Bis[5-(4-bromo­phen­yl)-4-(tert-but­oxy­carbon­yl)pyrrolidine-2-carboxyl­ato]copper(II) dihydrate

Kudryavtsev, K.V.; Churakov, A.V.; Dogan, O.

doi:10.1107/S1600536811043893

metal-organic compounds

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Volume 67| Part 11| November 2011| Page m1623

doi:10.1107/S1600536811043893

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Bis[5-(4-bromophenyl)-4-(tert-butoxycarbonyl)pyrrolidine-2-carboxylato]copper(II) dihydrate

Konstantin V. Kudryavtsev,^a ^* Andrei V. Churakov ^b and Ozdemir Dogan ^c

^aDepartment of Chemistry, M.V. Lomonosov Moscow State University, Leninskie Gory 1/3, Moscow 119991, Russian Federation, ^bInstitute of General and Inorganic Chemistry, Russian Academy of Sciences, Leninskii prosp. 31, Moscow 119991, Russian Federation, and ^cDepartment of Chemistry, Middle East Technical University, Ankara 06531, Turkey
^*Correspondence e-mail: kudr@org.chem.msu.ru

(Received 15 October 2011; accepted 22 October 2011; online 29 October 2011)

In the title compound, [Cu(C₁₆H₁₉BrNO₄)₂]·2H₂O, the Cu^II ion resides on an inversion centre and is coordinated by two O and two N atoms from two enantiomeric 5-(4-bromophenyl)-4-(tert-butoxycarbonyl)pyrrolidine-2-carboxylate ligands in a distorted square-planar geometry. The relative stereochemistry of the three stereogenic C atoms in each ligand has been determined. In the crystal, intermolecular N—H⋯O and O—H⋯O hydrogen bonds link the molecules into layers parallel to the bc plane. The crystal studied was twinned by pseudomerohedry with twin fractions of 0.719 (3) and 0.281 (3).

Related literature

For details of the ligand synthesis, see: Kudryavtsev et al. (2006 , 2010 ).

Experimental

Crystal data

[Cu(C₁₆H₁₉BrNO₄)₂]·2H₂O
M_r = 838.04
Monoclinic, P 2₁ /c
a = 15.251 (6) Å
b = 10.555 (4) Å
c = 10.541 (4) Å
β = 90.423 (6)°
V = 1696.9 (11) Å³
Z = 2
Mo Kα radiation
μ = 3.06 mm⁻¹
T = 150 K
0.32 × 0.20 × 0.05 mm

Data collection

Bruker SMART APEXII diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2008 ) T_min = 0.441, T_max = 0.862
12662 measured reflections
3268 independent reflections
2968 reflections with I > 2σ(I)
R_int = 0.053

Refinement

R[F² > 2σ(F²)] = 0.066
wR(F²) = 0.161
S = 1.09
3268 reflections
218 parameters
H-atom parameters constrained
Δρ_max = 0.75 e Å⁻³
Δρ_min = −1.12 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O5—H51⋯O2	0.82	2.15	2.968 (13)	180
O5—H52⋯O2ⁱ	0.82	2.18	3.001 (14)	180
N1—H⋯O2ⁱⁱ	0.93	1.99	2.916 (9)	173
Symmetry codes: (i) -x, -y+1, -z+2; (ii) $[-x, y-{\script{1\over 2}}, -z+{\script{3\over 2}}]$ .

Data collection: APEX2 (Bruker, 2008); cell refinement: SAINT (Bruker, 2008); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536811043893/cv5181sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536811043893/cv5181Isup2.hkl

checkCIF report

Comment top

To the best of our knowledge this is the first X-ray structural analysis of metal complex with 5-arylpyrrolidine-2,4-dicarboxylic acid derivative. In the title compound, an α-amino acid ligand contains additional structural elements - aryl substituent and second carboxylic function, that allows subsequent tuning of complex physico-chemical properties including supramolecular assemblies formation. In the centrosymmetric title complex central copper atom has square-planar coordination environment. There are no additional axial ligands, since both axial positions are shielded by lateral phenyl substituents (Fig. 1). The crystal lattice contains one crystallographycally independent solvent water molecule. Layers parallel to bc-plane are formed by N—H···O=C and H₂O···O=C hydrogen bonds (Table 1, Fig. 2). These layers are linked by weak van-der-Waals interactions between neighbouring t-Bu groups (Fig. 3).

Related literature top

For details of the ligand synthesis, see: Kudryavtsev et al. (2006, 2010).

Experimental top

(2S*,4S*,5R*)-5-(4-Bromophenyl)- 4-(tert-butoxycarbonyl)pyrrolidine-2-carboxylic acid (0.200 g, 0.54 mmol) was suspended in 6 ml of methanol. Anhydrous copper(II) chloride (0.036 g, 0.27 mmol) was added to the suspension in one portion under stirring. The deep blue solution formed immediately. After 1 h the solution was diluted with methanol to 9 mM concentration and subjected to slow evaporation at ambient temperature yielding deep blue crystals of the title complex compound.

Computing details top

Data collection: APEX2 (Bruker, 2008); cell refinement: SAINT (Bruker, 2008); data reduction: SAINT (Bruker, 2008); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures top

	Fig. 1. The molecular structure of the title compound, showing the numbering scheme adopted [symmetry code: (A) -x, -y, 2 - z]. Displacement ellipsoids are shown at the 50% probability level. Hydrogen atoms (except amino) are omitted for clarity.
	Fig. 2. Layers parallel to bc plane. Lateral bromophenyl (–C₆H₄Br) groups, butoxycarbonyl (–CO₂^tBu) substituents and hydrogen atoms (except amino and water) are omitted for clarity. Hydrogen bonds are shown as dashed lines.
	Fig. 3. A portion of the crystal packing viewed along axis a. Two parallel laeyers are shown. Hydrogen atoms (except amino and water) are omitted for clarity. Hydrogen bonds are drawn as dashed lines.

Bis[5-(4-bromophenyl)-4-(tert-butoxycarbonyl)pyrrolidine-2- carboxylato]copper(II) dihydrate top

Crystal data top

[Cu(C₁₆H₁₉BrNO₄)₂]·2H₂O	F(000) = 854
M_r = 838.04	D_x = 1.640 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 4476 reflections
a = 15.251 (6) Å	θ = 2.4–25.6°
b = 10.555 (4) Å	µ = 3.06 mm⁻¹
c = 10.541 (4) Å	T = 150 K
β = 90.423 (6)°	Prism, light-blue
V = 1696.9 (11) Å³	0.32 × 0.20 × 0.05 mm
Z = 2

Data collection top

Bruker SMART APEXII diffractometer	3268 independent reflections
Radiation source: fine-focus sealed tube	2968 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.053
Ω scans	θ_max = 26.0°, θ_min = 1.9°
Absorption correction: multi-scan (SADABS; Bruker, 2008)	h = −18→18
T_min = 0.441, T_max = 0.862	k = −13→13
12662 measured reflections	l = −13→13

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.066	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.161	H-atom parameters constrained
S = 1.09	w = 1/[σ²(F_o²) + (0.0259P)² + 19.8322P] where P = (F_o² + 2F_c²)/3
3268 reflections	(Δ/σ)_max < 0.001
218 parameters	Δρ_max = 0.75 e Å⁻³
0 restraints	Δρ_min = −1.12 e Å⁻³

Crystal data top

[Cu(C₁₆H₁₉BrNO₄)₂]·2H₂O	V = 1696.9 (11) Å³
M_r = 838.04	Z = 2
Monoclinic, P2₁/c	Mo Kα radiation
a = 15.251 (6) Å	µ = 3.06 mm⁻¹
b = 10.555 (4) Å	T = 150 K
c = 10.541 (4) Å	0.32 × 0.20 × 0.05 mm
β = 90.423 (6)°

Data collection top

Bruker SMART APEXII diffractometer	3268 independent reflections
Absorption correction: multi-scan (SADABS; Bruker, 2008)	2968 reflections with I > 2σ(I)
T_min = 0.441, T_max = 0.862	R_int = 0.053
12662 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.066	0 restraints
wR(F²) = 0.161	H-atom parameters constrained
S = 1.09	w = 1/[σ²(F_o²) + (0.0259P)² + 19.8322P] where P = (F_o² + 2F_c²)/3
3268 reflections	Δρ_max = 0.75 e Å⁻³
218 parameters	Δρ_min = −1.12 e Å⁻³

Special details top

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 (Å²) top

	x	y	z	U_iso*/U_eq
Cu1	0.0000	0.0000	1.0000	0.0234 (3)
Br1	0.28687 (6)	0.06433 (8)	1.37487 (10)	0.0343 (2)
N1	0.0529 (4)	−0.0100 (6)	0.8311 (7)	0.0205 (14)
H	0.0192	−0.0631	0.7799	0.025*
O1	0.0194 (3)	0.1801 (4)	0.9867 (6)	0.0231 (13)
O2	0.0442 (4)	0.3320 (6)	0.8483 (6)	0.0328 (15)
O3	0.3162 (4)	−0.1083 (5)	0.7398 (6)	0.0257 (13)
O4	0.3285 (4)	0.1004 (5)	0.6961 (7)	0.0321 (15)
C1	0.1464 (5)	−0.0587 (7)	0.8354 (8)	0.0200 (17)
H1	0.1455	−0.1526	0.8228	0.024*
C2	0.1854 (5)	0.0039 (8)	0.7160 (8)	0.0234 (18)
H2	0.1662	−0.0473	0.6409	0.028*
C3	0.1413 (6)	0.1349 (8)	0.7051 (8)	0.0254 (18)
H3A	0.1779	0.2011	0.7458	0.030*
H3B	0.1312	0.1580	0.6152	0.030*
C4	0.0542 (5)	0.1190 (8)	0.7750 (8)	0.0235 (17)
H4	0.0053	0.1253	0.7115	0.028*
C5	0.0399 (5)	0.2194 (7)	0.8769 (9)	0.0234 (17)
C6	0.2852 (6)	0.0073 (7)	0.7164 (7)	0.0223 (17)
C7	0.4129 (5)	−0.1301 (8)	0.7503 (9)	0.0271 (18)
C8	0.4490 (7)	−0.0602 (10)	0.8626 (11)	0.044 (3)
H8A	0.4167	−0.0847	0.9388	0.066*
H8B	0.4429	0.0312	0.8488	0.066*
H8C	0.5112	−0.0813	0.8738	0.066*
C9	0.4171 (6)	−0.2711 (9)	0.7707 (12)	0.046 (3)
H9A	0.3857	−0.2931	0.8484	0.069*
H9B	0.4785	−0.2975	0.7786	0.069*
H9C	0.3898	−0.3144	0.6983	0.069*
C10	0.4562 (6)	−0.0945 (10)	0.6271 (11)	0.041 (2)
H10A	0.4563	−0.0021	0.6181	0.061*
H10B	0.4237	−0.1323	0.5561	0.061*
H10C	0.5167	−0.1258	0.6271	0.061*
C11	0.1897 (5)	−0.0298 (7)	0.9624 (8)	0.0210 (17)
C12	0.2329 (5)	0.0837 (7)	0.9889 (9)	0.0243 (18)
H12	0.2405	0.1448	0.9237	0.029*
C13	0.2650 (5)	0.1081 (7)	1.1107 (9)	0.0257 (18)
H13	0.2972	0.1835	1.1268	0.031*
C14	0.2507 (6)	0.0250 (8)	1.2065 (9)	0.030 (2)
C15	0.2117 (6)	−0.0916 (8)	1.1805 (10)	0.034 (2)
H15	0.2060	−0.1530	1.2458	0.041*
C16	0.1813 (5)	−0.1178 (8)	1.0598 (9)	0.0252 (18)
H16	0.1543	−0.1972	1.0429	0.030*
O5	0.0873 (9)	0.5829 (11)	0.9593 (12)	0.107 (4)
H51	0.0755	0.5136	0.9285	0.128*
H52	0.0516	0.6063	1.0121	0.128*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Cu1	0.0179 (6)	0.0235 (7)	0.0287 (8)	−0.0049 (6)	0.0057 (7)	−0.0036 (6)
Br1	0.0351 (4)	0.0340 (4)	0.0335 (5)	0.0043 (4)	−0.0055 (5)	0.0007 (4)
N1	0.017 (3)	0.023 (3)	0.022 (3)	−0.001 (3)	0.001 (3)	−0.007 (3)
O1	0.020 (3)	0.008 (2)	0.041 (4)	−0.007 (2)	0.009 (3)	−0.002 (2)
O2	0.046 (4)	0.025 (3)	0.027 (4)	0.013 (3)	0.001 (3)	0.001 (3)
O3	0.026 (3)	0.011 (2)	0.040 (4)	0.002 (2)	0.009 (3)	0.004 (3)
O4	0.027 (3)	0.017 (3)	0.052 (4)	0.000 (3)	0.008 (3)	0.007 (3)
C1	0.020 (4)	0.006 (3)	0.033 (5)	0.001 (3)	0.010 (3)	0.001 (3)
C2	0.023 (4)	0.023 (4)	0.024 (4)	−0.001 (3)	0.008 (3)	−0.003 (3)
C3	0.030 (4)	0.019 (4)	0.028 (5)	0.002 (3)	0.006 (4)	−0.001 (3)
C4	0.017 (4)	0.022 (4)	0.032 (5)	0.001 (3)	0.002 (3)	−0.004 (3)
C5	0.015 (3)	0.020 (4)	0.036 (5)	0.005 (3)	−0.005 (4)	0.011 (4)
C6	0.033 (4)	0.014 (4)	0.020 (4)	0.003 (4)	0.005 (4)	−0.003 (3)
C7	0.024 (4)	0.019 (4)	0.039 (5)	0.001 (3)	0.004 (4)	0.006 (4)
C8	0.041 (5)	0.050 (6)	0.041 (6)	0.006 (5)	−0.011 (5)	−0.008 (5)
C9	0.032 (5)	0.028 (5)	0.077 (8)	0.015 (4)	−0.011 (5)	0.000 (5)
C10	0.029 (5)	0.049 (6)	0.045 (6)	0.004 (4)	0.008 (5)	−0.002 (5)
C11	0.017 (4)	0.015 (4)	0.031 (5)	0.003 (3)	0.005 (3)	0.002 (3)
C12	0.034 (5)	0.011 (3)	0.028 (4)	−0.003 (3)	0.006 (4)	0.001 (3)
C13	0.029 (4)	0.020 (4)	0.028 (5)	−0.003 (3)	0.007 (4)	−0.008 (4)
C14	0.022 (4)	0.026 (4)	0.042 (6)	0.010 (4)	−0.002 (4)	−0.005 (4)
C15	0.027 (4)	0.025 (4)	0.050 (6)	−0.002 (4)	−0.007 (5)	0.012 (4)
C16	0.019 (4)	0.014 (4)	0.042 (5)	−0.006 (3)	−0.004 (4)	0.010 (4)
O5	0.119 (10)	0.092 (8)	0.110 (10)	0.037 (8)	−0.011 (8)	−0.029 (7)

Geometric parameters (Å, º) top

Cu1—O1	1.929 (5)	C7—C8	1.497 (14)
Cu1—O1ⁱ	1.929 (5)	C7—C9	1.504 (12)
Cu1—N1	1.963 (7)	C7—C10	1.509 (14)
Cu1—N1ⁱ	1.963 (7)	C8—H8A	0.9800
Br1—C14	1.901 (10)	C8—H8B	0.9800
N1—C4	1.485 (11)	C8—H8C	0.9800
N1—C1	1.516 (10)	C9—H9A	0.9800
N1—H	0.9300	C9—H9B	0.9800
O1—C5	1.271 (11)	C9—H9C	0.9800
O2—C5	1.228 (10)	C10—H10A	0.9800
O3—C6	1.331 (9)	C10—H10B	0.9800
O3—C7	1.495 (10)	C10—H10C	0.9800
O4—C6	1.203 (10)	C11—C16	1.392 (12)
C1—C11	1.519 (12)	C11—C12	1.394 (11)
C1—C2	1.544 (11)	C12—C13	1.395 (13)
C1—H1	1.0000	C12—H12	0.9500
C2—C6	1.523 (12)	C13—C14	1.356 (13)
C2—C3	1.541 (11)	C13—H13	0.9500
C2—H2	1.0000	C14—C15	1.394 (12)
C3—C4	1.534 (11)	C15—C16	1.378 (13)
C3—H3A	0.9900	C15—H15	0.9500
C3—H3B	0.9900	C16—H16	0.9500
C4—C5	1.525 (12)	O5—H51	0.8198
C4—H4	1.0000	O5—H52	0.8200

O1—Cu1—O1ⁱ	180.0	O3—C7—C8	109.9 (7)
O1—Cu1—N1	85.6 (3)	O3—C7—C9	101.8 (7)
O1ⁱ—Cu1—N1	94.4 (3)	C8—C7—C9	111.1 (9)
O1—Cu1—N1ⁱ	94.4 (3)	O3—C7—C10	109.6 (7)
O1ⁱ—Cu1—N1ⁱ	85.6 (3)	C8—C7—C10	113.4 (8)
N1—Cu1—N1ⁱ	179.999 (1)	C9—C7—C10	110.6 (8)
C4—N1—C1	107.9 (6)	C7—C8—H8A	109.5
C4—N1—Cu1	108.6 (5)	C7—C8—H8B	109.5
C1—N1—Cu1	112.6 (5)	H8A—C8—H8B	109.5
C4—N1—H	109.3	C7—C8—H8C	109.5
C1—N1—H	109.3	H8A—C8—H8C	109.5
Cu1—N1—H	109.3	H8B—C8—H8C	109.5
C5—O1—Cu1	115.2 (5)	C7—C9—H9A	109.5
C6—O3—C7	120.2 (6)	C7—C9—H9B	109.5
N1—C1—C11	111.2 (6)	H9A—C9—H9B	109.5
N1—C1—C2	101.5 (6)	C7—C9—H9C	109.5
C11—C1—C2	117.7 (6)	H9A—C9—H9C	109.5
N1—C1—H1	108.7	H9B—C9—H9C	109.5
C11—C1—H1	108.7	C7—C10—H10A	109.5
C2—C1—H1	108.7	C7—C10—H10B	109.5
C6—C2—C3	114.5 (7)	H10A—C10—H10B	109.5
C6—C2—C1	113.5 (7)	C7—C10—H10C	109.5
C3—C2—C1	105.9 (6)	H10A—C10—H10C	109.5
C6—C2—H2	107.5	H10B—C10—H10C	109.5
C3—C2—H2	107.5	C16—C11—C12	118.1 (8)
C1—C2—H2	107.5	C16—C11—C1	118.4 (7)
C4—C3—C2	104.2 (6)	C12—C11—C1	123.4 (7)
C4—C3—H3A	110.9	C11—C12—C13	120.3 (8)
C2—C3—H3A	110.9	C11—C12—H12	119.8
C4—C3—H3B	110.9	C13—C12—H12	119.8
C2—C3—H3B	110.9	C14—C13—C12	120.6 (8)
H3A—C3—H3B	108.9	C14—C13—H13	119.7
N1—C4—C5	110.8 (7)	C12—C13—H13	119.7
N1—C4—C3	107.8 (6)	C13—C14—C15	119.7 (9)
C5—C4—C3	113.0 (7)	C13—C14—Br1	120.4 (7)
N1—C4—H4	108.4	C15—C14—Br1	119.8 (7)
C5—C4—H4	108.4	C16—C15—C14	119.9 (8)
C3—C4—H4	108.4	C16—C15—H15	120.0
O2—C5—O1	123.6 (8)	C14—C15—H15	120.0
O2—C5—C4	119.4 (8)	C15—C16—C11	121.0 (8)
O1—C5—C4	116.9 (7)	C15—C16—H16	119.5
O4—C6—O3	125.9 (8)	C11—C16—H16	119.5
O4—C6—C2	124.6 (8)	H51—O5—H52	113.1
O3—C6—C2	109.4 (7)

Symmetry code: (i) −x, −y, −z+2.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O5—H51···O2	0.82	2.15	2.968 (13)	180
O5—H52···O2ⁱⁱ	0.82	2.18	3.001 (14)	180
N1—H···O2ⁱⁱⁱ	0.93	1.99	2.916 (9)	173

Symmetry codes: (ii) −x, −y+1, −z+2; (iii) −x, y−1/2, −z+3/2.

Experimental details

Crystal data
Chemical formula	[Cu(C₁₆H₁₉BrNO₄)₂]·2H₂O
M_r	838.04
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	150
a, b, c (Å)	15.251 (6), 10.555 (4), 10.541 (4)
β (°)	90.423 (6)
V (Å³)	1696.9 (11)
Z	2
Radiation type	Mo Kα
µ (mm⁻¹)	3.06
Crystal size (mm)	0.32 × 0.20 × 0.05

Data collection
Diffractometer	Bruker SMART APEXII diffractometer
Absorption correction	Multi-scan (SADABS; Bruker, 2008)
T_min, T_max	0.441, 0.862
No. of measured, independent and observed [I > 2σ(I)] reflections	12662, 3268, 2968
R_int	0.053
(sin θ/λ)_max (Å⁻¹)	0.617

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.066, 0.161, 1.09
No. of reflections	3268
No. of parameters	218
H-atom treatment	H-atom parameters constrained
	w = 1/[σ²(F_o²) + (0.0259P)² + 19.8322P] where P = (F_o² + 2F_c²)/3
Δρ_max, Δρ_min (e Å⁻³)	0.75, −1.12

Computer programs: APEX2 (Bruker, 2008), SAINT (Bruker, 2008), SHELXTL (Sheldrick, 2008).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O5—H51···O2	0.82	2.15	2.968 (13)	179.8
O5—H52···O2ⁱ	0.82	2.18	3.001 (14)	179.7
N1—H···O2ⁱⁱ	0.93	1.99	2.916 (9)	172.7

Symmetry codes: (i) −x, −y+1, −z+2; (ii) −x, y−1/2, −z+3/2.

Acknowledgements

This study was partially supported by the Russian Foundation for Basic Research (project Nos. 11–03-00630-a and 11–03-91375-ST-a) and State Contract No. 11.519.11.2032.

References

Bruker (2008). APEX2, SADABS and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Kudryavtsev, K. V. (2010). Russ. J. Org. Chem. 46, 372–379. Web of Science CrossRef CAS Google Scholar
Kudryavtsev, K. V., Tsentalovich, M. Yu., Yegorov, A. S. & Kolychev, E. L. (2006). J. Heterocycl. Chem. 43, 1461–1466. CrossRef CAS Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar

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