Bonding features in Appel's salt from the orbital-free quantum crystallographic perspective

Bonding properties in the crystal of 4,5-di­chloro-l,2,3-di­thia­zolium chloride (Appel's salt) were studied using a combination of single-crystal high-resolution X-ray diffraction data and the orbital-free quantum crystallography approach. A QTAIM-based topological model shows the proximity of S—C and S—N bonds to the sesquialteral type and establishes the low S—S bond order in the l,2,3-di­thia­zolium heterocycle. It is found that the electrostatic potential carries the traces of a common positive area on the junction of interatomic zero-flux surfaces of S1 and S2 atomic basins; meanwhile the exchange energy density per particle shows perfectly here two separate minima through which the two bond paths run. Thus, the pair intermolecular interactions Cl⁻...S1 and Cl⁻...S2 formed by the common chloride anion placed near the center of the S—S bond are categorized as chalcogen bonds.

Computing details

Cell refinement: SAINT V8.38A (Bruker AXS Inc., 2013) for (I). Data reduction: SAINT V8.38A (Bruker AXS Inc., 2013) for (I). Program(s) used to solve structure: SHELXT-2018/3 (Sheldrick, 2018) for (I). Program(s) used to refine structure: SHELXL2013/8 (Sheldrick, 2018) for (I); Volkov et al., (2006) for Appel_mult. Molecular graphics: Bruker SHELXTL (Bruker AXS Inc., 2013) for (I); Volkov et al., (2006) for Appel_mult. Software used to prepare material for publication: Volkov et al., (2006) for Appel_mult.

(I)

Crystal data

C2Cl2NS2·Cl	Dx = 2.088 Mg m^−3
Mr = 208.50	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, P212121	Cell parameters from 9877 reflections
a = 5.90947 (10) Å	θ = 2.7–39.7°
b = 10.22455 (16) Å	µ = 1.89 mm^−1
c = 10.97838 (18) Å	T = 100 K
V = 663.33 (2) Å^3	Block-like, dark brown
Z = 4	0.58 × 0.12 × 0.11 mm
F(000) = 408

Data collection

Bruker Quest D8 diffractometer with Photon III detector	12387 reflections with I > 2σ(I)
ω–scan	Rint = 0.024
Absorption correction: multi-scan SADABS-2016/2 - Bruker AXS area detector scaling and absorption correction	θmax = 71.6°, θmin = 2.7°
Tmin = 0.566, Tmax = 0.724	h = −14→15
102642 measured reflections	k = −26→27
12761 independent reflections	l = −29→29

Refinement

Refinement on F^2	0 restraints
Least-squares matrix: full	w = 1/[σ^2(Fo^2) + (0.0193P)^2 + 0.0166P] where P = (Fo^2 + 2Fc^2)/3
R[F^2 > 2σ(F^2)] = 0.014	(Δ/σ)max = 0.003
wR(F^2) = 0.040	Δρmax = 0.49 e Å^−3
S = 1.07	Δρmin = −0.55 e Å^−3
12761 reflections	Absolute structure: Flack x determined using 5383 quotients [(I+)-(I-)]/[(I+)+(I-)] (Parsons, Flack and Wagner, Acta Cryst. B69 (2013) 249-259).
73 parameters	Absolute structure parameter: 0.273 (7)

Special details

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

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

	x	y	z	Uiso*/Ueq
Cl1	0.28475 (3)	0.74344 (2)	0.60078 (2)	0.01886 (2)
Cl2	−0.03886 (2)	0.53741 (2)	0.75136 (2)	0.01531 (1)
Cl3	0.48426 (2)	0.08785 (2)	0.59885 (2)	0.01301 (1)
S1	0.27725 (2)	0.33636 (2)	0.67299 (2)	0.01203 (1)
S2	0.54906 (2)	0.37393 (2)	0.56445 (2)	0.01248 (1)
N1	0.51415 (6)	0.53003 (3)	0.55287 (3)	0.01376 (3)
C1	0.33891 (6)	0.57994 (3)	0.60914 (3)	0.01276 (4)
C2	0.19775 (6)	0.49364 (3)	0.67624 (3)	0.01212 (3)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cl1	0.02390 (4)	0.01003 (2)	0.02265 (4)	0.00335 (2)	0.00101 (4)	0.00118 (2)
Cl2	0.01380 (3)	0.01544 (3)	0.01668 (3)	0.00184 (2)	0.00185 (2)	−0.00338 (2)
Cl3	0.01313 (2)	0.01159 (2)	0.01431 (2)	0.00126 (2)	0.00119 (2)	0.00060 (2)
S1	0.01314 (3)	0.00975 (2)	0.01320 (2)	−0.00035 (2)	0.00160 (2)	−0.00013 (2)
S2	0.01325 (3)	0.00998 (2)	0.01422 (3)	0.00051 (2)	0.00215 (2)	−0.00003 (2)
N1	0.01559 (9)	0.01034 (6)	0.01534 (8)	−0.00005 (6)	0.00207 (7)	0.00064 (6)
C1	0.01502 (9)	0.00973 (7)	0.01352 (9)	0.00078 (6)	−0.00014 (7)	−0.00002 (6)
C2	0.01295 (8)	0.01117 (7)	0.01224 (8)	0.00074 (6)	0.00017 (7)	−0.00139 (6)

Geometric parameters (Å, º)

Cl1—C1	1.7045 (3)	S2—N1	1.6143 (3)
Cl2—C2	1.6838 (4)	N1—C1	1.3094 (5)
S1—C2	1.6757 (3)	C1—C2	1.4203 (5)
S1—S2	2.0366 (1)
C2—S1—S2	93.014 (13)	C2—C1—Cl1	121.80 (3)
N1—S2—S1	97.570 (13)	C1—C2—S1	114.87 (3)
C1—N1—S2	116.70 (3)	C1—C2—Cl2	125.21 (3)
N1—C1—C2	117.84 (3)	S1—C2—Cl2	119.89 (2)
N1—C1—Cl1	120.36 (3)

(Appel_mult)

Crystal data

a = Å	α = °
b = Å	β = °
c = Å	γ = °

Data collection

h = →	l = →
k = →

Refinement

Refinement on F^2	9426 reflections
Least-squares matrix: full	414 parameters
R[F^2 > 2σ(F^2)] = 0.009	0 restraints
wR(F^2) = 0.011	w2 = q/[s^2(Fo^2) + (0.01 P)^2 + 0.00 P + 0.00 + 0.00 sin(th)] where P = (0.3333 Fo^2 + 0.6667 Fc^2) q = 1.0
S = 1.40	(Δ/σ)max < 0.001

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

	x	y	z	Uiso*/Ueq
Cl(1)	0.28457 (7)	0.74324 (2)	0.60055 (4)	0.019
Cl(2)	−0.03844 (5)	0.53756 (3)	0.75118 (2)	0.016
Cl(3)	0.48423 (4)	0.08786 (2)	0.59881 (2)	0.013
S(1)	0.27720 (4)	0.33636 (2)	0.67291 (2)	0.012
S(2)	0.54893 (4)	0.37393 (2)	0.56454 (2)	0.013
N(1)	0.51412 (3)	0.529971 (16)	0.552909 (18)	0.014
C(1)	0.33882 (4)	0.580022 (17)	0.609172 (19)	0.013
C(2)	0.19767 (3)	0.493656 (18)	0.676274 (18)	0.012

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cl(1)	0.02510 (11)	0.01005 (6)	0.02313 (10)	0.00356 (6)	0.00106 (9)	0.00108 (6)
Cl(2)	0.01443 (7)	0.01575 (7)	0.01701 (7)	0.00192 (5)	0.00180 (6)	−0.00347 (6)
Cl(3)	0.01360 (6)	0.01152 (5)	0.01460 (6)	0.00132 (4)	0.00135 (5)	0.00060 (5)
S(1)	0.01368 (7)	0.00971 (5)	0.01347 (6)	−0.00036 (5)	0.00160 (5)	−0.00017 (5)
S(2)	0.01384 (7)	0.00994 (5)	0.01443 (6)	0.00054 (5)	0.00221 (5)	−0.00009 (5)
N(1)	0.01572 (5)	0.01029 (4)	0.01568 (5)	−0.00001 (3)	0.00242 (4)	0.00073 (3)
C(1)	0.01503 (5)	0.00968 (4)	0.01378 (5)	0.00083 (3)	0.00000 (4)	−0.00006 (4)
C(2)	0.01309 (5)	0.01107 (4)	0.01247 (4)	0.00079 (3)	0.00035 (4)	−0.00131 (3)