M. Dhanalakshmi, C. Balakrishnan, S.R. Ahamed et al.
Journal of Molecular Structure 1237 (2021) 130421
Fig. 9. Views of the structure (2), showing the atom-numbering schemes. Displacement ellipsoid is shown at the 50% probability level.
The ORTEP (50% probability level) and packing diagram of (1)
are shown in Fig. 6a. The 1,2,3,4-tetrahydroquinolinium cations
cap the central hexachloro anion on both sides of the unit cell
are shown in Fig. 6b. The asymmetric unit of (1), contains one
1,2,3,4-tetrahydroquinolinium cation and half a [SnCl6]2- anion, the
anion lying on an inversion centre. The inversion centre gener-
ates a SnCl6 octahedron, in which the three unique Sn-Cl bond
inorganic layers extending column arrangement is demonstrated in
The compound shows extensive hydrogen-bonding interactions.
The crystal packing in (2) is controlled by the hydrogen bond,
in extension to coulombic forces. Nitrogen and carbon atoms
in the 1,2,3,4-tetrahydroquinolinium cations act as C H•••Br and
–
N H•••Br hydrogen-bond donor and forms four simple and one bi-
–
˚
lengths are 2.4234(3), 2.4320(3) and 2.4387(3) A (Table S3; Fig.
furcated hydrogen bonds with SnBr6 octahedra (Fig. 11) (Table 4b).
The corresponding distances of the donor accepter bifurcated
bonds C(9)-H(9A)•••Br(1) and C(9)-H(9A)•••Br(2) are 3.699(3) and
S3a) and the cis Cl-Sn-Cl bond angles range from 89.345(2) to
90.656(12)° (Table S4; Fig. S3b), indicating only the slight distor-
tion from ideal octahedral geometry. The bond distances are sim-
ilar to those found in other octahedral Sn(IV) compounds [19].
The compound (1) shows extensive hydrogen-bonding interactions.
The 1,2,3,4-tetrahydroquinolinium cations form layers parallel and
[SnCl6]2− octahedra alternate with the cationic layers along the b-
˚
3.677(3) A respectively (Fig. 11a). Fig. 12 displays the π•••π and
C H•••π interactions for (2). Within the organic layers, adjacent
–
aromatic rings are separated by a centroid-centroid distance of
˚
>4.3 A, clearly too far to consider as a π-stacking interaction. The
aromatic rings formed two C H•••π interactions with the corre-
–
˚
˚
sponding distances, 3.808 A (C(7)-H(7A)•••π) and 4.004 A (C(7)-
H(7B)•••π) and their corresponding angles are 154.08 and 128.16°
respectively.
The crystal packing in (1) is controlled by the classical hydro-
gen bonds, in extension to coulombic forces. Nitrogen and carbon
atoms in 1,2,3,4-tetrahydroquinolinium cation act as C H•••Cl and
–
N H•••Cl hydrogen-bond donor and forms one simple and two
–
3.7. Bond valence sum analysis (BVS)
bifurcated hydrogen bonds with SnCl6 octahedra (Table 4a). The
corresponding distances of donor accepter bifurcated bonds N(1)-
H(1A)•••Cl(1), N(1)-H(1A)•••Cl(2), N(1)-H(1B)•••Cl(1) and N(1)-
H(1B)•••Cl(3) are 3.5116(11), 3.2789(11), 3.4047(11) and 3.3457(12)
The valence number of the central metal atom is determined by
the Bond valence sum (BVS) analysis from the experimentally de-
rived bond distances [51]. BVS calculations are carried out by the
bond distances obtained from the single-crystal X-ray diffraction
analysis. Therefore, BVS calculation indirectly provides the way to
evident any imperfections observed from the crystal structures de-
termined [52]. This calculation depends on the Rij value for an i–j
bond which is primarily ionic [53,54]. In a compound, the oxida-
tion state of a central atom ‘i’ bonded to ‘j’ match up to the bond
valence, V and the total valence of the central atom is its oxidation
state,
˚
A respectively (Fig. 7b). Fig. 8 displays the π•••π and C H•••π
–
interactions for (1). Within the organic layers, adjacent aromatic
˚
rings are separated by a centroid-centroid distance of >4.4 A,
clearly too far to consider as a π-stacking interaction. The aromatic
rings formed two C H•••π interactions with corresponding dis-
–
˚
˚
tances of 3.757 A (C(7)-H(7A)•••π) and 3.921 A (C(7)-H(7B)•••π)
respectively.
The molecular geometry and atomic numbering schemes for
(2) are demonstrated in Fig. 9. The asymmetric unit of (2), con-
tains one 1,2,3,4-tetrahydroquinolinium cation and half a [SnBr6]2-
anion, the anion lying on an inversion centre. The inversion cen-
tre generates an SnBr6 octahedron, in which the three unique Sn-
ꢃ ꢁ
V = ꢁvij = exp Ro − −Rij /b
where Ro is the value which is reported for a large number of ionic
compounds [55] and Rij is the experimentally determined bond
distance. The constant b can be assumed to be 0.37 [56]. Bond va-
lence sums of (1) and (2) are 3.94 and 3.93 respectively (Table S6),
which proved the formal oxidation state of tin is found to be 4+
unequivocally.
˚
Br bond lengths are 2.5960(4), 2.5961(4) and 2.6089(4) A (Ta-
ble S3; Fig. S4a) and the cis Br-Sn-Br bond angles range from
89.509(11)° to 90.491(11)° (Table S4; Fig. S4b), indicating only the
slight distortion from ideal octahedral geometry. The bond dis-
tances are similar to those found in other octahedral Sn(IV) com-
pounds [19]. The 1,2,3,4-tetrahydroquinolinium cations capping the
central hexabromo anion on both sides of the unit cell are shown
in Fig. 10a. The crystal structure consists of alternating organic and
3.8. Continuous symmetry measure (CSM)
CSM computes the distance of a given structure from the de-
sired ideal symmetry or a reference shape [57-60]. Various geome-
10