Crystal structure of the pyridine–diiodine (1/1) adduct

In the title adduct, C₅H₅N·I₂, the N—I distance [2.424 (8) Å] is remarkably shorter than the sum of the van der Waals radii. The line through the I atoms forms an angle of 78.39 (16)° with the normal to the pyridine ring.

1. Related literature

For the structure of the pyridine–I₂ 1:2 adduct, see: Hassel & Hope (1961). For the crystal structures of pyridine with ICl and IBr, see: Rømming (1972); Dahl et al. (1967). For van der Walls radii, see: Bondi (1964). For the I—I distance of iodine, see: Buontempo et al. (1997). For I—I^⋯N angles in halogen bonding, see: Desiraju et al. (2013).

2. Experimental

2.1. Crystal data

• C₅H₅N·I₂

• M_r = 332.90

• Monoclinic, P 2/c

• a = 9.2432 (6) Å

• b = 4.3392 (2) Å

• c = 20.1953 (13) Å

• β = 98.468 (3)°

• V = 801.16 (8) ų

• Z = 4

• Mo Kα radiation

• μ = 7.76 mm⁻¹

• T = 120 K

• 0.09 × 0.07 × 0.02 mm

2.2. Data collection

• Bruker KAPPA APEX II CCD diffractometer

• Absorption correction: numerical (SADABS; Bruker,2012) T_min = 0.574, T_max = 0.902

• 6585 measured reflections

• 1853 independent reflections

• 1437 reflections with I > 2σ(I)

• R_int = 0.062

2.3. Refinement

• R[F² > 2σ(F²)] = 0.049

• wR(F²) = 0.091

• S = 1.07

• 1853 reflections

• 73 parameters

• H-atom parameters constrained

• Δρ_max = 1.11 e Å⁻³

• Δρ_min = −1.26 e Å⁻³

Data collection: Collect (Nonius, 2000); cell refinement: DENZO/SCALEPACK (Otwinowski & Minor, 1997); data reduction: DENZO/SCALEPACK; program(s) used to solve structure: SUPERFLIP (Palatinus & Chapuis, 2007; Palatinus & van der Lee, 2008; Palatinus et al., 2012); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: OLEX2.

Supporting information

S1. Comment

Diiodine is capable to act as halogen bond donor and form stable halogen bonds with Lewis bases, such as pyridine, due to the strong charge transfer. In the case of the pyridine-I₂ 1:2 adduct (Hassel & Hope, 1961), the interaction eventually results in the heterolytic cleavage of I₂ and formaton of [py₂I]⁺ I₃^- ion pairs. Although the crystal structures involving pyridine and interhalogens ICl and IBr are known (Rømming, 1972; Dahl et al., 1967), the title pyI₂ 1:1 adduct has not been reported earlier. The N1—I1 distance in pyI₂ (2.425 (8) Å) is remarkably shorter than the sum of the van der Walls radii of iodine and nitrogen (3.53 Å; Bondi, 1964). The I—I distance (2.8043 (9) Å) is significantly longer than that observed in free diiodine in solid state (2.715 Å; Buontempo et al., 1997). The I—I···N angle is approximately linear (176.44 (18)°) as expected in halogen bonds (Desiraju et al., 2013).

Related literature

For the structure of the pyridine– I₂ 1:2 adduct, see: Hassel & Hope (1961). For the crystal structures of pyridine with ICl and IBr, see: Rømming (1972); Dahl et al. (1967). For van der Walls radii, see: Bondi (1964). For the I—I distance of iodine, see: Buontempo et al. (1997). For I—I^···N angles in halogen bonding, see: Desiraju et al. (2013).

S2. Experimental

The title compound was synthesized by dissolving iodine (200 mg) in ethanol (5 ml) and adding pyridine (1 ml) into this solution. The solution was left to evaporate unde ambient conditions and after a couple of days light yellow crystals were formed.

S3. Refinement

All H atoms were positioned geometrically and refined using a riding model with C—H = 0.95 Å and with U_iso(H) = 1.2 U_eq(C).

Computing details

Data collection: Collect (Nonius, 2000); cell refinement: DENZO/SCALEPACK (Otwinowski & Minor, 1997); data reduction: DENZO/SCALEPACK (Otwinowski & Minor, 1997); program(s) used to solve structure: Superflip (Palatinus & Chapuis, 2007; Palatinus & van der Lee, 2008; Palatinus et al., 2012); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: Olex2 (Dolomanov et al., 2009); software used to prepare material for publication: Olex2 (Dolomanov et al., 2009).

Figures

Fig. 1. The molecular structure of the title compound, with 50% probability displacement ellipsoids for non-H atoms.

Pyridine–diiodine (1/1)

Crystal data

C5H5N·I2	F(000) = 592
Mr = 332.90	Dx = 2.760 Mg m^−3
Monoclinic, P2/c	Mo Kα radiation, λ = 0.71073 Å
a = 9.2432 (6) Å	Cell parameters from 1865 reflections
b = 4.3392 (2) Å	θ = 1.0–27.5°
c = 20.1953 (13) Å	µ = 7.76 mm^−1
β = 98.468 (3)°	T = 120 K
V = 801.16 (8) Å^3	Plate, clear light yellow
Z = 4	0.09 × 0.07 × 0.02 mm

Data collection

Bruker KAPPA APEX II CCD diffractometer	1853 independent reflections
Radiation source: fine-focus sealed tube	1437 reflections with I > 2σ(I)
Curved graphite crystal monochromator	Rint = 0.062
Detector resolution: 16 pixels mm^-1	θmax = 27.6°, θmin = 2.2°
ϕ scans and ω scans with κ offset	h = −11→11
Absorption correction: numerical (SADABS; Bruker,2012)	k = −5→5
Tmin = 0.574, Tmax = 0.902	l = −26→25
6585 measured reflections

Refinement

Refinement on F^2	Primary atom site location: iterative
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.049	H-atom parameters constrained
wR(F^2) = 0.091	w = 1/[σ^2(Fo^2) + (0.0153P)^2 + 9.3396P] where P = (Fo^2 + 2Fc^2)/3
S = 1.07	(Δ/σ)max = 0.001
1853 reflections	Δρmax = 1.11 e Å^−3
73 parameters	Δρmin = −1.26 e Å^−3
0 restraints

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
I1	0.27234 (6)	0.59684 (13)	0.54587 (3)	0.02083 (16)
I2	0.32645 (6)	0.35101 (14)	0.67558 (3)	0.02480 (18)
N1	0.2243 (7)	0.8407 (18)	0.4368 (4)	0.0243 (18)
C5	0.3349 (9)	0.933 (2)	0.4053 (4)	0.0207 (19)
H5	0.4323	0.8743	0.4223	0.025*
C3	0.1668 (10)	1.198 (2)	0.3214 (5)	0.028 (2)
H3	0.1471	1.3178	0.2818	0.033*
C1	0.0849 (10)	0.921 (2)	0.4121 (5)	0.030 (2)
H1	0.0069	0.8529	0.4342	0.035*
C2	0.0549 (10)	1.098 (2)	0.3558 (5)	0.030 (2)
H2	−0.0434	1.1533	0.3399	0.036*
C4	0.3076 (10)	1.112 (2)	0.3480 (5)	0.030 (2)
H4	0.3872	1.1783	0.3266	0.036*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
I1	0.0189 (3)	0.0224 (3)	0.0212 (3)	−0.0010 (2)	0.0027 (2)	−0.0016 (3)
I2	0.0253 (3)	0.0267 (3)	0.0222 (4)	0.0029 (2)	0.0031 (3)	0.0011 (3)
N1	0.016 (4)	0.032 (4)	0.024 (4)	−0.003 (3)	0.004 (3)	−0.007 (4)
C5	0.017 (4)	0.031 (5)	0.013 (5)	−0.001 (4)	−0.001 (3)	0.000 (4)
C3	0.031 (5)	0.035 (6)	0.014 (5)	−0.002 (4)	−0.003 (4)	0.004 (4)
C1	0.019 (5)	0.039 (6)	0.031 (6)	−0.009 (4)	0.007 (4)	0.005 (5)
C2	0.014 (4)	0.049 (7)	0.026 (6)	−0.002 (4)	−0.003 (4)	0.002 (5)
C4	0.025 (5)	0.042 (6)	0.022 (6)	−0.006 (4)	0.005 (4)	0.003 (5)

Geometric parameters (Å, º)

I1—I2	2.8043 (9)	C5—C4	1.388 (13)
I1—N1	2.425 (8)	C3—C2	1.397 (12)
N1—C5	1.342 (10)	C3—C4	1.383 (13)
N1—C1	1.357 (12)	C1—C2	1.364 (14)
N1—I1—I2	176.44 (18)	C4—C3—C2	116.6 (9)
C5—N1—I1	120.7 (6)	N1—C1—C2	121.1 (8)
C5—N1—C1	119.8 (8)	C1—C2—C3	120.9 (9)
C1—N1—I1	118.9 (6)	C3—C4—C5	121.2 (8)
N1—C5—C4	120.3 (8)
I1—N1—C5—C4	−170.3 (7)	C5—N1—C1—C2	−0.8 (15)
I1—N1—C1—C2	170.4 (8)	C1—N1—C5—C4	0.8 (14)
N1—C5—C4—C3	−0.9 (15)	C2—C3—C4—C5	1.0 (15)
N1—C1—C2—C3	1.0 (16)	C4—C3—C2—C1	−1.0 (15)