Rerefinement of triethyl­ammonium iodide from new intensity data at low temperature

The anion and the cation of the title compound, C₆H₁₆N⁺·I⁻, are located on special positions of site symmetry 3m. As a result, there is only a sixth of an ion pair in the asymmetric unit. The anion and cation are connected via an N—H...I hydrogen bond. Each methyl­ene group is disordered over two equally occupied positions.

Key indicators

• Single-crystal X-ray study
• T = 173 K
• Mean [sigma](Please check) = 0.000 Å
• R factor = 0.025
• wR factor = 0.071
• Data-to-parameter ratio = 18.6

checkCIF/PLATON results

No syntax errors found



Alert level B
PLAT301_ALERT_3_B Main Residue  Disorder .........................      27.00 Perc.

Alert level C
STRVA01_ALERT_4_C           Flack test results are ambiguous.
           From the CIF: _refine_ls_abs_structure_Flack    0.500
           From the CIF: _refine_ls_abs_structure_Flack_su    0.130
PLAT033_ALERT_2_C Flack Parameter Value Deviates from Zero .......       0.50
PLAT042_ALERT_1_C Calc. and Rep. MoietyFormula Strings Differ ....          ?
PLAT094_ALERT_2_C Ratio of Maximum / Minimum Residual Density ....       2.31
PLAT242_ALERT_2_C Check Low    U(eq) as Compared to Neighbors ....         C1
PLAT764_ALERT_4_C Overcomplete CIF Bond List Detected (Rep/Expd) .       1.14 Ratio

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           27.54
           From the CIF: _reflns_number_total                464
           Count of symmetry unique reflns          254
           Completeness (_total/calc)            182.68%
           TEST3: Check Friedels for noncentro structure
           Estimate of Friedel pairs measured       210
           Fraction of Friedel pairs measured     0.827
           Are heavy atom types Z>Si present          yes

   0 ALERT level A = In general: serious problem
   1 ALERT level B = Potentially serious problem
   6 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
   3 ALERT type 2 Indicator that the structure model may be wrong or deficient
   1 ALERT type 3 Indicator that the structure quality may be low
   3 ALERT type 4 Improvement, methodology, query or suggestion

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Computing details

Data collection: X-AREA (Stoe & Cie, 2001); cell refinement: X-AREA; data reduction: X-AREA; program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XP in SHELXTL-Plus (Sheldrick, 1991); software used to prepare material for publication: SHELXL97 and PLATON (Spek, 1990).

(I)

Crystal data

C6H16N^+·I^−	Dx = 1.497 Mg m^−3
Mr = 229.10	Mo Kα radiation, λ = 0.71073 Å
Hexagonal, P63mc	Cell parameters from 12855 reflections
Hall symbol: P 6c -2c	θ = 3.8–27.5°
a = 8.6555 (11) Å	µ = 3.08 mm^−1
c = 7.8351 (9) Å	T = 173 K
V = 508.35 (11) Å^3	Needle, colourless
Z = 2	0.35 × 0.12 × 0.11 mm
F(000) = 224

Data collection

Stoe IPDS-II two-circle diffractometer	464 independent reflections
Radiation source: fine-focus sealed tube	421 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.035
ω scans	θmax = 27.5°, θmin = 4.7°
Absorption correction: multi-scan (MULABS; Spek, 1990; Blessing, 1995)	h = −11→11
Tmin = 0.404, Tmax = 0.714	k = −11→11
5945 measured reflections	l = −10→10

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)] = 0.025	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.071	w = 1/[σ^2(Fo^2) + (0.0533P)^2 + 0.0681P] where P = (Fo^2 + 2Fc^2)/3
S = 1.09	(Δ/σ)max < 0.001
464 reflections	Δρmax = 1.00 e Å^−3
25 parameters	Δρmin = −0.43 e Å^−3
1 restraint	Absolute structure: Flack (1983), 232 Friedel pairs
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.50 (13)

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	Occ. (<1)
I1	0.6667	0.3333	0.3706	0.0532 (2)
N1	0.6667	0.3333	0.8210 (14)	0.053 (2)
H1	0.6667	0.3333	0.70 (3)	0.07 (5)*
C1	0.6898 (10)	0.1799 (11)	0.8459 (12)	0.047 (2)	0.50
H1A	0.6766	0.1219	0.7340	0.056*	0.50
H1B	0.5813	0.0987	0.9111	0.056*	0.50
C2	0.8335 (5)	0.1665 (5)	0.9478 (13)	0.0740 (19)
H2A	0.8038	0.0419	0.9509	0.111*	0.25
H2B	0.9446	0.2387	0.8879	0.111*	0.25
H2C	0.8430	0.2104	1.0654	0.111*	0.25
H2D	0.9564	0.1945	0.9509	0.111*	0.25
H2E	0.7879	0.1553	1.0654	0.111*	0.25
H2F	0.7596	0.0538	0.8879	0.111*	0.25

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
I1	0.0535 (2)	0.0535 (2)	0.0525 (3)	0.02675 (11)	0.000	0.000
N1	0.043 (2)	0.043 (2)	0.071 (7)	0.0217 (12)	0.000	0.000
C1	0.062 (3)	0.054 (3)	0.027 (6)	0.031 (2)	−0.003 (2)	0.000 (2)
C2	0.069 (3)	0.069 (3)	0.099 (5)	0.045 (4)	−0.0022 (16)	0.0022 (16)

Geometric parameters (Å, º)

N1—C1^i	1.452 (8)	C1—H1B	0.9884
N1—C1^ii	1.452 (8)	C2—C1^i	1.530 (11)
N1—C1^iii	1.452 (8)	C2—H2A	0.9757
N1—C1	1.452 (8)	C2—H2B	0.9664
N1—C1^iv	1.452 (8)	C2—H2C	0.9846
N1—C1^v	1.452 (8)	C2—H2D	0.9657
N1—H1	0.9 (2)	C2—H2E	0.9882
C1—C2	1.530 (11)	C2—H2F	0.9784
C1—H1A	0.9883
C1^i—N1—C1^iii	118.2 (3)	N1—C1—H1B	101.7
C1^ii—N1—C1	118.2 (3)	C2—C1—H1B	101.3
C1^i—N1—C1^iv	118.2 (3)	H1A—C1—H1B	105.7
C1^iii—N1—C1^iv	118.2 (3)	C1—C2—H2A	108.8
C1^ii—N1—C1^v	118.2 (3)	C1—C2—H2B	106.3
C1—N1—C1^v	118.2 (3)	H2A—C2—H2B	110.7
C1^i—N1—H1	97.7 (6)	C1—C2—H2C	111.9
C1^ii—N1—H1	97.7 (6)	H2A—C2—H2C	109.2
C1^iii—N1—H1	97.7 (6)	H2B—C2—H2C	109.9
C1—N1—H1	97.7 (6)	C1^i—C2—H2D	109.3
C1^iv—N1—H1	97.7 (5)	C1—C2—H2E	101.2
C1^v—N1—H1	97.7 (5)	H2D—C2—H2E	109.7
N1—C1—C2	128.9 (7)	C1^i—C2—H2F	106.4
N1—C1—H1A	108.1	H2D—C2—H2F	110.5
C2—C1—H1A	108.5	H2E—C2—H2F	108.6

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···I1	0.9 (2)	2.6 (2)	3.529 (11)	180