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Communication

Synthesis, Crystal Structure, and Some Transformations of 9,12-Dichloro-ortho-Carborane

by
Sergey A. Anufriev
1,
Sergey V. Timofeev
1,
Olga B. Zhidkova
1,
Kyrill Yu. Suponitsky
1,2 and
Igor B. Sivaev
1,2,*
1
A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 28 Vavilov Street, 119991 Moscow, Russia
2
Basic Department of Chemistry of Innovative Materials and Technologies, G.V. Plekhanov Russian University of Economics, 36 Stremyannyi Line, 117997 Moscow, Russia
*
Author to whom correspondence should be addressed.
Crystals 2022, 12(9), 1251; https://doi.org/10.3390/cryst12091251
Submission received: 1 August 2022 / Revised: 21 August 2022 / Accepted: 31 August 2022 / Published: 2 September 2022
(This article belongs to the Special Issue Advances of Carborane Compounds)
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Abstract

:
Reaction of ortho-carborane with anhydrous AlCl3 in chloroform results in a mixture of 9-chloro, 9,12-dichloro, and 8,9,12-trichloro derivatives with 9,12-dichloro-ortho-carborane being the main product. Molecular crystal structure of 9,12-dichloro-ortho-carborane was determined by the single crystal X-ray diffraction. The crystal structure of 9,12-Cl2-1,2-C2B10H10 appeared to be nearly isostructural to 9,12-dibromo-ortho-carborane: the crystal packing is built of layers in which molecules are connected via weak hydrogen and halogen bonds. A synthetic scheme for preparation of the hexachloro derivative of cobalt bis(dicarbollide) Cs[8,8′,9,9′,12,12′-Cl6-3,3′-Co(1,2-C2B9H8)2] from 9,12-dichloro-ortho-carborane has been proposed.

1. Introduction

Chlorination was the first described substitution reaction at boron atoms in carboranes C2B10H12. However, despite the fact that the synthesis of chloro derivatives of ortho-carborane was first described almost 60 years ago [1,2,3,4,5], so far only two of its chloro derivatives, namely, 1,2-C2B10H4-4,5,7,8,9,10,11,12-Cl8 [6,7] and 1,2-C2B10H2-3,4,5,6,7,8,9,10,11,12-Cl10 (the last one as a complex with DMSO) [8], have been characterized by single crystal X-ray diffraction. Moreover, to the best of our knowledge, the structures of only two chloro derivatives of C-substituted carboranes have been determined [9,10]. This contrasts sharply with both the well-developed chemistry of iodo derivatives of ortho-carborane [11,12,13,14,15,16,17,18,19,20,21,22] and the chemistry of chloro derivatives of their structural analogs carba-closo-dodecaborate [CB11H12]− [23,24,25] and closo-dodecaborate [B12H12]2− [26,27] anions, polychlorinated and perchlorinated derivatives of which are widely used as weakly coordinating anions [28,29,30,31,32,33,34].
One of the reasons for the poor study of chloro derivatives of ortho-carborane is the rather low selectivity of the chlorination reaction, which leads already at the first stage of substitution to the formation of hardly separable mixtures of 8- and 9-chloro derivatives, with the content of the minor 8-isomer varying depending on the reaction conditions from approx. 10 to 50% [35,36]. A further chlorination leads to the formation of complex mixtures of chloro derivatives of carborane with higher substitution degrees [37,38].
Recently, an efficient method for the synthesis of 9-chloro-ortho-carborane has been proposed and its complete characterization by multinuclear NMR spectroscopy has been carried out [39]. As for 9,12-dichloro-ortho-carborane, some of its NMR data have recently been reported, but the experimental procedure for its synthesis has not been described in detail [40].
In this contribution we describe the synthesis of 9,12-dichloro-ortho-carborane and its characterization by NMR spectroscopy and single crystal X-ray diffraction.

2. Results and Discussion

9,12-dichloro-ortho-carborane was prepared by heating of the parent ortho-carborane with anhydrous AlCl3 in chloroform or carbon tetrachloride similar to reported by Zakharkin et al. (Scheme 1) [2]. The separation of the reaction mixture using column chromatography on silica with chloroform as eluent gave 11% of 9-Cl-1,2-C2B10H11 (1), 53% of 9,12-Cl2-1,2-C2B10H10 (2), and 21% of 8,9,12-Cl3-1,2-C2B10H9 (3) as white solids.
The NMR spectral data of the monochloro derivative 1 (See SI) correspond to the literature data [39]. The 1H NMR spectrum of the dichloro derivative 9,12-Cl2-ortho-C2B10H10 (2) in CDCl3 contains signals of the CH groups at 3.50 ppm and the signals of BH groups in the region of 1.5–3.2 ppm. Note the downfield shift of the signal of the CH carborane groups compared to the parent ortho-carborane (3.56 ppm), which indicates a decrease in the electron-withdrawing effect of the carborane fragment. The 13C NMR spectrum contains signal of the carborane carbons at 43.6 ppm. The 11B NMR spectrum contains one singlet at 6.7 ppm and three doublets at −8.3, −15.3, and −18.3 ppm with the integral intensity ratio of 2:2:4:2. All these data are close to reported in the literature [40].
The 11B NMR spectrum of the trichloro derivative 3 consists of two singlets at 6.0 and 0.2 ppm and five doublets at −9.9, −15.1, −17.2, −18.6, and −18.3 ppm with the integral intensity ratio of 2:1:2:2:1:1. The position of the substitution in compound 3 is unambiguously confirmed by its 11B-11B DQCOSY spectrum (Figure 1), which shows strong cross-peaks of the signals of substituted boron atoms. The 1H NMR spectrum of the trichloro derivative 8,9,12-Cl3-ortho-C2B10H9 (3) contains signals of the CH groups at 3.54 ppm and the signals of BH groups in the region of 1.5–3.3 ppm. It should be noted that a slight decrease in the electron-withdrawing effect of the carborane cage, observed when chlorine atoms are introduced into positions 9 and 12, is almost completely compensated by the introduction of one more chlorine atom into position 8. The 13C NMR spectrum contains signal of the carborane carbons at 41.0 ppm.
Recently, interest has increased in studying the role of weak non-covalent interactions, including dihalogen and hydrogen bonds, in the stabilization of the crystal packing of halogen derivatives of carboranes. Such types of bonding were found earlier in the crystal structures of some iodo [41,42] and bromo [43,44] derivatives of ortho-carborane. In general, dihalogen bonds (X…X contacts of type II) are known to be most favored in iodo derivatives, less in bromo derivatives, and the least in chloro derivatives [45]. Nevertheless, the intermolecular Cl…Cl dihalogen bonds have been found in the solid-state structures of 4,5,7,8,9,10,11,12-Cl8-1,2-C2B10H4 [6,7] and 3,4,5,6,7,8,9,10,11,12-Cl10-1,2-C2B10H2·DMSO [8,46], as well as in the structure of perchloro 1,7-diphosphaborane 1,7-P2B10Cl10·toluene [47]. In this case, only a part of the chlorine atoms participates in the formation of the dihalogen bonds. Therefore, it was interesting to study the crystal structure of 9,12-Cl2-1,2-C2B10H10 from the point of view of the possibility of the formation of Cl…Cl dihalogen bonds.
Crystal structure of 9,12-dichloro-ortho-carborane was determined by the single crystal X-ray diffraction. General view of the molecule is presented in Figure 2. The B-Cl bond lengths are 1.798(2) Å. The crystal structure of 9,12-Cl2-1,2-C2B10H10 appeared to be nearly isostructural to recently studied 9,12-dibromo-ortho-carborane [44].
Crystal packing can be described as built up of layers in which molecules are connected via weak halogen bond and weak hydrogen bonds (Figure 3) as it was observed for the dibromo derivative 9,12-Br2-1,2-C2B10H10. Since the chlorine atom is both weaker donor and acceptor of the lone pair in comparison to the bromine, the strength of Cl…Cl and Cl…H contacts might appear to be somewhat weaker. In fact, the shortest H…Br nonbonded contacts (2.82 Å) in 9,12-Br2-1,2-C2B10H10 are somewhat longer than sum of van-der-Waals radii (2.72 Å) [48], while in 9,12-Cl2-1,2-C2B10H10 similar contacts (H2…Cl1, 2.61(2) Å) are somewhat shorter than sum of van-der-Waals radii (2.67 Å). At the same time, the Br…Br interactions (the Br…Br distance is 3.796 Å, sum of van-der-Waals radii is 3.79, B-Br…Br angle is 148.4°) in the dibromo derivative 9,12-Br2-1,2-C2B10H10 seems to be somewhat stronger in comparison to 9,12-Cl2-1,2-C2B10H10: the Cl…Cl distance is 3.751(2) Å (sum of van-der-Waals radii is 3.65 Å) and the B-Cl…Cl angle is 145.8(2)°. Those differences, however, are rather small and the behavior of the chlorine and bromine atoms in the dihalogen derivatives can be considered to be quite similar.
In the crystal of the 8,9,12-trichloro derivative 3 (Figure 4), the Cl8 atom is disordered over two cites: at B8 and B10 atoms in the ratio of 84:16. In fact, two disordered molecules are the same and are related by the mirror plane.
For the crystal packing description, we used major part of the disordered molecule. As in the 9,12-dihloro derivative 2, no any strong Cl…Cl halogen bonds of type II are observed in the crystal of compound 3. Each Cl atom forms two Cl…Cl dihalogen bonds being both lone pair donor and acceptor (Table 1) which leads to a formation of halogen-bonded layers (Figure 5). Each Cl atom participates in three Cl…H contacts however their distances are in the range of 2.87–3.29 Å which are longer than sum of van-der-Waals radii.
The use of the hexachloro derivative of cobalt bis(dicarbollide) Cs[8,8′,9,9′,12,12′-Cl6-3,3′-Co(1,2-C2B9H8)2] in the extraction processing of nuclear waste has previously been described [49,50]. The hexachloro derivative of cobalt bis(dicarbollide) can be obtained by direct chlorination of cobalt bis(dicarbollide) with chlorine [51] or sulfuryl chloride [52]; however, both these methods, along with the hexachloro derivative, lead to the formation of derivatives with higher degrees of substitution, which makes it difficult to purify the target product. This prompted us to develop a scheme for the synthesis of the hexachloro derivative of cobalt bis(dicarbollide) based on the dichloro derivative of ortho-carborane 2 (Scheme 2).
Deboronation of carborane 2 with KOH in refluxing aqueous ethanol followed by the treatment with Me3NHCl in water gave the corresponding nido-carborane (Me3NH)[5,6-Cl2-7,8-C2B9H10] (4) in 93% yield. The 11B NMR spectrum of nido-carborane 4 in acetone-d6 contains singlet at −4.0 ppm and five doublets at −11.5, −20.2, −22.3, −29.1, and −35.5 ppm with the integral intensity ratio of 2:2:1:2:1:1, which agrees well with the geometry of the symmetrically substituted nido-carborane. The 1H NMR spectrum contains signals of the CH groups at 1.70 ppm, the terminal BH groups in the region of 0.0–2.8 ppm, and the bridging BHB hydrogen at −2.14 ppm. The 13C NMR spectrum contains signal of the nido-carborane carbons at 36.8 ppm.
Reaction of 4 with cobalt bromide in 40% aqueous solution of potassium hydroxide resulted in the corresponding cobaltacarborane K[9,9′,12,12′-Cl4-3,3′-Co(1,2-C2B9H9)2] (5) isolated in 63% yield. The NMR spectral data of the tetrachloro derivative of cobalt bis(dicarbollide) correspond to the literature data [51]. The structure of the cobalt complex was supported by single crystal X-ray diffraction study of Cs[9,9′,12,12′-Cl4-3,3′-Co(1,2-C2B9H9)2]·2Me2CO (5′). An asymmetric unit cell contains one cobaltacarborane anion, two halves of the Cs cation located at two-fold symmetry axis and two acetone molecules. The structure of the anion is shown in Figure 6. The dicarbollide ligands are rotated by 37.0(4)° to each ither so that the projection of the C1′ atom onto the C1-C2-B4-B7-B8 open face appears over the center of the C2-B7 bond. A similar cisoid orientation of the dicarbollide ligands was previously found in the case of the tetrathiafulvalene salt of the 9,9′,12,12′-tetraiodo derivative of cobalt bis(dicarbollide) (TTF)[9,9′,12,12′-I4-3,3′-Co(1,2-C2B9H9)2] [53]. The intermolecular bonding in the crystal of 5′ is mostly dictated by the bonding preferences of the Cs atoms. Each Cs atom binds four chlorine and four oxygen atoms (see Figure S1 in SI), while the Cl…Cl and H…Cl as well as Cl…O are secondary interactions.
Previously, it was shown that the chlorine atoms at positions 8 and 8′ of the parent cobalt bis(dicarbollide) can be introduced using sodium hypochlorite [54]. Therefore, we decided to use a similar approach to selectively introduce two chlorine atoms into the tetrachloro derivative of cobalt bis(dicarbollide). The reaction of 5 with t-BuOCl in acetonitrile followed by precipitation with CsCl from aqueous solution gave the desired hexachloro derivative Cs[8,8′,9,9′,12,12′-Cl6-3,3′-Co(1,2-C2B9H8)2] (6) in 80% yield. The 11B NMR spectrum of 6 in acetone-d6 contains two singlets at 6.3 and 3.2 ppm and four doublets at 1.5, −6.4, −17.8, and −24.4 ppm with the integral intensity ratio of 2:4:2:4:4:2. The 1H NMR spectrum contains signals of the CH groups of cobaltacarborane at 4.39 ppm and the BH groups in the region of 1.0–3.9 ppm. A significant downfield shift of the signal of the CH groups of the dicarbollide ligands in the 1H NMR spectrum of complex 6 as compared to complex 5 suggests the presence of the intramolecular CH…Cl hydrogen bonds between the dicarbollide ligands with the formation of a transoid conformation, which is typical for the 8,8′-dihalogen derivatives of cobalt bis(dicarbollide) [55].

3. Materials and Methods

3.1. General Methods

tert-Butylhypochlorite tBuOCl was synthesized according literature method [56]. All other chemical reagent were purchased from Sigma Aldrich, Acros Organics, ABCR, and other commercial vendors and used without purification. The reaction progress was monitored by thin layer chromatography (Merck F254 silica gel on aluminum plates) and visualized using 0.5% PdCl2 in 1% HCl in aq. MeOH (1:10). The NMR spectra at 400 MHz (1H), 128 MHz (11B), and 100 MHz (13C) were recorded with Varian Inova 400 spectrometer. The residual signal of the NMR solvent relative to Me4Si was taken as the internal reference for 1H and 13C NMR spectra. 11B NMR spectra were referenced using BF3·Et2O as external standard. Mass spectra (MS) were measured using Shimadzu LCMS-2020 instrument with DUIS ionization (ESI—Electrospray ionization and APCI—Atmospheric pressure chemical ionization). The measurements were performed in a negative ion mode with mass range from m/z 50 to m/z 2000. Isotope distribution was calculated using Isotope Distribution Calculator and Mass Spec Plotter [57].

3.2. Synthetic Procedure of ortho-Carborane Chlorination and Characterization of Mono-, Di- and Trisubstituted Chloro Derivatives of ortho-Carborane

Anhydrous AlCl3 (2.00 g, 15.0 mmol) was added to a solution of ortho-carborane (5.0 g, 34.7 mmol) in CHCl3 or CCl4 (50 mL) stirred at room temperature. The resulting mixture was heated under reflux for 4 h. Since the reaction is highly exothermic and the carborane reacts very violently at first, a 250 mL round bottom flask should be used with vigorous stirring. Then, the reaction mixture was cooled to ambient temperature and treated with a solution of 5% HCl in water (50 mL). The organic phase was separated; the aqueous fraction was extracted with CHCl3 or CCl4 (3 × 50 mL). The organic phases were combined, dried over Na2SO4, filtered and concentrated under reduced pressure. The crude product was purified twice by column chromatography on silica using CHCl3 as eluent to give 0.70 g (11%) of 9-Cl-ortho-C2B10H11 (1), 6.01 g (53%) of 9,12-Cl2-ortho-C2B10H10 (2), and 1.82 g (21%) of 8,9,12-Cl3-ortho-C2B10H9 (3) as white powders.
9-Cl-ortho-C2B10H11 (1): 1H NMR (CDCl3, ppm): δ 3.56 (1H, br s, CHcarb), 3.44 (1H, br s, CHcarb), 3.2–1.4 (9H, br m, BH). 11B NMR (CDCl3, ppm): δ 7.4 (1B, s, B(9)), −2.1 (1B, d, J = 154 Hz, B(12)), −8.8 (2B, d, J = 153 Hz, B(8,10)), −13.8 (2B, d, J = 175 Hz, B(4,5)), −15.2 (2B, d, J = 158 Hz, B(7,11)), −16.4 (2B, d, J = 169 Hz, B(3,6)). 13C NMR (CDCl3, ppm): δ 52.2 (CHcarb), 44.5 (CHcarb). MS (DUIS), m/z: found: 178 (M–H)−; calculated for C2H10B10Cl (M–H)− 178.0.
9,12-Cl2-ortho-C2B10H10 (2): 1H NMR (CDCl3, ppm): δ 3.50 (2H, br s, CHcarb), 3.2–1.5 (8H, br m, BH). 11B NMR (CDCl3, ppm): δ 6.7 (2B, s, B(9,12)), −8.3 (2B, d, J = 156 Hz, B(8,10)), −15.3 (4B, d, J = 169 Hz, B(4,5,7,11)), −18.3 (2B, d, J = 182 Hz, B(3,6)). 13C NMR (CDCl3, ppm): δ 43.6 (CHcarb). MS (DUIS), m/z: found: 212 (M–H)−; calculated for C2H9B10Cl2 (M–H)− 212.
8,9,12-Cl3-ortho-C2B10H9 (3): 1H NMR (CDCl3, ppm): δ 3.54 (2H, br s, CHcarb), 3.3–1.5 (7H, br m, BH). 11B NMR (CDCl3, ppm): δ 6.0 (2B, s, B(9,12)), 0.2 (1B, s, B(8)), −9.9 (1B, d, J = 159 Hz, B(10)), −15.1 (2B, d, J = 175 Hz, B(4,7)), −17.2 (2B, d, J = 175 Hz, B(5,11)), −18.6 (1B, d, J = 187 Hz, B(3)), −22.9 (1B, d, J = 182 Hz, B(6)). 13C NMR (CDCl3, ppm): δ 41.0 (CHcarb). MS (DUIS), m/z: found: 246 (M–H)−; calculated for C2H8B10Cl3 (M–H)− 246.

3.3. Synthesis of 9-Chloro-ortho-Carborane (1)

N-Chlorosuccinimide (1.00 g, 7.5 mmol) was added to a solution of ortho-carborane (1.00 g, 6.9 mmol) in glacial acetic acid (20 mL). The resulting mixture was heated under reflux for 24 h. Then, the reaction mixture was cooled and treated with water (60 mL). The white precipitate was filtered, washed with water and dried on air. Fraction crystallization from hexane gave 0.60 g (49% yield) of 9-Cl-ortho-C2B10H11 (1) as colorless crystals.

3.4. Synthesis of Trimethylammonium Salt of 5,6-Dichloro-nido–Carborane (4)

Potassium hydroxide (7.84 g, 140.0 mmol) was added to a solution of 2 (7.49 g, 35.2 mmol) in 70% EtOH in water (500 mL). The resulting mixture was heated under reflux for 6 h. Then, the reaction mixture was cooled and concentrated under reduced pressure. The crude product was dissolved in a water (500 mL) and a solution of NH4Cl (11.23 g, 210.0 mmol) in water (150 mL) was added. The resulting mixture was added to a solution of Me3NHCl (7.00 g, 73.24 mmol) in water (50 mL). The white precipitate was filtered, washed with water and dried on air to give 8.58 g (93%) of (Me3NH)[5,6-Cl2-nido-7,8-C2B9H10] (4) as white powder.
(Me3NH)[5,6-Cl2-nido-7,8-C2B9H10]: 1H NMR (CD3COCD3, ppm): δ 3.19 (9H, s, (CH3)3NH), 1.70 (2H, br s, CHcarb), 2.8–0.0 (7H, br m, BH), −2.14 (1H, br m, BHB). 11B NMR (CD3COCD3, ppm): δ −4.0 (2B, s, B(5,6)), −11.5 (2B, d, J = 140 Hz, B(9,11)), −20.2 (1B, d, J = 165 Hz, B(3)), −22.3 (2B, d, J = 151 Hz, B(2,4)), −29.1 (1B, dd, J1 = 128 Hz, J2 = 37 Hz, B(10)), −35.5 (1B, d, J = 145 Hz, B(1)). 13C NMR (CD3COCD3, ppm): δ 46.1 ((CH3)3NH), 36.8 (CHcarb). MS (DUIS), m/z: found: 202 (M)−; calculated for C2H10B9Cl2 (M)− 202.

3.5. Synthesis of Potassium Salt of 9,9′,12,12′-Tetrachloro Cobalt bis(Dicarbollide) (5)

Compound 4 (8.58 g, 32.7 mmol) was added to a fresh hot 40% KOH solution in water (160 mL). The resulting mixture was stirred for 30 min. Then, CoBr2·6H2O (16.03 g, 49.2 mmol) was added and the reaction mixture was stirred at 60 °C for a week. After, the suspension was cooled, the orange precipitate was filtered, washed with 40% KOH solution in water (40% KOH washings can be used as solution for the same consecutive synthesis) and dried on air. The resulting orange solid was dissolved in acetonitrile, filtered and concentrated under reduced pressure to give 5.40 g (65%) of K[9,9′,12,12′-Cl4-closo-3,1,2-Co(1,2-C2B9H9)2] (5) as orange powder.
K[9,9′,12,12′-Cl4-closo-3,1,2-Co(1,2-C2B9H9)2] (5): 1H NMR (CD3COCD3, ppm): δ 4.05 (4H, br s, CHcarb), 4.4–0.7 (14H, br m, BH). 11B NMR (CD3COCD3, ppm): δ 6.3 (2B, d, J = 144 Hz, B(8,8′)), 4.4 (4B, s, B(9,9′,12,12′)), 1.9 (2B, d, J = 158 Hz, B(6,6′)), −7.6 (4B, d, J = 155 Hz, B(4,4′,7,7′)), −17.8 (4B, d, J = 164 Hz, B(5,5′11,11′)), −24.4 (2B, d, J = 158 Hz, B(10,10′)). 13C NMR (CD3COCD3, ppm): δ 43.7 (CHcarb). MS (DUIS), m/z: found: 461 (M)−; calculated for C4H18B18Cl4Co (M)− 461.

3.6. Synthesis of Cesium Salt of 8,8′,9,9′,12,12′-Hexachloro Cobalt bis(Dicarbollide) (6)

tBuOCl (14 mL, 13.42 g, 123.57 mmol) was added to a solution of 5 (5.40 g, 10.7 mmol) in acetonitrile (150 mL). The resulting mixture was stirred for 24 h and, then, concentrated under reduced pressure. The crude product was dissolved in water (200 mL), the resulting mixture was added to a solution of CsCl (6.00 g, 35.64 mmol) in water (10 mL). The orange precipitate was filtered, washed with water and dried on air to give 5.68 g (80%) of Cs[8,8′,9,9′,12,12′-Cl6-closo-3,1,2-Co(1,2-C2B9H8)2] (6) as orange powder.
Cs[8,8′,9,9′,12,12′-Cl6-closo-3,1,2-Co(1,2-C2B9H8)2] (6): 1H NMR (CD3COCD3, ppm): δ 4.39 (4H, br s, CHcarb),3.9–1.0 (12H, br m, BH). 11B NMR (CD3COCD3, ppm): δ 6.3 (2B, s, B(8,8′)), 3.2 (4B, s, B(9,9′,12,12′)), 1.5 (2B, d, J = 160 Hz, B(6,6′)), −6.4 (4B, d, J = 157 Hz, B(4,4′,7,7′)), −17.8 (4B, d, J = 165 Hz, B(5,5′11,11′)), −24.4 (2B, d, J = 185 Hz, B(10,10′)). 13C NMR (CD3COCD3, ppm): δ 50.5 (CHcarb). MS (DUIS), m/z: found: 530 (M)−; calculated for C4H18B16Cl6Co (M)− 530.

3.7. Single Crystal X-ray Diffraction Study

The single crystals of 9,12-Cl2-ortho-C2B10H10 and 8,9,12-Cl3-ortho-C2B10H9 were grown by slow evaporation of solutions of the title compounds in chloroform at room temperature, while the tiny orange prisms of Cs[9,9′,12,12′-Cl4-3,3′-Co(1,2-C2B9H9)2]·2Me2CO were obtained by slow evaporation of a solution of the complex in acetone. Single crystal X-ray diffraction experiments were carried out using SMART APEX2 CCD diffractometer (λ(Mo-Kα) = 0.71073 Å, graphite monochromator, ω-scans) at 120 K. Collected data were processed by the SAINT and SADABS programs incorporated into the APEX2 program package [58]. The structures were solved by the direct methods and refined by the full-matrix least-squares procedure against F2 in anisotropic approximation. The refinement was carried out with the SHELXTL program [59]. The CCDC numbers (2190099 for 2, 2202671 for 3, 2202672 for 5′) contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif (accessed on 17 May 2022).

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/cryst12091251/s1, Crystallographic data for compounds 2, 3, and 5′, NMR and MS spectra of compounds 1–6.

Author Contributions

Synthesis and NMR spectroscopy studies, S.A.A.; synthesis, S.V.T.; synthesis, O.B.Z.; single crystal X-ray diffraction experiments, K.Y.S.; supervision and manuscript concept, I.B.S. All authors have read and agreed to the published version of the manuscript.

Funding

This research was supported by the Russian Science Foundation (Grant No. 21-13-00345).

Data Availability Statement

In this section, please provide details regarding where data supporting reported results can be found, including links to publicly archived datasets analyzed or generated during the study. Crystallographic data for the structure of 9,12-Cl2-ortho-C2B10H10 (2), 8,9,12-Cl3-ortho-C2B10H9 (3), and Cs [9,9′,12,12′-Cl4-3,3′-Co(1,2-C2B9H9)2]·2Me2CO (5′) were deposited with the Cambridge Crystallographic Data Centre as supplementary publications CCDC 2190099 (for 2), 2202671 (for 3), and 2202672 (for 5′). The Supplementary Information contains crystallographic data for compounds 2, 3, and 5′, and NMR and MS spectra of compounds 1–6.

Acknowledgments

The single crystal X-ray diffraction and NMR spectral data were obtained by using equipment from the Center for Molecular Structure Studies at A.N. Nesmeyanov Institute of Organoelement Compounds, operating with financial support from the Ministry of Science and Higher Education of the Russian Federation.

Conflicts of Interest

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

References

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Crystals 12 01251 sch001 550
Scheme 1. Synthesis of 9,12-Cl2-ortho-C2B10H10.
Scheme 1. Synthesis of 9,12-Cl2-ortho-C2B10H10.
Crystals 12 01251 sch001
Crystals 12 01251 g001 550
Figure 1. 11B-11B DQCOSY NMR spectrum of 8,9,12-Cl3-1,2-C2B10H9 in CDCl3.
Figure 1. 11B-11B DQCOSY NMR spectrum of 8,9,12-Cl3-1,2-C2B10H9 in CDCl3.
Crystals 12 01251 g001
Crystals 12 01251 g002 550
Figure 2. General view of 9,12-Cl2-1,2-C2B10H10 showing atomic numbering. Thermal ellipsoids are drawn at 50% probability level. The B9-Cl1 and B12-Cl2 distances are equal to each other (1.798(2) Å).
Figure 2. General view of 9,12-Cl2-1,2-C2B10H10 showing atomic numbering. Thermal ellipsoids are drawn at 50% probability level. The B9-Cl1 and B12-Cl2 distances are equal to each other (1.798(2) Å).
Crystals 12 01251 g002
Crystals 12 01251 g003 550
Figure 3. Crystal packing fragment of 9,12-Cl2-1,2-C2B10H10. Trimeric associate formed via Cl…Cl dihalogen and H…Cl hydrogen bonds. Projection onto bc plane.
Figure 3. Crystal packing fragment of 9,12-Cl2-1,2-C2B10H10. Trimeric associate formed via Cl…Cl dihalogen and H…Cl hydrogen bonds. Projection onto bc plane.
Crystals 12 01251 g003
Crystals 12 01251 g004 550
Figure 4. General view of 8,9,12-Cl2-1,2-C2B10H9 showing atomic numbering. Thermal ellipsoids are drawn at 50% probability level. Only major part of the disorder is shown. The B8-Cl8, B9-Cl1 and B12-Cl2 distances are equal to 1.774(5), 1.794(4) and 1.793(4) Å, respectively.
Figure 4. General view of 8,9,12-Cl2-1,2-C2B10H9 showing atomic numbering. Thermal ellipsoids are drawn at 50% probability level. Only major part of the disorder is shown. The B8-Cl8, B9-Cl1 and B12-Cl2 distances are equal to 1.774(5), 1.794(4) and 1.793(4) Å, respectively.
Crystals 12 01251 g004
Crystals 12 01251 g005 550
Figure 5. Crystal packing fragment of 8,9,12-Cl3-1,2-C2B10H9. Layers parallel the ac plane are formed by weak Cl…Cl dihalogen bonds.
Figure 5. Crystal packing fragment of 8,9,12-Cl3-1,2-C2B10H9. Layers parallel the ac plane are formed by weak Cl…Cl dihalogen bonds.
Crystals 12 01251 g005
Crystals 12 01251 sch002 550
Scheme 2. Synthesis of Cs[8,8′,9,9′,12,12′-Cl6-3,3′-Co(1,2-C2B9H8)2].
Scheme 2. Synthesis of Cs[8,8′,9,9′,12,12′-Cl6-3,3′-Co(1,2-C2B9H8)2].
Crystals 12 01251 sch002
Crystals 12 01251 g006 550
Figure 6. General view of the [9,9′,12,12′-Cl4-3,3′-Co(1,2-C2B9H9)2]−·anion showing atomic numbering. Thermal ellipsoids are drawn at 50% probability level. The B9-Cl1, B12-Cl2, B9-Cl1 and B12′-Cl2′ distances are equal to 1.812(6), 1.806(6), 1.806(5) and 1.815(6), respectively.
Figure 6. General view of the [9,9′,12,12′-Cl4-3,3′-Co(1,2-C2B9H9)2]−·anion showing atomic numbering. Thermal ellipsoids are drawn at 50% probability level. The B9-Cl1, B12-Cl2, B9-Cl1 and B12′-Cl2′ distances are equal to 1.812(6), 1.806(6), 1.806(5) and 1.815(6), respectively.
Crystals 12 01251 g006
Table
Table 1. Cl…Cl dihalogen bond parameters in the crystal structure of compound 3 (distances in Å, angles in deg.).
Table 1. Cl…Cl dihalogen bond parameters in the crystal structure of compound 3 (distances in Å, angles in deg.).
B-Cl…Cl-B ContactCl…ClB-Cl…ClCl…Cl-B
B9-Cl9…Cl12-B123.704(3)105.4(3)133.8(3)
B9-Cl9…Cl8-B83.870(3)139.4(3)92.3(3)
B12-Cl12…Cl8-B83.870(3)91.0(3)149.3(3)
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Anufriev, S.A.; Timofeev, S.V.; Zhidkova, O.B.; Suponitsky, K.Y.; Sivaev, I.B. Synthesis, Crystal Structure, and Some Transformations of 9,12-Dichloro-ortho-Carborane. Crystals 2022, 12, 1251. https://doi.org/10.3390/cryst12091251

AMA Style

Anufriev SA, Timofeev SV, Zhidkova OB, Suponitsky KY, Sivaev IB. Synthesis, Crystal Structure, and Some Transformations of 9,12-Dichloro-ortho-Carborane. Crystals. 2022; 12(9):1251. https://doi.org/10.3390/cryst12091251

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Anufriev, Sergey A., Sergey V. Timofeev, Olga B. Zhidkova, Kyrill Yu. Suponitsky, and Igor B. Sivaev. 2022. "Synthesis, Crystal Structure, and Some Transformations of 9,12-Dichloro-ortho-Carborane" Crystals 12, no. 9: 1251. https://doi.org/10.3390/cryst12091251

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