−1. 1H NMR (400 MHz, d6-acetone): 3.80 (s, 3H, CH3O), 3.97, 4.49 (dd, J = 20.8 Hz, 2H, CH2CO), 4.54, 4.92 (dd, J = 13.2 Hz, 2H, CH2O), 6.79 (d, J = 8.4 Hz, 1H, 5-H of PhSC5H3N), 6.87 (d, J = 8.0 Hz, 1H, 3-H of PhSC5H3N), 6.94 (d, J = 8.4 Hz, 2H, 3,5-H of C6H4), 7.19 (d, J = 7.6 Hz, 1H, 3-H of PMBOC5H3N), 7.27 (d, J = 8.8 Hz, 2H, 2,6-H of C6H4), 7.57−7.68 (m, 6H, C6H5 and 5-H of PMBOC5H3N), 7.75 (t, J = 7.8 Hz, 1H, 4-H of PhSC5H3N), 7.80 (t, J = 7.8 Hz, 1H, 4-H of PMBOC5H3N) ppm. 13C{1H} NMR (100 MHz, d6-DMSO): 55.6 (CH3OC6H4), 63.8 (CH2CO), 70.3 (CH2O), 106.9, 109.3, 114.1, 114.4, 115.9, 118.9, 125.9, 126.9, 129.6, 130.6, 131.0, 131.1, 135.4, 139.6, 142.0, 155.6, 159.4, 159.7, 160.8, 165.4, 166.6 (C6H5, C6H4 and 2C5H3N), 201.6 (SCO), 209.6, 213.0 (C O), 263.7 (CH2CO) ppm. Preparation of (2-COCH 2 -6-HOC 5H 3 N)Fe(CO) 2 (2-SCO-6RC5H3N] (9a, R = MeO; 9b, R = PhS). A solution of 8a (0.268 g, 0.5 mmol) in CH2Cl2 (8 mL) was cooled to 0 °C, and then CF3CO2H (0.8 mL, 10.6 mmol) and EtSH (0.2 mL) were added. The mixture continued to be stirred at 0 °C for 3 h. After volatiles were removed at reduced pressure, the residue was dissolved in acetone (6 mL), and then NaHCO3 (0.400 g, 4.8 mmol) was added to neutralize the residual CF3CO2H. The neutralized mixture was subjected to column chromatography (silica gel) by elution with petroleum ether/acetone (2:3, v/v) to give a yellow band, from which 9a (0.089 g, 43%) was obtained as an orange solid, mp 115 °C (dec). Anal. Calcd for C16H12FeN2O6S: C, 46.17; H, 2.91; N, 6.73. Found: C, 46.06; H, 3.15; N, 6.57. IR (KBr disk): νOH 3088 (m), νCO 2027 (vs), 1966 (vs), νCH2CO 1654 (s), νSCO 1587 (s) cm−1. 1H NMR (400 MHz, d6acetone): 3.83, 4.30 (dd, J = 20.4 Hz, 2H, CH2CO), 4.24 (s, 3H, CH3O), 6.58 (d, J = 8.4 Hz, 1H, 5-H of CH3OC5H3N), 7.07 (d, J = 7.2 Hz, 1H, 3-H of CH3OC5H3N), 7.35 (d, J = 8.0 Hz, 1H, 3-H of HOC5H3N), 7.51 (d, J = 7.2 Hz, 1H, 5-H of HOC5H3N), 7.68 (t, J = 7.8 Hz, 1H, 4-H of CH3OC5H3N), 8.09 (t, J = 7.8 Hz, 1H, 4-H of HOC5H3N), 10.08 (br s, 1H, OH) ppm. 13C{1H} NMR (100 MHz, d6-DMSO): 57.5 (CH3), 64.4 (CH2CO), 108.9, 110.7, 113.6, 115.4, 141.0, 142.4, 153.4, 159.6, 166.4 (2C5H3N), 202.8 (SCO), 210.3, 213.7 (CO), 267.4 (CH2CO) ppm. Similarly, when 8b (0.307 g, 0.5 mmol) was employed instead of 8a, compound 9b (0.111 g, 45%) was obtained as an orange solid, mp 157 °C (dec). Anal. Calcd for C21H14FeN2O5S2: C, 51.02; H, 2.85; N, 5.67. Found: C, 50.94; H, 2.89; N, 5.39. IR (KBr disk): νOH 3152 (s or m), νCO 2027 (vs), 1968 (vs), νCH2CO 1625 (s), νSCO 1606 (s) cm−1. 1H NMR (400 MHz, d6-DMSO): 3.92, 4.35 (dd, J = 21.2 Hz, 2H, CH2CO), 6.51 (d, J = 8.4 Hz, 1H of C5H3N), 7.00 (d, J = 6.0 Hz, 1H of C5H3N), 7.11 (d, J = 7.6 Hz, 1H of C5H3N), 7.58−7.69 (m, 7H, 2H of C5H3N and C6H5), 7.92 (t, J = 7.6 Hz, 1H of C5H3N), 11.62 (br s, 1H, OH) ppm. 13 C{1H} NMR (100 MHz, d6-DMSO): 63.8 (CH2CO), 109.1, 113.9, 119.2, 126.7, 130.8, 131.1, 131.6, 134.9, 139.7, 141.4, 155.8, 159.5, 166.3, 167.2 (C6H5 and 2C5H3N), 201.9 (SCO), 209.9, 213.2 (C O), 264.5 (CH2CO) ppm. X-ray Crystal Structure Determinations of 1, 4, 7a, 8a, and 9a. Single crystals of 1 and 4 suitable for X-ray diffraction analysis were grown by slow diffusion of hexane into their CH2Cl2 solutions at −4 °C, while single crystals of 7a and 8a were obtained by slow evaporation of their CH2Cl2/hexane solutions at −5 °C and those of 9a were obtained by slow evaporation of its DMF/acetone/hexane solution at room temperature. A single crystal of 1, 4, 7a, 8a, or 9a was mounted on a Rigaku MM-007 (rotating anode) diffractometer equipped with a Saturn 70CCD. Data were collected using a confocal monochromator with Mo Kα radiation (λ = 0.710 73) in the ω−ϕ scanning mode at 113 and 293 K, respectively. Data collection,
reduction, and absorption correction were performed with the CRYSTALCLEAR program.41 All the structures were solved by direct methods using the SHELXS-97 program42 and refined by full-matrix least-squares techniques (SHELXL-97)43 on F2. Hydrogen atoms were located using the geometric method. Details of crystal data, data collections, and structure refinements are summarized in Tables S1 and S2 (see the Supporting Information).
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ASSOCIATED CONTENT
S Supporting Information *
Full tables of crystal data, atomic coordinates and thermal parameters, and bond lengths and angles for 1, 4, 7a, 8a, and 9a as CIF files as well as Tables S1 and S2. 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 We are grateful to the Ministry of Science and Technology of China (973 Programs 2011CB935902 and 2014CB845604) and the National Natural Science Foundation of China (21132001, 21272122) for financial support of this work.
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REFERENCES
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