3,4,6-Tris­(pyrazol-1-yl)­pyridazine

In the structure of the title compound, C₁₃H₁₀N₈, a tetradentate N₄-donor ligand derivatized on the pyridazine backbone with a monodentate N-donor group, the four potentially coordinating N atoms of the pyridazine and 3- and 6-pyrazole rings adopt a trans–trans conformation. Although the 6-substituted pyrazole ring is almost coplanar with the pyridazine ring, the 3- and 4-substituted pyrazole rings are severely bent out of the plane of the pyridazine ring. These features suggest that it may not be possible to arrange the four adjacent N-donors such that the mol­ecule can act as a bis-bidentate chelating ligand. An analysis of the extended structure of the title compound reveals a very short, offset face-to-face π–π interaction involving the pyridazine and 6-substituted pyrazole rings of adjacent mol­ecules.

Key indicators

• Single-crystal X-ray study
• T = 298 K
• Mean [sigma](C-C) = 0.010 Å
• R factor = 0.081
• wR factor = 0.168
• Data-to-parameter ratio = 8.9

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


 Alert Level A:



THETM_01  Alert A The value of sine(theta_max)/wavelength is less than 0.550
          Calculated sin(theta_max)/wavelength =    0.5380


 Alert Level C:



REFNR_01  Alert C Ratio of reflections to parameters is < 10 for a
          centrosymmetric structure
          sine(theta)/lambda                0.5380
          Proportion of unique data used    1.0000
          Ratio reflections to parameters   8.8842

RINTA_01  Alert C The value of Rint is greater than 0.10
          Rint given   0.117


 1 Alert Level A = Potentially serious problem

 0 Alert Level B = Potential problem

 2 Alert Level C = Please check

---

S1. Comment

Pyridazines substituted in the 3- and 6-positions with N-donor ligands act as tetradentate N₄-donor ligands in a bis-bidentate chelating fashion, generating multinuclear coordination complexes with relatively short internuclear separations [d(M···M) ca 3.6 Å; Thompson et al., 1985; Youinou et al., 1992, Hubberstey & Russell, 1995].

In an attempt to introduce a third ligating centre to these molecules, we have prepared 3,4,6-tris(pyrazol-1-yl)pyridazine, (I), a bis-bidentate N₄-donor ligand derivitized on the pyridazine backbone with a monodentate N-donor group. Its molecular structure is shown in Fig. 1. Two noteworthy points emerge. Firstly, the four N atoms on the pyridazine and 3- and 6-pyrazole rings adopt a trans–trans conformation, which contrasts with the cis–cis conformation required for the tetradentate N₄-donor ligands to act in a bis-bidentate chelating fashion. Secondly, although the 6-substituted pyrazole ring is almost coplanar with the pyridazine ring [dihedral angle 5.5 (4)°], the 3- and 4-substituted pyrazole rings are severely bent out of the plane of the pyridazine ring [dihedral angles 40.2 (3) and 51.2 (2)°, respectively]. Unfortunately, both points, but especially the latter, which can be attributed to steric conflict between the adjacent pyrazole substituents on the 3- and 4-positions of the pyridazine ring, suggest that it may not be possible to arrange the four adjacent N-donor centres for it to act as a bis-bidentate chelating ligand.

An analysis of the extended structure reveals the existence of a very short offset face-to-face (off) π–π interaction involving the pyridazine and 6-substituted pyrazole ring of adjacent molecules (Fig. 2). The perpendicular separation between the least-squares mean planes covering these two rings [the maximum deviation of fitted atoms from best plane is 0.10 Å] is very short [3.339 (12) Å; range 3.244–3.409 Å]. As each tris(pyrazol-1-yl)pyridazine molecule forms part of a weakly C—H···N hydrogen-bonded chain [C34—H34 = 0.93, H34···N42 = 2.62, C34···N42 = 3.515 (8) Å and C34—H34···N42 162°; C35—H35 = 0.93, H35···N62 = 2.50, C35···N62 = 3.413 (8) Å and C35—H36···N62168°] aligned in the [101] direction (Fig. 3), the off π–π interactions link the chains to give a three-dimensional matrix (Fig. 4).

S2. Experimental

Sodium hydride (0.98 g, 245 mmol) was added to a solution of pyrazole (1.12 g, 165 mmol) in pre-dried tetrahydrofuran (50 ml). After stirring the mixture for 20 min, 3,4,6-trichloropyridazine (1.00 g, 54 mmol) was added to the solution (caution: exothermic reaction!) and the mixture stirred for a further 60 min. After cooling to room temperature, the solvent was removed and the resultant solid dissolved in dichloromethane (40 ml) and washed with water (3 × 30 ml). The organic layer was dried over magnesium sulfate and the solvent removed to give a white powder, which was recrystallized from ethanol (yield; 1.32 g, 47 mmol, 88%) to give crystals suitable for diffraction analysis. Found (calculated for C₁₃H₁₀N₈): C 55.90 (56.10), H 3.60 (3.60), N 40.20% (40.25%). IR (KBr disc) (ν/cm⁻¹): 3132 (m), 1594 (s), 1562 (s), 1526 (s), 1456 (s), 1424 (s), 1396 (s), 1336 (s), 1323 (m), 1198 (s), 1189 (m), 1175 (s), 1113 (m), 1098 (m), 1059 (s), 1045 (s), 1031 (s), 1015 (s), 954 (s), 939 (s), 902 (s), 893 (s), 865 (m), 811 (s), 777 (s), 759 (s), 669 (m), 649 (m), 624 (s), 599 (s), 584 (m), 521 (m), 487 (m), 443 (m). ¹H NMR (CDCl₃) δ/p.p.m.: 6.45 (m, 1H), 6.68 (m, 2H), 6.80 (d, 1H), 7.81 (d, 1H), 7.84 (d, 1H), 7.93 (d, 1H), 8.21 (dd, 1H), 8.71 (s, 1H), 8.84 (dd, 1H). EI—MS (m/z) 278 [C₁₃H₁₀N₈]⁺.

S3. Refinement

This crystal diffracted only to low resolution. No significant diffraction occurred beyond 2θ of 45°, which accounts for the high value of R_int (0.117). All H atoms were included at geometrically calculated positions and constrained to ride at a distance of 0.93 Å from their parent C atoms, with U_iso(H) = 1.2U_eq(C).

Computing details

Data collection: STADI4 (Stoe & Cie, 1997); cell refinement: STADI4; data reduction: X-RED (Stoe & Cie, 1997); program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: CAMERON (Watkin et al., 1996); software used to prepare material for publication: SHELXL97 and PLATON (Spek, 2002).

Figures

	Fig. 1. The molecular structure and atom-numbering scheme of 3,4,6-tris(pyrazol-1-yl)pyridazine. Displacement ellipsoids are drawn at 30% probability and H atoms are shown as spheres of arbitrary radii.
	Fig. 2. A projection of the structure onto the least-squares mean plane containing the pyridazine and 6-substituted pyrazole rings, showing the π–π-stacking interactions between adjacent molecules.
	Fig. 3. A projection of the structure of on to the (010) plane, showing the C34—H34···N62 and C35—H35···N42 hydrogen-bonding interactions, which generate the chain of molecules aligned along the [101] direction. Key: C black circles, N blue circles and H small yellow circles.
	Fig. 4. A view of the structure showing the π–π-stacking interactions linking the hydrogen-bonded chains. Key: C black circles, N blue circles and H small yellow circles.

3,4,6-Tris(pyrazol-1-yl)pyridazine

Crystal data

C13H10N8	F(000) = 576
Mr = 278.29	Dx = 1.429 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
a = 13.190 (5) Å	Cell parameters from 29 reflections
b = 7.003 (3) Å	θ = 10.0–12.0°
c = 14.326 (4) Å	µ = 0.10 mm^−1
β = 102.14 (3)°	T = 298 K
V = 1293.7 (8) Å^3	Plate, colourless
Z = 4	0.23 × 0.23 × 0.02 mm

Data collection

Stoe Stadi-4 four-circle diffractometer	Rint = 0.117
Radiation source: fine-focus sealed tube	θmax = 22.5°, θmin = 2.9°
Graphite monochromator	h = −14→14
ω/θ scans	k = 0→7
3374 measured reflections	l = −15→15
1688 independent reflections	3 standard reflections every 60 min
856 reflections with I > 2σ(I)	intensity decay: none

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.081	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.168	H-atom parameters constrained
S = 1.19	w = 1/[σ^2(Fo^2) + (0.014P)^2 + 1.704P] where P = (Fo^2 + 2Fc^2)/3
1688 reflections	(Δ/σ)max = 0.001
190 parameters	Δρmax = 0.19 e Å^−3
0 restraints	Δρmin = −0.27 e Å^−3

Special details

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 (Ų)

	x	y	z	Uiso*/Ueq
N1	0.7987 (4)	0.0765 (9)	0.8711 (4)	0.0507 (17)
N2	0.7819 (4)	0.0605 (9)	0.7754 (4)	0.0525 (18)
C3	0.8456 (5)	0.1426 (11)	0.7282 (4)	0.046 (2)
C4	0.9301 (4)	0.2556 (10)	0.7723 (5)	0.0407 (18)
C5	0.9512 (5)	0.2662 (11)	0.8702 (4)	0.047 (2)
H5	1.0078	0.3335	0.9042	0.056*
C6	0.8826 (5)	0.1702 (11)	0.9153 (5)	0.0449 (18)
N31	0.8264 (4)	0.1013 (9)	0.6291 (4)	0.0488 (18)
N32	0.9050 (4)	0.0317 (10)	0.5902 (4)	0.066 (2)
C33	0.8615 (5)	0.0006 (13)	0.5001 (5)	0.065 (2)
H33	0.8964	−0.0473	0.4551	0.078*
C34	0.7559 (5)	0.0484 (12)	0.4802 (5)	0.060 (2)
H34	0.7093	0.0384	0.4219	0.072*
C35	0.7362 (5)	0.1121 (10)	0.5636 (5)	0.051 (2)
H35	0.6729	0.1551	0.5741	0.061*
N41	0.9914 (4)	0.3572 (9)	0.7189 (4)	0.0498 (17)
N42	1.0948 (4)	0.3754 (10)	0.7546 (4)	0.061 (2)
C43	1.1257 (6)	0.4956 (13)	0.6942 (5)	0.065 (2)
H43	1.1939	0.5364	0.7003	0.078*
C44	1.0444 (6)	0.5539 (13)	0.6206 (5)	0.066 (2)
H44	1.0477	0.6362	0.5704	0.080*
C45	0.9588 (5)	0.4627 (12)	0.6390 (5)	0.059 (2)
H45	0.8913	0.4716	0.6034	0.071*
N61	0.9024 (4)	0.1662 (9)	1.0150 (4)	0.0472 (16)
N62	0.9884 (4)	0.2537 (9)	1.0675 (4)	0.0496 (17)
C63	0.9837 (5)	0.2201 (11)	1.1569 (5)	0.054 (2)
H63	1.0322	0.2640	1.2093	0.064*
C64	0.8969 (6)	0.1102 (11)	1.1632 (5)	0.061 (2)
H64	0.8777	0.0683	1.2186	0.073*
C65	0.8469 (5)	0.0775 (12)	1.0727 (5)	0.064 (3)
H65	0.7862	0.0078	1.0531	0.077*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.043 (3)	0.064 (5)	0.044 (4)	−0.011 (3)	0.007 (3)	−0.007 (3)
N2	0.041 (4)	0.069 (5)	0.047 (4)	−0.006 (3)	0.008 (3)	−0.005 (4)
C3	0.038 (4)	0.063 (6)	0.035 (4)	−0.002 (4)	0.004 (3)	−0.008 (4)
C4	0.031 (4)	0.051 (5)	0.040 (4)	−0.002 (4)	0.007 (3)	0.003 (4)
C5	0.032 (4)	0.062 (6)	0.044 (4)	−0.007 (4)	0.005 (3)	−0.005 (4)
C6	0.044 (4)	0.052 (5)	0.038 (4)	0.003 (4)	0.009 (3)	−0.002 (4)
N31	0.033 (3)	0.068 (5)	0.044 (3)	0.006 (3)	0.005 (3)	−0.012 (3)
N32	0.045 (3)	0.101 (6)	0.051 (4)	0.012 (4)	0.005 (3)	−0.024 (4)
C33	0.060 (5)	0.088 (7)	0.049 (5)	−0.002 (5)	0.017 (4)	−0.015 (5)
C34	0.048 (4)	0.091 (7)	0.033 (4)	0.003 (5)	−0.004 (3)	0.007 (5)
C35	0.028 (4)	0.066 (6)	0.051 (5)	0.006 (4)	−0.008 (3)	−0.007 (4)
N41	0.037 (3)	0.073 (5)	0.039 (3)	−0.006 (3)	0.006 (3)	0.000 (4)
N42	0.037 (3)	0.102 (6)	0.046 (4)	−0.008 (4)	0.009 (3)	0.009 (4)
C43	0.056 (5)	0.093 (7)	0.052 (5)	−0.012 (5)	0.022 (4)	0.001 (5)
C44	0.065 (5)	0.097 (7)	0.040 (4)	−0.007 (5)	0.017 (4)	0.012 (5)
C45	0.052 (5)	0.087 (7)	0.032 (4)	0.001 (5)	−0.003 (3)	0.005 (5)
N61	0.041 (3)	0.062 (5)	0.041 (3)	−0.012 (3)	0.014 (3)	0.002 (3)
N62	0.048 (4)	0.063 (5)	0.037 (3)	−0.007 (3)	0.007 (3)	−0.006 (3)
C63	0.059 (5)	0.062 (6)	0.036 (4)	0.004 (4)	0.003 (4)	−0.001 (4)
C64	0.072 (5)	0.062 (6)	0.053 (5)	−0.014 (5)	0.023 (4)	0.011 (4)
C65	0.053 (4)	0.086 (7)	0.056 (5)	−0.017 (5)	0.017 (4)	0.003 (5)

Geometric parameters (Å, º)

N1—N2	1.347 (7)	C43—C44	1.397 (9)
N1—C6	1.327 (8)	C44—C45	1.370 (9)
N2—C3	1.316 (8)	N61—C65	1.362 (8)
C3—C4	1.404 (8)	N61—N62	1.368 (7)
C3—N31	1.419 (7)	N62—C63	1.316 (7)
C4—C5	1.373 (8)	C63—C64	1.399 (9)
C4—N41	1.415 (7)	C64—C65	1.346 (9)
C5—C6	1.390 (9)	C5—H5	0.9300
C6—N61	1.398 (7)	C33—H33	0.9300
N31—C35	1.353 (7)	C34—H34	0.9300
N31—N32	1.366 (6)	C35—H35	0.9300
N32—C33	1.316 (8)	C43—H43	0.9300
C33—C34	1.402 (8)	C44—H44	0.9300
C34—C35	1.351 (8)	C45—H45	0.9300
N41—C45	1.355 (8)	C63—H63	0.9300
N41—N42	1.358 (6)	C64—H64	0.9300
N42—C43	1.331 (9)	C65—H65	0.9300
C6—N1—N2	118.0 (5)	C65—N61—C6	128.3 (6)
C3—N2—N1	120.0 (5)	N62—N61—C6	120.5 (6)
N2—C3—C4	123.2 (6)	C63—N62—N61	104.6 (5)
N2—C3—N31	115.2 (6)	N62—C63—C64	111.6 (6)
C4—C3—N31	121.5 (6)	C65—C64—C63	105.8 (6)
C5—C4—C3	117.4 (6)	C64—C65—N61	106.9 (7)
C5—C4—N41	120.6 (6)	C4—C5—H5	122.1
C3—C4—N41	122.0 (6)	C6—C5—H5	122.1
C4—C5—C6	115.9 (6)	N32—C33—H33	124.1
N1—C6—C5	125.2 (6)	C34—C33—H33	124.1
N1—C6—N61	115.8 (6)	C35—C34—H34	127.3
C5—C6—N61	119.0 (6)	C33—C34—H34	127.3
C35—N31—N32	111.7 (5)	C34—C35—H35	126.6
C35—N31—C3	128.9 (6)	N31—C35—H35	126.6
N32—N31—C3	119.4 (5)	N42—C43—H43	123.7
C33—N32—N31	104.3 (5)	C44—C43—H43	123.7
N32—C33—C34	111.7 (6)	C45—C44—H44	127.7
C35—C34—C33	105.4 (6)	C43—C44—H44	127.7
C34—C35—N31	106.9 (6)	N41—C45—H45	126.6
C45—N41—N42	112.4 (6)	C44—C45—H45	126.6
C45—N41—C4	128.0 (6)	N62—C63—H63	124.2
N42—N41—C4	119.1 (5)	C64—C63—H63	124.2
C43—N42—N41	103.6 (6)	C65—C64—H64	127.1
N42—C43—C44	112.6 (7)	C63—C64—H64	127.1
C45—C44—C43	104.6 (7)	C64—C65—H65	126.6
N41—C45—C44	106.8 (6)	N61—C65—H65	126.6
C65—N61—N62	111.1 (5)
C6—N1—N2—C3	−2.5 (10)	C3—N31—C35—C34	−176.7 (8)
N1—N2—C3—C4	−2.7 (11)	C5—C4—N41—C45	−135.1 (8)
N1—N2—C3—N31	174.1 (6)	C3—C4—N41—C45	44.1 (11)
N2—C3—C4—C5	5.5 (11)	C5—C4—N41—N42	36.1 (10)
N31—C3—C4—C5	−171.1 (7)	C3—C4—N41—N42	−144.6 (7)
N2—C3—C4—N41	−173.8 (7)	C45—N41—N42—C43	−0.1 (8)
N31—C3—C4—N41	9.6 (11)	C4—N41—N42—C43	−172.6 (6)
C3—C4—C5—C6	−3.0 (10)	N41—N42—C43—C44	−0.2 (9)
N41—C4—C5—C6	176.3 (6)	N42—C43—C44—C45	0.4 (10)
N2—N1—C6—C5	5.0 (11)	N42—N41—C45—C44	0.3 (9)
N2—N1—C6—N61	−173.7 (6)	C4—N41—C45—C44	172.0 (7)
C4—C5—C6—N1	−2.1 (11)	C43—C44—C45—N41	−0.4 (9)
C4—C5—C6—N61	176.6 (7)	N1—C6—N61—C65	0.4 (12)
N2—C3—N31—C35	50.2 (11)	C5—C6—N61—C65	−178.4 (7)
C4—C3—N31—C35	−132.9 (7)	N1—C6—N61—N62	178.2 (6)
N2—C3—N31—N32	−126.2 (7)	C5—C6—N61—N62	−0.7 (11)
C4—C3—N31—N32	50.7 (10)	C65—N61—N62—C63	−1.0 (8)
C35—N31—N32—C33	0.1 (9)	C6—N61—N62—C63	−179.1 (7)
C3—N31—N32—C33	177.1 (7)	N61—N62—C63—C64	0.8 (9)
N31—N32—C33—C34	−0.1 (10)	N62—C63—C64—C65	−0.3 (10)
N32—C33—C34—C35	0.2 (11)	C63—C64—C65—N61	−0.3 (9)
C33—C34—C35—N31	−0.1 (9)	N62—N61—C65—C64	0.8 (9)
N32—N31—C35—C34	0.0 (9)	C6—N61—C65—C64	178.7 (7)