1,5-Diiodo­naphthalene

In the crystal structure of the title compound, C₁₀H₆I₂, the mol­ecules are planar and packed in T-shaped edge-to-face mode. They are held together by weak I...π and I...I non-bonding inter­molecular inter­actions.

Key indicators

• Single-crystal X-ray study
• T = 223 K
• Mean [sigma](C-C) = 0.006 Å
• R factor = 0.033
• wR factor = 0.077
• Data-to-parameter ratio = 25.5

checkCIF/PLATON results

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Alert level G
REFLT03_ALERT_4_G Please check that the estimate of the number of Friedel pairs is
            correct. If it is not, please give the correct count in the
            _publ_section_exptl_refinement section of the submitted CIF.
           From the CIF: _diffrn_reflns_theta_max           30.01
           From the CIF: _reflns_number_total               2783
           Count of symmetry unique reflns         1667
           Completeness (_total/calc)            166.95%
           TEST3: Check Friedels for noncentro structure
           Estimate of Friedel pairs measured      1116
           Fraction of Friedel pairs measured     0.669
           Are heavy atom types Z>Si present        yes

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

   0 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
   1 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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S1. Comment

The structure of isomer (I) has C—I bond lengths (2.090–2.103 Å) which are slightly shorter than the bond lengths in 1,8-diiodonaphthalene (2.11–2.13 Å). This can be attributed to the requirement for strain relief in the latter. The geometry of the naphthalene skeleton in (I) is similar to the parent naphthalene (Cruickshank, 1957) except for the C5—C10 bond which at 1.431 (4) Å is longer in (I) compared to 1.410 Å in the parent naphthalene. The molecules of (I) are planar (Figure 1).

The most interesting feature of the title compound (I) is its crystal packing (Figure 2) which is different from the packings in 1,8-diiodonaphthalene (Bock et al. 1998) or 2,3-diiodonaphthalene (Novak 2007). In the last two compounds crystal packing comprises π -π stacking and herringbone motif, respectively with individual molecules being held together by I···I non-bonding, van der Waals forces. In (I) on the other hand the molecules are packed in a way which facilitates T-shaped edge-face mode of intermolecular interaction (Nguyen et al. 1999). The separations pertaining to the shortest intermolecular contacts, which hold the structure together are given in Table 1.

Related literature

The analysis of the electronic structure of 1,8-diiodonaphthalene has revealed the existence of intramolecular steric repulsions and through-space interactions between vicinal iodines (Novak et al., 2003). Pronounced steric repulsion between iodine substituents was also observed in its structure in which the I atoms are twisted out of the aromatic ring plane by 5–17° (Bock et al., 1998).

For related literature, see: Cruickshank (1957); Nguyen et al. (1999); Novak (2007).

S2. Experimental

The synthesis of 1,5-diiodonaphthalene was carried out according to the procedure reported previously by Novak et al. (2003). Single crystals of (I) were obtained from the sublimate.

S3. Refinement

H atoms were positioned geometrically (C—H = 0.94 Å) and refined as riding with U_iso (H) = 1.2 U_eq (C). The highest peak is located 0.74 Å from atom I1 and the deepest hole is located -0.908 Å from atom I1. This is a chiral space group. The Friedel equivalents were not merged. The Flack value indicates the correct absolute structure. However, the molecule is not chiral, it is the packing that results in the chiral space group.

Computing details

Data collection: SMART (Bruker, 1997); cell refinement: SMART (Bruker, 1997); data reduction: SAINT (Bruker, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Sheldrick, 1997); software used to prepare material for publication: SHELXTL.

Figures

	Fig. 1. Molecular structure of (I) with displacement parameters drawn at the 50% probability level.
	Fig. 2. Crystal packing of (I) viewed along a axis. H atoms have been omitted.

1,5-Diiodonaphthalene

Crystal data

C10H6I2	F(000) = 688
Mr = 379.95	Dx = 2.556 Mg m^−3
Orthorhombic, P212121	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ac 2ab	Cell parameters from 4117 reflections
a = 7.0211 (5) Å	θ = 2.9–29.4°
b = 11.5366 (8) Å	µ = 6.31 mm^−1
c = 12.1874 (8) Å	T = 223 K
V = 987.17 (12) Å^3	RECTANGULAR ROD, red
Z = 4	0.40 × 0.30 × 0.22 mm

Data collection

Bruker SMART CCD area-detector Diffractometer	2783 independent reflections
Radiation source: fine-focus sealed tube	2640 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.024
ω scans	θmax = 30.0°, θmin = 2.4°
Absorption correction: multi-scan SADABS (Sheldrick, 2001)	h = −9→9
Tmin = 0.121, Tmax = 0.249	k = −14→15
8070 measured reflections	l = −16→13

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.033	H-atom parameters constrained
wR(F^2) = 0.077	w = 1/[σ^2(Fo^2) + (0.039P)^2 + 0.3767P] where P = (Fo^2 + 2Fc^2)/3
S = 1.09	(Δ/σ)max = 0.002
2783 reflections	Δρmax = 0.74 e Å^−3
109 parameters	Δρmin = −0.91 e Å^−3
0 restraints	Absolute structure: Flack (1983), 1116 Friedel pairs
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.001 (4)

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
I1	0.49839 (5)	0.36624 (3)	1.00766 (3)	0.05194 (10)
I2	1.04897 (4)	0.85089 (3)	0.75365 (3)	0.05002 (10)
C1	0.5745 (6)	0.5033 (4)	0.9044 (3)	0.0392 (8)
C2	0.4501 (6)	0.5338 (4)	0.8239 (4)	0.0455 (10)
H2	0.3342	0.4939	0.8161	0.055*
C3	0.4960 (8)	0.6258 (4)	0.7519 (4)	0.0454 (8)
H3	0.4093	0.6462	0.6964	0.054*
C4	0.6596 (6)	0.6846 (4)	0.7609 (3)	0.0411 (8)
H4	0.6860	0.7454	0.7119	0.049*
C5	0.7929 (5)	0.6560 (3)	0.8436 (3)	0.0339 (7)
C6	0.7516 (6)	0.5630 (4)	0.9176 (3)	0.0349 (8)
C7	0.8822 (6)	0.5353 (4)	1.0011 (4)	0.0431 (9)
H7	0.8525	0.4754	1.0504	0.052*
C8	1.0531 (7)	0.5938 (5)	1.0127 (4)	0.0455 (10)
H8	1.1402	0.5728	1.0678	0.055*
C9	1.0939 (6)	0.6865 (4)	0.9391 (4)	0.0438 (10)
H9	1.2078	0.7286	0.9465	0.053*
C10	0.9689 (5)	0.7142 (4)	0.8581 (3)	0.0373 (8)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
I1	0.0586 (2)	0.04360 (17)	0.05359 (17)	−0.01052 (14)	0.00536 (16)	0.00267 (12)
I2	0.05333 (18)	0.04250 (17)	0.05423 (17)	−0.00836 (11)	0.00393 (14)	0.00466 (14)
C1	0.043 (2)	0.036 (2)	0.0386 (19)	−0.0013 (17)	0.0048 (17)	−0.0050 (15)
C2	0.038 (2)	0.050 (3)	0.049 (2)	−0.0025 (19)	−0.0029 (18)	−0.0041 (19)
C3	0.0436 (18)	0.052 (2)	0.040 (2)	0.003 (2)	−0.0097 (17)	0.002 (2)
C4	0.0428 (19)	0.043 (2)	0.038 (2)	0.0001 (16)	−0.0003 (18)	−0.0015 (19)
C5	0.0344 (17)	0.0306 (19)	0.0366 (17)	0.0019 (15)	0.0025 (14)	−0.0043 (15)
C6	0.0388 (19)	0.036 (2)	0.0303 (17)	0.0038 (16)	0.0028 (14)	−0.0033 (15)
C7	0.049 (2)	0.041 (2)	0.040 (2)	0.0015 (17)	−0.0015 (19)	0.0000 (18)
C8	0.043 (2)	0.053 (3)	0.041 (2)	0.004 (2)	−0.006 (2)	0.0018 (19)
C9	0.040 (2)	0.045 (2)	0.047 (2)	−0.0025 (18)	−0.0044 (18)	−0.0083 (19)
C10	0.037 (2)	0.036 (2)	0.0393 (19)	−0.0002 (17)	0.0024 (16)	−0.0047 (15)

Geometric parameters (Å, º)

I1—C1	2.090 (4)	C5—C10	1.417 (5)
I2—C10	2.103 (4)	C5—C6	1.432 (6)
C1—C2	1.360 (6)	C6—C7	1.406 (6)
C1—C6	1.431 (6)	C7—C8	1.384 (7)
C2—C3	1.414 (7)	C7—H7	0.9400
C2—H2	0.9400	C8—C9	1.425 (7)
C3—C4	1.339 (7)	C8—H8	0.9400
C3—H3	0.9400	C9—C10	1.358 (6)
C4—C5	1.415 (5)	C9—H9	0.9400
C4—H4	0.9400
C2—C1—C6	121.0 (4)	C7—C6—C1	122.6 (4)
C2—C1—I1	117.8 (3)	C7—C6—C5	119.6 (4)
C6—C1—I1	121.2 (3)	C1—C6—C5	117.8 (4)
C1—C2—C3	119.7 (4)	C8—C7—C6	121.9 (4)
C1—C2—H2	120.1	C8—C7—H7	119.0
C3—C2—H2	120.1	C6—C7—H7	119.0
C4—C3—C2	121.7 (4)	C7—C8—C9	118.4 (4)
C4—C3—H3	119.2	C7—C8—H8	120.8
C2—C3—H3	119.2	C9—C8—H8	120.8
C3—C4—C5	120.5 (4)	C10—C9—C8	120.2 (4)
C3—C4—H4	119.7	C10—C9—H9	119.9
C5—C4—H4	119.7	C8—C9—H9	119.9
C4—C5—C10	123.7 (4)	C9—C10—C5	122.9 (4)
C4—C5—C6	119.3 (4)	C9—C10—I2	116.3 (3)
C10—C5—C6	116.9 (3)	C5—C10—I2	120.8 (3)