Halogen bonds on demand: I...S contacts in cocrystals of trans-bis­(thiocyanato-[kappa]N)tetra­kis­(4-vinyl­pyridine-[kappa]N)nickel(II) and 2,3,5,6-tetra­fluoro-1,4-di­iodo­benzene

Hydrogen bonds are considered a powerful organizing force in designing supra­molecular architectures because they are directional, selective and reversible at room temperature. trans-Di­thio­cyanato­tetra­kis­(4-vinyl­pyridine)­nickel(II) is a popular host for the inclusion of small mol­ecules and 2,3,5,6-tetra­fluoro-1,4-di­iodo­benzene (TFDIB) represents a strong halogen-bond donor. These constituents cocrystallize in a 1:1 stoichiometry, [Ni(NCS)₂(C₇H₇N)₄]·C₆F₄I₂, in the tetra­gonal space group I4₁/a. Both residues occupy special positions, i.e. the pseudo-octa­hedral Ni^II complex is located on a twofold axis and the TFDIB mol­ecule sits about a crystallographic centre of inversion. The components inter­act via a short S...I contact of 3.2891 (12) Å between the thio­cyanate S atom of the host and the iodine substituent at the perhalogenated aromatic ring of the smaller guest mol­ecule. This inter­action meets the commonly accepted criteria for a halogen bond. Such halogen bonds to sulfur are significantly less common than to smaller electronegative atoms.

S1. Introduction

Crystal engineering deals with competition, co-operation and balance between different inter­molecular forces in extended crystal structures (Aakeroy, 1997; Steiner, 2002; Desiraju, 2014; Deringer et al., 2014; Thakur et al., 2015).

Hydrogen bonds are considered a powerful organizing force in designing supra­molecular architectures because they are directional, selective and reversible at room temperature.

Halogen bonding implies a directional inter­action between an electron-density donor (a neutral or anionic Lewis base with an N, O, S, P or halogen functionality) and a (usually heavy) halogen atom as electrophile. Halogen bonds have been defined by Mate Erdélyi in his tutorial review (Erdélyi, 2012) as `the cement to assemble molecules into supra­molecular architectures' (Metrangolo & Resnati, 2001; Metrangolo et al., 2008; Wang et al., 2012, 2013; Erdélyi, 2012; Pan et al., 2015). Halogen bonds in which an S atom is the formal acceptor, i.e. it acts as a lone-pair donor towards the σ hole of a heavy halide, are quite rare. For S···I contacts, the Camdridge Structural Database (CSD, Version 5.36, including updates of November 2014, 717876 entries; Groom & Allen, 2014) lists only 17 occurrences for C—S···I—C with S···I < 3.4 Å. It goes without explicit literature citation that this infrequency is in marked contrast with the many examples of short N···X or O···X (X = Cl, Br or I) contacts.

We expected to design a representative for such a rare S···I halogen bond by combining two particularly suitable constituents in a cocrystal. For the sulfur halogen-bond acceptor group, we chose di­thio­cyanato­tetra­kis(4-vinyl­pyridine)­nickel(II). This Ni^II complex is suitable for cocrystal formation; according to Moore and co-workers, the reason is the remarkable rotational freedom of the pyridine rings about their Ni—N bonds, which allows the molecule to adjust its shape to accommodate various guest molecules of different shape, size and polarity. Moreover, the iso­thio­cyanate group allows a secondary inter­action between the S atom and the nonmetallic elements of the guest molecules (Moore et al., 1987; Nassimbeni et al., 1989).

This pseudo-o­cta­hedral complex was originally described by Lipkowski et al. (1984) and Nassimbeni & coworkers (Moore et al.,1986); the latter group used it as host to accomodate a variety of small guest molecules, such as: (i) p-xylene, m-xylene and o-xylene (Moore et al.,1986; CSD refcodes FINCOU, FINCUA and FINDAH, respectively) or chloro­form (Moore et al., 1987; refcode FOCDEG); (ii) cyclo­hexane and tetra­hydro­furan; 1,3-cyclo­hexadiene and tetra­hydro­furan; 1,4-cyclo­hexadiene and tetra­hydro­furan; benzene and tetra­hydro­furan, benzene or tetra­hydro­furan (Lavelle & Nassimbeni, 1993; CSD refcodes PIZLOZ, PIZMAM, PIZMIU, PIZMOA, PIZMUG and PIZNAN, respectively); (iii) tetra­chloro­methane or tri­iodo­methane (Nassimbeni et al., 1989; CSD refcodes VAXVAR, VAXVEV and VAXVIZ, respectively).

Tetra­fluoro­diiodo­benzene (TFDIB) meets the requirements for a good halogen-bond donor through its iodo substituents towards nucleophiles such as the S atom from the iso­thio­cyanate ligand. Our group has used TFDIB for the construction of cocrystals in which hydrogen and halogen bonds of different strengths co-exist with coordinative bonds (Merkens et al., 2013).

The present contribution deals with the successful cocrystallization of di­thio­cyanato­tetra­kis(4-vinyl­pyridine)­nickel(II), [Ni(NCS)₂(4ViPy)₄], and TFDIB. In the resulting adduct, (1) (see scheme), the iso­thio­cyanate S atom acts as electron-density donor or halogen-bond acceptor.

S2. Experimental

S2.1. Synthesis and crystallization

Chemicals were used as supplied without further purification. The powder X-ray diffraction (PXRD) pattern was recorded at the Institute of Inorganic Chemistry, RWTH Aachen University, using a Stoe IP-PSD imaging-plate detector. A flat sample was measured in transmission using Cu Kα₁ radiation at ambient temperature. Nickel(II) thio­cyanate was prepared according to the procedure described by Sarma & Poddar (1984). Di­thio­cyanato­tetra­kis(4-vinyl­pyridine)­nickel(II), [Ni(NCS)₂(4ViPy)₄], was prepared following the procedure of Moore et al. (1986).

For the preparation of (1), [Ni(NCS)₂(4ViPy)₄] (0.1 mmol, 59.5 mg) and 2,3,5,6-tetra­fluoro-1,4-di­iodo­benzene (0.1 mmol, 40.18 mg) were dissolved in ethanol (6 ml) at room temperature. Blue crystals of (1) were obtained from the resulting solution by partial evaporation at room temperature overnight. The phase purity of the product was confirmed by powder X-ray diffraction (see Fig. 1).

S2.2. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 1. Crystal data, data collection and structure refinement details are summarized in Table 1. H atoms attached to C atoms were calculated, introduced in their idealized positions and treated as riding, with C—H = 0.95 Å and U_iso(H) = 1.2U_eq(C).

S3. Results and discussion

The title compound, (1), crystallizes in the centrosymmetric tetra­gonal space group I4₁/a with half a molecule of di­thio­cyanato­tetra­kis(4-vinyl­pyridine)­nickel(II), [Ni(NCS)₂(4ViPy)₄], and half a molecule of 2,3,5,6-tetra­fluoro-1,4-di­iodo­benzene (TFDIB) in the asymmetric unit. The larger coordination compound can be perceived as host; it is situated on a twofold crystallographic axis, with the Ni atom on Wyckoff position 8e, whereas the centre of gravity of the perhalogenated guest coincides with a centre of inversion.

The Ni^II cation is coordinated by six N atoms, four from the 4-vinyl­pyridine (4ViPy) ligands in equatorial positions and two from the iso­thio­cyanate (NCS) ligands in axial positions (Fig. 2). The Ni—N distances range from 2.084 (3) to 2.118 (3) Å (Table 2). The Ni—N bonds to the iso­thio­cyanate ligands are shorter than those to the pyridine ligands, as reported previously for this type of compound (Roy et al., 2007; Lavelle & Nassimbeni, 1993; Moore et al., 1987; Miklovic et al., 2004).

The complex molecule adopts a four-blade propeller geometry. The four torsion angles of the 4-vinyl­pyridine ligands (N1—Ni1—Nx1—Cx2) differ only slightly from each other and adopt the following values: N1—Ni1—N2—C5 = -139.8 (3)°, N1—Ni1—N2ⁱ—C5ⁱ = 41.5 (3)°, N1—Ni1—N3—C8 = -134.1 (3)° and N1—Ni1—N3ⁱ—C8ⁱ = 44.7 (3)° [symmetry code: (i) -x, -y + 1/2, z].

The iso­thio­yanate ligand is significantly bent at the N-atom position, with an Ni—N—C angle of 157.1 (3)°. The two NCS ligands in a trans geometry are not coplanar but subtend a C—N···N—C angle of 9.9 (2)°.

The iodine substituents in the TFDIB residue are suitable halogen-bond donors towards nucleophiles such as the terminal S atom from the iso­thio­cyanate ligands. TFDIB has been used successfully as an electrophilic component in short halogen bonds with pyridine derivatives (Roper et al., 2010; Sgarbossa et al., 2012; Merkens et al., 2013).

According to Desiraju and co-workers (Thalladi et al., 1998; Thakur et al., 2015), in the absence of strong hydrogen bonds, weak inter­molecular inter­actions are very important for the overall crystal packing. This is true in the crystal structure of (1), which is stabilized through very short S···I halogen bonds of 3.2891 (12) Å, considerably shorter than the sum of the common van der Waals radii, i.e. I 1.98 Å and S 1.80 Å (Batsanov, 2001). Hirshfeld surfaces (Hirshfeld, 1977; Wolff et al., 2010) allow the visualization of the relevant inter­molecular contacts. They are presented in Figs. 3(a) and 3(b) for both residues of (1); the short S···I inter­action corresponds to the pronounced red spot on the surface.

A histogram of S···I contacts allows the classification of the halogen bond in (1) as unusually short. Fig. 4 shows that the vast majority of inter­molecular S···I contacts retrieved from the CSD are associated with distances longer than 3.4 Å.

Inter­atomic distances do not represent the only criteria for halogen bonds: Nassimbeni and co-workers (Nassimbeni et al., 1989; Lavelle & Nassimbeni, 1993) have already described two alternative geometries in which `secondary bonding' between an iso­thio­cyanate S atom and an I atom of the guest can occur. Either the (NiNC)—S···I or the S···I—C angle should be approximately linear. In the case of (1), the latter amounts to 164.20 (13)° and thus matches the expected geometry for a halogen bond, with the S atom approaching the σ hole at the I atom opposite the aryl C—I bond.

Space-filling in cocrystal (1) is efficient: its density of 1.758 Mg m^-3 is significantly higher than that for unsolvated α-[Ni(NCS)₂(4ViPy)₄] with a density of 1.3 Mg m^-3 (Lipkowski et al., 1984). The packing for (1) does not show any relevant voids: the cocrystal is associated with a packing index of 68.9%, whereas a hypothetical unsolvated guest structure (Fig. 5) would correspond to a much more close-packed solid with 53.1% space filling.

Alternatively, the packing density can be expressed as the ratio (volume of the unit cell):(number of non-H atoms in the unit cell). When such a comparison is made for (1) with clathrates reported by Moore et al. (1986) or Lavelle & Nassimbeni (1993), it confirms that our compound is more efficiently packed than the clathrates reported earlier [Is it worth giving the specific numbers here?].

S4. Conclusion

A coordination complex prone to encapsulating small guest molecules and tetra­fluoro­diiodo­benzene, a well-established halogen-bond donor, have been cocrystallized. These particularly well suited residues subtend an unusually short S···I contact. Future work will focus on aspects beyond molecular geometry. We will attempt to grow crystals suitable for high-resolution diffraction experiments, perform multipole refinements and analyze the resulting experimental electron density in terms of Bader's AIM (atoms in molecules) theory (Bader, 1990). Very short inter­molecular contacts can be associated with significant electron density in the bond critical point (Wang et al., 2013).

Computing details

Data collection: SMART (Bruker, 2001); cell refinement: SAINT-Plus (Bruker, 2009); data reduction: SAINT-Plus (Bruker, 2009); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: PLATON (Spek, 2009); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures

	Fig. 1. Experimental (blue) and simulated (red) X-ray powder diffractograms of (1).
	Fig. 2. PLATON (Spek, 2009) plot of the residues in (1), showing the atomic numbering scheme. [Displacement ellipsoids are drawn at the ??% probability level.] H atoms have been omitted for clarity. The residues are not shown in the same view direction to avoid overlap. [Symmetry codes: (i) -x, -y + 1/2, z; (ii) -x, -y, -z + 2.]
	Fig. 3. Hirshfeld surfaces (Wolff et al., 2010) for (a) the 2,3,5,6-tetrafluoro-1,4-diiodobenzene residue and (b) the [Ni(NCS)2(4ViPy)4] residue in (1).
	Fig. 4. Histogram of S···I contacts found in the CSD. The arrow indicates the S···I halogen bond distance in (1).
	Fig. 5. Hypothetical cavities in cocrystal (1) when only host molecules are taken into account and TFDIB guests have been omitted.

trans-Tetrakis(4-vinylpyridine-κN)bis(thiocyanato-κN)nickel(II)–2,3,5,6-tetrafluoro-1,4-diiodobenzene (1/1)

Crystal data

[Ni(NCS)2(C7H7N)4]·C6F4I2	Dx = 1.758 Mg m^−3
Mr = 997.27	Mo Kα radiation, λ = 0.71073 Å
Tetragonal, I41/a	θ = 2.5–20.0°
a = 16.2034 (14) Å	µ = 2.32 mm^−1
c = 28.698 (2) Å	T = 100 K
V = 7534.6 (14) Å^3	Block, blue
Z = 8	0.13 × 0.12 × 0.10 mm
F(000) = 3904

Data collection

Bruker SMART CCD area-detector diffractometer	2947 reflections with I > 2σ(I)
Radiation source: Incoatec microsource	Rint = 0.065
ω scans	θmax = 26.5°, θmin = 2.5°
Absorption correction: multi-scan (SADABS; Bruker, 2008)	h = −18→20
Tmin = 0.622, Tmax = 0.745	k = −20→20
22801 measured reflections	l = −26→35
3877 independent 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)] = 0.036	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.077	H-atom parameters constrained
S = 1.03	w = 1/[σ^2(Fo^2) + (0.0276P)^2] where P = (Fo^2 + 2Fc^2)/3
3877 reflections	(Δ/σ)max = 0.006
231 parameters	Δρmax = 0.79 e Å^−3
0 restraints	Δρmin = −1.00 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.

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

	x	y	z	Uiso*/Ueq
Ni1	0.0000	0.2500	0.78471 (2)	0.01796 (15)
S1	−0.11466 (6)	−0.02162 (6)	0.77532 (4)	0.0328 (3)
N1	−0.07587 (17)	0.14614 (18)	0.78356 (10)	0.0202 (7)
N2	0.07433 (17)	0.19832 (17)	0.83794 (10)	0.0178 (6)
N3	−0.07086 (17)	0.30733 (17)	0.73194 (10)	0.0191 (7)
C1	0.0871 (2)	0.1165 (2)	0.84181 (13)	0.0217 (8)
H1	0.0689	0.0814	0.8173	0.026*
C2	0.1256 (2)	0.0816 (2)	0.88005 (13)	0.0232 (8)
H2	0.1339	0.0236	0.8812	0.028*
C3	0.1522 (2)	0.1308 (2)	0.91691 (12)	0.0214 (8)
C4	0.1408 (2)	0.2151 (2)	0.91201 (12)	0.0211 (8)
H4	0.1597	0.2516	0.9356	0.025*
C5	0.1020 (2)	0.2462 (2)	0.87280 (12)	0.0209 (8)
H5	0.0947	0.3042	0.8704	0.025*
C6	0.1881 (2)	0.0927 (2)	0.95838 (13)	0.0269 (9)
H6	0.2041	0.0365	0.9559	0.032*
C7	0.2004 (2)	0.1291 (3)	0.99889 (14)	0.0350 (10)
H7A	0.1854	0.1853	1.0030	0.042*
H7B	0.2242	0.0991	1.0240	0.042*
C8	−0.0340 (2)	0.3445 (2)	0.69534 (12)	0.0222 (8)
H8	0.0245	0.3487	0.6954	0.027*
C9	−0.0764 (2)	0.3768 (2)	0.65782 (13)	0.0242 (9)
H9	−0.0472	0.4015	0.6327	0.029*
C10	−0.1621 (2)	0.3729 (2)	0.65694 (13)	0.0240 (8)
C11	−0.1999 (2)	0.3365 (2)	0.69524 (14)	0.0266 (9)
H11	−0.2584	0.3333	0.6967	0.032*
C12	−0.1529 (2)	0.3049 (2)	0.73121 (13)	0.0251 (9)
H12	−0.1807	0.2801	0.7568	0.030*
C13	−0.2112 (3)	0.4051 (2)	0.61799 (15)	0.0368 (11)
H13	−0.2695	0.4006	0.6205	0.044*
C14	−0.1824 (3)	0.4394 (3)	0.58024 (15)	0.0462 (12)
H14A	−0.1245	0.4454	0.5761	0.055*
H14B	−0.2192	0.4585	0.5569	0.055*
C15	−0.0925 (2)	0.0770 (2)	0.78008 (12)	0.0220 (8)
I1	0.06962 (2)	0.03854 (2)	1.11334 (2)	0.03788 (11)
F1	−0.06105 (14)	0.12477 (14)	0.94756 (8)	0.0441 (7)
F2	−0.00803 (16)	0.15593 (15)	1.03344 (9)	0.0478 (7)
C16	−0.0313 (2)	0.0619 (3)	0.97335 (15)	0.0336 (10)
C17	0.0285 (2)	0.0164 (3)	1.04525 (14)	0.0333 (10)
C18	−0.0037 (2)	0.0788 (3)	1.01741 (16)	0.0347 (10)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ni1	0.0152 (3)	0.0198 (3)	0.0189 (4)	0.0001 (3)	0.000	0.000
S1	0.0331 (6)	0.0248 (5)	0.0404 (7)	−0.0060 (4)	−0.0020 (5)	−0.0011 (5)
N1	0.0175 (15)	0.0241 (17)	0.0190 (18)	0.0004 (12)	−0.0003 (13)	−0.0001 (13)
N2	0.0164 (15)	0.0168 (15)	0.0203 (18)	0.0013 (12)	0.0014 (12)	−0.0028 (13)
N3	0.0170 (15)	0.0226 (16)	0.0178 (18)	−0.0005 (12)	−0.0003 (13)	−0.0007 (13)
C1	0.0191 (18)	0.0201 (18)	0.026 (2)	−0.0005 (15)	−0.0011 (16)	−0.0043 (16)
C2	0.0186 (18)	0.0188 (18)	0.032 (2)	0.0044 (14)	0.0021 (16)	0.0011 (16)
C3	0.0151 (17)	0.0239 (19)	0.025 (2)	0.0014 (15)	0.0008 (15)	0.0050 (16)
C4	0.0204 (19)	0.0240 (19)	0.019 (2)	0.0011 (15)	−0.0009 (15)	−0.0042 (15)
C5	0.0247 (19)	0.0180 (18)	0.020 (2)	0.0017 (15)	0.0019 (16)	−0.0004 (15)
C6	0.0205 (19)	0.028 (2)	0.032 (3)	0.0029 (16)	−0.0036 (17)	0.0113 (18)
C7	0.032 (2)	0.037 (2)	0.035 (3)	−0.0012 (19)	−0.009 (2)	0.010 (2)
C8	0.0168 (18)	0.026 (2)	0.024 (2)	0.0001 (15)	0.0017 (15)	−0.0009 (16)
C9	0.031 (2)	0.0215 (19)	0.020 (2)	0.0017 (16)	0.0036 (17)	0.0009 (16)
C10	0.029 (2)	0.0189 (19)	0.024 (2)	0.0052 (16)	−0.0103 (17)	−0.0042 (16)
C11	0.0189 (19)	0.022 (2)	0.039 (3)	0.0003 (15)	−0.0050 (17)	0.0007 (17)
C12	0.0175 (18)	0.028 (2)	0.030 (2)	−0.0020 (15)	0.0003 (16)	0.0005 (17)
C13	0.044 (3)	0.024 (2)	0.042 (3)	−0.0025 (18)	−0.021 (2)	0.003 (2)
C14	0.073 (4)	0.033 (3)	0.033 (3)	0.016 (2)	−0.020 (2)	−0.005 (2)
C15	0.0154 (18)	0.033 (2)	0.017 (2)	0.0035 (16)	−0.0006 (15)	0.0003 (17)
I1	0.02717 (15)	0.04786 (19)	0.0386 (2)	−0.00369 (12)	−0.00040 (12)	0.01396 (14)
F1	0.0450 (15)	0.0412 (15)	0.0461 (16)	0.0175 (12)	0.0013 (12)	0.0217 (12)
F2	0.0542 (17)	0.0403 (15)	0.0488 (17)	0.0080 (12)	−0.0012 (13)	0.0109 (12)
C16	0.023 (2)	0.042 (3)	0.036 (3)	0.0099 (18)	0.0029 (18)	0.022 (2)
C17	0.024 (2)	0.044 (3)	0.032 (3)	0.0037 (18)	0.0043 (18)	0.018 (2)
C18	0.026 (2)	0.032 (2)	0.046 (3)	0.0025 (18)	0.004 (2)	0.012 (2)

Geometric parameters (Å, º)

Ni1—N1	2.084 (3)	C7—H7A	0.9500
Ni1—N1^i	2.084 (3)	C7—H7B	0.9500
Ni1—N3^i	2.115 (3)	C8—C9	1.380 (5)
Ni1—N2	2.118 (3)	C8—H8	0.9500
Ni1—N3	2.115 (3)	C9—C10	1.391 (5)
Ni1—N2^i	2.118 (3)	C9—H9	0.9500
S1—C15	1.643 (4)	C10—C11	1.389 (5)
N1—C15	1.157 (4)	C10—C13	1.468 (5)
N2—C5	1.343 (4)	C11—C12	1.381 (5)
N2—C1	1.346 (4)	C11—H11	0.9500
N3—C12	1.331 (4)	C12—H12	0.9500
N3—C8	1.350 (4)	C13—C14	1.304 (6)
C1—C2	1.384 (5)	C13—H13	0.9500
C1—H1	0.9500	C14—H14A	0.9500
C2—C3	1.393 (5)	C14—H14B	0.9500
C2—H2	0.9500	I1—C17	2.096 (4)
C3—C4	1.385 (5)	F1—C16	1.349 (4)
C3—C6	1.461 (5)	F2—C18	1.334 (5)
C4—C5	1.384 (5)	C16—C18	1.369 (6)
C4—H4	0.9500	C16—C17^ii	1.377 (6)
C5—H5	0.9500	C17—C16^ii	1.377 (6)
C6—C7	1.319 (5)	C17—C18	1.390 (5)
C6—H6	0.9500
N1—Ni1—N1^i	178.17 (16)	C7—C6—C3	126.1 (4)
N1—Ni1—N3^i	87.37 (11)	C7—C6—H6	116.9
N1^i—Ni1—N3^i	91.32 (11)	C3—C6—H6	116.9
N1—Ni1—N3	91.32 (11)	C6—C7—H7A	120.0
N1^i—Ni1—N3	87.37 (11)	C6—C7—H7B	120.0
N3^i—Ni1—N3	88.56 (15)	H7A—C7—H7B	120.0
N1—Ni1—N2	91.59 (11)	N3—C8—C9	123.8 (3)
N1^i—Ni1—N2	89.73 (11)	N3—C8—H8	118.1
N3^i—Ni1—N2	91.95 (10)	C9—C8—H8	118.1
N3—Ni1—N2	177.07 (11)	C8—C9—C10	119.6 (3)
N1—Ni1—N2^i	89.73 (11)	C8—C9—H9	120.2
N1^i—Ni1—N2^i	91.59 (11)	C10—C9—H9	120.2
N3^i—Ni1—N2^i	177.07 (11)	C11—C10—C9	116.4 (3)
N3—Ni1—N2^i	91.95 (10)	C11—C10—C13	121.0 (4)
N2—Ni1—N2^i	87.69 (15)	C9—C10—C13	122.6 (4)
C15—N1—Ni1	157.0 (3)	C12—C11—C10	120.4 (3)
C5—N2—C1	117.1 (3)	C12—C11—H11	119.8
C5—N2—Ni1	119.9 (2)	C10—C11—H11	119.8
C1—N2—Ni1	122.4 (2)	N3—C12—C11	123.5 (4)
C12—N3—C8	116.3 (3)	N3—C12—H12	118.3
C12—N3—Ni1	122.7 (2)	C11—C12—H12	118.3
C8—N3—Ni1	120.9 (2)	C14—C13—C10	126.1 (4)
N2—C1—C2	122.5 (3)	C14—C13—H13	116.9
N2—C1—H1	118.7	C10—C13—H13	116.9
C2—C1—H1	118.7	C13—C14—H14A	120.0
C1—C2—C3	120.5 (3)	C13—C14—H14B	120.0
C1—C2—H2	119.7	H14A—C14—H14B	120.0
C3—C2—H2	119.7	N1—C15—S1	179.2 (4)
C4—C3—C2	116.5 (3)	F1—C16—C18	118.2 (4)
C4—C3—C6	123.5 (3)	F1—C16—C17^ii	119.7 (4)
C2—C3—C6	120.0 (3)	C18—C16—C17^ii	122.1 (4)
C5—C4—C3	120.2 (3)	C16^ii—C17—C18	117.4 (4)
C5—C4—H4	119.9	C16^ii—C17—I1	120.6 (3)
C3—C4—H4	119.9	C18—C17—I1	122.1 (3)
N2—C5—C4	123.2 (3)	F2—C18—C16	119.3 (4)
N2—C5—H5	118.4	F2—C18—C17	120.2 (4)
C4—C5—H5	118.4	C16—C18—C17	120.5 (4)

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