For the synthesis of (I), CuBr2 (0.44 g, 0.002 mol) was added with intensive
stirring to a solution containing 5-amino-2-methyltetrazole (0.4 g, 0.004 mol)
in 15 ml of methanol–hexane mixture (1:3 v/v). The resulting
green precipitate, obtained simultaneously with the dissolution of copper(II)
bromide, was filtered off, washed with diethyl ether (3 × 5 ml) and
dried in air [0.68 g, yield 81%; m.p. 473 K (decomposition)]. Analyis
calculated: Cu 15.1, Br 38.0%; found: Cu 15.4, Br 38.1%. IR (cm-1): 3328
(s), 3262 (s), 3042 (s), 1600 (sh), 1524
(s), 1464 (w), 1436 (s), 1371 (s), 1351
(w), 1324 (s), 1199 (s), 107 (s), 1070 (s),
1020 (s), 818 (s), 765 (s), 706 (s), 638
(s), 520 (s), 467 (s).
For the synthesis of (II), a solution containing 5-amino-2-methyl-tetrazole
(0.4 g, 0.004 mol) in a mixture of methanol and diethyl ether (1:3
v/v, 15 ml) was added to a solution of CuCl2.2H2O (0.34 g,
0.002 mol) in 10 ml of the same solvent mixture. After stirring the reaction
mixture for 0.5 h, the resulting blue–green precipitate was filtered off,
washed with diethyl ether (3 × 5 ml) and dried in air [0.53 g, yield
80%; m.p. 483 K (decomposition)]. Analysis calculated: Cu 19.1, Cl 21.4%;
found: Cu 19.4, Cl 21.6%. IR (cm-1): 3338 (s), 3267 (s), 3047
(s), 1600 (sh), 1524 (s), 1468 (w), 1436
(s), 1371 (s), 1351 (sh), 1323 (s), 1203
(s), 1109 (w), 1070 (s), 1017 (s), 818 (s),
765 (m), 709 (s), 640 (s), 540 (m), 481
(s).
Powder diffraction patterns of complexes (I) and (II) were indexed using the
program TREOR90 (Werner et al., 1985). As a result,
triclinic
unit cells were found for both compounds, with a = 5.224 Å, b
= 6.512 Å, c = 9.120 Å, α = 99.02°, β = 102.45°, γ = 90.29°
[F20 = 118, M20 = 60, F30 = 111, M30 = 45]
for complex (I), and a = 5.164 Å, b = 6.332 Å, c =
9.002 Å, α = 100.09°, β = 101.47°, γ = 90.41° [F20 = 45,
M20 = 26, F30 = 42, M30 = 20] for complex (II).
Similarity of the obtained unit cells as well as of powder patterns of (I) and
(II) allowed the assumption to be made that the compounds were isotypic. This
prediction was supported later by the obtained results.
Structure solution was performed only for complex (I) using the program
EXPO (Altomare et al., 1999). Both possible space groups,
P1 and P1, were tested, but P1 was found to be
appropriate, allowing a reasonable solution to be obtained. All non-H atoms
were located by stucture solution, with R(F) = 0.124. The solved
structure of (I) was refined with the FULLPROF package
(Rodrigues-Carvajal, 2001). The refined atomic positions in complex (I)
was
used as starting coordinates for complex (II).
Both structures were refined in the same way. The background was adjusted
iteratively at each cycle by using a Fourier filtering technique as
implemented in the FULLPROF program. The pseudo-Voigt profile function
was used to fit the patterns. An asymmetry correction was applied according to
the Bérar–Baldinozzi function (Bérar & Baldinozzi, 1993). A
March–Dollase correction of intensities for the (001) preferred orientation
of plate-like grains (March, 1932; Dollase, 1986) was used in
the Rietveld
refinement. The preferred orientation parameter G1 was refined to
0.7801 (13) for complex (I) and 0.9096 (18) for complex (II). For both
compounds, the G2 parameters were found to be practically equal to 0
and were not included in the final refinement. The displacement parameters of
all non-H atoms were refined isotropically and were constrained to be the
same. The H atoms were placed in calculated positions (Sheldrick,
2008), with
C—H distances of 0.96 Å for the methyl group, N—H distances of 0.90 Å
for the amine group and Uiso(H) = 1.5Uiso(C,N). Pyramidal
geometry was assigned to the amine group in view of its coordination to the Cu
atom. A set of suitable soft restraints on the bond lengths of the ligand
molecule was introduced into the refinement. They were obtained as a result of
analysis of bond lengths in copper(II), palladium(II) and platinum(II)
chloride complexes with 5-amino-2-tert-buthyltetrazole (Voitekhovich
et al., 2009), and a silver complex of 5-amino-2-methyltetrazole
(Karaghiosoff et al., 2009). The bonds were restrained to
1.32 (1) Å
(N1—N2), 1.32 (1) Å (N1—C5), 1.30 (1) Å (N2—N3), 1.32 (1) Å
(N3—N4), 1.33 (1) Å (N4—C5), 1.50 (1) Å (N2—C6) and 1.35 (1) Å
(C5—N7). The final Rietveld refinement plots are shown in Fig. 4.
For both compounds, data collection: Local program; cell refinement: FULLPROF (Rodrigues-Carvajal, 2001); data reduction: Local program. Program(s) used to solve structure: EXPO (Altomare et al., 1999) for (I). For both compounds, program(s) used to refine structure: FULLPROF (Rodrigues-Carvajal, 2001); molecular graphics: PLATON (Spek, 2009); software used to prepare material for publication: FULLPROF (Rodrigues-Carvajal, 2001), PLATON (Spek, 2009).
(I)
catena-poly[[dibromidocopper(II)]-bis(µ-2-methyl-2
H-tetrazol-
5-amine)-
κ2N4:
N5;
κ2N5:
N4]
top
Crystal data top
[CuBr2(C2H5N5)2] | V = 298.56 (2) Å3 |
Mr = 421.57 | Z = 1 |
Triclinic, P1 | F(000) = 203.0 |
Hall symbol: -P 1 | Dx = 2.345 Mg m−3 |
a = 5.22187 (19) Å | Cu Kα radiation, λ = 1.5418 Å |
b = 6.5081 (2) Å | T = 295 K |
c = 9.1165 (3) Å | Particle morphology: finely ground powder |
α = 99.0064 (15)° | green |
β = 102.4480 (15)° | flat sheet, 30 × 30 mm |
γ = 90.2997 (18)° | Specimen preparation: Prepared at 295 K and 100 kPa |
Data collection top
HZG-4A (Carl Zeiss, Jena) diffractometer | Data collection mode: reflection |
Radiation source: fine-focus sealed X-ray tube, BSV-29 | Scan method: step |
Ni filtered monochromator | 2θmin = 8.00°, 2θmax = 110.00°, 2θstep = 0.02° |
Specimen mounting: packed powder pellet | |
Refinement top
Refinement on Inet | Profile function: pseudo-Voigt |
Least-squares matrix: full with fixed elements per cycle | 40 parameters |
Rp = 0.037 | 7 restraints |
Rwp = 0.050 | 0 constraints |
Rexp = 0.029 | H-atom parameters constrained |
RBragg = 0.043 | Weighting scheme based on measured s.u.'s |
χ2 = 3.028 | (Δ/σ)max = 0.002 |
5101 data points | Background function: Fourier filtering |
Excluded region(s): none | Preferred orientation correction: March-Dollase function (March, 1932; Dollase, 1986) |
Crystal data top
[CuBr2(C2H5N5)2] | β = 102.4480 (15)° |
Mr = 421.57 | γ = 90.2997 (18)° |
Triclinic, P1 | V = 298.56 (2) Å3 |
a = 5.22187 (19) Å | Z = 1 |
b = 6.5081 (2) Å | Cu Kα radiation, λ = 1.5418 Å |
c = 9.1165 (3) Å | T = 295 K |
α = 99.0064 (15)° | flat sheet, 30 × 30 mm |
Data collection top
HZG-4A (Carl Zeiss, Jena) diffractometer | Scan method: step |
Specimen mounting: packed powder pellet | 2θmin = 8.00°, 2θmax = 110.00°, 2θstep = 0.02° |
Data collection mode: reflection | |
Refinement top
Rp = 0.037 | 5101 data points |
Rwp = 0.050 | 40 parameters |
Rexp = 0.029 | 7 restraints |
RBragg = 0.043 | H-atom parameters constrained |
χ2 = 3.028 | |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
Cu1 | 1.00000 | 0.00000 | 1.00000 | 0.0288 (4)* | |
Br1 | 1.0113 (4) | −0.3259 (3) | 0.82721 (17) | 0.0288 (4)* | |
N1 | 0.4701 (18) | 0.2743 (17) | 0.6853 (8) | 0.0288 (4)* | |
N2 | 0.6671 (15) | 0.2061 (17) | 0.6214 (8) | 0.0288 (4)* | |
N3 | 0.8551 (17) | 0.1126 (17) | 0.7019 (8) | 0.0288 (4)* | |
N4 | 0.7747 (17) | 0.1165 (16) | 0.8276 (8) | 0.0288 (4)* | |
C5 | 0.550 (2) | 0.215 (3) | 0.8202 (11) | 0.0288 (4)* | |
N7 | 0.3877 (18) | 0.2256 (17) | 0.9193 (9) | 0.0288 (4)* | |
C6 | 0.690 (2) | 0.2569 (19) | 0.4729 (10) | 0.0288 (4)* | |
H7A | 0.30700 | 0.34482 | 0.90462 | 0.0432* | |
H7B | 0.50276 | 0.25817 | 1.00926 | 0.0432* | |
H6A | 0.53613 | 0.32483 | 0.42971 | 0.0432* | |
H6B | 0.70900 | 0.13140 | 0.40589 | 0.0432* | |
H6C | 0.84193 | 0.34817 | 0.48653 | 0.0432* | |
Geometric parameters (Å, º) top
Cu1—Br1 | 2.4452 (18) | N4—C5 | 1.334 (16) |
Cu1—N4 | 2.004 (8) | N7—C5 | 1.360 (14) |
Cu1—N7i | 2.783 (10) | N7—H7A | 0.9000 |
N1—N2 | 1.333 (12) | N7—H7B | 0.9000 |
N1—C5 | 1.328 (15) | C6—H6A | 0.9600 |
N2—N3 | 1.307 (13) | C6—H6B | 0.9600 |
N2—C6 | 1.472 (12) | C6—H6C | 0.9600 |
N3—N4 | 1.299 (11) | | |
| | | |
Br1—Cu1—N4 | 89.2 (3) | N2—N3—N4 | 101.6 (8) |
Br1—Cu1—N7i | 98.4 (2) | Cu1—N4—N3 | 119.1 (7) |
Br1—Cu1—N7ii | 81.6 (2) | Cu1—N4—C5 | 130.4 (7) |
Br1—Cu1—Br1iii | 180.00 | N3—N4—C5 | 110.3 (9) |
Br1—Cu1—N4iii | 90.8 (3) | Cu1iv—N7—C5 | 142.5 (10) |
N4—Cu1—N7i | 81.4 (3) | Cu1iv—N7—H7B | 101.00 |
N4—Cu1—N7ii | 98.6 (3) | C5—N7—H7B | 101.00 |
Br1iii—Cu1—N4 | 90.8 (3) | H7A—N7—H7B | 105.00 |
N4—Cu1—N4iii | 180.00 | C5—N7—H7A | 101.00 |
N7i—Cu1—N7ii | 180.00 | Cu1iv—N7—H7A | 101.00 |
Br1iii—Cu1—N7i | 81.6 (2) | N1—C5—N7 | 120.4 (11) |
N4iii—Cu1—N7i | 98.6 (3) | N4—C5—N7 | 127.6 (12) |
Br1iii—Cu1—N7ii | 98.4 (2) | N1—C5—N4 | 111.0 (9) |
N4iii—Cu1—N7ii | 81.4 (3) | N2—C6—H6A | 110.00 |
Br1iii—Cu1—N4iii | 89.2 (3) | N2—C6—H6B | 110.00 |
N2—N1—C5 | 99.2 (9) | N2—C6—H6C | 109.00 |
N1—N2—N3 | 117.9 (7) | H6A—C6—H6B | 110.00 |
N1—N2—C6 | 121.2 (9) | H6A—C6—H6C | 109.00 |
N3—N2—C6 | 120.6 (8) | H6B—C6—H6C | 109.00 |
Symmetry codes: (i) x+1, y, z; (ii) −x+1, −y, −z+2; (iii) −x+2, −y, −z+2; (iv) x−1, y, z. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
N7—H7A···Br1v | 0.90 | 2.74 | 3.634 (11) | 172 |
N7—H7B···Br1iii | 0.90 | 2.65 | 3.463 (9) | 151 |
Symmetry codes: (iii) −x+2, −y, −z+2; (v) x−1, y+1, z. |
(II)
catena-poly[[dichloridocopper(II)]-bis(µ-2-methyl-2
H-tetrazol-
5-amine)-
κ2N4:
N5;
κ2N5:
N4]
top
Crystal data top
[CuCl2(C2H5N5)2] | V = 282.81 (1) Å3 |
Mr = 332.67 | Z = 1 |
Triclinic, P1 | F(000) = 167.0 |
Hall symbol: -P 1 | Dx = 1.953 Mg m−3 |
a = 5.16248 (13) Å | Cu Kα radiation, λ = 1.5418 Å |
b = 6.32103 (16) Å | T = 295 K |
c = 8.9925 (2) Å | Particle morphology: finely ground powder |
α = 100.1652 (13)° | blue-green |
β = 101.4538 (12)° | flat sheet, 30 × 30 mm |
γ = 90.4234 (12)° | Specimen preparation: Prepared at 295 K and 100 kPa |
Data collection top
HZG-4A (Carl Zeiss, Jena) diffractometer | Data collection mode: reflection |
Radiation source: fine-focus sealed X-ray tube, BSV-29 | Scan method: step |
Ni filtered monochromator | 2θmin = 8.000°, 2θmax = 120.000°, 2θstep = 0.020° |
Specimen mounting: packed powder pellet | |
Refinement top
Refinement on Inet | Profile function: psevdo-Voigt |
Least-squares matrix: full with fixed elements per cycle | 40 parameters |
Rp = 0.030 | 7 restraints |
Rwp = 0.039 | 0 constraints |
Rexp = 0.025 | H-atom parameters constrained |
RBragg = 0.045 | Weighting scheme based on measured s.u.'s |
χ2 = 2.434 | (Δ/σ)max = 0.001 |
5601 data points | Background function: Fourier filtering |
Excluded region(s): none | Preferred orientation correction: March-Dollase function (March, 1932; Dollase, 1986) |
Crystal data top
[CuCl2(C2H5N5)2] | β = 101.4538 (12)° |
Mr = 332.67 | γ = 90.4234 (12)° |
Triclinic, P1 | V = 282.81 (1) Å3 |
a = 5.16248 (13) Å | Z = 1 |
b = 6.32103 (16) Å | Cu Kα radiation, λ = 1.5418 Å |
c = 8.9925 (2) Å | T = 295 K |
α = 100.1652 (13)° | flat sheet, 30 × 30 mm |
Data collection top
HZG-4A (Carl Zeiss, Jena) diffractometer | Scan method: step |
Specimen mounting: packed powder pellet | 2θmin = 8.000°, 2θmax = 120.000°, 2θstep = 0.020° |
Data collection mode: reflection | |
Refinement top
Rp = 0.030 | 5601 data points |
Rwp = 0.039 | 40 parameters |
Rexp = 0.025 | 7 restraints |
RBragg = 0.045 | H-atom parameters constrained |
χ2 = 2.434 | |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
Cu1 | 1.00000 | 0.00000 | 1.00000 | 0.0227 (3)* | |
Cl1 | 1.0253 (4) | −0.3188 (4) | 0.8346 (2) | 0.0227 (3)* | |
N1 | 0.4609 (11) | 0.2789 (10) | 0.6788 (7) | 0.0227 (3)* | |
N2 | 0.6653 (11) | 0.2114 (12) | 0.6192 (7) | 0.0227 (3)* | |
N3 | 0.8589 (11) | 0.1207 (10) | 0.6938 (6) | 0.0227 (3)* | |
N4 | 0.7562 (11) | 0.1194 (10) | 0.8198 (7) | 0.0227 (3)* | |
C5 | 0.5317 (14) | 0.2183 (15) | 0.8152 (7) | 0.0227 (3)* | |
N7 | 0.3871 (11) | 0.2243 (12) | 0.9289 (7) | 0.0227 (3)* | |
C6 | 0.7091 (13) | 0.2576 (12) | 0.4719 (8) | 0.0227 (3)* | |
H7A | 0.32285 | 0.35726 | 0.93370 | 0.03405* | |
H7B | 0.51557 | 0.23496 | 1.01409 | 0.03405* | |
H6A | 0.55753 | 0.32454 | 0.42251 | 0.03405* | |
H6B | 0.73579 | 0.12546 | 0.40610 | 0.03405* | |
H6C | 0.86268 | 0.35217 | 0.48962 | 0.03405* | |
Geometric parameters (Å, º) top
Cu1—Cl1 | 2.305 (2) | N2—C6 | 1.465 (9) |
Cu1—N4 | 2.101 (6) | N3—N4 | 1.344 (8) |
Cu1—N7i | 2.683 (6) | N4—C5 | 1.318 (10) |
Cu1—N7ii | 2.683 (6) | N7—C5 | 1.376 (9) |
Cu1—Cl1iii | 2.305 (2) | N7—H7A | 0.9000 |
Cu1—N4iii | 2.101 (6) | N7—H7B | 0.9000 |
N1—N2 | 1.317 (8) | C6—H6A | 0.9600 |
N1—C5 | 1.332 (9) | C6—H6B | 0.9600 |
N2—N3 | 1.287 (9) | C6—H6C | 0.9600 |
| | | |
Cl1—Cu1—N4 | 90.03 (18) | N2—N3—N4 | 96.4 (5) |
Cl1—Cu1—N7i | 98.04 (16) | Cu1—N4—N3 | 115.4 (4) |
Cl1—Cu1—N7ii | 81.96 (16) | Cu1—N4—C5 | 130.8 (5) |
Cl1—Cu1—Cl1iii | 180.00 | N3—N4—C5 | 113.1 (6) |
Cl1—Cu1—N4iii | 89.97 (18) | Cu1iv—N7—C5 | 140.2 (5) |
N4—Cu1—N7i | 84.2 (2) | Cu1iv—N7—H7B | 102.00 |
N4—Cu1—N7ii | 95.8 (2) | C5—N7—H7B | 102.00 |
Cl1iii—Cu1—N4 | 89.97 (18) | H7A—N7—H7B | 105.00 |
N4—Cu1—N4iii | 180.00 | C5—N7—H7A | 102.00 |
N7i—Cu1—N7ii | 180.00 | Cu1iv—N7—H7A | 102.00 |
Cl1iii—Cu1—N7i | 81.96 (16) | N1—C5—N7 | 128.2 (7) |
N4iii—Cu1—N7i | 95.8 (2) | N4—C5—N7 | 122.2 (7) |
Cl1iii—Cu1—N7ii | 98.04 (16) | N1—C5—N4 | 109.0 (6) |
N4iii—Cu1—N7ii | 84.2 (2) | N2—C6—H6A | 110.00 |
Cl1iii—Cu1—N4iii | 90.03 (18) | N2—C6—H6B | 109.00 |
N2—N1—C5 | 98.7 (6) | N2—C6—H6C | 110.00 |
N1—N2—N3 | 122.5 (6) | H6A—C6—H6B | 109.00 |
N1—N2—C6 | 123.1 (6) | H6A—C6—H6C | 110.00 |
N3—N2—C6 | 114.0 (6) | H6B—C6—H6C | 109.00 |
Symmetry codes: (i) x+1, y, z; (ii) −x+1, −y, −z+2; (iii) −x+2, −y, −z+2; (iv) x−1, y, z. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
N7—H7A···Cl1v | 0.90 | 2.74 | 3.587 (8) | 157 |
N7—H7B···Cl1iii | 0.90 | 2.49 | 3.323 (6) | 154 |
Symmetry codes: (iii) −x+2, −y, −z+2; (v) x−1, y+1, z. |
Experimental details
| (I) | (II) |
Crystal data |
Chemical formula | [CuBr2(C2H5N5)2] | [CuCl2(C2H5N5)2] |
Mr | 421.57 | 332.67 |
Crystal system, space group | Triclinic, P1 | Triclinic, P1 |
Temperature (K) | 295 | 295 |
a, b, c (Å) | 5.22187 (19), 6.5081 (2), 9.1165 (3) | 5.16248 (13), 6.32103 (16), 8.9925 (2) |
α, β, γ (°) | 99.0064 (15), 102.4480 (15), 90.2997 (18) | 100.1652 (13), 101.4538 (12), 90.4234 (12) |
V (Å3) | 298.56 (2) | 282.81 (1) |
Z | 1 | 1 |
Radiation type | Cu Kα, λ = 1.5418 Å | Cu Kα, λ = 1.5418 Å |
Specimen shape, size (mm) | Flat sheet, 30 × 30 | Flat sheet, 30 × 30 |
|
Data collection |
Diffractometer | HZG-4A (Carl Zeiss, Jena) diffractometer | HZG-4A (Carl Zeiss, Jena) diffractometer |
Specimen mounting | Packed powder pellet | Packed powder pellet |
Data collection mode | Reflection | Reflection |
Scan method | Step | Step |
2θ values (°) | 2θmin = 8.00 2θmax = 110.00 2θstep = 0.02 | 2θmin = 8.000 2θmax = 120.000 2θstep = 0.020 |
|
Refinement |
R factors and goodness of fit | Rp = 0.037, Rwp = 0.050, Rexp = 0.029, RBragg = 0.043, χ2 = 3.028 | Rp = 0.030, Rwp = 0.039, Rexp = 0.025, RBragg = 0.045, χ2 = 2.434 |
No. of data points | 5101 | 5601 |
No. of parameters | 40 | 40 |
No. of restraints | 7 | 7 |
H-atom treatment | H-atom parameters constrained | H-atom parameters constrained |
Selected bond lengths (Å) for (I) topCu1—Br1 | 2.4452 (18) | N2—N3 | 1.307 (13) |
Cu1—N4 | 2.004 (8) | N2—C6 | 1.472 (12) |
Cu1—N7i | 2.783 (10) | N3—N4 | 1.299 (11) |
N1—N2 | 1.333 (12) | N4—C5 | 1.334 (16) |
N1—C5 | 1.328 (15) | N7—C5 | 1.360 (14) |
Symmetry code: (i) x+1, y, z. |
Hydrogen-bond geometry (Å, º) for (I) top
D—H···A | D—H | H···A | D···A | D—H···A |
N7—H7A···Br1ii | 0.90 | 2.74 | 3.634 (11) | 172 |
N7—H7B···Br1iii | 0.90 | 2.65 | 3.463 (9) | 151 |
Symmetry codes: (ii) x−1, y+1, z; (iii) −x+2, −y, −z+2. |
Selected bond lengths (Å) for (II) topCu1—Cl1 | 2.305 (2) | N2—N3 | 1.287 (9) |
Cu1—N4 | 2.101 (6) | N2—C6 | 1.465 (9) |
Cu1—N7i | 2.683 (6) | N3—N4 | 1.344 (8) |
N1—N2 | 1.317 (8) | N4—C5 | 1.318 (10) |
N1—C5 | 1.332 (9) | N7—C5 | 1.376 (9) |
Symmetry code: (i) x+1, y, z. |
Hydrogen-bond geometry (Å, º) for (II) top
D—H···A | D—H | H···A | D···A | D—H···A |
N7—H7A···Cl1ii | 0.90 | 2.74 | 3.587 (8) | 157 |
N7—H7B···Cl1iii | 0.90 | 2.49 | 3.323 (6) | 154 |
Symmetry codes: (ii) x−1, y+1, z; (iii) −x+2, −y, −z+2. |
Aminotetrazoles are promising multifunctional ligands, with the amino group and the tetrazole ring N atoms able to be coordinated by metal atoms. This allows the formation of diverse coordination frameworks, resulting in coordination compounds with different structural motifs and properties.
A number of complexes of 5-aminotetrazole and its 1- and 2-substituted derivatives have been synthesized and characterized (see Voitekhovich et al., 2009, and references therein; Gaponik et al., 2006). Analysis of the structural data showed that in all compounds the 5-amine groups were not coordinated to the metal. In the case of 5-amino-1-vinyltetrazole, this fact was explained by the conjugation of the 5-amine group lone pair with the tetrazole π-ring, in accordance with quantum-chemical calculations (Lyakhov et al., 2008). In most investigated complexes with 1,5-diaminotetrazole (Qi et al., 2009; Cui, Zhang, Zhang, Yang, Hu & Zhang, 2008; Cui et al., 2008a,b; Cui, Zhang, Zhang, Yang, Zhang & Shu, 2008), the 1-amine group does not participate in metal coordination; however in the copper(II) chloride complex with this ligand (Gaponik et al., 2005) the 1-amine N atom is bonded to Cu, showing the ability of the 1-amine group to be coordinated by metal.
The present work is devoted to complexes of 2-substituted 5-aminotetrazoles. To date, only structural data for copper(II), palladium(II) and platinum(II) chloride complexes with 5-amino-2-tert-butyltetrazole (Voitekhovich et al., 2009), and also for silver complex of 5-amino-2-methyltetrazole (Karaghiosoff et al., 2009), have been available. In these compounds, the 5-amine group adopts a geometry close to planar and is not included in the coordination environment of the metal atoms. Here, we present the structures of CuII halogenide complexes with 5-amino-2-methyltetrazole, viz. [CuBr2(C2H5N5)2]n, catena-poly[dibromidocopper(II)-bis[µ- (2-methyl-2H-tetrazol-5-yl)amine-κ2N4:N5;κ2N5:N4]], (I), and the isotypic chloride complex, (II). Because it was impossible to obtain single crystals suitable for X-ray analysis, both structures were determined by laboratory X-ray powder diffraction.
Complexes (I) and (II) crystallize in the triclinic space group P1 and are isotypic. The asymmetric units contain a half a Cu atom, one Cl/Br atom and one molecule of 5-amino-2-methyltetrazole (Fig. 1). The Cu atoms lie on inversion centres, whereas all others are in general positions.
In both structures, the 5-amino-2-methyltetrazole molecules reveal similar geometry (Tables 1 and 3). The formally single tetrazole ring bond N2—N3 is rather short, reflecting a tendency to be the shortest in the ring, as follows from previous structural investigations of 2-substituted tetrazoles and their complexes (Voitekhovich et al., 2009; Karaghiosoff et al., 2009; Lyakhov, Degtyarik et al., 2005; Lyakhov, Gaponik et al., 2005, and references therein).
In complexes (I) and (II), the Cu atoms are surrounded by four ligand molecules and two halogen atoms. Two of the four molecules are bonded to the metal through the tetrazole ring N4 atoms, occupying together with two halogen atoms equatorial sites of a distorted coordination octahedron. Two other molecules of the Cu environment are coordinated via the amine N7 atoms, which are distant from the metal by 2.783 (10) Å in complex (I) and 2.683 (6) Å in complex (II) and can be considered as semi-coordinated. Two 5-amino-2-methyltetrazole molecules play the role of bridges between two adjacent Cu atoms in polymeric chains, running along the a axis (Figs. 1 and 2). Halogen atoms do not participate in building the coordination polymer.
In both structures, the amine group H atoms are involved in hydrogen bonds (N7—H7···Br/Cl; Tables 2 and 4). Two H atoms of the amine group are connected with two halogen atoms belonging to different polymeric chains (Fig. 3), to form polymeric layers parallel to the ab plane.
Thus, complexes (I) and (II) are the first examples of coordination of tetrazole ligands via the 5-amine group. Among complexes of 5-aminotetrazole and its 1-substituted derivatives, no such coordination has been observed. Probably, the amine group of 2-substituted 5-aminotetrazoles is conjugated with the tetrazole π-ring to a lesser extent than the 5-amine group of 1-substituted analogues.