Crystal structure and Hirshfeld surface analysis of a zinc xanthate complex containing the 2,2'-bi-pyridine ligand.

In the title compound, (2,2'-bi-pyridine-κ2 N,N')bis-(2-meth-oxy-ethyl xanthato-κS)zinc(II), [Zn(C4H7O2S2)2(C10H8N2)], the ZnII ion is coordinated to two N atoms of the 2,2'-bi-pyridine ligand and two S atoms from two 2-meth-oxy-ethyl xanthate ligands. The ZnII ion lies on a crystallographic twofold rotation axis and has distorted tetra-hedral coordination geometry. In the crystal, mol-ecules are linked by weak C-H⋯O hydrogen bonds, forming supramolecular chains propagating along the a-axis direction. Weak intra-molecular C-H⋯S hydrogen bonds are also observed. The inter-molecular contacts in the crystal were further analysed using Hirshfield surface analysis, which indicates that the most significant contacts are H⋯H (36.3%), followed by S⋯H/H⋯S (24.7%), C⋯H/H⋯C (15.1%), O⋯H/H⋯O (14.4%), N⋯H/H⋯N (4.1%) and C⋯C (2.9%). © Qadir et al. 2019.

Chemical context

Xanthates (di­thio­carbonates, ROCS2 −) have attracted the attention of scientific groups of researchers due to their diverse applications. Metal xanthates have been used as single-source precursors to metal sulfide materials (Kociok-Köhn et al., 2015 ▸). It was reported that metal xanthates have cytotoxic activity on human cancer cells (Efrima et al., 2003 ▸; Friebolin et al., 2005 ▸). Cellulose xanthate have been used for the column separation of alcohols by chromatographic methods (Friebolin et al., 2004 ▸). Zinc(II) xanthate complexes have a tetra­hedral geometry, while zinc(II) xanthate complexes with neutral bidentate nitro­gen donor ligands are either strongly distorted octa­hedral or tetra­hedral. In our previous work, ZnII 2-meth­oxy­ethylxanthate with N,N,N′,N′-tetra­methyl­ethyl­ene­di­amine was synthesized, structurally characterized and studied by density functional theory (Qadir et al., 2019 ▸). The complex showed a tetra­hedral environment around metal center and the HOMO–LUMO band gap was 3.9 eV. Aromatic heterocyclic nitro­gen donor ligands have been used by researchers to prepare mixed-ligand complexes of transition metals with supra­moleculer architectures. In this work, the synthesis and crystal structure of a zinc(II) 2-meth­oxy­ethyl xanthate involving 2,2′-bi­pyridine is reported. Hirshfeld surface analysis was used to further investigate the inter­molecular inter­actions.

Structural commentary

The title complex (Fig. 1 ▸) comprises one ZnII ion, one 2,2′-bi­pyridine ligand and two 2-meth­oxy­ethyl xanthate ligands. The ZnII ion is coordinated to two N atoms of the 2,2′-bi­pyridine ligand and two S atoms from two 2-meth­oxy­ethyl xanthate ligands in a distorted tetra­hedral environment and lies on a crystallographic twofold rotation axis. The Zn—N and Zn—S bond lengths are 2.083 (5) and 2.295 (2) Å, respectively, whereas the bond angles around the central ZnII ion are in the range 78.7 (3)–126.64 (10)° (Table 1 ▸). The bond lengths and angles of the ZnN2S2 coordination units correspond to those in the structures of mixed-ligand ZnII coordination compounds (see; Database Survey). The C—O bond lengths range from 1.346 (8) to 1.453 (8) Å although all of the C—O bonds show single-bond character. In the {S2C} part of the xanthate ligands, the C1—S1 distance is 1.727 (7) Å, which is typical of a single bond whereas the C1—S2 distance of 1.652 (7) Å is typical of a carbon-to-sulfur double bond. The C—N and C—C bond lengths in 2,2′-bi­pyridine are normal for 2-substituted pyridine derivatives (Strotmeyer et al., 2003 ▸; Iskenderov et al., 2009 ▸; Golenya et al., 2012 ▸).

Figure 1

The mol­ecular structure of the title complex, with the atom labelling. Displacement ellipsoids are drawn at the 50% probability level. Symmetry code: (i) 1 − x, y,  − z.

Table 1

Selected geometric parameters (Å, °)

Zn1—S1	2.2954 (18)	Zn1—N1	2.083 (5)
S1i—Zn1—S1	126.64 (10)	N1—Zn1—S1	100.54 (15)
N1i—Zn1—S1	120.78 (15)	N1—Zn1—N1i	78.7 (3)

Symmetry code: (i) .

Supra­molecular features

The crystal packing of the title compound (Fig. 2 ▸) features inter­molecular C8—H8⋯O5ii hydrogen bonds (Table 2 ▸), which connect the mol­ecules into supramolecular chains propagating along the a-axis direction. Weak intra­molecular C—H⋯S hydrogen bonds are also observed.

Figure 2

A view of the crystal packing of the title complex. Dashed lines denote the inter­molecular hydrogen bonds (Table 2 ▸). Symmetry codes: (i)  + x,  − y,  + z, (ii) 1 − x, y,  − z, (iii)  − x,  − y, −z.

Table 2

Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C8—H8⋯O5i	0.95	2.51	3.246 (9)	134
C7—H7⋯S2ii	0.95	2.90	3.552 (7)	127

Symmetry codes: (i) ; (ii) .

Hirshfeld surface analysis

The Hirshfeld surface analysis and the associated two-dimensional fingerprint plots were performed with CrystalExplorer17.5 (Turner et al., 2017 ▸). The Hirshfeld surface of the title complex is shown in Fig. 3 ▸ a and 3b. The inter­molecular inter­actions are represented using different colours, red indicating distances closer than the sum of the van der Waals radii, white indicating distances near the van der Waals radii separation, and blue indicating distances longer than the van der Waals radii (McKinnon et al., 2007 ▸). The weak C—H⋯O and C—H⋯S hydrogen bonding in the crystal of the title complex are represented as red spots on d. Selected two-dimensional fingerprint plots are shown in Fig. 4 ▸ for all contacts as well as those delineated into H⋯H, S⋯H/H⋯S and C⋯H/H⋯C contacts, whose percentage contribution is also given. H⋯H inter­molecular contacts make the highest percentage contribution (36.3%), a result of the prevalence of hydrogen from the organic ligands. The S⋯H/H⋯S and O⋯H/H⋯O inter­molecular contacts are due to the attractive C—H⋯S and C—H⋯O hydrogen-bonding inter­actions and make percentage contributions of 24.7 and 14.4%, respectively, indicating these to be the dominant stabilizing inter­actions in this crystal. In addition, C⋯H/H⋯C contacts contribute 15.1% to the Hirshfeld surface. The small percentage contributions from the other different inter­atomic contacts to the Hirshfeld surfaces are as follows: N⋯H/H⋯N (4.1%), C⋯C (2.9%), S⋯S (1.1%), S⋯O/O⋯S (0.8%) and S⋯C/C⋯S (0.3%).

Figure 3

The Hirshfeld surfaces mapped over d norm in the range −0.1353 to +1.0127 (arbitrary units) for visualizing the weak inter­molecular (a) C—H⋯O and (b) C—H⋯S hydrogen bonding.

Figure 4

Hirshfeld surface fingerprint plots for the H⋯H, S⋯H/H⋯S, C⋯H/H⋯C and N⋯H/H⋯N contacts of the title complex.

Database survey

A search of the Cambridge Structural Database (CSD, version 5.40, update of February 2019; Groom et al., 2016 ▸) for compounds related to the title complex revealed five hits: (2,2′-dipyrid­yl)bis­(butylxanthato)zinc(II) (DIFBOK; Klevtsova et al., 2006 ▸), (2,2′-bi­pyridine)(O-n-propyl­dithio­carbo­n­ato-κ2 S,S′)(O-n-propyl­dithio­carbonato-S)zinc(II) (IGUGUO; Jeremias et al., 2014 ▸), (2,2′-bi­pyridine)-bis­(O-iso­prop­yl­xan­thato)zinc(II) and (2,2′-bi­pyridine)­bis­(O-iso­butyl­xan­th­ato)zinc(II) (with refcodes MUJJOQ and MUJJUW, respectively; Klevtsova et al., 2002 ▸) and (2,2′-bipyrid­yl)bis­(ethyl­xan­th­ato)zinc(II) (WITLAM; Glinskaya et al., 2000 ▸). All of these complexes except IGUGUO have tetra­hedral environments around the metal center. The Zn—N and Zn—S bond lengths range from 2.065 to 2.147 Å and 2.284 to 2.341 Å, respectively. The Zn—N and Zn—S bond lengths in the title complex [2.083 (5) and 2.295 (2) Å, respectively] fall within these limits. The structure with refcode IGUGUO has a distorted trigonal–bipyramidal coordination environment.

Synthesis and crystallization

To a hot solution of Zn(CH3CO2). 2H2O (10 mmol, 2.20 g) in 2-meth­oxy­ethanol, was added a hot solution of 2,2′-bipy (10 mmol, 1.56 g) in 2-meth­oxy­ethanol. A hot solution of potassium 2-meth­oxy­ethylxanthate (20 mmol, 3.81 g) in 2-meth­oxy­ethanol was added under stirring. Colourless crystals were formed after 30 minutes. The crystals were washed with small amounts of 2-meth­oxy­ethanol and water and air-dried.

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 3 ▸. The C-bound H atoms were positioned geometrically and refined using a riding model, with C—H = 0.95, 0.98 and 0.99 Å with U iso(H) = 1.5U eq(C) for methyl H atoms and 1.2U eq(C) otherwise. The crystal was a weak diffractor (I/σ at 0.81 resolution was 5.1) and refinedas a two-component twin with HKLF 4 data (twin law −1 0 0 0 − 1 0 0 0 − 1) but this had little effect. The anisotropy of N1 was restrained with ISOR 0.01 0.02 in SHELXL (Sheldrick, 2015 ▸).

Table 3

Experimental details

Crystal data
Chemical formula	[Zn(C4H7O2S2)2(C10H8N2)]
M r	523.98
Crystal system, space group	Monoclinic, C2/c
Temperature (K)	100
a, b, c (Å)	22.869 (4), 8.3212 (12), 12.5627 (19)
β (°)	115.348 (4)
V (Å3)	2160.5 (6)
Z	4
Radiation type	Mo Kα
μ (mm−1)	1.55
Crystal size (mm)	0.42 × 0.36 × 0.04
Data collection
Diffractometer	Bruker APEXII CCD
Absorption correction	Multi-scan (SADABS; Bruker, 2009 ▸)
T min, T max	0.599, 0.745
No. of measured, independent and observed [I > 2σ(I)] reflections	11173, 2119, 1954
R int	0.061
(sin θ/λ)max (Å−1)	0.618
Refinement
R[F 2 > 2σ(F 2)], wR(F 2), S	0.087, 0.155, 1.43
No. of reflections	2119
No. of parameters	134
No. of restraints	6
H-atom treatment	H-atom parameters constrained
Δρmax, Δρmin (e Å−3)	0.55, −1.00

Computer programs: APEX2 and SAINT (Bruker, 2009 ▸), SHELXS (Sheldrick, 2008 ▸), SHELXL (Sheldrick, 2015 ▸) and OLEX2 (Dolomanov et al., 2009 ▸).

Crystal structure: contains datablock(s) I. DOI: 10.1107/S2056989019014968/lh5934sup1.cif

Structure factors: contains datablock(s) I. DOI: 10.1107/S2056989019014968/lh5934Isup2.hkl

CCDC references: 1424075, 1424075

Additional supporting information: crystallographic information; 3D view; checkCIF report

[Zn(C4H7O2S2)2(C10H8N2)]	F(000) = 1080
Mr = 523.98	Dx = 1.611 Mg m−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
a = 22.869 (4) Å	Cell parameters from 2844 reflections
b = 8.3212 (12) Å	θ = 3.0–25.4°
c = 12.5627 (19) Å	µ = 1.55 mm−1
β = 115.348 (4)°	T = 100 K
V = 2160.5 (6) Å3	Plate, colourless
Z = 4	0.42 × 0.36 × 0.04 mm

Bruker APEXII CCD diffractometer	1954 reflections with I > 2σ(I)
φ and ω scans	Rint = 0.061
Absorption correction: multi-scan (SADABS; Bruker, 2009)	θmax = 26.1°, θmin = 2.6°
Tmin = 0.599, Tmax = 0.745	h = −28→28
11173 measured reflections	k = −9→10
2119 independent reflections	l = −14→15

Refinement on F2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.087	H-atom parameters constrained
wR(F2) = 0.155	w = 1/[σ2(Fo2) + 39.0236P] where P = (Fo2 + 2Fc2)/3
S = 1.43	(Δ/σ)max < 0.001
2119 reflections	Δρmax = 0.55 e Å−3
134 parameters	Δρmin = −1.00 e Å−3
6 restraints

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.

Refinement. Refined as a 2-component inversion twin.

	x	y	z	Uiso*/Ueq
Zn1	0.5000	0.63086 (13)	0.2500	0.0085 (3)
S1	0.44329 (8)	0.5070 (2)	0.33978 (16)	0.0164 (4)
S2	0.36008 (9)	0.4541 (2)	0.08028 (17)	0.0208 (4)
O2	0.3340 (2)	0.3748 (7)	0.2598 (4)	0.0203 (11)
O5	0.2155 (2)	0.4123 (6)	0.2833 (4)	0.0193 (11)
N1	0.5396 (3)	0.8245 (6)	0.3634 (5)	0.0101 (11)
C1	0.3750 (3)	0.4405 (8)	0.2208 (6)	0.0153 (15)
C3	0.2717 (3)	0.3151 (9)	0.1750 (6)	0.0186 (16)
H3A	0.2775	0.2208	0.1325	0.022*
H3B	0.2481	0.3996	0.1169	0.022*
C4	0.2350 (4)	0.2688 (9)	0.2455 (7)	0.0192 (16)
H4A	0.1966	0.2038	0.1964	0.023*
H4B	0.2630	0.2037	0.3146	0.023*
C6	0.1815 (4)	0.3775 (11)	0.3521 (7)	0.0289 (19)
H6A	0.1441	0.3094	0.3067	0.043*
H6B	0.1666	0.4780	0.3731	0.043*
H6C	0.2102	0.3211	0.4240	0.043*
C7	0.5764 (3)	0.8146 (9)	0.4798 (6)	0.0165 (15)
H7	0.5905	0.7116	0.5138	0.020*
C8	0.5948 (4)	0.9481 (9)	0.5521 (6)	0.0191 (16)
H8	0.6204	0.9372	0.6345	0.023*
C9	0.5751 (4)	1.0972 (9)	0.5021 (7)	0.0214 (17)
H9	0.5874	1.1913	0.5494	0.026*
C10	0.5371 (3)	1.1084 (8)	0.3815 (7)	0.0189 (16)
H10	0.5229	1.2103	0.3455	0.023*
C11	0.5204 (3)	0.9708 (8)	0.3151 (6)	0.0113 (14)

	U11	U22	U33	U12	U13	U23
Zn1	0.0137 (6)	0.0030 (5)	0.0118 (6)	0.000	0.0084 (4)	0.000
S1	0.0169 (9)	0.0160 (9)	0.0181 (9)	−0.0021 (7)	0.0091 (7)	0.0031 (7)
S2	0.0285 (10)	0.0198 (10)	0.0198 (10)	−0.0027 (8)	0.0158 (8)	−0.0026 (8)
O2	0.018 (3)	0.022 (3)	0.023 (3)	−0.002 (2)	0.011 (2)	0.003 (2)
O5	0.022 (3)	0.016 (3)	0.023 (3)	−0.001 (2)	0.013 (2)	0.002 (2)
N1	0.016 (3)	0.003 (3)	0.017 (3)	−0.004 (2)	0.011 (2)	−0.004 (2)
C1	0.019 (4)	0.007 (3)	0.022 (4)	0.004 (3)	0.011 (3)	0.004 (3)
C3	0.020 (4)	0.019 (4)	0.017 (4)	−0.006 (3)	0.008 (3)	−0.005 (3)
C4	0.020 (4)	0.014 (4)	0.023 (4)	−0.005 (3)	0.009 (3)	−0.001 (3)
C6	0.028 (4)	0.029 (4)	0.038 (5)	0.009 (4)	0.022 (4)	0.015 (4)
C7	0.017 (4)	0.018 (4)	0.020 (4)	−0.002 (3)	0.013 (3)	−0.003 (3)
C8	0.025 (4)	0.021 (4)	0.016 (4)	−0.006 (3)	0.013 (3)	−0.003 (3)
C9	0.021 (4)	0.018 (4)	0.030 (4)	−0.008 (3)	0.015 (3)	−0.014 (3)
C10	0.020 (4)	0.006 (3)	0.032 (4)	−0.002 (3)	0.013 (3)	−0.005 (3)
C11	0.012 (3)	0.004 (3)	0.021 (4)	−0.002 (3)	0.011 (3)	−0.002 (3)

Zn1—S1	2.2954 (18)	C4—H4A	0.9900
Zn1—S1i	2.2954 (18)	C4—H4B	0.9900
Zn1—N1i	2.083 (5)	C6—H6A	0.9800
Zn1—N1	2.083 (5)	C6—H6B	0.9800
S1—C1	1.727 (7)	C6—H6C	0.9800
S2—C1	1.652 (7)	C7—H7	0.9500
O2—C1	1.346 (8)	C7—C8	1.382 (10)
O2—C3	1.453 (8)	C8—H8	0.9500
O5—C4	1.426 (9)	C8—C9	1.377 (11)
O5—C6	1.418 (8)	C9—H9	0.9500
N1—C7	1.342 (9)	C9—C10	1.390 (11)
N1—C11	1.347 (8)	C10—H10	0.9500
C3—H3A	0.9900	C10—C11	1.371 (9)
C3—H3B	0.9900	C11—C11i	1.497 (13)
C3—C4	1.506 (10)
S1i—Zn1—S1	126.64 (10)	C3—C4—H4A	110.0
N1i—Zn1—S1	120.78 (15)	C3—C4—H4B	110.0
N1—Zn1—S1i	120.78 (15)	H4A—C4—H4B	108.4
N1—Zn1—S1	100.54 (15)	O5—C6—H6A	109.5
N1i—Zn1—S1i	100.54 (15)	O5—C6—H6B	109.5
N1—Zn1—N1i	78.7 (3)	O5—C6—H6C	109.5
C1—S1—Zn1	102.2 (2)	H6A—C6—H6B	109.5
C1—O2—C3	119.3 (5)	H6A—C6—H6C	109.5
C6—O5—C4	111.4 (6)	H6B—C6—H6C	109.5
C7—N1—Zn1	125.7 (5)	N1—C7—H7	118.7
C7—N1—C11	118.5 (6)	N1—C7—C8	122.7 (7)
C11—N1—Zn1	115.4 (4)	C8—C7—H7	118.7
S2—C1—S1	126.8 (4)	C7—C8—H8	120.8
O2—C1—S1	109.1 (5)	C9—C8—C7	118.4 (7)
O2—C1—S2	124.0 (5)	C9—C8—H8	120.8
O2—C3—H3A	110.5	C8—C9—H9	120.4
O2—C3—H3B	110.5	C8—C9—C10	119.2 (7)
O2—C3—C4	105.9 (6)	C10—C9—H9	120.4
H3A—C3—H3B	108.7	C9—C10—H10	120.4
C4—C3—H3A	110.5	C11—C10—C9	119.2 (7)
C4—C3—H3B	110.5	C11—C10—H10	120.4
O5—C4—C3	108.3 (6)	N1—C11—C10	121.9 (6)
O5—C4—H4A	110.0	N1—C11—C11i	115.0 (4)
O5—C4—H4B	110.0	C10—C11—C11i	123.1 (4)
Zn1—S1—C1—S2	4.2 (5)	C3—O2—C1—S2	−1.8 (9)
Zn1—S1—C1—O2	−175.3 (4)	C6—O5—C4—C3	−179.0 (6)
Zn1—N1—C7—C8	−172.1 (5)	C7—N1—C11—C10	−0.5 (9)
Zn1—N1—C11—C10	173.2 (5)	C7—N1—C11—C11i	179.9 (6)
Zn1—N1—C11—C11i	−6.4 (9)	C7—C8—C9—C10	0.7 (10)
O2—C3—C4—O5	73.0 (7)	C8—C9—C10—C11	−0.3 (10)
N1—C7—C8—C9	−0.9 (10)	C9—C10—C11—N1	0.2 (10)
C1—O2—C3—C4	−173.4 (6)	C9—C10—C11—C11i	179.8 (7)
C3—O2—C1—S1	177.8 (5)	C11—N1—C7—C8	0.8 (10)

D—H···A	D—H	H···A	D···A	D—H···A
C8—H8···O5ii	0.95	2.51	3.246 (9)	134
C7—H7···S2i	0.95	2.90	3.552 (7)	127