Article Cite This: Organometallics XXXX, XXX, XXX−XXX
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Molybdenum-Mediated Vinylidene Rearrangement of Internal Acylalkynes and Sulfonylalkynes Takuya Kuwabara, Kousuke Sakajiri, Yousuke Oyama, Shintaro Kodama, and Youichi Ishii* Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 Japan
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S Supporting Information *
ABSTRACT: Vinylidene rearrangement of internal acylalkynes and sulfonylalkynes at a d6 molybdenum center is presented. Treatment of [(η7-C7H7)MoBr(dppe)] with various acylalkynes R−CC−COR′ in the presence of NaBArF4 afforded the corresponding vinylidene complexes [(η7-C7H7)Mo[CCR(COR′)](dppe)][BArF4], which exist as mixtures of two rotamers, with respect to the MoCα bond at room temperature, as evidenced by NMR studies. This provides the first example of vinylidene rearrangement of internal alkynes at a Mo center. X-ray diffraction studies revealed that the vinylidene ligand :C CR(COR′) coordinates almost perpendicularly toward the C7H7 plane. A 13C-labeling experiment unveiled selective migration of the acyl group, which is in agreement with a nucleophilic 1,2-migration mechanism. When sulfonylakynes R−CC−SO2R′ were used as substrates, three types of productsη2-alkyne, vinylidene, and unexpected η2-phosphonioalkyne complexeshave been isolated, depending on the R group. The η2-phosphonioalkyne complex is considered to be generated through nucleophilic substitution of the sulfonyl group by a phosphine.
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INTRODUCTION Vinylidene rearrangement at a transition-metal center has been utilized in catalytic as well as stoichiometric synthesis of various types of organic molecules.1 Although such transformation of terminal alkynes and heteroatom-substituted internal alkynes (R−CC−E or E−CC−E, where E = SiR′3,2 GeR′3,3 SnR′3,4 SR′,5 SeR′,6 Br,7 and I;8 see Chart 1A) have been well-established, the corresponding reaction using carbon-disubstituted internal alkynes is considered to be an unusual process, because activation of C−C bonds is more difficult than that of C−H and C−E bonds. Thus, vinylidene rearrangement of carbon-disubstituted internal alkynes had been limited to a very few examples with acylalkynes until 2008.9 We have shown that general carbon-disubstituted internal alkynes can be transformed to vinylidene ligands in Group 8 metal complexes (FeII, RuII, OsII; see Chart 1B).10 Recently, this rearrangement using a ruthenium complex has been applied for catalytic synthesis of indole and naphthalene derivatives.11 These results prompted us to investigate whether this type of rearrangement can be promoted with transition metals other than those of Group 8. In fact, recent studies have successfully expanded the reaction site for such transformation to Group 9 metal (IrIII) complexes.9e,12 These experimental facts suggest that half-sandwich-type d6 transition-metal complexes can induce the vinylidene rearrangement of internal alkynes, and we have now turned our research interest focused © XXXX American Chemical Society
Chart 1. Examples of Vinylidene Rearrangement and This Work
on zerovalent Group 6 metal complexes to confirm this hypothesis. Although vinylidene rearrangement of terminal alkynes at a Group 6 metal center have been wellinvestigated,13,14 to the best of our knowledge, that of internal Received: January 15, 2019
A
DOI: 10.1021/acs.organomet.9b00019 Organometallics XXXX, XXX, XXX−XXX
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Organometallics
internal alkynes were examined as substrates, as summarized in Table 1.19 Note that this reaction tolerates various types of
alkynes has never been achieved. Here, we report vinylidene rearrangement of internal acylalkynes at a Mo0 center to afford the corresponding vinylidene complexes, while sulfonylalkynes provide three types of complexes: η2-alkyne-, vinylidene-, and unexpected η2-phosphonioalkyne complexes. Mechanisms for the formation of these complexes are also discussed.
Table 1. Scope of the Vinylidene Rearrangement of Internal Acylalkynes and A/B Ratios Determined by NMR Spectroscopy
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RESULTS AND DISCUSSION We have investigated the reactivity of [(η7-C7H7)MoBr(dppe)] 115 and various internal alkynes in the presence of NaBArF4, where ArF = 3,5-bis(trifluoromethyl)phenyl and dppe = 1,2-bis(diphenylphosphino)ethane, but unlike in reactions with [CpRuCl(dppe)] (Cp = η5-C5H5), diaryl and dialkyl alkynes failed to give tractable products. In contrast, ketoalkynes were successfully transformed to vinylidene complexes (Scheme 1). When complex 1 was allowed to
2a 2b 2c 2d 2e 2f 2g 2h
Scheme 1. Reaction of 1 and Ph−CC−COPh in the Presence of NaBArF4
a
R
R′
yield (%)
ratio of A:B
Ph Ph p-Ansa cyclo-C3H5 Ph Ph p-Ansa 1-Naph
Ph p-Tol Ph Ph Me H H Ph
45 49 33 37 35 23 32 41
1.4:1 1.6:1 1.5:1 7:1 1:1.5 1:2.5 1:2.3 1:11
Ans = C6H4OMe.
substituents, including aryl, alkyl, formyl, and 1-naphthyl to give vinylidene complexes 2b−2h in moderate isolated yields, demonstrating the versatility of this reaction as a preparative method of molybdenum ketovinylidene complexes. All the complexes thus obtained exist as equilibrium mixtures of rotamers, as evidenced by their 1H, 31P{1H}, and 13C{1H} NMR spectra. Moreover, by taking account of the shielding effects caused by the dppe Ph groups, dominant rotamers were successfully determined: one of the vinylidene substituents that resides between the two Ph groups of the dppe ligand is strongly shielded. For instance, the Me protons of 2e resonated at δ 1.66 and 1.02 ppm in the integration ratio of 1:1.5, and the upfield signal is assignable to rotamer B. According to this analysis, rotamer A is dominant in 2a−2d, while rotamer B is the major isomer for 2e−2h, as summarized in Table 1. Our results are very consistent with the Whiteley report,13 demonstrating that the major rotamers have smaller substituents on the same side with the bulky dppe ligand to minimize steric congestion. Molecular structures of 2d and 2e have been determined by X-ray diffraction (XRD) analysis, the former of which is shown in Figure 1, while the latter is shown in Figure S1 in the Supporting Information. Because both complexes exist as a
NaBArF4
react with Ph−CC−COPh in the presence of in toluene at 70 °C, the color of the solution changed from green to dark purple and then to dark brown. The 31P{1H} NMR spectrum of the dark purple solution displays a singlet at δ 59.3, but this intermediate species was too unstable to be isolated. We consider that the initial step is the formation of a complex in which the O atom of the acyl group coordinates to the Mo atom,16 because similar treatment of 1 with acetone in toluene in the presence of NaBArF4 gave rise to the formation of a dark brown solution showing a 31P{1H} NMR signal at δ 61.9, where [(η7-C7H7)Mo(dppe)(acetone)]+ is expected to be formed.17 After purification of the reaction mixture by column chromatography followed by recrystallization from Et2O/hexane, the desired vinylidene complex [(η7-C7H7)Mo[CCPh(COPh)](dppe)][BArF4] 2a was isolated as orange crystals in 45% yield. In 31P{1H} NMR of 2a, two singlets were observed at δ 56.8 and 55.9 ppm, implying that there exist two distinct chemical species that can be discriminated by NMR and possess apparent Cs symmetry. Thus, the vinylidene substituents are oriented orthogonally, with respect to the C7H7 plane, as was found in related Mo-vinylidene complexes.13a Moreover, two characteristic 13C{1H} NMR triplet signals originated from the vinylidene Cα were observed at δ 371.1 and 367.7 ppm. These NMR data suggest that 2a exists in solution as a mixture of two rotamers, with respect to the MoCα bond, whose rotation is slow at room temperature. In relation to this observation, Whiteley reported that detailed NMR studies of [(η7C7H7)Mo[CCMe(nBu)](dppe)]+ also indicated the presence of two rotamers over the temperature range of −40 °C to 75 °C.13a,18 The ratio of rotamers A and B was determined to be 1.4:1 on the basis of the 31P{1H} NMR data, as well as the 1H NMR signals of the dppe methylene protons. To gain deeper insight into the relationship between vinylidene substituents and rotamer A/B ratio, as well as to broaden the substrate scope of this rearrangement, various
Figure 1. Molecular structures of the cationic part of 2d from two different angles with thermal ellipsoid plot at 50% probability. The phenyl group of the acyl substituent for the right figure and all H atoms are omitted for clarity. Selected bond lengths (Å): Mo−C(1), 1.959(3); C(1)−C(2), 1.322(4). B
DOI: 10.1021/acs.organomet.9b00019 Organometallics XXXX, XXX, XXX−XXX
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Organometallics rotamer A and exhibit very similar structural features,20 only details for 2d are discussed here. Complex 2d has a typical piano stool structure with the C7H7, the two P atoms of the dppe, and the vinylidene α-C atom. Structural characteristics of 2d are similar to those of related molybdenum complexes bearing a monosubstituted vinylidene (:CC(H)R) ligand.13b The Mo−Cα and Cα−Cβ bond lengths are 1.959(3) and 1.322(4) Å, respectively, which are in normal ranges of the corresponding double bond lengths.13 The vinylidene substituents are almost orthogonally oriented to the C7H7 ring plane; the angle made by the C7H7 and C1−C2−C3−C4 planes is 85.6°, while the C*−Mo−C1 and C1−C2−C3−C4 planes form a dihedral angle of only 18.4°, where C* is the center of the C7H7 ring. Moreover, single-point calculations based on the structure by the XRD analysis of 2d (Figure 2)21 revealed that the HOMO
Scheme 2. Mechanistic Study Using a 13C-Enriched Substratea
a
The asterisks on the carbon atoms indicate 13C-enrichment.
For further development of Mo-mediated vinylidene rearrangement of internal alkynes, reactions using sulfonylalkynes were investigated (Scheme 3). In the reaction using Ph− Scheme 3. Reactions of 1 with Sulfonylalkynes Figure 2. HOMO (left) and HOMO−1 (right) of 2d with iso values of 0.04 au (Mo, blue green; P, orange; O, red; and C, gray).
contributes to the CαCβ π-bond, while the HOMO−1 (and also the HOMO−2; see Figure S4 in the SI) to the Mo Cα π-bond. As seen in Figure 2, the MoCα π-bonding orbital (i.e., π back-donation from the filled metal d orbital to the π* of the vinylidene) distributes along the plane orthogonal to the C7H7, which is in agreement with the orthogonal conformation of the vinylidene moiety. The main features of the MOs are similar to those of [(η7-C7H7)Mo(CCH2)(dppe)]+, which were examined in detail through a fragment analysis of vinylidene (:CCH2) and [(η7-C7H7)Mo(dppe)]+ and compared with those of [(η5-Cp)Ru(CCH2)(dppe)]+.13b To better understand the mechanism for the rearrangement, experiments using a 13C-enriched alkyne (25% enriched Ph− C13C−COPh) were performed (Scheme 2). When the benzoyl group undergoes 1,2-migration, complex 2a-13Cα is generated via TS-A, while complex 2a-13Cβ is formed by migration of the Ph group. After purification by the same method as that for 2a, orange crystals were obtained in 28% yield. In the 13C{1H} NMR spectrum of this sample, only the signals attributable to the Cα were enhanced (see Figure S3 in the SI). A detailed analysis of the spectrum disclosed that the migration ratio of the benzoyl group is essentially 100%.19 This trend is in good agreement with both the experimental and theoretical results that the more electron-withdrawing substituent on the alkyne has a tendency to migrate in vinylidene rearrangement at Group 810b,e,22 and Group 912b metal centers. The origin of this selectivity can be explained by structure of the transition state (TS) in this reaction: the vinylidene rearrangement is a nucleophilic migration of the αsubstituent toward the positively charged β-carbon and is expected to be facilitated by an electron-donating group at the β-carbon. Therefore, TS-A with a β-Ph group is more favorable than TS-B with a β-benzoyl, leading to selective migration of the benzoyl group.
CC−SO2(p-Tol) at room temperature, an unexpected η2phosphonioalkyne complex [(η 7 -C 7 H 7 )MoBr(η 1 :η 2 PPh2C2H4PPh2CCPh)][BArF4] 3 was isolated as reddishbrown crystals in 13% yield.23 The 31P{1H} NMR spectrum of 3 displays two doublet signals at δ 14.7 and 4.9 ppm with 3JP−P coupling of 12.8 Hz, which is in accordance with the structure having two chemically inequivalent P atoms. Notably, with the progress of the reaction, precipitation of white powder was observed, which was characterized to be (p-Tol)SO2Na, on the basis of the 1H NMR and IR spectra. Thus, this reaction is a formal nucleophilic substitution of (p-Tol)SO2 group with a phosphine at an sp-hybridized carbon. Presumably it involves either a direct addition−elimination process in an η2-alkyne complex concomitant with recoordination of a Br− anion (Path A in Scheme 4) or nucleophilic attack on the α-carbon of a vinylidene ligand derived from the alkyne, followed by the elimination of a (p-Tol)SO2− anion (Path B in Scheme 4).24 C
DOI: 10.1021/acs.organomet.9b00019 Organometallics XXXX, XXX, XXX−XXX
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Organometallics Scheme 4. Plausible Mechanisms for the Formation of 3
Figure 3. Molecular structures of the cationic parts of 3 (left) and 4 (right) with thermal ellipsoid plot at 50% probability. A CH2Cl2 molecule in 4 and all H atoms are omitted for clarity. Selected bond lengths (Å) and angle (deg) for 3: Mo−C(1), 2.193(3); Mo−C(2), 2.185(3); C(1)−C(2), 1.265(4); P(1)−C(2)−C(1), 140.5(3). Selected bond lengths (Å) and angle (deg) for 4: Mo−C(1), 2.177(3); Mo−C(2), 2.254(3); C(1)−C(2), 1.258(5); S−C(1)− C(2), 137.5(3).
Nucleophilic substitutions of sulfonylalkynes have recently been reported to occur at sp carbon centers, which is in accordance with the former mechanism.25 By contrast, when Me−CC−SO2Ph was used as a substrate, orange crystals of η2-alkyne complex [(η7-C7H7)Mo(η2-MeCCSO2Ph)(dppe)][BArF4] 4 were obtained in 42% yield. As protons of the Me group resonate at δ 0.08 ppm, the Me group resides in a pocket of the dppe ligand and is highly shielded by two Ph groups of the dppe ligand, as in the case of complexes 2. In addition, only one singlet signal was found at δ 50.2 ppm in the 31P{1H} NMR spectrum. These NMR observations led to the conclusion that the η2-alkyne ligand coordinates orthogonally to the C7H7 plane, and only one of two rotamers was selectively generated to avoid steric congestion between the SO2Ph and dppe Ph groups. This is in sharp contrast to the case of [(η5-C5H5)Mo(CO)(NO)(η2HCCPh)] that exists as a mixture of two rotamers.26 Unfortunately, our attempts to transform complex 4 to a vinylidene or phosphonioalkyne complex by heating its solution resulted in the formation of a complex mixture. To our delight, changing a substrate and reaction conditions to p-Ans−CC−SO2Ph and heating at 100 °C for 5 min, respectively, provided desired vinylidene complex [(η7-C7H7)Mo[CC(p-Ans)(SO2Ph)](dppe)][BArF4] 5 in 18% yield.27 Although XRD analysis of 5 has not been available, characteristic 13C{1H} NMR signal observed at δ 356.2 ppm unambiguously supports the formation of the vinylidene complex 5. According to the 1H, 31P{1H}, and 13C{1H} NMR spectra, complex 5 also exist as a single rotamer in which the less bulky p-Ans group is situated in the same side with the dppe ligand. Solid-state structures of 3 and 4 are shown in Figure 3. It is interesting to note that phosphonioalkyne complexes have rarely been described in the literature,24b,28 and to the best of our knowledge, complex 3 provides the first structurally characterized molybdenum−phosphonioalkyne complex. Both complexes 3 and 4 have typical piano stool structures with the C7H7, phosphine, Br, and phosphonioalkyne ligands, and the C7H7, dppe, and sulfonylalkyne ligands, respectively. The bend back angles of the η2-alkyne ligand in each complex are ca. 30°−40°, reflecting a considerable back-bonding from the electron-rich Mo center. The distances between the Mo and the alkynyl C atoms are 2.185(3)−2.254(3) Å, which are longer than those in reported Mo0 complexes incorporated with η2-alkyne and dppe ligands (2.044(13)−2.081(13) Å).29
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CONCLUSION We have demonstrated, for the first time, that a formal d6 Mo center in [(η7-C7H7)Mo(dppe)]+ can induce vinylidene rearrangement of internal alkynes. Each of the vinylidene complexes obtained from acylalkynes exists as a mixture of two rotamers, and their ratios are dependent on the substituents of the vinylidene ligands. Rotamers having the smaller substituent on the same side with the dppe ligand exist predominantly in solution, because of the steric repulsion between the dppe Ph groups and the substituent. XRD analysis of complexes 2d and 2e revealed nearly orthogonal orientation of the vinylidene ligand toward the C7H7 plane. 13C-labeling experiments clarified that the acyl group undergoes 1,2-migration selectively, which is in accord with a nucleophilic migration mechanism. When internal sulfonylalkynes were used as substrates, three types of complexes, η2-phosphonioalkyne complex 3, η2-alkyne complex 4 and vinylidene complex 5 were isolated, depending on the substituents and reaction conditions. Although it has been considered that the vinylidene rearrangement of internal alkynes is an unusual process, because of the inertness of C−C bonds, present work successfully expanded reaction sites for this transformation to a Group 6 metal.
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EXPERIMENTAL SECTION
Synthesis of [(η7-C7H7)Mo[CCPh(COPh)](dppe)][BArF4] (2a) (Typical Procedure for the Synthesis of Complex 2). A mixture of [(η7-C7H7)MoBr(dppe)] (1) (40.5 mg, 0.061 mmol), PhCCCOPh (15.7 mg, 0.076 mmol) and NaBArF4·2H2O (60.8 mg, 0.066 mmol) in toluene (3 mL) was stirred at room temperature for 5 min. The resulting purple suspension was filtered through a short pad of Celite, and the pad was rinsed with toluene (ca. 1 mL). The combined filtrate was heated at 70 °C for 24 h. The resulting orange suspension was dried in vacuo, and the residue was purified by column chromatography on silica gel (eluent: CH2Cl2). The eluate was dried up in vacuo and recrystallized from diethyl ether/hexane to afford [(η7-C7H7)Mo[CCPh(COPh)](dppe)][BAr F4] (2a) (45.8 mg, 0.028 mmol, 45% yield) as orange crystals. For Rotamer A: Selected 1H NMR (CDCl3): δ 6.82 (t, 3JHH = 7.0 Hz, 1H, p-H of CCPh), 6.59 (t, 3JHH = 7.0 Hz, 2H, m-H of CCPh), 5.25 (d, 3JHH = 7.0 Hz, 2H, o-H of CCPh), 4.99 (C7H7, overlapping with C7H7 signal of rotamer B), 2.67 (br, 2H, dppe), 2.03 (br, 2H, dppe). 31 1 P{ H} NMR (CDCl3): δ 56.8 (s, dppe). Selected 13C{1H} NMR (CDCl3): δ 367.7 (t, 2JCP = 29 Hz, MoCC), 192.9 (t, 4JCP = 7 Hz, CO). For Rotamer B: Selected 1H NMR (CDCl3): δ 6.90 (t, 3 JHH = 7.0 Hz, 2H, m-H of C(O)Ph), 6.69 (d, 3JHH = 7.0 Hz, 2H, oH of CCPh), 6.42 (d, 3JHH = 7.0 Hz, 2H, o-H of C(O)Ph), 4.99 D
DOI: 10.1021/acs.organomet.9b00019 Organometallics XXXX, XXX, XXX−XXX
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Organometallics (C7H7, overlapping with C7H7 signal of rotamer A), 3.47 (br, 2H, dppe), 2.85 (br, 2H, dppe). 31P{1H} NMR (CDCl3): δ 55.9 (s, dppe). Selected 13C{1H} NMR (CDCl3): δ 371.1 (t, 2JCP = 29 Hz, MoC C), 191.0 (t, 4JCP = 6 Hz, CO). IR (KBr, cm−1): 1647 (νCO). Anal. Calcd for C80H53BF24MoOP2 (2a): C, 58.06; H, 3.23. Found: C, 57.66; H, 3.03. Synthesis of [(η7-C7H7)Mo(η1:η2-PPh2C2H4PPh2CCPh)][BArF4] 3. A mixture of [(η7-C7H7)MoBr(dppe)] (1) (80.2 mg, 0.121 mmol), PhCCSO2(p-Tol) (62.2 mg, 0.243 mmol) and NaBArF4·2H2O (122 mg, 0.132 mmol) in toluene (6 mL) was stirred at room temperature for 2 h. The resulting red-brown suspension was dried in vacuo, and the residue was purified by column chromatography on silica gel (eluent: AcOEt) under an argon atmosphere. The eluate was dried up in vacuo and recrystallized from diethyl ether/hexane to afford [(η7-C7H7)Mo(η1:η2-PPh2C2H4PPh2CCPh)][BArF4] (3) (25.1 mg, 0.015 mmol, 13% yield) as red-brown crystals. 1H NMR (CDCl3): δ 7.80−7.65 (m, 14H, PPh2 + BArF4), 7.59−7.47 (m, 11H, PPh2 + BArF4), 7.41−7.31 (m, 9H, m- and p-H of CCPh + PPh2), 7.04 (d + br, 3JHH = 7.0 Hz, 3H, o-H of CCPh + PPh2), 4.83 (dd, 3 JPH = 4.5 Hz, 4JPH = 2.0 Hz, 7H, C7H7), 4.14 (br, 1H, dppe), 3.18 (br, 1H, dppe), 2.68 (br, 1H, dppe), 2.43 (br, 1H, dppe). 31P{1H} NMR (CDCl3): δ 14.7 (d, 3JPP = 13 Hz, dppe), 4.89 (d, 3JPP = 13 Hz, dppe). Selected 13C{1H} NMR (CDCl3): δ 95.5 (s, C7H7). Anal. Calcd for C73H48BBrF24MoP2 (3): C, 53.80; H, 2.97. Found: C, 54.14; H, 2.95. A similar reaction with PhCCSO2Ph was also confirmed by 31P{1H} NMR to give complex 3 as the major product. Synthesis of [(η7-C7H7)Mo(η2-MeCCSO2Ph)(dppe)][BArF4] 4. A mixture of [(η7-C7H7)MoBr(dppe)] (1) (39.9 mg, 0.060 mmol), MeCCSO2Ph (11.3 mg, 0.063 mmol) and NaBArF4·2H2O (61.6 mg, 0.067 mmol) in toluene (3 mL) was stirred at room temperature for 2 h. The orange powder deposited was collected by filtration and washed with toluene (ca. 1.0 mL). The eluate was dried up in vacuo and recrystallized from CH2Cl2/hexane to afford [(η7-C7H7)Mo(η2MeCCSO2Ph)(dppe)][BArF4] (4) (41.9 mg, 0.026 mmol, 43% yield) as orange crystals. 1H NMR (CD2Cl2): δ 7.73 (s, 8H, BArF4), 7.61 (d, 3JHH = 7.5 Hz, 2H, o-H of SO2Ph), 7.58−7.46 (m, 17H, Ar), 7.44−7.31 (m, 6H, Ar), 7.25−7.15 (m, 4H, Ar), 5.20 (t, 3JHP = 3.4 Hz, 7H, C7H7), 3.18−2.93 (m, 4H, dppe), 0.08 (s, 3H, Me). 31P{1H} NMR (CD2Cl2): 50.2 (s, dppe). Selected 13C{1H} NMR (CD2Cl2): δ 138.3 (t, 2JCP = 21 Hz, CC), 119.8 (t, 2JCP = 4 Hz, CC), 92.7 (s, C7H7), 14.9 (s, CH3). IR (KBr, cm−1): 1814 (νCC). Anal. Calcd for C74H51BF24MoO2P2S (4): C, 54.56; H, 3.16. Found: C, 54.49; H, 2.96. Synthesis of [(η7-C7H7)Mo[CC(p-Ans)(SO2Ph)](dppe)][BArF4] 5. A mixture of [(η7-C7H7)MoBr(dppe)] (1) (120 mg, 0.180 mmol) and (p-Ans)CCSO2Ph (59.4 mg, 0.218 mmol) in toluene (9 mL) was heated at 100 °C. NaBArF4·2H2O (182 mg, 0.197 mmol) was added, and the mixture was stirred for 5 min at this temperature. The resulting brown suspension was dried in vacuo, and the residue was purified by column chromatography on silica gel (eluent: CH2Cl2). The eluate was dried up in vacuo and recrystallized from CH2Cl2/ hexane to afford [(η7-C7H7)Mo[CC(p-Ans)(SO2Ph)](dppe)][BArF4] (5) (56.8 mg, 0.033 mmol, 18% yield) as orange crystals. 1H NMR (CD2Cl2): δ 7.88−7.82 (m, 4H, Ph), 7.72 (s, 8H, BArF4), 7.68−7.59 (m, 3H, Ph), 7.57−7.51 (m, 8H, BArF4 + Ph), 7.49−7.43 (m, 8H, Ph), 7.35 (dd, 3JHH = 8.3 Hz, 4JHH = 1.5 Hz, 2H, o-H of SO2Ph), 7.13−7.03 (m, 4H, Ph), 6.04 (d, 3JHH = 8.5 Hz, 2H, m-H of p-Ans), 5.37 (t, 3JPH = 3.4 Hz, 7H, C7H7), 4.51 (d, 3JHH = 8.5 Hz, 2H, o-H of p-Ans), 3.53 (s, 3H, OCH3), 2.61 (br, 2H, dppe), 1.69 (br, 2H, dppe). 31P{1H} NMR (CD2Cl2): δ 57.8 (s, dppe). Selected 13C{1H} NMR (CD2Cl2): δ 356.2 (t, MoCC, 2JCP = 31 Hz), 94.9 (s, C7H7), 55.0 (s, OCH3). Anal. Calcd for C80H55BF24MoO3P2S (5): C, 55.83; H, 3.22. Found: C, 55.70; H, 3.07.
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General procedures; molecular structures of 2b and 2e; NMR charts of the new compounds; details for theoretical calculations; 13C{1H} NMR analysis of the 13 C-labeling experiment; and X-ray crystallographic data for 2d, 2e, 3, and 4 (PDF) Accession Codes
CCDC 1890497−1890500 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing
[email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
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AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. ORCID
Takuya Kuwabara: 0000-0002-5259-0124 Shintaro Kodama: 0000-0003-4190-9539 Youichi Ishii: 0000-0002-1914-7147 Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS This work was supported by JSPS KAKENHI (Nos. 18K05154 and 18K14203). REFERENCES
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