A new platinum–bromine cyclo­hexane­diamine complex from the family of cancer cytostatics

Another new substance from the family of Pt-based coord­ination complexes with potential use in cancer chemotherapy has been synthesized, crystallized and structurally characterized. In this compound {systematic name cis-dibromido[(1R,2R)-cyclo­hexane-1,2-diamine-κ²N,N′]platinum(II)}, cis-[PtBr₂(C₆H₁₄N₂)], there are two mol­ecules with very similar conformations in the asymmetric unit. The component species inter­act by way of N—H...Br and C—H...Br hydrogen bonds to give two-dimensional networks which lie parallel to the (100) plane.

S1. Comment

Platinum complexes belong to the oldest but still used and studied group of anticancer cytostatics. Some of the novel structures are based on platinum complexes with the trans-configured (1R,2R)-cyclohexane-1,2-diamine (DACH) carrier ligand and various leaving groups. The title compound, cis-[PtBr₂(DACH)], (I), belongs to the class of structurally similar complexes, which includes cis-[PtCl₂(DACH)], cis-[PtI₂(DACH)] and cis-[Pt(NO₃)₂(DACH)], and it is possible to use it as a precursor not only for the preparation of the currently used cytostatic oxaliplatin (Abu-Surrah & Kettunen, 2006) but also for new cytostatics of the fourth generation which are now being developed, e.g. complex AP5346 (Galanski et al., 2005). The cytostatic effects of (I) have been tested in mice under the code NSC-289559 against leukaemia strain P388 (Noji et al., 1981), but it is not currently in clinical use. Compound (I) is a yellow crystalline substance which is sparingly soluble in water (less than 0.3 g l^-1). The crystallographic data of (I) have hitherto not been described, but the structure of its isomeric analogue with the cis-cyclohexane-1,2-diamine ligand, cis-[Pt(cis-DACH)Br₂], has been reported previously (Lock & Pilon, 1981).

The single-crystal structure of (I) is composed of discrete molecules in the monoclinic space group P2₁, with two molecules, A and B, in the asymmetric unit (Fig. 1). The molecule is formed by one cyclohexane ring with a chair conformation, and a five-membered diamine ring involving the central atom Pt and two bromide ligands. Most bond lengths and angles fall within expected ranges [Standard reference?].

The molecules of (I) are approximately planar, with a dihedral angle between the Br2A/Br1A/N2A/N1A plane and the cyclohexane ring plane, C3A/C6A/N2A/N1A, of 4.2 (5)° in molecule A. The corresponding dihedral angle in molecule B is 2.0 (5)°. These angles are very similar to those found in cis-[Pt(NO₃)₂(DACH)] (Pažout et al., 2010), but quite different to those in cis-[PtBr₂(cis-DACH)] and cis-[PtCl₂(cis-DACH)], where the corresponding dihedral angles are between 50 and 70° (Lock & Pilon, 1981). The average Pt—N bond length of 2.04 (2) Å is very similar to the same bond in cis-[PtBr₂(cis-DACH)] and cis-[PtCl₂(cis-DACH)] [2.05 (2) and 2.03 (3) Å, respectively; Lock & Pilon, 1981]. There are no significant differences between the Pt—Br distances of these three structures.

Molecules A and B have very similar geometries and conformations, with an r.m.s fit of the non-H atoms of the two molecules of 0.077 Å. The molecular planes of molecules A and B are essentially coplanar, with the angle between planes C3A/C6A/N1A/N2A and C3B/C6B/N1B/N2B being 1.4 (6)°.

The crystal structure of (I) is held together by hydrogen bonds, all of them having a Br atom as an acceptor. There are two systems of intermolecular interactions. One involves molecules whose molecular planes all lie in the same layer (Fig. 2) and is formed by N—H···Br interactions linking neighbouring molecules into ribbons which run parallel to the c axis. The other is between these layers (Fig. 3) and is formed by N—H···Br and C—H···Br interactions linking layers of ribbons stacked along the b axis. Each stack is formed solely of either molecules A or molecules B. The distance between the layers is exactly half of the unit cell b parameter, i.e. 3.56 Å, which is considerably less than the corresponding separation of 3.74 Å found in cis-[PtI₂(DACH)] (Pažout et al., 2011).

The first system is represented by two parallel sequences of hydrogen bonds linking an N atom of the diamine group with the Br atom of a neighbouring molecule, one sequence being Br2B···(H1N2A/H2N2A chelated)—N2A and N1A—H2N1A···Br1Bⁱ, and the other being N2B—H2N2B···Br2A and Br1A···(H1N1Bⁱ/H2N1Bⁱ chelated)—N1Bⁱ, as shown in Fig. 2 (symmetry code given in Table 1). We have concluded that the second H atoms on N1A and N2B do not form hydrogen bonds, since the H···Br distances are too long (3.27 and 3.33 Å, respectively) and the N—H···Br angle is less than 100° (98 and 97°, respectively).

The layers of chains (the second system) are held together by eight N—H···Br hydrogen bonds and four C—H···Br hydrogen bonds, as depicted in Fig. 3. Molecules B are involved in the following four N—H···Br hydrogen bonds: Br2B^vi···H2N1B—N1B, Br1B^vi···H1N2B—N2B, N1B^vi—H1N1B^vi···Br2B, N2B^vi—H2N2B^vi···Br1B, and two C—H···Br hydrogen bonds: Br2B^vi···H1C1B—C1B and C2B^vi—H1C2B^vi···Br1B. The stack of molecules A is held by the following four N—H···Br hydrogen bonds: N1Aⁱⁱⁱ —H1N1Aⁱⁱⁱ···Br2A, N2Aⁱⁱⁱ—H2N2Aⁱⁱⁱ···Br1A, Br2Aⁱⁱⁱ···H2N1A—N1A and Br1Aⁱⁱⁱ···H1N2A—N2A, and two C—H···Br hydrogen bonds: C2Aⁱⁱⁱ—H1C2Aⁱⁱⁱ···Br1A and Br2Aⁱⁱⁱ···H1C1A—C1A. Full details of these hydrogen bonds and the symmetry codes are given in Table 1. Only H···Br distances up to 3.2 Å were considered and included. Similar N—H···Br contacts (N···Br distances 3.550 and 3.474 Å) were observed by Lock & Pilon (1981), who considered the forces within and between the layers to be van der Waals. Adding geometrically positioned H atoms (N—H = 0.96 Å) to their structure, the model for which did not include H atoms, shows that all N—H···Br contacts are hydrogen bonds with H···Br distances between 2.727 and 2.830 Å.

Comparing (I) with the closest structure among the DACH-Pt complexes, cis-[PtI₂(DACH)] (Pažout et al., 2011), the arrangement of hydrogen-bonded chains within one layer is the same. Although the unit cells of both structures are monoclinic and their volumes are similar, the iodine complex has a C-centred monoclinic unit cell with Z' = 1, while the bromine complex possesses a primitive unit cell with Z' = 2. The similarity of the two structures was tested in two supergroups. Both structures are very similar and can be described in the supergroup C2/m, where they are isostructural with regard to positions. For this purpose, the P cell had to be transformed. For both structures, fairly good refinement R factors can be obtained. However, for the P cell data (bromine complex, this paper) many reflections with significant intensity are required to be systematically absent under the C-centring and are discarded. Clearly, this structure is not C-centred. On top of that, for the highest symmetry space group C2/m the cyclohexane ring with a chair conformation would have to be planar or disordered, and disorder is not evident in any of the lower symmetry space groups. The structure refinement then produces huge atomic displacement parameters U₂₂. The supergroup C2 was also tested. This comes out as exactly the correct space group for the C-cell data (iodine complex), but for the P-cell data a great number of reflections with significant intensity are discarded as being absent under the lattice-centring condition. The structures can be refined with reasonable R factors but the atomic displacement parameters for the P-cell data are again unacceptable. The conclusion is that, using a rough description, the structures are isostructural, but subtle violations of translational symmetry are evident and the presented solutions are indeed correct, i.e. the space group for the bromine complex is P2₁ and that for the iodine complex is C2.

Related literature

For related literature, see: Abu-Surrah & Kettunen (2006); Galanski et al. (2005); Lock & Pilon (1981); Noji et al. (1981); Oxford (2010); Pažout et al. (2010, 2011).

S2. Experimental

The title compound was prepared from a suspension of cis-dichlorido[(1R,2R)-cyclohexane-1,2-diamine-κ²N,N']platinum(II) (365 mg, 0.959 mmol) in water (300 ml), which was stirred in the absence of light at 318 K for 70 min. A solution of AgNO₃ (326 mg, 1.919 mmol) in water (30 ml) was then added dropwise and the reaction mixture was stirred in the absence of light at 318 K for 1.5 h. Subsequently, the reaction mixture was cooled to 277 K overnight. The AgCl side-product was removed by filtration through an ultrafilter (0.22 mm, Sigma–Aldrich) and a layer of active carbon. A solution of KBr (228 mg, 1.916 mmol) in water (30 ml) was then added at room temperature and the reaction mixture was stirred in the absence of light at 318 K for 75 min. A yellow precipitate formed and the reaction mixture was cooled to 277 K overnight. The yellow product was separated the next day by filtration through an ultrafilter (0.22 mm, Sigma–Aldrich) and rinsed with water (100 ml) (yield 87%, 389.4 mg, 0.83 mmol). Single crystals suitable for crystal structure analysis were obtained from a solution of (I) in water by spontaneous precipitation under slow programmed cooling. The structure was confirmed by liquid chromatography–mass spectroscopy analysis, and the purity of the desired substance was verified by high-performance liquid chromatography–UV analysis.

S3. Refinement

The crystal examined was a twin, with the twinning operation being a rotation of 180° around a*. This twinning resulted in a partial overlap of reflections. To achieve a better separation of reflections, Cu radiation was used instead of Mo radiation. A meticulous absorption correction was applied consisting of: (i) a shape correction; (ii) a multi-scan correction [ABSPACK in CrysAlis PRO (Oxford Diffraction, 2010)], which can account for both twin components; and (iii) scaling of frames. Point (iii) led to an almost constant scale and a good R_int value. Various procedures for treating the twin components were tried, consisting of determining the twin matrix and reading independently indexed domains, with the subsequent use of either one domain or both and testing to cull (throw away) reflections belonging to different domains with close θ angles. By means of the θ angle a complete overlap was tested when defined from zero to 0.3°. Moreover, refinement based on a reflection file containing the non-overlapped and overlapped reflections from both twin domains was also tried. In our case, the best results were achieved when ignoring twinning, using one domain (the stronger one) and no culling of reflections. The volume fraction of the stronger domain was 0.925 (6) and that of the weaker was 0.075 (5).

Although from a chemical point of view a centrosymmetric space group (SG) is ruled out because the DACH ligand is enantiomerically pure, the structure of (I) exhibits strong pseudosymmetry, corresponding closely to the SG P2₁/c. Therefore, another key point from a crystallographic point of view was to test the centre of inversion. For the structure solution in P2₁/c, the positions of the Br and Pt atoms correspond to this symmetry, while the organic part of the molecule looks disordered. Using this SG, the cyclohexane ring showed an effect that looked like disorder, manifesting itself in large displacement parameters for the C atoms. However, meaningful configurations that would form this disorder, such as two interwoven chairs of the cyclohexane ring, failed to be identified. The conclusion is that P2₁/c is not the correct SG.

Because the SG Pc has many more systematically extinct reflections than P2₁, another test was made using Pc. However, here the geometry of the organic part did not make sense either (similar to what happened with P2₁/c). What we are left with is the SG P2₁ and in this SG the structure comes out correctly without disorder. Therefore, the model was transformed to subgroup P2₁ and refined as an inversion twin. The Flack parameter of 0.04 (2) shows that the crystals are enantiomerically pure and have the correct absolute configuration. Finally, the reflections forbidden in P2₁/c are indeed present. There are 15 observed h0l reflections with l odd with intensities between 5.5 and 3σ(I), and several hundred reflections with I < 3σ(I). The average I/σ(I) for all reflections forbidden in P2₁/c is just 1.01, but this is quite understandable in a structure with several heavy atoms fitting the P2₁/c symmetry and a light organic component of the molecule breaking this symmetry.

All H atoms were positioned geometrically and refined using a riding model, with C—H = 0.96 Å and N—H = 0.87 Å, and with Ui_so(H) = 1.2U_eq(C,N). The anisotropic refinement of atom N1B resulted in the displacement parameters not being positive definite, so this atom was refined isotropically. A similar situation was observed in the structure of cis-[PtI₂(DACH)] (Pažout et al., 2011).

Computing details

Data collection: CrysAlis PRO (Oxford Diffraction, 2010); cell refinement: CrysAlis PRO (Oxford Diffraction, 2010); data reduction: CrysAlis PRO (Oxford Diffraction, 2010); program(s) used to solve structure: SUPERFLIP (Palatinus & Chapuis, 2007); program(s) used to refine structure: JANA2006 (Petříček et al., 2006); molecular graphics: ORTEP-3 (Farrugia, 1999) and Mercury (Macrae et al., 2008); software used to prepare material for publication: JANA2006 (Petříček et al., 2006).

Figures

	Fig. 1. The two independent molecules of (I), showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level.
	Fig. 2. Chelating N—H···Br hydrogen bonds (dashed lines) linking neighbouring molecules into a ribbon along the c axis. The view is down the b axis.
	Fig. 3. The formation of two types of N—H···Br and C—H···Br hydrogen bonds (dashed lines), linking layers of ribbons parallel to (010).

cis-dibromido[(1R,2R)-cyclohexane-1,2-diamine- κ²N,N']platinum(II)}

Crystal data

[PtBr2(C6H14N2)]	F(000) = 848
Mr = 469.1	Dx = 2.831 Mg m^−3
Monoclinic, P21	Cu Kα radiation, λ = 1.54184 Å
Hall symbol: P 2yb	Cell parameters from 8285 reflections
a = 11.716 (3) Å	θ = 3.4–66.5°
b = 7.1266 (14) Å	µ = 31.95 mm^−1
c = 13.288 (2) Å	T = 120 K
β = 97.423 (17)°	Needle, yellow
V = 1100.2 (4) Å^3	0.63 × 0.07 × 0.03 mm
Z = 4

Data collection

Oxford MODEL? CCD area-detector diffractometer	3587 independent reflections
Radiation source: X-ray tube	3264 reflections with I > 3σ(I)
Graphite monochromator	Rint = 0.047
Detector resolution: 10.3784 pixels mm^-1	θmax = 66.5°, θmin = 3.4°
ω scans	h = −13→13
Absorption correction: multi-scan (CrysAlis PRO; Oxford Diffraction, 2010)	k = −8→8
Tmin = 0.173, Tmax = 1.000	l = −15→13
10413 measured reflections

Refinement

Refinement on F	H-atom parameters constrained
R[F^2 > 2σ(F^2)] = 0.034	Weighting scheme based on measured s.u.'s w = 1/(σ^2(F) + 0.0001F^2)
wR(F^2) = 0.040	(Δ/σ)max = 0.020
S = 2.16	Δρmax = 1.96 e Å^−3
3587 reflections	Δρmin = −1.92 e Å^−3
194 parameters	Absolute structure: Flack (1983), with 1484 Friedel pairs
0 restraints	Absolute structure parameter: 0.04 (2)
113 constraints

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

	x	y	z	Uiso*/Ueq
Pt1A	0.51201 (5)	0.477736	0.50286 (3)	0.0196 (4)
Pt1B	0.48887 (5)	0.52156 (7)	−0.00086 (3)	0.0170 (3)
Br2A	0.65942 (13)	0.4859 (3)	0.38829 (9)	0.0258 (6)
Br2B	0.34236 (13)	0.5325 (3)	0.11445 (9)	0.0234 (5)
Br1A	0.64835 (13)	0.4652 (3)	0.65878 (9)	0.0278 (6)
Br1B	0.35166 (12)	0.5141 (3)	−0.15597 (8)	0.0255 (5)
N2A	0.3874 (9)	0.476 (2)	0.3810 (7)	0.027 (4)
N2B	0.6142 (9)	0.524 (2)	0.1205 (6)	0.023 (3)
N1A	0.3749 (10)	0.482 (2)	0.5842 (7)	0.035 (4)
N1B	0.6229 (8)	0.5179 (18)	−0.0839 (7)	0.018 (2)*
C2A	0.2729 (9)	0.4188 (18)	0.4180 (7)	0.024 (3)
C2B	0.7284 (10)	0.4801 (16)	0.0846 (8)	0.024 (3)
C3A	0.1712 (11)	0.455 (2)	0.3399 (8)	0.031 (4)
C3B	0.8317 (12)	0.533 (2)	0.1586 (9)	0.035 (5)
C4A	0.0631 (11)	0.401 (2)	0.3854 (9)	0.043 (5)
C4B	0.9446 (11)	0.494 (2)	0.1158 (9)	0.039 (4)
C1A	0.2679 (10)	0.5253 (18)	0.5164 (7)	0.026 (3)
C1B	0.7311 (9)	0.5737 (18)	−0.0160 (7)	0.023 (3)
C6A	0.1585 (12)	0.469 (2)	0.5627 (9)	0.031 (5)
C6B	0.8415 (11)	0.528 (2)	−0.0631 (8)	0.028 (4)
C5A	0.0539 (12)	0.505 (2)	0.4833 (9)	0.039 (4)
C5B	0.9471 (11)	0.588 (2)	0.0142 (9)	0.035 (4)
H1C2A	0.269784	0.286003	0.42935	0.0286*
H1C2B	0.733794	0.346222	0.07859	0.0292*
H1C3A	0.177189	0.380093	0.280878	0.0372*
H2C3A	0.168134	0.586376	0.323017	0.0372*
H1C3B	0.830643	0.464447	0.220603	0.0416*
H2C3B	0.827583	0.663916	0.175138	0.0416*
H1C4A	−0.003548	0.426786	0.337389	0.0513*
H2C4A	0.063688	0.268017	0.398031	0.0513*
H1C4B	1.00812	0.537911	0.162809	0.0469*
H2C4B	0.954042	0.361098	0.10856	0.0469*
H1C1A	0.263279	0.658384	0.50548	0.0316*
H1C1B	0.733071	0.707491	−0.007465	0.0273*
H1C6A	0.162138	0.338447	0.580001	0.0376*
H2C6A	0.152579	0.544499	0.621739	0.0376*
H1C6B	0.841556	0.596456	−0.125156	0.0337*
H2C6B	0.845028	0.394911	−0.074973	0.0337*
H1C5A	−0.014846	0.466933	0.509948	0.047*
H2C5A	0.047039	0.637244	0.469663	0.047*
H1C5B	1.016977	0.555688	−0.012174	0.0416*
H2C5B	0.946156	0.722108	0.02276	0.0416*
H1N2A	0.380638	0.588364	0.354809	0.0329*
H2N2A	0.405155	0.395434	0.336583	0.0329*
H1N2B	0.617312	0.634497	0.148605	0.0272*
H2N2B	0.598984	0.439573	0.16419	0.0272*
H1N1A	0.368297	0.372691	0.612254	0.0416*
H2N1A	0.386308	0.566565	0.631477	0.0416*
H1N1B	0.630993	0.405267	−0.10719	0.0219*
H2N1B	0.609862	0.597402	−0.133692	0.0219*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Pt1A	0.0232 (4)	0.0265 (11)	0.0093 (2)	−0.0015 (3)	0.0022 (2)	−0.00048 (19)
Pt1B	0.0221 (3)	0.0194 (9)	0.0094 (2)	0.0006 (3)	0.00207 (19)	−0.00016 (18)
Br2A	0.0274 (7)	0.0349 (14)	0.0163 (5)	−0.0014 (8)	0.0071 (4)	0.0008 (6)
Br2B	0.0286 (7)	0.0256 (11)	0.0166 (5)	−0.0002 (7)	0.0053 (4)	−0.0017 (6)
Br1A	0.0325 (8)	0.0371 (13)	0.0129 (5)	−0.0039 (8)	−0.0006 (5)	−0.0004 (6)
Br1B	0.0295 (8)	0.0317 (12)	0.0144 (5)	0.0024 (8)	−0.0009 (5)	−0.0011 (6)
N2A	0.026 (6)	0.039 (8)	0.018 (5)	−0.004 (7)	0.007 (4)	−0.009 (6)
N2B	0.033 (6)	0.027 (7)	0.009 (4)	0.000 (7)	0.008 (4)	0.002 (6)
N1A	0.034 (6)	0.061 (9)	0.011 (4)	0.001 (5)	0.010 (3)	−0.006 (4)
C2A	0.022 (5)	0.030 (7)	0.021 (4)	−0.011 (5)	0.008 (4)	0.001 (5)
C2B	0.026 (6)	0.019 (6)	0.027 (5)	−0.008 (5)	−0.001 (4)	0.002 (4)
C3A	0.024 (7)	0.051 (10)	0.017 (5)	−0.003 (8)	0.000 (4)	0.006 (7)
C3B	0.031 (8)	0.050 (10)	0.020 (6)	0.002 (9)	−0.006 (5)	−0.004 (7)
C4A	0.024 (6)	0.063 (10)	0.039 (6)	0.000 (7)	−0.005 (5)	0.005 (7)
C4B	0.019 (6)	0.061 (10)	0.037 (6)	0.009 (7)	0.001 (4)	0.006 (6)
C1A	0.033 (6)	0.034 (7)	0.015 (4)	0.001 (6)	0.014 (4)	−0.002 (5)
C1B	0.026 (5)	0.030 (6)	0.012 (4)	0.004 (5)	0.002 (3)	0.003 (4)
C6A	0.029 (8)	0.034 (9)	0.032 (6)	−0.010 (8)	0.011 (5)	−0.006 (7)
C6B	0.020 (7)	0.039 (9)	0.028 (6)	0.009 (8)	0.012 (5)	0.011 (7)
C5A	0.036 (7)	0.045 (9)	0.038 (6)	−0.001 (7)	0.012 (5)	0.005 (6)
C5B	0.031 (6)	0.039 (8)	0.032 (6)	0.004 (7)	−0.001 (4)	−0.004 (5)

Geometric parameters (Å, º)

Pt1A—Br2A	2.4462 (17)	C3A—C4A	1.52 (2)
Pt1A—Br1A	2.4489 (16)	C3A—H1C3A	0.96
Pt1A—N2A	2.035 (9)	C3A—H2C3A	0.96
Pt1A—N1A	2.048 (12)	C3B—C4B	1.53 (2)
Pt1B—Br2B	2.4455 (17)	C3B—H1C3B	0.96
Pt1B—Br1B	2.4453 (16)	C3B—H2C3B	0.96
Pt1B—N2B	2.036 (9)	C4A—C5A	1.515 (19)
Pt1B—N1B	2.032 (10)	C4A—H1C4A	0.96
N2A—C2A	1.543 (16)	C4A—H2C4A	0.96
N2A—H1N2A	0.87	C4B—C5B	1.513 (18)
N2A—H2N2A	0.87	C4B—H1C4B	0.96
N2B—C2B	1.510 (16)	C4B—H2C4B	0.96
N2B—H1N2B	0.87	C1A—C6A	1.545 (19)
N2B—H2N2B	0.87	C1A—H1C1A	0.96
N1A—C1A	1.479 (15)	C1B—C6B	1.543 (17)
N1A—H1N1A	0.87	C1B—H1C1B	0.96
N1A—H2N1A	0.87	C6A—C5A	1.532 (18)
N1B—C1B	1.511 (14)	C6A—H1C6A	0.96
N1B—H1N1B	0.87	C6A—H2C6A	0.96
N1B—H2N1B	0.87	C6B—C5B	1.564 (17)
C2A—C3A	1.498 (15)	C6B—H1C6B	0.96
C2A—C1A	1.519 (15)	C6B—H2C6B	0.96
C2A—H1C2A	0.96	C5A—H1C5A	0.96
C2B—C3B	1.506 (17)	C5A—H2C5A	0.96
C2B—C1B	1.499 (14)	C5B—H1C5B	0.96
C2B—H1C2B	0.96	C5B—H2C5B	0.96
Br2A—Pt1A—Br1A	95.26 (5)	H1C3A—C3A—H2C3A	110.9199
Br2A—Pt1A—N2A	89.8 (3)	C2B—C3B—C4B	111.9 (10)
Br2A—Pt1A—N1A	173.1 (3)	C2B—C3B—H1C3B	109.4713
Br1A—Pt1A—N2A	174.5 (3)	C2B—C3B—H2C3B	109.4711
Br1A—Pt1A—N1A	91.4 (3)	C4B—C3B—H1C3B	109.471
N2A—Pt1A—N1A	83.6 (4)	C4B—C3B—H2C3B	109.4712
Br2B—Pt1B—Br1B	95.20 (5)	H1C3B—C3B—H2C3B	106.9789
Br2B—Pt1B—N2B	89.8 (3)	C3A—C4A—C5A	111.7 (12)
Br2B—Pt1B—N1B	174.0 (2)	C3A—C4A—H1C4A	109.4712
Br1B—Pt1B—N2B	175.0 (3)	C3A—C4A—H2C4A	109.4712
Br1B—Pt1B—N1B	90.7 (2)	C5A—C4A—H1C4A	109.471
N2B—Pt1B—N1B	84.4 (4)	C5A—C4A—H2C4A	109.4712
Pt1A—N2A—C2A	108.2 (6)	H1C4A—C4A—H2C4A	107.1325
Pt1A—N2A—H1N2A	109.4713	C3B—C4B—C5B	111.6 (11)
Pt1A—N2A—H2N2A	109.4711	C3B—C4B—H1C4B	109.471
C2A—N2A—H1N2A	109.4707	C3B—C4B—H2C4B	109.4715
C2A—N2A—H2N2A	109.4713	C5B—C4B—H1C4B	109.4712
H1N2A—N2A—H2N2A	110.7288	C5B—C4B—H2C4B	109.471
Pt1B—N2B—C2B	109.0 (6)	H1C4B—C4B—H2C4B	107.286
Pt1B—N2B—H1N2B	109.4714	N1A—C1A—C2A	107.2 (10)
Pt1B—N2B—H2N2B	109.4715	N1A—C1A—C6A	112.6 (9)
C2B—N2B—H1N2B	109.4708	N1A—C1A—H1C1A	109.0466
C2B—N2B—H2N2B	109.4709	C2A—C1A—C6A	109.9 (10)
H1N2B—N2B—H2N2B	109.947	C2A—C1A—H1C1A	111.8188
Pt1A—N1A—Br2A^i	98.4 (5)	C6A—C1A—H1C1A	106.3324
Pt1A—N1A—Br1A	49.3 (2)	N1B—C1B—C2B	107.6 (9)
Pt1A—N1A—Br1B^ii	133.3 (4)	N1B—C1B—C6B	112.6 (9)
Pt1A—N1A—C1A	110.0 (7)	N1B—C1B—H1C1B	109.7355
Pt1A—N1A—H1N1A	109.4707	C2B—C1B—C6B	112.5 (10)
Pt1A—N1A—H2N1A	109.4713	C2B—C1B—H1C1B	109.8611
C1A—N1A—H1N1A	109.4715	C6B—C1B—H1C1B	104.5385
C1A—N1A—H2N1A	109.471	C1A—C6A—C5A	108.3 (10)
H1N1A—N1A—H2N1A	108.9279	C1A—C6A—H1C6A	109.4712
Pt1B—N1B—C1B	108.7 (6)	C1A—C6A—H2C6A	109.4714
Pt1B—N1B—H1N1B	109.4713	C5A—C6A—H1C6A	109.4716
Pt1B—N1B—H2N1B	109.4709	C5A—C6A—H2C6A	109.4711
C1B—N1B—H1N1B	109.4715	H1C6A—C6A—H2C6A	110.6274
C1B—N1B—H2N1B	109.4713	C1B—C6B—C5B	107.9 (10)
H1N1B—N1B—H2N1B	110.2475	C1B—C6B—H1C6B	109.4713
N2A—C2A—C3A	112.3 (9)	C1B—C6B—H2C6B	109.4711
N2A—C2A—C1A	105.8 (9)	C5B—C6B—H1C6B	109.471
N2A—C2A—H1C2A	111.4008	C5B—C6B—H2C6B	109.4713
C3A—C2A—C1A	113.2 (10)	H1C6B—C6B—H2C6B	110.9544
C3A—C2A—H1C2A	103.7331	C4A—C5A—C6A	111.7 (12)
C1A—C2A—H1C2A	110.5064	C4A—C5A—H1C5A	109.4711
N2B—C2B—C3B	114.3 (9)	C4A—C5A—H2C5A	109.4713
N2B—C2B—C1B	108.2 (9)	C6A—C5A—H1C5A	109.471
N2B—C2B—H1C2B	107.678	C6A—C5A—H2C5A	109.4715
C3B—C2B—C1B	111.2 (10)	H1C5A—C5A—H2C5A	107.1192
C3B—C2B—H1C2B	104.3521	C4B—C5B—C6B	111.0 (11)
C1B—C2B—H1C2B	111.0036	C4B—C5B—H1C5B	109.4711
C2A—C3A—C4A	108.0 (10)	C4B—C5B—H2C5B	109.4712
C2A—C3A—H1C3A	109.471	C6B—C5B—H1C5B	109.4715
C2A—C3A—H2C3A	109.4712	C6B—C5B—H2C5B	109.4709
C4A—C3A—H1C3A	109.4713	H1C5B—C5B—H2C5B	107.9139
C4A—C3A—H2C3A	109.4714

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N2A—H1N2A···Br2B	0.87	3.19	3.536 (10)	107
N2A—H2N2A···Br2B	0.87	3.11	3.536 (10)	113
N2B—H2N2B···Br2A	0.87	2.99	3.539 (9)	123
N1A—H2N1A···Br1B^ii	0.87	2.93	3.507 (10)	126
N1B—H1N1B···Br1A^iii	0.87	3.17	3.491 (9)	104
N1B—H2N1B···Br1A^iii	0.87	3.00	3.491 (9)	118
N2A—H1N2A···Br1A^iv	0.87	2.71	3.540 (16)	160
N2A—H2N2A···Br1A^i	0.87	3.13	3.698 (16)	125
N1A—H1N1A···Br2A^i	0.87	2.78	3.581 (17)	155
N1A—H2N1A···Br2A^iv	0.87	3.04	3.639 (17)	128
N1B—H1N1B···Br2B^v	0.87	2.68	3.512 (13)	161
N1B—H2N1B···Br2B^vi	0.87	3.16	3.719 (13)	125
N2B—H1N2B···Br1B^vi	0.87	2.73	3.540 (15)	156
N2B—H2N2B···Br1B^v	0.87	3.09	3.679 (15)	127
C1A—H1C1A···Br2A^iv	0.96	2.82	3.581 (13)	137
C1B—H1C1B···Br2B^vi	0.96	2.80	3.585 (12)	139
C2A—H1C2A···Br1A^i	0.96	2.79	3.548 (13)	136
C2B—H1C2B···Br1B^v	0.96	2.82	3.610 (12)	141

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