2,3,6,7-Tetra­kis(bromo­meth­yl)naphthalene

The title compound, C₁₄H₁₂Br₄, crystallizes with imposed inversion symmetry. In the crystal, the mol­ecules pack in layers parallel to (10). The layers involve two Br...Br and one H...Br contact. Between the layers, one contact each of types Br...Br, H...Br and Br...π is observed.

Key indicators

• Single-crystal X-ray study
• T = 100 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.016
• wR factor = 0.034
• Data-to-parameter ratio = 25.9

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT480_ALERT_4_C Long H...A H-Bond Reported H6A    ..  BR2     ..       2.96 Ang.
PLAT480_ALERT_4_C Long H...A H-Bond Reported H6A    ..  BR2     ..       2.98 Ang.
PLAT480_ALERT_4_C Long H...A H-Bond Reported H5     ..  BR1     ..       3.11 Ang.
PLAT912_ALERT_4_C Missing # of FCF Reflections Above STh/L=  0.600         35

Alert level G
PLAT154_ALERT_1_G The su's on the Cell Angles are Equal  (x 10000)        300 Deg.

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   4 ALERT level C = Check and explain
   1 ALERT level G = General alerts; check

   1 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   0 ALERT type 2 Indicator that the structure model may be wrong or deficient
   0 ALERT type 3 Indicator that the structure quality may be low
   4 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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S1. Comment

The title compound is a symmetric rigid molecule with four bromomethyl groups. The bromine atoms can be easily substituted by other nucleophiles, which offers the opportunity of employing the compound as a building block for construction of various functional architectures. The title compound was prepared to serve as a spacer between two tetrathiafulvalene (TTF) groups in TTF-containing molecular tweezers (Skibiński et al., 2009). It was first employed as an intermediate in the preparation of triple-layered [2.2]naphthalenophane (Otsubo et al., 1983), and several other triple-layered cyclophanes (Otsubo et al., 1983; Yano et al., 1999). It was also used as an intermediate in the synthesis of H-bonded molecular capsules (Valdes et al., 1995; Rivera et al., 2001).

The molecule of the title compound is shown in Fig. 1. It displays crystallographic inversion symmetry (operator #1 - x, 1 - y, 1 - z); for this reason, the crystallographic numbering does not correspond to the IUPAC numbering scheme. Bond lengths and angles may be considered normal; the bromine atoms are directed to opposite sides of the ring system, with C(2)—C(3)—C(6)—Br(1) 92.22 (16), C(3)—C(4)—C(7)—Br2 - 79.86 (17)°, which leads to a +/-/-/+ pattern of Br atoms about the ring plane for the IUPAC-numbered C2,3,6,7; this contrasts with the -/-/+/+ pattern in 1,2,4,5-tetrakis(bromomethyl)benzene (Jones & Kuś, 2007), which is also inversion-symmetric.

Details of the packing interactions are given in the Tables. The molecules pack in layers parallel to (101). Within the layers, the contacts Br1···Br2, the longer Br2···Br2 and the shorter H6A···Br2 are observed. These combine to form columns of interactions parallel to the b axis; chains of molecules parallel to [101] (horizontal in Fig. 2) are also formed. The contacts Br2···Br2 (the shorter), H6A···Br2 (the longer) and Br1···Cg (Cg = centre of gravity of the ring C1–5 and C1#1) link the layers (Fig. 3). H5···Br1 3.11 Å between the layers is a borderline interaction. The Br···Cg interaction could alternatively be interpreted as Br···C5, which at 3.450 (2) Å is by far the shortest of the six Br···C contacts; it is often unclear which is the better interpretation in such systems (Jones & Kuś, 2010). Despite the presence of the naphthalene ring systems, there are no significant Cg···Cg interactions. The shortest H···Cg contact is H7A···Cg (1 - x,1 - y,-z) 3.10 Å between layers, but this is both long and has a narrow angle (124°). We can conclude that the crystal packing of the title compound is dominated by the contacts involving bromomethylene groups.

Related literature

For the use of 2,3,6,7-tetrakis(bromomethyl)naphthalene in the preparation of cyclophanes, see: Otsubo et al. (1983, 1989); Yano et al. (1999); Skibiński et al. (2009). For its applications in the synthesis of hydrogen-bonded molecular capsules, see: Valdes et al. (1995); Rivera et al. (2001). For reviews on halogen–halogen contacts and `weak' hydrogen bonding, see: Desiraju & Steiner (1999); Metrangolo & Resnati (2001); Metrangolo et al. (2008); Rissanen (2008). For the X-ray structures of the full series of ten isomeric bis(bromomethyl)naphthalenes, see: Jones & Kuś (2010). For the X-ray structures of two isomeric tetrakis(bromomethyl)benzene derivatives, see: Jones & Kuś (2007).

S2. Experimental

The title compound was prepared as described by Rivera et al. (2001) by treatment of a solution of 2,3-bis[{[(1,1-dimethylethyl)dimethylsilyl]oxy}methyl]- 6,7-bis[(phenylmethoxy)methyl]-naphthalene in chloroform with gaseous HBr. The compound was obtained as a colourless microcrystalline solid. Yield: 87%. Crystals suitable for X-ray diffraction were grown by slow evaporation of a solution in EtOH/hexane/CH₂Cl₂. M.p. (decomp.) 230–231° C (lit. 230° C). ¹H NMR (CDCl₃): δ = 7.83 (s, 4H), 4.84 (s, 8H) p.p.m..

The title compound is poorly soluble (< 1 g/L) in most organic solvents at room temperature, but is much more soluble in aromatic solvents, such as toluene or chlorobenzene, upon reflux.

S3. Refinement

Hydrogen atoms were included at calculated positions using a riding model with aromatic C—H 0.95, methylene C—H 0.99 Å. The U(H) values were fixed at 1.2 × U_eq(C) of the parent C atom.

Computing details

Data collection: CrysAlis PRO (Oxford Diffraction, 2009); cell refinement: CrysAlis PRO (Oxford Diffraction, 2009); data reduction: CrysAlis PRO (Oxford Diffraction, 2009); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: XP (Siemens, 1994); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures

	Fig. 1. Structure of the title compound in the crystal. Ellipsoids represent 50% probability levels. Only the asymmetric unit is numbered.
	Fig. 2. Molecular packing of the title compound as a layer parallel to (101). Br···Br and H···Br contacts are shown as thick dashed bonds.
	Fig. 3. Linking between the layers of the title compound. Br···Br and H···Br contacts are shown as thick dashed bonds. One representative Br···Cg contact is shown as a thin dashed bond (top left).

2,3,6,7-Tetrakis(bromomethyl)naphthalene

Crystal data

C14H12Br4	Z = 1
Mr = 499.88	F(000) = 236
Triclinic, P1	Dx = 2.254 Mg m^−3
Hall symbol: -P 1	Melting point: 503 K
a = 6.6144 (2) Å	Mo Kα radiation, λ = 0.71073 Å
b = 7.1770 (2) Å	Cell parameters from 9533 reflections
c = 8.7761 (3) Å	θ = 2.4–30.7°
α = 84.744 (3)°	µ = 10.91 mm^−1
β = 78.251 (3)°	T = 100 K
γ = 64.555 (3)°	Prism, colourless
V = 368.32 (2) Å^3	0.20 × 0.06 × 0.04 mm

Data collection

Oxford Diffraction Xcalibur Eos diffractometer	2122 independent reflections
Radiation source: Enhance (Mo) X-ray Source	1716 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.031
Detector resolution: 16.1419 pixels mm^-1	θmax = 30.0°, θmin = 2.4°
ω–scan	h = −9→9
Absorption correction: multi-scan (CrysAlis PRO; Oxford Diffraction, 2009)	k = −10→10
Tmin = 0.356, Tmax = 1.000	l = −11→12
17701 measured reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.016	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.034	H-atom parameters constrained
S = 0.92	w = 1/[σ^2(Fo^2) + (0.0181P)^2] where P = (Fo^2 + 2Fc^2)/3
2122 reflections	(Δ/σ)max = 0.001
82 parameters	Δρmax = 0.50 e Å^−3
0 restraints	Δρmin = −0.49 e Å^−3

Special details

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 (Ų)

	x	y	z	Uiso*/Ueq
Br1	0.64988 (3)	−0.00387 (3)	0.24985 (2)	0.01628 (5)
Br2	0.23208 (3)	0.72525 (3)	0.44061 (2)	0.01672 (5)
C1	−0.0170 (3)	0.4100 (3)	0.02483 (19)	0.0108 (3)
C2	0.0922 (3)	0.2877 (3)	0.14549 (19)	0.0122 (3)
H2	0.0699	0.1672	0.1791	0.015*
C3	0.2297 (3)	0.3393 (3)	0.21518 (19)	0.0111 (3)
C4	0.2621 (3)	0.5223 (3)	0.16547 (19)	0.0110 (3)
C5	0.1575 (3)	0.6419 (3)	0.04994 (19)	0.0112 (3)
H5	0.1791	0.7633	0.0185	0.013*
C6	0.3431 (3)	0.2029 (3)	0.34014 (19)	0.0136 (3)
H6A	0.2495	0.1316	0.3945	0.016*
H6B	0.3563	0.2876	0.4173	0.016*
C7	0.4062 (3)	0.5854 (3)	0.24055 (18)	0.0135 (3)
H7A	0.4559	0.6799	0.1704	0.016*
H7B	0.5437	0.4620	0.2592	0.016*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br1	0.01360 (10)	0.01494 (10)	0.01724 (10)	−0.00349 (8)	−0.00312 (7)	0.00232 (7)
Br2	0.01615 (10)	0.01865 (11)	0.01468 (9)	−0.00544 (8)	−0.00321 (7)	−0.00581 (7)
C1	0.0099 (8)	0.0112 (9)	0.0093 (8)	−0.0031 (7)	0.0001 (6)	−0.0012 (6)
C2	0.0130 (8)	0.0120 (9)	0.0105 (8)	−0.0053 (7)	0.0000 (7)	−0.0003 (6)
C3	0.0085 (8)	0.0127 (9)	0.0087 (8)	−0.0016 (7)	−0.0006 (6)	−0.0008 (6)
C4	0.0092 (8)	0.0139 (9)	0.0097 (8)	−0.0050 (7)	0.0011 (6)	−0.0040 (6)
C5	0.0111 (8)	0.0104 (8)	0.0120 (8)	−0.0055 (7)	0.0012 (6)	−0.0020 (6)
C6	0.0111 (8)	0.0156 (9)	0.0115 (8)	−0.0033 (7)	−0.0017 (7)	0.0003 (7)
C7	0.0128 (8)	0.0177 (9)	0.0101 (8)	−0.0064 (7)	−0.0017 (7)	−0.0023 (7)

Geometric parameters (Å, º)

Br1—C6	1.9801 (16)	C4—C7	1.493 (2)
Br2—C7	1.9806 (16)	C5—C1^i	1.422 (2)
C1—C2	1.418 (2)	C2—H2	0.9500
C1—C1^i	1.420 (3)	C5—H5	0.9500
C1—C5^i	1.422 (2)	C6—H6A	0.9900
C2—C3	1.377 (2)	C6—H6B	0.9900
C3—C4	1.436 (2)	C7—H7A	0.9900
C3—C6	1.494 (2)	C7—H7B	0.9900
C4—C5	1.363 (2)
C2—C1—C1^i	118.85 (18)	C1—C2—H2	119.2
C2—C1—C5^i	122.57 (15)	C4—C5—H5	119.0
C1^i—C1—C5^i	118.58 (19)	C1^i—C5—H5	119.0
C3—C2—C1	121.68 (15)	C3—C6—H6A	109.6
C2—C3—C4	119.29 (15)	Br1—C6—H6A	109.6
C2—C3—C6	119.30 (15)	C3—C6—H6B	109.6
C4—C3—C6	121.41 (15)	Br1—C6—H6B	109.6
C5—C4—C3	119.70 (15)	H6A—C6—H6B	108.1
C5—C4—C7	119.52 (15)	C4—C7—H7A	109.6
C3—C4—C7	120.77 (15)	Br2—C7—H7A	109.6
C4—C5—C1^i	121.90 (15)	C4—C7—H7B	109.6
C3—C6—Br1	110.35 (11)	Br2—C7—H7B	109.6
C4—C7—Br2	110.18 (11)	H7A—C7—H7B	108.1
C3—C2—H2	119.2
C1^i—C1—C2—C3	0.0 (3)	C6—C3—C4—C7	−1.7 (2)
C5^i—C1—C2—C3	179.24 (16)	C3—C4—C5—C1^i	−0.5 (2)
C1—C2—C3—C4	0.5 (2)	C7—C4—C5—C1^i	−179.53 (15)
C1—C2—C3—C6	−179.09 (15)	C2—C3—C6—Br1	92.22 (16)
C2—C3—C4—C5	−0.2 (2)	C4—C3—C6—Br1	−87.36 (16)
C6—C3—C4—C5	179.34 (15)	C5—C4—C7—Br2	99.15 (16)
C2—C3—C4—C7	178.76 (15)	C3—C4—C7—Br2	−79.86 (17)

Symmetry code: (i) −x, −y+1, −z.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C6—H6A···Br2^ii	0.99	2.96	3.7967 (17)	143
C6—H6A···Br2^iii	0.99	2.98	3.7359 (16)	134
C5—H5···Br1^iv	0.95	3.11	3.9399 (16)	147

Symmetry codes: (ii) x, y−1, z; (iii) −x, −y+1, −z+1; (iv) −x+1, −y+1, −z.