Conformational preference of chlorothioformate species: molecular structure of ethyl chlorothioformate, ClC(O)SCH₂CH₃, in the solid phase and NBO analysis

The molecular structure of ethyl chlorothioformate, ClC(O)SCH₂CH₃, has been investigated in the solid phase by X-ray diffraction analysis at low temperature using a miniature zone-melting procedure and IR laser radiation. The crystalline solid consists exclusively of molecules with the synperiplanar conformation with respect to the C=O double bond and the S—C single bond, and gauche orientation of the ethyl group (syn-gauche). These results coincide with previous studies devoted to gas-phase conformational properties. The conformational preference for the ClC(O)SY (Y = Cl, CF₃, CH₃ and CH₂CH₃) series of molecules was rationalized using the natural bond orbital (NBO) scheme. It was found that both resonance (mesomeric) and anomeric (hyperconjugation) intermolecular charge-transfer interactions are important for describing the syn ↔ anti equilibrium, also illustrating the effect of electronegativity of the substituent in the conformation preference of the ClC(O)S— moiety. On the basis of the atoms in molecules (AIM) theory, intermolecular interactions have been characterized in the B3LYP/6-31G** periodic boundary electron density.

Computing details

Data collection: BRUKER AXS SMART Vers.5.054; cell refinement: BRUKER AXS SAINT Vers.6.45A; data reduction: BRUKER AXS SAINT Vers.6.45A; program(s) used to solve structure: BRUKER D8 KAPPA APEX 2 Vers. 3.0-2009; program(s) used to refine structure: BRUKER AXS SHELXTL (c) 2008 / Vers. 2008/4; molecular graphics: BRUKER AXS SHELXTL (c) 2008 / Vers. 2008/4; software used to prepare material for publication: BRUKER AXS SHELXTL (c) 2008 / Vers. 2008/4.

ethyl chlorothioformate

Crystal data

C3H5ClOS	F(000) = 256
Mr = 124.58	Dx = 1.468 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 9.4763 (6) Å	Cell parameters from 1913 reflections
b = 5.8288 (4) Å	θ = 3.5–28.3°
c = 11.0764 (7) Å	µ = 0.91 mm^−1
β = 112.853 (1)°	T = 183 K
V = 563.79 (6) Å^3	Cylindric, colourless
Z = 4	0.3 × 0.3 × 0.3 mm

Data collection

Siemens SMART CCD area detector system diffractometer	1241 independent reflections
Radiation source: fine-focus sealed tube	1182 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.013
Detector resolution: 512 pixels mm^-1	θmax = 28.3°, θmin = 2.3°
ω data collection at 0.3 deg scan width, with chi = 0	h = −11→12
Absorption correction: multi-scan BRUKER AXS SMART APEX 2 Vers. 3.0-2009 R.H. Blessing, Acta Cryst. (1995) A51 33-38	k = −7→7
Tmin = 0.93, Tmax = 0.97	l = −14→7
2014 measured reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.018	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.050	H-atom parameters constrained
S = 1.07	w = 1/[σ^2(Fo^2) + (0.0234P)^2 + 0.1192P] where P = (Fo^2 + 2Fc^2)/3
1241 reflections	(Δ/σ)max = 0.001
55 parameters	Δρmax = 0.24 e Å^−3
0 restraints	Δρmin = −0.15 e Å^−3

Special details

Experimental. The crystallization was performed on the diffractometer at a temperature of 183 K with a miniature zone melting procedure using focused infrared-laser-radiation according to: R. Boese, M·Nussbaumer, "In Situ crystallization Techniques", in: "Organic Crystal Chemistry", Ed. D·W. Jones, Oxford University Press, Oxford,England, (1994) 20–37

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. Treatment of hydrogen atoms Riding model on idealized geometrics with the 1.2 fold (1.5 fold for methyl groups) isotropic displacement parameters of the equivalent U^ij of the corresponding carbon atom

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

	x	y	z	Uiso*/Ueq
S1	0.81176 (3)	0.18119 (4)	0.38405 (3)	0.03465 (9)
Cl1	0.88744 (4)	−0.20949 (5)	0.26225 (3)	0.04247 (10)
O1	0.73701 (11)	−0.24618 (14)	0.41354 (9)	0.0433 (2)
C1	0.79640 (12)	−0.11444 (18)	0.36717 (10)	0.0304 (2)
C2	0.70880 (14)	0.22534 (18)	0.49007 (11)	0.0353 (2)
H2A	0.7449	0.3636	0.5396	0.042*
H2B	0.7302	0.1001	0.5509	0.042*
C3	0.53753 (14)	0.2430 (2)	0.41505 (13)	0.0433 (3)
H3A	0.5148	0.3716	0.3534	0.065*
H3B	0.4874	0.2684	0.4764	0.065*
H3C	0.4994	0.1002	0.3666	0.065*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
S1	0.03849 (19)	0.02769 (13)	0.04127 (17)	−0.00359 (9)	0.01934 (14)	0.00177 (9)
Cl1	0.0444 (2)	0.04292 (16)	0.04572 (18)	0.00156 (11)	0.02363 (16)	−0.00511 (11)
O1	0.0564 (5)	0.0306 (4)	0.0508 (5)	−0.0054 (3)	0.0295 (4)	0.0025 (3)
C1	0.0288 (5)	0.0309 (5)	0.0293 (5)	−0.0002 (4)	0.0089 (4)	0.0008 (4)
C2	0.0443 (7)	0.0300 (5)	0.0327 (5)	0.0011 (4)	0.0163 (5)	−0.0003 (4)
C3	0.0412 (8)	0.0421 (6)	0.0491 (7)	0.0038 (5)	0.0204 (6)	0.0020 (5)

Geometric parameters (Å, º)

S1—C1	1.7333 (11)	O1—C1	1.1810 (13)
S1—C2	1.8131 (11)	C2—C3	1.5125 (18)
Cl1—C1	1.7834 (10)
C1—S1—C2	99.62 (5)	S1—C1—Cl1	109.73 (5)
O1—C1—S1	129.33 (9)	C3—C2—S1	112.73 (8)
O1—C1—Cl1	120.95 (9)
C2—S1—C1—O1	−0.78 (13)	C1—S1—C2—C3	−84.73 (9)
C2—S1—C1—Cl1	179.01 (6)