Article pubs.acs.org/IC
Reactivity of 1,3-Disubstituted Indoles with Lithium Compounds: Substituents and Solvents Effects on Coordination and Reactivity of Resulting 1,3-Disubstituted-2-Indolyl Lithium Complexes Liping Guo,†,‡ Shaowu Wang,*,†,§ Yun Wei,† Shuangliu Zhou,† Xiancui Zhu,† and Xiaolong Mu† †
Key Laboratory of Functional Molecular Solids, Ministry of Education, Anhui Laboratory of Molecule-Based Materials, College of Chemistry and Materials Science, Anhui Normal University, Wuhu, Anhui 241000, China ‡ Department of Applied Chemistry and Environmental Engineering, Bengbu College, Bengbu, Anhui 233030, China § State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China S Supporting Information *
ABSTRACT: Reactivity of 1,3-disubstituted indolyl compounds with lithium reagents was studied to reveal the substituents and solvent effects on coordination modes and reactivities resulting in different indolyl lithium complexes. Treatment of 1-alkyl-3-imino functionalized compounds 1-R3-(R′NCH)C8H5N [R = Bn, R′ = Dipp (HL1); R = Bn, R′ = tBu (HL2); R = CH3OCH2, R′ = Dipp (HL3); Dipp = i Pr2C6H3] with Me3SiCH2Li or nBuLi in hydrocarbon solvents (toluene or n-hexane) produced 1,3-disubstituted-2-indolyl lithium complexes [η 1:(μ2 -η1:η1)-1-Bn-3-(DippNCH)C 8 H4 NLi]2 (1), {[η 1:(μ3 -η1 :η 1 :η1 )-1-Bn-3-( t BuNCH)C8H4N][η2:η1:(μ2-η1:η1)-1-Bn-3-(tBuNCH)C8H4N][η1:(μ2-η1:η1)-1-Bn-3-(tBuNCH)C8H4N]Li3} (2), and [η1:η1:(μ2η1:η1)-1-CH3OCH2-3-(DippNCH)C8H4NLi]2 (3), respectively. The bonding modes of the indolyl ligand were kept in 1 by coordination with donor solvent, affording [η1:(μ2-η1:η1)-1-Bn-3-(DippNCH)C8H4NLi(THF)]2 (4). The trinuclear complex 2 was converted to dinuclear form with a change of bonding modes of the indolyl ligand by treatment of 2 with donor solvent THF, producing [η1:(μ2-η1:η1)-1-Bn-3-(tBuNCH)C8H4NLi(THF)]2 (5). X-ray diffraction established that compounds 1, 3, 4, and 5 crystallized as dinuclear structures with the carbanionic sp2 carbon atoms of the indolyl ligands coordinated to lithium ions in a μ2-η1:η1 manner, while compound 2 crystallized as a trinuclear structure and the carbanionic atoms of the indolyl moieties coordinated to lithium ions in μ2-η1:η1 and μ3-η1:η1:η1 manners. When the lithiation reaction of HL1 with 1 equiv of n BuLi was carried out in THF, the monomeric lithium complex {η1:η1-1-Bn-3-(DippNCH)-2-[1′-Bn-3′-(DippNCH)C8H5N]C8H4NLi(THF)} (6) having coupled indolyl moieties was obtained. The compound 6 can also be prepared by the reaction of 1 with 0.5 equiv of HL1 with a higher isolated yield. Accordingly, the lithium complexes [η1:η4-1-Bn-3-tBuNCH-2-(1′-Bn3′-tBuNCHC8H5N)C8H4NLi(L)] (L = THF, 7a; L = Et2O, 7b) with the coupled indolyl moieties in η4 mode were isolated by treatment of HL2 with 2 in THF or Et2O. All complexes were characterized by spectroscopic methods, and their structures were determined by X-ray diffraction study.
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INTRODUCTION Organolithium compounds or reagents are ubiquitous in organic synthesis,1 and they have greatly contributed to the burgeoning field of organometallic chemistry as they were synthons par excellence to generate a huge variety of transition metal complexes via transmetalation or salt metathesis reactions.2 Indole and its derivatives, for their electron-rich properties, have been widely used in transition organometallic chemistry with the finding of multihapto-binding modes (Figure 1).3−6 Indolide-based anionic ligands commonly bind to most metals in the η1 and μ2-η1:η1 modes through the electron-rich nitrogen atom.3 In some circumstances, the η5 bonding modes through the electron-delocalized five-membered heterocyclic ring have © 2017 American Chemical Society
Figure 1. Representative bonding mode of indolyl ligand with metals.
been observed in transition metal4 and s block metal5 complexes, which holds promise for indolide-containing anions to functionalize as alternatives to traditionally used indenyl ligands. Indolide-based anionic ligands can also bind to the Received: January 30, 2017 Published: May 5, 2017 6197
DOI: 10.1021/acs.inorgchem.7b00179 Inorg. Chem. 2017, 56, 6197−6207
Article
Inorganic Chemistry Scheme 1. Preparation of 2-Indolyl Lithium Complexes 1−5
Figure 2. ORTEP diagram of complex 1 with thermal ellipsoids at the 30% probability level. Hydrogen atoms and isopropyl groups on the phenyl groups are omitted for clarity. Selected bond lengths (Å) and angles (deg): Li(1)···Li(2) 2.356(5), C(1)−Li(1) 2.228(4), C(29)−Li(1) 2.247(4), N(2)−Li(1) 2.033(5), C(1)−Li(2) 2.129(5), C(29)−Li(2) 2.219(4), N(4)−Li(2) 1.953(4). C(1)−Li(1)−C(29) 111.3(2), C(1)−Li(2)−C(29) 116.3(2), Li(1)−C(1)−Li(2) 65.41(17), Li(1)−C(29)−Li(2) 63.68(16).
metals in the η3 manner through the nitrogen atom and the fused carbons of indolyl ring.6 Recently, rare-earth metal complexes incorporating functionalized indolyl ligands in novel η1:(μ2-η1:η1),7a μ-η6:η1:η1,7b,c μ-η3:η1:η1, μ-η5:η1:η1, μ-η2:η1:η1,7d and η2:η1-μ-η17e binding modes were found by our group. In contrast to the extensively used 1H-indolyl ligands, Nsubstituted indolyl ligands and their coordinative modes have been less documented. Mulvey reported C-magnesiation at 2position of N-methylindole using (TMEDA)2·Na2MgBu4, and
the N-methylindolyl ligand was found to bind to Mg and Na in η1 and η2 (C2−C3) patterns, respectively.8 Organopalladium complexes supported by N-alkyl indolyl or 1,3-disubstituted SCS pincer indolyl ligands were also reported with the finding of the ligands coordinated to palladium in η1 and η2 (C2−C3) patterns.9 The N-protected indoles can be lithiated at 2position and be functionalized to afford a variety of useful compounds,10 but the structures of these 2-lithiated compounds have not been reported, and solvent effects on the 6198
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Figure 3. ORTEP diagram of complex 2 with thermal ellipsoids at the 30% probability level. Hydrogen atoms, benzyl groups on the indolyl ring nitrogen atoms, tertiary butyl groups connected to the imino nitrogen atoms are omitted for clarity. Selected bond lengths (Å) and angles (deg): Li(1)−C(1) 2.197(4), Li(1)−C(21) 2.342(4), Li(1)−N(4) 1.925(4), Li(1)−N(2) 2.102(4), Li(2)−C(1) 2.231(4), Li(2)−C(21) 2.383(4), Li(2)− C(41) 2.300(4), Li(2)−N(6) 1.978(4), Li(3)−C(21) 2.330(4), Li(3)−C(41) 2.233(4), Li(3)−N(2) 2.115(4). C(2)−N(16) 1.293(3) C(36)−N(4) 1.274(3) C(56)−N(6) 1.283(3) C(1)−Li(1)−C(21) 111.80(17), C(1)−Li(2)−C(21) 109.11(16), C(21)−Li(3)−C(41) 109.87(17), C(21)− Li(2)−C(41) 105.80(15).
C8H4NLi]2 (3), respectively. It should be noted that either Me3SiCH2Li or nBuLi can react with HL1-HL3 and producing the corresponding lithium complexes in almost similar yields. Treatment of 1 or 2 stoichiometrically with donor solvent THF afforded the THF-solvated complexes formulated as [η1:(μ2η1:η1)-1-Bn-3-(DippNCH)C8H4NLi(THF)]2 (4) and [η1: (μ2-η1:η1)-1-Bn-3-(tBuNCH)C8H4NLi(THF)]2 (5). The results indicated that bonding modes of the indolyl ligands in 1 were preserved, while the bonding modes of the indolyl ligands and assembly in 2 were changed when they were treated with THF, suggesting the coordination solvent has effects on the coordination of ligands and assembly of final products (Scheme 1). Complex 1 crystallized from a mixture of toluene and nhexane in triclinic space group P1̅ (Figure 2). X-ray diffraction established that complex 1 existed in a dimeric form in the solid state, in which lithium atoms showed trigonal planar coordination geometry made up by two carbanionic sp2 carbon atoms of indolyl moieties and the nitrogen atoms of the imino groups. The central four-membered ring formed by C1−Li1− C29−Li2 was almost flat (mean deviation: 0.143 Å; the sum of the bond angle is 356.7 (16)°). The Li−Cipso bond length (range 2.13−2.25 Å, with an average of 2.206 Å) was comparable with that found in three-coordinated aryllithium compounds [2-(Me2NCH2)C10H6Li-1]2·L (coordinated L = dman) (av. 2.220 Å)12a and [{Li(Et2O)(2,4,6-(CHMe2)3C6H2)}2] (av. 2.226 Å).12b In comparison with the dimeric complex 1, complex 2 crystallized as a trinuclear with two carbanionic sp2 atoms (C1 and C41) coordinated to lithium centers in μ2-η1:η1 manner and one carbanionic sp2 atom (C21) in a rare μ3-η1:η1:η1
lithiation process have not been documented. Very recently, we have found that reactions of 1-alkyl-3-imino functionalized indoles with M(CH2SiMe3)3(THF)2 (M = Y, Er, Dy) produced the 2-carbon σ bonded indolyl rare-earth metal monoalkyl complexes, which displayed high catalytic activity with excellent 1,4-cis selectivity (1,4-cis content up to 99%) for isoprene polymerization.11 As a part of ongoing work of those 1-alkyl-3imino functionalized 2-carbon σ bonded indolyl ligands used in organometallic chemistry, we wish to report the study of the reactions of 1,3-disubstituted indolyl compounds with lithium reagents to reveal the structural and reactivity diversity depending on substituents on indoles and solvents involved in the reactions.
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RESULTS AND DISCUSSION The 1-alkyl-3-imino functionalized indolyl ligands HL1 and HL2 were prepared according to the methods developed by our group previously.11 The ligand 1-CH3OCH2-3-(DippNCH)C8H5N (HL3) (Dipp = 2,6-iPr2C6H3) can be prepared by the reaction of 1-methoxymethylindole-3-carboxaldehyde with 2,6diisopropylaniline in 48% yield and was characterized by spectroscopic methods and HR-MS analyses. Treatment of 1-alkyl-3-imino functionalized indolyl compounds 1-R-3-(R′NCH)C8H5N [R = Bn, R′ = Dipp (HL1); R = Bn, R′ = tBu (HL2); R = CH3OCH2, R′ = Dipp (HL3)] with 1 equiv of Me3SiCH2Li or nBuLi in hydrocarbon solvents smoothly produced the lithium compounds [η1:(μ2-η1:η1)-1Bn-3-(DippNCH)C8H4NLi]2 (1), {[η1:(μ3-η1:η1:η1)-1-Bn-3(tBuNCH)C8H4N][η2:η1:(μ2-η1:η1)-1-Bn-3-(tBuNCH)C8H4N][η1:(μ2-η1:η1)-1-Bn-3-(tBuNCH)C8H4N]Li3} (2), and [η 1 :η 1 :(μ 2 -η 1 :η 1 )-1-CH 3 OCH 2 -3-(DippNCH)6199
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Figure 4. ORTEP diagram of complexes 3 (left), 4 (middle), and 5 (right) with thermal ellipsoids at the 30% probability level. Hydrogen atoms and isopropyl groups on the phenyl groups are omitted for clarity. Selected bond lengths (Å) and angles (deg): 3, Li(1)···Li(2) 2.588(11) Li(1)−C(3) 2.227(11), Li(2)−C(3) 2.230(11), Li(2)−C(26) 2.267(11), Li(1)−C(26) 2.280(11), Li(1)−N(2) 2.048(10), Li(1)−O(2) 2.080(11), Li(2)−N(4) 2.053(10), Li(2)−O(1) 2.000(10), Li(1)−C(3)−Li(2)71.0(4), Li(1)−C(26)−Li(2) 69.4(4); 4, Li(1)···Li(1i) 2.463(9), Li(1)−C(1) 2.316(5), Li(1)−C(1i) 2.256(5), Li(1)−N(2) 2.122(5), Li(1)−O(1) 2.010(13). C(1i)−Li(1)−C(1) 114.8(2); 5, Li(1)···Li(2) 2.501(12), Li(1)−C(1) 2.294(6), Li(1)−C(1i) 2.294(6), Li(1)−N(2) 2.017(4), Li(1)−N(2i) 2.017(4), Li(2)−C(1) 2.276(5), Li(2)−C(1i) 2.276(5), Li(2)−O(1) 2.021(6), Li(2)−O(1i) 2.021(6).
Figure 5. THF coordinated 1,3-disubstituted-2-indolyl lithium complexes with different bonding modes and geometry.
manner forming an unusual five-coordinate sp2 carbon (Figure 3), and this electron-deficient bonding mode can also been found in methyllithium.15 Furthermore, Li2 and Li3 were coordinated by nitrogen atoms of the imino groups in η1 manner, whereas Li1 engaged in Li−π interaction with the imino moiety (C16−N2) in a η2 manner, which slightly elongated the C16−N2 double bond length (1.293(3) Å) as compared with the observed values in η1 pattern in complex 2 (C36−N4 1.274(3) Å; C56−N6 1.283(3) Å). These results indicated that substituents on the imino groups (tBu vs Dipp) have a significant influence on the bonding modes of the ligands with lithium and assembly of the resulting lithium complexes. The geometries around Li(1) and Li(2) are distorted tetrahedral, whereas Li(3) adopted a trigonal planar coordination configuration. The average Li−Cipso distances in 2 are 2.269 Å (av.) for Li(1), 2.305 Å (av.) for Li(2), and 2.231 Å (av.) for Li(3) respectively, which are comparable with those found in the literature for the ortho-lithium aryl complex [4,6-Me2-2(CH2NMe2)C6H2Li2]·Et2O (av. 2.236 Å, CN = 4; av. 2.157 Å, CN = 3).13d The Li···Li contacts range between 2.361 and 2.601 Å [Li(1)···Li(2) 2.601 Å, Li(1)−Li(3) 2.429 Å, Li(2)− Li(3) 2.361 Å]. X-ray diffraction established that complexes 3, 4, and 5 adopted a dinuclear structure, in which the carbanionic sp2 carbon atoms of the indolyl rings bonded to the lithium centers in μ2-η1:η1manner forming a planar Li2C2 ring (mean deviation: 0.043 Å for 3 and 0.000 Å for both 4 and 5) (Figure 4). Compounds 3, 4, and 5 might have three different geometri-
cally dimeric aggregates in solution, similarly to 2[(dialkylamino)methyl]phenyllithium complexes illustrated by Reich et al. (Figure 5).14a−c In compounds 3 and 4, each lithium atom was coordinated by only one nitrogen atom of the imino group and one oxygen atom from methoxymethyl groups or THF. The orientation of imino groups situated opposite to the Li2C2 plane (Figure 5, Type A). For compound 5, two nitrogen atoms of the imino groups were coordinated to the same lithium atom, and the other lithium were coordinated by two oxygen atoms of THF (Figure 5, Type B). To the best of our knowledge, 5 represents a rare example of verified structure of THF solvated aryllithium complexes with the Type B geometry, which was considered as impossible structure as previous modeling report noted.14e The different stereopatterns between 3, 4, and 5 might be due to the steric difference between Dipp and tBu groups, indicating substituent effects on the bonding of the functionalized indolyl ligands with lithium ions. The Li···Li distance is 2.588(10) Å for 3, 2.463(9) Å for 4, and 2.501 (12) Å for 5, which are comparable to fourcoordinated lithium aryl complex Li[2,6-(NEt2CH2)2C6H3] (Li···Li = 2.483 Å)13a but longer than those found in 2,6bis(oxazolinyl)phenyl supported lithium complexes [Li(Me, Me-Phebox)]2 (2.333(4)Å), 13b [2-Me 2NN(Me)C6H4Li]2· TMEDA (2.393(9) Å),13c and [8-Me2NC10H6LiEt2O] (2.366 (5) Å).13f The Li−Cipso bond length (av. 2.251 Å for 3, 2.286 Å for 4, and 2.285 Å for 5) is longer than that of Li[2,6(NEt 2 CH 2 ) 2 C 6 H 3 ] (av. 2.229 Å) 1 3 a and [2,3,5,6(Me2NCH2)4C6H]Li (2.209 Å).13d,e 6200
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Figure 6. Partial 13C NMR spectra showing the ipso carbon signals of 1 (in C7D8), 3 (in C7D8), 4 (in C6D6), and 5 (in C7D8) at room temperature.
Scheme 2. Formation of Complex 6
aggregation type and enhance its reactivity.16 However, impurity signals appeared around downfield, indicating formation of a byproduct. The result was proved by the following experimental outputs. Reactivity. Originally, we want to prepare complex 4 by carrying out the reaction of HL1 with nBuLi in THF solution under other same conditions; however, the reaction provided a mixture containing part of complex 4 at room temperature as identified by NMR. When HL1 was treated with 1.0 equiv of n BuLi in THF at elevated temperature (50 °C), an unexpected monolithium amido complex 6 having coupled indolyl moieties via 1,4-conjugated addition was isolated (Scheme 2, path A). The result indicated that the reaction of 4, once formed, with HL1 to give coupling compound 6, is at least one order faster than the reaction of HL1 with the nBuLi. Complex 6 can also be prepared by the reaction of HL1 with 0.5 equiv of complex 1 in THF with an improved isolated yield (56% yield) (Scheme 2, Path B), while the reaction of HL1 with 0.5 equiv of complex 1 in toluene did not happen, indicating a solvent effect on the reactivity. The reported intermolecular electrophilic addition at C2 position of indole generally requires control of the
13
C NMR spectra of these complexes at ambient temperature exhibited a broad peak in their ipso carbon signals (192.8 ppm (in C7D8) for 1; 195.5 ppm (in C7D8) for 3; 201.0 ppm (in C6D6) for 4; 196.6 ppm (in C7D8) for 5 (Figure 6)) except 2, whose ipso carbon signal was so weak to be detected. Experiments to verify whether the L3 ligand can also act as a OCN-tridentate in solution as well by determining the 7Li−13C coupling pattern were made. The signal of the ipso carbon atoms showed as a broad singlet, and no splitting and no changes of the resonances were observed even cooling the solution to −80 °C. The results indicated that the ligand acts as a OCN-tridentate in solution (see Supporting Information). It is well-known that the solvents (e.g., hydrocarbon and electron donor solvents) have an effect on the aggregation and reactivity of organolithium reagents. So the reactions of HL1 with 1.0 equiv of Me3SiCH2Li in THF-d8 and C6D6 at room temperature were performed monitored by the NMR technique (see Supporting Information). The results showed the lithium reagent Me3SiCH2Li exhibited enhanced reactivity in THF-d8 than in C6D6, which is in agreement with a previous report like n BuLi that electron donor solvents would destroy its 6201
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Further studies on the reactions of HL2 bearing a tertiary butyl group with one-third equivalent of trinuclear complex 2 in THF or Et2O at elevated temperature also produced the 1,4conjugated addition products 7a and 7b, respectively (Scheme 3). X-ray analyses revealed that 7a and 7b crystallized in the monoclinic with C2/c and P21/c space groups, respectively. In the solid state of 7a and 7b (Figure 8), the lithium center was engaged in metal−ligands π interactions with the C21, C22, C29, and N4 moiety in a η4 manner. Again, substituents (tBu vs Dipp) effects on bonding modes of the ligands with central metal ions were observed. Thus, the geometry of lithium center is best described as a distorted tetrahedral by setting the coordinative interactions with nitrogen atoms on enamine and imino groups, and oxygen atom from solvent molecules THF or Et2O. Before discussion of the observed data in detail, various implication of stereochemical aspects of the coupling compound will be outlined (Figure 9). Apparently, in solution these indolyl coupling complexes existed at least four different stereochemical possibilities, as shown in Figure 9, I, II, III, and IV. The conformations between I and II (also III and IV) can inverse through the O−Li or N−Li coordination−decoordination and C−C single bond rotation processes. For 7b, weak coordination of Et2O allowed the conformations inversion smoothly within the NMR time scale for the weak binding ability of Et2O. Consequently, the 1H NMR spectra of 7b showing the signals of diastereoisomers with the ratio 1:1, which was illustrated by methyl protons of tertiary butyl group and benzyl CH2 protons both exhibited two peaks and resonated at δ 4.36, 5.34 ppm and 1.00, 1.29 ppm, respectively (Figure 10). In the 1H NMR spectra of 7a, the resonances of the protons of the coordinating THF shifted to high field (α-H, 3.07 ppm; β-H, 1.02 ppm), indicating the THF molecule coordinated to lithium tightly in solution,17 which blocked the rotation of the C−C single bond. Complex 7a gave 1H NMR spectra of two diastereomers with four different stereochemical structures (I and II; III and IV). Consequently, this gave rise to the observation of four peaks of benzyl CH2 protons resonated at δ 4.49 ppm, 5.34 ppm, 3.45/4.18 ppm and 5.12/5.72 ppm with the ratio of 1:1:1:1. Meanwhile, the methyl protons of tertiary butyl groups also exhibited four singlets resonance at δ 1.03, 1.05, 1.31, and 1.33 ppm with ratio of 1:1:1:1 (Figure 10). These results can also partially be attributed to the nonclassical hydrogen bond of the benzyl methylene CH 2 proton interaction with the four sp2 hybridized atoms (Figure 11).18
nucleophilicity or formation and stabilization of the indolium intermediate by the choice of proper proton sources.10c In our present case, formation of complex 6 is obviously through 1,4conjugated nucleophilic addition, which is uncommon. This can be attributed to the coordination of nitrogen of the imino group to lithium to make the indole C2 position more electron deficient to make the 1.4-nucleophilic addition reaction happen.
Figure 7. ORTEP diagram of complex 6 with thermal ellipsoids at the 30% probability level. Hydrogen atoms, benzyl group and isopropyl group are omitted for clarity. Selected bond lengths (Å) and angles (deg): C(29)−C(30)1.528(2), C(30)−C(44) 1.359(3), C(44)−N(4) 1.336(3), N(4)−Li(1) 1.945(4), C(1)−C(29), 1.522(3), C(1)−C(2) 1.388(3), C(2)−C(16) 1.437(3), C(16)−N(2) 1.278(2), N(2)−Li(1) 2.023(4), N(4)−Li(1)−N(2) 129.6(2), O(1)−Li(1)−N(4) 120.6(2), O(1)−Li(1)−N(2) 108.84(19).
Complex 6 crystallized in the triclinic space group P1̅, and the geometry of the lithium center is trigonal planar by coordinative interactions with two nitrogen atoms from enamine and imino groups, one oxygen atom from THF. The bond lengths of C29−C30 (1.528(2) Å) and C30−C44 (1.359(3) Å) demonstrated that the double bond of the five number ring of indolyl was weakened to a single bond, and an exocyclic double bond formed. Scheme 3. Preparation of Complexes 7a and 7b.
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Figure 8. ORTEP diagram of 7a (left) and 7b (right) with thermal ellipsoids at the 30% probability level. Hydrogen atoms and benzyl groups are omitted for clarity.
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CONCLUSION In conclusion, we described here the reactivities of 1-alkyl-3imino functionalized indoles with lithium reagents leading to the formation of various indolyl lithium complexes in different aggregating forms having the indolyl ligands bonding with metals in μ2-η1:η1 and rare μ3-η1:η1:η1 modes highly depending on the substituents on the imino groups and the reaction solvents. Further reactivity studies of these lithiated species revealed that the functionalized lithium complexes can perform as nucleophilic reagents to react with 1-alkyl-3-imino indoles to functionalize the C2 position of indolyl ring in polar solvents, and the solvents effects on the stereochemistry were found, which provide a helpful clue for the future study of intermolecular functionalization of C2 position of indolyl ring.
Table 1. Selected Bond Lengths (Å) and Angles (deg) of Structure 7a and 7b 7a C(1)−C(2) C(2)−C(9) C(21)−C(22) C(22)−C(29) C(1)−C(21) C(9)−N(2) C(29)−N(4) Li(1)−C(21) Li(1)−C(22) Li(1)−C(29) Li(1)−N(2) Li(1)−N(4) Li(1)−O(1) N(2)−Li(1)−N(4) N(2)−Li(1)−O(1) N(4)−Li(1)−C(21)
1.521(4) 1.364(4) 1.386(4) 1.458(4) 1.505(4) 1.337(4) 1.270(4) 2.726(6) 2.695(7) 2.683(7) 1.931(6) 2.057(7) 1.947(7) 131.9(4) 124.1(3) 77.8(2)
7b 1.519(4) 1.365(4) 1.390(4) 1.471(4) 1.514(4) 1.335(4) 1.263(3) 2.746(5) 2.691(5) 2.692(5) 1.953(6) 2.060(6) 2.024(6)
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EXPERIMENTAL SECTION
General Procedures. All syntheses and manipulations of air- and moisture-sensitive materials were carried out under an atmosphere of argon using standard Schlenk techniques or in an argon-filled glovebox. THF, toluene, n-hexane, and Et2O were refluxed and distilled over sodium benzophenone ketyl under argon prior to use unless otherwise noted. HL1 and HL2 were synthesized according to the published procedures.11 nBuLi (2.5 M in n-hexane) was purchased from J&K and used as received. 1-Methoxymethylindole-3-carboxaldehyde was prepared following the literature procedure.19 Elemental analyses data were obtained on a Perkin−Elmer model 2400 Series II elemental analyzer. 1H NMR and 13C NMR spectra for analyses of compounds were recorded on Bruker AV-300 (300 MHz for 1H; 75.0 MHz for 13C) or AV-500 NMR spectrometer (500 MHz for 1H; 125 MHz for 13C). Benzene-d6, toluene-d8, and THF-d8 were purchased from Sigma-Aldrich, distilled over Na, and stored in an argon-filled glovebox. Chemical shift (δ) were reported in ppm. J values are reported in Hz. HR-MS measurements were conducted with an Agilent model 6220 ESI-TOF mass spectrometer. IR spectra were recorded on a Shimadzu model FTIR-8400s spectrometer (KBr pellet). Preparation of 1-CH3OCH2-3-(DippNCH)C8H5N (HL3). 1-Methoxymethylindole-3-carboxaldehyde (1.89 g, 10.0 mmol) was dissolved in methanol (30 mL); then 2,6-diisopropylaniline (1.77 g, 10.0 mmol) and a catalytic amount of p-toluenesulfonic acid were added to the solution. The mixture was stirred at 60 °C for 12 h. After
127.0(3) 126.8(3) 76.66(17)
Figure 9. Different stereochemical possibilities of indolyl coupling complexes. 6203
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Inorganic Chemistry
Figure 10. Comparison of 1H NMR spectra between 7a (500 MHz, C7D8) and 7b (500 MHz, C6D6) [the symbols ⧫ and ▼ represented the signal of different diastereomers]. CHMe2), 4.60 (s, 2H, OCH2), 6.67 (s, 1H, H1), 7.09−7.25 (m, 6H), 8.27 (s, 1H), 8.93 (d, J = 6.0 Hz, 1H, H7). 13C NMR (75 MHz, C6D6): δ23.6, 28.3, 55.3, 77.2, 110.3, 116.2, 122.5, 123.2, 123.9, 124.0, 127.0, 133.4, 137.7, 138.0, 151.1, 155.9. HR-MS calcd for C23H28N2O 349.2235, found 349.2234. Anal. Calcd for C23H28N2O: C, 79.27; H, 8.10; N, 8.04. Found: C, 79.52; H, 7.95; N, 7.78. Preparation of [η1:(μ2-η1:η1)-1-Bn-3-(DippNCH)C8H4NLi]2 (1). To a solution of 1.18 g (3.0 mmol) HL1 in toluene (10 mL) was added slowly at ambient temperature a solution of LiCH2SiMe3 (3.85 mL, 0.78 M, 3.0 mmol) or nBuLi (1.2 mL, 2.5 M, 3.0 mmol) in n-hexane. The reaction mixture was stirred at room temperature for about 6 h, after which the suspension was decanted after centrifugation. The residue was washed with n-hexane (10 mL), which afforded a light yellow solid product (1.0 g, 84% yield). Crystals suitable for X-ray analysis were obtained by cooling a saturated solution of 1 in toluene/ n-hexane (2:3 v/v) to 0 °C for several days. 1H NMR (500 MHz, C6D6): δ 1.00 (s, 12H, CHMe2), 3,11 (septet, J = 5.0 Hz, 2H, CHMe2), 4.95 (s, 2H, CH2C6H5), 6.80−6.87 (m, 3H), 6.92−6.93 (d, 2H), 7.10 (m, 3H), 7.13−7.14 (d, 2H), 7.20−7.22 (m, 2H), 7.66 (d, 1H), 8.72 (s, 1H, CHN). 1H NMR (300 MHz, C7D8): δ 0.96 (d, J = 6.0 Hz, 12H, CHMe2), 3.06 (septet. J = 6.0 Hz, 2H, CHMe2), 4.99 (s, 2H, CH2C6H5), 6.82−6.86 (m, 5H), 7.07−7.14 (m, 6H), 7.59 (d, J = 6.0 Hz, 1H), 8.67 (s, 1H, CHN). 13C NMR (75 MHz, C6D6): δ 24.2, 28.2, 53.1, 109.6, 115.7, 120.3, 120.5, 123.6, 124.7, 125.1, 129.4, 132.0, 137.9, 140.9, 142.2, 148.9, 166.4, 191.9 (br, Cipso). 13C NMR (75 MHz, C7D8): δ 24.4, 28.4, 53.4, 109.9, 115.9, 120.4, 120.6, 123.7, 124.9, 127.9, 129.5, 132.2, 137.5, 138.2, 141.1, 142.3, 149.2, 166.5, 192.8 (br, Cipso). Anal. Calcd for C56H58Li2N4:C, 83.97; H, 7.30; N, 6.99. Found: C, 83.92; H, 7.18; N, 7.23. IR (KBr pellets, cm−1): υ 2956 (s), 2864 (s), 1627 (w), 1541 (s), 1465 (w), 1390 (w), 1163 (w), 1043 (s), 854 (s), 744 (w).
Figure 11. Nonclassical hydrogen bond of H34A with C2, C3, C8, and N1. The distance H34A−C2, 2.558 Å; H34A−C3, 2.643 Å; H34A− C8, 2.747 Å; H34A−N1, 2.646 Å. being cooled to room temperature, the methanol was removed under vacuo. The residue was diluted with ethyl acetate (30 mL), washed with saturated Na2CO3 solution (20 mL), and dried over anhydrous Na2SO4. The solvent was evaporated, and the crude product was purified by silica gel column chromatography eluting fast with hexane− EtOAc (10:1 v/v), resulting in the recovery of 1.67 g (48% yield) of the white solid. 1H NMR (300 MHz, C6D6): δ 1.21 (d, J = 6.0 Hz, 12H, CHMe2), 2.61 (s, 3H, CH3O), 3.36 (septet, J = 6.0 Hz, 2H, 6204
DOI: 10.1021/acs.inorgchem.7b00179 Inorg. Chem. 2017, 56, 6197−6207
Article
Inorganic Chemistry Preparation of {[η1:(μ3-η1:η1:η1)-1-Bn-3-(tBuNCH)C8H4N][η2:η1: (μ2-η1:η1)-1-Bn-3-(tBuNCH)C8H4N][η1:(μ2-η1:η1)-1-Bn-3-(tBuN CH)C8H4N]Li3} (2). To a solution of 0.29 g (1.0 mmol) HL2 in toluene (10 mL) was added slowly at ambient temperature a solution of LiCH2SiMe3 (1.28 mL, 0.78 M, 1.0 mmol) or nBuLi (0.4 mL, 2.5 M, 1.0 mmol) in n-hexane. The reaction was stirred at room temperature for about 6 h, and then, the volatile components of the mixture were removed under vacuo. The residue was extracted with n-hexane (15 mL), and the crystals were obtained at 0 °C for several days (0.25 g, 85% yield). 1H NMR (500 MHz, C6D6): δ 0.81 (s, 9H, CMe3), 5.28 (br, 2H, CH2C6H5), 6.74−7.23 (m, 8H), 7.73 (d, 1H), 8.84 (s, 1H, CHN). 13C NMR (75 MHz, C6D6): δ 30.1, 53.7, 55.1, 109.8, 119.7, 120.0, 124.7, 127.3, 128.9, 131.7, 138.8, 142.0, 159.1. Anal. Calcd for C60H63Li3N6: C, 81.06; H, 7.14; N, 9.45. Found: C, 79.93; H, 7.11; N, 9.61.IR (KBr pellets, cm−1): υ 2962 (s), 2877 (s), 1631 (w), 1456 (w), 1355 (s), 1219 (s), 1168 (w), 1012 (s), 964 (s), 736 (w). Preparation of [η1 :η1:(μ2 -η1 :η1 )-1-CH 3 OCH 2 -3-(DippNCH)C8H4NLi]2 (3). To a solution of 0.348 g (1.0 mmol) HL3 in n-hexane (15 mL) was added slowly at ambient temperature a solution of LiCH2SiMe3 (1.28 mL, 0.78 M, 1.0 mmol) or nBuLi (0.4 mL, 2.5 M, 1.0 mmol) in n-hexane. The reaction mixture was stirred at room temperature for about 6 h, after which the suspension was decanted after centrifugation. The residue was washed with n-hexane (10 mL), which afforded a light yellow solid product (0.27 g, 76% yield). Crystals suitable for X-ray analysis were obtained by cooling a saturated solution of 3 in toluene/n-hexane (5:2 v/v) to 0 °C for several days. 1H NMR (500 MHz, C7D8): δ 0.98 (br, 12H, CHMe2), 2.81 (s, 3H, CH3OCH2), 3.10 (septet, J = 5.0 Hz, 2H, CHMe2), 5.05 (s, 2H, CH3OCH2), 6.98 (d, J = 10.0 Hz, 1H, H4), 7.03 (br, 3H), 7.11 (t, J = 5.0 Hz, 1H, H5), 7.17 (t, J = 5.0 Hz, 1H, H6), 7.60 (d, J = 5.0 Hz, 1H, H7), 8.67 (s, 1H, NCH). 13C NMR (125 MHz, C7D8): δ 24.2 (br), 28.4, 57.2, 80.8, 108.4 (C4), 116.1 (C7), 120.1 (C5), 120.7 (C6), 123.6, 124.6, 128.1, 131.7, 140.7, 141.7, 149.9, 166.0, 195.5 (br, Cipso). Anal. Calcd for C46H54Li2N4O2: C, 78.38; H, 7.82; N, 7.95. Found: C, 78.39; H, 7.84; N, 7.92.IR (KBr pellets, cm−1): υ 2958 (w), 2864 (s), 1627 (w), 1543 (s), 1465 (w), 1390 (w), 1161 (w), 1035 (s), 933 (s), 854 (s), 752 (w). Preparation of [η1:(μ2-η1:η1)-1-Bn-3-(DippNCH)C8H4NLi(THF)]2 (4). Complex 1 (0.4 g, 0.5 mmol) was dissolved in THF and the solution was stirred at room temperature about 0.5 h. The solvent was removed under vacuo, which afforded light yellow solid product (0.472 g, 100% yield). Crystals suitable for X-ray analysis were obtained as a hexane solvate by cooling a saturated solution of 4 in toluene/nhexane (1:1 v/v) to 0 °C for several days. 1H NMR (300 MHz, C6D6): δ 1.19 (br, 16H, CHMe2 and β−CH2 THF), 3.22 (m, α−CH2 THF), 3.40 (m, 2H, CHMe2), 5.79 (s, 2H, CH2C6H5), 6.51 (d, J = 6.0 Hz, 2H), 6.96−7.40 (m, 8H), 7.74 (d, J = 6.0 Hz, 1H), 8.99 (s, 1H, CH N). 1H NMR (300 MHz, C7D8): δ 1.15 (br, 16H, CHMe2 and β− CH2 THF), 3.14 (m, α−CH2 THF), 3.28 (septet, J = 6.0 Hz, 2H, CHMe2), 5.64 (s, 2H, CH2C6H5), 6.36 (d, J = 6.0 Hz, 2H), 6.82−6.92 (m, 5H), 7.06 (m, 1H), 7.20−7.29 (m, 3H), 7.60 (d, J = 6.0 Hz, 1H), 8.84 (s, 1H, CHN). 13C NMR (C6D6, 75 MHz): δ 25.2, 27.8, 54.8, 68.3, 110.0, 115.2, 119.8, 120.1, 123.5, 123.7, 124.5, 126.0, 126.2, 128.0, 139.0, 141.1, 141.5, 151.0, 165.5, 201.0 (br, Cipso). 13C NMR (C7D8, 75 MHz): δ 25.5, 28.1, 54.9, 68.4, 111.1, 115.5, 120.0, 120.3, 122.8, 123.7, 126.3, 126.5, 139.2, 141.3, 141.8, 151.1, 165.8. Anal. Calcd for C64H74Li2N4O2:C, 81.33; H, 7.89; N, 5.93. Found: C, 81.37; H, 8.36; N, 5.86. IR (KBr pellets, cm−1): υ 2958 (s), 2862 (s), 1625 (w), 1541 (s), 1465 (w), 1390 (w), 1305 (s), 1163 (w), 1035 (s), 854 (s), 746 (w). Preparation of [η1:(μ2-η1:η1)-1-Bn-3-(tBuNCH)C8H4NLi(THF)]2 (5). Complex 2 was dissolved in THF, and the solution was stirred at room temperature about 0.5 h. The solvent was removed under vacuo, which afforded light yellow solid product quantitatively. Crystals suitable for X-ray analysis were obtained as THF solvate by cooling a saturated solution of 5 in THF/n-hexane (1:4 v/v) to 0 °C for several days. 1H NMR (500 MHz, THF-d8): δ 1.31 (s, 9H, CMe3), 1.79 (m, 4H, β−CH2 THF), 3.64 (m, 4H, α−CH2 THF), 5.48 (s, 2H, CH2C6H5), 6.65 (t, J = 5.0 Hz, 1H), 6.78 (t, J = 5.0 Hz, 1H), 6.96 (d, J = 5.0 Hz, 1H), 7.10−7.18 (m, 5H), 7.43 (d, J = 10.0 Hz, 1H), 8.78 (s,
1H, CHN). 1H NMR (300 MHz, C7D8): δ 1.08 (s, 9H, CMe3), 1.14 (m, 4H, β−CH2 THF), 3.21 (m, 4H, α−CH2 THF), 5.42 (s, 2H, CH2C6H5), 6.92−7.08 (m, 6H), 7.16−7.20 (m, 2H), 7.79 (d, J = 6.0 Hz, 1H), 8.99 (s, 1H, CHN). 13C NMR (125 MHz, C7D8): δ 25.3, 30.6, 54.2, 55.4, 68.2, 109.9, 115.7, 119.3, 119.4, 126.9, 127.0, 132.2, 140.5, 141.8, 158.0, 196.6 (br, Cipso). Anal. Calcd for C48H58Li2N4O2: C, 78.24; H, 7.93; N, 7.60. Found: C, 78.10; H, 8.05; N, 7.92. IR (KBr pellets, cm−1): υ 2962 (s), 2868 (s), 1638 (w), 1465 (w), 1359 (w), 1261 (w), 1097 (w), 802 (w), 738 (s). Preparation of {η 1 :η 1 -1-Bn-3-(DippNCH)-2-[1′-Bn-3′(DippNCH)C8H5N]C8H5NLi(THF)} (6). Path A. To a solution of HL1 (0.394 g, 1.0 mmol) in THF (15 mL) was added slowly a solution of n BuLi (0.2 mL, 2.5 M, 0.5 mmol) in n-hexane at −78 °C. The reaction mixture was warmed to room temperature and stirred at 50 °C for about 12 h. The volatile components of the mixture were removed under vacuo, and the residue was extracted by toluene/n-hexane (6 mL/4 mL). After standing the solution at 0 °C for several days, red rhombic crystals were obtained (0.18 g, 42% yield). Alternative Path B. To a THF (10 mL) solution of complex 1 (0.4 g, 0.5 mmol) was added a THF (10 mL) solution of HL1 (0.394 g, 1.0 mmol). The mixture was stirred for about 12 h at 50 °C, after which the volatile components of the mixture were removed under a vacuum. The residue was extracted by toluene/n-hexane (12 mL/8 mL). The red color crystals were obtained by standing the solution at 0 °C for several days (0.48 g, 56% yield). The 1H NMR signals of complex 5 could not be easily elucidated. Variable temperature (VT) NMR experiment showed that some peaks overlapped when the temperature were raised to 80 °C. Anal. Calcd for C60H67LiN4O: C, 83.11; H, 7.79; N, 6.46. Found: C, 82.80; H, 7.58; N, 6.67. IR (KBr pellets, cm−1): υ 2964 (w), 1656 (w), 1627 (w), 1595 (s), 1533 (s), 1450 (s), 1355 (s), 1319 (s), 1213 (s), 1091 (s), 746 (s). Preparation of [η1:η4-1-Bn-3-tBuNCH-2-(1′-Bn3′-tBuNCHC8H5N)C8H5NLi(THF)] (7a). To a THF (10 mL) solution of complex 2 (0.27 g, 0.3 mmol) was added a THF (10 mL) solution of HL2 (0.26 g, 0.9 mmol). The mixture was stirred for about 12 h at 50 °C, after which the volatile components of the mixture were removed under a vacuum. The residue was extracted by toluene/nhexane (8 mL/2 mL). The red crystals were obtained by storing at 0 °C for several days (0.39 g, 68% yield). 1H NMR (500 MHz, C7D8): δ 1.02 (m, 8H, β−CH2 THF), 1.03 (s, 9H, CMe3), 1.05 (s, 9H, CMe3), 1.31 (s, 9H, CMe3), 1.33 (s, 9H, CMe3), 3.07 (m, 8H, α−CH2 THF), 3.45, 4.18 (AB, J = 15.0 Hz, 2H, CH2C6H5), 4.49 (s, 2H, CH2C6H5), 5.12, 5.72 (AB, J = 15.0 Hz, 2H, CH2C6H5), 5.34 (s, 2H, CH2C6H5), 6.14 (d, J = 10.0 Hz, 1H), 6.47 (s, 1H), 6.68−7.24 (m, 30H), 7.75 (d, J = 5.0 Hz, 1H), 7.99 (s, 1H), 8.31 (s, 1H), 8.44 (s, 1H), 8.64 (br, 1H, CHN), 8.94 (s, 1H, CHN). 13C NMR (C7D8, 125 MHz): δ 25.2, 29.7, 30.2, 30.5, 32.6, 48.2, 49.1, 49.9, 53.3, 54.5, 55.4, 56.9, 58.0, 61.8, 68.0, 89.3, 103.1, 110.0, 110.6, 111.5, 112.8, 115.8, 117.9, 118.0, 119.1, 119.5, 120.4, 121.3, 122.8, 123.1, 123.2, 126.5, 126.7, 127.0, 131.2, 132.1, 136.4, 138.5, 138.7, 139.9, 140.3, 141.8, 142.2, 145.2, 147.5, 154.7, 158.0. Anal. Calcd for C44H51LiN4O: C, 80.21; H, 7.80; N, 8.50. Found: C, 79.83; H, 7.40; N, 8.26. IR (KBr pellets, cm−1): υ 2966 (w), 2874 (s), 1656 (w), 1629 (s), 1608 (s), 1543 (s), 1508 (s), 1452 (s), 1087 (s), 989 (s), 748 (s). Preparation of [η1:η4-1-Bn-3-tBuNCH-2-(1′-Bn3′-tBuNCHC8H5N)C8H5NLi(Et2O)] (7b). This complex was obtained as red crystals in 56% yields following procedures similarly to those used for the preparation of 7a. 1H NMR (500 MHz, C6D6): δ 1.00 (s, 9H, CMe3), 1.09 (t, J = 5.0 Hz, 6H, OCH2CH3), 1.29 (s, 9H, CMe3), 3.22 (q, J = 5.0 Hz, 4H, OCH2CH3), 4.36 (s, 2H, CH2C6H5), 5.34 (s, 2H, CH2C6H5), 6.70−6.72 (m, 2H), 6.84−6.86 (m, 6H), 6.95−6.97 (m, 4H), 7.08−7.15 (m, 4H), 7.22−7.25 (m, 2H), 7.79 (d, J = 10.0 Hz, 1H), 8.45 (s, 1H), 8.93 (s, 1H). 13C NMR (C6D6, 125 MHz): δ 15.5, 30.3, 30.4, 49.9, 54.6, 55.4, 57.1, 65.9, 110.2, 110.3, 116.0, 119.6, 119.7, 121.5, 123.3, 127.0, 128.8, 128.9, 131.0, 132.1, 137.3, 137.6, 139.5, 141.9, 151.1, 158.0. Anal. Calcd for C44H53LiN4O: C, 79.97; H, 8.08; N, 8.48. Found: C, 80.08; H, 8.10; N, 8.50.IR (KBr pellets, cm−1): υ 2968 (w), 2873 (s), 1658 (w), 1629 (s), 1595 (s), 1452 (w), 1361 (s), 1211 (w), 1155 (s), 1018 (s), 904 (s), 742 (w), 700 (s). 6205
DOI: 10.1021/acs.inorgchem.7b00179 Inorg. Chem. 2017, 56, 6197−6207
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Inorganic Chemistry Crystal Structure Analyses of 1−7. A suitable crystal of complexes 1−7 was each mounted in a sealed capillary. Diffraction was performed on a Bruker SMART APEX II CCD area detector diffractometer using a graphite-monochromated Mo−Kα radiation (λ = 0.71073 Å) at 293(2) K, φ and ω scan technique. An empirical absorption correction was applied using the SADABS program.20 All structures were solved by direct methods, completed by subsequent difference Fourier syntheses, and refined anisotropically for all non-hydrogen atoms by full-matrix least-squares calculations based on F2 using the SHELXTL program package.21 The hydrogen atom coordinates were calculated with SHELXTL by using an appropriate riding model with varied thermal parameters. The residual electron densities were of no chemical significance. Some of the structure showed large esd values due to the weak intensity of data for lacking of heavier atom of the molecules.
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Diisobutylaluminum. Organometallics 2010, 29, 5927−5935. (b) Wei, Y.; Wang, S. W.; Zhou, S. L.; Feng, Z. J.; Guo, L. P.; Zhu, X. C.; Mu, X. L.; Yao, F. S. Aluminum Alkyl Complexes Supported by Bidentate N,N Ligands: Synthesis, Structure, and Catalytic Activity for Guanylation of Amines. Organometallics 2015, 34, 1882−1889. (c) Peng, K.; Chen, Y.; Chen, C. Synthesis and catalytic application of magnesium complexes bearing pendant indolyl ligands. Dalton Trans. 2015, 44, 9610−9619. (d) Jia, W.; Liu, Q.; Wang, R.; Wang, S. Novel Phosphorescent Cyclometalated Organotin(IV) and Organolead(IV) Complexes of 2,6-Bis(2′-indolyl)pyridine and 2,6-Bis[2′-(7-azaindolyl)]pyridine. Organometallics 2003, 22, 4070−4078. (e) Karshtedt, D.; McBee, J.; Bell, A.; Tilley, T. Stoichiometric and Catalytic Arene Activations by Platinum Complexes Containing Bidentate Monoanionic NitrogenBased Ligands. Organometallics 2006, 25, 1801−1811. (f) Ho, J.; Black, D.; Messerle, B.; Clegg, J.; Turner, P. Reactive Indolyl Complexes of Group 9 Metals. Organometallics 2006, 25, 5800−5810. (g) Lam, E.; Farrar, D.; Browning, C. S.; Lough, A. Reactions of 2-indolylphosphines with Ru3(CO)12: cluster capping with μ3, η2-indolylphosphine as an anionic six-electron P,N-donor ligand. Dalton Trans. 2004, 3383−3388. (h) Li, G.; Zuccaccia, C.; Tedesco, C.; D’Auria, I.; Macchioni, A.; Pellecchia, C. NMR Spectroscopy and X-Ray Characterisation of Cationic N-Heteroaryl-Pyridylamido ZrIV Complexes: A Further Level of Complexity for the Elusive Active Species of Pyridylamido Olefin Polymerisation Catalysts. Chem. - Eur. J. 2014, 20, 232−244. (i) Wang, J.; Stringer, D.; Gardiner, M.; Skelton, B.; White, A. Synthesis of 2,5-bis{(diethyl-3′-indolyl)methyl}furan and its N,N′dimetallated complexes (lithium, sodium and potassium): X-ray crystal structures of 2,5-bis{(diethyl-3′-indolyl)methyl}furan and the polymeric tetrahydrofuran adduct of the dilithiated complex. J. Organomet. Chem. 2005, 690, 220−227. (4) (a) Suginome, M.; Fu, G. First synthesis and resolution of a planar-chiral tetrahydroindolyl complex of iron: Electronic tuning of reactivity and enantioselective nucleophilic catalysis. Chirality 2000, 12, 318−324. (b) Zhu, G.; Tanski, J.; Churchill, D.; Janak, K.; Parkin, G. The Reactivity of Mo(PMe3)6 towards Heterocyclic Nitrogen Compounds: Transformations Relevant to Hydrodenitrogenation. J. Am. Chem. Soc. 2002, 124, 13658−13659. (c) Parker, K.; Noll, B.; Pierpont, C.; Rakowski DuBois, M. Syntheses of Tantalum(V) Complexes Containing Tetramethylpyrrolyl, Pyrrolyl, and Indolyl Ligands. Inorg. Chem. 1996, 35, 3228−3234. (d) Kulangara, S.; Jabri, A.; Yang, Y.; Korobkov, I.; Gambarotta, S.; Duchateau, R. Synthesis, Xray Structural Analysis, and Ethylene Polymerization Studies of Group IV Metal Heterobimetallic Aluminum-Pyrrolyl Complexes. Organometallics 2012, 31, 6085−6094. (5) Hu, J.; Barbour, L.; Ferdani, R.; Gokel, G. Sodium cation complexation behavior of the heteroaromatic sidechains of histidine and tryptophan. Chem. Commun. 2002, 1810−1811. (6) Evans, W.; Brady, J.; Ziller, J. Flexibility in the Coordination Chemistry of the 2,3-Dimethylindolide Ligand with Potassium, Yttrium, and Samarium. Inorg. Chem. 2002, 41, 3340−3346. (7) (a) Zhu, X. C.; Zhou, S. L.; Wang, S. W.; Wei, Y.; Zhang, L. J.; Wang, F. H.; Wang, S. Y.; Feng, Z. J. Rare-earth metal complexes having an unusual indolyl-1,2-dianion through C-H activation with a novel η1:(μ2-η1:η1) bonding with metals. Chem. Commun. 2012, 48, 12020−12022. (b) Feng, Z. J.; Zhu, X. C.; Wang, S. Y.; Wang, S. W.; Zhou, S. L.; Wei, Y.; Zhang, G. C.; Deng, B. J.; Mu, X. L. Synthesis, Structure, and Reactivity of Lanthanide Complexes Incorporating Indolyl Ligands in Novel Hapticities. Inorg. Chem. 2013, 52, 9549− 9556. (c) Zhang, G. C.; Wang, S. W.; Zhou, S. L.; Wei, Y.; Guo, L. P.; Zhu, X. C.; Zhang, L. J.; Gu, X. X.; Mu, X. L. Synthesis and Reactivity of Rare-Earth-Metal Monoalkyl Complexes Supported by Bidentate Indolyl Ligands and Their High Performance in Isoprene 1,4-cis Polymerization. Organometallics 2015, 34, 4251−4261. (d) Zhang, G. C.; Wei, Y.; Guo, L. P.; Zhu, X. C.; Wang, S. W.; Zhou, S. L.; Mu, X. L. Dinuclear Rare-Earth Metal Alkyl Complexes Supported by Indolyl Ligands in μ-η2:η1:η1 Hapticities and their High Catalytic Activity for Isoprene 1,4-cis-Polymerization. Chem. - Eur. J. 2015, 21, 2519−2526. (e) Zhang, G. C.; Deng, B. J.; Wang, S. W.; Wei, Y.; Zhou, S. L.; Zhu, X. C.; Huang, Z. M.; Mu, X. L. Di and trinuclear rare-earth metal
ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.7b00179. NMR spectra for characterization of new ligands HL3, indolyl lithium complexes 1−6, 7a, and 7b (PDF) Crystallographic information file (CIF)
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AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. ORCID
Shaowu Wang: 0000-0003-1083-1468 Shuangliu Zhou: 0000-0002-0103-294X Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation (21432001, 21372010, 21202002), and the Special and Excellent Research Fund of Anhui Normal University.
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REFERENCES
(1) (a) Rappoport, Z.; Marek, I. The Chemistry of Organolithium Compounds; Wiley-VCH: Weinheim, 2004. (b) Luisi, R.; Capriati, V. Lithium Compounds in Organic Synthesis − From Fundamentals to Applications; Wiley-VCH: Weinheim, 2014. (2) (a) Raith, A.; Altmann, P.; Cokoja, M.; Herrmann, W. A.; Kühn, F. E. η5,η1-Coordinated cyclopentadienyl transition metal complexes featuring σ-metal−carbon ansa bridges. Coord. Chem. Rev. 2010, 254, 608−634. (b) Guo, L.; Zhu, X.; Zhou, S.; Mu, X.; Wang, S.; Feng, Z.; Zhang, G.; Deng, B.; Wei, Y. Rare-earth alkyl complexes supported by formamidinate ligands: synthesis, structure, and catalytic activity for isoprene polymerization. Dalton Trans. 2014, 43, 6842−6847. (c) Alonso, P.; Arauzo, A.; García-Monforte, M.; Martín, A.; Menjón, B.; Rillo, C.; Tomás, M. Homoleptic Organoderivatives of High-Valent Nickel(III). Chem. - Eur. J. 2009, 15, 11020−11030. (d) Moriya, K.; Simon, M.; Mose, R.; Karaghiosoff, K.; Knochel, P. Stereoselective Retentive Domino Transmetalations of Secondary Alkyllithium Compounds to Functionalized Secondary Alkylcopper Reagents. Angew. Chem., Int. Ed. 2015, 54, 10963−10967. (e) Gossage, R.; Jastrzebski, J. T. B. H.; van Koten, G. Hetero-Aggregate Compounds of Aryl and Alkyl Lithium Reagents: A Structurally Intriguing Aspect of Organolithium Chemistry. Angew. Chem., Int. Ed. 2005, 44, 1448−1454. (3) (a) Kingsley, N.; Kirschbaum, K.; Mason, M. Confirmation of Bridging N-Indolides in 3-Methylindole and Di- and Tri(3methylindolyl)methane Complexes of Dimethyl-, Diethyl-, and 6206
DOI: 10.1021/acs.inorgchem.7b00179 Inorg. Chem. 2017, 56, 6197−6207
Article
Inorganic Chemistry
Soc. 1996, 118, 6074−6075. (c) Reich, H. J.; Goldenberg, W. S.; Sanders, A. W.; Jantzi, K. L.; Tzschucke, C. C. Amine- and EtherChelated Aryllithium ReagentsStructure and Dynamics. J. Am. Chem. Soc. 2003, 125, 3509−3521. (d) Jantzi, K. L.; Puckett, C. L.; Guzei, I. A.; Reich, H. J. Solution Structure and Chelation Properties of 2Thienyllithium Reagents. J. Org. Chem. 2005, 70, 7520−7529. (e) Rietveld, M. H. P.; Wehman-Ooyevaar, I. C. M.; Kapteijn, G. M.; Grove, D. M.; Smeets, W. J. J.; Kooijman, H.; Spek, A. L.; van Koten, G. An Aryllithium Complex with Intramolecular Coordination of an o-Diamine Substituent. X-ray and Solution NMR Structures of Dimeric [Li{C6H4(CH2N(Me)CH2CH2NMe2)-2}]2. Organometallics 1994, 13, 3782−3787. (15) (a) Weiss, E.; Lucken, E. A. C. Die kristall- und elektronenstruktur des methyllithiums. J. Organomet. Chem. 1964, 2, 197−205. (b) Weiss, E.; Lambertsen, T.; Schubert, B.; Cockeroft, J. K.; Wiedenmann, A. Ü ber Metallalkyl- und -aryl-Verbindungen, 40 Strukturverfeinerung von Methyllithium durch Neutronenbeugung von (LiCD3)4 bei 1.5 und 290 K. Chem. Ber. 1990, 123, 79−81. (c) Weiss, E.; Hencken, G. Ü ber metall-alkyl-verbindungen: XII. verfeiner ung der kristallstruktur des methyllithiums. J. Organomet. Chem. 1970, 21, 265−268. (16) (a) Reich, H. J.; Borst, J. P. Direct NMR spectroscopic determination of organolithium ion pair structures in THF/HMPA solution. J. Am. Chem. Soc. 1991, 113, 1835−1837. (b) Nichols, M. A.; Williard, P. G. Solid-state structures of n-butyllithium-TMEDA, -THF, and -DME complexes. J. Am. Chem. Soc. 1993, 115, 1568−1572. (c) Barnett, N. D. R.; Muhey, R. E. Butyllithium cubane tetramers linked by Li-TMEDA-Li bridges in an infinite, zig-zag chain arrangement: First crystallographic study of a simple butyl compound of an early main group element. J. Am. Chem. Soc. 1993, 115, 1573− 1574. (d) Bauer, W.; Winchester, W. R.; von Ragué Schleyer, P. Monomeric organolithium compounds in tetrahydrofuran: tertbutyllithium, sec-butyllithium, supermesityllithium, mesityllithium, and phenyllithium. Carbon-lithium coupling constants and the nature of carbon-lithium bonding. Organometallics 1987, 6, 2371−2379. (e) Arink, A. M.; Kronenburg, C. M. P.; Jastrzebski, J. B. H.; Lutz, M.; Spek, A.; Gossage, R. A.; van Koten, G. Diastereoselective SelfAssembly of Chiral Diamine-Chelated Aryllithiums to Dimeric Aggregates. J. Am. Chem. Soc. 2004, 126, 16249−16258. (17) Lu, E. L.; Gan, W.; Chen, Y. F. Monoalkyllanthanide Complexes with New β-Diketiminato Derivative Dianionic Ligands. Organometallics 2009, 28, 2318−2324. (18) (a) Xie, Z. W.; Wang, S. W.; Zhou, Z. Y.; Mak, T. C. W. Synthesis, Reactivity, and Structural Characterization of Organolanthanide Compounds Incorporating both Cyclopentadienyl and Carboranyl Groups. Organometallics 1999, 18, 1641−1652. (b) Ruhlandt-Senge, K.; Ellison, J. J.; Wehmschulte, R. J.; Pauer, F.; Power, P. P. Isolation and structural characterization of unsolvated lithium aryls. J. Am. Chem. Soc. 1993, 115, 11353−11357. (19) Comins, D.; Killpack, M. Lithiation of heterocycles directed by.alpha.-amino alkoxides. J. Org. Chem. 1987, 52, 104−109. (20) Sheldrick, G. M. SADABS: Program for Empirical Absorption Correction of Area Detector Data; University of Göttingen: Germany, 1996. (21) Sheldrick, G. M. SHELXTL 5.10 for Windows NT: Structure Determination Software Programs; Bruker Analytical X-ray Systems, Inc.: Madison, WI, 1997.
complexes supported by 3-amido appended indolyl ligands: synthesis, characterization and catalytic activity towards isoprene 1,4-cis polymerization. Dalton Trans. 2016, 45, 15445−15456. (8) Conway, B.; Hevia, E.; Kennedy, A.; Mulvey, R. Structurallydefined direct C-magnesiation and C-zincation of N-heterocyclic aromatic compounds using alkali-metal-mediated metallation. Chem. Commun. 2007, 2864−2866. (9) (a) Li, Y.; Wang, W.; He, K.; Shi, Z. Mechanistic Insight into the Regioselective Palladation of Indole Derivatives: Tetranuclear Indolyl Palladacycles with High C2−Pd or C3−Pd Bond Selectivity. Organometallics 2012, 31, 4397−4400. (b) Lisena, J.; Monot, J.; Mallet-Ladeira, S.; Martin-Vaca, B.; Bourissou, D. Influence of the Ligand Backbone in Pincer Complexes: Indenediide-, Indolyl-, and Indenyl-Based SCS Palladium Complexes. Organometallics 2013, 32, 4301−4305. (10) (a) Johnson, C.; Stemp, G.; Anand, N.; Stephen, S.; Gallagher, T. Palladium (0)-Catalysed Arylations using Pyrrole and Indole 2Boronic Acids. Synlett 1998, 1998, 1025−1027. (b) Vazquez, E.; Davies, I.; Payack, J. A Non-cryogenic Method for the Preparation of 2-(Indolyl) Borates, Silanes, and Silanols. J. Org. Chem. 2002, 67, 7551−7552. (c) Morimoto, N.; Morioku, K.; Suzuki, H.; Takeuchi, Y.; Nishina, Y. Lewis Acid and Fluoroalcohol Mediated Nucleophilic Addition to the C2 Position of Indoles. Org. Lett. 2016, 18, 2020− 2023. (11) Guo, L. P.; Zhu, X. C.; Zhang, G. C.; Wei, Y.; Ning, L. X.; Zhou, S. L.; Feng, Z. J.; Wang, S. W. W.; Mu, X. L.; Chen, J.; Jiang, Y. Z. Synthesis and Characterization of Organo-Rare-Earth Metal Monoalkyl Complexes Supported by Carbon σ-Bonded Indolyl Ligands: High Specific Isoprene 1,4-Cis Polymerization Catalysts. Inorg. Chem. 2015, 54, 5725−5731. (12) (a) Jastrzebski, J. T. B. H.; Arink, A.; Kleijin, H.; Braam, T.; Lutz, M.; Spek, A.; van Koten, G. Directed ortho-Lithiation: Observation of an Unexpected 1-Lithio to 3-Lithio Conversion of 1Lithio-naphthyllithium Compounds with an ortho-Directing 2(Dimethylamino)methyl Group. J. Am. Chem. Soc. 2013, 135, 13371−13378. (b) Bartlett, R. A.; Dias, H. V. R.; Power, P. P. Isolation and X-ray crystal structures of the organolithium etherate c o m p l e x e s , [ L i ( E t 2 O) 2 ( C P h 3 ) ] a n d [ { L i ( E t 2 O ) ( 2 ,4 , 6 (CHMe2)3C6H2)}2]. J. Organomet. Chem. 1988, 341, 1−9. (13) (a) Schlengermann, R.; Sieler, J.; Jelonek, S.; Hey-Hawkins, E. Different donor binding modes of the pincer ligand 2,6-bis[(diethylamino)-methyl]phenyl: intermolecularly chelating in Li[2,6(NEt2CH2)2C6H3] and both mono- and bi-dentate in BCl2{2[BCl3(NEt2CH2)]-6 -(NEt2CH2)C6H3}. Chem. Commun. 1997, 197−198. (b) Stol, M.; Snelders, D.; de Pater, J.; van Klink, G.; Kooijman, H.; Spek, A.; van Koten, G. Synthesis and Structural Characterization of Lithium and Trimethyltin Complexes of 2,6Bis(oxazolinyl)phenyl. Organometallics 2005, 24, 743−749. (c) Belzner, J.; Schär, D.; Dehnert, U.; Noltemeyer, M. Synthesis and Structure of Aryllithium Compounds Containing ortho-Directing (Dimethylamino)methyl and Trimethylhydrazino Substituents. Organometallics 1997, 16, 285−288. (d) Jastrzebski, J. T. B. H.; van Koten, G.; Konijn, M.; Stam, C. H. Intramolecularly chelated di- and tetranuclear aryllithium compounds: crystal structure of Li4[C6H4(2CH2NMe2)]4 containing 4-center 2-electron-bonded C(aryl) atoms and heptacoordinate lithium atoms. J. Am. Chem. Soc. 1982, 104, 5490−5492. (e) Smeets, W. J. J.; Spek, A. L.; van der Zeijden, A. A. H.; van Koten, G. Structure of {2,3,5,6-Tetrakis[(dimethylamino)methyl]phenyl-C,N,N′}lithium Dimer. Acta Crystallogr., Sect. C: Cryst. Struct. Commun. 1987, 43, 1429−1430. (f) Jastrzebski, J. T. B. H.; van Koten, G.; Goubitz, K.; Arlen, C.; Pfeffer, M. Synthesis of 8-(dimethylamino)1-naphthyllithium etherate: its structure in the solid (X-ray) and in solution (7Li and 1H NMR). J. Organomet. Chem. 1983, 246, C75− C79. (14) (a) Reich, H. J.; Goldenberg, W. S.; Gudmundsson, B. Ö .; Sanders, A. W.; Kulicke, K. J.; Simon, K.; Guzei, I. A. Amine-Chelated Aryllithium ReagentsStructure and Dynamics. J. Am. Chem. Soc. 2001, 123, 8067−8079. (b) Reich, H. J.; Gudmundsson, B. Ö . Solution Structure of 2-[(Dimethylamino)methyl]phenyllithium. J. Am. Chem. 6207
DOI: 10.1021/acs.inorgchem.7b00179 Inorg. Chem. 2017, 56, 6197−6207
