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Reaction of pyrazine-2,3-di­carboxyl­ic acid, NaOH, KSCN and Cu(NO3)2·3H2O led to the formation of Na2K2[trans-Cu(C6H2N2O4)2](SCN)2·2H2O, in which the CuII atom, on an inversion centre, is approximately in a square-planar environment. This is a new coordination geometry for copper in complexes of pyrazine-2,3-di­carboxyl­ate.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536803006883/cf6249sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S1600536803006883/cf6249Isup2.hkl
Contains datablock I

CCDC reference: 209905

Key indicators

  • Single-crystal X-ray study
  • T = 293 K
  • Mean [sigma](C-C) = 0.005 Å
  • H-atom completeness 51%
  • R factor = 0.040
  • wR factor = 0.106
  • Data-to-parameter ratio = 11.4

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry

General Notes

FORMU_01 There is a discrepancy between the atom counts in the _chemical_formula_sum and _chemical_formula_moiety. This is usually due to the moiety formula being in the wrong format. Atom count from _chemical_formula_sum: C14 H8 Cu1 K2 N6 Na2 O10 S2 Atom count from _chemical_formula_moiety:C16 H4 Cu1 K2 N6 Na2 O8 S2 FORMU_01 There is a discrepancy between the atom counts in the _chemical_formula_sum and the formula from the _atom_site* data. Atom count from _chemical_formula_sum:C14 H8 Cu1 K2 N6 Na2 O10 S2 Atom count from the _atom_site data: C14 H4 Cu1 K2 N6 Na2 O10 S2 CELLZ_01 From the CIF: _cell_formula_units_Z 2 From the CIF: _chemical_formula_sum C14 H8 Cu K2 N6 Na2 O10 S2 TEST: Compare cell contents of formula and atom_site data atom Z*formula cif sites diff C 28.00 28.00 0.00 H 16.00 8.00 8.00 Cu 2.00 2.00 0.00 K 4.00 4.00 0.00 N 12.00 12.00 0.00 Na 4.00 4.00 0.00 O 20.00 20.00 0.00 S 4.00 4.00 0.00 Difference between formula and atom_site contents detected. WARNING: H atoms missing from atom site list. Is this intentional?

Comment top

Takusagawa & Shimada (1973) first determined the structure of pyrazine-2,3-dicarboxlic acid by single-crystal X-ray analysis. Almost at the same time, the first metal-organic compound of pyrazine-2,3-dicarboxylic acid was reported (Richard et al., 1973). More recently, owing to the interest in supramolecular chemistry, pyrazine-2,3-dicarboxylic acid has been intensely investigated (Smith et al., 1995; Neels et al., 1997; Kondo et al., 1999). For further investigation of pyrazine-2,3-dicarboxylic acid, we synthesized the t itle compound, (I), with a new coordination mode for copper in such complexes. An interesting phenomenon was noted during the synthesis; a blue solid precipitated when pyrazine-2,3-dicarboxylate was added to Cu(NO3)2·3H2O in water, but no product was deposited in the present of SCN. Here we report the synthesis and crystal structure of the title compound.

Compound (I) is composed of K+ and Na+ cations, [trans-Cu(C6H2N2O4)2]2− and SCN anions, and water molecules. As shown in Fig. 1, the CuII atom has centrosymmetric square-planar coordination with trans-positioned O– and N-donor atoms of two pyrazine-2,3-dicarboxylate ligands. The bond distances Cu1—O3 and Cu1—N3 are 1.971 (3) and 1.970 (3) Å, respectively, almost equal to each other, unlike those found in other CuII complexes of pyrazine-2,3-dicarboxylate (Smith et al., 1995; Neels et al., 1997; Kondo et al., 1999). As in the structures of C14H8CuN2O8·2H2O (Yucang, Maochun, Rong & Qian, 2001) and (C28H24CuGd2N4O22)n.2nH2O (Yucang, Maochun, Wiping et al., 2001), the C—O bond distance of the carboxylate group involving the O atom coordinated to copper in the present compound [C6—O3 = 1.276 (4) Å] is a little onger than the other [C6—O4 = 1.237 (4) Å]. However, the two C—O bond distances of the uncoordinated carboxylate group are almost equal, as found in the structure of (C14H22CuN2Na2O16)n (Sileo et al., 1999).

As shown in Fig. 2, the three-dimensional framework is constructed through electrostatic interactions among [trans-Cu(C6H2N2O4)2]2−, SCN, K+ and Na+ ions, together with water molecules. O—H···N hydrogen bonds are found between O1W and the uncoordinated N atom of pyrazine-2,3-dicarboxylate, with a distance of 2.985 (5) Å. Na is six-coordinated, by five O atoms and one N atom, while K is eight-coordinated, by seven O atoms and one N atom (Table 1).

Experimental top

5 ml of a stirred aqueous solution of pyrazine-2,3-dicarboxylic acid (84 mg, 0.5 mmol) was adjusted to pH ca 7 with 1 N NaOH aqueous solution, then KSCN (49 mg, 0.5 mmol) was added. After complete dissolution, Cu(NO3)2·3H2O (60 mg, 0.25 mmol) was added, giving a clear blue solution, which was filtered. Upon evaporation in air, blue prismatic crystals were obtained in a few days (yield 58%).

Refinement top

H atoms were positioned geometrically and refined as riding on their parent atoms; no H atoms were included for the water molecules.

Computing details top

Data collection: SMART (Siemens, 1996); cell refinement: SMART and SAINT (Siemens, 1994); data reduction: SAINT and SHELXTL (Siemens, 1994); program(s) used to solve structure: SHELXTL; program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Figures top
[Figure 1] Fig. 1. The structure of the [trans-Cu(C6H2N2O4)2]2− complex anion, shown with 30% probability ellipsoids. H atoms have been omitted for clarity.
[Figure 2] Fig. 2. The crystal structure of the title compound, viewed along the b axis. H atoms have been omitted and the coordination environments of only one Na ion and one K ion are shown (dotted lines). Dashed lines represent hydrogen bonds.
Dipotassium disodium trans-bis(pyrazine-2,3-dicarboxylato)copper(II) dithiocyanate dihydrate top
Crystal data top
Na2K2[Cu(C6H2N2O4)2](SCN)2·2H2OF(000) = 670
Mr = 672.10Dx = 2.021 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
a = 6.8349 (7) ÅCell parameters from 2150 reflections
b = 6.9692 (7) Åθ = 1.8–25.0°
c = 23.184 (2) ŵ = 1.66 mm1
β = 90.797 (2)°T = 293 K
V = 1104.23 (19) Å3Prism, blue
Z = 20.68 × 0.22 × 0.18 mm
Data collection top
Siemens SMART CCD
diffractometer
1929 independent reflections
Radiation source: fine-focus sealed tube1663 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.025
ω scansθmax = 25.0°, θmin = 1.8°
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
h = 88
Tmin = 0.514, Tmax = 0.741k = 68
3306 measured reflectionsl = 279
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.040Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.106H-atom parameters constrained
S = 1.00 w = 1/[σ2(Fo2) + (0.0473P)2 + 3.7091P]
where P = (Fo2 + 2Fc2)/3
1929 reflections(Δ/σ)max < 0.001
169 parametersΔρmax = 0.50 e Å3
0 restraintsΔρmin = 0.64 e Å3
Crystal data top
Na2K2[Cu(C6H2N2O4)2](SCN)2·2H2OV = 1104.23 (19) Å3
Mr = 672.10Z = 2
Monoclinic, P21/cMo Kα radiation
a = 6.8349 (7) ŵ = 1.66 mm1
b = 6.9692 (7) ÅT = 293 K
c = 23.184 (2) Å0.68 × 0.22 × 0.18 mm
β = 90.797 (2)°
Data collection top
Siemens SMART CCD
diffractometer
1929 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
1663 reflections with I > 2σ(I)
Tmin = 0.514, Tmax = 0.741Rint = 0.025
3306 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0400 restraints
wR(F2) = 0.106H-atom parameters constrained
S = 1.00Δρmax = 0.50 e Å3
1929 reflectionsΔρmin = 0.64 e Å3
169 parameters
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
xyzUiso*/Ueq
Cu10.50000.50000.00000.0253 (2)
K10.66535 (14)0.29284 (15)0.24276 (4)0.0368 (3)
Na10.1562 (2)0.3776 (3)0.18520 (7)0.0342 (4)
S10.39800 (14)0.12607 (14)0.05177 (4)0.0278 (3)
C10.2341 (6)0.2114 (5)0.09809 (17)0.0253 (8)
C20.8786 (5)0.7055 (6)0.01637 (16)0.0252 (8)
H1A0.89930.69340.02300.030*
C31.0162 (6)0.7956 (6)0.05106 (16)0.0265 (9)
H2A1.12720.84660.03410.032*
C40.8302 (5)0.7439 (5)0.13118 (15)0.0185 (7)
C50.6869 (5)0.6576 (5)0.09638 (15)0.0184 (7)
C60.4927 (5)0.5771 (5)0.11627 (15)0.0196 (7)
C70.8251 (5)0.7633 (6)0.19643 (16)0.0230 (8)
N10.1189 (5)0.2741 (5)0.13020 (16)0.0371 (9)
N20.9962 (4)0.8122 (5)0.10792 (13)0.0238 (7)
N30.7161 (4)0.6362 (4)0.03943 (12)0.0195 (6)
O10.9468 (4)0.6603 (5)0.22316 (12)0.0368 (7)
O20.7119 (4)0.8837 (4)0.21772 (11)0.0302 (6)
O30.3746 (4)0.5306 (4)0.07552 (11)0.0259 (6)
O40.4600 (4)0.5583 (4)0.16829 (11)0.0256 (6)
O1W0.2985 (4)0.0653 (5)0.16246 (14)0.0436 (8)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Cu10.0224 (3)0.0366 (4)0.0170 (3)0.0021 (3)0.0017 (2)0.0092 (3)
K10.0341 (5)0.0427 (6)0.0337 (5)0.0073 (4)0.0085 (4)0.0126 (4)
Na10.0277 (8)0.0454 (10)0.0294 (8)0.0050 (7)0.0032 (7)0.0014 (7)
S10.0282 (5)0.0272 (5)0.0279 (5)0.0013 (4)0.0018 (4)0.0016 (4)
C10.028 (2)0.0202 (19)0.028 (2)0.0081 (16)0.0035 (17)0.0020 (16)
C20.029 (2)0.027 (2)0.0199 (18)0.0058 (17)0.0085 (16)0.0012 (16)
C30.0237 (19)0.031 (2)0.025 (2)0.0014 (17)0.0079 (16)0.0009 (17)
C40.0203 (17)0.0171 (17)0.0181 (18)0.0039 (15)0.0013 (14)0.0016 (14)
C50.0214 (17)0.0175 (18)0.0164 (17)0.0031 (14)0.0023 (14)0.0006 (14)
C60.0227 (18)0.0184 (17)0.0177 (17)0.0008 (15)0.0036 (14)0.0000 (14)
C70.0208 (18)0.029 (2)0.0194 (18)0.0079 (16)0.0003 (15)0.0035 (16)
N10.041 (2)0.032 (2)0.038 (2)0.0024 (17)0.0083 (18)0.0031 (17)
N20.0206 (15)0.0276 (17)0.0234 (16)0.0003 (14)0.0041 (13)0.0018 (14)
N30.0242 (15)0.0193 (15)0.0150 (14)0.0037 (13)0.0032 (12)0.0009 (12)
O10.0324 (15)0.056 (2)0.0220 (14)0.0086 (15)0.0050 (12)0.0014 (14)
O20.0276 (14)0.0387 (16)0.0244 (14)0.0037 (13)0.0054 (11)0.0079 (12)
O30.0210 (13)0.0346 (16)0.0222 (13)0.0010 (12)0.0017 (11)0.0058 (12)
O40.0274 (14)0.0298 (15)0.0197 (13)0.0050 (12)0.0052 (11)0.0003 (11)
O1W0.0338 (16)0.054 (2)0.0436 (18)0.0018 (15)0.0078 (14)0.0070 (16)
Geometric parameters (Å, º) top
Cu1—N31.970 (3)C2—H1A0.930
Cu1—N3i1.970 (3)C3—N21.332 (5)
Cu1—O31.971 (3)C3—H2A0.930
Cu1—O3i1.971 (3)C4—N21.350 (5)
K1—O4ii2.776 (3)C4—C51.396 (5)
K1—O2ii2.820 (3)C4—C71.520 (5)
K1—O42.882 (3)C5—N31.346 (4)
K1—O1iii2.906 (3)C5—C61.518 (5)
K1—O1Wiv2.912 (4)C6—O41.237 (4)
K1—O2v2.928 (3)C6—O31.276 (4)
K1—N1vi3.018 (4)C7—O21.248 (5)
K1—O13.239 (3)C7—O11.256 (5)
Na1—N12.370 (4)N1—K1vii3.018 (4)
Na1—O2ii2.413 (3)O1—Na1vi2.596 (4)
Na1—O1W2.445 (4)O1—Na1iv2.710 (3)
Na1—O42.465 (3)O1—K1viii2.906 (3)
Na1—O1vii2.596 (4)O2—Na1iv2.413 (3)
Na1—O1ii2.710 (3)O2—K1iv2.820 (3)
S1—C11.652 (4)O2—K1ix2.928 (3)
C1—N11.161 (5)O4—K1iv2.776 (3)
C2—N31.330 (5)O1W—K1ii2.912 (4)
C2—C31.380 (6)
N3—Cu1—N3i180.00 (15)N3—C2—C3119.8 (3)
N3—Cu1—O382.42 (11)N3—C2—H1A120.1
N3i—Cu1—O397.58 (11)C3—C2—H1A120.1
N3—Cu1—O3i97.58 (11)N2—C3—C2122.5 (3)
N3i—Cu1—O3i82.42 (11)N2—C3—H2A118.8
O3—Cu1—O3i180.00 (7)C2—C3—H2A118.8
O4ii—K1—O2ii66.29 (8)N2—C4—C5120.5 (3)
O4ii—K1—O4132.08 (5)N2—C4—C7113.4 (3)
O2ii—K1—O467.09 (8)C5—C4—C7126.0 (3)
O4ii—K1—O1iii84.30 (8)N3—C5—C4120.1 (3)
O2ii—K1—O1iii144.84 (8)N3—C5—C6113.5 (3)
O4—K1—O1iii143.29 (9)C4—C5—C6126.3 (3)
O4ii—K1—O1Wiv81.20 (9)O4—C6—O3125.0 (3)
O2ii—K1—O1Wiv71.14 (9)O4—C6—C5120.4 (3)
O4—K1—O1Wiv93.95 (9)O3—C6—C5114.6 (3)
O1iii—K1—O1Wiv86.26 (9)O2—C7—O1126.8 (3)
O4ii—K1—O2v67.01 (8)O2—C7—C4118.4 (3)
O2ii—K1—O2v112.66 (9)O1—C7—C4114.6 (3)
O4—K1—O2v124.03 (8)C1—N1—Na1170.2 (3)
O1iii—K1—O2v69.10 (9)C1—N1—K1vii103.6 (3)
O1Wiv—K1—O2v140.92 (9)Na1—N1—K1vii85.12 (12)
O4ii—K1—N1vi140.93 (10)C3—N2—C4117.6 (3)
O2ii—K1—N1vi138.63 (9)C2—N3—C5119.4 (3)
O4—K1—N1vi75.49 (9)C2—N3—Cu1127.8 (3)
O1iii—K1—N1vi76.50 (9)C5—N3—Cu1112.8 (2)
O1Wiv—K1—N1vi130.05 (10)C7—O1—Na1vi129.1 (2)
O2v—K1—N1vi74.38 (9)C7—O1—Na1iv83.7 (2)
O4ii—K1—O1139.44 (8)Na1vi—O1—Na1iv147.18 (12)
O2ii—K1—O1114.56 (9)C7—O1—K1viii123.2 (3)
O4—K1—O172.16 (7)Na1vi—O1—K1viii80.12 (9)
O1iii—K1—O175.41 (5)Na1iv—O1—K1viii81.66 (9)
O1Wiv—K1—O163.00 (8)C7—O1—K197.5 (2)
O2v—K1—O1132.52 (8)Na1vi—O1—K177.22 (9)
N1vi—K1—O167.34 (9)Na1iv—O1—K199.83 (9)
N1—Na1—O2ii142.25 (13)K1viii—O1—K1138.99 (11)
N1—Na1—O1W85.88 (13)C7—O2—Na1iv97.5 (2)
O2ii—Na1—O1W94.13 (12)C7—O2—K1iv123.5 (2)
N1—Na1—O4137.22 (13)Na1iv—O2—K1iv91.41 (9)
O2ii—Na1—O480.48 (10)C7—O2—K1ix143.4 (2)
O1W—Na1—O494.69 (11)Na1iv—O2—K1ix82.67 (9)
N1—Na1—O1vii88.66 (12)K1iv—O2—K1ix92.98 (8)
O2ii—Na1—O1vii82.60 (10)C6—O3—Cu1114.0 (2)
O1W—Na1—O1vii166.35 (13)C6—O4—Na1111.9 (2)
O4—Na1—O1vii97.81 (11)C6—O4—K1iv136.4 (2)
N1—Na1—O1ii92.23 (12)Na1—O4—K1iv85.02 (9)
O2ii—Na1—O1ii51.43 (9)C6—O4—K1124.0 (2)
O1W—Na1—O1ii77.29 (11)Na1—O4—K188.92 (9)
O4—Na1—O1ii129.70 (10)K1iv—O4—K194.92 (8)
O1vii—Na1—O1ii90.46 (6)Na1—O1W—K1ii116.59 (12)
N1—C1—S1179.0 (4)
Symmetry codes: (i) x+1, y+1, z; (ii) x+1, y1/2, z+1/2; (iii) x+2, y1/2, z+1/2; (iv) x+1, y+1/2, z+1/2; (v) x, y1, z; (vi) x+1, y, z; (vii) x1, y, z; (viii) x+2, y+1/2, z+1/2; (ix) x, y+1, z.

Experimental details

Crystal data
Chemical formulaNa2K2[Cu(C6H2N2O4)2](SCN)2·2H2O
Mr672.10
Crystal system, space groupMonoclinic, P21/c
Temperature (K)293
a, b, c (Å)6.8349 (7), 6.9692 (7), 23.184 (2)
β (°) 90.797 (2)
V3)1104.23 (19)
Z2
Radiation typeMo Kα
µ (mm1)1.66
Crystal size (mm)0.68 × 0.22 × 0.18
Data collection
DiffractometerSiemens SMART CCD
diffractometer
Absorption correctionMulti-scan
(SADABS; Sheldrick, 1996)
Tmin, Tmax0.514, 0.741
No. of measured, independent and
observed [I > 2σ(I)] reflections
3306, 1929, 1663
Rint0.025
(sin θ/λ)max1)0.595
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.040, 0.106, 1.00
No. of reflections1929
No. of parameters169
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.50, 0.64

Computer programs: SMART (Siemens, 1996), SMART and SAINT (Siemens, 1994), SAINT and SHELXTL (Siemens, 1994), SHELXTL.

Selected geometric parameters (Å, º) top
Cu1—N31.970 (3)Na1—N12.370 (4)
Cu1—O31.971 (3)Na1—O2i2.413 (3)
K1—O4i2.776 (3)Na1—O1W2.445 (4)
K1—O2i2.820 (3)Na1—O42.465 (3)
K1—O42.882 (3)Na1—O1vi2.596 (4)
K1—O1ii2.906 (3)Na1—O1i2.710 (3)
K1—O1Wiii2.912 (4)C6—O41.237 (4)
K1—O2iv2.928 (3)C6—O31.276 (4)
K1—N1v3.018 (4)C7—O21.248 (5)
K1—O13.239 (3)C7—O11.256 (5)
N3—Cu1—O382.42 (11)O2—C7—O1126.8 (3)
O4—C6—O3125.0 (3)O2—C7—C4118.4 (3)
O4—C6—C5120.4 (3)C6—O3—Cu1114.0 (2)
Symmetry codes: (i) x+1, y1/2, z+1/2; (ii) x+2, y1/2, z+1/2; (iii) x+1, y+1/2, z+1/2; (iv) x, y1, z; (v) x+1, y, z; (vi) x1, y, z.
 

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