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Bis(2,6-di­methyl­pyrid­yl)iodonium di­bromo­iodate

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aDepartment of Chemistry, University of Durham, South Road, Durham DH1 3LE, England, and bGlaxoSmithKline Pharmaceuticals, New Frontiers Science Park, Third Avenue, Harlow, Essex, CM19 5AW, England
*Correspondence e-mail: andy.whiting@durham.ac.uk

(Received 27 January 2006; accepted 30 January 2006; online 3 February 2006)

The crystal structure of the title compound, C14H18IN2+·Br2I, isostructural with the Cl2I analogue, comprises discrete centrosymmetric cations and anions, both with linear coordination of the I atoms.

Comment

Electropositive sources of iodine are useful reagents for the iodo­deboronation of alkenylboronate derivatives (Brown et al., 1973[Brown H. C., Hamaoka T. & Ravindran N. (1973). J. Am. Chem. Soc. 95, 5786-5788.]). Iodine monochloride is an important representative of such reagents (Stewart & Whiting, 1995[Stewart, S. K. & Whiting A. (1995). Tetrahedron Lett. 36, 3929-3932.]; Lightfoot et al., 2004[Lightfoot, A. P., Twiddle, S. J. R. & Whiting, A. (2004). Tetrahedron Lett. 45, 8557-8561.]), but its shortcomings concerning reactivity, stereocontrol and chemoselectivity necessitated the development of adjusted reagents involving amine–ICl complexes (Batsanov et al., 2005[Batsanov, A. S., Howard, J. A. K., Lightfoot, A. P., Twiddle, S. J. R. & Whiting, A. (2005). Eur. J. Org. Chem. pp. 1876-1883.]). In the course of the latter work, we obtained bis­(2,6-dimethyl­pyrid­yl)iodonium dichloro­iodate (I), the crystal structure of which unexpectedly comprised discrete I(NC7H9)2+ and ICl2 ions rather than neutral Cl—I—NC7H9 mol­ecules (Batsanov et al., 2005[Batsanov, A. S., Howard, J. A. K., Lightfoot, A. P., Twiddle, S. J. R. & Whiting, A. (2005). Eur. J. Org. Chem. pp. 1876-1883.]), but which also proved to be active in iodo­deboronation. Continuing these studies, we have prepared the bromide analogue of compound (I), viz. I(NC7H9)2+·IBr2 (II)[link], which proved not to be superior to (I) as an iodo­deboronation agent.

[Scheme 1]

The crystals of (II)[link] are isomorphous with those of (I), with an increase of the volume per mol­ecule by 14 Å3, or ca 3%. The structure comprises discrete bis­(2,6-dimethyl­pyrid­yl)iodo­nium cations and IBr2 anions (Fig. 1[link]). In both ions, the central I atoms occupy special positions at inversion centres, hence the N—I1—N′ and Br—I2—Br′ angles exactly equal 180°.

Atom I1 is tilted out of the pyridine ring plane by 0.190 (5) Å, whereas atoms C1 and C7 deviate on the opposite side of the plane by 0.026 (6) and 0.080 (6) Å, respectively. Thus, the two rings of the cation are parallel but not coplanar, with an inter­planar separation of 0.38 Å, cf. 0.60 Å in (I). The I1—N bond distance of 2.294 (3) Å agrees with 2.300 (1) Å in (I), 2.259 (3) Å in bis­(pyridine)iodo­nium (Álvarez-Rúa et al., 2002[Álvarez-Rúa, C., García-Granda, S., Bellesteros, A., Gonzáles-Bobes, F. & Gonzáles, J. M. (2002). Acta Cryst. E58, o1381-o1383.]) and 2.29 (1) Å in bis­(2,4,6-collidine)iodo­nium (Brayer & James, 1982[Brayer, G. D. & James, M. N. G. (1982). Acta Cryst. B38, 654-657.]). All these distances are much longer than the single Nsp2—I bonds in N-iodo­succinimide [2.059 (4) Å; Padmanabhan et al., 1990[Padmanabhan, K., Paul, I. C. & Curtin, D. Y. (1990). Acta Cryst. C46, 88-92.]] or diiodo­formamide [mean 2.07 (3) Å; Pritzkow, 1974[Pritzkow, H. (1974). Monatsh. Chem. 105, 621-628.]] and can be regarded as hypervalent bonds. Likewise, the I2—Br bond length of 2.6962 (4) Å is normal for IBr2 anions in the solid state, cf. 2.710 (1) Å in [Me3S][IBr2] (Svensson & Kloo, 2000[Svensson, P. H. & Kloo, L. (2000). J. Chem. Soc. Dalton Trans. pp. 2449-2455.]), 2.709 (2) Å in [H2(pc)][IBr2] or 2.6986 (4) Å in [H2(pc)]2[IBr2]Br (pc is phthalocyanine; Gardberg et al., 2002[Gardberg, A. S., Yang, S., Hoffman, B. M. & Ibers, J. A. (2002). Inorg. Chem. 41, 1778-1781.]). However, these bonds also are much weaker than a single bond, as observed in the IBr mol­ecule in the gas phase (2.469 Å; Huber & Herzberg, 1979[Huber, K. P. & Herzberg, G. (1979). In Molecular Spectra and Molecular Structure, Vol. IV, Constants of Diatomic Molecules. New York: van Nostrand.]).

[Figure 1]
Figure 1
The cation and anion in (II)[link]. Atomic displacement ellipsoids are drawn at the 50% probability level. Br′ is generated by the symmetry operator (−x, −y, 1 − z), and the other primed atoms are generated by the symmetry operator (1 − x, 1 − y, 1 − z).

Experimental

A 1.0 M solution of IBr in dichloromethane (DCM; 30 mmol, 30 ml) was cooled to 273 K with stirring under argon prior to the dropwise addition of 2,6-lutidine (30 mmol, 3.50 ml). After 30 min, the reaction was allowed to warm to room temperature before the addition of hexane (40 ml) to induce precipitation of the product. Filtration, drying (MgSO4) and evaporation gave the product as an orange solid (7.37 g, 78%). IR νmax, cm−1: 2978, 1601, 1466, 1377, 1161 and 792. 1H NMR (400 MHz, CDCl3, δ, p.p.m.): 2.78 (6H, s, 2 × Me), 7.13 (2H, d, J = 7.6 Hz, Ar—H) and 7.62 (1H, t, J = 7.6 Hz, Ar—H). 13C NMR (100 MHz, CDCl3, δ, p.p.m.): 28.1 (Me), 123.0 (Ar), 139.2 (Ar) and 157.6 (Ar). (C7H9NIBr)2 requires: C 26.76, H 2.89, N 4.46%; found: C 26.22, H 2.88, N 4.28%. Single crystals of X-ray quality were obtained by slow evaporation of a solution in DCM–hexane (1:1). To test the deboronation properties of (II)[link], it has been reacted with 4,4,5,5-tetra­methyl-2-non-1-enyl-1,3,2-dioxaborolane and 4,4,6-trimethyl-2-non-1-enyl-1,3,2-dioxaborinane in DCM, yielding BrCH=CHC7H15 as the sole product and with complete selectivity for the Z-alkene in both cases. However, the maximum conversions achieved (47 and 52%, respectively) were low.

Crystal data
  • C14H18IN2+·Br2I

  • Mr = 627.92

  • Triclinic, [P \overline 1]

  • a = 7.5777 (7) Å

  • b = 8.2610 (7) Å

  • c = 8.5800 (7) Å

  • α = 99.09 (1)°

  • β = 101.45 (1)°

  • γ = 114.20 (1)°

  • V = 462.6 (1) Å3

  • Z = 1

  • Dx = 2.254 Mg m−3

  • Mo Kα radiation

  • Cell parameters from 3235 reflections

  • θ = 2.5–30.0°

  • μ = 7.71 mm−1

  • T = 120 (2) K

  • Block, orange

  • 0.10 × 0.08 × 0.02 mm

Data collection
  • Bruker SMART 6K CCD area-detector diffractometer

  • ω scans

  • Absorption correction: multi-scan(SADABS; Bruker, 2003[Bruker (2003). SADABS. Version 2.10. Bruker AXS Inc, Madison, Wisconsin, USA.])Tmin = 0.637, Tmax = 0.861

  • 6548 measured reflections

  • 2693 independent reflections

  • 2309 reflections with I > 2σ(I)

  • Rint = 0.037

  • θmax = 30.0°

  • h = −10 → 10

  • k = −11 → 11

  • l = −12 → 12

Refinement
  • Refinement on F2

  • R[F2 > 2σ(F2)] = 0.031

  • wR(F2) = 0.076

  • S = 0.99

  • 2693 reflections

  • 98 parameters

  • H-atom parameters constrained

  • w = 1/[σ2(Fo2) + (0.0387P)2] where P = (Fo2 + 2Fc2)/3

  • (Δ/σ)max < 0.001

  • Δρmax = 2.54 e Å−3

  • Δρmin = −1.41 e Å−3

Methyl groups were treated as rigid bodies (C—H = 0.98 Å) rotating around the C—C bonds, with a common refined Uiso value for three H atoms. Aromatic H atoms were treated as riding on the C atoms [C—H = 0.95 Å and Uiso(H) = 1.2Ueq(C)]. The five strongest maxima and minima of the final difference map are located at distances of 0.8–0.9 Å from atoms I1 and I2.

Data collection: SMART (Bruker, 2001[Bruker (2001). SMART (Version 5.625), SAINT (Version 6.02A) and SHELXTL (Version 6.12). Bruker AXS Inc, Madison, Wisconsin, USA.]); cell refinement: SAINT (Bruker, 2001[Bruker (2001). SMART (Version 5.625), SAINT (Version 6.02A) and SHELXTL (Version 6.12). Bruker AXS Inc, Madison, Wisconsin, USA.]); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Bruker, 2001[Bruker (2001). SMART (Version 5.625), SAINT (Version 6.02A) and SHELXTL (Version 6.12). Bruker AXS Inc, Madison, Wisconsin, USA.]); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Supporting information


Computing details top

Data collection: SMART (Bruker, 2001); cell refinement: SMART; data reduction: SAINT (Bruker, 2001); program(s) used to solve structure: SHELXTL (Bruker, 2001); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Bis(2,6-dimethylpyridyl)iodinium dibromoiodate top
Crystal data top
C14H18IN2+·Br2IF(000) = 292
Mr = 627.92Dx = 2.254 Mg m3
Triclinic, P1Melting point: 383(1) K
a = 7.5777 (7) ÅMo Kα radiation, λ = 0.71073 Å
b = 8.2610 (7) ÅCell parameters from 3235 reflections
c = 8.5800 (7) Åθ = 2.5–30.0°
α = 99.09 (1)°µ = 7.71 mm1
β = 101.45 (1)°T = 120 K
γ = 114.20 (1)°Block, orange
V = 462.6 (1) Å30.10 × 0.08 × 0.02 mm
Z = 1
Data collection top
Bruker SMART 6K CCD area-detector
diffractometer
2693 independent reflections
Radiation source: fine-focus sealed tube2309 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.037
Detector resolution: 5.6 pixels mm-1θmax = 30.0°, θmin = 2.5°
ω scansh = 1010
Absorption correction: multi-scan
(SADABS; Bruker, 2003)
k = 1111
Tmin = 0.637, Tmax = 0.861l = 1212
6548 measured reflections
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.031Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.076H-atom parameters constrained
S = 0.99 w = 1/[σ2(Fo2) + (0.0387P)2]
where P = (Fo2 + 2Fc2)/3
2693 reflections(Δ/σ)max < 0.001
98 parametersΔρmax = 2.54 e Å3
0 restraintsΔρmin = 1.41 e Å3
Special details top

Experimental. The data collection nominally covered full sphere of reciprocal space, by a combination of 3 sets of ω scans; each set at different φ angles and each scan (20 s exposure) covering 0.3° in ω. Crystal to detector distance 4.85 cm.

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
I10.50000.50000.50000.01576 (9)
I20.00000.00000.50000.01764 (9)
Br0.12080 (6)0.18586 (6)0.30774 (5)0.02574 (10)
N0.3548 (4)0.4793 (4)0.2315 (3)0.0157 (5)
C10.3316 (6)0.1696 (5)0.1580 (5)0.0237 (8)
H110.47490.20850.21090.028 (7)*
H120.28220.06840.05840.028 (7)*
H130.25350.12790.23470.028 (7)*
C20.3060 (5)0.3288 (5)0.1115 (4)0.0186 (7)
C30.2344 (5)0.3203 (5)0.0527 (4)0.0225 (7)
H30.20210.21400.13660.027*
C40.2092 (6)0.4668 (6)0.0944 (4)0.0230 (7)
H40.16040.46260.20660.028*
C50.2572 (5)0.6189 (5)0.0308 (4)0.0210 (7)
H50.24160.72070.00460.025*
C60.3291 (5)0.6239 (5)0.1946 (4)0.0173 (6)
C70.3721 (6)0.7836 (6)0.3326 (5)0.0256 (8)
H710.29640.73850.40990.033 (7)*
H720.33050.86850.28730.033 (7)*
H730.51730.84830.39080.033 (7)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
I10.01858 (15)0.01675 (16)0.01325 (15)0.00838 (12)0.00566 (11)0.00521 (11)
I20.01924 (16)0.02170 (17)0.01317 (15)0.01004 (13)0.00530 (11)0.00509 (12)
Br0.0292 (2)0.0335 (2)0.02382 (19)0.01926 (17)0.01002 (15)0.01507 (16)
N0.0171 (13)0.0173 (14)0.0139 (13)0.0083 (11)0.0056 (10)0.0051 (11)
C10.036 (2)0.0186 (18)0.0163 (17)0.0139 (16)0.0061 (15)0.0035 (14)
C20.0186 (16)0.0225 (18)0.0160 (16)0.0097 (14)0.0073 (13)0.0051 (13)
C30.0237 (18)0.026 (2)0.0155 (16)0.0114 (15)0.0044 (13)0.0023 (14)
C40.0255 (18)0.031 (2)0.0155 (16)0.0143 (16)0.0065 (14)0.0100 (15)
C50.0235 (17)0.0264 (19)0.0196 (17)0.0141 (15)0.0087 (14)0.0123 (15)
C60.0201 (16)0.0201 (17)0.0163 (16)0.0107 (14)0.0101 (13)0.0065 (13)
C70.033 (2)0.028 (2)0.0201 (18)0.0191 (17)0.0072 (15)0.0059 (15)
Geometric parameters (Å, º) top
I1—Ni2.294 (3)C3—C41.389 (5)
I1—N2.294 (3)C3—H30.9500
I2—Br2.6962 (4)C4—C51.382 (5)
I2—Brii2.6962 (4)C4—H40.9500
N—C21.345 (5)C5—C61.390 (5)
N—C61.361 (4)C5—H50.9500
C1—C21.507 (5)C6—C71.500 (5)
C1—H110.9801C7—H710.9800
C1—H120.9800C7—H720.9800
C1—H130.9800C7—H730.9801
C2—C31.385 (5)
Ni—I1—N180.0C4—C3—H3120.1
Br—I2—Brii179.999 (12)C5—C4—C3118.6 (3)
C2—N—C6120.8 (3)C5—C4—H4120.8
C2—N—I1119.8 (2)C3—C4—H4120.7
C6—N—I1119.4 (2)C4—C5—C6120.3 (3)
C2—C1—H11109.7C4—C5—H5119.7
C2—C1—H12109.3C6—C5—H5120.0
H11—C1—H12109.5N—C6—C5119.8 (3)
C2—C1—H13109.4N—C6—C7119.1 (3)
H11—C1—H13109.5C5—C6—C7121.1 (3)
H12—C1—H13109.5C6—C7—H71109.5
N—C2—C3120.7 (3)C6—C7—H72109.4
N—C2—C1119.0 (3)H71—C7—H72109.5
C3—C2—C1120.3 (3)C6—C7—H73109.6
C2—C3—C4119.9 (3)H71—C7—H73109.5
C2—C3—H3120.0H72—C7—H73109.5
Symmetry codes: (i) x+1, y+1, z+1; (ii) x, y, z+1.
 

Acknowledgements

The authors are grateful to the EPSRC for a DTA award to SJRT and to GlaxoSmithKline Pharmaceuticals for a CASE studentship.

References

First citationÁlvarez-Rúa, C., García-Granda, S., Bellesteros, A., Gonzáles-Bobes, F. & Gonzáles, J. M. (2002). Acta Cryst. E58, o1381–o1383.  Web of Science CSD CrossRef IUCr Journals Google Scholar
First citationBatsanov, A. S., Howard, J. A. K., Lightfoot, A. P., Twiddle, S. J. R. & Whiting, A. (2005). Eur. J. Org. Chem. pp. 1876–1883.  CrossRef Google Scholar
First citationBrayer, G. D. & James, M. N. G. (1982). Acta Cryst. B38, 654–657.  CSD CrossRef CAS Web of Science IUCr Journals Google Scholar
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First citationBruker (2001). SMART (Version 5.625), SAINT (Version 6.02A) and SHELXTL (Version 6.12). Bruker AXS Inc, Madison, Wisconsin, USA.  Google Scholar
First citationBruker (2003). SADABS. Version 2.10. Bruker AXS Inc, Madison, Wisconsin, USA.  Google Scholar
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First citationHuber, K. P. & Herzberg, G. (1979). In Molecular Spectra and Molecular Structure, Vol. IV, Constants of Diatomic Molecules. New York: van Nostrand.  Google Scholar
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First citationPadmanabhan, K., Paul, I. C. & Curtin, D. Y. (1990). Acta Cryst. C46, 88–92.  CSD CrossRef CAS Web of Science IUCr Journals Google Scholar
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First citationSvensson, P. H. & Kloo, L. (2000). J. Chem. Soc. Dalton Trans. pp. 2449–2455.  CrossRef Google Scholar

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