The use of Mo Kα radiation in the assignment of the absolute configuration of light-atom molecules; the importance of high-resolution data

Recent studies have confirmed the usefulness of the Hooft and Parsons methodologies for determination of the absolute crystal structures of enantiopure light-atom compounds using Cu Kα radiation. While many single-crystal diffractometers used for small-molecule structure determination are equipped with molybdenum anodes, use of data from such instruments for the absolute structure determination of light-atom crystal structures is rarely documented and has often been found to be unsuccessful. The Hooft and Parsons methodologies have been applied to 44 data sets obtained from single crystals containing light-atom molecules of known chirality using Mo Kα radiation. Several factors influencing the calculation of accurate and precise values for the Hooft and Parsons parameters obtained from these data sets have been identified, the inclusion of high-resolution diffraction data being particularly important. The correct absolute structure was obtained in all cases, with the standard uncertainties of the final absolute structure parameters below 0.1 for the great majority.

Computing details

Data collection: Bruker APEX2 v2011.4-0; cell refinement: Bruker APEX2 v2011.4-0; data reduction: Bruker SAINT V7.60A; program(s) used to solve structure: Sir2011; program(s) used to refine structure: SHELXL2012 (Sheldrick, 2012); molecular graphics: Bruker SHELXTL; software used to prepare material for publication: Bruker SHELXTL.

Figures

(I)

Crystal data

C3H7NO2	Dx = 1.405 Mg m^−3
Mr = 89.10	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, P212121	Cell parameters from 7420 reflections
a = 5.7890 (8) Å	θ = 7.5–62.4°
b = 5.9387 (7) Å	µ = 0.12 mm^−1
c = 12.2516 (14) Å	T = 100 K
V = 421.20 (9) Å^3	Block, colourless
Z = 4	0.4 × 0.4 × 0.3 mm
F(000) = 192

Data collection

Kappa 4-axis goniometer bruker-nonius diffractometer	6425 independent reflections
Radiation source: Rotating anode X-ray tube, Bruker-Nonius FR 591	6209 reflections with I > 2σ(I)
Multilayer Montel 200 mirrors monochromator	Rint = 0.026
Detector resolution: 512 pixels mm^-1	θmax = 62.7°, θmin = 7.5°
Fullsphere data collection, phi and ω scans	h = −13→12
Absorption correction: empirical (using intensity measurements) SADABS Version 2008/1 Bruker-Nonius Blessing, Acta Cryst. (1995) A51 33-38	k = −14→14
Tmin = 0.743, Tmax = 0.966	l = −30→30
31341 measured reflections

Refinement

Refinement on F^2	Hydrogen site location: difference Fourier map
Least-squares matrix: full	H-atom parameters not refined
R[F^2 > 2σ(F^2)] = 0.025	w = 1/[σ^2(Fo^2) + (0.040P)^2 + 0.0029P] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.066	(Δ/σ)max = 0.002
S = 1.18	Δρmax = 0.49 e Å^−3
6425 reflections	Δρmin = −0.23 e Å^−3
55 parameters	Absolute structure: Flack x determined using 2644 quotients [(I+)-(I-)]/[(I+)+(I-)] (Parsons and Flack (2004), Acta Cryst. A60, s61).
0 restraints	Absolute structure parameter: 0.05 (8)

Special details

Experimental. It should be noted that the e.s.d.'s of the cell dimensions are probably too low; they should be multiplied by a factor of 2 to 10

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
O1	−0.26127 (4)	0.94249 (4)	0.81575 (2)	0.01282 (3)
O2	−0.12499 (4)	1.22736 (4)	0.91615 (2)	0.01287 (3)
N1	0.31650 (4)	1.14850 (3)	0.86234 (2)	0.01033 (3)
C1	−0.10016 (4)	1.05514 (4)	0.85909 (2)	0.00919 (3)
C2	0.14545 (4)	0.96797 (4)	0.83885 (2)	0.00930 (3)
C3	0.19665 (5)	0.76231 (5)	0.90917 (2)	0.01349 (4)
H2	0.1624	0.9309	0.7617	0.021*
H11	0.3067	1.1953	0.9341	0.022*
H12	0.4527	1.0920	0.8541	0.028*
H13	0.2945	1.2591	0.8221	0.021*
H31	0.1957	0.8005	0.9881	0.026*
H32	0.0848	0.6442	0.8952	0.023*
H33	0.3491	0.7020	0.8936	0.022*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.00792 (6)	0.01600 (6)	0.01453 (6)	−0.00075 (5)	−0.00098 (4)	−0.00346 (5)
O2	0.01146 (7)	0.01409 (6)	0.01306 (5)	0.00160 (5)	0.00097 (4)	−0.00414 (4)
N1	0.00808 (6)	0.01183 (5)	0.01107 (5)	−0.00043 (4)	−0.00003 (4)	−0.00042 (4)
C1	0.00762 (6)	0.01138 (6)	0.00858 (5)	0.00061 (4)	0.00000 (4)	−0.00038 (4)
C2	0.00765 (6)	0.01098 (6)	0.00928 (5)	0.00046 (4)	−0.00003 (4)	−0.00090 (4)
C3	0.01147 (8)	0.01255 (7)	0.01646 (8)	0.00113 (6)	−0.00050 (6)	0.00241 (6)

Geometric parameters (Å, º)

O1—C1	1.2647 (3)	C1—C2	1.5333 (4)
O2—C1	1.2472 (3)	C2—C3	1.5238 (4)
N1—C2	1.4876 (3)
O2—C1—O1	125.75 (2)	N1—C2—C3	109.81 (2)
O2—C1—C2	118.32 (2)	N1—C2—C1	110.04 (2)
O1—C1—C2	115.93 (2)	C3—C2—C1	111.07 (2)
O2—C1—C2—N1	−18.27 (3)	O2—C1—C2—C3	103.54 (3)
O1—C1—C2—N1	162.01 (2)	O1—C1—C2—C3	−76.19 (3)