Synthesis and crystal structure of [Zn6Br4(C9H18NO)4(OH)4]·2C3H6O2

Scheel, R.; Brieger, L.; Louven, K.; Strohmann, C.

doi:10.1107/S2056989020007100

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ISSN: 2056-9890

Volume 76| Part 7| July 2020| Pages 998-1002

https://doi.org/10.1107/S2056989020007100

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Synthesis and crystal structure of [Zn₆Br₄(C₉H₁₈NO)₄(OH)₄]·2C₃H₆O₂

Rebecca Scheel,^a Lukas Brieger,^a Kathrin Louven ^a and Carsten Strohmann ^a ^*

^aInorganic Chemistry, TU Dortmund University, Otto-Hahn Str.6, 44227 Dortmund, Germany
^*Correspondence e-mail: carsten.strohmann@tu-dortmund.de

Edited by W. T. A. Harrison, University of Aberdeen, Scotland (Received 5 May 2020; accepted 26 May 2020; online 2 June 2020)

The complete molecule of the hexametallic title complex, namely, tetrabromidotetra-μ-hydroxido-hexakis[μ-2-methyl-3-(pyrrolidin-1-yl)propan-2-olato]hexazinc(II) acetone disolvate, [Zn₆Br₄(C₉H₁₈NO)₄(OH)₄]·2C₃H₆O₂, is generated by a crystallographic centre of symmetry. Two of the unique zinc atoms adopt distorted ZnO₂NBr tetrahedral coordination geometries and the other adopts a ZnO₃N tetrahedral arrangement. Both unique alkoxide ligands are N,O-chelating and both hydroxide ions are μ² bridging. The crystal structure displays an O—H⋯O hydrogen bond between a μ²-OH group and an acetone solvent molecule. The Hirshfeld surface has been calculated and is described.

Keywords: crystal structure; zinc; aminoalkoxide; zinc alkoxide; hydroxide; hydrogen bonding.

CCDC reference: 2005919

1. Chemical context

Zinc complexes have a wide range of applications. For example they can be found as catalysts in organic chemistry or in the human body in enzymes, such as oxidoreductases, transferases, hydrolases, lyases, isomerases and ligases (Lipscomb & Sträter, 1996 ). As a result of the filled d¹⁰ shell of the Zn²⁺ cation, zinc complexes can exhibit different coordination geometries, including tetrahedral, trigonal–bipyramidal and octahedral (Kimura et al., 1997 ). The tetrahedral coordination sphere is the most common because the ligands have the largest separation from each other (Holm et al., 1996 ).

Zinc alkoxides find applications in many fields. They are used in organic catalysis, for example in the amplification of an enantiomer through an autocatalytic cycle by building a tetrameric zinc alkoxide as an intermediate (Shibata et al., 1997 ; Soai et al., 1995 ). In addition, they are also used as catalysts in polymerization reactions, for example for the ring-opening polymerization of lactides (Chen et al., 2006 , 2011 ). Moreover, zinc alkoxides are electronically favoured in comparison to the incorporation of hydroxide or water molecules (Bergquist & Parkin, 1999 ). Hence, zinc alkoxides are an important species in the human body for example for the liver alcohol dehydrogenase or the CO₂ transport through the circulatory system by carbonate anhydrase (Clegg et al., 1988 ; Siek et al., 2016 ). Liver alcohol dehydrogenase is an enzyme that catalyses the biological oxidation of alcohols to aldehydes and ketones (Bergquist et al., 2000 ). As part of this reaction, a tetrahedral zinc alkoxide complex is formed and after that, a formal hydride transfer occurs from the alkoxide to the oxidized form of NAD⁺ (see Fig. 1). The entire process depicted in Fig. 1 involves the removal of a ketone from the zinc atom.

Figure 1
Reaction scheme of the liver alcohol dehydrogenase cycle by the formation of a zinc alkoxide (Bergquist et al., 2000

In the title compound, (I), an acetone molecule interacts with the complex through hydrogen bonding. It can therefore be understood as an intermediate of the ketone removal during the dehydrogenation process shown in Fig. 1. The remaining interaction of the ketone with the zinc complex is interesting for a deeper understanding of the liver alcohol dehydrogenase cycle.

2. Structural commentary

Compound (I) was crystallized from a mixture of zinc bromide and an aminoalkoxide in an acetone/water/triethylamine mixture at 278 K. It crystallizes in the monoclinic crystal system in space group P2₁/n together with one solvent molecule of acetone and the complete hexa-metallic molecule is generated by crystallographic inversion symmetry. The structure of (I) is shown in Fig. 2 and selected bond lengths and angles are given in Table 1.

Table 1
Selected geometric parameters (Å, °)

Zn1—O1	1.9593 (9)	Zn2—O4	1.9401 (9)
Zn1—O2	1.9165 (10)	Zn2—N2	2.1358 (11)
Zn1—N1	2.1058 (11)	Zn3—O1ⁱ	1.9646 (9)
Zn1—Br1	2.3816 (2)	Zn3—O3ⁱ	1.9681 (9)
Zn2—O2	1.9310 (10)	Zn3—O4	1.9512 (9)
Zn2—O3	1.9147 (9)	Zn3—Br2	2.3722 (2)

O1—Zn1—Br1	114.12 (3)	O4—Zn2—N2	86.91 (4)
O1—Zn1—N1	88.54 (4)	O1ⁱ—Zn3—Br2	118.00 (3)
O2—Zn1—Br1	110.82 (3)	O1ⁱ—Zn3—O3ⁱ	106.38 (4)
O2—Zn1—O1	111.19 (4)	O3ⁱ—Zn3—Br2	111.70 (3)
O2—Zn1—N1	116.18 (4)	O4—Zn3—Br2	117.11 (3)
N1—Zn1—Br1	114.35 (3)	O4—Zn3—O1ⁱ	105.41 (4)
O2—Zn2—O4	116.23 (4)	O4—Zn3—O3ⁱ	95.52 (4)
O2—Zn2—N2	110.18 (4)	Zn1—O1—Zn3ⁱ	118.87 (5)
O3—Zn2—O2	108.79 (4)	Zn1—O2—Zn2	123.95 (5)
O3—Zn2—O4	120.54 (4)	Zn2—O3—Zn3ⁱ	133.08 (5)
O3—Zn2—N2	112.11 (4)	Zn2—O4—Zn3	120.17 (4)
Symmetry code: (i) -x+1, -y+1, -z+1.

Figure 2
The molecular structure of (I)

with atom labelling and 50% displacement ellipsoids. Atoms with superscript a are generated by the symmetry operation 1 − x, 1 − y, 1 − z.

The bond lengths between the zinc atom and the oxygen atom of the alkoxide ligand are 1.9593 (9) Å for Zn1—O1 and 1.9401 (9) Å for Zn2—O4. The bond length for Zn2 may be shorter because of the direct bonding of a bromide ion to Zn1. Bond lengths between a zinc atom and an alkoxide oxygen atom have been observed to be 1.936 (3) Å (Chen et al., 2014 ) and 1.971 (2) Å (Siek et al., 2016), thus the corresponding bonds in (I) lie between these limits. The bond lengths between the zinc atom and the bridging hydroxide O atom, Zn1—O2 and Zn2—O3, are 1.9165 (10) Å and 1.9147 (9) Å, respectively, which are elongated in comparison to a similar zinc–hydroxide bond in the literature, where the distance is 1.900 (2) Å (Siek et al., 2016). However, the Zn1—Br1 [2.3816 (2) Å] and the Zn3—Br2 bonds [2.3722 (2) Å] are similar to other zinc—bromine bonds in related complexes [e.g. 2.358 (1) and 2.401 (1) Å; Chen et al., 2014]. Finally, (I) exhibits zinc–nitrogen bond lengths of 2.1058 (11) Å for Zn1—N1 and 2.1358 (11) Å for Zn2—N2. A similar Schiff-base complex containing zinc and hydroxide ions exhibits an zinc–imine bond length of 2.022 (4) Å (Chen et al., 2014), thus the bonds in (I) are slightly elongated in comparison, especially the Zn2—N2 bond.

In general, the bond angles in (I) are as expected (Table 1), apart from the O—Zn—N angles: these are significantly compressed from the ideal tetrahedral values with O1—Zn1—N1 = 88.54 (4)° and O4—Zn2—N2 = 86.91 (4)°, presumably because of the rigid structure of the aminoalkoxide and the higher steric demand of the tetrahedral nitrogen atom. This is supported by a similar compound in the literature with an O—Zn—N angle of 94.1 (1)° (Chen et al., 2014). The N2—Zn2—O3 bond angle [112.11 (4)°] is slightly wider than the ideal tetrahedral angle, as is O2—Zn2—O4 [116.23 (4)°] but O2—Zn2—O3 is slightly compressed to 108.79 (4)°. The angle of the O2 hydroxyl oxygen atom, Zn1 and the O1 atom of the alkoxide is 111.19 (4)°, which is slightly expanded from the ideal tetrahedral angle. Finally, the N1—Zn1—Br1 bond angle is widened to 114.35 (3)°, which is similar to a compound in literature, where the corresponding angle is 113.1 (1)° (Chen et al., 2014).

The central structural features of (I) are two six-membered rings, which consist of zinc–oxygen bonds (Fig. 2). In the six-membered rings two zinc atoms are bridged by one oxygen atom of the alkoxide and the other zinc centres are bridged by a hydroxide ion. Then, both six-membered rings are connected by two oxygen atoms of the alkoxide species, so the two parts are interconnected to each other and a central eight-membered ring is formed by the connection of the two six-membered rings. The four nitrogen atoms of the piperidine rings coordinate to the zinc atoms of the six-membered ring. The coordination spheres of the other zinc atoms are completed by bromide ions. The chelating 2-methyl-1-(piperidine-1-yl)propan-2-olate anions lie at the edges of the complex, so they do not interact with the other anions.

One of the methyl groups of the acetone solvent molecule is disordered over two sets of sites with occupancies of 0.519 (6) and 0.481 (6). The disorder of just one methyl group of an acetone molecule has already been reported in the literature (Arias et al., 2013 ; Balogh-Hergovich et al., 1998 ).

3. Supramolecular features

In the extended structure of (I), the molecules are stacked along the a axis, as shown in Fig. 3. As noted already, an O—H⋯O hydrogen bond links the O2—H2 hydroxide ion with the acetone solvent molecule (Table 2). The graph-set motif of the O—H⋯O hydrogen bonding is described by a discrete finite pattern [D(2)] and, because of the inversion symmetry of the complex, a second [D₂²(11)] pattern appears.

Table 2
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O2—H2⋯O5	0.69 (2)	2.23 (2)	2.9036 (15)	166 (3)

Figure 3
View along the a-axis direction of the crystal packing of (I)

The Hirshfeld surface analysis of (I) (CrystalExplorer17; Turner et al., 2017 ) highlights the hydrogen bonding between the main molecule and the acetone solvent molecule. The main molecule is shown (Fig. 4) with d_norm in the range −0.5240 to +1.5598: the characteristic red spot adjacent to H2 indicates the hydrogen bond to O5. As a result of steric shielding, no intermolecular hydrogen bonding through the bridging O3 hydroxide group occurs.

Figure 4
Hirshfeld surface of (I)

: the O—H⋯O hydrogen bond between H2 and O5 is labelled.

4. Database survey

Other examples of crystallographically characterized zinc complexes containing coordinated bromide ions or aminoalkoxides include Zn₂Br₂OH₂(C₂₇H₃₃N₃O₂)·C₂H₃N [CSD (Groom et al., 2016 ]) refcode COCQOC; Chen et al., 2014] and ZnBr₂(C₂₅H₃₁Cl₂N₃O₂) (COCQAO; Chen et al., 2014), ZnOH(C₂₁H₃₇BN₉) (RUWSOT; Siek et al., 2016), ZnBr(C₁₆H₁₈N₄O)ZnH₂OBr₃·2H₂O (SEQROY; Purkait et al., 2018 ), ZnBr(C₂₁H₂₂N₆)·ZnOCH₄Br₃ (MATFEV; Herber et al., 2017 ), ZnBr(C₈H₂₀N₄O)·ClO₄ (BAMZAR; Reichenbach-Klinke et al., 2003 ), ZnI₂(C₁₄H₂₁BrN₂O)·CH₄O (DUHJIA; Zhu et al., 2009 ), ZnCl(C₁₆H₁₃BrN₃O·CH₄O (GAVSOM; Qiu & Tong, 2005 ), Zn(C₂H₅)(C₂₁H₂₉BrN₃O (FEKMIU; Stasiw et al., 2017 ), ZnBr(C₂₆H₁₉N₅O)·Br (LIMBAM; Bachmann et al., 2013 ), ZnBr(C₁₅H₁₈N₃O) (POGJAW; Ondráček et al.,1994 ), ZnBr₂(C₁₀H₂₄N₂) (DAGMUV01; Eckert et al., 2013 ), ZnBr₂(C₂₃H₃₄N₂Si) (DASCIL; Gessner & Strohmann, 2012 ), Zn₂Br₄(C₈H₁₉NOSi)₂ (VUPFES; Däschlein et al., 2009 ), Zn₂Br₂(C₁₁H₂₃NO)₂ (OMAHAM; Gessner et al., 2010 ), Zn₂Br₂(C₁₅H₂₂FeNOSi)₂·C₃H₆O (FAWPOL; Golz et al., 2017 ) and Zn₂Br₄(C₁₈H₂₃NOSi)₂ (VUPFAO; Däschlein & Strohmann, 2009 ).

5. Synthesis and crystallization

Zinc bromide (432 mg, 1.92 mmol, 3.00 eq.) was dissolved in 2.00 ml of acetone/water (v:v = 4:1). Then, 2-methyl-1-(piperidine-1-yl)propan-2-ol (200 mg, 1.28 mmol, 2.00 eq.) and triethylamine (0.10 ml, 0.64 mmol, 1.0 eq.) were added. The reaction solution turned dull and was stored at 278 K for seven days during which time (I) crystallized as colourless blocks.

6. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 3. The O-bound hydrogen atoms were located in difference-Fourier maps and refined independently. All C-bound hydrogen atoms were placed in geometrically calculated positions (C—H = 0.98–0.99 Å) and refined as riding atoms with the constraint U_iso(H) = 1.5U_eq(C-methyl) and 1.2U_eq(C) for other H atoms.

Table 3
Experimental details

Crystal data
Chemical formula	[Zn₆Br₄(C₉H₁₈NO)₄(OH)₄]·2C₃H₆O₂
M_r	1521.02
Crystal system, space group	Monoclinic, P2₁/n
Temperature (K)	100
a, b, c (Å)	12.1464 (7), 21.0777 (12), 12.5842 (7)
β (°)	115.277 (2)
V (Å³)	2913.3 (3)
Z	2
Radiation type	Mo Kα
μ (mm⁻¹)	5.22
Crystal size (mm)	0.22 × 0.17 × 0.13

Data collection
Diffractometer	Bruker D8 VENTURE area detector
Absorption correction	Multi-scan (SADABS; Bruker, 2016 )
T_min, T_max	0.638, 0.746
No. of measured, independent and observed [I > 2σ(I)] reflections	87000, 10668, 9283
R_int	0.044
(sin θ/λ)_max (Å⁻¹)	0.760

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.021, 0.051, 1.03
No. of reflections	10668
No. of parameters	323
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	1.00, −1.02
Computer programs: APEX2 and SAINT (Bruker, 2016), SHELXT2014/5 (Sheldrick, 2015a ), SHELXL2014/7 (Sheldrick, 2015b ), OLEX2 (Dolomanov et al., 2009 ), Mercury (Macrae et al., 2020 ) and publCIF (Westrip, 2010 ).

Supporting information

CCDC reference: 2005919

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2056989020007100/hb7910sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989020007100/hb7910Isup2.hkl

checkCIF report

Computing details top

Data collection: APEX2 (Bruker, 2016); cell refinement: SAINT (Bruker, 2016); data reduction: SAINT (Bruker, 2016); program(s) used to solve structure: SHELXT2014/5 (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2014/7 (Sheldrick, 2015b); molecular graphics: OLEX2 (Dolomanov et al., 2009), Mercury (Macrae et al., 2020); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009) and publCIF (Westrip, 2010).

Tetrabromidotetra-µ-hydroxido-hexakis[µ-2-methyl-3-(pyrrolidin-1-yl)propan-2-olato]hexazinc(II) acetone disolvate top

Crystal data top

[Zn₆Br₄(C₉H₁₈NO)₄(OH)₄]·2C₃H₆O₂	F(000) = 1536
M_r = 1521.02	D_x = 1.734 Mg m⁻³
Monoclinic, P2₁/n	Mo Kα radiation, λ = 0.71073 Å
a = 12.1464 (7) Å	Cell parameters from 9842 reflections
b = 21.0777 (12) Å	θ = 2.6–32.7°
c = 12.5842 (7) Å	µ = 5.22 mm⁻¹
β = 115.277 (2)°	T = 100 K
V = 2913.3 (3) Å³	Block, colourless
Z = 2	0.22 × 0.17 × 0.13 mm

Data collection top

Bruker D8 VENTURE area detector diffractometer	10668 independent reflections
Radiation source: microfocus sealed X-ray tube, Incoatec Iµs	9283 reflections with I > 2σ(I)
HELIOS mirror optics monochromator	R_int = 0.044
Detector resolution: 10.4167 pixels mm^-1	θ_max = 32.7°, θ_min = 2.6°
ω and φ scans	h = −18→18
Absorption correction: multi-scan (SADABS; Bruker, 2016)	k = −31→31
T_min = 0.638, T_max = 0.746	l = −19→19
87000 measured reflections

Refinement top

Refinement on F²	Primary atom site location: dual
Least-squares matrix: full	Hydrogen site location: mixed
R[F² > 2σ(F²)] = 0.021	H atoms treated by a mixture of independent and constrained refinement
wR(F²) = 0.051	w = 1/[σ²(F_o²) + (0.0215P)² + 1.5066P] where P = (F_o² + 2F_c²)/3
S = 1.03	(Δ/σ)_max = 0.003
10668 reflections	Δρ_max = 1.00 e Å⁻³
323 parameters	Δρ_min = −1.02 e Å⁻³
0 restraints

Special details top

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq	Occ. (<1)
Zn1	0.62156 (2)	0.63111 (2)	0.41114 (2)	0.01274 (3)
Zn2	0.45211 (2)	0.49658 (2)	0.32741 (2)	0.01142 (3)
Zn3	0.61346 (2)	0.38070 (2)	0.51363 (2)	0.01140 (3)
Br1	0.79563 (2)	0.61003 (2)	0.59007 (2)	0.02105 (3)
Br2	0.80568 (2)	0.34023 (2)	0.54000 (2)	0.02140 (3)
O1	0.48677 (8)	0.67133 (4)	0.43216 (9)	0.01519 (17)
O2	0.56873 (9)	0.55579 (5)	0.31759 (9)	0.01716 (18)
H2	0.616 (2)	0.5432 (11)	0.309 (2)	0.037 (6)*
O3	0.37153 (9)	0.53555 (5)	0.41228 (9)	0.01578 (17)
H3	0.3282 (18)	0.5134 (10)	0.4186 (17)	0.022 (5)*
O4	0.50357 (8)	0.40863 (4)	0.35585 (8)	0.01269 (16)
N1	0.63568 (10)	0.71351 (5)	0.32313 (10)	0.0155 (2)
N2	0.32698 (10)	0.46745 (5)	0.15543 (9)	0.01465 (19)
C1	0.45082 (12)	0.72981 (6)	0.36876 (13)	0.0174 (2)
C2	0.41477 (15)	0.77873 (7)	0.43809 (15)	0.0255 (3)
H2A	0.3434	0.7635	0.4478	0.038*
H2B	0.3952	0.8191	0.3954	0.038*
H2C	0.4826	0.7849	0.5156	0.038*
C3	0.34282 (13)	0.71765 (7)	0.25016 (14)	0.0236 (3)
H3A	0.3621	0.6823	0.2103	0.035*
H3B	0.3264	0.7559	0.2014	0.035*
H3C	0.2708	0.7070	0.2628	0.035*
C4	0.56436 (13)	0.75801 (6)	0.36102 (13)	0.0190 (2)
H4A	0.5381	0.7941	0.3054	0.023*
H4B	0.6189	0.7751	0.4392	0.023*
C5	0.58516 (13)	0.71191 (7)	0.19220 (13)	0.0220 (3)
H5A	0.5839	0.7555	0.1626	0.026*
H5B	0.5002	0.6963	0.1598	0.026*
C6	0.65865 (15)	0.66969 (8)	0.14903 (14)	0.0261 (3)
H6A	0.6231	0.6711	0.0621	0.031*
H6B	0.6548	0.6253	0.1731	0.031*
C7	0.79068 (15)	0.69111 (8)	0.19897 (16)	0.0293 (3)
H7A	0.7959	0.7333	0.1669	0.035*
H7B	0.8389	0.6607	0.1760	0.035*
C8	0.84214 (13)	0.69466 (8)	0.33251 (15)	0.0250 (3)
H8A	0.8459	0.6515	0.3648	0.030*
H8B	0.9260	0.7118	0.3645	0.030*
C9	0.76406 (12)	0.73670 (7)	0.37067 (14)	0.0207 (3)
H9A	0.7990	0.7376	0.4576	0.025*
H9B	0.7649	0.7805	0.3428	0.025*
C10	0.46559 (11)	0.37274 (6)	0.25037 (11)	0.0139 (2)
C11	0.45016 (13)	0.30319 (6)	0.27504 (13)	0.0202 (3)
H11A	0.5295	0.2853	0.3269	0.030*
H11B	0.4162	0.2795	0.2009	0.030*
H11C	0.3949	0.3001	0.3131	0.030*
C12	0.56244 (13)	0.37841 (7)	0.20344 (13)	0.0208 (3)
H12A	0.5782	0.4233	0.1952	0.031*
H12B	0.5334	0.3576	0.1267	0.031*
H12C	0.6378	0.3580	0.2584	0.031*
C13	0.33860 (12)	0.39724 (6)	0.16641 (11)	0.0162 (2)
H13A	0.3171	0.3791	0.0874	0.019*
H13B	0.2786	0.3812	0.1939	0.019*
C14	0.19942 (12)	0.48510 (7)	0.13000 (13)	0.0202 (3)
H14A	0.1802	0.4696	0.1944	0.024*
H14B	0.1431	0.4641	0.0565	0.024*
C15	0.17948 (14)	0.55629 (8)	0.11732 (14)	0.0251 (3)
H15A	0.2309	0.5772	0.1928	0.030*
H15B	0.0933	0.5659	0.0984	0.030*
C16	0.21093 (16)	0.58260 (9)	0.02080 (15)	0.0313 (3)
H16A	0.1520	0.5665	−0.0566	0.038*
H16B	0.2056	0.6295	0.0197	0.038*
C17	0.33921 (16)	0.56243 (8)	0.04279 (14)	0.0286 (3)
H17A	0.3560	0.5760	−0.0242	0.034*
H17B	0.3987	0.5837	0.1144	0.034*
C18	0.35499 (15)	0.49096 (8)	0.05796 (13)	0.0237 (3)
H18A	0.3004	0.4698	−0.0162	0.028*
H18B	0.4399	0.4796	0.0745	0.028*
O5	0.76193 (12)	0.52276 (7)	0.24976 (13)	0.0363 (3)
C19	0.86250 (16)	0.50349 (10)	0.29097 (18)	0.0379 (4)
C20	0.9050 (6)	0.4770 (4)	0.4156 (5)	0.082 (3)	0.519 (6)
H20A	0.9538	0.5090	0.4727	0.122*	0.519 (6)
H20B	0.9546	0.4389	0.4241	0.122*	0.519 (6)
H20C	0.8340	0.4660	0.4297	0.122*	0.519 (6)
C20A	0.8773 (4)	0.4280 (2)	0.3187 (5)	0.0537 (18)	0.481 (6)
H20D	0.8394	0.4171	0.3712	0.081*	0.481 (6)
H20E	0.9640	0.4170	0.3566	0.081*	0.481 (6)
H20F	0.8375	0.4042	0.2451	0.081*	0.481 (6)
C21	0.96197 (15)	0.52689 (8)	0.26145 (16)	0.0292 (3)
H21A	0.9265	0.5461	0.1830	0.044*
H21B	1.0143	0.4913	0.2625	0.044*
H21C	1.0104	0.5586	0.3195	0.044*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Zn1	0.01269 (6)	0.00878 (6)	0.01867 (7)	−0.00006 (5)	0.00852 (6)	0.00090 (5)
Zn2	0.01198 (6)	0.00917 (6)	0.01388 (6)	−0.00076 (5)	0.00627 (5)	−0.00150 (5)
Zn3	0.01127 (6)	0.01025 (6)	0.01389 (6)	0.00137 (5)	0.00653 (5)	0.00032 (5)
Br1	0.01778 (6)	0.02193 (7)	0.02107 (7)	0.00233 (5)	0.00602 (5)	0.00430 (5)
Br2	0.01385 (6)	0.02248 (7)	0.03002 (7)	0.00588 (5)	0.01142 (5)	0.00404 (5)
O1	0.0159 (4)	0.0097 (4)	0.0236 (5)	0.0029 (3)	0.0119 (4)	0.0046 (3)
O2	0.0166 (4)	0.0126 (4)	0.0272 (5)	−0.0020 (3)	0.0140 (4)	−0.0030 (4)
O3	0.0182 (4)	0.0130 (4)	0.0204 (5)	−0.0034 (3)	0.0122 (4)	−0.0041 (3)
O4	0.0150 (4)	0.0107 (4)	0.0117 (4)	−0.0001 (3)	0.0050 (3)	−0.0031 (3)
N1	0.0167 (5)	0.0123 (5)	0.0203 (5)	−0.0016 (4)	0.0105 (4)	0.0011 (4)
N2	0.0145 (5)	0.0171 (5)	0.0122 (4)	−0.0003 (4)	0.0056 (4)	0.0006 (4)
C1	0.0197 (6)	0.0105 (5)	0.0262 (7)	0.0036 (4)	0.0137 (5)	0.0054 (5)
C2	0.0320 (8)	0.0126 (6)	0.0411 (9)	0.0065 (5)	0.0244 (7)	0.0036 (6)
C3	0.0189 (6)	0.0239 (7)	0.0286 (7)	0.0046 (5)	0.0106 (6)	0.0094 (6)
C4	0.0231 (6)	0.0094 (5)	0.0288 (7)	0.0001 (5)	0.0154 (6)	0.0020 (5)
C5	0.0225 (6)	0.0232 (7)	0.0217 (6)	0.0010 (5)	0.0108 (5)	0.0055 (5)
C6	0.0314 (8)	0.0281 (7)	0.0243 (7)	0.0003 (6)	0.0171 (6)	0.0008 (6)
C7	0.0311 (8)	0.0314 (8)	0.0367 (9)	0.0013 (6)	0.0252 (7)	0.0057 (7)
C8	0.0192 (6)	0.0257 (7)	0.0347 (8)	−0.0005 (5)	0.0160 (6)	0.0048 (6)
C9	0.0185 (6)	0.0173 (6)	0.0287 (7)	−0.0058 (5)	0.0122 (6)	0.0005 (5)
C10	0.0155 (5)	0.0123 (5)	0.0149 (5)	−0.0023 (4)	0.0075 (5)	−0.0055 (4)
C11	0.0227 (6)	0.0120 (5)	0.0261 (7)	−0.0023 (5)	0.0106 (6)	−0.0059 (5)
C12	0.0209 (6)	0.0251 (7)	0.0212 (6)	−0.0004 (5)	0.0135 (5)	−0.0043 (5)
C13	0.0163 (5)	0.0161 (6)	0.0147 (5)	−0.0034 (4)	0.0052 (5)	−0.0048 (4)
C14	0.0137 (5)	0.0239 (7)	0.0194 (6)	0.0007 (5)	0.0036 (5)	0.0019 (5)
C15	0.0217 (6)	0.0246 (7)	0.0259 (7)	0.0072 (6)	0.0071 (6)	0.0063 (6)
C16	0.0347 (8)	0.0290 (8)	0.0239 (7)	0.0058 (7)	0.0066 (7)	0.0116 (6)
C17	0.0346 (8)	0.0301 (8)	0.0234 (7)	0.0021 (7)	0.0146 (7)	0.0112 (6)
C18	0.0291 (7)	0.0294 (7)	0.0159 (6)	0.0018 (6)	0.0127 (6)	0.0040 (5)
O5	0.0309 (6)	0.0365 (7)	0.0516 (8)	0.0045 (5)	0.0273 (6)	0.0029 (6)
C19	0.0260 (8)	0.0477 (11)	0.0405 (10)	0.0031 (7)	0.0146 (7)	0.0224 (8)
C20	0.074 (4)	0.127 (6)	0.061 (3)	0.050 (4)	0.045 (3)	0.063 (4)
C20A	0.0223 (17)	0.052 (3)	0.084 (4)	0.0048 (17)	0.020 (2)	0.041 (3)
C21	0.0239 (7)	0.0305 (8)	0.0350 (8)	−0.0013 (6)	0.0143 (7)	0.0054 (7)

Geometric parameters (Å, º) top

Zn1—O1	1.9593 (9)	C8—H8A	0.9900
Zn1—O2	1.9165 (10)	C8—H8B	0.9900
Zn1—N1	2.1058 (11)	C8—C9	1.518 (2)
Zn1—Br1	2.3816 (2)	C9—H9A	0.9900
Zn2—O2	1.9310 (10)	C9—H9B	0.9900
Zn2—O3	1.9147 (9)	C10—C11	1.5265 (19)
Zn2—O4	1.9401 (9)	C10—C12	1.5297 (18)
Zn2—N2	2.1358 (11)	C10—C13	1.5396 (18)
Zn3—O1ⁱ	1.9646 (9)	C11—H11A	0.9800
Zn3—O3ⁱ	1.9681 (9)	C11—H11B	0.9800
Zn3—O4	1.9512 (9)	C11—H11C	0.9800
Zn3—Br2	2.3722 (2)	C12—H12A	0.9800
O1—Zn3ⁱ	1.9646 (9)	C12—H12B	0.9800
O1—C1	1.4314 (15)	C12—H12C	0.9800
O2—H2	0.69 (2)	C13—H13A	0.9900
O3—Zn3ⁱ	1.9682 (9)	C13—H13B	0.9900
O3—H3	0.73 (2)	C14—H14A	0.9900
O4—C10	1.4227 (15)	C14—H14B	0.9900
N1—C4	1.4867 (17)	C14—C15	1.517 (2)
N1—C5	1.4930 (19)	C15—H15A	0.9900
N1—C9	1.4940 (17)	C15—H15B	0.9900
N2—C13	1.4876 (17)	C15—C16	1.525 (2)
N2—C14	1.4892 (17)	C16—H16A	0.9900
N2—C18	1.4907 (17)	C16—H16B	0.9900
C1—C2	1.531 (2)	C16—C17	1.522 (2)
C1—C3	1.530 (2)	C17—H17A	0.9900
C1—C4	1.5425 (19)	C17—H17B	0.9900
C2—H2A	0.9800	C17—C18	1.520 (2)
C2—H2B	0.9800	C18—H18A	0.9900
C2—H2C	0.9800	C18—H18B	0.9900
C3—H3A	0.9800	O5—C19	1.177 (2)
C3—H3B	0.9800	C19—C20	1.532 (5)
C3—H3C	0.9800	C19—C20A	1.623 (5)
C4—H4A	0.9900	C19—C21	1.491 (2)
C4—H4B	0.9900	C20—H20A	0.9800
C5—H5A	0.9900	C20—H20B	0.9800
C5—H5B	0.9900	C20—H20C	0.9800
C5—C6	1.516 (2)	C20A—H20D	0.9800
C6—H6A	0.9900	C20A—H20E	0.9800
C6—H6B	0.9900	C20A—H20F	0.9800
C6—C7	1.520 (2)	C21—H21A	0.9800
C7—H7A	0.9900	C21—H21B	0.9800
C7—H7B	0.9900	C21—H21C	0.9800
C7—C8	1.524 (2)

O1—Zn1—Br1	114.12 (3)	C9—C8—C7	111.10 (13)
O1—Zn1—N1	88.54 (4)	C9—C8—H8A	109.4
O2—Zn1—Br1	110.82 (3)	C9—C8—H8B	109.4
O2—Zn1—O1	111.19 (4)	N1—C9—C8	111.64 (12)
O2—Zn1—N1	116.18 (4)	N1—C9—H9A	109.3
N1—Zn1—Br1	114.35 (3)	N1—C9—H9B	109.3
O2—Zn2—O4	116.23 (4)	C8—C9—H9A	109.3
O2—Zn2—N2	110.18 (4)	C8—C9—H9B	109.3
O3—Zn2—O2	108.79 (4)	H9A—C9—H9B	108.0
O3—Zn2—O4	120.54 (4)	O4—C10—C11	109.87 (11)
O3—Zn2—N2	112.11 (4)	O4—C10—C12	108.80 (10)
O4—Zn2—N2	86.91 (4)	O4—C10—C13	107.02 (10)
O1ⁱ—Zn3—Br2	118.00 (3)	C11—C10—C12	109.57 (11)
O1ⁱ—Zn3—O3ⁱ	106.38 (4)	C11—C10—C13	106.71 (10)
O3ⁱ—Zn3—Br2	111.70 (3)	C12—C10—C13	114.78 (11)
O4—Zn3—Br2	117.11 (3)	C10—C11—H11A	109.5
O4—Zn3—O1ⁱ	105.41 (4)	C10—C11—H11B	109.5
O4—Zn3—O3ⁱ	95.52 (4)	C10—C11—H11C	109.5
Zn1—O1—Zn3ⁱ	118.87 (5)	H11A—C11—H11B	109.5
Zn1—O2—Zn2	123.95 (5)	H11A—C11—H11C	109.5
Zn2—O3—Zn3ⁱ	133.08 (5)	H11B—C11—H11C	109.5
Zn2—O4—Zn3	120.17 (4)	C10—C12—H12A	109.5
C1—O1—Zn1	111.77 (7)	C10—C12—H12B	109.5
C1—O1—Zn3ⁱ	125.97 (8)	C10—C12—H12C	109.5
Zn1—O2—H2	109 (2)	H12A—C12—H12B	109.5
Zn2—O2—H2	117 (2)	H12A—C12—H12C	109.5
Zn2—O3—H3	110.4 (15)	H12B—C12—H12C	109.5
Zn3ⁱ—O3—H3	116.5 (15)	N2—C13—C10	115.14 (10)
C10—O4—Zn2	112.67 (7)	N2—C13—H13A	108.5
C10—O4—Zn3	126.68 (8)	N2—C13—H13B	108.5
C4—N1—Zn1	99.33 (7)	C10—C13—H13A	108.5
C4—N1—C5	110.31 (11)	C10—C13—H13B	108.5
C4—N1—C9	108.46 (11)	H13A—C13—H13B	107.5
C5—N1—Zn1	118.32 (9)	N2—C14—H14A	109.2
C5—N1—C9	108.44 (11)	N2—C14—H14B	109.2
C9—N1—Zn1	111.39 (8)	N2—C14—C15	111.98 (12)
C13—N2—Zn2	101.16 (8)	H14A—C14—H14B	107.9
C13—N2—C14	108.49 (10)	C15—C14—H14A	109.2
C13—N2—C18	111.17 (11)	C15—C14—H14B	109.2
C14—N2—Zn2	111.77 (8)	C14—C15—H15A	109.4
C14—N2—C18	108.80 (11)	C14—C15—H15B	109.4
C18—N2—Zn2	115.13 (9)	C14—C15—C16	111.13 (13)
O1—C1—C2	110.84 (11)	H15A—C15—H15B	108.0
O1—C1—C3	109.26 (11)	C16—C15—H15A	109.4
O1—C1—C4	107.39 (10)	C16—C15—H15B	109.4
C2—C1—C4	104.92 (11)	C15—C16—H16A	109.7
C3—C1—C2	109.51 (12)	C15—C16—H16B	109.7
C3—C1—C4	114.85 (12)	H16A—C16—H16B	108.2
C1—C2—H2A	109.5	C17—C16—C15	109.80 (13)
C1—C2—H2B	109.5	C17—C16—H16A	109.7
C1—C2—H2C	109.5	C17—C16—H16B	109.7
H2A—C2—H2B	109.5	C16—C17—H17A	109.4
H2A—C2—H2C	109.5	C16—C17—H17B	109.4
H2B—C2—H2C	109.5	H17A—C17—H17B	108.0
C1—C3—H3A	109.5	C18—C17—C16	111.34 (14)
C1—C3—H3B	109.5	C18—C17—H17A	109.4
C1—C3—H3C	109.5	C18—C17—H17B	109.4
H3A—C3—H3B	109.5	N2—C18—C17	111.83 (12)
H3A—C3—H3C	109.5	N2—C18—H18A	109.3
H3B—C3—H3C	109.5	N2—C18—H18B	109.3
N1—C4—C1	115.86 (11)	C17—C18—H18A	109.3
N1—C4—H4A	108.3	C17—C18—H18B	109.3
N1—C4—H4B	108.3	H18A—C18—H18B	107.9
C1—C4—H4A	108.3	O5—C19—C20	114.2 (2)
C1—C4—H4B	108.3	O5—C19—C20A	115.6 (2)
H4A—C4—H4B	107.4	O5—C19—C21	125.10 (17)
N1—C5—H5A	109.1	C21—C19—C20	114.9 (3)
N1—C5—H5B	109.1	C21—C19—C20A	110.5 (2)
N1—C5—C6	112.41 (12)	C19—C20—H20A	109.5
H5A—C5—H5B	107.9	C19—C20—H20B	109.5
C6—C5—H5A	109.1	C19—C20—H20C	109.5
C6—C5—H5B	109.1	H20A—C20—H20B	109.5
C5—C6—H6A	109.5	H20A—C20—H20C	109.5
C5—C6—H6B	109.5	H20B—C20—H20C	109.5
C5—C6—C7	110.88 (14)	C19—C20A—H20D	109.5
H6A—C6—H6B	108.1	C19—C20A—H20E	109.5
C7—C6—H6A	109.5	C19—C20A—H20F	109.5
C7—C6—H6B	109.5	H20D—C20A—H20E	109.5
C6—C7—H7A	109.8	H20D—C20A—H20F	109.5
C6—C7—H7B	109.8	H20E—C20A—H20F	109.5
C6—C7—C8	109.51 (12)	C19—C21—H21A	109.5
H7A—C7—H7B	108.2	C19—C21—H21B	109.5
C8—C7—H7A	109.8	C19—C21—H21C	109.5
C8—C7—H7B	109.8	H21A—C21—H21B	109.5
C7—C8—H8A	109.4	H21A—C21—H21C	109.5
C7—C8—H8B	109.4	H21B—C21—H21C	109.5
H8A—C8—H8B	108.0

Zn1—O1—C1—C2	−143.25 (10)	C2—C1—C4—N1	165.89 (12)
Zn1—O1—C1—C3	95.97 (10)	C3—C1—C4—N1	−73.82 (15)
Zn1—O1—C1—C4	−29.18 (13)	C4—N1—C5—C6	177.10 (12)
Zn1—N1—C4—C1	−38.23 (13)	C4—N1—C9—C8	−178.28 (12)
Zn1—N1—C5—C6	−69.58 (14)	C5—N1—C4—C1	86.76 (14)
Zn1—N1—C9—C8	73.40 (13)	C5—N1—C9—C8	−58.48 (15)
Zn2—O4—C10—C11	−152.00 (8)	C5—C6—C7—C8	54.13 (18)
Zn2—O4—C10—C12	88.05 (11)	C6—C7—C8—C9	−54.74 (17)
Zn2—O4—C10—C13	−36.51 (11)	C7—C8—C9—N1	58.21 (16)
Zn2—N2—C13—C10	−32.11 (11)	C9—N1—C4—C1	−154.62 (12)
Zn2—N2—C14—C15	69.34 (13)	C9—N1—C5—C6	58.46 (15)
Zn2—N2—C18—C17	−67.74 (14)	C11—C10—C13—N2	164.92 (11)
Zn3ⁱ—O1—C1—C2	57.94 (15)	C12—C10—C13—N2	−73.49 (14)
Zn3ⁱ—O1—C1—C3	−62.83 (13)	C13—N2—C14—C15	−179.96 (11)
Zn3ⁱ—O1—C1—C4	172.01 (8)	C13—N2—C18—C17	178.00 (12)
Zn3—O4—C10—C11	36.06 (13)	C14—N2—C13—C10	−149.80 (11)
Zn3—O4—C10—C12	−83.89 (12)	C14—N2—C18—C17	58.59 (16)
Zn3—O4—C10—C13	151.55 (8)	C14—C15—C16—C17	−53.46 (18)
O1—C1—C4—N1	47.91 (16)	C15—C16—C17—C18	53.38 (19)
O4—C10—C13—N2	47.33 (14)	C16—C17—C18—N2	−57.19 (17)
N1—C5—C6—C7	−57.60 (16)	C18—N2—C13—C10	90.61 (13)
N2—C14—C15—C16	57.53 (16)	C18—N2—C14—C15	−58.90 (15)

Symmetry code: (i) −x+1, −y+1, −z+1.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O2—H2···O5	0.69 (2)	2.23 (2)	2.9036 (15)	166 (3)

Acknowledgements

We thank the Deutsche Forschungsgemeinschaft (DFG) for financial support and LB thanks the Fonds der Chemischen Industrie (FCI) for a doctoral fellowship.

Funding information

Funding for this research was provided by: Deutsche Forschungsgemeinschaft ; Verband der Chemischen Industrie .

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