Reactivity of N,C,N-Chelated Antimony(III) and Bismuth(III) Chlorides

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Reactivity of N,C,N-Chelated Antimony(III) and Bismuth(III) Chlorides with Lithium Reagents: Addition vs Substitution Iva Vránová,† Roman Jambor,† Aleš Růzǐ čka,† Robert Jirásko,‡ and Libor Dostál*,† †

Department of General and Inorganic Chemistry and ‡Department of Analytical Chemistry, Faculty of Chemical Technology, University of Pardubice, Studentská 573, Pardubice 53210, Czech Republic S Supporting Information *

ABSTRACT: N,C,N-chelated antimony(III) and bismuth(III) chlorides L1,2MCl2 (1−4: for L1, M = Sb (1), Bi (3); for L2, M = Sb (2), Bi (4)) containing ligands L1,2 (where L1 = C6H3-2,6(CHN-t-Bu)2, L2 = C6H3-2,6-(CHN-2′,6′-Me2C6H3)2) were prepared by reactions of lithium precursors with SbCl3 or BiCl3. The identities of 1−4 were established both in solution (1H and 13C NMR spectroscopy) and, in the case of 1−3, in the solid state using single-crystal X-ray diffraction analysis. Treatment of antimony derivatives 1 and 2 with 2 molar equiv of R′Li (R = Me, n-Bu, Ph) yielded the set of substituted 1,3-(R′)2-2-R-7-(CHNR)-1H-2,1-benzazastiboles 5−10 (where R = t-Bu, 2,6-Me2C6H3 and R′ = Me, n-Bu, Ph) as a result of a nucleophilic attack of one of the lithium compounds across the imino CN functionality. In contrast, analogous reactions between bismuth congeners 2 and 4 and R′Li (2 equiv, R′ = Me, Ph) gave L1,2BiR′2 (11−13: for L1, R′ = Me (11), Ph (12); for L2, R′ = Me (13)) as products of substitution of chlorine atoms. Compounds 5−13 were characterized by the help of 1H and 13C NMR spectroscopy. The molecular structures of 8, 9, and 13 were unambiguously established using single-crystal X-ray diffraction analysis.

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INTRODUCTION The utilization of various types of formally monoanionic C,Yand Y,C,Y-chelating ligands (Y = O, N) in the chemistry of heavier group 15 elements, antimony and bismuth in particular, is a well-known phenomenon and a vast number of compounds was obtained and characterized.1 These compounds often represent unique examples among organoantimony and organobismuth compounds from both a structural and reactivity point of view.2 In spite of this fact, these ligands usually help to thermodynamically stabilize the central atom (Sb or Bi) and play the role of a spectator ligand. Examples of C,Y-chelated compounds, where these ligands take part in any chemical transformation involving the central atom, thus behaving as actor ligands, are rare. In 2011, Jurkschat et al. reported on O,C,O-chelated bismuth(III) compounds showing a pronounced tendency for intramolecular cyclization, giving benzoxabismoles (Scheme 1A).1d We have reported a similar cyclization process via C−O bond cleavage, which was induced by a Lewis acidic antimony atom leading to benzoxastiboles (Scheme 1B).3 Recently, we have discovered that main-groupelement compounds (mainly derived from B, Si, and Sb) chelated by a C,N-ligand that contains an imino (CHN) donor functionality are able to smoothly convert to the respective heterocyclic compounds under particular reaction conditions (Scheme 2).4 These findings proved that C,Nchelating ligands containing analogical imino donor group(s) may behave as actor ligands and further investigation in these field seems to be reasonable. This finding is further supported by a recent achievement by Fischer and Flock et al., who reported on an impressive © XXXX American Chemical Society

Scheme 1. Formation of Benzoxabismole and Benzoxastibole

reactivity of related N,N,N-chelated tin compounds that also contain an imino donor functionality,5 which was later followed by a work of Nikonov et al. on germanium.6 Similarly, interesting results in ligand-centered reactivity were obtained for related N,N-chelated main-group compounds.7 In this work, we present the reactivity of N,C,N-chelated antimony(III) and bismuth(III) chlorides L1,2MCl2 (1−4: for L1, M = Sb (1), Bi (3); for L2, M = Sb (2), Bi (4)), containing pincer type ligands L1,2 (where L1 = C6H3-2,6-(CHN-t-Bu)2, L2 = C6H3-2,6-(CHN-2′,6′-Me2C6H3)2) with organolithium reagents. It is demonstrated that these ligands are able to participate in these reactions in the case of antimony Received: November 25, 2014

A

DOI: 10.1021/om5011879 Organometallics XXXX, XXX, XXX−XXX

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Organometallics Scheme 2. Reactions Leading to Benzazametallacycles

Figure 1. ORTEP plots of molecules of 1·(hexane) (left; the hexane molecule was removed by the squeeze routine of the program Platon (see the Experimental Section)) and 2 (right). Anisotropic displacement parameters are depicted at the 40% probability level. Hydrogen atoms are omitted for clarity. Selected bond lengths (Å) and angles (deg) for 1 (values for 2 are given in brackets): Sb(1)−N(1) 2.415(2) [2.401(5)], Sb(1)−N(2) 2.399(2) [2.428(5)], Sb(1)−C(1) 2.109(4) [2.134(5)], Sb(1)−Cl(1) 2.5971(9) [2.6482(16)], Sb(1)−Cl(2) 2.5833(10) [2.5209(16)], N(1)−Sb(1)−N(2) 146.20(10) [144.68(17)], Cl(1)−Sb(1)−Cl(2) 171.06(3) [167.54(5)].

compounds 1 and 2, when the lithium reagent adds across the CHN bond involved in the structure of the respective ligands. In contrast, these ligands remain intact in analogous reactions between bismuth compounds 3 and 4 and organolithium compounds, giving products of chlorine atom substitution.

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RESULTS AND DISCUSSION The ligand-precursors L1,2Br were prepared according to published procedures.8 Ligand precursors were first lithiated by n-BuLi at low temperature (−78 °C) in THF, and observed lithium precursors were treated in situ with 1 molar equiv of SbCl3 (or BiCl3), giving 1−4 (Scheme 3) as colorless (1 and 3) Scheme 3. Preparation of 1−4

Figure 2. ORTEP plot of a molecule of 3·0.5CHCl3 (the chloroform molecule was removed by the squeeze routine of the program Platon (see the Experimental Section)). Anisotropic displacement parameters are depicted at the 40% probability level. Hydrogen atoms are omitted for clarity. Selected bond lengths (Å) and angles (deg): Bi(1)−N(1) 2.470(7), Bi(1)−N(2) 2.499(6), Bi(1)−C(1) 2.183(7), Bi(1)−Cl(1) 2.662(2), Bi(1)−Cl(2) 2.6890(18), N(1)−Bi(1)−N(2) 142.89(18), Cl(1)−Bi(1)−Cl(2) 172.18(6).

or yellowish crystals (2 and 4) in reasonable yields (59−82%). 1−4 are readily soluble in chlorinated solvents and sparingly soluble in aromatic solvents but insoluble in hexane. The 1H and 13C NMR spectra of 1−4 revealed the expected sets of signals consistent with the proposed structures (Scheme 3; see the Experimental Section). Thus, one set of signals was observed for L1,2 in the corresponding 1H and 13C NMR spectra of 1−4, including one singlet for the CHN group, thereby suggesting symmetrical (pseudo-meridional) coordination of pincer ligands to the central atoms, as observed in the solid state (vide infra). Molecular structures of 1 (as the hexane solvate 1·(hexane)), 2, and 3 (as the chloroform solvate 3·0.5CHCl3) were determined using single-crystal X-ray diffraction analysis and are depicted together with related structural parameters in Figures 1 and 2. Ligands L1,2 are coordinated to the central atom in a pseudo-meridional fashion, as demonstrated by N(1)−M(1)−N(2) bonding angles of 146.20(10), 144.68(17), and 142.89(18)° for 1−3, respectively. The coordination

polyhedron of the central atom is best described as a distorted octahedron, where both nitrogen N(1) and N(2) as well as chlorine Cl(1) and Cl(2) atoms are placed in mutually trans positions. The stereochemically active lone pair of central atoms is then located in the position trans to the ipso carbon atom C(1) of the ligand. This arrangement closely resembles that usually found in related N,C,N-chelated antimony and bismuth halides.9−11 The N−Sb distances (2.415(2) and 2.399(2) Å for 1, 2.401(5) and 2.428(5) Å for 2) are slightly longer than the ∑cov(Sb,N) value of 2.11 Å12 and significantly shorter than the ∑vdW(Sb,N) value of 3.7 Å, thereby proving the presence of strong intramolecular N→Sb interactions. These values are also comparable to the values observed in [C6H3-2,6-(CH2NMe2)2]SbCl29 (2.491(9) and 2.422(8) Å). B

DOI: 10.1021/om5011879 Organometallics XXXX, XXX, XXX−XXX

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Organometallics Analogously, the N−Bi bond distances in 3 (2.470(7) and 2.499(6) Å) in comparison with the ∑cov(Bi,N) = 2.22 Å12 indicate the presence of intramolecular N→Bi interactions and are slightly shorter than those observed for [C6H3-2,6(CH2NMe2)2]BiCl2 (2.561(3) and 2.570(4) Å).10 The reaction of 1 with 2 molar equiv of organolithium compounds R′Li (R′ = Me, n-Bu, Ph) smoothly gave benzazastiboles 5−7 as a result of addition of one of the lithium reagents across the CHN double bond in the structure of the ligand L1 (Scheme 4), while the second goes to

Scheme 5. Reactions of Benzazastiboles 5 and 7 with HCl

Scheme 4. Reactivity of 1−4 with RLi Reagents

expected signals was observed, including one signal for the methine CH(R′)N groups (i.e., quartet for 5a (R′ = Me) at 4.49 ppm, singlet for 7a (R′ = Ph) at 4.82 ppm in the 1H NMR spectra and singlets at 64.2 and 64.0 ppm for 5a and 7a, respectively, in the 13C NMR spectra). Importantly, one signal was observed also for the NH group at 7.20 (5a) and 6.69 (7a) ppm in the 1H NMR spectra. Finally, the molecular structure of 7a (as the chloroform solvate 7a·2CHCl3) was unambiguously determined by single-crystal X-ray diffraction analysis and the molecular structure is shown in Figure 3. It crystallizes in the

the antimony atom. A plausible mechanism of this reaction is most probably analogous to that described by us recently for the formation of related benzazaboroles.4b It is also important to note that the variation of stoichiometry resulted only in the observation of a mixture of products. Unfortunately, benzazastiboles 5−7 were obtained as oily materials, which hampered the determination of molecular structures by the help of single-crystal X-ray diffraction analysis. Similarly, their isolation as analytically pure samples failed. Nevertheless, the identities of 5 −7 were suggested by 1H and 13C NMR spectroscopy (see the Experimental Section and the Supporting Information). The 1H NMR spectra revealed typical signals for the methine CH(R′)N group within the benzazastibole core (at 4.71 ppm for 5, 4.60 ppm for 6, and 5.59 and 6.13 ppm for 713), importantly with the expected multiplicity (i.e., quartet for 5 (R′ = Me), triplet for 6 (R′ = n-Bu), and singlet for 7 (R′ = Ph)). These signals were observed in a mutual 1:1 integral ratio with the remaining CHN proton. Furthermore, two signals were detected for t-Bu groups in a 1:1 integral ratio, thereby proving their nonequivalency. Similarly, the 13C NMR spectra of 5−7 established the presence of the methine CH(R′)N group in the benzazastibole ring (at 64.2 ppm for 5, 68.8 ppm for 6, and 72.2 and 72.4 ppm for 713). All of these NMR data closely resemble those observed by us for related benzazaboroles4b and prove the closure of benzazastibole rings in 5−7. In order to further substantiate the formation of benzazastiboles 5 and 7, they were treated with 1 molar equiv of HCl, giving compounds 5a and 7a (Scheme 5) as a result of the cleavage of the Sb−N bond of the benzazastibole core.14 A similar approach was used by us to cleave the Sb−N bond in related benzazastiboles.15 5a and 7a were obtained as colorless solids in high yields, and their identity was unambiguously established by ESI-mass spectrometry, where [M − Cl]+ ions were formed in accordance with the literature.16 IR spectra of 5a and 7a showed a broad absorption band at 3364 cm−1, confirming the presence of the NH group in the molecule. The identities of 5a and 7a were also established by 1H and 13C NMR spectroscopy, where one set of

Figure 3. ORTEP plot of a molecule of 7a·2CHCl3. Anisotropic displacement parameters are depicted at the 40% probability level. Hydrogen atoms, except for the C(7)H, C(12)H, and N(2)H groups, and the chloroform solvate molecule are omitted for clarity. Symmetry operator: (a) x, 1/2 − y, 1/2 + z. Selected bond lengths (Å) and angles (deg): Sb(1)−N(1) 2.4086(18), Sb(1)−N(2) 2.4157(18), Sb(1)− C(1) 2.099(2), C(7)−N(1) 1.275(3), C(12)−N(2) 1.490(3), N(2)Cl(1a) 3.238(3), N(1)−Sb(1)−N(2) 148.23(6), C(1)−Sb(1)−C(23) 93.83(10), N(2)−H(N2)−Cl(1a) 165.

space group P21/c as a pair of diastereoisomers (two independent molecules are present in the unit cell) with stereogenic centers, where one is located at the C(12) atom and the second one on the N(2) atom connected to the stereochemically active Sb(1) atom. Compound 7a exists as an ionic pair in the solid state formed by an organoantimony(III) cation and the chloride counteranion. The contact between the central Sb(1) atom and Cl(1a) is 3.7387(8) Å, which indeed indicates only a negligible interaction (∑vdW(Sb,Cl) = 3.9 Å). The Cl(1a) atom forms a hydrogen bond with the N(2)H group that is characterized by the Cl(1a)−N(2) bond length 3.238(3) Å and the Cl(1a)− H(N2)−N(2) bond angle 165°. There is also an additional contact between Cl(1a) and the hydrogen atom of the chloroform solvate molecule. Regarding the structure of the cation, the central Sb(1) atom is four-coordinated and, as the result of the presence of a stereochemically active lone pair, the coordination environment around the Sb(1) atom may be described as having a seesaw geometry (i.e., a trigonal C

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Organometallics bipyramid with a vacant equatorial site). Analogous structures were obtained also for related N,C,N- and O,C,O-chelated antimony(III) cations.17 The Sb(1)−N(1) (2.4086(18) Å) and Sb(1)−N(2) (2.4157(18) Å) bond distances in 7a are also comparable with those observed in the ionic pair [C6H3-2,6(CH2NMe2)2SbCl]+[CB11H12]− (2.379(5) and 2.422(4) Å).17b Importantly, the bond length C(12)−N(2) (1.490(3) Å) corresponds to a C−N single bond (∑cov(C,N) = 1.46 Å12), but C(7)−N(1) bond retains its double bond character as demonstrated by the bond length 1.275(3) Å (for double bond ∑cov(C,N) = 1.27 Å12). The reaction between 2, containing the more bulky ligand L2, and lithium reagents yielded benzazastiboles 8−10 as analytically pure crystalline materials (Scheme 4) by a reaction path similar to that described for the formation of 5−7. 8−10 were characterized mainly by 1H and 13C NMR spectroscopy, and all data resemble those observed for benzazastiboles 5−7. The addition of 1 equiv of R′Li lithium reagent to the CHN bond was proven especially by the observation of signals of the methine CH(R′)N groups (i.e., quartet for 8 (R′ = Me) at 4.76 and 5.46 ppm, triplet for 9 (R′ = n-Bu) at 4.85 and 5.54 ppm, and singlet for 10 (R′ = Ph) at 5.81 and 6.43 ppm13) in the corresponding 1H NMR spectra. Analogously, signals due to the methine carbon atom in CH(R′)N moiety (in the range 70.9−77.9 ppm for 8−10) were detected in 13C NMR spectra. Two sets of signals were also detected for magnetically nonequivalent 2,6-Me2C6H3 moieties. The molecular structures of 8 and 10 were unambiguously established using single-crystal X-ray diffraction analysis, and the respective molecular structures of 8 and 10 are depicted in Figures 4 and 5. Both compounds crystallize in the space group

Figure 5. ORTEP plot of a molecule of 10. Anisotropic displacement parameters are depicted at the 40% probability level. Hydrogen atoms, except for the C(7)H and C(16)H groups, are omitted for clarity. Selected bond lengths (Å) and angles (deg): Sb(1)−N(1) 2.727(3), Sb(1)−N(2) 2.077(3), Sb(1)−C(1) 2.114(3), Sb(1)−C(31) 2.160(3), C(7)−N(1) 1.262(6), C(16)−N(2) 1.459(5), N(1)− Sb(1)−N(2) 147.69(11), C(1)−Sb(1)−C(31) 95.12(12), C(1)− Sb(1)−N(2) 78.95(13), Sb(1)−C(1)−C(6) 114.5(2), C(1)−C(6)− C(16) 119.0(3), C(6)−C(16)−N(2) 108.5(3), C(16)−N(2)−Sb(1) 118.5(2).

N(1) bonds retain their double-bond character, as demonstrated by bond lengths 1.279(6) (8) and 1.262(6) Å (10) (for double bond ∑cov(C,N) = 1.27 Å12). The Sb(1)−N(2) bond lengths 2.080(4) and 2.077(3) Å for 8 and 10, respectively, are comparable to the value ∑cov(Sb,N) = 2.11 Å,12 thereby proving formation of a Sb−N bond. The central antimony atom in 8 and 10 adopts a seesaw coordination environment. In contrast, the Sb(1)−N(1) distances (2.801(4) Å for 8 and 2.727(3) Å for 10) indicate the presence of a weak intramolecular N→Sb interaction. The central benzazastibole rings (including the fused phenyl ring) are essentially planar in 8 and 10. In contrast to the antimony compounds 1 and 2, analogous reactions between bismuth compound 3 (or 4) and MeLi (or PhLi) provided compounds 11−13 (Scheme 4) as a result of substitution. The 1H and 13C NMR spectra of 11−13 revealed an expected set of signals for the ligands L1,2 with no evidence for the formation of benzazabismoles (see the Experimental Section). The molecular structure of 13 was determined by single-crystal X-ray diffraction analysis and is shown in Figure 6. The central Bi(1) atom in 13 is found in a trigonal-pyramidal array, as demonstrated by the sum of C−Bi−C bonding angles of 279.69°. The N(2) atom is out of the primary coordination

Figure 4. ORTEP plot of a molecule of 8. Anisotropic displacement parameters are depicted at the 40% probability level. Hydrogen atoms, except for the C(7)H and C(16)H groups, are omitted for clarity. Selected bond lengths (Å) and angles (deg): Sb(1)−N(1) 2.801(4), Sb(1)−N(2) 2.080(4), Sb(1)−C(1) 2.123(4), Sb(1)−C(26) 2.132(6), C(7)−N(1) 1.279(6), C(16)−N(2) 1.470(6), N(1)− Sb(1)−N(2) 146.61(14), C(1)−Sb(1)−C(26) 97.08(19), C(1)− Sb(1)−N(2) 79.83(15), Sb(1)−C(1)−C(6) 114.0(3), C(1)−C(6)− C(16) 118.8(4), C(6)−C(16)−N(2) 110.1(4), C(16)−N(2)−Sb(1) 117.0(3).

P21/c as a pair of diastereoisomers (two independent molecules are present in the unit cell) with two stereogenic centers located at the C(16) and Sb(1) atoms. The results of structural analysis unambiguously proved the formation of benzazastibole rings, and as a result of the addition of the lithium reagent across the imino CHN bond, the coordination geometry around the C(16) atom is distorted tetrahedral, while the coordination environment around the C(7) atom remains essentially trigonal planar. C(16)−N(2) bond lengths of 1.470(6) and 1.459(5) Å for 8 and 10, respectively, correspond to a C−N single bond (∑cov(C,N) = 1.46 Å12), but C(7)−

Figure 6. ORTEP plot of a molecule of 13. Anisotropic displacement parameters are depicted at the 40% probability level. Hydrogen atoms are omitted for clarity. Selected bond lengths (Å) and angles (deg): Bi(1)−N(1) 3.059(3), Bi(1)−N(2) 4.633(3), Bi(1)−C(1) 2.296(3), Bi(1)−C(25) 2.249(5), Bi(1)−C(26) 2.267(4), C(1)−Bi(1)−C(25) 97.67(14), C(1)−Bi(1)−C(26) 93.47(14), C(25)−Bi(1)−C(26) 88.55(16). D

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Organometallics

obtain a yellow extract. The solution was slowly (during 1 day) evaporated, giving yellowish single crystals of 1·(hexane) (suitable for X-ray diffraction analysis). These crystals were dried in vacuo, leading to the removal of hexane solvate molecules to give 1. Yield: 1.98 g (82%). Mp: 224 °C. Anal. Calcd for C16H23Cl2N2Sb (MW 436.03): C, 44.1; H, 5.3. Found: C, 44.3; H, 5.6. 1H NMR (400 MHz, CDCl3): δ 1.63 (s, 18H, C(CH3)3), 7.62 (t, 3JH−H = 7.2 Hz, 1H, Ar-H4), 7.81 (d, 3 JH−H = 7.2 Hζ, 2H, Ar-H3,5), 8.75 (s, 2H, CHN) ppm. 13C NMR (100.61 MHz, CDCl3): δ 30.7 (s, C(CH3)3), 61.8 (s, C(CH3)3), 130.2 (s, Ar-C4), 133.7 (s, Ar-C3,5), 138.0 (s, Ar-C2,6), 160.8 (s, CHN), 162.0 (s, Ar-C1) ppm. Synthesis of [2,6-(CHN-2′,6′-Me2C6H3)2C6H3]SbCl2 (2). A hexane solution of n-BuLi (1.8 mL, 3.0 mmol, 1.6 M solution) was added to a precooled (−78 °C) yellow solution of 2,6-(2′,6′Me2C6H3NCH)2C6H3Br (1.24 g, 3.0 mmol) in THF (30 mL), and the mixture was stirred for 1 h at −70 °C and then warmed to −40 °C. The resulting red solution was added to a precooled solution (−40 °C) of SbCl3 (0.675 g, 3.0 mmol) in THF (30 mL). The reaction mixture was stirred for 1 day at room temperature and then evaporated in vacuo. The isolation was carried out in air. The solid was extracted with dichloromethane (30 mL), and hexane (10 mL) was added to the orange extract. The solution slowly evaporated, giving orange single crystals of 2 (suitable for X-ray diffraction analysis), which were filtered off and dried in vacuo. Yield: 1.20 g (76%). Mp: 164 °C with decomposition. Anal. Calcd for C24H23Cl2N2Sb (MW 532.12): C, 54.2; H, 4.4. Found: C, 54.0; H, 4.3. 1H NMR (400 MHz, CDCl3): δ 2.49 (s, 12H, CH3), 7.15 (s, 6H, NC6H3), 7.78 (t, 3JH−H = 7.6 Hz, 1H Ar-H4), 8.06 (d, 3JH−H = 7.6 Hz, 2H, Ar-H3,5), 8.82 (s, 2H, CHN) ppm. 13C NMR (100.61 MHz, CDCl3): δ 20.2 (s, CH3), 127.6, 129.3, 130.5, 131.5, 135.7, 137.1, 145.4, 167.4 (s, Ar-C), 167.2 (s, Ar-C1), 169.6 (s, CHN) ppm. Synthesis of [2,6-(CHN-t-Bu)2C6H3]BiCl2 (3). A hexane solution of n-BuLi (3.0 mL, 4.8 mmol, 1.6 M solution) was added to a precooled (−78 °C) colorless solution of 2,6-(t-BuN CH)2C6H3Br (1.54 g, 4.8 mmol) in THF (30 mL) and stirred for 1 h at −70 °C and then warmed to −40 °C. The resulting orange solution was added to a precooled solution (−40 °C) of BiCl3 (1.502 g, 4.8 mmol) in THF (30 mL). The reaction mixture was stirred for 1 day at room temperature and then evaporated in vacuo. The isolation was carried out in air. The solid was extracted with chloroform (30 mL), and hexane (10 mL) was added to the colorless extract. The solution was slowly (several hours) evaporated, giving colorless crystals of 3·0.5CHCl3. These crystals were dried in vacuo, leading to the removal of chloroform solvate molecules to give 3. Yield: 1.62 g (65%). Mp: 172 °C. Anal. Calcd for C16H23Cl2N2Bi (MW 523.25): C, 36.7; H, 4.4. Found: C, 36.8; H, 4.5. 1H NMR (400 MHz, CDCl3): δ 1.58 (s, 18H, C(CH3)3), 7.84 (t, 3JH−H = 7.2 Hz, 1H, Ar-H4), 8.16 (d, 3 JH−H = 7.2 Hζ, 2H, Ar-H3,5), 9.62 (s, 2H, CHN) ppm. 13C NMR (100.61 MHz, CDCl3): δ 30.9 (s, C(CH3)3), 61.9 (s, C(CH3)3), 129.6 (s, Ar-C4), 136.3 (s, Ar-C3,5), 148.5 (s, Ar-C2,6), 167.0 (s, CHN), 208.8 (s, Ar-C1) ppm. Synthesis of [2,6-(CHN-2′,6′-Me2C6H3)2C6H3]BiCl2 (4). A hexane solution of n-BuLi (1.7 mL, 2.7 mmol, 1.6 M solution) was added to a precooled (−78 °C) yellow solution of 2,6-(2′,6′Me2C6H3NCH)2-C6H3Br (1.13 g, 2.7 mmol) in THF (30 mL), and the mixture was stirred for 1 h at −70 °C and then warmed to −40 °C. The resulting red solution was added to a precooled solution (−40 °C) of BiCl3 (0.850 g, 2.7 mmol) in THF (30 mL). The reaction mixture was stirred for 1 day at room temperature and evaporated in vacuo. The isolation was carried out in air. The solid was extracted with dichloromethane (30 mL), and hexane (10 mL) was added to the orange extract. The solution was slowly evaporated, giving yellow crystals of 4, which were filtered off and dried in vacuo. Yield: 0.99 g (59%). Mp: 145 °C with decomposition. Anal. Calcd for C24H23Cl2N2Bi (MW 619.34): C, 46.5; H, 3.7. Found: C, 46.7; H, 3.7. 1H NMR (400 MHz, CDCl3): δ 2.45 (s, 12H, CH3), 7.15 (m, 6H, NC6H3), 8.01 (t, 3JH−H = 7.6 Hζ, 1H, Ar-H4), 8.46 (d, 3JH−H = 7.6 Hζ, 2H, Ar-H3,5), 9.64 (s, 2H, CHN) ppm. 13C NMR (100.61 MHz, CDCl3): δ 20.1 (s, CH3), 127.3, 129.2, 129.9, 130.9, 138.4, 146.6, 147.0, (s, Ar-C), 176.2 (s, CHN) ppm, Ar-C1 not observed.

sphere of the bismuth atom (Bi(1)−N(2) 4.633(3) Å), and the Bi(1)−N(1) distance of 3.059(3) Å indicates only a negligible intramolecular interaction in comparison with ∑cov(Bi,N) = 2.22 Å.12 Surprisingly, there is, to the best of our knowledge, no example of a structurally authenticated aryl(dimethyl)bismuth(III) compound and there exist only a limited number of structurally characterized dimethylbismuth(III) compounds of the general formula Me2BiX (X = N3,18 Br,19 OMe20). All of them form infinite polymeric chain structures in the solid state, where the polar groups play the role of the bridging ligand. There are also two examples of transition-metal-stabilized trimethylbismuth compounds: namely, Me3BiM(CO)5 (X = Cr, W21). In light of these facts, compound 13 represents a significant contribution to the structurally characterized methylbismuth compounds.

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CONCLUSIONS We have demonstrated that in the reaction between N,C,Nchelated antimony(III) compounds with 2 molar equiv of RLi (R = Me, n-Bu, Ph) one of the lithium reagents is able to smoothly add across the CHN imino functionality, leading to the formation of substituted benzazastiboles. This finding paves a new and straightforward path for the formation of azastibaheterocyclic compounds. In contrast, this reaction is not useful for the N,C,N-chelated bismuth(III) compounds, where the substitution of the chlorine atoms by lithium compounds was obtained. The reactivity of prepared benzazastiboles as well as the potential application of the synthetic strategy reported here for the preparation of other heterocyclic compounds is currently underway in our laboratories.

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EXPERIMENTAL SECTION

All air- and moisture-sensitive manipulations were carried out under an argon atmosphere using standard Schlenk tube techniques. All solvents were dried using Pure Solv-Innovative Technology equipment, and THF was further distilled from Na/benzophenone mixture prior to use. 1H and 13C NMR spectra were recorded on a Bruker 400 MHz spectrometer, using a 5 mm tunable broad-band probe. Appropriate chemical shifts in 1H and 13C NMR spectra were related to the residual signals of the solvent (CDCl3, δ(1H) 7.27 ppm and δ(13C) 77.23 ppm; C6D6, δ(1H) 7.16 ppm and δ(13C) 128.39 ppm). The starting compounds SbCl3 (99.999%), BiCl3 (99.999%), MeLi 1.6 M solution in diethyl ether, n-BuLi 1.6 M solution in hexane, and PhLi 1.7 M solution in dibutyl ether were obtained from commercial suppliers and used as delivered. The ligands L1Br and L2Br were prepared according to the published procedures.8 Elemental analyses were performed on an LECO-CHNS-932 analyzer. Positive-ion electrospray ionization (ESI) mass spectra were measured on an Esquire 3000 ion trap analyzer (Bruker Daltonics, Bremen, Germany) in the range m/z 50− 1000. Samples were dissolved in acetonitrile and analyzed by direct infusion at a flow rate of 5 μL/min. The ion source temperature was 300 °C, the tuning parameter compound stability was 100%, and the flow rate and the pressure of nitrogen were 4 L/min and 10 psi, respectively. Infrared spectra were recorded in the 4000−350 cm−1 region on a Nicolet 6700 FTIR spectrometer using the diamond ATR technique. Synthesis of [2,6-(CHN-t-Bu)2C6H3]SbCl2 (1). A hexane solution of n-BuLi (3.46 mL, 5.5 mmol, 1.6 M solution) was added to a precooled (−78 °C) colorless solution of 2,6-(t-BuN CH)2C6H3Br (1.79 g, 5.5 mmol) in THF (30 mL) and stirred for 1 h at −70 °C and then warmed to −40 °C. The resulting orange solution was added to a precooled solution (−40 °C) of SbCl3 (1.262 g, 5.5 mmol) in THF (30 mL). The reaction mixture was stirred for 1 day at room temperature and evaporated in vacuo. The remaining steps were carried out in air. The solid was extracted with dichloromethane (30 mL), and then hexane (10 mL) was added to E

DOI: 10.1021/om5011879 Organometallics XXXX, XXX, XXX−XXX

Article

Organometallics

C1) ppm. IR (cm−1): 3364 [m-br, ν(NH)], 1610 [vs, ν(CN)]. Raman (cm−1): 3365 [w, ν(NH)], 1611 [m, ν(CN)]. Positive-ion MS: m/z 395 [M − Cl]+, 100%. Synthesis of {[2-(CHN-t-Bu)-6-(CH(Ph)N-t-Bu)C6H3]SbPh}+Cl− (7a). A dioxane solution of HCl (0.18 mL, 0.7 mmol, 4 M solution) was added to a slightly yellow solution of 7 (0.364 g, 0.7 mmol) in hexane (20 mL) at room temperature. A white precipitate formed immediately, and the reaction mixture was stirred for 1 h at room temperature. The resulting white suspension was filtered, and the solid was dried in vacuo, giving compound 7. X-ray-quality crystals of 7a· 2CHCl3 were grown from a chloroform/hexane 2/1 mixture. Yield: 0.319 g (82%). Mp: 211 °C with decomposition. Anal. Calcd for C28H34ClN2Sb (MW 555.80): C, 60.5; H, 6.2. Found: C, 60.8; H, 6.5. 1 H NMR (400 MHz, CDCl3): δ 0.94 (s, 9H, C(CH3)3) 1.15 (s, 9H, C(CH3)3), 4.82 (d, 3JH−H = 11.2 Hζ, 1H, NCH(C6H5)), 6.69 (d, 3JH−H = 7.6 Hz, 1H, NH), 7.23−7.75 (m, 13H, Ar-H), 8.64 (s, 1H, CHN) ppm. 13C NMR (100.61 MHz, C6D6): δ 30.4 (s, C(CH3)3), 31.0 (s, C(CH3)3), 57.5 overlap of two signals (s, C(CH3)3), 64.0 (s, NCH(C6H5)), 128.5, 129.4, 129.7, 130.1, 130.4, 130.7, 130.9, 131.9, 135.9, 139.9, 141.6, 142.1, 143.3 (s, Ar-C), 152.2 (s, Ar-C1), 162.8 (s, CHN) ppm. IR (cm−1): 3364 [w-br, ν(NH)], 1613 [vs, ν(CN)]. Raman (cm−1): 1613 [m, ν(CN)]. Positive-ion MS: m/z 519 [M − Cl]+, 100%. Synthesis of 1,3-Me2-2-(2′,6′-Me2C6H3)-7-(CHN-2′,6′-Me2C6H3)1H-2,1-benzazastibole (8). A 0.78 mL portion (1.2 mmol) of a 1.6 M solution of MeLi in diethyl ether was added to 0.331 g (0.6 mmol) of 2. The yellow hexane extract was concentrated to one-third of the original volume. The solution was stored at −30 °C to give yellow single crystals of 8 (suitable for X-ray diffraction analysis). Yield: 0.27 g (89%). Mp: 160 °C. Anal. Calcd for C26H29N2Sb (MW 491.28): C, 63.6; H, 6.0. Found: C, 63.8; H, 6.2. 1H NMR (400 MHz, C6D6): major set of signals δ 1.10 (s, 3H, SbCH3), 1.37 (d, 3JH−H = 6.8 Hz, 3H, NCH(CH3)), 2.01 (s, 6H, C6H3(CH3)2), 2.11 (s, 3H, C6H3(CH3)2), 2.51 (s, 3H, C6H3(CH3)2), 4.76 (q, 3JH−H = 6.8 Hz, 1H, NCH(CH3)), 6.90−7.03 (m, 9H, Ar-H and C6H3(CH3)2), 7.62 (s, 1H, CHN); minor set of signals δ 0.83 (s, 3H, SbCH3), 1.23 (d, 3 JH−H = 6.4 Hz, 3H, NCH(CH3)), 1.88 (s, 6H, C6H3(CH3)2), 2.34 (s, 3H, C6H3(CH3)2), 2.57 (s, 3H, C6H3(CH3)2), 5.46 (q, 3JH−H = 6.4 Hζ, 1H, NCH(CH3)), 6.90−7.03 (m, 9H, Ar-H and C6H3(CH3)2), 7.63 (s, 1H, CHN) ppm. 13C NMR (100.61 MHz, C6D6): δ 10.7 (s, Sb(CH3)2), 19.2, 19.9, 21.6, 29.1 (s, C6H3(CH3)2 and NCH(CH3)), 70.9 (s, NCH(CH3)), 124.1, 125.1, 128.3, 128.8, 128.9, 129.0, 129.9, 130.3, 137.5, 138.7, 138.8, 146.4, 150.5, 152.4, 158.6 (s, Ar-C and C6H3(CH3)2), 165.1 (s, CHN) ppm, Ar-C1 not observed. Synthesis of 1,3-n-Bu 2 -2-(2′,6′-Me 2 C 6 H 3 )-7-(CHN-2′,6′Me2C6H3)-1H-2,1-benzazastibole (9). A 0.51 mL portion (0.8 mmol) of a 1.6 M solution of n-BuLi in hexane was added to 0.217 g (0.4 mmol) of 2. The yellow hexane extract was evaporated in vacuo to give yellow crystals of 9. Yield: 0.15 g (65%). Mp: 168 °C. Anal. Calcd for C32H41N2Sb (MW 575.44): C, 66.8; H, 7.2. Found: C, 66.9; H, 7.4. 1H NMR (400 MHz, C6D6): major set of signals δ 0.88−1.83 (m, 18H, SbC4H9 and NCH(C4H9)), 2.04 (s, 6H, C6H3(CH3)2), 2.12 (s, 3H, C6H3(CH3)2), 2.63 (s, 3H, C6H3(CH3)2), 4.85 (t, 3JH−H = 4.4 Hz, 1H, NCH(C4H9)), 6.90−7.24 (m, 9H, Ar-H and C6H3(CH3)2), 7.66 (s, 1H, CHN); minor set of signals δ 0.88−1.83 (m, 18H, SbC4H9 and NCH(C4H9)), 2.06 (s, 6H, C6H3(CH3)2), 2.35 (s, 3H, C6H3(CH3)2), 2.70 (s, 3H, C6H3(CH3)2), 5.54 (t, 3JH−H = 4.8 Hz, 1H, NCH(C4H9)), 6.90−7.24 (m, 9H, Ar-H, and C6H3(CH3)2), 7.67 (s, 1H, CHN) ppm. 13C NMR (100.61 MHz, C6D6): signals for both isomers δ 13.8, 14.1, 14.6, 14.7, 19.2 (overlap of two signals), 20.4, 20.9, 21.6, and 22.1 (s, Bu-CH3 and C6H3(CH3)2), 23.8, 23.9, 26.7, 27.1, 27.3, 28.0, 28.2, 29.7, 30.5, 30.7, 39.3, and 43.0 (s, Bu-CH2), 71.6 and 75.1 (s, NCH(C4H9)), 123.0, 123.5, 125.1, 125.2, 128.4, 128.5, 128.8, 128.9 (overlap of two signals), 129.0, 129.5, 130.1, 130.3, 130.4, 136.0, 136.5, 137.5, 138.9, 139.4, 145.8, 146.7, 150.4, 150.5, 154.3, 155.6, 157.9 (s, Ar-C and C6H3(CH3)2), 165.2 and 165.3 (s, CHN) ppm, Ar-C1 not observed. Synthesis of 1,3-Ph2-2-(2′,6′-Me2C6H3)-7-(CHN-2′,6′-Me2C6H3)1H-2,1-benzazastibole (10). A 0.79 mL portion (1.4 mmol) of a 1.8 M solution of PhLi in dibutyl ether was added to 0.377 g (0.7 mmol)

General Procedures for Preparation of Compounds 5−10. A solution of RLi (R = Me, Ph, n-Bu) was added to a stirred suspension of 1−4 in toluene (20 mL) at 0 °C. The reaction mixture was warmed to room temperature, stirred for 1 day, and then evaporated in vacuo. The residue was extracted with hexane (10 mL). For the next steps of isolation see the procedures described for the particular compounds. Synthesis of 1,3-Me2-2-t-Bu-7-(CHN-t-Bu)-1H-2,1-benzazastibole (5). A 1.04 mL portion (1.7 mmol) of a 1.6 M solution of MeLi in diethyl ether was mixed with 0.362 g (0.8 mmol) of 1. The yellow hexane extract was evaporated in vacuo to give a yellow oil characterized as 5. Yield: 0.29 g (87%). 1H NMR (400 MHz, C6D6): δ 1.14 (s, 9H, C(CH3)3), 1.15 (s, 3H, SbCH3), 1.36 (s, 9H, C(CH3)3), 1.49 (d, 3JH−H = 6.4 Hz, 3H, CHNCH3), 4.71 (q, 3JH−H = 6.4 Hz, 1H, NCH(CH3)), 7.00−7.22 (m, 3H, C6H3), 8.03 (s, 1H, CHN) ppm. 13C NMR (100.61 MHz, C6D6): δ SbCH3 not observed, 30.6 (s, C(CH3)3), 33.0 (s, C(CH3)3), 33.6 (s, NCH(CH3)), 55.5 (s, C(CH3)3), 58.3 (s, C(CH3)3), 64.2 (s, NCH(CH3)), 127.0, 128.5, 128.6, 139.8, 143.3 (s, Ar-C), 156.3 (s, CHN), 161.4 (s, ArC1) ppm. Synthesis of 1,3-n-Bu2-2-t-Bu-7-(CHN-t-Bu)-1H-2,1-benzazastibole (6). A 0.73 mL portion (1.2 mmol) of a 1.6 M solution of n-BuLi in hexane was added to 0.253 g (0.6 mmol) of 1. The yellow hexane extract was evaporated in vacuo to give a yellow oil characterized as 6. Yield: 0.23 g (82%). 1H NMR (400 MHz, C6D6): δ 1.19 (s, 9H, C(CH3)3), 1.34 (s, 9H, C(CH3)3), 0.88−1.83 (m, 18H, SbC4H9 and NCH(C4H9)), 4.60 (t, 3JH−H = 6.1 Hz, 1H, NCH(C4H9)), 7.10 (dd, 3 JH−H = 6.0 and 2.3 Hz, 1H, Ar-H), 7.25 (m, 2H, Ar-H), 8.07 (s, 1H, CHN) ppm. 13C NMR (100.61 MHz, C6D6): δ 14.4 and 14.9 (s, Bu-CH3), 24.2, 25.7, 27.2, 29.5, 29.9, and 45.2 (s, Bu-CH2), 30.7 (s, C(CH3)3), 33.0 (s, C(CH3)3), 55.7 (s, C(CH3)3), 58.3 (s, C(CH3)3), 68.8 (NCH(C4H9)), 126.9, 128.2, 128.7, 140.3, 143.4 (s, Ar-C), 156.8 (s, CHN), 160.6 (s, Ar-C1) ppm. Synthesis of 1,3-Ph2-2-t-Bu-7-(CHN-t-Bu)-1H-2,1-benzazastibole (7). A 1.08 mL portion (1.9 mmol) of a 1.8 M solution of PhLi in dibutyl ether was added to 0.422 g (1.0 mmol) of 1. The yellow hexane extract was evaporated in vacuo to give a yellow oil characterized as 7. Yield: 0.39 g (78%). 1H NMR (400 MHz, C6D6): major set of signals δ 0.91 (s, 9H, C(CH3)3), 1.31 (s, 9H, C(CH3)3), 5.59 (s, 1H, NCH(C6H5)), 6.92−7.53 (m, 13H, Ar-H and Ph-H), 7.99 (s, 1H, CHN); minor set of signals δ 0.98 (s, 9H, C(CH3)3), 1.14 (s, 9H, C(CH3)3), 6.13 (s, 1H, NCH(C6H5)), 6.92−7.53 (m, 13H, ArH and Ph-H), 7.86 (s, 1H, CHN) ppm. With regard to the 13C NMR data, the signals of aliphatic carbon atoms are listed below, but it is not possible to list the corresponding signals of aromatic carbon atoms, because the assignment is rather questionable. As mentioned above, compound 7 could not be isolated as an analytically pure sample. In addition, the existence of sets of signals, both containing two types of phenyl groups and one pincer ligand, leads to a rather complicated 13C NMR spectrum in the aromatic region. Both of these circumstances make the unambiguous assignment of this spectrum only slightly achievable. 13C NMR (100.61 MHz, C6D6):13 29.9, 30.0, 32.7, and 33.3 (s, C(CH3)3), 55.6, 56.2, 57.9, and 58.0 (s, C(CH3)3), 72.2 and 72.4 (NCH(C6H5)) ppm. Synthesis of {[2-(CHN-t-Bu)-6-(CH(Me)N-t-Bu)C6H3]SbMe}+Cl− (5a). A dioxane solution of HCl (0.16 mL, 0.6 mmol, 4 M solution) was added to a slightly yellow solution of 5 (0.254 g, 0.6 mmol) in hexane (20 mL) at room temperature. A yellowish precipitate formed immediately, and the reaction mixture was stirred for 1 h at room temperature. The resulting yellow suspension was filtered, and the solid was dried in vacuo. Yield: 0.236 g (85%). Mp: 231 °C. Anal. Calcd for C18H30ClN2Sb (MW 431.66): C, 54.6; H, 7.6. Found: C, 54.8; H, 7.5. 1H NMR (400 MHz, C6D6): δ 1.45 (s, 9H, C(CH3)3), 1.50 (s, 9H, C(CH3)3), 1.67 (d, 3JH−H = 7.2 Hz, 3H, NCH(CH3)), 1.79 (s, 3H, SbCH3), 4.49 (q, 3JH−H = 7.2 Hz, 1H, NCH(CH3)), 7.20 (s, 1H, NH), 7.42 (d, 3JH−H = 7.6 Hz, 1H, C6H3), 7.61 (t, 3JH−H = 7.6 Hz, 1H, C6H3), 7.71 (d, 3JH−H = 7.6 Hz, 1H, C6H3), 8.72 (s, 1H, CHN) ppm. 13C NMR (100.61 MHz, C6D6): δ SbCH3 not observed, 30.7 (s, C(CH3)3), 33.1 (s, C(CH3)3), 33.7 (s, NCH(CH3)), 55.5 (s, C(CH3)3), 58.3 (s, C(CH3)3), 64.2 (s, NCH(CH3)), 127.0, 128.5, 128.6, 139.8, 143.3 (s, Ar-C), 156.3 (s, CHN), 161.3 (s, ArF

DOI: 10.1021/om5011879 Organometallics XXXX, XXX, XXX−XXX

Article

Organometallics of 2. The yellow hexane extract was concentrated to one-third of the original volume. The solution was stored at −30 °C, giving yellow single crystals of 10 (suitable for X-ray diffraction analysis). Yield: 0.28 g (64%). Mp: 172 °C. Anal. Calcd for C36H33N2Sb (MW 615.42): C, 70.3; H, 5.4. Found: C, 70.5; H, 5.5. 1H NMR (400 MHz, C6D6): major set of signals δ 1.72 (s, 6H, C6H3(CH3)2), 1.93 (s, 3H, C6H3(CH3)2), 2.31 (s, 3H, C6H3(CH3)2), 6.43 (s, 1H, NCH(C6H5)), 6.73−7.18 (m, 19H, Ar-H, Ph-H and C6H3(CH3)2), 7.57 (s, 1H, CHN); minor set of signals δ 1.45 (s, 3H, C6H3(CH3)2), 1.70 (s, 3H, C6H3(CH3)2), 2.40 (s, 3H, C6H3(CH3)2), 5.81 (s, 1H, NCH(C6H5)), 6.73−7.18 (m, 19H, Ar-H, Ph-H and C6H3(CH3)2), 7.55 (s, 1H, CHN) ppm. 13C NMR (100.61 MHz, C6D6): signals for both isomers δ 18.6, 18.7, 20.1, 20.2, 20.3, 21.3 (s, C6H3(CH3)2), 74.9 and 77.9 (s, NCH(C6H5)), 124.0, 124.9, 125.1 (overlap of two signals), 127.3, 127.5, 128.7, 128.8, 128.9, 129.0 (overlap of two signals), 129.1 129.6, 129.7, 129.9, 130.8, 131.1, 131.3, 131.4, 135.5, 135.6, 136.8, 137.3, 138.2, 139.2, 139.3, 141.0, 145.2, 145.7, 145.8, 147.2, 147.8, 147.9, 148.3, 149.7, 149.8, 150.2, 157.0, 157.4 (s, Ar-C), 164.1 and 164.4 (s, CHN) ppm, Ar-C1 not observed. Synthesis of [2,6-(CHN-t-Bu)2C6H3]BiMe2 (11). A 1.19 mL portion (1.9 mmol) of a 1.6 M solution of MeLi in diethyl ether was added to 0.495 g (0.9 mmol) of compound 3. The greenish hexane extract was evaporated in vacuo to give an oil characterized as 11. Yield: 0.27 g (58%). Anal. Calcd for C18H29BiN2 (MW 482.42): C, 44.8; H, 6.1. Found: C, 44.6; H, 6.2. 1H NMR (400 MHz, C6D6): δ 1.10 (s, 6H, Bi(CH3)2), 1.25 (s, 18H, C(CH3)3), 7.16 (t, 3JH−H = 7.6 Hz, 1H, Ar-H4), 7.67 (d, 3JH−H = 7.6 Hz, 2H, Ar-H3,5), 8.27 (s, 2H, CHN) ppm. 13C NMR (100.61 MHz, C6D6): δ 11.0 (s, Bi(CH3)2), 30.2 (s, C(CH3)3), 58.0 (s, C(CH3)3), 127.5 (s, Ar-C4), 132.7 (s, ArC3,5), 146.6 (s, Ar-C2,6), 159.3 (s, CHN) ppm, Ar-C1 not observed. Synthesis of [2,6-(CHN-t-Bu)2C6H3]BiPh2 (12). A 0.72 mL portion (1.3 mmol) of a 1.8 M solution of PhLi in dibutyl ether was added to 0.339 g (0.6 mmol) of 3. The greenish hexane extract was evaporated in vacuo to give an oil characterized as 12. Yield: 0.22 g (55%). Anal. Calcd for C28H33BiN2 (MW 606.56): C, 55.4; H, 5.5. Found: C, 55.6; H, 5.7. 1H NMR (400 MHz, CDCl3): δ 0.91 (s, 18H, C(CH3)3), 7.12 (t, 3JH−H = 7.2, 2H, Ph-H4), 7.21 (m, 4H, Ph-H3,5), 7.53 (t, 3JH−H = 7.4 Hz, 1H, Ar-H4), 7.74 (d, 3JH−H = 7.6 Hz, 4H, PhH2,6), 7.95 (d, 3JH−H = 7.4 Hz, 2H, Ar-H3,5), 8.25 (s, 2H, CHN) ppm. 13C NMR (100.61 MHz, CDCl3): δ 29.6 (s, C(CH3)3), 57.7 (s, C(CH3)3), 126.8, 128.3, 130.2, 132.8, 136.9, 145.8 (s, Ar-C), 160.6 (s, CHN) ppm, Ar-C1 and Ph-C1 not observed. Synthesis of [2,6-(CHN-2′,6′-Me2C6H3)2C6H3]BiMe2 (13). A 0.39 mL portion (0.6 mmol) of a 1.6 M solution of MeLi in diethyl ether was added to 0.191 g (0.3 mmol) of 4. The greenish hexane extract was concentrated to one-third of the original volume. The solution was stored at −30 °C to give yellow single crystals of 13 (suitable for X-ray diffraction analysis). Yield: 0.12 g (68%). Mp: 121 °C. Anal. Calcd for C26H29BiN2 (MW 578.50): C, 54.0; H, 5.1. Found: C, 54.2; H, 5.2. 1H NMR (400 MHz, C6D6): δ 1.01 (s, 6H, Bi(CH3)2), 2.20 (s, 12H, C6H3(CH3)2), 6.96 (m, 2H, Ar-H), 7.04 (m, 3H, Ar-H), 7.18 (m, 2H, Ar-H), 7.99 (d, 3JH−H = 7.6 Hz, 2H, Ar-H), 8.20 (s, 2H, CHN) ppm. 13C NMR (100.61 MHz, C6D6): δ 9.6 (s, Bi(CH3)2), 19.2 (s, C6H3(CH3)2), 124.8, 128.0, 128.3, 129.1, 134.1, 144.6, 151.3 (s, Ar-C), 166.9 (s, CHN) ppm, Ar-C1 not observed. X-ray Crystallography. Suitable single crystals of studied compounds were mounted on glass fibers with oil and measured on a KappaCCD four-circle diffractometer with CCD area detector by monochromated Mo Kα radiation (λ = 0.71073 Å) at 150(1) K. The numerical22 absorption corrections from crystal shapes were applied for all crystals. The correction of the absorption in the case of 13 was performed analytically using SADABS software.23 The structures were solved by direct methods (SIR92)24 and refined by a full-matrix leastsquares procedure based on F2 (SHELXL97).25 Hydrogen atoms were fixed into idealized positions (riding model) and assigned temperature factors Uiso(H) = 1.2[Ueq(pivot atom)] or 1.5[Ueq( methyl)] with C− H = 0.96, 0.98, and 0.93 Å for methyl, methine, and hydrogen atoms in the aromatic ring, respectively. There are disordered solvent molecules of hexane and chloroform in the structures of 1 and 3, respectively.

Attempts were made to model this disorder but were unsuccessful. PLATON/SQUEZZE26 software was used to correct the data for the presence of disordered solvent. In the case of 1, a potential solvent volume of 360 Å3 was found. A total of 134 electrons per unit cell worth of scattering was located in the void. The calculated stoichiometry of the solvent was calculated to be a half-molecule of hexane per unit cell, which results in 100 electrons per unit cell. In the case of 3, a potential solvent volume of 230 Å3 was found. A total of 146 electrons per unit cell worth of scattering was located in the void. The calculated stoichiometry of the solvent was calculated to be a halfmolecule of chloroform per unit cell, which results in 116 electrons per unit cell. Crystallographic data for structural analysis have been deposited with the Cambridge Crystallographic Data Centre, CCDC Nos. 1032173−1032179. Copies of this information may be obtained free of charge from The Director, CCDC, 12 Union Road, Cambridge CB2 1EY, U.K. (fax, +44-1223-336033; e-mail, [email protected]. uk; web, http://www.ccdc.cam.ac.uk).

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ASSOCIATED CONTENT

S Supporting Information *

Figures giving 1H and 13C NMR data of compounds 5−7, Table S1 giving experimental details for X-ray diffraction analysis, and CIF files giving all crystal data and structure refinement details, atomic coordinates, anisotropic displacement parameters, and geometric data for the studied compounds. This material is available free of charge via the Internet at http://pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Author

*L.D.: fax, +420 466037068; tel, +420 466037163; e-mail, libor. [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The authors thank the Grant Agency of the Czech Republic (P207/12/0223).

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REFERENCES

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DOI: 10.1021/om5011879 Organometallics XXXX, XXX, XXX−XXX