Article pubs.acs.org/Organometallics
(Pyrazol-1-yl)carbonyl and Ester-Functionalized Bis(pyrazol-1yl)methide Carbonyl Tungsten Complexes Jian-Peng Sun, Da-Wei Zhao, Hai-Bin Song, and Liang-Fu Tang* Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin),Tianjin 300071, People’s Republic of China S Supporting Information *
ABSTRACT: (3,5-Dimethylpyrazol-1-yl)carbonyl- and n-butoxycarbonyl-functionalized bis(3,5-dimethylpyrazol-1-yl)methide carbonyl tungsten derivatives were unexpectedly formed, together with a bis(3,5-dimethylpyrazol-1-yl)acyl carbonyl tungsten complex, upon sequential treatment of bis(3,5-dimethylpyrazol-1-yl)methane with n-BuLi, tungsten carbonyl, and iodine. The resulting complexes were fully characterized using IR and NMR spectroscopy, and their structures were unambiguously determined by X-ray crystallography.
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INTRODUCTION Heteroscorpionate ligands derived from bis(pyrazol-1-yl)methane have been used extensively in recent years in coordination and bioinorganic chemistry, as well as being applied to a variety of catalytic transformations.1 These ligands possess good donor properties and variable coordination modes, which allow them to form strong complexes with a wide variety of main-group and transition metals. Furthermore, the coordination behaviors of these ligands can be readily adjusted by making changes to the electronic and steric characteristics of the substituents on the pyrazolyl rings, as well as by changing the properties of the pendant arms. The deprotonation of the methylene bridge of bis(pyrazol-1yl)methane2 and the subsequent reaction of the resulting carbanionic species with various electrophilic reagents have been successfully exploited to synthesize these heteroscorpionate ligands.3 The results of our previous study showed that the modification of bis(pyrazol-1-yl)methane with organometallic functional groups on the methine carbon resulted in unusual types of reactivity.4 For example, the reaction of the tungsten carbonyl derivatives of trialkylstannylbis(3,5-dimethylpyrazol-1yl)methane with iodine resulted in the formation of novel bis(pyrazol-1-yl)acyl complexes.4a This result implied that pyrazolyl-based ligands could potentially be used to stabilize metal−acyl complexes, which are considered to be important active intermediates in many catalytic carbonylation processes.5 The development of a technique for capturing these active species is highly desirable, because it would allow for the elucidation of their structures and the development of a better understanding of their role in catalytic processes, which could be used to design improved catalysts. The treatment of metal carbonyls with organolithium reagents leads to the formation of the corresponding acylmetalates, which usually form Fischer © XXXX American Chemical Society
carbene complexes following their treatment with a hard electrophile.6 In contrast, the treatment of these acylmetalates with a soft electrophile results in the formation of metal−acyl complexes.6 As part of our ongoing interest in the reactivity of bis(pyrazol-1-yl)methide anion,7 we herein report the reaction of bis(pyrazol-1-yl)methyllithium with tungsten carbonyl, followed by the reaction of the resulting intermediate with iodine, which yielded unexpected (pyrazol-1-yl)carbonyl and ester-functionalized bis(pyrazol-1-yl)methide tungsten derivatives, together with bis(pyrazol-1-yl)acyl tungsten complexes.
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RESULTS AND DISCUSSION Reaction of Bis(3,5-dimethylpyrazol-1-yl)methyllithium with W(CO)6, Followed by Reaction with I2. Bis(3,5-dimethylpyrazol-1-yl)methyllithium was prepared by the reaction of bis(3,5-dimethylpyrazol-1-yl)methane with nBuLi at −70 °C.2a The subsequent treatment of this lithium salt with W(CO)6 followed by I2 yielded complexes 1−4 (Scheme 1). Complexes 1 and 2 have been reported previously, where they were readily obtained by the reaction of Cy3SnCH(3,5Me2Pz)2W(CO)4 (Cy = cyclohexyl and Pz = pyrazol-1-yl) with I2.4a Complexes 3 and 4 have never been reported previously in the literature and were characterized by spectroscopic methods. IR analysis of these complexes revealed that they both contained a carbonyl (CO) group, as evidenced by the characteristic carbonyl peaks at 1695 and 1717 cm−1 for 3 and 4, respectively. Three sets of signals corresponding to the pyrazolyl groups were observed in both the 1H and 13C NMR spectra of 3, which indicated that the two pyrazolyl rings in Received: June 16, 2014
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dx.doi.org/10.1021/om500639f | Organometallics XXXX, XXX, XXX−XXX
Organometallics
Article
Scheme 1. Reaction of Bis(3,5-dimethylpyrazol-1yl)methyllithum with W(CO)6 and I2
Figure 2. Molecular structure of 4. The thermal ellipsoids have been drawn at the 30% probability level. Selected bond distances (Å) and angles (deg): W(1)−N(1) = 2.218(3), W(1)−N(3) = 2.226(3), W(1)−C(4) = 2.317(4), W(1)−I(1) = 2.8260(6), C(4)−C(5) = 1.487(5), C(5)−O(4) = 1.217(4); N(1)−W(1)−N(3) = 86.1(1), N(2)−C(4)−N(4) = 111.9(3), C(5)−C(4)−W(1) = 122.0(2), N(2)−C(4)−W(1) = 91.8(2), C(4)−C(5)−O(4) = 123.3(3), O(4)−C(5)−O(5) = 125.2(3).
bis(pyrazol-1-yl)methide were not equivalent. It is possible that the significant level of steric repulsion in 3 may have prevented the free rotation of the pyrazolylcarbonyl moiety, which would have resulted in the two pyrazolyl rings in bis(pyrazol-1yl)methide being diastereotopic. The structures of 3 and 4 were confirmed by X-ray crystallography, and the X-ray structures of these complexes are shown in Figures 1 and 2, respectively. The X-ray data
sp3-hybridized carbon atom. This deviation suggested the existence of significant steric repulsion in these two complexes, as shown by the 1H NMR spectrum of 3. To reduce this steric repulsion, the uncoordinated pyrazolyl group sits in a position that is trans to the bis(pyrazol-1-yl)methide ligand in 3. Additionally, some electronic effects such as the directionality of the nitrogen lone pairs that, upon binding to the metal center, partially hinders the optimal overlap of orbits should also be partially responsible for the significant deviation. Possible Pathway for the Formation of 3 and 4. The reaction of W(CO)6 with bis(3,5-dimethylpyrazol-1-yl)methyllithum gave the corresponding acylmetalate, which was reacted with I2 to give the acyltungsten complex 1. Complex 2 was formed via the loss of the acyl carbonyl group in 1. The pathways responsible for the formation of 3 and 4 appeared obscure at first glance, but consideration of the experimental process in greater detail provided a much deeper understanding of the problem. For example, the yield of 3 improved significantly when a portion of 3,5-dimethylpyrazole was added at the beginning of the reaction, which suggested that a 3,5-dimethylpyrazolate anion was being formed during the course of the process. Furthermore, n-butanol appeared to promote the formation of the 3,5-dimethylpyrazolate anion, and the addition of a small quantity of n-butanol to the reaction mixture led to significant improvements in the yields of 3 and 4. Taken together with our previous finding that a 3,5dimethylpyrazolate anion was generated during the formation and subsequent reaction of a bis(3,5-dimethylpyrazol-1-yl)methyl anion,7 and the fact that lithium n-butoxide is formed by the oxidation of n-BuLi with oxygen, these results led to the construction of a plausible pathway for the formation of 3 and 4, which is depicted in Scheme 2. The nucleophilic attack of 3,5-dimethylpyrazolate or nbutoxide at the acyl carbon atom would lead to the reductive elimination of iodide from intermediate M1 and the generation of intermediate M2. The subsequent reaction of M2 with I2 would give intermediate M3.8 Intermediate M4 would be readily formed by the deprotonation of M3 at its methine carbon because of the enhanced acidity of the carbonyl αhydrogen. Intramolecular nucleophilic attack would then give complex 3 or 4.
Figure 1. Molecular structure of 3. The thermal ellipsoids have been drawn at the 30% probability level. Selected bond distances (Å) and angles (deg): W(1)−N(1) = 2.225(7), W(1)−N(4) = 2.231(7), W(1)−C(9) = 2.303(8), W(1)−I(1) = 2.8185(9), C(9)−C(15) = 1.461(12), C(15)−O(4) = 1.216(11); N(1)−W(1)−N(4) = 85.4(3), N(2)−C(9)−N(3) = 109.0(7), C(15)−C(9)−W(1) = 125.7(6), N(2)−C(9)−W(1) = 92.5(5), C(9)−C(15)−O(4) = 122.7(8), N(5)−C(15)−C(9) = 117.0(8).
revealed that both of these complexes possessed similar molecular skeletons. Complexes 3 and 4 also possessed similar structural parameters, such as analogous W−I, W−N, and W− Csp3 bond distances, as well as N−W−N bite angles, which were similar to the corresponding values reported for bis(pyrazol-1yl)methide carbonyl tungsten derivatives.4a It is noteworthy that some of the bond angles around the C(9) atom in 3 and C(4) atom in 4 (such as the C(15)−C(9)−W(1) angle of 125.7(6)° in 3 and the N(2)−C(4)−W(1) angle of 91.8(2)° in 4) deviated significantly from the tetrahedral geometry of an B
dx.doi.org/10.1021/om500639f | Organometallics XXXX, XXX, XXX−XXX
Organometallics
Article
Scheme 2. Possible Pathway for the Formation of 3 and 4
To isolate some of the proposed intermediates as direct evidence for the suggested reaction pathway, we investigated the reaction of acyl complex 1 with a series of different nucleophiles (Scheme 3). The treatment of 1 with lithium nScheme 3. Related Reaction of Acyl Complex 1 with Nucleophiles
Figure 3. Molecular structure of 5. The thermal ellipsoids have been drawn at the 30% probability level. Selected bond distances (Å) and angles (deg): W(1)−N(1) = 2.238(4), W(1)−N(4) = 2.247(4), C(15)−C(16) = 1.500(8), C(16)−O(5) = 1.200(8); N(1)−W(1)− N(4) = 80.2(1), N(2)−C(15)−N(3) = 113.0(3), W(1)−C(2)−O(2) = 172.9(4), W(1)−C(4)−O(4) = 168.1(4), N(2)−C(15)−C(16) = 123.5(7), O(5)−C(16)−O(6) = 130.4(8), C(15)−C(16)−O(5) = 125.0(8).
butoxide resulted in the formation of complex 5 (M2; Nu = nBuO). This complex was fully characterized by IR and NMR spectroscopy, and its structure was confirmed by X-ray crystallography (Figure 3). The ester-functionalized bis(3,5dimethylpyrazol-1-yl)methane acted as a chelating bidentate ligand in this complex. Although IR analysis of the reaction mixture indicated that an analogous species (M3) was being formed during the treatment of 5 with I2, it was not possible to isolate this species in sufficient purity to allow for the elucidation of its structure. Furthermore, this material readily decomposed to give ionic complex 6 during recrystallization (Figure 4). The formation of M3 is possibly because the halogenation of (N−N)W(CO)4 (N−N represents bis(pyrazol1-yl)methane) generating the seven-coordinate dihalides has been previously reported.8 However, complex 4 could be formed by the treatment of 5 with I2 followed by a base. Complex 4 was also directly obtained by the reaction of 1 with lithium n-butoxide, followed by the reaction of the resulting intermediate with I2 and a base. Pleasingly, the replacement of lithium n-butoxide with sodium 3,5-dimethylpyrazolate led to the formation of 3. These results therefore provided strong
evidence in support of the reaction pathway shown in Scheme 2 for the formation of 3 and 4. It should be pointed out that obvious decomposition was observed upon treatment of 1 with sodium 3,5-dimethylpyrazolate or lithium n-butoxide, followed by reaction with I2 and a base, which is possibly responsible for the low yields of 3 and 4 in these reactions. Synthesis and Subsequent Reaction of the Bis(3,5diisopropylpyrazol-1-yl)acyl Tungsten Derivative. The results described above inspired us to expand the scope of these reactions to other bis(pyrazol-1-yl)methanes. The treatment of bis(3,5-diisopropylpyrazol-1-yl)methane with n-BuLi led to the successful deprotonation of the methylene group.4c Similar treatment of the corresponding lithium salt with W(CO)6 followed by I2, like treatment of bis(3,5-methylpyrazol-1yl)methyllithium, gave the acyl complex 7 in relatively high yield (Scheme 4). The (pyrazol-1-yl)carbonyl and esterfunctionalized bis(pyrazol-1-yl)methide tungsten derivatives that were analogous to 3 and 4 were not obtained in this case. The exclusive formation of 7 in this case was attributed to the bulky isopropyl groups at the 3- and 5-positions of the pyrazolyl ring, which would have prevented the acyl group from C
dx.doi.org/10.1021/om500639f | Organometallics XXXX, XXX, XXX−XXX
Organometallics
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respectively, which were similar to those of 3 and 4. The 1H and 13C NMR spectra of 7 and 8 contained four sets of proton and carbon signals of the isopropyl methyl groups. The 1H and 13 C NMR spectra of 9 indicated that the two pyrazolyl rings in bis(pyrazol-1-yl)methide were diastereotopic, which resulted in all of the substituents in this complex being inequivalent. These results suggested that there was significant steric repulsion in these three complexes, which was preventing the free rotation of the substituents on the pyrazolyl rings, in a manner similar to that seen in 3 and 4. The molecular structure of 7 is shown in Figure 5. It is clear from the figure that the fundamental molecular skeleton of this
Figure 4. Molecular structure of 6. The thermal ellipsoids have been drawn at the 30% probability level. Selected bond distances (Å) and angles (deg): W(1)−I(1) = 2.8281(5), W(1)−I(2) = 2.8583(5), I(4)−I(5) = 2.8491(6), I(5)−I(6) = 2.9977(6); C(3)−W(1)−I(3) = 162.0(2), I(4)−I(5)−I(6) = 176.56(2), I(7)−I(8)−I(9) = 176.00(2).
Scheme 4. Synthesis and Related Reaction of Bis(3,5diisopropylpyrazol-1-yl)acyl Tungsten
Figure 5. Molecular structure of 7. The thermal ellipsoids have been drawn at the 30% probability level. Selected bond distances (Å) and angles (deg): W(1)−N(1) = 2.242(2), W(1)−N(4) = 2.249(2), W(1)−I(1) = 2.8563(5), W(1)−C(14) = 2.208(3), C(13)−C(14) = 1.565(4), C(14)−O(4) = 1.218(3); N(1)−W(1)−N(4) = 84.29(8), N(2)−C(13)−N(3) = 111.0(2), N(3)−C(13)−C(14) 103.4(2), W(1)−C(14)−O(4) = 139.4(2), W(1)−C(14)−C(13) = 103.4(2).
complex is similar to that of 1,4a where bis(pyrazol-1-yl)acyl acts as a tridentate κ3[N,C,N] chelating ligand. The shorter W− Cacyl (2.208(3) Å) bond distance and especially shorter C−Cacyl (1.565(4) Å) bond distance in 7, in comaprison with the corresponding values (W−C/C−C 2.231 and 1.608 Å) in 1, obviously increased the stability of 7. Complex 8 was therefore not directly formed in the reaction of bis(3,5-diisopropylpyrazol-1-yl)methyllithium with W(CO)6 and I2. Figure 6 shows the molecular structure of 8, which was found to be very similar to that of 2.9 Although the N−W−N bite angle in 8 (88.5(1)°) was larger than that found in 2 (84.9(2)°), the other structural parameters, including the W− Csp3, W−N, and W−I bond distances, were similar in both complexes. Compared with that in 7, the methine carbon in 8 deviated to a much greater extent from the tetrahedral geometry of an sp3-hybridized carbon atom, as evidenced by the smaller N(2)−C(13)−W(1) angle in 8 (92.9(2)°). This deviation was attributed to the reduction in the ring size with the loss of CO leading to an increase in steric congestion, and the aforementioned electronic effects in the structures of 3 and 4. The molecular structure of 9 is shown in Figure 7. It is clear from the figure that the fundamental framework of 9 is very similar to those in 3 and 4. For example, the functionalized bis(pyrazol-1-yl)methide acts as a tridentate monoanionic κ3[N,C,N] chelating ligand in all three of these complexes,
being attacked by nucleophiles under low concentration conditions. Furthermore, complex 7 lost its acyl group when it was heated in CH2Cl2 to yield the fused tetracyclic complex 8. The reaction of 7 with sodium pyrazolate led to the formation of an intermediate, which was subsequently reacted with I2 and a base to give complex 9. This reaction demonstrated that the steric hindrance afforded by the bulky groups on the pyrazolyl rings was not enough to completely prevent the acyl group from being attacked by nucleophiles under high-concentration conditions. Complexes 7−9 were fully characterized by IR and NMR spectroscopy, and their structures were unambiguously confirmed by X-ray crystallographic analysis. The IR spectra of 7 and 9 revealed the presence of characteristic carbonyl (CO) absorption bands at 1692 and 1711 cm−1 for 7 and 9, D
dx.doi.org/10.1021/om500639f | Organometallics XXXX, XXX, XXX−XXX
Organometallics
Article
bis(pyrazol-1-yl)methide tungsten derivatives were also prepared by the related reaction of bis(pyrazol-1-yl)acyl tungsten complexes with the corresponding nucleophiles. Although significant steric repulsion was observed in the fused fourmembered heterometallacycles, these strained rings were stable and easily obtained, presumably because of their strong W−Csp3 bond.
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EXPERIMENTAL SECTION
General Considerations. All of the solvents were dried and distilled prior to use according to standard procedures. All of the reactions were performed under an atmosphere of argon using standard Schlenk techniques. NMR spectra were recorded on a Bruker 400 spectrometer using CDCl3 as the solvent, and the chemical shifts were reported in ppm with respect to the reference (internal SiMe4 for 1 H and 13C NMR spectra). IR spectra were recorded on a Bruker Equinox 55 spectrometer as KBr pellets. Elemental analyses were carried out on an Elementar Vario EL analyzer. Bis(3,5-dimethylpyrazol-1-yl)methane and bis(3,5-diisopropylpyrazol-1-yl)methane4c were prepared according to the previously published methods. Reaction of Bis(3,5-dimethylpyrazol-1-yl)methane with nBuLi, Followed by Reaction with W(CO)6 and I2. A solution of nBuLi (1.6 M, 3.15 mL, 5 mmol) in hexane was added to a solution of bis(3,5-dimethylpyrazol-1-yl)methane (1.02 g, 5 mmol) in THF (150 mL) at −70 °C, and the resulting mixture was stirred for 1 h at the same temperature. W(CO)6 (1.76 g, 5 mmol) was then added to the reaction solution, and the resulting mixture was stirred at −70 °C for 30 min before being warmed to room temperature and stirred for 2 h. Iodine (1.27 g, 5 mmol) was added to the reaction solution, and the resulting mixture was stirred overnight. After the solvent was removed under reduced pressure, the residue was purified by column chromatography over silica with a 2/1 (v/v) mixture of CH2Cl2 and hexane as eluent to give an orange-red band containing a mixture of 2, 3, and 4. The column was then eluted with CH2Cl2 to give a yellow band. The fractions containing the yellow band were combined and concentrated to dryness to give complex 1. The mixture of 2, 3, and 4 was consecutively isolated by column chromatography over silica using a 1/3 (v/v) mixture of ethyl acetate and hexane as the eluent. Data for 1. Yield: 0.75 g (24%). 1H NMR: δ 2.50 (s, 6H), 2.80 (s, 6H) (CH3), 5.87 (s, 1H, CH), 6.12 (s, 2H, H4 of pyrazole). Data for 2. Yield: 12.5 mg (0.42%). 1H NMR: δ 2.27 (s, 6H), 2.50 (s, 6H) (CH3), 5.48 (s, 1H, CH), 5.74 (s, 2H, H4 of pyrazole). Data for 3. Yield: 56.2 mg (1.56%). 1H NMR: δ 1.87 (s, 3H), 1.94 (s, 3H), 2.38 (s, 3H), 2.52 (s, 3H), 2.57 (s, 3H), 2.61 (s, 3H) (CH3), 5.74 (s, 1H), 5.83 (s, 1H), 5.88 (s, 1H) (H4 of pyrazole). 13C NMR: δ 9.0, 11.5, 13.1, 13.3, 13.5, 14.6 (CH3), 68.0 (CH), 106.7, 107.9, 110.6 (C4 of pyrazole), 143.3, 145.0, 145.1, 151.5, 151.7, 152.3 (C3 and C5 of pyrazole), 166.8 (CO), 219.4, 222.4, 245.8 (CO). IR (cm−1): νCO 2020 (vs), 1940 (vs), 1896 (vs); νCO = 1695 (s). Anal. Found: C, 33.19; H, 2.76; N, 11.40. Calcd for C20H21IN6O4W: C, 33.36; H, 2.94; N, 11.67. Data for 4. Yield: 2.4 mg (0.07%). 1H NMR: δ 0.96 (t, J = 7.4 Hz, 3H, CH3), 1.34−1.43 (m, 2H, CH2), 1.65−1.72 (m, 2H, CH2), 2.25 (s, 6H), 2.56 (s, 6H) (CH3), 4.32 (t, J = 6.9 Hz, 2H, OCH2), 5.83 (s, 2H, H4 of pyrazole). 13C NMR: δ 10.3, 13.3 (CH3), 13.7, 19.2, 30.6, 52.9 (n-butyl carbons), 66.0 (CH), 107.6 (C4 of pyrazole), 143.6, 152.1 (C3 and C5 of pyrazole), 168.3 (CO), 219.6, 244.1 (CO). IR (cm−1): νCO 2029 (vs), 1944 (vs), 1900 (vs); νCO = 1717 (s). Anal. Found: C, 32.37; H, 3.44; N, 7.98. Calcd for C19H23IN4O5W: C, 32.69; H, 3.32; N, 8.02. Reaction of Bis(3,5-dimethylpyrazol-1-yl)methane with nBuLi in the Presence of 3,5-Dimethylpyrazole, Followed by Reaction with W(CO)6 and I2. This reaction was carried out according to the procedure described above, except 3,5-dimethylpyrazole (1 mmol) was added together with bis(3,5-dimethylpyrazol-1yl)methane (5 mmol), and a slightly larger charge of n-BuLi (1.6 M, 3.75 mL, 6 mmol) was used. After the solvent was removed under reduced pressure, the residue was purified by column chromatography over silica with a 2/1 (v/v) mixture of CH2Cl2 and hexane as eluent to
Figure 6. Molecular structure of 8. The thermal ellipsoids have been drawn at the 30% probability level. Selected bond distances (Å) and angles (deg): W(1)−N(1) = 2.226(3), W(1)−N(4) = 2.229(3), W(1)−I(1) = 2.8066(5), W(1)−C(13) = 2.279(4); N(1)−W(1)− N(4) = 88.5(1), N(2)−C(13)−N(3) = 111.8(3), N(2)−C(13)− W(1) = 92.9(2), N(3)−C(13)−W(1) = 93.1(2).
Figure 7. Molecular structure of 9. The thermal ellipsoids have been drawn at the 30% probability level. Selected bond distances (Å) and angles (deg): W(1)−N(1) = 2.227(2), W(1)−N(3) = 2.228(2), W(1)−C(4) = 2.298(2), W(1)−I(1) = 2.8103(3), C(4)−C(5) = 1.479(3), C(5)−O(4) = 1.210(2); N(1)−W(1)−N(3) = 84.20(6), N(2)−C(4)−N(4) = 111.2(2), C(5)−C(4)−W(1) = 122.8(1), N(4)−C(4)−C(5) = 118.2(2), N(4)−C(4)−W(1) = 92.0(1), C(4)−C(5)−O(4) = 123.7(2), N(5)−C(5)−C(4) = 116.6(2).
leading to the formation of a fused tetracyclic core. The noticeable difference among these complexes is the dihedral angle between the two pyrazolyl rings of the bis(pyrazol-1yl)methide moiety. The corresponding dihedral angle in 9 (75.7°) was found to be larger than those in 3 (72.2°) and 4 (70.7°). Furthermore, the W−Csp3 bond distances in 9 (2.298(2) Å), 3 (2.303(8) Å) and 4 (2.317(4) Å) were slightly longer than that in 8 (2.279(4) Å), most likely because of the influence of the carbonyl group on the methine carbon. In summary, we have investigated the reaction of bis(pyrazol1-yl)methyl anions with tungsten carbonyl, as well as the reaction of the resulting intermediates with iodine. These reactions resulted in the formation of novel (pyrazol-1yl)carbonyl and ester-functionalized bis(pyrazol-1-yl)methide carbonyl tungsten derivatives, which contained a fused fourmembered heterometallacyclic core. These functionalized E
dx.doi.org/10.1021/om500639f | Organometallics XXXX, XXX, XXX−XXX
Organometallics
Article
green crystals of complex 6. IR (cm−1): νCO 2066 (s), 2004 (vs), 1983 (vs); νCO 1578 (s). Reaction of Bis(3,5-diisopropylpyrazol-1-yl)methane with nBuLi, Followed by Reaction with W(CO)6 and I2. This reaction was carried out according to the procedure described above for the reaction of bis(3,5-dimethylpyrazol-1-yl)methane, except bis(3,5diisopropylpyrazol-1-yl)methane was used instead of bis(3,5-dimethylpyrazol-1-yl)methane. After the solvent was removed under reduced pressure, the residue was purified by column chromatography over silica with CH2Cl2 as eluent to give complex 7. Yield: 65%. 1H NMR: δ 1.28 (d, J = 6.8 Hz, 6H), 1.31 (d, J = 5.9 Hz, 6H), 1.32 (d, J = 3.6 Hz, 6H), 1.34 (d, J = 4.6 Hz, 6H) (CH3), 2.96−3.05 (m, 2H, CH), 4.15−4.25 (m, 2H, CH), 5.88 (s, 1H, CHCO), 6.16 (s, 2H, H4 of pyrazole). 13C NMR: δ 22.2, 22.3, 23.6, 24.0 (CH3), 26.7, 29.7 (CH), 79.5 (CHCO), 102.5 (C4 of pyrazole), 151.0, 167.8 (C3 and C5 of pyrazole), 221.6, 236.2 (CO). IR (cm−1): νCO 2018 (vs), 1933 (vs), 1913 (vs); νCO 1692 (s). Anal. Found: C, 37.62; H, 4.29; N, 7.63. Calcd for C23H31IN4O4W: C, 37.42; H, 4.23; N, 7.59. Heating 7 in CH2Cl2. A solution of 7 (0.15 g, 0.2 mmol) in CH2Cl2 (30 mL) was heated at reflux for 24 h. The mixture was cooled to ambient temperature, and the solvent was removed under reduced pressure to give a residue, which was purified by crystallization from a 1/1 (v/v) mixture of CH2Cl2 and hexane to give complex 8. Yield: 0.11 g (77%). 1H NMR: δ 1.27 (d, J = 6.5 Hz, 6H), 1.29 (d, J = 6.6 Hz, 6H), 1.30 (d, J = 7.1 Hz, 6H), 1.33 (d, J = 6.8 Hz, 6H) (CH3), 2.90− 3.01 (m, 2H, CH), 3.69−3.79 (m, 2H, CH), 5.54 (s, 1H, CHCO), 5.80 (s, 2H, H4 of pyrazole). 13C NMR: δ 22.2, 22.5, 23.3, 23.5 (CH3), 24.0, 26.5 (CH), 41.8 (CHW), 98.7 (C4 of pyrazole), 153.0, 163.0 (C3 and C5 of pyrazole), 220.4 (2 C), 240.1 (CO). IR (cm−1): νCO 2023 (vs), 1950 (vs), 1877 (vs). Anal. Found: C, 36.99; H, 3.95; N, 7.55. Calcd for C22H31IN4O3W: C, 37.20; H, 4.40; N, 7.89. Reaction of 7 with Sodium Pyrazolate, Followed by Reaction with I2 and Base. This reaction was carried out according to the procedure described above for the reaction of 1 with sodium 3,5-dimethylpyrazolate, except 7 and pyrazole were used instead of 1 and 3,5-dimethylpyrazole, respectively. After the solvent was removed under reduced pressure, the residue was purified by column chromatography over silica with a 6/1 (v/v) mixture of CH2Cl2 and ethyl acetate as eluent to give complex 9. Yield: 31%. 1H NMR: δ 0.56 (d, J = 5.0 Hz, 3H), 1.19 (d, J = 5.1 Hz, 3H), 1.27 (d, J = 5.2 Hz, 3H), 1.31 (d, J = 5.2 Hz, 3H), 1.32 (d, J = 5.5 Hz, 3H), 1.34 (d, J = 5.6 Hz, 3H), 1.41 (d, J = 5.2 Hz, 3H), 1.51 (d, J = 4.9 Hz, 3H) (CH3), 2.54− 2.64 (m, 1H), 2.94−3.04 (m, 1H), 3.71−3.83 (m, 1H), 3.90−4.00 (m, 1H) (CH), 5.90 (s, 1H), 5.98 (s, 1H) (H4 of 3,5-diisopropylpyrazole), 6.38−6.39 (m, 1H, H4 of pyrazole), 7.44 (s, 1H), 8.33 (d, J = 2.0 Hz, 1H) (H3 and H5 of pyrazole). 13C NMR: δ 22.0, 22.7, 22.8, 23.2, 23.3, 23.6, 24.0, 24.5, 24.6, 26.1, 26.5, 26.6 (isopropyl carbons), 56.6 (CHW), 99.9, 100.4 (C4 of 3,5-diisopropylpyrazole), 109.2 (C4 of pyrazole), 129.9, 143.5 (C3 and C5 of pyrazole), 154.9, 156.9, 162.5, 163.4 (C3 and C5 of 3,5-diisopropylpyrazole), 165.9 (CO), 218.6, 221.7, 246.7 (CO). IR (cm−1): νCO 2023 (vs), 1937 (vs), 1898 (vs); νCO 1711 (s). Anal. Found: C, 38.42; H, 3.65; N, 10.17. Calcd for C26H33IN6O4W: C, 38.82; H, 4.14; N, 10.45. X-ray Structure Determinations of 3−9. Crystals of 3−9 suitable for X-ray analysis were grown by the diffusion of hexane into CH2Cl2 solutions of complexes 3−9 at −18 °C. Crystals of 3 contained half of a disordered CH2Cl2 molecule. Satisfactory results were obtained when the occupancy factor was refined to 0.25. The nbutoxycarbonyl group in 5 was also disordered, and an occupancy factor of 0.5 was required to afford satisfactory results. All of the intensity data were collected on a Rigaku Saturn CCD diffractometer using graphite-monochromated Mo Kα radiation (λ = 0.71073 Å). Semiempirical absorption corrections were applied using the CrystalClear program.10 The structures were solved by direct methods and difference Fourier maps using the SHELXS feature of the SHELXTL package and refined with SHELXL11 by full-matrix least squares on F2. All of the non-hydrogen atoms were refined anisotropically. A summary of the fundamental crystal data for these complexes is given in Tables 1 and 2.
give only complex 3 (yield 6%). The column was then eluted with CH2Cl2 to give complex 1 (yield 30%). Reaction of Bis(3,5-dimethylpyrazol-1-yl)methane with nBuLi in the Presence of n-Butanol, Followed by Reaction with W(CO)6 and I2. This reaction was carried out according to the procedure described above for the reaction in the presence of 3,5dimethylpyrazole, except n-butanol (1 mmol) was used instead of 3,5dimethylpyrazole (1 mmol). After the solvent was removed under reduced pressure, the residue was purified by column chromatography over silica with a 2/1 (v/v) mixture of CH2Cl2 and hexane as eluent to give a mixture of 3 and 4. The column was then eluted with CH2Cl2 to give complex 1 (yield 26%). The mixture of 3 and 4 was isolated by column chromatography over silica with a 3/1 (v/v) mixture of ethyl acetate and hexane as eluent to afford 3 (yield 8%) and 4 (yield 3%). Reaction of 1 with Sodium 3,5-Dimethylpyrazolate, Followed by Reaction with I2 and Base. NaH (24 mg, 1 mmol) was added to a solution of 3,5-dimethylpyrazole (96 mg, 1 mmol) in THF (10 mL) at room temperature, and the resulting solution was stirred for 1 h. The reaction mixture was then transferred via a syringe to a solution of 1 (0.63 g, 1 mmol) in THF (10 mL), and the resulting mixture was stirred continuously for 1 h. Iodine (0.25 g, 1 mmol) was added to the reaction solution, and the resulting mixture was stirred overnight. NaH (24 mg, 1 mmol) was again added to the reaction solution, and the resulting mixture was stirred for 5 h. After the solvent was removed under reduced pressure, the residue was purified by column chromatography over silica with a 2/1 (v/v) mixture of CH2Cl2 and hexane as eluent to give complex 3. Yield: 43 mg (6%). Reaction of 1 with Lithium n-Butoxide, Followed by Reaction with I2 and Base. This reaction was carried out according to the procedure described above for the reaction with sodium 3,5dimethylpyrazolate, except n-butanol (1 mmol) and n-BuLi (1 mmol) were used instead of 3,5-dimethylpyrazole (1 mmol) and NaH (1 mmol), respectively. After the solvent was removed under reduced pressure, the residue was purified by column chromatography over silica with a 2/1 (v/v) mixture of CH2Cl2 and hexane as eluent to give complex 4 (yield 7%). Reaction of 1 with Lithium n-Butoxide. A solution of n-BuLi (1.6 M, 0.63 mL, 1 mmol) in hexane was added to a solution of nbutanol (91 μL, 1 mmol) in THF (10 mL) at room temperature, and the resulting mixture was stirred for 1 h at ambient temperature. The reaction mixture was transferred via a syringe to a solution of 1 (0.63 g, 1 mmol) in THF (10 mL), and the resulting mixture was stirred continuously for 1 h. The solvent was removed under reduced pressure, and the residue was purified by column chromatography over silica with a 2/1 (v/v) mixture of CH2Cl2 and hexane as eluent to give complex 5. Yield: 0.18 g (30%). 1H NMR: δ 0.89 (t, J = 7.3 Hz, 3H, CH3), 1.21−1.33 (m, 2H, CH2), 1.55−1.62 (m, 2H, CH2), 2.42 (s, 6H), 2.55 (s, 6H) (CH3), 4.31 (t, J = 6.5 Hz, 2H, OCH2), 6.10 (s, 2H, H4 of pyrazole), 6.45 (s, 1H, CH). 13C NMR: δ 11.7, 17.1 (CH3), 13.6, 18.9, 30.1, 68.3 (n-butyl carbons), 66.0 (CH), 108.3 (C4 of pyrazole), 142.2, 155.9 (C3 and C5 of pyrazole), 163.1 (CO), 202.4, 203.1, 211.3 (2 C) (CO). IR (cm−1): νCO 2002 (vs), 1869 (vs), 1846 (vs), 1817 (vs); νCO 1759 (s). Anal. Found: C, 40.31; H, 3.94; N, 9.21. Calcd for C20H24N4O6W: C, 40.02; H, 4.03; N, 9.33. Reaction of 5 with I2 and Base. A solution of I2 (0.13 g, 0.5 mmol) in THF (10 mL) was added to a stirred solution of 5 (0.30 g, 0.5 mmol) in THF (10 mL) at room temperature, and the resulting mixture was stirred for 2 h at ambient temperature. NaH (12 mg, 0.5 mmol) was added to the reaction solution, and the resulting mixture was stirred continuously for 5 h. The solvent was removed under reduced pressure, and the residue was purified by column chromatography over silica with a 3/2 (v/v) mixture of CH2Cl2 and hexane as eluent to give complex 4. Yield: 52 mg (15%). In a separate experiment, the reaction mixture was stirred continuously for 2 h following the addition of the iodine solution, and the solvent was then removed under reduced pressure to give a residue. A portion of the residue was monitored by IR spectroscopy, which showed three carbonyl peaks at 2101 (s), 2077 (s), and 2008 (vs) cm−1. The remainder of the residue was recrystallized from a 1/1 (v/v) mixture of CH2Cl2 and hexane to yield a trace amount of yellowF
dx.doi.org/10.1021/om500639f | Organometallics XXXX, XXX, XXX−XXX
Organometallics
Article
Table 1. Crystallographic Data for 3−7 formula fw cryst size, mm cryst syst space group a, Å b, Å c, Å β, deg V, Å3 Z T (K) calcd density, Mg/m−3 F(000) μ, mm−1 no. of rflns collcd/unique (Rint) no. of rflns obsd with I ≥ 2σ(I) no. of params R, Rw (I ≥ 2σ(I)) R, Rw (all data) goodness of fit on F2 largest diff peak and hole, e Å−3
3·0.5CH2Cl2
4
5
6·2CH2Cl2
7·CH2Cl2
C20.5H22ClIN6O4W 762.64 0.20 × 0.18 × 0.12 monoclinic P21/n 11.919(2) 19.424(4) 12.313(3) 98.38(3) 2820.4(10) 4 293(2) 1.796 1452 5.319 28098/6616 (0.0860) 4688 350 0.0605, 0.1630 0.0848, 0.1799 1.009 1.953, −1.200
C19H23IN4O5W 698.16 0.26 × 0.22 × 0.20 orthorhombic Pna21 15.526(5) 8.489(3) 17.653(6) 90 2326.7(14) 4 113(2) 1.993 1328 6.327 31754/6618 (0.0501) 5530 277 0.0224, 0.0380 0.0268, 0.0388 0.820 1.834, −1.355
C20H24N4O6W 600.28 0.24 × 0.20 × 0.18 tetragonal I41/a 30.621(4) 30.621(4) 9.4304(9) 90 8842.3(17) 16 113(2) 1.804 4704 5.269 30584/5228 (0.0741) 4648 325 0.0334, 0.0725 0.0417, 0.0857 1.107 1.263, −1.690
C42H55Cl4I9N12O10W 2355.73 0.18 × 0.12 × 0.10 orthorhombic P212121 13.7502(19) 21.771(3) 22.894(3) 90 6853.4(16) 4 113(2) 2.283 4360 5.951 71264/16315 (0.0440) 15408 733 0.0304, 0.0525 0.0331, 0.0533 1.001 0.933, −0.819
C24H33Cl2IN4O4W 823.19 0.20 × 0.18 × 0.12 monoclinic C2/c 34.019(11) 9.296(3) 20.062(6) 108.758(5) 6008(3) 8 113(2) 1.820 3184 5.086 37296/7135 (0.0531) 6491 333 0.0334, 0.0740 0.0377, 0.0759 1.065 1.898, −1.586
Table 2. Crystallographic Data for 8 and 9 8 formula fw cryst size, mm cryst syst space group a, Å b, Å c, Å α, deg β, deg γ, deg V, Å3 Z T (K) calcd density, Mg/m−3 F(000) μ, mm−1 no. of rflns collcd/unique (Rint) no. of rflns obsd with I ≥ 2σ(I) no. of params R, Rw (I ≥ 2σ(I)) R, Rw (all data) goodness of fit on F2 largest diff peak and hole, e Å−3
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C26H33IN6O4W 804.33 0.22 × 0.20 × 0.20 monoclinic P21/n 9.9980(10) 15.6800(15) 19.460(2) 90 102.242(4) 90 1371.6(18) 4 113(2) 1.792 1560 4.950 58186/14494 (0.0390) 13085
288 0.0311, 0.0781 0.0320, 0.0788 1.053 1.288, −2.716
351 0.0325, 0.0568 0.0380, 0.0588 1.085 1.459, −1.851
AUTHOR INFORMATION
Corresponding Author
9
C22H31IN4O3W 710.26 0.20 × 0.18 × 0.12 triclinic P1̅ 9.9540(17) 10.209(2) 14.519(3) 72.300(14) 70.935(16) 71.540(13) 1289.2(4) 2 113(2) 1.830 684 5.706 11853/6073 (0.0429) 5844
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*L.-F.T.: e-mail,
[email protected]; fax, 86-22-23502458. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS This work is supported by the National Natural Science Foundation of China (No. 21372124). The authors also thank the reviewers for their valuable suggestions.
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REFERENCES
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ASSOCIATED CONTENT
S Supporting Information *
CIF files giving crystallographic data for 3−9. This material is available free of charge via the Internet at http://pubs.acs.org. G
dx.doi.org/10.1021/om500639f | Organometallics XXXX, XXX, XXX−XXX
Organometallics
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dx.doi.org/10.1021/om500639f | Organometallics XXXX, XXX, XXX−XXX
