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Article

A Silicon Complex of 1,4,7,10-Tetraazacyclododecane (Cyclen) with Unusual Coordination Geometry

by
Uwe Böhme
*,
Marcus Herbig
and
Betty Günther
Institut für Anorganische Chemie, TU Bergakademie Freiberg, Leipziger Straße 29, 09599 Freiberg, Germany
*
Author to whom correspondence should be addressed.
Crystals 2025, 15(7), 635; https://doi.org/10.3390/cryst15070635
Submission received: 12 June 2025 / Revised: 7 July 2025 / Accepted: 8 July 2025 / Published: 10 July 2025
(This article belongs to the Section Macromolecular Crystals)
Browse Figures
Versions Notes

Abstract

[1,4,7,10-Tetraazacyclododecano-κ4N1,4,7,10(3-)]silicon(IV) chloride was synthesized from 1,4,7,10-tetraazacyclododecane (cyclen), n-butyl lithium, and silicon tetrachloride. The crystal structure analysis reveals that this cationic compound is a dimer in the solid state with pentacoordinate silicon atoms. The compound was characterized by melting point, IR, and NMR spectroscopy. The quantum chemical analysis shows that this compound might be an interesting precursor to generate a mononuclear silicon (IV) complex with unusual reactivity due to nearly planar tetracoordinate coordination geometry at the silicon atom.

1. Introduction

The macrocyclic alkylamine 1,4,7,10-tetraazacyclododecane (cyclen, 1) and derivatives thereof are often used as ligands to stabilize transition metal ions in a fixed coordination environment [1], which allows for different applications; see examples from the recent literature [2,3,4,5,6,7,8,9,10]. The macrocyclic alkylamine 1 occupies four coordination sites at a central atom and generates unusual coordination geometries in coordination compounds of group 14 elements due to its restricted ring size. This can be seen in various Pb(II) and Ge(II) compounds with cyclen and derivatives thereof, where the central atom is on the tip of a quadratic pyramid (A–C in Scheme 1) [11,12,13]. In contrast to that, the complex of SiCl3+ with 1,4,7-triazacyclononane, which is a macrocyclic ligand with a smaller ring size, leads to a fac-octahedral complex (D in Scheme 1) [11]. Other structurally characterized silicon complexes with macrocyclic amine ligands do not exist to the best of our knowledge. We were curious to find out what coordination geometry 1,4,7,10-tetraazacyclododecane (1) would generate with silicon. Therefore, 1 was deprotonated with n-butyl lithium and reacted with silicon tetrachloride.
Our original hope was that we would find easy access to planar tetracoordinated silicon [14,15]. The main group elements in such an unusual coordination geometry are highly attractive due to the associated reactivity [16].

2. Experimental Section

2.1. General

The reactions were carried out under argon using a standard Schlenk technique [17,18]. NMR spectra were recorded in DMSO-d6 with TMS as internal standard either on a BRUKER DPX 400 spectrometer at 400.13, 100.61 and 79.49 MHz for 1H, 13C and 29Si NMR spectra or on a BRUKER AVANCE III 500 MHz spectrometer at 500.13, 125.76, and 99.36 MHz for 1H, 13C, and 29Si NMR spectra, respectively. IR spectra were recorded on a Nicolet 380 FT-IR by Thermo. Melting points were measured using a “Polytherm A” hot-stage microscope from Wagner and Munz with an attached 52II thermometer from Fluke.

2.2. Synthesis of (1-Hydrogen-1,4,7,10-tetraazacyclododecane)silicon(IV) Chloride (2)

1,4,7,10-Tetraazacyclododecane (2.85 g, 16.6 mmol) was placed in a Schlenk flask. After careful removal of air and moisture from this flask, dry THF (150 mL) was added, and the mixture was cooled to −78 °C under stirring. n-Butyllithium (2.5 mol/L in hexane, 26.6 mL, 66.4 mmol) was added dropwise to the solution in the flask. The mixture was warmed up to 0 °C and stirred for an additional two hours. After this, silicon tetrachloride (2.82 g, 16.6 mmol) was added, and the solution was stirred overnight at room temperature. The solvents were removed in vacuo from the resulting mixture. The residual was extracted with diethyl ether, and the resulting suspension was filtered. The solid residue consisted of lithium chloride and was disposed of. The diethyl ether was removed in vacuo from the filtered solution. The remaining residue was carefully dried in vacuo and used for NMR measurement, yielding 2.61 g of white solid, 67.5%.
A part of the white solid was dissolved in methylene chloride and filtered. The filtered methylene chloride solution was left in the refrigerator at 5 °C for twelve weeks. After this time, colorless crystals of 2.2 CH2Cl2, suitable for X-ray structure analysis, were formed (see the results of structure analysis). A second batch was dissolved in chloroform and, with the same procedure, generated colorless crystals of 2.6 CHCl3. Those were also subjected to crystal structure analysis but yielded inferior results.
Analytical data for 2 (without solvent due to drying procedure):
The compound decomposed slowly above 200 °C.
1H NMR (DMSO-d6, 400 MHz) δ [ppm] = 2.80–3.05 (m, 12 H, CH2), 3.23 (dt, 3JH,H = 5.6 and 12.0 Hz, 2 H, NH-CH2), 3.66 (dt, 3JH,H = 5.6 and 12.0 Hz, 2 H, NH-CH2), 8.68 (s, 1H, N-H).
13C NMR (DMSO-d6, 100 MHz) δ [ppm] = 42.1, 42.5, 46.5, 49.9 (4 × CH2).
29Si NMR (DMSO-d6, 79.5 MHz) δ [ppm] = −75.5.
IR ν [cm-1] = 3406.0 (s), 2962.5 (m), 2896.8 (m), 2836.8 (vs), 2360.3 (m), 2344.3 (w), 1626.3 (m), 1462.4 (m), 1382.6 (w), 1357.6 (w), 1334.5 (m), 1273.7 (w), 1252.4 (w), 1236.8 (m), 1216.7 (m), 1185.4 (m), 1155.8 (vs), 1126.7 (m), 1095.9 (s), 1048.5 (vs), 1016.6 (s), 952.0 (m), 941.7 (m), 929.9 (w), 911.3 (m), 868.5 (w), 851.9 (m), 803.9 (m), 773.1 (m), 704.7 (s), 660.8 (s), 642.3 (w), 624.0 (m), 568.9 (m), 524.7 (m), 460.0 (s), 440.7 (w), 406.7 (w).

2.3. Single-Crystal Structure Determination

Data collection of the title compound was performed on a STOE IPDS-II image plate diffractometer, equipped with a low-temperature device with Mo-Kα radiation (λ = 0.71073 Å) using ω scans at different φ angles. The following software programs were used: data collection: X-AREA; cell refinement: X-AREA; and data reduction: X-RED [19]. The preliminary structure model was derived using direct methods [20], and the structure was refined by full-matrix least-squares calculations based on F2 for all reflections using SHELXL [21]. The hydrogen atom bound to N1 was located from residual electron density peaks and was freely refined. All other hydrogen atoms were included in the structure models in calculated positions and were refined as constrained to the bonding atoms. Crystallographic data are summarized in Table 1.
A crystalline pseudopolymorph of 2 was isolated from chloroform solution. Therein, two crystallographically independent molecules of the dimer, four chloride ions, and twelve molecules of chloroform crystallized in monoclinic space group P21/c. Cell constants were a = 22.6096(6) Å, b = 22.1217(5) Å, c = 19.3902(6) Å, and β = 94.562(2)°. It turned out that these crystals were extremely weakly diffracting, and the final results after refinement of the structure were R1 = 0.0968 for 11,152 Fo > 4σ(Fo) and R1 = 0.1569 for all 17,042 data. This weak dataset is only mentioned here.

2.4. Quantum Chemical Calculations

The geometry optimizations and energy calculations were performed with Gaussian 16 [22]. The molecules were optimized with B3LYP/6-31G(d) including Grimme’s D3 dispersion correction [23,24,25,26,27]. The calculation of Hessian matrices verified the presence of local minima on the potential energy surface with zero imaginary frequencies.
Thermochemical analysis was performed within the Gaussian routines at 298.15 K and 1 atmosphere of pressure. Numeric data are given in the Supporting Information.
The IBO calculations and visualizations were performed using the IBOview software (http://iboview.org/) using the IBO2 scheme [28] and PBE/def2-qzvppd [29,30,31], with univ-JKFIT as an auxiliary basis set used as built in the IBOview software.

3. Results and Discussion

3.1. Preparation and Crystal Structure Analysis

In the first step, 1,4,7,10-tetraazacyclododecane (1) was deprotonated with n-butyllithium (ratio 1:4). To the resulting suspension, an equimolar amount of silicon tetrachloride was added. After the workup procedure (see Experimental Section), a white product was obtained. The 1H and 13C NMR spectra show signals for the ligand molecule, and the 29Si NMR spectrum shows the presence of a pentacoordinate silicon atom. The information available from the NMR spectra did not enable an unambiguous assignment of a chemical structure for the obtained compound. Therefore, crystallization experiments were carried out with two different solvents, in order to obtain crystals suitable for crystal structure analysis. The crystals obtained from chloroform did provide basic information about the composition of the compound. However, the measurement data were not sufficient for a high-quality structural analysis. The crystals from methylene chloride were of much better quality, and the results of this structural analysis are presented here.
The reaction product crystallizes in the triclinic space group P-1 with one molecule of [1,4,7,10-tetraazacyclododecano-κ4N1,4,7,10(3-)]silicon(IV) chloride (2) and two molecules of methylene chloride in the asymmetric unit (Figure S1). The 1,4,7,10-tetraazacyclododecane is deprotonated at the nitrogen atoms N2, N3, and N4 and acts as a trianionic tetradentate chelate ligand. The nitrogen atom N1 is protonated. This proton forms a hydrogen bond to a chloride ion, which acts as a counterion for the cationic silicon complex. The chloride ion is stabilized by further hydrogen bonds to the methylene chloride molecules.
The cationic silicon complex forms a dimer in the solid state by interacting with a symmetry equivalent molecule (Figure 1). The dimer is formed through interactions between the silicon atom and N3 from a second molecule. Thus, a 1,3-diazadisilacyclobutane is formed containing the atoms Si1-N3A-Si1A-N3. The second molecule is generated by an inversion center in the center of this rectangle. The silicon atoms in the dimer are pentacoordinated (Figure 2). The coordination geometry of fivefold coordinated complexes can be analyzed with the parameter τ from Addison et al. [32]. One uses the largest bond angle β and the second largest angle α at the central atom to calculate this parameter with τ = (β-α)/60°. A value of τ = 0 indicates a perfect square pyramid, while τ = 1 indicates a perfect trigonal bipyramid. The largest bond angle in 2 is N1-Si1-N3 with 175.12(6)°, and the second largest is N2-Si1-N4, with 128.60(7)°. The parameter τ calculated from these is 0.78, indicating a distorted trigonal bipyramid. The apical positions of the bipyramid are occupied by the N1 and N3 atoms. The N2, N4, and N3A atoms are in the trigonal plane of the coordination polyhedron.
The Si-N distances vary strongly. There are two short distances Si1-N2 and Si1-N4, with 1.695(1) and 1.708(1) Å; one distance of medium length [Si1-N3A with 1.830(1) Å]; and two long distances, Si1-N1 and Si1-N3, with 1.922(1) and 1.956(1) Å (Table 2). The mean bond length for Si-N(sp3) bonds was determined from the statistical analysis of X-ray structural data, with 1.739 Å [33]. These different bond lengths result from the unique composition of the dimer with pentacoordinate silicon atoms and the folding of the macrocyclic ligand.
The folding of the macrocyclic ligand was analyzed with the least-squares plane, which includes the atoms N1-C1-C2-N2-C3-C4-N3-C5-C6-N4-C7-C8 of the twelve-membered ring. Therefore, it becomes evident that the N1 and N3 atoms lie above this plane by 0.69(1) and 0.71(1) Å, respectively. The N2 and N4 atoms lie in the least-squares plane (0.0 and +0.10(1) Å). This results in a boat-like conformation of the macrocyclic ligand. This conformation is forced by the bonds to the silicon atom.
There is a short intramolecular contact between H5A and N2 in the dimer of the cation of 2. Furthermore, there are a number of intermolecular interactions in the crystal lattice (see Table 3). The hydrogen bond N1-H1C⋯Cl1, with a short distance of 2.28 Å, connects the proton at N1 with the chloride ion. Further hydrogen bonds with longer distances between 2.60 and 2.74 Å connect the hydrogen atoms of methylene chloride with the chloride ion. As seen in Figure 3, the methylene chloride molecules are an important factor for the stabilization of the chloride ions in the crystal lattice.
The second pseudopolymorph, which was crystallized from chloroform, contains two dimeric cations of 2, four chloride ions, and twelve molecules of chloroform in the asymmetric unit. The geometry of the silicon-containing cations in this crystal structure is very similar to the data presented here. The chloride ions and chloroform molecules form a complicated network of hydrogen bonds. This large asymmetric unit (with a large number of parameters) and severe disorder of the chloroform molecules generate weakly diffracting crystals, which in turn lead to poor results in the refinement of the structure. Therefore, this second polymorph is only mentioned here. Anyone interested in the data can retrieve it from the CCDC; the deposition number can be found at the end of the publication in the Supplementary Materials.

3.2. Discussion of the Outcome of the Reaction

Based on the reaction product obtained and the single-crystal structure analysis, it can be assumed that the lithiation of the tetraamine was not complete. A fourfold negatively charged amide ion is probably very difficult to obtain. The partially lithiated amide ion reacts with silicon tetrachloride, yielding 2 (see Scheme 2). The chelating effect of threefold deprotonated 1 is strong enough to break all Si-Cl bonds in silicon tetrachloride, forming a cationic complex with chloride counter ions. The dimerization occurs in order to stabilize the highly reactive monomer. Thereby, a pentacoordinate silicon complex is formed, which is an often-encountered coordination mode in silicon chemistry [34,35,36,37,38,39]. A similar type of head-to-tail dimerization was observed with tridentate O,N,O- and NNN-chelate ligands [15,40].

3.3. Quantum Chemical Calculations and Perspectives in Reactivity

The unusual structure of the dimer of 2 prompts us to consider whether a cleavage into monomers is possible. This possibility was explored using quantum chemical methods. The dication of 2 and the monomeric structures of 3, 4, and 5 were fully geometry-optimized at the B3LYP-D3/6–31G* level. Scheme 3 shows a schematic representation of the molecules together with their relative Gibbs free energies calculated in the gas phase at 298 K. Full coordinates of the molecules, details regarding the energy calculations, graphic presentations of the calculated structures, and essential geometric parameters can be found in the Supporting Information.
Cation 3 carries a proton on the nitrogen atom, as is also the case in the dimer. Cation 4 has the proton on the silicon atom, and the neutral compound 5 is formally formed by deprotonation of 3 or 4. The dimer (cation of 2) has the lowest relative energy in this system.
The splitting of 2 into 3 requires 42.4 kJ/mol. This appears to be a possible process. The energy required to convert 2 into 4 is 227.9 kJ/mol. Deprotonation to form 5 requires an extremely high amount of energy. Whether the necessary energy of 1028.6 kJ/mol can be achieved by chemical reduction and stabilization of the resulting molecule 5 with suitable solvent molecules cannot be judged.
Comprehensive quantum chemical analyses of head–tail-dimerized silicon compounds have already been carried out by Greb et al. [15]. At this point, a few more MO-theoretical considerations on the compound under investigation should be made. IBO calculations provide an insight into the orbital situation of monomer 3 and dimer 2.
The frontier orbitals of monomer 3 are shown in Figure 4. The LUMO is localized in the N-H bond and on the silicon atom. The HOMO is located on the nitrogen atom opposite the N-H bond. Such combinations of closely adjacent occupied and unoccupied frontier orbitals are an important prerequisite for the activation of small molecules. This has been demonstrated recently in numerous examples with compounds of the main group elements [16,41,42].
Figure 5 shows the LUMO of dimer 2, which is mainly antibonding in the Si⋯N interactions between the silicon atom and the nitrogen atom from the other part of the dimer. This indicates that the reduction of 2 could contribute to the cleavage of the dimer.
The IBO scheme only localizes the calculated wave functions in the molecule. Therefore, it is quite interesting that the LUMO is partly located at the silicon atom in the monomer as well as in the dimer. In the monomer, HOMO is localized at the non-protonated nitrogen atom. In the dimer, on the other hand, part of the LUMO is localized at this atom. This results in a weakening of the affected intramolecular Si-N bond in favor of building an intermolecular Si-N interaction. This emphasizes the potential of the monomer state for small-molecule activation, similar to dimer formation.

4. Conclusions

The silicon complex [1,4,7,10-Tetraazacyclododecano-κ4N1,4,7,10(3-)]silicon(IV) chloride (2) was obtained from 1,4,7,10-tetraazacyclododecane (cyclen), butyl lithium, and silicon tetrachloride. The complex forms a head-to-tail dimer with an unusual coordination geometry of the central silicon atom. If it is possible to break up the dimer and generate the monomeric compound, this opens up exciting possibilities for unusual reactivity of such silicon compounds. It has previously been demonstrated that the main group elements in unusual coordination geometries and electronic states show transition metal-like reactivity [16,41,43].
We do not further pursue this type of chemistry, since we have moved on to other subjects [44,45,46]. However, it might be worth building upon these results for other scientists. The preparation of 2 is straightforward and can be conducted with commercially available reagents under inert gas conditions. The title compound seems to be a suitable precursor for coordinatively unsaturated silicon complexes with unusual reactivity [14,15,47,48].

Supplementary Materials

CIF files of the structures were deposited by the Cambridge Crystallographic Data Centre: 2435000 (2.2CH2Cl2); 2435001 (2.6 CHCl3). The copies can be obtained free of charge on written application to CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK (fax: +44-1223 336033); or by access to http://www.ccdc.cam.ac.uk (accessed on 7 July 2025). The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/cryst15070635/s1: Table S1: Sources and purities of chemicals; Figure S1: Asymmetric unit of the crystal structure of 2 showing the atomic numbering scheme. The thermal ellipsoids of the non-hydrogen atoms are drawn at the 50% probability level; Figure S2: 29Si NMR spectrum in DMSO-d6 (79.5 MHz at 298 K); Figure S3: 1H NMR spectrum in DMSO-d6 (400 MHz at 298 K); Figure S4: 13C NMR spectrum (1H decoupled) in DMSO-d6 (100 MHz at 298 K); Figure S5: Structural formula (left) and structure of the optimized dication 2 (right); Table S2: Cartesian Coordinates of the optimized dication 2; Figure S6: Structural formula (left) and structure of the optimized cation 3 (right); Table S3: Cartesian Coordinates of the optimized cation 3; Figure S7: Structural formula (left) and structure of the optimized cation 4 (right); Table S4: Cartesian Coordinates of the optimized cation 4; Figure S8: Structural formula (left) and structure of the optimized neutral molecule 5 (right); Table S5: Cartesian Coordinates of the optimized neutral molecule 5; Table S6: Essential geometric parameters of the optimized molecules (bond lengths in Å, angles in °). Data of the crystal structure of 2 are showed for comparison; Table S7: Energy calculations at the B3LYP-D3/6-31G* level of theory.

Author Contributions

Conceptualization, U.B. and M.H.; data curation, U.B.; formal analysis, U.B. and M.H.; investigation, U.B., M.H. and B.G.; methodology, U.B. and M.H.; validation, U.B., M.H. and B.G.; visualization, U.B. and M.H.; writing—original draft, U.B.; writing—review and editing, U.B. and M.H. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data Availability Statement

The original contributions presented in this study are included in the article/Supplementary Materials. Further inquiries can be directed to the corresponding author.

Acknowledgments

The authors thank TU Bergakademie Freiberg (Freiberg, Germany) for financial support. The authors are grateful to Beate Kutzner (TU Bergakademie Freiberg, Institut für Anorganische Chemie) for NMR measurements. The authors acknowledge computing time on the compute cluster of the Faculty of Mathematics and Computer Science of Technische Universität Bergakademie Freiberg, operated by the computing center (URZ) and funded by Deutsche Forschungsgemeinschaft (DFG) under DFG grant number 397252409.

Conflicts of Interest

The authors declare no conflicts of interest.

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Crystals 15 00635 sch001
Scheme 1. Examples for compounds of group 14 elements with macrocyclic amine ligands from the literature.
Scheme 1. Examples for compounds of group 14 elements with macrocyclic amine ligands from the literature.
Crystals 15 00635 sch001
Crystals 15 00635 g001
Figure 1. Dimer of 2.2CH2Cl2 in the solid state (symmetry operation −x + 1,−y + 1,−z). The thermal ellipsoids of the non-hydrogen atoms are drawn at the 50% probability level.
Figure 1. Dimer of 2.2CH2Cl2 in the solid state (symmetry operation −x + 1,−y + 1,−z). The thermal ellipsoids of the non-hydrogen atoms are drawn at the 50% probability level.
Crystals 15 00635 g001
Crystals 15 00635 g002
Figure 2. Dication of 2 in the solid state in ball and stick representation. A semi-transparent coordination polyhedron is shown for silicon atom 1. Chloride ions and methylene chloride molecules are omitted for clarity.
Figure 2. Dication of 2 in the solid state in ball and stick representation. A semi-transparent coordination polyhedron is shown for silicon atom 1. Chloride ions and methylene chloride molecules are omitted for clarity.
Crystals 15 00635 g002
Crystals 15 00635 g003
Figure 3. Hydrogen bond network which stabilizes the chloride ions in the crystal lattice of 2 (symmetry equivalent atoms of the silicon containing dimer are generated by symmetry operation #1 = -x+1,-y+1,-z; hydrogen bond network between chloride ions by symmetry operation #2 = -x+2,-y+1,-z+1; see also Table 3).
Figure 3. Hydrogen bond network which stabilizes the chloride ions in the crystal lattice of 2 (symmetry equivalent atoms of the silicon containing dimer are generated by symmetry operation #1 = -x+1,-y+1,-z; hydrogen bond network between chloride ions by symmetry operation #2 = -x+2,-y+1,-z+1; see also Table 3).
Crystals 15 00635 g003
Crystals 15 00635 sch002
Scheme 2. Reaction of ligand 1 with n-butyllithium, silicon tetrachloride, and formation of 2.
Scheme 2. Reaction of ligand 1 with n-butyllithium, silicon tetrachloride, and formation of 2.
Crystals 15 00635 sch002
Crystals 15 00635 sch003
Scheme 3. Relative energies of the calculated molecules 2–5 from quantum chemical calculations.
Scheme 3. Relative energies of the calculated molecules 2–5 from quantum chemical calculations.
Crystals 15 00635 sch003
Crystals 15 00635 g004
Figure 4. Frontier orbitals of monomer 3 (top—LUMO, bottom—HOMO).
Figure 4. Frontier orbitals of monomer 3 (top—LUMO, bottom—HOMO).
Crystals 15 00635 g004
Crystals 15 00635 g005
Figure 5. Frontier orbitals of the dimer 2 (top–LUMO, bottom–HOMO; notice that there are degenerate frontier orbitals with the same shape in the other part of the molecule).
Figure 5. Frontier orbitals of the dimer 2 (top–LUMO, bottom–HOMO; notice that there are degenerate frontier orbitals with the same shape in the other part of the molecule).
Crystals 15 00635 g005
Table 1. Crystallographic data from data collection and refinement processes for 2.2CH2Cl2.
Table 1. Crystallographic data from data collection and refinement processes for 2.2CH2Cl2.
ParameterValue
FormulaC20H42Cl10N8Si2
Mr805.29
T (K)153 K
λ (Å)0.71073
Crystal systemTriclinic
Space groupP 1
a (Å)9.0804(6)
b (Å)9.7215(7)
c (Å)11.0648(7)
α (°)67.070(5)
β (°)88.222(6)
γ (°)75.748(5)
V (Å3)869.57(11)
Z1
ρcalc (g.cm−3)1.538
μ (mm−1)0.898
F(000)416
θmax (°)27.323
Reflections collected/unique [Rint]25,897/3833 [R(int) = 0.0392]
Completeness to θ = 25.242°98.1%
Absorption correctionface-indexing absorption correction
Max. and min. transmission0.9405 and 0.7674
Data/restraints/parameters3833/0/185
GoF on F21.096
Final R indices [I > 2sigma(I)]R1 = 0.0322, wR2 = 0.0811
R indices (all data)R1 = 0.0351, wR2 = 0.0852
Largest peak and hole (e.Å−3)0.348 and −0.552
Table 2. Bond lengths [Å] and angles [°] for 2 (symmetry transformation used to generate equivalent atoms with label A: −x + 1,−y + 1,−z).
Table 2. Bond lengths [Å] and angles [°] for 2 (symmetry transformation used to generate equivalent atoms with label A: −x + 1,−y + 1,−z).
ParameterValueParameterValue
Si1-N11.922(1)Si1-N3A1.830(1)
Si1-N21.695(1)Si1-Si1A2.7972(8)
Si1-N31.956(1)
Si1-N41.708(1)
N1-Si1-N3175.12(6)N2-Si1-N3A113.77(7)
N2-Si1-N4128.60(7)N4-Si1-N3A117.12(6)
N2-Si1-N188.69(6)N1-Si1-N3A99.96(6)
N4-Si1-N189.46(6)N3-Si1-N3A84.81(6)
N2-Si1-N388.42(6)
N4-Si1-N389.28(6)
Table 3. Hydrogen bonds for 2 (values are given in Å and °; symmetry transformations used to generate equivalent atoms: #1 = −x + 1,−y + 1,−z; #2 = −x + 2,−y + 1,−z + 1).
Table 3. Hydrogen bonds for 2 (values are given in Å and °; symmetry transformations used to generate equivalent atoms: #1 = −x + 1,−y + 1,−z; #2 = −x + 2,−y + 1,−z + 1).
D-H⋯Ad(D-H)d(H⋯A)d(D⋯A)<(DHA)
C5-H5A⋯N2#10.992.553.176(2)121.3
N1-H1C⋯Cl10.89(2)2.28(2)3.1556(14)166.1(19)
C9-H9A⋯Cl10.992.603.578(2)170.2
C9-H9B⋯Cl1#20.992.743.5987(19)145.8
C10-H10B⋯Cl10.992.613.533(2)155.7
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Böhme, U.; Herbig, M.; Günther, B. A Silicon Complex of 1,4,7,10-Tetraazacyclododecane (Cyclen) with Unusual Coordination Geometry. Crystals 2025, 15, 635. https://doi.org/10.3390/cryst15070635

AMA Style

Böhme U, Herbig M, Günther B. A Silicon Complex of 1,4,7,10-Tetraazacyclododecane (Cyclen) with Unusual Coordination Geometry. Crystals. 2025; 15(7):635. https://doi.org/10.3390/cryst15070635

Chicago/Turabian Style

Böhme, Uwe, Marcus Herbig, and Betty Günther. 2025. "A Silicon Complex of 1,4,7,10-Tetraazacyclododecane (Cyclen) with Unusual Coordination Geometry" Crystals 15, no. 7: 635. https://doi.org/10.3390/cryst15070635

APA Style

Böhme, U., Herbig, M., & Günther, B. (2025). A Silicon Complex of 1,4,7,10-Tetraazacyclododecane (Cyclen) with Unusual Coordination Geometry. Crystals, 15(7), 635. https://doi.org/10.3390/cryst15070635

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