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Article

Intramolecularly Stabilized o-Carboranyl Aluminum Complexes: Synthesis, Characterization, and X-ray Structural Studies

by
Honglae Sohn
and
Jong-Dae Lee
*
Department of Chemistry, College of Natural Sciences, Chosun University, Gwangju 61452, Republic of Korea
*
Author to whom correspondence should be addressed.
Crystals 2023, 13(6), 877; https://doi.org/10.3390/cryst13060877
Submission received: 24 April 2023 / Revised: 24 May 2023 / Accepted: 25 May 2023 / Published: 27 May 2023
(This article belongs to the Section Inorganic Crystalline Materials)
Browse Figures
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Abstract

:
The chelating aluminum complex [2-(Me2NCH2)C2B10H10]AlX2 (X = Br 3, CH3 4) was synthesized using 2-dimethylaminomethyl-o-carboranyl lithium (LiCabN, 2) with aluminum tribromide (AlBr3) or dimethylaluminum bromide (Me2AlBr), resulting in a modest yield. Compound 4 was obtained by reacting compound 3 with methyllithium (CH3Li) in toluene. All compounds were characterized using infrared (IR) spectroscopy; 1H, 11B, 13C nuclear magnetic resonance (NMR) spectroscopy; and X-ray crystallography. X-ray structural studies of CabNAlBr2 (3) and CabNAlMe2 (4) (CabN = 2-dimethylaminomethyl-o-carboranyl) indicated that the aluminum atom was located at the center of a distorted tetrahedron. Crystal structures of CabNAlBr2 (3) [a = 8.9360(3) Å, b = 12.0358(9) Å, c = 14.7730(4) Å, α = β = γ = 90°] and CabNAlMe2 (4) [a = 8.9551(3) Å, b = 11.9126(9) Å, c = 14.7711(4) Å, α = β = γ = 90°] were obtained. The reactivity of aluminum complexes 3 and 4 with Lewis bases, such as H2O, pyridine, alkylamines, and arylamines, confirmed their rapid decomposition due to the strong Lewis acidity of aluminum metals.

1. Introduction

Organometallic compounds with unique properties and specific reactivities can be prepared by utilizing the properties of C,N-chelating ligands [1]. These properties derive from the extension of their coordination number via the intramolecular coordination of a C,N-chelating ligand. Various organoaluminum compounds with C,N-chelating ligands have been prepared for the purpose of bonding to aluminum atoms via Al–C covalent bonds and Al–N dative bonds [2,3,4,5,6,7,8,9,10,11,12]. Recently, interest in aluminum nitride (AlN) [13], a form in which aluminum and nitrogen are combined, has been on the rise due to AlN being one of the few materials with both a wide direct bandgap and large thermal conductivity [14,15,16,17,18,19,20]. Group 13 metal nitrides are commonly used in optoelectronics [21,22,23,24,25,26], as well as in high-power and high-frequency electronics [27,28,29,30,31], owing to their small atomic mass, strong interatomic bonds, and simple crystal structure [32]. In particular, from among group 13 metal nitrides, AlN has the highest thermal conductivity and demonstrates the most effective dissipation of heat from a wide variety of power and radio frequency electronics [27,28,29,30,31].
o-Carborane is a cluster compound of great interest owing to its ease of preparation and derivatization, thermal stability, and steric bulkiness [33]. Therefore, it was necessary to investigate the possibility of synthesizing intramolecular coordination complexes in a 2-dimethylaminomethyl-o-carboranyl (HCabN, 1) system. For these reasons, it is interesting to investigate the possibility of synthesizing such intramolecularly N-coordinated aluminum metal complexes using the potentially bidentate ligand system [34,35].
This study reports on the synthesis, characterization, and X-ray structural study of organoaluminum complexes of the type (CabN)AlX2 (X = Br, CH3), in which the aluminum metal center can be regarded as tetracoordinated because of intramolecular Al–N coordination. We have previously reported on the successful synthesis and structural characterization of tetracoordinated gallium complexes containing an N- or P-donor [34,36]. We observe from these results that N-donor, far more so than P-donor, ligand systems have a reduced probability of forming the desired intramolecular stabilization as the size of the incoming metal increases, that is, unless specific electronic factors intervene. In this respect, we have started to investigate the synthesis of intramolecularly stabilized aluminum metal complexes that bear a steric bulky o-carboranyl ligand system [33].
Thus, we report, in this paper, the detailed synthetic procedures of (o-carboranylamino) aluminum compounds and their complete characterization using IR, NMR spectroscopy, and X-ray diffraction. The preparation of this type of compound starts from the reaction of metal halides with (2-dimethylaminomethyl-o-carboranyl)lithium (2). Herein, we reported the appropriate synthetic procedures and spectroscopic characteristics of novel intramolecularly coordinated aluminum complexes and the reactivities of these compounds toward a Lewis base.

2. Materials and Methods

2.1. General Procedures

All manipulations were performed under a dry, oxygen-free nitrogen or argon atmosphere using standard Schlenk techniques Alternatively, they were conducted in vacuum conditions in a KK-011AS glove box. Ether and toluene were dried and distilled from sodium benzophenone. Hexane was dried and distilled over CaH2. 1H, 11B, and 13C NMR spectra were recorded on a JEOL 300 MHz NMR spectrometer as operating at 300.1, 96.3, and 75.4 MHz, respectively. All the boron-11 chemical shifts were referenced to BF3∙O(C2H5)2 (0.0 ppm), with a negative sign indicating an upfield shift. All proton and carbon chemical shifts were measured in relation to the internal residual benzene in the lock solvent (99.5% C6D6) and then referenced to tetramethylsilane (0.00 ppm). IR spectra were recorded using a Bio-Rad FTS-165 spectrophotometer. Elemental analyses were performed using a Carlo Erba Instruments CHNS-O EA1108 analyzer. All melting points were uncorrected. Decaborane and (dimethylamino)-2-propyne were purchased from Katchem and Aldrich, respectively, and used without purification. CabN (1; HCabN, 2-[(dimethylamino)methyl]-o-carborane) [37] was prepared according to the specifications of a previously reported method. The starting material AlBr3 was purchased from Strem Chemical and sublimed under dynamic vacuum conditions prior to each use. Dimethylaluminum bromide [38] was prepared by conducing stoichiometric ligand redistribution reactions in pentane at room temperature, after which it was purified by vacuum sublimation at room temperature.

2.2. X-ray Crystallography

Details of the crystal data and a summary of the intensity data collection parameters for 3 and 4 are provided in Table 1. Crystals of 3 and 4 were grown in a toluene solution and stored at −20 °C. They were then mounted in thin-walled glass capillaries, sealed under an argon atmosphere, and transferred to the goniometer of the Bruker SMART 1000 CCD area detector system. The initial unit cell parameters were obtained using the SMART [39] software. Data integration, correction for Lorentz and polarization effects, and final cell refinement were performed using SAINTPLUS [40]. The data were further corrected for absorption using SADABS [41]. The initial structure solutions were obtained via direct methods in SHELXTL [42]. Subsequent refinement cycles (based on F2) and Fourier synthesis revealed the positions of all non-hydrogen atoms. The atoms were refined using anisotropic displacement tensors. All hydrogen atoms were added to the calculated positions for the final refinement cycle.

2.3. Synthesis of CabNAlBr2 (3)

We added 1.6 M n-BuLi (2 mL, 3.2 mmol) via a syringe to a stirred solution of CabN (1; 0.604 g, 3.0 mmol) in 30 mL of hexane, cooled to −10 °C. The resulting white suspension (LiCabN, 2) was stirred at −10 °C for 2 h and then transferred through a cannula to a suspension of AlBr3 (0.80 g, 3.0 mmol) in 50 mL of toluene at −78 °C. The reaction temperature was first maintained at −78 °C for 1 h, after which the reaction mixture was slowly warmed to room temperature. After being stirred for an additional 12 h, the mixture was filtered. The solvent was removed under vacuum conditions, and the resulting residue was taken up in a minimum of toluene. This was then recrystallized by cooling the solution to −20 °C. Compound 3 was isolated from the reaction solution in 82% yield as colorless crystals (0.95 g, 2.5 mmol). Anal. Calcd: C, 15.51; H, 4.69; N, 3.62. Found: C, 15.71; H, 4.88; N, 3.72. MP: 231–232 °C. IR (Nujol, cm−1): ν(C-H) 3100, 2990; ν(B-H) 2590. 1H NMR (C6D6, 300.1 MHz) δ 1.630 (s, N–CH3), 2.212 (s, N-CH2). 11B NMR (C6D6, 96.3 MHz) δ –2.31 (d, 1B, JB-H = 150 Hz), –4.08 (d, 1B, JB-H = 175 Hz), –5.79 (d, 2B, JB-H = 150 Hz), –9.72 (d, 1B, JB-H = 180 Hz), –11.14 (d, 1B, JB-H = 125 Hz), −11.75 (d, 2B, JB-H = 140 Hz), −12.95 (d, 2B, JB-H = 130 Hz). 13C NMR (C6D6, 75.4 MHz) δ 52.060 (N-CH3), 66.517 (N-CH2), 72.674 (carborane).

2.4. Synthesis of CabNAlMe2 (4)

We added 1.6 M n-BuLi (2 mL, 3.2 mmol) via a syringe to a stirred solution of CabN (1; 0.604 g, 3.0 mmol) in 30 mL of hexane, cooled to −10 °C. The resulting white suspension (LiCabN, 2) was stirred at −10 °C for 2 h and then transferred through a cannula to a suspension of Me2AlBr (0.41 g, 3.0 mmol) in 50 mL of toluene at −78 °C. The reaction temperature was first maintained at −78 °C for 1 h, after which the reaction mixture was slowly warmed to room temperature and it was observed that LiBr precipitation was produced from the solution. After being stirred for an additional 12 h, the mixture was filtered. The solvent was removed under vacuum conditions, and the resulting residue was taken up in a minimum of toluene and then recrystallized by cooling the solution to −20 °C. Compound 4 was isolated from the reaction solution as colorless crystals with a 61% yield (0.47 g, 1.8 mmol). Anal. Calcd: C, 32.67; H, 9.40; N, 5.44. Found: C, 32.74; H, 9.53; N, 5.55. MP: 175–177 °C. IR (Nujol, cm−1): ν(C-H) 3100, 2990; ν(B-H) 2590. 1H NMR (C6D6, 300.1 MHz) δ 0.520 (s, Al-CH3), 1.512 (s, N-CH3), 2.087 (s, N-CH2). 11B NMR (C6D6, 400 MHz) δ −3.18 (d, 1B, JB-H = 155 Hz), −4.31 (d, 1B, JB-H = 137 Hz), −10.10 (d, 2B, JB-H = 170 Hz), −12.88 (d, 6B, JB-H = 135 Hz). 13C NMR (C6D6, 75.4 MHz) δ 10.377 (Al-CH3), 48.774 (N-CH3), 63.124 (N-CH2), 73.800 (carborane).

2.5. Reaction of CabNAlBr2 (3) with LiMe

We added 1.4 M solution of LiMe in diethyl ether (1.6 mL, 2.2 mmol) to a stirred solution of 3 (0.77 g, 2.0 mmol) in toluene (30 mL) at −78 °C via a syringe. The reaction temperature was first maintained at −78 °C for 1 h, after which the reaction mixture was slowly warmed to room temperature. It was observed that LiBr precipitation was produced from the solution. After being stirred for 3 h, the mixture was filtered. The solvent was removed under vacuum conditions, and the resulting residue was taken up in a minimum of toluene and then recrystallized by cooling the solution to −20 °C. Compound 4 was isolated from the reaction solution in colorless crystals with a 20% yield (0.10 g, 0.40 mmol).

3. Results

3.1. Synthesis of CabNAlBr2 (3)

As shown in Scheme 1, intramolecularly stabilized tetracoordinated 2-dimethylaminomethyl-o-carboranyl aluminum compound CabNAlBr2 (3) was synthesized from aluminum tribromide with 2-dimethylaminomethyl-o-carboranyllithium (2) in toluene solvent. Compound 3 was stabilized by the formation of a five-membered ring with C,N-chelating ligand. Notably, compound 3 was moderately unstable in air and decomposed slowly upon contact with O2 and moisture.
It was confirmed that the synthesis and structures of compounds 3 and 4 showed a very similar story to the results obtained for gallium compounds that we have already reported [34]. Detailed information on the structural determinations of compounds 3 and 4 are provided Tables S1–S6 in the Supplementary Materials. Compound 3 was purified from colorless crystals via a process of low-temperature recrystallization in toluene. Satisfactory elemental analysis was performed for compound 3. The structure of compound 3 was proposed based on the corresponding IR, 1H, 11B, and 13C NMR spectroscopic data. Details of the crystal data and a summary of the intensity data collection parameters of compound 3 are provided in Table 1 and Table 2, respectively. The Ortep diagram of compound 3, shown in Figure 1, was determined via the use of single-crystal X-ray diffraction (XRD). The selected interatomic distances and angles are listed in Table 2. Similar to the results obtained in our previously published work,34 the molecule lays on a crystallographic reflection plane and exhibited rigorously imposed reflection symmetry. Seven atoms, namely Al(1), N(1), C(13), C(2), C(1), B(9), and B(12), lay on the symmetry plane. The dimethylamine group of the o-carboranyl ligand was coordinated to the aluminum metal in 3, resulting in the formation of a five-membered chelate ring, N(1)–Al(1)–C(1)–C(2)–C(13). The Al(1), Br(1), Br(1)*, and C(1) moieties were close to planar, with aluminum −0.532(4) Å above the Br(1)Br(1)*C(1) plane. The angles around the aluminum metal center did not deviate much from the tetrahedral angle, except for the C(1)–Al(1)–N(1) angle in the five-membered ring, which was 92.2(4)°. This also influenced the geometry around the o-carborane cluster; the C(2)–C(1)–Al(1) angle (107.9(7)°) within the five-membered ring was similar to that expected at 108°. The Al(1)–N(1) distance in 3 (2.039(1) Å) was longer than that obtained in the corresponding amine-ligated aryl system [o-(Me2NCH2)C6H4]AlBr2 (2.003(5) Å).7 The Al(1)–N(1) distance of 2.039(1) Å was in agreement with the corresponding values observed in the adducts formed between AlX3 and NR3 [43,44,45,46,47,48,49,50]; all distances were longer than the sum of the covalent radii for aluminum and nitrogen (1.95 Å) [51]. The Al(1)–C(1) distance (1.938(1) Å) was similar to that reported for other organoaluminum compounds [6,7,52,53,54,55]. The Al–Br distance of 2.216(2) Å was within the range of typical covalent Al–Br bond distances (2.310–2.316 Å) [7].

3.2. Synthesis of CabNAlMe2 (4)

As shown in Scheme 2, the intramolecularly coordinated 2-dimehylaminomethyl-o-carboranyl dimethylaluminum compound CabNAlMe2 (4) was obtained from dimethylaluminum bromide and LiCabN (2). This compound also forms colorless crystals, demonstrates stability in an inert gas environment, and exhibits slow decomposition upon exposure to air. It is readily soluble in pentane, hexane, and aromatic solvents. Similar to compound 3, IR, 1H, 11B, and 13C NMR spectra exhibited the expected patterns and chemical shifts. The molecular structure of 4 was determined via the use of a single-crystal X-ray diffractometer (XRD). The structure is shown in Figure 2, and details of the crystal data and a summary of the intensity data collection parameters of compound 4 are provided in Table 1 and Table 2, respectively. Similar to compound 3, compound 4 lay on a crystallographic reflection plane and thus exhibited rigorously imposed reflection symmetry. A number of atoms, namely Al(1), N(1), C(13), C(2), C(1), B(9), and B(12), lay on the symmetry plane. Similar to compound 3, the dimethylamine group of the o-carboranyl ligand was coordinated to the aluminum metal in complex 4, resulting in the formation of a five-membered chelate ring, N(1)–Al(1)–C(1)–C(2)–C(13). The Al(1), C(15), C(15)*, and C(1) moieties were close to planar, with aluminum −0.435(4) Å above the C(15)C(15)*C(1) plane. The geometry of 4 was similar to that of 3 owing to the use of intramolecularly coordinated aluminum metal as a Lewis acid and a nitrogen atom as an electron donor. This tetrahedral distortion, with nearly “normal” angles [C(15)–Al(1)–N(1) 109.1(2)° and C(15)–Al(1)–C(1) 113.1(2)°] and a significantly different angle [C(1)–Al(1)–N(1) 88.4(2)°], is caused by the transannular Al–N interaction. The Al(1)–N(1) distance (2.090(5) Å) is in agreement with the corresponding values observed in [(AlMe3)3]4[N-tetramethylcyclam] (2.093(3) Å) [44], (Me3Al)2[(Me2N)2CH2] (2.104(2), 2.112(2) Å) [56], and Me3Al·NMe3 (2.099(1) Å) [43], but is longer than the sum of the covalent radii for Al and N (1.95 Å) [51]. The Al(1)–C(1) distance (2.010(6) Å) is slightly longer than the other two Al–C distances (Al(1)–C(15) and Al(1)–C(15)*, 1.947(5) Å). The Al–C distances of the Me2Al group were similar to those of Me3Al in the gas phase [43,44,45,46,47,48,49,50,51,52,53,54,55,56,57].

3.3. Reaction of CabNAlBr2 (3) with LiMe

Compound 4 can be synthesized via another route using compound 3 (Scheme 3). When compound 3 and MeLi, a Lewis base, are reacted in a 1:2 ratio, compound CabNA1Me2 (4) is obtained through a process of dimethylation. According to Scheme 1, the two bromine atoms of compound 3 can be selectively replaced by Lewis bases to produce compound 4. However, compared to the yield obtained when reacting with Me2AlBr and 2, it was confirmed that the reaction between compound 3 and MeLi generated a very low yield. This result confirmed that compound 3 is easily decomposed in further reactions with Lewis bases such as pyridine, alkyl alcohol, and arylamine (Scheme 3), unlike previously reported gallium compounds. This is probably because compound 3 is more unstable than the gallium compound owing to the strong Lewis acid properties of aluminum [58,59,60]. When the 1H and 13C NMR spectra of this product were compared with those derived from 4, it was confirmed that they were identical.

4. Conclusions

In summary, we prepared new types of 2-(dimethylaminomethyl-o-carboranyl) aluminum bromide and -dimethylaluminum complexes. A combination of X-ray crystallographic and spectroscopic studies, including IR, 1H, 11B, and 13C NMR spectroscopy, confirmed the nature of these compounds. The X-ray crystallographic studies of complexes 3 and 4 provided the first structural data obtained on intramolecularly C,N-coordinated o-carboranylamino aluminum complexes. In compounds 3 and 4, unlike gallium compounds, aluminum atoms preferred only the tetracoordinate by the C,N-chelate ligand in the molecule. However, o-carboranyl C,N-chelating ligands stabilized aluminum compounds, at least in inert environments, and showed the potential for isolation as a well-defined monomeric species. The intramolecular coordination of the N atom of the o-carboranyl ligand and the Al metal center has a significant effect on the stability of the starting materials, aluminum tribromide and dimethylaluminum bromide. This may have been be a result of changes in the electronic properties and bond strength of Al–C and Al–N owing to the C,N-chelation effect. In this study, unlike previous studies, it was confirmed that compounds 3 and 4 did not form a pentacoordinate compound when reacted with a strong Lewis base such as pyridine, but were easily decomposed due to the strong Lewis acidity of aluminum.

Supplementary Materials

The following supporting information can be downloaded at https://www.mdpi.com/article/10.3390/cryst13060877/s1, Tables S1–S6: Detailed information on the structural determinations and structural features of compounds 3 and 4 are provided in the Supplementary Materials.

Author Contributions

Conceptualization, J.-D.L. and H.S.; Designed and performed X-ray crystallography, J.-D.L.; Chemical experiments, J.-D.L.; Data Curation, J.-D.L. and H.S.; Writing—Original Draft Preparation, J.-D.L.; Writing—Review and Editing, J.-D.L. and H.S.; Supervision, J.-D.L.; Project Administration, J.-D.L.; Funding Acquisition, J.-D.L. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data Availability Statement

Crystallographic data for the structure of compounds 3 and 4 were deposited with the Cambridge Crystallographic Data Centre (CCDC No. 2256552 and 2256553). These data can be obtained free of charge via www.ccdc.cam.ac.uk/conts/retrieving.html) and the Supplementary Materials contains detailed crystallographic data (bond lengths, angles, and torsion angles) for compounds 3 and 4.

Acknowledgments

This work was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2022R1F1A1074095).

Conflicts of Interest

The authors declare no conflict of interest.

Appendix A

CCDC 2256552 and 2256553 contain the supplementary crystallographic data of 3 and 4 for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/conts/retrieving.html (or from the Cambridge Crystallographic Data Centre, 12, Union Road, Cambridge CB2 1EZ, UK; Fax: +44 1223 336033; or [email protected]). Additional Supporting Information may be found online in the supporting information tab for this article.

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Crystals 13 00877 sch001 550
Scheme 1. Synthesis of CabNAlBr2 (3).
Scheme 1. Synthesis of CabNAlBr2 (3).
Crystals 13 00877 sch001
Crystals 13 00877 g001 550
Figure 1. Molecular structure of CabNAlBr2 (3). Thermal ellipsoids are drawn at the 30% probability level. (CCDC No. 2256552 in Appendix A).
Figure 1. Molecular structure of CabNAlBr2 (3). Thermal ellipsoids are drawn at the 30% probability level. (CCDC No. 2256552 in Appendix A).
Crystals 13 00877 g001
Crystals 13 00877 g002 550
Figure 2. Molecular structure of CabNAlMe2 (4). The thermal ellipsoids are drawn at the 30% probability level. (CCDC No. 2256553).
Figure 2. Molecular structure of CabNAlMe2 (4). The thermal ellipsoids are drawn at the 30% probability level. (CCDC No. 2256553).
Crystals 13 00877 g002
Crystals 13 00877 sch002 550
Scheme 2. Synthesis of CabNAlMe2 (4).
Scheme 2. Synthesis of CabNAlMe2 (4).
Crystals 13 00877 sch002
Crystals 13 00877 sch003 550
Scheme 3. Reaction of CabNAlBr2 (3) with 2 equiv. of LiMe.
Scheme 3. Reaction of CabNAlBr2 (3) with 2 equiv. of LiMe.
Crystals 13 00877 sch003
Table
Table 1. X-ray crystallographic data and processing parameters for compounds 3 and 4.
Table 1. X-ray crystallographic data and processing parameters for compounds 3 and 4.
Identification codeKOR103KOR106
Empirical formulaC5 H18 B10 N1 Br2 Al1C7 H24 B10 N1 Al1
Formula weight387.08257.37
Temperature293(2) K293(2) K
Wavelength0.71073 Å0.71073 Å
Crystal system, space groupOrthorhombic, Cmc 21Orthorhombic, Cmc 21
Unit cell dimensionsa = 8.9360(3) Å, α = 90.00ºa = 8.9551(3) Å, α = 90.00º
b = 12.0358(9) Å, β = 90.00ºb = 11.9126(9) Å, β = 90.00º
c = 14.7730(4) Å, γ = 90.00ºc = 14.7711(4) Å, γ = 90.00º
Volume1588.9(1) Å−31575.8(1) Å−3
Z, Dcalc4, 1.618 g/cm34, 1.085 g/cm3
Absorption coefficient5.132 mm−10.153 mm−1
F(000)752544
Crystal size0.2 × 0.16 × 0.14 mm0.18 × 0.14 × 0.10 mm
θ range for data collection2.76 to 25.97º2.76 to 25.95º
Limiting indices−8 ≤ h ≤ 10, −8 ≤ k ≤ 14, −18 ≤ l ≤ 0−8 h ≤ 11, −8 ≤ k ≤ 14, −8 ≤ 1 ≤ 18
Reflections collected/unique1693/853 [R(int) = 0.0891]1748/845 [R(int) = 0.0703]
Completeness to θ = 25.9699.9%100.0%
Refinement methodFull-matrix least-squares on F2Full-matrix least-squares on F2
Data/restraints/parameters853/1/98845/1/105
Goodness-of-fit on F20.9231.005
Final R indices [I > 2σ (I)]a R1 = 0.0394, b wR2 = 0.0834a R1 = 0.0448, b wR2 = 0.1110
R indices (all data)a R1 = 0.1020, b wR2 = 0.0881a R1 = 0.0876, b wR2 = 0.1066
Extinction coefficient0.19(3)−0.3(6)
Largest diff. peak and hole0.713 and −0.700 e·Å−30.193 and −0.227 e·Å−3
a R1 = ∑‖Fo|−|Fc‖ (based on reflections with Fo2 > 2σF 2), b wR2 = [∑[w(Fo2−Fc2)2]/∑[w(Fo2)2]]1/2; w = 1/[σ2(Fo2) + (0.095P)2]; and P = [max(Fo2, 0) + 2Fc2]/3(also with Fo2 > 2σF 2)
Table
Table 2. Selected interatomic distances (Å), angles, and torsion angles (°) for 3 and 4.
Table 2. Selected interatomic distances (Å), angles, and torsion angles (°) for 3 and 4.
Compound 3
Al1−C11.938(1)Al1−N12.039(1)
Al1−Br12.216(2)N1−C131.518(2)
Al1−Br#12.216(2)N1–C141.476(1)
C1–C21.649(2)N1–C#141.476(1)
C2–C131.516(2)
C1−Al1−N192.2(4)C13−N1−Al1109.4(8)
C1−Al1−Br1113.7(2)C2−C1−Al1107.9(7)
C1−Al1−Br#1113.7(2)Br#1−Al1−Br1115.7(2)
N1−Al1−Br1109.5(2)C#14−N1−C14108.6(1)
N1−Al1−Br#1109.5(2)C14–N1–C13109.2(8)
Compound 4
Al1−C12.010(6)Al1−N12.090(5)
Al1−C151.947(5)N1−C131.507(7)
Al1−C#151.947(5)N1–C141.488(5)
C1–C21.652(8)N1–C#141.488(5)
C2–C131.532(8)
C1−Al1−N188.4(2)C13−N1−Al1113.2(3)
C1−Al1−C15113.1(2)C2−C1−Al1108.9(3)
C1−Al1−C#15113.1(2)C#15−Al1−C15119.4(3)
N1−Al1−C15109.1(2)C#14−N1−C14108.0(6)
N1−Al1−C#15109.1(2)C14–N1–C13108.3(3)
Symmetry code: (i) x, y, z, (ii) −x, −y, z + 1/2, (iii) −x, y, z + 1/2, (iv) x, −y, z, (v) x + 1/2, y + 1/2, z, (vi) −x + 1/2, −y + 1/2, z + 1/2, (vii) −x + 1/2, y + 1/2, z + 1/2, (viii) x + 1/2, −y + 1/2, z.
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Sohn, H.; Lee, J.-D. Intramolecularly Stabilized o-Carboranyl Aluminum Complexes: Synthesis, Characterization, and X-ray Structural Studies. Crystals 2023, 13, 877. https://doi.org/10.3390/cryst13060877

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Sohn H, Lee J-D. Intramolecularly Stabilized o-Carboranyl Aluminum Complexes: Synthesis, Characterization, and X-ray Structural Studies. Crystals. 2023; 13(6):877. https://doi.org/10.3390/cryst13060877

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Sohn, Honglae, and Jong-Dae Lee. 2023. "Intramolecularly Stabilized o-Carboranyl Aluminum Complexes: Synthesis, Characterization, and X-ray Structural Studies" Crystals 13, no. 6: 877. https://doi.org/10.3390/cryst13060877

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