Supra­molecular inter­action patterns in the zinc(II) dichloride and tin(IV) tetra­chloride complexes with dipyrido[f,h]quinoxaline-6,7-dicarbonitrile

This study characterizes the supra­molecular synthons that dominate the inter­molecular organization of the title compounds, namely dichloridobis(dipyrido[f,h]quinoxaline-6,7-dicarbonitrile)zinc(II), [ZnCl₂(C₁₆H₆N₆)₂], (I), and tetrachlorido(dipyrido[f,h]quinoxaline-6,7-dicarbonitrile)tin(IV), [SnCl₄(C₁₆H₆N₆)], (II), in their respective crystal structures. Mol­ecules of (I) are located on 2^b axes of rotational symmetry. Their crystal packing is stabilized mostly by π–π stacking and dipole–dipole attractions between the organic ligand fragments of inversion-related neighbouring species, as well as by weak inter­molecular C—H...N hydrogen bonds. On the other hand, Cl...π and N...π inter­actions seem to direct the crystal packing in (II), which is unusual in the sense that its aromatic fragments are not involved in π–π stacking. Mol­ecules of (II) are located on m^b planes of mirror symmetry. This study confirms the diverse structural chemistry of this organic ligand, which can be involved in a wide range of supra­molecular inter­actions. These include effective coordination to various metal ions via the phenathroline N-atom sites, π–π stacking and π...halogen contacts through its extended π-system, and hydrogen bonding and N...π inter­actions through its nitrile groups. The competing natures of the latter make it difficult to predict a priori the preferred supra­molecular motif that may form in a given structure.

S1. Comment

The phenathroline-based 6,7-dicyanodipyridoquinoxaline (DICNQ) ligand has an extended π electron system and multiple N-sites, which make it an attractive reagent in diverse applications. It has been widely used as a multidentate coordination ligand in the synthesis of various transition metal complexes (Liu et al., 2001; Xu et al., 2002; Stephenson & Hardie, 2006). It has also been employed as an efficient antenna chromophore in the design of photonic and biochemical sensors (van der Tol et al., 1998; Arounaguiri & Maiya, 1999; Ambroize & Maiya, 2000). The redox chemistry of Ru^I complexes of DICNQ has been investigated too (Kulkarni et al., 2004). We were also interested in exploring the supramolecular reactivity of DICNQ, by evaluating the preferred modes of its intermolecular organization as a free ligand or in the form of its various complexes with metal ions. To this end, we synthesized DICNQ by a literature procedure (van der Tol et al., 1998; Arounaguiri & Maiya, 1999), determined its crystal structure, and characterized its remarkable π–π stacking as a dominant intermolecular interaction in the solid phase (Kozlov et al., 2008). Here, we report the crystal structures of the 2:1 complex of DICNQ with zinc(II) dichloride, (I), and the 1:1 complex of DICNQ with tin(IV) tetrachloride, (II), with an emphasis on their supramolecular self-organization and descriptions of the interaction synthons that operate therein.

Representations of (I) and (II) are shown in Fig. 1. In (I), molecules of the complex are located on axes of twofold rotation and the two DICNQ ligands bound to the Zn^II ion are symmetry equivalent. In (II), the complex resides on a mirror plane, which is perpendicular to the plane of the ligand. The DICNQ framework is aromatic, and it is quite planar in the two structures. For the 18-membered delocalized system (excluding the two –CN substituents), the deviations of the individual atoms from their mean plane does not exceed ±0.06 Å (r.m.s. 0.03 Å) in (I) and 0.05 Å (r.m.s. 0.03 Å) in (II). In both structures, the cyano groups deviate to a minor extent from the mean plane of the corresponding aromatic fragment.

The overall topology of complex (I) is dictated by the preferred tetrahedral coordination environment of the Zn^II ion with respect to the four ligating species, with the Cl^- anions occupying two vertices of the tetrahedron. Along the other two directions, the Zn^II is coordinated in a chelating manner by the phenanthroline side of two rotation-related DICNQ ligands. If the N sites of the coordinated phenanthroline moieties are counted as separate ligands, the coordination environment around the Zn^II ion can be described alternatively as a distorted octahedron. No metal coordination by the cyano sites is observed.

It appears that the intermolecular organization in the condensed solid phase of the species thus formed cannot be optimized solely by π–π stacking as in the crystal structure of the free flat DICNQ ligand (Kozlov et al., 2008). Instead, in (I), three different types of specific interactions (in addition to common dispersion) operate in concert. Fig. 2(a) illustrates the π–π stacking and dipole–dipole interactions beween DICNQ fragments related to one another by centres of inversion. Thus, significant overlap occurs between the quinoxaline moieties related by the symmetry operator (3/4 - x, 1/2 - y, 1 - z) (in the centre of Fig. 2a). The relatively short interplanar distance between the corresponding fragments (C8/C9/N17/C19–C22) is 3.29 (1) Å, which is indicative of a strong π–π interaction. In addition, dipolar attractions operate between the cyano groups of DICNQ residues inter-related by inversion at (1/2 - x, -y, 1/2 - z). The distance between the antiparallel pairs of CN dipoles of the two molecules is 3.123 (4) Å, which reflects a rather strong interaction. Preliminary density functional theory calculations (Software and reference?) confirm the attractive nature of the π–π and dipole–dipole interactions. The third component of the supramolecular interaction in this structure is shown in Fig. 2(b). It involves weak C—H···N(cyano) hydrogen bonds (Table 1). Every molecule of complex (I) associates via eight such hydrogen bonds to four neighbouring species, yielding an extended supramolecular network that propagates through the crystal structure. The unit cell shown in Fig. 3 partly illustrates the combination of the above-described interaction synthons in the crystal structure of (I). It also shows that the Cl^- ligands of one complex are oriented perpendicular to the π system of adjacent moieties, suggesting the presence of Cl···π interactions as well. The observed distance of the Cl^- anions from the plane of the corresponding DICNQ ring is 3.640 (5) Å, which is, however, considerably longer than expected for a Cl^-···π interaction [Rosokha et al., 2004; see also structure (II) below]. As the π–π stacking and dipole–dipole interactions operate in directions perpendicular to the two DICNQ rings, while the hydrogen bonds operate in different directions parallel to these rings, the entire supramolecular assembly exhibits a three-dimensional connectivity scheme. Structure (I) is nearly isomorphous with the structure of the cobalt dibromide analogue (Stephenson & Hardie, 2006).

The tin tetracholoride complex, (II), is characterized by a distorted octahedral geometry, with the two N atoms of the phenanthroline fragment occupying two adjacent coordination sites of the metal ion (Fig. 1b). Somewhat surprisingly, the supramolecular organization of (II) lacks the π–π stacking interactions between aromatic ligands which are often observed in the crystal structures of various metal ions with phenanthroline-type ligands (e.g. Bergman et al., 2002; Gut et al., 2002; Gupta et al., 2004; Rubin-Preminger et al., 2008). This may be mainly due to strong attractions between the electron-rich Cl^- ligand and the electron-deficient areas of the π electron system in DICNQ. These interactions are illustrated in Fig. 4. They are reflected well in the rather short contact distances, Cl4···C13(1/2 + x, y, -1/2 - z) = 3.254 (3) Å and Cl2···C14(1/2 - x, 1/2 + y, 1/2 + z) = 3.346 (4) Å, indicative of arrays of significant Cl···π interactions that extend in two dimensions, which is consistent with earlier reports (Rosokha et al., 2004). Furthermore, atom Cl4 is located 3.147 (10) Å above the plane of the proxime quinoxaline ring [atoms C10/N12/C13 at (1/2 + x, y, -1/2 - z) and at (1/2 + x, 1/2 - y, -1/2 - z)]. Thus, every molecule of the complex is involved in eight such Cl···π contacts through its Cl sites (`donating' electrons) and its π system (`accepting' electrons). Fig. 4 also shows that N···π interactions provide additional enthalpic stabilization to the observed structure along one direction of the two-dimensional supramolecular array. They involve the C—N groups of one species that interact with the π system of the two pyrido rings of adjacent species. Thus, the observed C9···N15(1/2 + x, y, -1/2 - z) distance is 3.163 (4) Å, and this N atom is located 3.010 (8) Å above the plane of the corresponding aromatic ring (N5/C6–C9/C11). Each molecule of the complex associates in four such interactions through its pair of cyano groups and the two pyrido rings. The CN bond is not perpendicular to the aromatic ring it overlaps, the approach angle being 46.20 (7) instead of 90°. Similar CN···π interactions were observed earlier in the structure of the octahedral [Ni(DICNQ)₃]Br₂ complex (Stephenson & Hardie, 2006). The above-described array of intermolecular interactions gives rise to two-dimensional supramolecular motifs. Another observation related to the presence of the N···π interactions is the slight inward bending of the cyano groups in (II) compared with the structure of the free DICNQ ligand (Kozlov et al., 2008). The intramolecular N15···N15(x, 1/2 - y, z) distance is 3.615 (5) Å in (II) compared with 3.999 (6) Å in the structure of the free ligand.

In summary, the supramolecular organization in (II) is stabilized mainly by the somewhat less common Cl···π and N···π interactions in two dimensions, but not by π–π stacking forces like those observed in the structure of DICNQ (Kozlov et al., 2008) and many other complexes of phenanthroline-type ligands (Bergman et al., 2002; Gut et al., 2002; Gupta et al., 2004; Rubin-Preminger et al., 2008).

This study demonstrates the diverse supramolecular reactivity of the DICNQ ligand. The competing natures of the secondary interactions, which involve the extended π system and the nitrile groups, make it difficult to predict a priori the preferred supramolecular organization in a given structure.

Related literature

For related literature, see: Ambroise & Maiya (2000); Arounaguiri & Maiya (1999); Bergman et al. (2002); Gupta et al. (2004); Gut et al. (2002); Kozlov et al. (2008); Kulkarni et al. (2004); Liu et al. (2001); Rosokha et al. (2004); Rubin-Preminger, Kozlov & Goldberg (2008); Stephenson & Hardie (2006); Tol et al. (1998); Xu et al. (2002).

S2. Experimental

DICNQ was synthesized by previously reported procedures (Arounaguiri & Maiya, 1999; van der Tol et al., 1998) and crystallized from ethanol by slow evaporation. For the synthesis of the zinc complex, (I), DICNQ (17.2 mg, 0.06 mmol) was dissolved in hot acetonitrile (15 ml). This solution was then mixed with a solution of zinc dichloride (2.9 mg, 0.02 mmol) in boiling acetonitrile (2.5 ml). Slow evaporation of the resulting mixture yielded plate–needle-shaped yellow crystals of (I) after three weeks. For the synthesis of the tin complex, (II), DICNQ (22.8 mg, 0.08 mmol) was dissolved in a hot methanol–ethyl acetate mixture (10 ml, 1:3 v/v). This solution was then mixed with a solution of tin dichloride dihydrate (12.8 mg, 0.06 mmol) in methanol (2.5 ml) under boiling/reflux conditions. Brown needle-shaped crystals of (I) appeared after one month of slow evaporation of the solvent under ambient conditions. It appears that during the preparative process of (II), the Sn^II species was oxidized to an Sn^IV moiety, leading to the SnCl₄–DICNQ product.

S3. Refinement

H atoms bound to C atoms were located in calculated positions and constrained to ride on their parent atoms, with C—H = 0.95 Å and with U_iso(H) = 1.2U_eq(C). The residual electron-density map of (I) contains a single peak of 1.82 e Å^-3, about 2.2 Å from N24, which could not be accounted for. It may be due to a systematic error in the intensity data set (e.g. an unnoticed diffraction from ice in the low-temperature experiment).

Computing details

For both compounds, data collection: COLLECT (Nonius, 1999); cell refinement: DENZO (Otwinowski & Minor, 1997); data reduction: DENZO (Otwinowski & Minor, 1997); program(s) used to solve structure: SIR97 (Altomare et al., 1994); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEPIII (Burnett & Johnson, 1996) and Mercury (Macrae et al., 2006); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures

	Fig. 1. The molecular structures of the title compounds, showing the atom-labelling schemes. Displacement ellipsoids are drawn at the 50% probability level at ca 110 K, and H atoms are shown as small spheres of arbitrary radii. (a) Compound (I), which is located on the twofold rotation axis at (1, y, 3/4) passing through the Zn^II ion; only atoms of the asymmetric unit are labelled. (b) Compound (II). Atoms of the asymmetric unit are labelled. The entire molecule of the complex is located on a plane of mirror symmetry (x, 1/4, z), which passes through the Sn^IV ion and perpendicular to the plane of the DICNQ ligand.
	Fig. 2. (a) The π–π stacking and dipole–dipole interaction modes in (I). The DICNQ fragment labelled (1) is at the symmetry position (x, y, z), that labelled (2) is at (1 - x, -y, 1 - z) and that labelled (3) is at (3/2 - x, 1/2 - y, 1 - z). The predominantly dipole–dipole interactions are indicated by dotted lines, while the π–π stacking is indicated by the double arrow. (b) The intermolecular hydrogen-bonding scheme (dotted lines) in (I). The DICNQ fragment labelled (1) is at the symmetry position (x, y, z), that labelled (2) is at (2 - x, -y, 1 - z) and that labelled (3) is at (1/2 - x, 1/2 - y, 1 - z). Zn and Cl atoms are denoted by small spheres. H atoms have been omitted for clarity. Primed atom N23' is at symmetry position (2) and doubly primed atom N24'' is at symmetry position (3).
	Fig. 3. The unit-cell contents in (I), showing some of the supramolecular interactions. The DICNQ fragment labelled (1) is at the symmetry position (x, y, z), that labelled (2) is at (1 - x, 1 - y, 1 - z), that labelled (3) is at (x - 1/2, y + 1/2, z) and that labelled (4) is at (3/2 - x, 1/2 - y, 1 - z). The weak hydrogen bond from primed atom C6' at (x - 1/2, y + 1/2, z) to doubly primed atom N23'' at (3/2 - x, 1/2 - y, 1 - z) and its inversion-related counterpart are marked by dotted lines. The π–π stacking interactions between overlapping DICNQ fragments are indicated by arrows. Zn and Cl atoms are denoted by small spheres. H atoms have been omitted for clarity.
	Fig. 4. The intermolecular interaction scheme in (II). The Cl···π interactions and interactions between neighbouring species are indicated by dotted lines. The N···π interactions are indicated by dashed arrows. Sn atoms are denoted by small spheres. H atoms have been omitted. Primed atoms are at the symmetry position (1/2 + x, y, -1/2 - z) and doubly primed atoms are the (1/2 - x, 1/2 + y, 1/2 - z).
	Fig. 5. The crystal packing of (II). The Cl···π and N···π interactions are indicated by dotted lines. Sn atoms are denoted by small spheres. H atoms have been omitted.

(I) dichloridobis(dipyrido[f,h]quinoxaline-6,7-dicarbonitrile)zinc(II)

Crystal data

[ZnCl2(C32H12N12)]	F(000) = 1408
Mr = 700.81	Dx = 1.597 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
a = 8.3051 (2) Å	Cell parameters from 2759 reflections
b = 12.6449 (3) Å	θ = 1.4–27.9°
c = 28.0176 (12) Å	µ = 1.07 mm^−1
β = 97.766 (2)°	T = 110 K
V = 2915.34 (16) Å^3	Plate, yellow
Z = 4	0.40 × 0.20 × 0.15 mm

Data collection

Nonius KappaCCD diffractometer	3433 independent reflections
Radiation source: fine-focus sealed tube	2501 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.035
Detector resolution: 12.8 pixels mm^-1	θmax = 27.8°, θmin = 3.0°
1 deg. ϕ and ω scans	h = −10→8
Absorption correction: multi-scan (Blessing, 1995)	k = −16→9
Tmin = 0.673, Tmax = 0.856	l = −36→36
9284 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)] = 0.062	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.173	H-atom parameters constrained
S = 1.07	w = 1/[σ^2(Fo^2) + (0.0799P)^2 + 10.2582P] where P = (Fo^2 + 2Fc^2)/3
3433 reflections	(Δ/σ)max < 0.001
213 parameters	Δρmax = 1.82 e Å^−3
0 restraints	Δρmin = −0.52 e Å^−3

Special details

Experimental. One hemisphere of data was collected

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.

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

	x	y	z	Uiso*/Ueq
Zn1	1.0000	0.46608 (5)	0.7500	0.0273 (2)
Cl2	0.87310 (11)	0.59024 (9)	0.79770 (4)	0.0360 (3)
N3	1.0649 (4)	0.3338 (3)	0.70149 (12)	0.0268 (7)
C4	1.2074 (4)	0.2864 (3)	0.70188 (14)	0.0300 (9)
H4	1.2920	0.3027	0.7271	0.036*
C5	1.2389 (5)	0.2136 (3)	0.66688 (15)	0.0317 (9)
H5	1.3432	0.1819	0.6684	0.038*
C6	1.1187 (5)	0.1880 (3)	0.63033 (16)	0.0335 (9)
H6	1.1383	0.1396	0.6058	0.040*
C7	0.9653 (5)	0.2354 (3)	0.63000 (14)	0.0299 (9)
C8	0.8298 (5)	0.2111 (3)	0.59291 (15)	0.0339 (9)
C9	0.6769 (5)	0.2603 (3)	0.59410 (15)	0.0340 (9)
C10	0.6554 (4)	0.3359 (3)	0.63142 (15)	0.0300 (9)
C11	0.5073 (4)	0.3884 (4)	0.63364 (15)	0.0338 (10)
H11	0.4156	0.3745	0.6104	0.041*
C12	0.4975 (4)	0.4596 (3)	0.66968 (15)	0.0327 (9)
H12	0.3978	0.4946	0.6722	0.039*
C13	0.6349 (4)	0.4807 (3)	0.70287 (15)	0.0294 (9)
H13	0.6263	0.5308	0.7276	0.035*
N14	0.7781 (3)	0.4333 (3)	0.70127 (12)	0.0269 (7)
C15	0.9437 (4)	0.3079 (3)	0.66576 (13)	0.0251 (8)
C16	0.7877 (4)	0.3607 (3)	0.66633 (14)	0.0260 (8)
N17	0.8560 (5)	0.1431 (3)	0.55784 (13)	0.0388 (9)
N18	0.5518 (4)	0.2406 (3)	0.55932 (13)	0.0389 (9)
C19	0.7290 (6)	0.1242 (4)	0.52388 (17)	0.0459 (12)
C20	0.5779 (6)	0.1740 (4)	0.52503 (16)	0.0445 (12)
C21	0.7511 (7)	0.0558 (4)	0.48534 (17)	0.0515 (14)
C22	0.4514 (7)	0.1522 (5)	0.48621 (17)	0.0523 (14)
N23	0.7675 (8)	−0.0001 (5)	0.4531 (2)	0.0831 (18)
N24	0.3496 (7)	0.1364 (5)	0.4546 (2)	0.0856 (19)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Zn1	0.0162 (3)	0.0314 (4)	0.0328 (4)	0.000	−0.0029 (2)	0.000
Cl2	0.0223 (5)	0.0362 (6)	0.0489 (7)	−0.0017 (4)	0.0020 (4)	−0.0110 (5)
N3	0.0225 (15)	0.0271 (17)	0.0288 (17)	−0.0007 (13)	−0.0030 (12)	0.0029 (14)
C4	0.0211 (18)	0.035 (2)	0.032 (2)	0.0011 (15)	−0.0029 (15)	0.0040 (18)
C5	0.028 (2)	0.029 (2)	0.038 (2)	0.0034 (16)	0.0024 (16)	0.0018 (18)
C6	0.040 (2)	0.026 (2)	0.035 (2)	0.0009 (17)	0.0040 (17)	0.0005 (18)
C7	0.031 (2)	0.029 (2)	0.028 (2)	−0.0022 (16)	−0.0002 (16)	0.0046 (17)
C8	0.039 (2)	0.032 (2)	0.030 (2)	−0.0062 (18)	0.0009 (17)	0.0000 (18)
C9	0.034 (2)	0.034 (2)	0.031 (2)	−0.0109 (18)	−0.0047 (16)	0.0066 (18)
C10	0.0240 (18)	0.032 (2)	0.032 (2)	−0.0083 (16)	−0.0032 (15)	0.0028 (17)
C11	0.0202 (18)	0.043 (3)	0.035 (2)	−0.0073 (17)	−0.0071 (15)	0.007 (2)
C12	0.0171 (17)	0.040 (2)	0.041 (2)	0.0007 (16)	0.0008 (15)	0.011 (2)
C13	0.0222 (18)	0.033 (2)	0.033 (2)	−0.0003 (15)	0.0014 (15)	0.0072 (17)
N14	0.0169 (14)	0.0322 (18)	0.0306 (18)	−0.0001 (13)	−0.0007 (12)	0.0042 (15)
C15	0.0251 (18)	0.0235 (19)	0.026 (2)	−0.0025 (15)	0.0010 (14)	0.0041 (16)
C16	0.0228 (17)	0.027 (2)	0.0267 (19)	−0.0043 (15)	−0.0016 (14)	0.0073 (17)
N17	0.047 (2)	0.035 (2)	0.033 (2)	−0.0100 (17)	0.0010 (16)	−0.0016 (17)
N18	0.0366 (19)	0.045 (2)	0.031 (2)	−0.0127 (17)	−0.0074 (15)	0.0033 (17)
C19	0.059 (3)	0.040 (3)	0.036 (3)	−0.014 (2)	−0.002 (2)	0.006 (2)
C20	0.049 (3)	0.049 (3)	0.031 (2)	−0.020 (2)	−0.0092 (19)	0.002 (2)
C21	0.081 (4)	0.046 (3)	0.025 (2)	−0.026 (3)	0.000 (2)	−0.010 (2)
C22	0.063 (3)	0.059 (3)	0.031 (2)	−0.030 (3)	−0.010 (2)	−0.002 (2)
N23	0.117 (5)	0.075 (4)	0.058 (3)	−0.027 (4)	0.014 (3)	−0.006 (3)
N24	0.081 (4)	0.109 (5)	0.062 (3)	−0.036 (4)	−0.011 (3)	0.013 (3)

Geometric parameters (Å, º)

Zn1—N14	2.180 (3)	C10—C16	1.405 (5)
Zn1—N3	2.265 (3)	C10—C11	1.406 (6)
Zn1—Cl2	2.3962 (11)	C11—C12	1.363 (6)
N3—C4	1.326 (5)	C11—H11	0.9500
N3—C15	1.361 (5)	C12—C13	1.397 (5)
C4—C5	1.395 (6)	C12—H12	0.9500
C4—H4	0.9500	C13—N14	1.337 (5)
C5—C6	1.369 (6)	C13—H13	0.9500
C5—H5	0.9500	N14—C16	1.353 (5)
C6—C7	1.406 (6)	C15—C16	1.459 (5)
C6—H6	0.9500	N17—C19	1.343 (6)
C7—C15	1.388 (6)	N18—C20	1.318 (6)
C7—C8	1.458 (6)	C19—C20	1.408 (8)
C8—N17	1.346 (6)	C19—C21	1.414 (7)
C8—C9	1.418 (6)	C20—C22	1.434 (6)
C9—N18	1.349 (5)	C21—N23	1.171 (8)
C9—C10	1.445 (6)	C22—N24	1.156 (7)
N14^i—Zn1—N14	158.10 (18)	C16—C10—C9	119.3 (4)
N14—Zn1—N3	74.56 (12)	C11—C10—C9	122.6 (4)
N14—Zn1—N3^i	89.19 (12)	C12—C11—C10	119.0 (3)
N3—Zn1—N3^i	84.85 (17)	C12—C11—H11	120.5
N14—Zn1—Cl2	94.32 (9)	C10—C11—H11	120.5
N3—Zn1—Cl2	167.54 (8)	C11—C12—C13	119.6 (4)
N14—Zn1—Cl2^i	99.99 (9)	C11—C12—H12	120.2
N3—Zn1—Cl2^i	89.47 (9)	C13—C12—H12	120.2
Cl2—Zn1—Cl2^i	98.14 (6)	N14—C13—C12	122.9 (4)
C4—N3—C15	117.9 (3)	N14—C13—H13	118.6
C4—N3—Zn1	127.9 (3)	C12—C13—H13	118.6
C15—N3—Zn1	114.0 (2)	C13—N14—C16	117.9 (3)
N3—C4—C5	123.0 (4)	C13—N14—Zn1	125.1 (3)
N3—C4—H4	118.5	C16—N14—Zn1	117.0 (2)
C5—C4—H4	118.5	N3—C15—C7	122.4 (3)
C6—C5—C4	119.7 (4)	N3—C15—C16	116.9 (3)
C6—C5—H5	120.2	C7—C15—C16	120.8 (3)
C4—C5—H5	120.2	N14—C16—C10	122.6 (3)
C5—C6—C7	118.2 (4)	N14—C16—C15	117.2 (3)
C5—C6—H6	120.9	C10—C16—C15	120.2 (4)
C7—C6—H6	120.9	C19—N17—C8	116.2 (4)
C15—C7—C6	118.8 (4)	C20—N18—C9	117.3 (4)
C15—C7—C8	119.4 (4)	N17—C19—C20	121.4 (5)
C6—C7—C8	121.8 (4)	N17—C19—C21	118.6 (5)
N17—C8—C9	122.1 (4)	C20—C19—C21	119.9 (4)
N17—C8—C7	118.0 (4)	N18—C20—C19	122.5 (4)
C9—C8—C7	119.9 (4)	N18—C20—C22	120.0 (5)
N18—C9—C8	120.5 (4)	C19—C20—C22	117.4 (5)
N18—C9—C10	119.1 (4)	N23—C21—C19	179.1 (7)
C8—C9—C10	120.4 (4)	N24—C22—C20	178.8 (6)
C16—C10—C11	118.1 (4)
N14^i—Zn1—N3—C4	−15.5 (3)	N18—C9—C10—C16	−176.8 (4)
N14—Zn1—N3—C4	179.4 (4)	C8—C9—C10—C16	0.5 (6)
N3^i—Zn1—N3—C4	−90.1 (3)	N18—C9—C10—C11	1.4 (6)
Cl2—Zn1—N3—C4	−153.3 (3)	C8—C9—C10—C11	178.7 (4)
Cl2^i—Zn1—N3—C4	78.8 (3)	C16—C10—C11—C12	−1.0 (6)
N14^i—Zn1—N3—C15	170.1 (3)	C9—C10—C11—C12	−179.2 (4)
N14—Zn1—N3—C15	5.0 (3)	C10—C11—C12—C13	1.5 (6)
N3^i—Zn1—N3—C15	95.5 (3)	C16—N14—C13—C12	−1.2 (6)
Cl2—Zn1—N3—C15	32.3 (6)	Zn1—N14—C13—C12	177.6 (3)
Cl2^i—Zn1—N3—C15	−95.6 (3)	C11—C12—C13—N14	−0.4 (6)
N14^i—Zn1—N14—C13	133.8 (3)	C4—N3—C15—C7	−0.8 (6)
N3^i—Zn1—N14—C13	92.4 (3)	Zn1—N3—C15—C7	174.2 (3)
N3—Zn1—N14—C13	177.2 (3)	C4—N3—C15—C16	179.6 (3)
Cl2—Zn1—N14—C13	2.9 (3)	Zn1—N3—C15—C16	−5.4 (4)
Cl2^i—Zn1—N14—C13	−96.1 (3)	C6—C7—C15—N3	−0.9 (6)
N14^i—Zn1—N14—C16	−47.3 (3)	C8—C7—C15—N3	179.8 (4)
N3^i—Zn1—N14—C16	−88.8 (3)	C6—C7—C15—C16	178.8 (4)
N3—Zn1—N14—C16	−3.9 (3)	C8—C7—C15—C16	−0.6 (6)
Cl2—Zn1—N14—C16	−178.2 (3)	C13—N14—C16—C10	1.8 (6)
Cl2^i—Zn1—N14—C16	82.7 (3)	Zn1—N14—C16—C10	−177.2 (3)
C15—N3—C4—C5	1.5 (6)	C13—N14—C16—C15	−178.6 (3)
Zn1—N3—C4—C5	−172.7 (3)	Zn1—N14—C16—C15	2.5 (4)
N3—C4—C5—C6	−0.5 (6)	C11—C10—C16—N14	−0.7 (6)
C4—C5—C6—C7	−1.1 (6)	C9—C10—C16—N14	177.6 (4)
C5—C6—C7—C15	1.8 (6)	C11—C10—C16—C15	179.6 (4)
C5—C6—C7—C8	−178.8 (4)	C9—C10—C16—C15	−2.1 (6)
C19—N17—C8—C9	0.0 (6)	N3—C15—C16—N14	2.1 (5)
C19—N17—C8—C7	−178.9 (4)	C7—C15—C16—N14	−177.5 (3)
C15—C7—C8—N17	177.9 (4)	N3—C15—C16—C10	−178.2 (3)
C6—C7—C8—N17	−1.5 (6)	C7—C15—C16—C10	2.2 (6)
C15—C7—C8—C9	−1.0 (6)	C8—N17—C19—C20	0.6 (7)
C6—C7—C8—C9	179.7 (4)	C8—N17—C19—C21	178.1 (4)
C20—N18—C9—C8	0.5 (6)	C9—N18—C20—C19	0.1 (7)
C20—N18—C9—C10	177.7 (4)	C9—N18—C20—C22	−178.1 (4)
N17—C8—C9—N18	−0.5 (6)	N17—C19—C20—N18	−0.7 (7)
C7—C8—C9—N18	178.3 (4)	C21—C19—C20—N18	−178.1 (4)
N17—C8—C9—C10	−177.7 (4)	N17—C19—C20—C22	177.5 (4)
C7—C8—C9—C10	1.1 (6)	C21—C19—C20—C22	0.1 (7)

Symmetry code: (i) −x+2, y, −z+3/2.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C6—H6···N23^ii	0.95	2.61	3.549 (8)	171
C11—H11···N24^iii	0.95	2.66	3.608 (6)	172

Symmetry codes: (ii) −x+2, −y, −z+1; (iii) −x+1/2, −y+1/2, −z+1.

(II) tetrachlorido(dipyrido[f,h]quinoxaline-6,7-dicarbonitrile)tin(IV)

Crystal data

[SnCl4(C16H6N6)]	Dx = 1.910 Mg m^−3
Mr = 542.77	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Pnma	Cell parameters from 2487 reflections
a = 14.8630 (4) Å	θ = 2.5–27.9°
b = 12.8457 (3) Å	µ = 1.93 mm^−1
c = 9.8852 (2) Å	T = 110 K
V = 1887.34 (8) Å^3	Needle, brown
Z = 4	0.55 × 0.15 × 0.06 mm
F(000) = 1048

Data collection

Nonius KappaCCD diffractometer	2292 independent reflections
Radiation source: fine-focus sealed tube	1822 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.055
Detector resolution: 12.8 pixels mm^-1	θmax = 27.9°, θmin = 2.5°
1 deg. ϕ scans	h = −19→0
Absorption correction: multi-scan (Blessing, 1995)	k = 0→15
Tmin = 0.492, Tmax = 0.915	l = 0→12
14219 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)] = 0.038	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.089	H-atom parameters constrained
S = 1.04	w = 1/[σ^2(Fo^2) + (0.0419P)^2 + 1.6487P] where P = (Fo^2 + 2Fc^2)/3
2292 reflections	(Δ/σ)max = 0.001
127 parameters	Δρmax = 0.53 e Å^−3
0 restraints	Δρmin = −0.78 e Å^−3

Special details

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.

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

	x	y	z	Uiso*/Ueq
Sn1	0.45953 (2)	0.2500	0.17411 (3)	0.03787 (13)
Cl2	0.54487 (7)	0.39021 (8)	0.25853 (10)	0.0538 (3)
Cl3	0.35726 (9)	0.2500	0.36490 (12)	0.0467 (3)
Cl4	0.53914 (8)	0.2500	−0.03944 (12)	0.0424 (3)
N5	0.35850 (18)	0.1448 (2)	0.0769 (3)	0.0351 (6)
C6	0.3634 (3)	0.0404 (3)	0.0708 (3)	0.0413 (8)
H6	0.4159	0.0065	0.1031	0.050*
C7	0.2938 (3)	−0.0191 (3)	0.0186 (4)	0.0444 (9)
H7	0.2993	−0.0927	0.0140	0.053*
C8	0.2174 (2)	0.0284 (3)	−0.0261 (3)	0.0399 (8)
H8	0.1687	−0.0120	−0.0596	0.048*
C9	0.2111 (2)	0.1379 (3)	−0.0224 (3)	0.0333 (7)
C10	0.1330 (2)	0.1950 (3)	−0.0685 (3)	0.0339 (7)
C11	0.2841 (2)	0.1933 (3)	0.0293 (3)	0.0342 (7)
N12	0.06107 (19)	0.1398 (2)	−0.1106 (3)	0.0387 (7)
C13	−0.0094 (2)	0.1958 (3)	−0.1474 (3)	0.0374 (7)
C14	−0.0903 (3)	0.1424 (3)	−0.1920 (3)	0.0429 (8)
N15	−0.1568 (2)	0.1093 (3)	−0.2295 (3)	0.0535 (9)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Sn1	0.0388 (2)	0.0459 (2)	0.02890 (18)	0.000	−0.00373 (14)	0.000
Cl2	0.0563 (6)	0.0621 (6)	0.0431 (5)	−0.0125 (5)	−0.0116 (4)	−0.0052 (4)
Cl3	0.0546 (8)	0.0520 (7)	0.0334 (6)	0.000	0.0042 (5)	0.000
Cl4	0.0369 (7)	0.0582 (8)	0.0320 (6)	0.000	−0.0009 (5)	0.000
N5	0.0349 (15)	0.0405 (16)	0.0299 (13)	0.0000 (12)	0.0005 (11)	0.0026 (12)
C6	0.045 (2)	0.0399 (19)	0.0394 (18)	0.0053 (15)	0.0009 (16)	0.0058 (15)
C7	0.051 (2)	0.0359 (18)	0.046 (2)	0.0009 (16)	0.0048 (18)	0.0037 (16)
C8	0.043 (2)	0.0391 (18)	0.0374 (18)	−0.0066 (15)	0.0041 (15)	0.0013 (15)
C9	0.0345 (18)	0.0387 (17)	0.0268 (15)	−0.0024 (14)	0.0046 (13)	0.0015 (13)
C10	0.0314 (17)	0.0448 (18)	0.0255 (15)	−0.0045 (14)	0.0038 (13)	−0.0026 (13)
C11	0.0377 (19)	0.0375 (18)	0.0275 (15)	0.0018 (14)	0.0045 (14)	0.0027 (13)
N12	0.0370 (16)	0.0471 (16)	0.0321 (14)	−0.0034 (13)	0.0017 (12)	0.0000 (13)
C13	0.0322 (17)	0.0498 (19)	0.0302 (16)	−0.0039 (15)	−0.0001 (14)	0.0007 (14)
C14	0.044 (2)	0.051 (2)	0.0338 (18)	−0.0040 (17)	−0.0017 (16)	0.0045 (16)
N15	0.048 (2)	0.067 (2)	0.0454 (18)	−0.0081 (17)	−0.0077 (16)	0.0058 (16)

Geometric parameters (Å, º)

Sn1—N5	2.237 (3)	C8—H8	0.9500
Sn1—Cl2	2.3556 (10)	C9—C11	1.395 (5)
Sn1—Cl4	2.4200 (12)	C9—C10	1.446 (5)
Sn1—Cl3	2.4223 (13)	C10—N12	1.349 (4)
N5—C6	1.344 (4)	C10—C10^i	1.414 (7)
N5—C11	1.353 (4)	C11—C11^i	1.457 (6)
C6—C7	1.386 (5)	N12—C13	1.322 (4)
C6—H6	0.9500	C13—C13^i	1.391 (7)
C7—C8	1.362 (5)	C13—C14	1.452 (5)
C7—H7	0.9500	C14—N15	1.138 (5)
C8—C9	1.410 (5)
N5—Sn1—N5^i	74.33 (14)	C7—C8—C9	119.6 (3)
N5—Sn1—Cl2^i	92.96 (8)	C7—C8—H8	120.2
N5—Sn1—Cl2	167.29 (8)	C9—C8—H8	120.2
Cl2^i—Sn1—Cl2	99.74 (5)	C11—C9—C8	117.8 (3)
N5—Sn1—Cl4	87.33 (7)	C11—C9—C10	118.8 (3)
Cl2—Sn1—Cl4	92.62 (3)	C8—C9—C10	123.4 (3)
N5—Sn1—Cl3	85.03 (7)	N12—C10—C10^i	121.69 (19)
Cl2—Sn1—Cl3	93.56 (3)	N12—C10—C9	117.9 (3)
Cl4—Sn1—Cl3	170.40 (4)	C10^i—C10—C9	120.46 (18)
C6—N5—C11	119.2 (3)	N5—C11—C9	121.9 (3)
C6—N5—Sn1	125.9 (2)	N5—C11—C11^i	117.43 (18)
C11—N5—Sn1	114.8 (2)	C9—C11—C11^i	120.66 (19)
N5—C6—C7	121.8 (3)	C13—N12—C10	115.3 (3)
N5—C6—H6	119.1	N12—C13—C13^i	123.0 (2)
C7—C6—H6	119.1	N12—C13—C14	118.8 (3)
C8—C7—C6	119.7 (4)	C13^i—C13—C14	118.2 (2)
C8—C7—H7	120.2	N15—C14—C13	173.8 (4)
C6—C7—H7	120.2
N5^i—Sn1—N5—C6	175.3 (2)	C13—N12—C10—C10^i	−2.0 (3)
Cl2^i—Sn1—N5—C6	−5.2 (3)	C13—N12—C10—C9	177.8 (3)
Cl2—Sn1—N5—C6	177.4 (2)	C11—C9—C10—N12	−176.1 (3)
Cl4—Sn1—N5—C6	87.3 (3)	C8—C9—C10—N12	3.5 (5)
Cl3—Sn1—N5—C6	−98.5 (3)	C11—C9—C10—C10^i	3.8 (3)
N5^i—Sn1—N5—C11	−9.4 (2)	C8—C9—C10—C10^i	−176.7 (2)
Cl2^i—Sn1—N5—C11	170.2 (2)	C6—N5—C11—C9	1.8 (4)
Cl2—Sn1—N5—C11	−7.3 (5)	Sn1—N5—C11—C9	−173.8 (2)
Cl4—Sn1—N5—C11	−97.4 (2)	C6—N5—C11—C11^i	−175.9 (2)
Cl3—Sn1—N5—C11	76.8 (2)	Sn1—N5—C11—C11^i	8.4 (2)
C11—N5—C6—C7	−0.8 (5)	C8—C9—C11—N5	−1.0 (4)
Sn1—N5—C6—C7	174.4 (2)	C10—C9—C11—N5	178.6 (3)
N5—C6—C7—C8	−1.1 (5)	C8—C9—C11—C11^i	176.6 (2)
C6—C7—C8—C9	1.8 (5)	C10—C9—C11—C11^i	−3.8 (3)
C7—C8—C9—C11	−0.8 (5)	C10—N12—C13—C13^i	2.0 (3)
C7—C8—C9—C10	179.6 (3)	C10—N12—C13—C14	−179.0 (3)

Symmetry code: (i) x, −y+1/2, z.