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The title compound, C8H4ClNO2Te, represents the first reported example of a benzofuran-derived 2,1,3-benzoxa­tellurazole derivative. While it can be formally described as a nitroso­aryl­tellurium monochloride, its Te-O and Te-C bond lengths of 2.1421 (14) and 2.0374 (17) Å, respectively, characterize it as a planar tricyclic aromatic containing a Te=C double bond. Its formation suggests that derivatives of 2-cyclo­hexenone oxime in general react with tellurium dioxide to form aryl-2,1,3-benzoxatellurazoles.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270112050196/eg3105sup1.cif
Contains datablocks I, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270112050196/eg3105Isup2.hkl
Contains datablock I

CCDC reference: 925764

Comment top

Reports of oxatellurazole derivatives have been limited to a very few members, namely 3-chloro-3H-naphth[2,1-c][1,2,5]oxatellurazole and related compounds, and 1-chloro-5,6-dimethoxy-1H-2,1,3-benzoxatellurazole 3-oxide cited in the patent literature (Gunther, 1987; Gunther & Lock, 1986; Przyklek-Elling et al., 1987). Furthermore, the structure of 1-bromo-4,6-dimethyl-1H-2,1,3-benzoxatellurazole was reported more recently (Mallikaratchy et al., 2003). The title compound, (I) (Fig. 1), was prepared by reacting 4-oxo-4,5,6,7-tetrahydrobenzofuran with hydroxylamine hydrochloride and tellurium dioxide in the presence of lithium chloride (see scheme). It represents the first reported example of a benzofuran-derived tricyclic benzoxatellurazole derivative. It is highly probable that the initial reaction product is an oxime, which condenses with tellurium dioxide by undergoing aromatization of the central ring. In the past, claims had appeared in the patent literature reporting the condensation of tellurium dioxide and α-tetralone oxime or acenaphthylen-1-one oxime to the corresponding oxatellurazole derivatives (Gunther & Lock, 1986), but the scope of this reaction has remained unclear. The data presented here suggest that α,β-unsaturated cyclohexenones in general are capable of condensing to 2,1,3-oxatellurazole derivatives. Formally, 2,1,3-benzoxatellurazoles can be described as 2-nitrosoaryltellurium monohalides (see scheme). The purpose of this study was the structural characterization of these compounds in an effort to evaluate whether they are indeed cyclic and what their degree of planarity is, and consequently to establish the appropriate formal naming (halo-oxatellurazole versus nitrosoaryltellurium halide). The structural parameters of very few 1,2,5-oxatellurazoles have been published, making generalized statements regarding their structures problematic. These compounds have potential as intermediates for other organotellurium heterocycles.

The geometry of (I) is T-shaped about the Te atom, with an O—Te—Cl angle of 169.62 (4)°, distinctly nonlinear. This can be attributed to the presence of two lone pairs on the TeII center, as well as ring strain evidenced by the fact that the C—Te—Cl angle is more than 15° larger than the C1—Te—O angle. This value is very similar to those of 169.6 and 160.8°, respectively, reported for 1-bromo-4,6-dimethyl-1H-2,1,3-benzoxatellurazole and 1-bromo-4,6-dimethyl-1H-2,1,3-benzoxatellurazole 3-oxide (Mallikaratchy et al., 2003). The Te—O bond length of 2.1421 (14) Å in (I) is in good agreement with that of 2.165 Å reported for the former. The Te—C distance of 2.0374 (17) Å in (I) is considerably shorter than those found for coordination-stabilized aryl tellurenyl monohalides (Detty & O'Regan, 1994), but similar to 2.043 Å reported for 2,5-diphenyl-1,6-dioxa-6a-tellurapentalene, a structurally related molecule containing a Te—C double bond (Detty & Luss, 1983). Similarly, the Te—O bond lengths of (I) and the aforementioned tellurapentalene derivative (Te—O = 2.13 Å) are nearly identical. A best-plane calculation carried out for the C8TeNO2 component of (I) found deviations from planarity of less than 0.03 Å for these atoms. The chloride substituent deviates from this plane by 0.137 (2) Å.

Pairs of molecules of I) are stacked such that they are related by an inversion center at (1/2, 1/2, 1/2), with C2···C7i = 3.319 (2) Å [symmetry code: (i) -x + 1, -y + 1, -z + 1].

Related literature top

For related literature, see: Detty & Luss (1983); Detty & O'Regan (1994); Gunther (1987); Gunther & Lock (1986); Mallikaratchy et al. (2003); Matsumoto & Watanabe (1985); Przyklek-Elling, Lok & Gunther (1987).

Experimental top

A 50 ml round-bottomed flask equipped with a magnetic stirrer and a reflux condenser was charged with 4-oxo-4,5,6,7-tetrahydrobenzofuran (1.00 g, 7.3 mmol) prepared according to the literature method of Matsumoto & Watanabe (1985), tellurium dioxide (1.16 g, 7.3 mmol), hydroxylamine hydrochloride (0.51 g, 7.3 mmol), lithium chloride (1.55 g, 36.6 mmol) and glacial acetic acid (10 ml). The mixture was stirred and heated to gentle reflux for 20 min. The resulting deep-purple solution was allowed to cool to room temperature then diluted with water (200 ml), and the precipitated solid was collected by filtration and washed with copious amounts of water. The filtrate was dried, placed into a beaker and extracted with 50 ml batches of warm tert-butyl methyl ether (MTBE) until the bulk of the purple product had been dissolved (approximately 250 ml used). The solution was purified by vacuum filtration and the solvent allowed to evaporate from an open beaker placed under the fume hood. The residue was chromatographed on silica gel (60–200 mesh, grade 62, GFS Chemicals), using hexane followed by MTBE as eluents. The blue–purple band was collected and the solvent removed by open-air evaporation. Well formed crystals of (I) were obtained by slow open-air evaporation of a concentrated solution in hot heptane. The product was intensely dark-blue–purple and nonpolar in nature (yield 430 mg, 18.9%; decomposition >453 K). Spectroscopic analysis: 1H NMR (CDCl3, δ, p.p.m.): 7.77 (multiplet, 1H), 8.03 (doublet, 1H), 8.05 (multiplet, 1H), 8.67 (doublet, 1H); 13C NMR (CDCl3, δ, p.p.m.): 107.66, 120.17, 128.79, 129.65, 148.47, 155.64, 155.74, 163.23.

Refinement top

All H atoms were placed in idealized positions, guided by difference maps, with C—H = 0.95 Å and Uiso(H) = 1.2Ueq(C).

Computing details top

Data collection: COLLECT (Nonius, 1998); cell refinement: DENZO and SCALEPACK (Otwinowski & Minor, 1997); data reduction: DENZO and SCALEPACK (Otwinowski & Minor, 1997); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. The molecular structure of (I), showing the atom-labeling scheme. Displacement ellipsoids are shown at the 50% probability level.
1-Chlorofuro[3,2-e][2,1,3]benzoxatellurazole top
Crystal data top
C8H4ClNO2TeF(000) = 576
Mr = 309.17Dx = 2.364 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 3941 reflections
a = 9.9504 (15) Åθ = 2.5–34.9°
b = 8.8490 (14) ŵ = 3.69 mm1
c = 10.0077 (16) ÅT = 90 K
β = 99.731 (9)°Fragment, dark purple–blue
V = 868.5 (2) Å30.23 × 0.10 × 0.10 mm
Z = 4
Data collection top
Nonius KappaCCD area-detector
diffractometer
3795 independent reflections
Radiation source: fine-focus sealed tube3405 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.019
ω and ϕ scansθmax = 34.9°, θmin = 3.0°
Absorption correction: multi-scan
(DENZO and SCALEPACK; Otwinowski & Minor, 1997)
h = 1515
Tmin = 0.484, Tmax = 0.709k = 1414
21379 measured reflectionsl = 1616
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.024H-atom parameters constrained
wR(F2) = 0.055 w = 1/[σ2(Fo2) + (0.019P)2 + 1.1492P]
where P = (Fo2 + 2Fc2)/3
S = 1.05(Δ/σ)max = 0.002
3795 reflectionsΔρmax = 1.28 e Å3
119 parametersΔρmin = 1.07 e Å3
0 restraintsExtinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.0019 (2)
Crystal data top
C8H4ClNO2TeV = 868.5 (2) Å3
Mr = 309.17Z = 4
Monoclinic, P21/cMo Kα radiation
a = 9.9504 (15) ŵ = 3.69 mm1
b = 8.8490 (14) ÅT = 90 K
c = 10.0077 (16) Å0.23 × 0.10 × 0.10 mm
β = 99.731 (9)°
Data collection top
Nonius KappaCCD area-detector
diffractometer
3795 independent reflections
Absorption correction: multi-scan
(DENZO and SCALEPACK; Otwinowski & Minor, 1997)
3405 reflections with I > 2σ(I)
Tmin = 0.484, Tmax = 0.709Rint = 0.019
21379 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0240 restraints
wR(F2) = 0.055H-atom parameters constrained
S = 1.05Δρmax = 1.28 e Å3
3795 reflectionsΔρmin = 1.07 e Å3
119 parameters
Special details top

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Te10.194204 (12)0.141192 (13)0.517777 (12)0.01443 (4)
Cl10.02661 (5)0.16185 (5)0.67853 (5)0.01845 (8)
O10.33675 (15)0.16734 (15)0.38122 (15)0.0180 (3)
O20.32249 (14)0.81368 (16)0.46146 (15)0.0180 (2)
N10.37143 (16)0.30684 (18)0.35571 (16)0.0161 (3)
C10.22229 (18)0.36919 (19)0.51573 (17)0.0131 (3)
C20.31289 (17)0.41136 (19)0.42512 (17)0.0125 (3)
C30.34183 (17)0.5671 (2)0.40939 (17)0.0131 (3)
C40.28249 (18)0.6700 (2)0.48623 (18)0.0143 (3)
C50.19367 (18)0.6319 (2)0.57587 (19)0.0153 (3)
H50.15540.70740.62550.018*
C60.16359 (17)0.4799 (2)0.58966 (18)0.0145 (3)
H60.10330.45040.64910.017*
C70.42279 (19)0.6535 (2)0.33147 (19)0.0157 (3)
H70.47620.61620.26850.019*
C80.40701 (19)0.7999 (2)0.3667 (2)0.0178 (3)
H80.44930.88300.33020.021*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Te10.01624 (6)0.01189 (5)0.01659 (6)0.00241 (4)0.00689 (4)0.00068 (4)
Cl10.01650 (18)0.02040 (19)0.02034 (19)0.00364 (14)0.00857 (15)0.00200 (15)
O10.0229 (6)0.0118 (5)0.0217 (6)0.0015 (5)0.0104 (5)0.0024 (5)
O20.0180 (6)0.0122 (5)0.0259 (7)0.0000 (5)0.0099 (5)0.0014 (5)
N10.0176 (6)0.0149 (6)0.0172 (7)0.0004 (5)0.0074 (5)0.0022 (5)
C10.0126 (6)0.0133 (7)0.0140 (7)0.0012 (5)0.0039 (5)0.0002 (5)
C20.0126 (6)0.0127 (6)0.0134 (7)0.0002 (5)0.0052 (5)0.0005 (5)
C30.0118 (6)0.0129 (7)0.0157 (7)0.0004 (5)0.0055 (5)0.0009 (5)
C40.0135 (7)0.0115 (6)0.0189 (7)0.0001 (5)0.0059 (6)0.0012 (5)
C50.0149 (7)0.0142 (7)0.0185 (8)0.0010 (6)0.0074 (6)0.0019 (6)
C60.0138 (7)0.0154 (7)0.0156 (7)0.0003 (5)0.0064 (6)0.0005 (6)
C70.0163 (7)0.0157 (8)0.0170 (7)0.0007 (6)0.0084 (6)0.0025 (6)
C80.0180 (7)0.0153 (7)0.0218 (8)0.0013 (6)0.0083 (6)0.0045 (6)
Geometric parameters (Å, º) top
Te1—C12.0374 (17)C3—C41.387 (2)
Te1—O12.1421 (14)C3—C71.433 (2)
Te1—Cl12.5119 (6)C4—C51.403 (2)
O1—N11.318 (2)C5—C61.389 (3)
O2—C41.367 (2)C5—H50.9500
O2—C81.375 (2)C6—H60.9500
N1—C21.347 (2)C7—C81.359 (3)
C1—C61.413 (2)C7—H70.9500
C1—C21.432 (2)C8—H80.9500
C2—C31.422 (2)
C1—Te1—O177.28 (6)O2—C4—C3110.24 (15)
C1—Te1—Cl192.37 (5)O2—C4—C5125.01 (16)
O1—Te1—Cl1169.62 (4)C3—C4—C5124.75 (16)
N1—O1—Te1116.61 (11)C6—C5—C4117.77 (16)
C4—O2—C8105.87 (15)C6—C5—H5121.1
O1—N1—C2113.14 (15)C4—C5—H5121.1
C6—C1—C2120.74 (16)C5—C6—C1120.28 (16)
C6—C1—Te1127.75 (13)C5—C6—H6119.9
C2—C1—Te1111.50 (12)C1—C6—H6119.9
N1—C2—C3119.68 (15)C8—C7—C3105.49 (16)
N1—C2—C1121.40 (16)C8—C7—H7127.3
C3—C2—C1118.92 (15)C3—C7—H7127.3
C4—C3—C2117.51 (15)C7—C8—O2111.98 (16)
C4—C3—C7106.42 (15)C7—C8—H8124.0
C2—C3—C7136.06 (16)O2—C8—H8124.0
C1—Te1—O1—N12.25 (13)C1—C2—C3—C7179.47 (19)
Cl1—Te1—O1—N12.3 (3)C8—O2—C4—C30.6 (2)
Te1—O1—N1—C22.0 (2)C8—O2—C4—C5179.12 (17)
O1—Te1—C1—C6178.62 (17)C2—C3—C4—O2178.77 (15)
Cl1—Te1—C1—C62.20 (15)C7—C3—C4—O20.5 (2)
O1—Te1—C1—C21.86 (11)C2—C3—C4—C51.5 (3)
Cl1—Te1—C1—C2177.32 (11)C7—C3—C4—C5179.22 (17)
O1—N1—C2—C3179.27 (16)O2—C4—C5—C6179.83 (17)
O1—N1—C2—C10.3 (2)C3—C4—C5—C60.5 (3)
C6—C1—C2—N1178.86 (16)C4—C5—C6—C10.4 (3)
Te1—C1—C2—N11.6 (2)C2—C1—C6—C50.3 (3)
C6—C1—C2—C30.7 (2)Te1—C1—C6—C5179.80 (14)
Te1—C1—C2—C3178.85 (13)C4—C3—C7—C80.2 (2)
N1—C2—C3—C4178.01 (16)C2—C3—C7—C8178.9 (2)
C1—C2—C3—C41.6 (2)C3—C7—C8—O20.2 (2)
N1—C2—C3—C71.0 (3)C4—O2—C8—C70.5 (2)

Experimental details

Crystal data
Chemical formulaC8H4ClNO2Te
Mr309.17
Crystal system, space groupMonoclinic, P21/c
Temperature (K)90
a, b, c (Å)9.9504 (15), 8.8490 (14), 10.0077 (16)
β (°) 99.731 (9)
V3)868.5 (2)
Z4
Radiation typeMo Kα
µ (mm1)3.69
Crystal size (mm)0.23 × 0.10 × 0.10
Data collection
DiffractometerNonius KappaCCD area-detector
diffractometer
Absorption correctionMulti-scan
(DENZO and SCALEPACK; Otwinowski & Minor, 1997)
Tmin, Tmax0.484, 0.709
No. of measured, independent and
observed [I > 2σ(I)] reflections
21379, 3795, 3405
Rint0.019
(sin θ/λ)max1)0.806
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.024, 0.055, 1.05
No. of reflections3795
No. of parameters119
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)1.28, 1.07

Computer programs: COLLECT (Nonius, 1998), DENZO and SCALEPACK (Otwinowski & Minor, 1997), SIR97 (Altomare et al., 1999), SHELXL97 (Sheldrick, 2008), ORTEP-3 for Windows (Farrugia, 1997).

Selected geometric parameters (Å, º) top
Te1—C12.0374 (17)O1—N11.318 (2)
Te1—O12.1421 (14)N1—C21.347 (2)
Te1—Cl12.5119 (6)
C1—Te1—O177.28 (6)O1—N1—C2113.14 (15)
C1—Te1—Cl192.37 (5)C6—C1—Te1127.75 (13)
O1—Te1—Cl1169.62 (4)C2—C1—Te1111.50 (12)
N1—O1—Te1116.61 (11)
 

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