Redetermination of trimethyl­ammonium iodide at 93 K

The crystal structure of the title compound, C₃H₁₀N⁺·I⁻, originally determined by Sheldrick & Sheldrick [Acta Cryst. (1970), B26, 1334–1338], has been redetermined at 93 K. Both ions lie on a mirror plane. They form N—H...I hydrogen-bonded units in the crystal structure.

Key indicators

• Single-crystal X-ray study
• T = 93 K
• Mean [sigma](N-C) = 0.002 Å
• R factor = 0.010
• wR factor = 0.024
• Data-to-parameter ratio = 14.4

checkCIF/PLATON results

No syntax errors found



Alert level A
PLAT029_ALERT_3_A _diffrn_measured_fraction_theta_full Low .......       0.90

Author Response: ... Data collection was not a complete sphere because of instrument limitations; more than adequate redundant data was collected as indicated by final R factors.

Alert level C
REFLT03_ALERT_3_C  Reflection count < 95% complete
           From the CIF: _diffrn_reflns_theta_max           27.94
           From the CIF: _diffrn_reflns_theta_full          27.94
           From the CIF: _reflns_number_total                735
           TEST2: Reflns within _diffrn_reflns_theta_max
           Count of symmetry unique reflns          813
           Completeness (_total/calc)             90.41%
PLAT164_ALERT_4_C Nr. of Refined C-H H-Atoms in Heavy-At Struct...          5

   1 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   2 ALERT level C = Check and explain
   0 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
   2 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

---

Computing details

Data collection: SMART (Siemens, 2001); cell refinement: SMART; data reduction: SAINT (Siemens, 2001) and SADABS (Sheldrick, 1996); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia, 1997).

trimethylammonium iodide

Crystal data

C3H10N^+·I^−	F(000) = 176
Mr = 187.02	Dx = 1.969 Mg m^−3
Monoclinic, P21/m	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yb	Cell parameters from 1695 reflections
a = 5.5309 (7) Å	θ = 2.5–28.0°
b = 8.2737 (10) Å	µ = 4.94 mm^−1
c = 7.1000 (9) Å	T = 93 K
β = 103.801 (1)°	Block, colourless
V = 315.52 (7) Å^3	0.37 × 0.18 × 0.16 mm
Z = 2

Data collection

Bruker SMART CCD area-detector diffractometer	735 independent reflections
Radiation source: fine-focus sealed tube	730 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.011
Detector resolution: 8.192 pixels mm^-1	θmax = 27.9°, θmin = 3.0°
φ and ω scans	h = −6→7
Absorption correction: multi-scan (Blessing, 1995)	k = −10→10
Tmin = 0.304, Tmax = 0.454	l = −5→9
1741 measured reflections

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)] = 0.010	All H-atom parameters refined
wR(F^2) = 0.024	w = 1/[σ^2(Fo^2) + (0.0077P)^2 + 0.1167P] where P = (Fo^2 + 2Fc^2)/3
S = 1.23	(Δ/σ)max = 0.001
735 reflections	Δρmax = 0.34 e Å^−3
51 parameters	Δρmin = −0.25 e Å^−3
0 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.045 (2)

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	0.03818 (2)	0.2500	0.203342 (18)	0.01281 (8)
N1	0.5629 (3)	0.2500	0.7777 (3)	0.0133 (3)
C1	0.7161 (4)	0.2500	0.6300 (3)	0.0183 (4)
C2	0.4065 (3)	0.10057 (18)	0.7625 (2)	0.0163 (3)
H1	0.607 (5)	0.2500	0.507 (4)	0.015 (6)*
H2	0.815 (4)	0.155 (2)	0.647 (3)	0.022 (5)*
H3	0.662 (6)	0.2500	0.882 (5)	0.022 (7)*
H4	0.298 (3)	0.100 (2)	0.639 (3)	0.015 (4)*
H5	0.310 (3)	0.105 (2)	0.863 (3)	0.016 (5)*
H6	0.521 (4)	0.006 (3)	0.779 (3)	0.021 (5)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
I1	0.01116 (10)	0.01505 (10)	0.01131 (10)	0.000	0.00088 (5)	0.000
N1	0.0097 (8)	0.0177 (9)	0.0112 (9)	0.000	0.0002 (7)	0.000
C1	0.0143 (10)	0.0242 (11)	0.0180 (11)	0.000	0.0069 (9)	0.000
C2	0.0158 (7)	0.0148 (7)	0.0177 (7)	−0.0007 (6)	0.0027 (6)	0.0013 (6)

Geometric parameters (Å, º)

N1—C1	1.498 (3)	C1—H2	0.95 (2)
N1—C2	1.4977 (18)	C2—H4	0.94 (2)
N1—C2^i	1.4977 (18)	C2—H5	0.99 (2)
N1—H3	0.81 (3)	C2—H6	1.00 (2)
C1—H1	0.94 (3)
C1—N1—C2	111.26 (11)	H1—C1—H2	110.2 (15)
C1—N1—C2^i	111.26 (11)	N1—C2—H4	107.6 (11)
C2—N1—C2^i	111.27 (17)	N1—C2—H5	108.5 (11)
C1—N1—H3	105 (2)	H4—C2—H5	110.0 (16)
C2—N1—H3	108.7 (11)	N1—C2—H6	107.6 (12)
C2^i—N1—H3	108.7 (11)	H4—C2—H6	110.5 (16)
N1—C1—H1	107.9 (17)	H5—C2—H6	112.3 (16)
N1—C1—H2	108.4 (13)

Symmetry code: (i) x, −y+1/2, z.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H3···I1^ii	0.81 (3)	2.70 (3)	3.500 (2)	173 (3)

Symmetry code: (ii) x+1, y, z+1.