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DOI: 10.1039/C9NJ02217A (Paper) New J. Chem., 2019, 43, 12601-12608

Structural diversity of the complexes of monovalent metal d10 ions with macrocyclic aggregates of iso-tellurazole N-oxides†

Jin Wang , Peter C. Ho , James F. Britten , Valerie Tomassetti and Ignacio Vargas-Baca *
McMaster University, Department of Chemistry and Chemical Biology, 1280 Main Street West, Hamilton, Ontario L8S 4M1, Canada. E-mail: vargas@chemistry.mcmaster.ca

Received 30th April 2019 , Accepted 17th July 2019

First published on 17th July 2019

Abstract

The reactions of iso-tellurazole N-oxides with monocations of the coinage metals yielded a family of coordination complexes with a remarkable variety of compositions and structures. All new species were identified by single-crystal X-ray diffraction. In all cases, the macrocyclic aggregation of the organo-chalcogen heterocycles through Te⋯O chalcogen bonding interactions is preserved and the metal ions are coordinated by tellurium. Copper and gold formed complexes with the tetramers. The lighter element acquired a κ4Te,κ1O pentacoordinated square pyramidal structure with a triflate anion in the apical position. The preference of the heavier metal for a linear κ1Te,κ1Cl coordination geometry permitted the formation of a binuclear complex. Silver demonstrated a unique preference for coordinating to the hexamer; two distinct examples showed a structure with a pair of endocyclic κ2Te,κ2O metal ions bridged by two triflate anions; the other two chalcogen atoms are located at trans-annular positions and each coordinates a κ1Te,κ1O,κ1C silver ion, also bonded to an aromatic carbon and another triflate anion.

Introduction

Heavy analogues of crown ethers have long attracted interest because their soft electron-donor atoms often give rise to unique reactivity patterns with metal ions. Compared to macrocycles that contain thioether groups, ligands with the heavier chalcogens, selenium and especially tellurium, are much less studied.1–3 The first selena-crown ethers were prepared from propane-1,3-bis(selenolate) and dibromoalkanes by Pinto;4 chromatography allowed the separation of those rings by size. Soon after, the ability of such macrocycles to coordinate Pd(II) was demonstrated.5 That breakthrough was followed by complexes of other d-block6–10 and main-group elements,11,12 sometimes with modifications to the macrocycle's backbone and alternative syntheses. Investigations of macrocyclic complexes of tellurium ligands usually are complicated by side-reactions enabled by the large size of the chalcogen atom and the polarity of the Te–C bond;2 oxidation, hydrolysis,13 and olefin extrusion from the –Te–CH2–CH2– sequence14 are common. The first telluracrown ether, 1,5-ditelluracyclooctane, was prepared from 1,3-dibromopropane and Na2Te and shown to undergo two-electron oxidation with formation of a transannular Te–Te bond.15 Pyrolysis of the corresponding dichloride caused significant rearrangement into 1,1,5,5,9,9-hexachlorotritelluracyclododecane, which could be reduced to the tritelluracyclododecane.16 However, no coordination complexes have been reported from such telluracoronands.

Electron-donor atoms of other elements such as nitrogen, oxygen and sulfur have been incorporated into the backbone of selena- and telluramacrocycles to facilitate their syntheses and improve their stability. This approach has allowed the synthesis of complexes of alkaline earth,17,18 d-block,6,8,10,19–22 p-block23–25 and lanthanoid26 elements with selenium ligands. In the case of tellurium-containing macrocycles, complexes of Pd(II), Pt(II) and Rh(III) with 1,10-ditellura-4,7,13,16-tetraoxacyclooctadecane,19 Mn(0), Ag(I), Mn(I), Cu(I), Pd(II), Pt(II), Rh(III) with dithia-tellura crowns of various sizes were characterized.27,28 On the other hand, a Sc(III) complex of 1,10-ditellura-4,7,13,16-tetraoxacyclooctadecane was prepared and spectroscopically characterized but spontaneous decomposition prevented its structural characterization.26 Macrocyclic ditellura-tetraza Schiff bases form κ2N,κ2Te complexes with Pd(II) and Pt(II) but κ4N,κ2Te with Ni(II).29–33 Several telluraporphyrinoids34–41 have been prepared but their coordination chemistry has only been examined with PdII.42,43 Although macrocyclic oxatelluranes have been prepared,44,45 there are no reported studies of their reactions with transition metals.

In contrast with the conventional methods of macrocycle synthesis, we recently reported the spontaneous assembly of annular aggregates of iso-tellurazole N-oxides (Scheme 1; 1, 2) into macrocyclic tetra- and hexamers (14, 16) that are persistent and exist in equilibrium in solution.46–48 These species do display characteristic chemical properties of macrocycles; for example, the formation of adducts with fullerenes, hosting small molecules and coordination of metal ions. Square complexes of the tetramers have been obtained with d8 metal ions such as [Pd(1b4)]2+ and [Pt(1c4)]2+; the related octahedral complex [RhCl2(1b4)]+ has two trans chloro ligands completing the coordination sphere.49 The formation of these complexes is remarkable considering that the macrocycles are formed by Te⋯O chalcogen bonding (ChB) interactions, i.e. the reversible intermolecular interaction between the electrophilic tellurium centers and the nucleophilic oxygen atoms. The latter are reasonably good Lewis bases capable of forming bonds to haloboranes and being protonated by strong acids.50 Arguably, ligand field effects contribute to stabilize the macrocyclic square-planar or octahedral complexes of the tetramers. In this report we present our investigation of the coordination complexes of d10 ions of the coinage metals, free of ligand-field effects as their d orbitals are fully occupied.


image file: c9nj02217a-s1.tif
Scheme 1 Iso-tellurazole N-oxides and their macrocyclic aggregates.

Experimental section

Materials and methods

Air-sensitive materials were handled in a glove box or using standard Schlenk methods under an inert atmosphere of nitrogen or argon. All solvents were dehydrated and degassed by distillation or using an Innovative Technology solvent purification system. Photosensitive materials were handled under red LED light. 2Cu(CF3SO3)·(CH3C6H5), Ag(CF3SO3) and HAuCl4 were used as received from Sigma Aldrich. [AuCl(C4H8S)]51 and the iso-tellurazoles N-oxides 1b47 and 1c49 were prepared as previously described.

Instrumentation

All samples for nuclear magnetic resonance (NMR) spectroscopy were prepared by dissolving the compound in a deuterated solvent. NMR spectra were collected using Bruker AVANCE 200 MHz, 500 MHz, 600 MHz or 700 MHz spectrometers operating at 298 K; The 1H and 13C spectra were processed using Bruker TopSpin 3.2 software; δ chemical shift values were measured from the resonance of residual nuclei in the deuterated solvent and are reported with respect to the corresponding resonances of tetramethylsilane. The acquisition of 125Te NMR was attempted for all new compounds but no resonance could be observed due to their low solubilities.

Melting points were determined with a Uni-Melt Thomas Hoover capillary melting point apparatus and are reported uncorrected. Combustion elemental analyses were carried out by the London Metropolitan University elemental analysis service (London, United Kingdom). UV-vis absorption spectra were obtained in 10 mm quartz cuvettes on Cary 5000 or Cary 300 spectrometers in dual beam mode. Raman vibrational spectra were obtained with a Renishaw Invia Laser Raman spectrometer with a 25 mW argon ion laser (514 nm, 1800 L mm−1 grating). IR spectra were measured with a Thermo Scientific Nicolet 6700 FT-IR spectrometer equipped with a Smart iTX attenuated total reflectance (ATR) sample-analyzer attachment.

Single-crystal X-ray diffraction patterns were acquired from samples mounted on nylon loops (Hampton, CA) or MiTeGen Micromounts (Ithaca, NY) and coated with Paratone®-n oil. A Bruker APEX2 diffractometer was used to collect data at 100 K with Mo-Ka radiation (λ = 0.71073 Å). A CCD area detector was used. The diffractometer was equipped with a low-temperature accessory Oxford cryostream. Three different orientations were used with a minimum of 50 frames for the determination of the unit cell parameters and final cell advancement after integration with SAINT.52 SADABS53 or a semiempirical absorption correction was used for the absorption correction. All structures were solved with direct methods then refined using SHELXT54 by the full-matrix least-squares techniques on F2. All non-hydrogen atoms were assigned anisotropic thermal parameters. Appropriate riding models were used to place hydrogen atoms in idealized positions. Satisfactory refinement of the structures with heavily-disordered solvent molecules was accomplished with the solvent Mask tool in Olex2.55

Syntheses

[Cu(1b4)(CF3SO3)]. A solution of 1a (9.7 mg, 0.034 mmol) in 0.5 g anhydrous THF was added to a stirring solution of 2Cu(CF3SO3)·CH3C6H5 (2.2 mg, 0.0042 mmol) in 0.5 g anhydrous THF. Orange crystals of the product formed by slow evaporation of the solvent. Yield 72%. M.p.: 188 °C (d); 1H NMR (700 mHz, CD2Cl2): δ 7.26–7.48 (m, 5H), 7.14 (s, 1H), 1.842 (s, 3H); 13C NMR (700 mHz, CD2Cl2): δ 158.0 (s, 1C), 152.5 (s, 1C), 140.5 (s, 1C), 129.7 (s, 2C), 128.1 (s, 1C), 127.9 (s, 2C), 127.5 (s, 1C), 16.1 (s, 1C); no 125Te resonance could be observed. UV-vis absorption (λmax, nm/ε, L mol−1 cm−1): 321//1881; IR (cm−1): 1586.6 m br, 1495.0 m, 1442.4 m, 1303.4 w, 1228.4 m br, 1207.9 s, 1153.7 m, 1104.2 m, 1016.8 s, 927.1 s, 907.1 m, 864.3 m, 846.7 m, 759.9 m, 693.1 s, 630.2 s, 612.2 s, 579.9 s; Raman cm−1: 1595.3 s, 1494.7 s, 1466.0 m, 1408.2 s, 1216.8 m, 1000.1 m; E.A. (calcd for C41H36N4O7Te4Cu1S1F3, found): C (36.22, 36.23), H (2.67, 2.76), N (4.12, 4.04). Orange single crystals of [Cu0.4(1b4)(CF3SO3)0.4]·0.6THF suitable for X-ray diffraction were grown over one day by slow evaporation of a mixture of the reagents in CH2Cl2.
[Au2Cl2(1b4)]. [Au(Cl)(C4H8S)] (5.2 mg, 0.0162 mmol) in 0.5 mL anhydrous CH2Cl2 was mixed with a solution of 1b (9.29 mg, 0.0324 mmol) in CH2Cl2. The solution was stirred for 5 minutes to complete the reaction. Diffusion of Et2O vapor at −20 °C produced photosensitive yellow single crystals suitable for X-ray diffraction. Yield 81%. 1H (700 mHz, CD2Cl2): 7.28–7.48 (m, 5H), 7.11 (s, 1H), 2.10 (s, 3H); no 13C nor 125Te resonance could be observed due to the low solubility of the compound. UV-vis absorption (λmax, nm//ε, L mol−1 cm−1): 322/64[thin space (1/6-em)]720. IR (cm−1): 1572.8 m, 1493.4 m, 1441.1 m, 1212.5 m, 1093.0 s, 1026.9 m, 923.8 m, 904.0 m, 852.3 m, 755.3 s, 707.2 m, 689.8 s, 618.9 m, 610.9 s, 575.1 m; Raman (cm−1): 1596.8 s, 1497.8 s, 1475.09 s, 1441.7 m, 1213.7 m, 998.5 m; analysis (calcd for C64H54N6O18Te6Ag4S4F12, found): C (29.80, 29.75), H (2.25, 2.32), N (3.48, 3.47).
{[Ag2(μ-CF3SO3)2(1b6)]Ag2(CF3SO3)2}. A solution of Ag(CF3SO3) (4.6 mg, 0.0178 mmol) in 0.5 mL anhydrous THF was added to a solution of 1b (7.65 mg, 0.027 mmol) in 1.0 mL of anhydrous THF. A yellow precipitate, sensitive to ambient light, formed upon mixing. Yield 89%. M.p.: 195 °C (d.); 1H (700 mHz, CD3CN): δ 7.39–7.47 (m, 5H), 7.29 (s, 1H), 2.02 (s, 3H). 13C NMR (700 mHz, CD3CN) δ 130.5 (s, 2C), 129.8 (s, 1C), 129.1 (s, 2C), 124.9 (s, 1C), 123.1 (s, 1C), 121.3 (s, 1C), 119.5 (s, 1C), 16.5 (s, 1C). No 125Te resonance could be observed. M.p.: 207 °C (d). UV-vis absorption (λmax, nm//ε, L mol−1 cm−1): 320//24[thin space (1/6-em)]600; IR (cm−1): 2957.8 m, 1586.9 m, 1494.7 m, 1438.9 m, 1296.8 m, 1217.5 m, 1193.6 m, 1158.5 s, 1097.8 m, 1021.1 m, 1000.3 m, 927.9 m, 909.6 m, 882.8 m, 864.0 m, 773.0 m, 707.1 m, 692.0 s, 630.9 s, 611.4 s, 573.2 m; Raman (cm−1): 1595.7 s, 1499.7 s, 1477.0 s, 1440.6 m, 1342.7 m, 1220.3 m, 1096.1 m, 998.9 m, 708.8 m, 612.137 m, 578.6 m, 403.6 m, 345.0 m; E.A. (calcd for C64H54N6O18Te6Ag4S4F12, found): C (27.97, 27.85), H (1.98, 2.09), N (3.06, 3.02). Yellow single crystals suitable for X-ray diffraction were grown by slow diffusion of Ag(CF3SO3) into 1b, both reagents in THF solution.
{[Ag2(μ-CF3SO3)2(1c6)]Ag2(CF3SO3)2}. A solution of Ag(CF3SO3) (3.7 mg, 0.0144 mmol) in 0.5 mL anhydrous CH2Cl2 was added with stirring to a solution of 1c (8.62 mg, 0.0216 mmol) in 0.5 mL anhydrous CH2Cl2. The solution became dark yellow and was stirred for 15 minutes; yellow crystals formed by slow evaporation. Yield: 78%. M.p.: 208 °C (d.). 1H (700 mHz, CD2Cl2): δ 7.29–7.50 (m, 18H), 7.14 (s, 4H), 7.08 (s, 2H), 2.07 (s, 6H), 1.80 (s, 12H), 1.35 (s, 72H), 1.32 (s, 36H). 13C NMR (700 mHz, CD2Cl2): 163.9, 151.5, 151.4, 151.3, 137.6, 137.5, 130.5, 129.9, 125.8, 123.9, 123.4, 121.6, 119.8, 117.9, 35.3, 35.2, 31.608, 31.5, 16.9, 16.3. No 125Te resonance could be observed. UV-vis absorption (λmax, nm//ε, L mol−1 cm−1): 277//49[thin space (1/6-em)]220, 338//163[thin space (1/6-em)]630, 421//16[thin space (1/6-em)]060; IR (cm−1): 2957.8 m, 1583.7 m, 1477.8 m, 1363.9 m, 1309.8 m, 1226.0 m, 1190.7 s, 1170.2 m, 1097.1 m, 1015.9 m, 994.8 m, 895.5 m, 876.8 m, 840.0 m, 733.1 m, 708.0 m, 651.9 m, 628.9 s, 590.8 m, 576.1 m. Raman (cm−1): 1487.3 s, 1492.4 s, 1426.6 m, 1382.3 m; analysis (calcd for C112H150N6O18Te6Ag4S4F12, found): C (39.31, 39.39), H (4.42, 4.38), N (2.46, 2.49). Yellow single crystals suitable for X-ray diffraction were grown over one day by slow evaporation of a dilute mixture of the reagents in CH2Cl2.

Results and discussion

Synthesis and properties

Quick color changes were observed on all cases upon mixing the metal salts with the iso-tellurazole N-oxides in solution. The products precipitated within a few minutes but crystalline samples could be obtained from dilute mixtures. The products thus formed were sparingly soluble in common organic solvents, which complicated their spectroscopic characterization. No 125Te magnetic resonance could be observed in all cases and the 13C NMR spectrum could not be obtained for the gold compound. Electrospray mass spectrometry has been useful in the characterization of other metal complexes of 1b and 1c49 but, in the present case, the spectra only displayed the patterns characteristic of the ligands. Therefore, characterization of the products relied mainly on single-crystal X-ray diffraction. Details of the crystallographic determination are presented in Table 1, selected measurements for each structure are compiled in Table 2. Most crystals contained heavily disorder solvent molecules, which required solvent masking to complete the refinement. Satisfactory results of combustion elemental analyses were obtained only when the samples were subject to vacuum for prolonged periods of time to evaporate the crystallization solvent.
Table 1 Crystallographic and refinement parameters for the reported complexes
Crystal composition [Cu0.4(1b4)(CF3SO3)0.4]·0.6THF {[Ag2(μ-CF3SO3)2(1c6)]Ag2(CF3SO3)2} {[Ag2(μ-CF3SO3)2(1b6)]Ag2(CF3SO3)2} [Au2Cl2(1b4)]
a R 1 = ∑‖Fo| − |Fc‖/∑|Fo|, wR2 = {∑[w(Fo2 − Fc2)2]/∑w(Fo2)2}½.
Empirical formula C42.78H40.76Cu0.41F1.22 C116H158Ag4Cl8F12 C64H54Ag4F12 C40H36Au2
N4O5.81S0.41Te4 N6O18S4Te6 N6O18S4Te6 Cl2N4O4Te4
Formula weight/g mol−1 1276.14 3761.39 2748.56 1611.96
Temperature/K 296.15 296.15 296.15 100.15
Crystal system Tetragonal Triclinic Trigonal Triclinic
Space group I[4 with combining macron]2d P[1 with combining macron] R[3 with combining macron] P[1 with combining macron]
a/Å 11.5411(4) 12.6097(6) 19.968(2) 9.4627(16)
b/Å 11.5411(4) 16.7724(8) 19.968(2) 11.961(2)
c/Å 43.659(2) 17.9715(9) 26.815(3) 19.749(3)
α/° 90 88.457(2) 90 90.599(3)
β/° 90 88.965(2) 90 99.141(3)
γ/° 90 87.865(2) 120 96.104(3)
Volume/Å3 5815.2(5) 3796.3(3) 9260(2) 2193.4(6)
Z 4 1 3 2
ρ calc/g cm−3 1.458 1.645 1.479 2.441
μ/mm−1 2.187 1.905 2.145 9.454
F(000) 2436.0 1848.0 3888.0 1472.0
Crystal size/mm3 0.09 × 0.09 × 0.03 0.2 × 0.15 × 0.1 0.2 × 0.2 × 0.1 0.18 × 0.18 × 0.18
Radiation MoKα (λ = 0.71073 Å) MoKα (λ = 0.71073 Å) MoKα (λ = 0.71073 Å) MoKα (λ = 0.71073 Å)
2Θ range for data collection/° 3.65 to 56.58 3.232 to 52.718 2.802 to 54.268 2.09 to 53.424
Index ranges −15 ≤ h ≤ 15, −15 ≤ k ≤ 12, −44 ≤ l ≤ 58 −15 ≤ h ≤ 15, −20 ≤ k ≤ 20, −22 ≤ l ≤ 22 −25 ≤ h ≤ 25, −25 ≤ k ≤ 25, −34 ≤ l ≤ 34 −11 ≤ h ≤ 11, −15 ≤ k ≤ 15, −24 ≤ l ≤ 24
Reflections collected 22[thin space (1/6-em)]244 89[thin space (1/6-em)]837 79[thin space (1/6-em)]012 52[thin space (1/6-em)]282
Independent reflections 3623 [Rint = 0.0774, RSigma = 0.0685] 15[thin space (1/6-em)]445 [Rint = 0.0581, RSigma = 0.0435] 4566 [Rint = 0.0419, RSigma = 0.0236] 9240 [Rint = 0.0686, RSigma = 0.0581]
Data/restraints/parameters 3626/0/138 15[thin space (1/6-em)]445/6/805 4566/309/245 9240/456/509
Goodness-of-fit on F2 1.032 1.067 1.674 1.078
Solvent masking Yes Yes Yes No
Final R indexes [I ≥ 2σ(I)]a R 1 = 0.0530, wR2 = 0.1277 R 1 = 0.0437, wR2 = 0.1070 R 1 = 0.1169, wR2 = 0.3546 R 1 = 0.0371, wR2 = 0.0775
Final R indexes [all data]a R 1 = 0.0677, wR2 = 0.1326 R 1 = 0.0647, wR2 = 0.1170 R 1 = 0.1400, wR2 = 0.3885 R 1 = 0.0599, wR2 = 0.0839
Largest diff. peak/hole/e Å−3 2.08/−1.24 2.74/−1.09 4.26/−1.77 1.79/−1.75
Flack parameter −0.001(19) n/a n/a n/a

Table 2 Selected bond distances (Å) and angles (°) in the structures of the complexes
Crystal composition [Cu0.4(1b4) (CF3SO3)0.4]·0.6THF {[Ag2(μ-CF3SO3)2(1c6)]Ag2(CF3 SO3)2} {[Ag2(μ-CF3SO3)2(1b6)]Ag2(CF3 SO3)2} [Au2Cl2(1b4)]
M Cu Ag Ag Au
Bond distance (Å)
Te1−C1 2.10(1) 2.117(5), 2.130(5), 2.146(5) 2.08(1) 2.095(8), 2.106(7), 2.108(8), 2.126(8)
Te1−N1 2.2228(8) 2.227(5), 2.234(4), 2.242(5) 2.22(1) 2.199(7), 2.230(7), 2.259(6), 2.265(6)
Te1−O1 2.249(8) 2.178(3), 2.210(4), 2.224(4) 2.19(1) 2.172(6), 2.189(5), 2.217(6), 2.239(6)
N1−O1 1.34(1) 1.362(5), 1.366(6), 1.366(6) 1.42(1) 1.358(8), 1.368(8), 1.368(8), 1.386(9)
N1−O1 4.45(1) 4.400(6), 4.425(6), 4.435(5) 4.38(1) 4.370(8), 4.404(9), 4.404(9), 4.407(8)
C1−C2 1.36(1) 1.345(7), 1.352(7), 1.357(7) 1.46(2) 1.34(1), 1.36(1)
C2−C3 1.48(2) 1.438(7), 1.438(8), 1.452(7) 1.40(2) 1.42(1), 1.43(1), 1.46(1), 1.47(1)
C3−N1 1.28(1) 1.306(6), 1.307(7), 1.312(7) 1.25(2) 1.30(1), 1.309(9), 1.31(1), 1.319(9)
Te1−Te1 5.201(1) 7.5568(6), 8.2723(6), 8.5508(6) 8.410(2) 5.4251(9), 5.4989(9), 5.604(1), 5.8908(9)
Te−M 2.644(2), 2.704(3) 2.7007(5), 2.7429(5), 2.7870(5) 2.569(3), 2.680(5), 2.801(5) 2.5116(7), 2.5233(7), 3.3323(8)
M−O 2.20(4) 2.178(3), 2.210(4), 2.224(4) 2.15(2)
M−Cl 2.295(2), 2.305(2)
Bond angle (°)
N1−Te1−O1 167.0(3) 168.3(1), 169.2(2), 171.5(2) 167.2(4) 160.9(2), 163.3(2), 164.2(2), 165.9(2)
N1−Te1−C1 77.4(3) 76.1(2), 76.2(2), 76.3(2) 75.6(5) 75.5(3), 76.1(3), 76.2(3), 76.3(3)
O1−N1−Te1 125.9(6) 125.8(3), 127.1(3), 127.3(3) 123.0(8) 123.7(4), 124.8(4), 126.8(4)
Torsion angle (°)
Te1−N1−O1−Te1 35.0(8) 38.1(5), 48.4(5), 43.5(5) 65(1) 38.0(7), 45.8(6), 61.6(6), 81.4(5)
N1−O1−Te1-C1 113.3(6) 85.9(4), 86.1(3), 86.3(4) 96.7(8) 79.8(5), 111.1(5), 173.4(5), 173.9(4)
C1−Te1−N1−O1 180.0(8) 175.2(5), 179.5(5), 172.9(4) 174(1) 173.4(6), 178.2(6), 174.2(6), 177.8(6)

Copper(I). The crystal of the product of the reaction of 1b with Cu(CF3SO3) in THF belongs to the I[4 with combining macron]2d space group. It features the tetramer 1b4 in its boat conformation (Fig. 1). The metal ion displays a distorted square pyramidal coordination geometry with the anion at the apical position. The S4 symmetry of the macrocycle allows the complex to sit in a −4 special position, this situation enables disorder and depletion of cation and anion. Copper(I) and triflate ions are disordered above and below the average plane of the four tellurium atoms, the anions are additionally disordered in two distinct orientations. Any vacancies in the structure are occupied by the solvent and the crystal can grow with significant ion depletion. The same issue was previously observed in the crystal of [Pd(1b4)](BF4)2, which features similar packing (I41/a; α, β, γ = 90°; a = 11.2576(14), b = 11.2576(14), c = 40.011(5) Å).47 Crystals grown from Cu(CF3SO3)·CH3C6H5 displayed metal occupancy close to 100%; but the degree of disorder precluded full refinement of the structure. The best results were achieved from crystals grown using [Cu(CH3CN)4](CF3SO3), which featured 60% depletion of copper. In that case, a satisfactory refinement with reasonable precision was completed by isotropically modelling atoms in the triflate anion and applying a solvent mask. Selected distances and angles from the final refinement are compiled in Table 2. The observed Te–Cu bond distances (2.645(2) and 2.705(2) Å) are longer than those observed in 356 (Scheme 2) and 457 (2.5299(8), 2.5598(7) and 2.587(2), 2.596(2) Å, respectively). However, those are tetrahedral complexes, there are no reported pentacoordinated κ4Te,κ1O species for a direct comparison. The Cu–O distance (2.249(8) Å) is shorter than observed in compounds such as [Cu(1,5,9,13-tetraselenacyclohexadecane)(SO3CF3)2] (2.464(5) Å). The base of the pyramid is slightly distorted, with Te–Cu–Tetrans angles of 148.3(3) and 159.1(3)°, the tellurium atoms deviate 0.131 Å from the average Te4 plane. The metal ion sits 0.609 Å from said plane. In spite of the symmetric inequivalence observed in the crystal structure, the NMR spectra display the patterns of only one iso-tellurazole, which indicates that in solution either the anion dissociates from the complex or the macrocycle undergoes a fast conformational exchange.
image file: c9nj02217a-f1.tif
Fig. 1 Molecular structure in the crystal of [Cu0.4(1b4)(CF3SO3)0.4]. Hydrogen atoms and solvent molecules, are omitted for clarity; displacement ellipsoids calculated at 75%.

image file: c9nj02217a-s2.tif
Scheme 2 Copper(I) and silver(I) complexes of telluroethers.
Gold(I). The reaction of 1b with [AuCl(C4H8S)] produced a crystalline compound with a structure that belongs to the P[1 with combining macron] space group. Here, 1b is also aggregated in 1b4 tetramers, but in a new conformation that features two neighboring tellurazole heterocycles pointing above and the other two pointing below the average plane of the tellurium atoms; further, this is a binuclear complex (Fig. 2). The unit cell contains two crystallographically independent molecules that sit in −1 special positions and display small structural differences (Fig. S1, ESI†). Selected bond distances and angles are provided in Table 2. The gold(I) ions are placed at either side of the macrocycle and each is bound to one tellurium atom (dAu–Te = 2.5233(7), 2.5116(7) Å) and one chloride anion (dAu–Cl = 2.305(2), 2.295(2) Å) with a linear coordination geometry (θTe–Au–Cl = 177.56(5), 177.29(6)°). The lengths of the Te–Au bonds are comparable to those measured for the linear complexes [Au(CF3Te)2]− (2.549(1), 2.533(1) Å)58 and [Au(TeSiMe3)(PPh3)] (2.5663(8) Å).59 The long intramolecular gold–gold distances (4.1806(8), 3.9507(7)) rule out aurophilic interactions but each gold ion is engaged in a short interaction (dAu–Te* = 3.5670(8), 3.5712(8) Å; cf. ∑rvdW = 4.44 Å) with a second tellurium atom in the macrocycle, nearly perpendicular to the Au–Cl axis (θTe–Au⋯Te = 83.38(2), 78.24(2)°). Although Au(I) can be a halogen bond acceptor,60 in the present case the orientation of the atoms is not consistent with chalcogen bonding. The Au⋯Te axis is nearly perpendicular to the relevant TeNC3 plane (θN–Te–Au = 84.5(2), 102.5(2)°; θC–Te–Au = 78.1(2), 100.3(2)°). The 1H NMR spectrum displays broad resonances at room temperature, which suggest that a dynamic process takes place in solution. Unfortunately, this process could not be better characterized due to the limited solubility and sensitivity of the compound to air and light.
image file: c9nj02217a-f2.tif
Fig. 2 Two perspectives of the molecular structure in the crystal of [Au2Cl2(1b4)]. Hydrogen atoms, are omitted for clarity; displacement ellipsoids calculated at 75%.
Silver(I). The reaction of Ag(CF3SO3) with the ligand 1c yielded crystals with a structure that belongs to the P[1 with combining macron] space group and contains the first example of a coordination complex of a hexamer of iso-tellurazole oxide (Fig. 3). The molecular structure features exocyclic κ1Te coordination of two metal ions and κ2Te endocyclic coordination of additional two silver cations. The overall composition of the complex, {[Ag2(μ-CF3SO3)2(1c6)]Ag2(CF3SO3)2}, includes triflate anions coordinated to the metal ions. The endocyclic ions are chelated by the tellurium atoms of two neighboring iso-tellurazole rings, and are O-bridged by two triflate anions. Bonds distances (dTe–Ag = 2.7871(5) and 2.7429(5) Å; dO–Ag = 2.404(4) and 2.352(4) Å) are within typical ranges. The coordination geometry deviates from tetrahedral, as shown by the Te–Ag–Te (92.15(2)°) and O–Ag–O (81.8(1)°) bond angles and the (Te–Ag–Te)–(O–Ag–O) interplanar angle (80.7°). This structural motif resembles the arrangement in 5,61 but in that case the Te–Ag–Te angle is much wider (130.72(2)°) and the O–Ag–O angle narrower (55.7(7)°). The AgTe2NO chelate ring is puckered, the Te–N–O⋯Te torsion angle is (43.5(5)°). The exocyclic silver ions are bound to antipodal tellurium atoms (dTe–Ag = 2.7008(5) Å), to triflate anions (dO–Ag = 2.266(5) Å) and to a carbon atom of the R aromatic group (dC–Ag = 2.548(5) Å). The trigonal planar coordination geometry is understandable in the case of this sterically hindered ligand (∑θE–Ag–E′ = 354.7°). Crystallization attempts in analogous conditions with 1b yielded a second example of this polynuclear complex. However, in this case, the space group is R[3 with combining macron] and the molecule is disordered in three orientations (Fig. S2, ESI†) with equal populations; this and crystallization-solvent disorder limit the precision of the structural determination. Refinement attempts in less symmetric space groups such as P[1 with combining macron] did not improve the quality of the model. The 1H and 13C NMR spectra measured for these compounds at room temperature is much simpler than expected from the molecular structures. For the complex of 1c in CD2Cl2, the observed patterns correspond to two iso-tellurazole N-oxides in 2[thin space (1/6-em)]:[thin space (1/6-em)]1 ratio; for the product of 1b in CD3CN, only one iso-tellurazole N-oxide pattern is observed. Whether conformational changes or partial dissociation are responsible remains uncertain as the sensitivity of the compounds frustrated further spectroscopic experiments. However, the insolubility of pure 1b in acetonitrile, and comparison with the spectra of pure 1c in CD2Cl2 rule out complete dissociation.
image file: c9nj02217a-f3.tif
Fig. 3 Molecular structure in the crystal of the complex {[Ag2(μ-CF3SO3)2(1c6)]Ag2(CF3SO3)2}. Hydrogen atoms, are omitted for clarity; displacement ellipsoids calculated at 75%.

Conclusions

These investigations do confirm that the annular aggregates of iso-tellurazole N-oxides are viable all-tellurium macrocyclic ligands for transition metal ions, even in the absence of favourable ligand field effects. A remarkable variety of structures was found with the complexes of copper, silver and gold monocations. All previous examples with Pd(II), Pt(II), and Rh(III) as well as the Cu(I) and Au(I) complexes feature the metal ion at the centre of the tetramer of iso-tellurazole N-oxide. As shown before by the Rh(III) complex and now by the Cu(I) derivative, this macrocycle allows additional ligands to bind the metal at either side of the Te4 plane to form penta- and hexacoordinated complexes. Being the largest cation in the series, Au(I) prefers an exocyclic linear coordination and a binuclear complex is formed with the metal ions bound to one tellurium atom each. Most noteworthy is the structure of the Ag(I) complexes, which are the first examples of hexamers as ligands and feature two endocyclic and two exocyclic ions. The isolation of two isostructural examples with ligands of different solubilties indicates that their structure is selected by the metal ion, not the solubility of the complex and its packing in the lattice. The structural diversity observed in the metal complexes of iso-tellurazole N-oxides stems from the conformational flexibility and the tetramer–hexamer equilibrium previously observed in the free macrocyclic aggregates. These findings indicate that achieving precise control of the structure of the coordination compounds of these ligands will be challenging.

Conflicts of interest

There are no conflicts to declare.

Acknowledgements

We gratefully acknowledge funding from the Natural Sciences and Engineering Research Council of Canada (NSERC).

References

  1. A. Panda, Coord. Chem. Rev., 2009, 253, 1056–1098 CrossRef CAS .
  2. A. Panda, Coord. Chem. Rev., 2009, 253, 1947–1965 CrossRef CAS .
  3. Y.-P. Chang, W. Levason and G. Reid, Dalton Trans., 2016, 45, 18393–18416 RSC .
  4. R. J. Batchelor, F. W. Einstein, I. D. Gay, J. Gu, B. D. Johnston and M. B. Pinto, J. Am. Chem. Soc., 1989, 111, 6582–6591 CrossRef CAS .
  5. R. J. Batchelor, F. W. Einstein, I. D. Gay, J. Gu, M. B. Pinto and X. Zhou, Inorg. Chem., 1996, 35, 3667–3674 CrossRef CAS .
  6. W. Levason, J. M. Manning, P. Pawelzyk and G. Reid, Eur. J. Inorg. Chem., 2006, 4380–4390 CrossRef CAS .
  7. R. D. Adams, K. T. McBride and R. D. Rogers, Organometallics, 1997, 16, 3895–3901 CrossRef CAS .
  8. T. Shimizu, M. Kawaguchi, T. Tsuchiya, K. Hirabayashi and N. Kamigata, Org. Lett., 2003, 5, 1443–1445 CrossRef CAS PubMed .
  9. T. Shimizu, M. Kawaguchi, T. Tsuchiya, K. Hirabayashi and N. Kamigata, J. Org. Chem., 2005, 70, 5036–5044 CrossRef CAS PubMed .
  10. W. Levason, J. M. Manning, G. Reid, M. Tuggey and M. Webster, Dalton Trans., 2009, 4569–4577 RSC .
  11. A. J. Barton, N. J. Hill, W. Levason and G. Reid, J. Am. Chem. Soc., 2001, 123, 11801–11802 CrossRef CAS PubMed .
  12. N. J. Hill, W. Levason and G. Reid, Inorg. Chem., 2002, 41, 2070–2076 CrossRef CAS PubMed .
  13. J. Y. Lim, I. Marques, A. L. Thompson, K. E. Christensen, V. Félix and P. D. Beer, J. Am. Chem. Soc., 2017, 139, 3122–3133 CrossRef CAS PubMed .
  14. E. G. Hope, T. Kemmitt and W. Levason, Organometallics, 1987, 6, 206–207 CrossRef CAS .
  15. H. Fujihara, T. Ninoi, R. Akaishi, T. Erata and N. Furukawa, Tetrahedron Lett., 1991, 32, 4537–4540 CrossRef CAS .
  16. Y. Takaguchi, E. Horn and N. Furukawa, Organometallics, 1996, 15, 5112–5115 CrossRef CAS .
  17. M. J. Champion, W. Levason, D. Pugh and G. Reid, Dalton Trans., 2015, 44, 18748–18759 RSC .
  18. W. Levason, D. Pugh, J. M. Purkis and G. Reid, Dalton Trans., 2016, 45, 7900–7911 RSC .
  19. M. J. Hesford, W. Levason, M. L. Matthews and G. Reid, Dalton Trans., 2003, 2852–2858 RSC .
  20. A. Panda, S. C. Menon, H. B. Singh, C. P. Morley, R. Bachman, M. T. Cocker and R. J. Butcher, Eur. J. Inorg. Chem., 2005, 1114–1126 CrossRef CAS .
  21. W. Levason, J. M. Manning, M. Nirwan, R. Ratnani, G. Reid, H. L. Smith and M. Webster, Dalton Trans., 2008, 3486–3492 RSC .
  22. C. Bornet, R. Amardeil, P. Meunier and J. Daran, J. Chem. Soc., Dalton Trans., 1999, 1039–1040 RSC .
  23. P. Farina, T. Latter, W. Levason and G. Reid, Dalton Trans., 2013, 42, 4714–4724 RSC .
  24. P. Farina, W. Levason and G. Reid, Polyhedron, 2013, 55, 102–108 CrossRef CAS .
  25. C. Beattie, P. Farina, W. Levason and G. Reid, Dalton Trans., 2013, 42, 15183–15190 RSC .
  26. M. J. Champion, P. Farina, W. Levason and G. Reid, Dalton Trans., 2013, 42, 13179–13189 RSC .
  27. W. Levason, S. D. Orchard and G. Reid, Chem. Commun., 2001, 427–428 RSC .
  28. M. J. Hesford, W. Levason, M. L. Matthews, S. D. Orchard and G. Reid, Dalton Trans., 2003, 2434–2442 RSC .
  29. U. Patel, H. B. Singh and R. J. Butcher, Eur. J. Inorg. Chem., 2006, 5089–5097 CrossRef CAS .
  30. S. Panda, S. S. Zade, H. B. Singh and R. J. Butcher, Eur. J. Inorg. Chem., 2006, 172–184 CrossRef CAS .
  31. S. C. Menon, A. Panda, H. B. Singh and R. J. Butcher, Chem. Commun., 2000, 143–144 RSC .
  32. S. Panda, H. B. Singh and R. J. Butcher, Chem. Commun., 2004, 322–323 RSC .
  33. S. C. Menon, A. Panda, H. B. Singh, R. P. Patel, S. K. Kulshreshtha, W. L. Darby and R. J. Butcher, J. Organomet. Chem., 2004, 689, 1452–1463 CrossRef CAS .
  34. A. Alka, V. S. Shetti and M. Ravikanth, Dalton Trans., 2019, 48, 4444–4459 RSC .
  35. E. Pacholska-Dudziak, L. Szterenberg and L. Latos-Grażyński, Chem. – Eur. J., 2011, 17, 3500–3511 CrossRef CAS PubMed .
  36. B. Sathyamoorthy, A. Axelrod, V. Farwell, S. M. Bennett, B. D. Calitree, J. B. Benedict, D. K. Sukumaran and M. R. Detty, Organometallics, 2010, 29, 3431 CrossRef CAS .
  37. E. Pacholska-Dudziak, F. Ulatowski, Z. Ciunik and L. Latos-Grażyński, Chem. – Eur. J., 2009, 15, 10924–10929 CrossRef CAS PubMed .
  38. M. Abe, M. R. Detty, O. O. Gerlits and D. K. Sukumaran, Organometallics, 2004, 23, 4513 CrossRef CAS .
  39. M. Abe, D. G. Hilmey, C. E. Stilts, D. K. Sukumaran and M. R. Detty, Organometallics, 2002, 21, 2986 CrossRef CAS .
  40. E. Pacholska, L. Latos-Grażyński and Z. Ciunik, Chem. – Eur. J., 2002, 8, 5403–5405 CrossRef CAS .
  41. L. Latos-Grażyński, E. Pacholska, P. J. Chmielewski, M. M. Olmstead and A. L. Balch, Angew. Chem., Int. Ed. Engl., 1995, 34, 2252–2254 CrossRef .
  42. E. Pacholska-Dudziak, M. Szczepaniak, A. Książek and L. Latos-Grażyński, Angew. Chem., 2013, 125, 9066–9071 CrossRef .
  43. S. Kumar, W.-Z. Lee and M. Ravikanth, Org. Lett., 2018, 20, 636–639 CrossRef CAS PubMed .
  44. M. Oba, K. Nishiyama, S. Koguchi, S. Shimada and W. Ando, Organometallics, 2013, 32, 6620–6623 CrossRef CAS .
  45. K. Kobayashi, H. Izawa, K. Yamaguchi, E. Horn and N. Furukawa, Chem. Commun., 2001, 1428–1429 RSC .
  46. J. Kübel, P. J. Elder, H. A. Jenkins and I. Vargas-Baca, Dalton Trans., 2010, 39, 11126–11128 RSC .
  47. P. C. Ho, P. Szydlowski, J. Sinclair, P. J. Elder, J. Kübel, C. Gendy, L. Lee, H. Jenkins, J. F. Britten, D. R. Morim and I. Vargas-Baca, Nat. Commun., 2016, 7, 11299 CrossRef CAS .
  48. P. C. Ho, J. Rafique, J. Lee, L. M. Lee, H. A. Jenkins, J. F. Britten, A. L. Braga and I. Vargas-Baca, Dalton Trans., 2017, 46, 6570–6579 RSC .
  49. P. Ho, R. Bui, A. Cevallos, S. Sequeira, J. F. Britten and I. Vargas-Baca, Dalton Trans., 2019, 48, 4879–4886 RSC .
  50. P. C. Ho, L. Lee, H. Jenkins, J. F. Britten and I. Vargas-Baca, Can. J. Chem., 2016, 94, 453–457 CrossRef CAS .
  51. R. Uson, A. Laguna, M. Laguna, D. Briggs, H. Murray and J. Fackler, Inorg. Synth., 2007, 26, 85–91 CrossRef .
  52. Bruker, SAINT, Bruker AXS Inc., Madison, Wisconsin, USA, 2012 Search PubMed .
  53. Bruker, SADABS, Bruker AXS Inc., Madison, Wisconsin, USA, 2001 Search PubMed .
  54. G. Sheldrick, Acta Crystallogr., Sect. C: Struct. Chem., 2015, 71, 3–8 CrossRef PubMed .
  55. B. Rees, L. Jenner and M. Yusupov, Acta Crystallogr., Sect. D: Biol. Crystallogr., 2005, 61, 1299–1301 CrossRef PubMed .
  56. J. R. Black, N. R. Champness, W. Levason and G. Reid, Inorg. Chem., 1996, 35, 1820–1824 CrossRef CAS .
  57. W. Levason, G. Reid and V.-A. Tolhurst, J. Chem. Soc., Dalton Trans., 1998, 3411–3416 RSC .
  58. N. V. Kirij, W. Tyrra, D. Naumann, Y. L. Yagupolskii, I. Pantenburg and M. Schäfer, J. Fluorine Chem., 2004, 125, 1933–1938 CrossRef CAS .
  59. P. J. Bonasia, D. E. Gindelberger and J. Arnold, Inorg. Chem., 1993, 32, 5126–5131 CrossRef CAS .
  60. F. Groenewald, J. Dillen and C. Esterhuysen, New J. Chem., 2018, 42, 10529–10538 RSC .
  61. M. J. Poropudas, L. Vigo, R. Oilunkaniemi and R. S. Laitinen, Dalton Trans., 2013, 42, 16868–16877 RSC .

Footnote

† Electronic supplementary information (ESI) available: Structural comparison of the two molecular units in the crystal of [Au2Cl2(1b4)], 1H and 13C NMR spectra. CCDC 1894241, 1894242, 1894244 and 1894691. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c9nj02217a
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