Related literature {#sec1}
==================

For the synthesis, structures and analgesic and anti-inflammatory activity of substituted pyridazine derivatives, see: Boissier *et al.* (1963[@bb2]); Gokce *et al.* (2001[@bb8], 2004[@bb9], 2005[@bb7], 2009[@bb10]); Sahin *et al.* (2004[@bb11]); Dundar *et al.* (2007[@bb5]). For general background to non-opioid analgesic derivatives, see: Sato *et al.* (1981[@bb12]); Banoglu *et al.* (2004[@bb1]); Giovannoni *et al.* (2003[@bb6])·For puckering parameters, see: Cremer & Pople (1975[@bb4]).

Experimental {#sec2}
============

 {#sec2.1}

### Crystal data {#sec2.1.1}

C~13~H~14~ClN~5~*M* *~r~* = 275.74Triclinic,*a* = 5.912 (3) Å*b* = 8.088 (5) Å*c* = 13.689 (8) Åα = 83.359 (9)°β = 83.019 (9)°γ = 75.168 (9)°*V* = 625.5 (6) Å^3^*Z* = 2Mo *K*α radiationμ = 0.30 mm^−1^*T* = 296 K0.16 × 0.15 × 0.14 mm

### Data collection {#sec2.1.2}

Bruker APEXII CCD diffractometerAbsorption correction: multi-scan (*SADABS*; Bruker, 2008[@bb3]) *T* ~min~ = 0.954, *T* ~max~ = 0.95911395 measured reflections3275 independent reflections2264 reflections with *I* \> 2σ(*I*)*R* ~int~ = 0.049

### Refinement {#sec2.1.3}

*R*\[*F* ^2^ \> 2σ(*F* ^2^)\] = 0.039*wR*(*F* ^2^) = 0.095*S* = 0.953275 reflections172 parametersH-atom parameters constrainedΔρ~max~ = 0.27 e Å^−3^Δρ~min~ = −0.23 e Å^−3^

 {#d5e453}

Data collection: *APEX2* (Bruker (2008[@bb3]); cell refinement: *SAINT* (Bruker, 2008[@bb3]); data reduction: *SAINT*; program(s) used to solve structure: *SHELXS97* (Sheldrick, 2008[@bb13]); program(s) used to refine structure: *SHELXL97* (Sheldrick, 2008[@bb13]); molecular graphics: *SHELXTL* (Sheldrick, 2008[@bb13]); software used to prepare material for publication: *SHELXTL*.

Supplementary Material
======================

Crystal structure: contains datablocks I, global. DOI: [10.1107/S1600536809050727/hg2610sup1.cif](http://dx.doi.org/10.1107/S1600536809050727/hg2610sup1.cif)

Structure factors: contains datablocks I. DOI: [10.1107/S1600536809050727/hg2610Isup2.hkl](http://dx.doi.org/10.1107/S1600536809050727/hg2610Isup2.hkl)

Additional supplementary materials: [crystallographic information](http://scripts.iucr.org/cgi-bin/sendsupfiles?hg2610&file=hg2610sup0.html&mime=text/html); [3D view](http://scripts.iucr.org/cgi-bin/sendcif?hg2610sup1&Qmime=cif); [checkCIF report](http://scripts.iucr.org/cgi-bin/paper?hg2610&checkcif=yes)

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: [HG2610](http://scripts.iucr.org/cgi-bin/sendsup?hg2610)).

Comment
=======

The opioid derivative analgesics have significant side effects, therefore, the current research is focused on non-opioid analgesics that do not have serious side effects but are as effective as the opioids. One of the non-opioid analgesic derivatives is emorfazone which has a substituted pyridazine (Sato *et al.*, 1981). In addition, some pyridazinone derivatives bearing an alkylpiperazinyl alkyl moiety also show interesting antinociceptive activity (Banoglu *et al.*, 2004; Giovannoni *et al.*, 2003).

Recently, our team focused on the synthesis, characterization, and analgesics-anti-inflammatory activity of substituted pyridazine derivatives (Dundar *et al.*, 2007; Gokce *et al.*, 2001, 2004, 2005, 2009; Sahin *et al.*, 2004). The compound, 3-chloro-6-(4-pyridin-2-ylpiperazin-1-yl)pyridazine, (I), Scheme 1, is one example and in this article we report on the crystal structure of the title compound, Figure 1.

The molecular structure of (I) consists of 3-chloropyridazine and pyridine arms connected to a piperazine ring. The 3-chloropyridazine and pyridine rings are planar with a maximum deviation of 0.006 (1) Å for atom C4 and -0.014 (2) Å for atom C12. The dihedral angle between these two rings is 13.91 (7) °. The piperazine ring adopts a chair conformation. This is confirmed by the puckering parameters *q*~2~ = 0.0056 (13) Å, *q*~3~ = -0.5388 (13) Å, *Q*~T~ = 0.5388 (13) Å, *θ* = 179.67 (14) ° and φ = 221 (14) ° (Cremer & Pople, 1975).

The conformations of the 3-chloropyridazine and pyridine rings are best described by the torsion angles of -155.41 (12) ° and 156.51 (12) ° for C4---N3---C5---C6 and C9---N4---C7---C8, respectively; thus they adopt - antiperiplanar and + antiperiplanar conformations, respectively.

The crystal packing is dominated by weak intermolecular C3---H3···N1 (1 + *x*, *y*, *z*) hydrogen bonds, with H···N = 2.58 Å and a C---H···N angle of 140 ° (Figure 2).

Experimental {#experimental}
============

A mixture of 3,6-dichloropyridazine, (II), (1.7 mol) and 1-(2-pyridyl)piperazine, (III), (2.0 mol) in ethanol (10 ml) was heated under reflux for 4 h after which the mixture was cooled to room temperature (Figure 3) (Boissier *et al.*, 1963). The resulting crude precipitate was filtered off and purified by repeated washing with small portions of cold ethanol. The precipitate formed was crystallized from CH~2~Cl~2~:ethanol (5:10) to give the compound 3-chloro-6-(4-pyridin-2-ylpiperazin-1-yl) pyridazine, (I), as white crystals. Yields: 0.270 g, 58%. *M*.p.: 153 °C. ^1^H NMR (DMSO-d~6~) δ: 8.16--8.13 (d, 1H, pyridyl), 7.63--7.56 (m, 2H, pyridyl), 7.47--7.44 (d, 1H, pyridazin), 6.93--6.89 (d, 1H, pyridyl), 6.75--6.66 (d, 1H, pyridazin), 3.73--3.62(m, 4H, piperazine), 3.17--3.14 (m, 4H, piperazine). MS (EI) m/*z*: 276 (*M*^+^). Anal. Calc. for C~13~H~14~N~5~Cl: C, 56.63; H, 5.12; N, 25.40%. Found: C, 56.60; H, 5.10; N, 24.42%.

Refinement {#refinement}
==========

The H atoms were positioned geometrically and allowed to ride on their parent atoms, with C---H distances of 0.93 Å (CH) or 0.97 Å (CH~2~), and with *U*~iso~(H) = 1.2*U*~eq~ of the parent atoms.

Figures
=======

![The molecular structure of (I), showing ellipsoids at the 50% probability level.](e-66-00o35-fig1){#Fap1}

![The molecular packing of (I). The hydrogen bonds are shown as dashed lines.](e-66-00o35-fig2){#Fap2}

![Preparation of compound (I)](e-66-00o35-fig3){#Fap3}

Crystal data {#tablewrapcrystaldatalong}
============

  ---------------------- ---------------------------------------
  C~13~H~14~ClN~5~       *Z* = 2
  *M~r~* = 275.74        *F*(000) = 288
  Triclinic, *P*1        *D*~x~ = 1.464 Mg m^−3^
  Hall symbol: -P 1      Mo *K*α radiation, λ = 0.71073 Å
  *a* = 5.912 (3) Å      Cell parameters from 2718 reflections
  *b* = 8.088 (5) Å      θ = 2.6--28.2°
  *c* = 13.689 (8) Å     µ = 0.30 mm^−1^
  α = 83.359 (9)°        *T* = 296 K
  β = 83.019 (9)°        Block, colourless
  γ = 75.168 (9)°        0.16 × 0.15 × 0.14 mm
  *V* = 625.5 (6) Å^3^   
  ---------------------- ---------------------------------------

Data collection {#tablewrapdatacollectionlong}
===============

  ------------------------------------------------------------ --------------------------------------
  Bruker APEXII CCD diffractometer                             3275 independent reflections
  Radiation source: fine-focus sealed tube                     2264 reflections with *I* \> 2σ(*I*)
  graphite                                                     *R*~int~ = 0.049
  φ and ω scans                                                θ~max~ = 29.0°, θ~min~ = 1.5°
  Absorption correction: multi-scan (*SADABS*; Bruker, 2008)   *h* = −8→7
  *T*~min~ = 0.954, *T*~max~ = 0.959                           *k* = −10→11
  11395 measured reflections                                   *l* = −18→18
  ------------------------------------------------------------ --------------------------------------

Refinement {#tablewraprefinementdatalong}
==========

  ------------------------------------- -------------------------------------------------------------------------------------
  Refinement on *F*^2^                  Primary atom site location: structure-invariant direct methods
  Least-squares matrix: full            Secondary atom site location: difference Fourier map
  *R*\[*F*^2^ \> 2σ(*F*^2^)\] = 0.039   Hydrogen site location: inferred from neighbouring sites
  *wR*(*F*^2^) = 0.095                  H-atom parameters constrained
  *S* = 0.95                            *w* = 1/\[σ^2^(*F*~o~^2^) + (0.0433*P*)^2^\] where *P* = (*F*~o~^2^ + 2*F*~c~^2^)/3
  3275 reflections                      (Δ/σ)~max~ = 0.001
  172 parameters                        Δρ~max~ = 0.27 e Å^−3^
  0 restraints                          Δρ~min~ = −0.23 e Å^−3^
  ------------------------------------- -------------------------------------------------------------------------------------

Special details {#specialdetails}
===============

  -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  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 *F*^2^ against ALL reflections. The weighted *R*-factor *wR* and goodness of fit *S* are based on *F*^2^, conventional *R*-factors *R* are based on *F*, with *F* set to zero for negative *F*^2^. The threshold expression of *F*^2^ \> σ(*F*^2^) is used only for calculating *R*-factors(gt) *etc*. and is not relevant to the choice of reflections for refinement. *R*-factors based on *F*^2^ 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 (Å^2^) {#tablewrapcoords}
==================================================================================================

  ----- -------------- -------------- -------------- -------------------- --
        *x*            *y*            *z*            *U*~iso~\*/*U*~eq~   
  C1    0.2600 (3)     1.08679 (18)   0.14549 (10)   0.0258 (3)           
  C2    0.4977 (3)     1.05027 (18)   0.15814 (10)   0.0262 (3)           
  H2    0.6045         1.0856         0.1098         0.031\*              
  C3    0.5676 (2)     0.96086 (18)   0.24396 (10)   0.0233 (3)           
  H3    0.7248         0.9314         0.2563         0.028\*              
  C4    0.3929 (2)     0.91394 (16)   0.31412 (10)   0.0183 (3)           
  C5    0.2554 (2)     0.78257 (18)   0.47211 (9)    0.0191 (3)           
  H5A   0.2447         0.6710         0.4565         0.023\*              
  H5B   0.1066         0.8639         0.4613         0.023\*              
  C6    0.2997 (2)     0.77262 (18)   0.57925 (10)   0.0201 (3)           
  H6A   0.2902         0.8869         0.5973         0.024\*              
  H6B   0.1795         0.7281         0.6206         0.024\*              
  C7    0.7198 (2)     0.71363 (18)   0.53092 (9)    0.0195 (3)           
  H7A   0.8676         0.6312         0.5417         0.023\*              
  H7B   0.7325         0.8246         0.5467         0.023\*              
  C8    0.6760 (2)     0.72468 (17)   0.42325 (10)   0.0191 (3)           
  H8A   0.7957         0.7701         0.3822         0.023\*              
  H8B   0.6860         0.6107         0.4047         0.023\*              
  C9    0.5772 (2)     0.58513 (17)   0.69070 (10)   0.0195 (3)           
  C10   0.3966 (3)     0.57581 (19)   0.76644 (11)   0.0273 (3)           
  H10   0.2411         0.6307         0.7571         0.033\*              
  C11   0.4545 (3)     0.4840 (2)     0.85437 (11)   0.0326 (4)           
  H11   0.3373         0.4754         0.9052         0.039\*              
  C12   0.6857 (3)     0.4044 (2)     0.86779 (11)   0.0335 (4)           
  H12   0.7277         0.3393         0.9263         0.040\*              
  C13   0.8513 (3)     0.4253 (2)     0.79115 (11)   0.0317 (4)           
  H13   1.0080         0.3743         0.8002         0.038\*              
  Cl1   0.15611 (8)    1.19962 (6)    0.03723 (3)    0.04376 (16)         
  N1    0.1002 (2)     1.04206 (16)   0.21036 (9)    0.0273 (3)           
  N2    0.1664 (2)     0.95301 (15)   0.29644 (8)    0.0240 (3)           
  N3    0.44321 (19)   0.83591 (14)   0.40660 (8)    0.0185 (3)           
  N4    0.53064 (19)   0.66186 (14)   0.59658 (8)    0.0190 (3)           
  N5    0.8031 (2)     0.51407 (15)   0.70410 (9)    0.0259 (3)           
  ----- -------------- -------------- -------------- -------------------- --

Atomic displacement parameters (Å^2^) {#tablewrapadps}
=====================================

  ----- ------------- ------------ ------------ ------------- --------------- --------------
        *U*^11^       *U*^22^      *U*^33^      *U*^12^       *U*^13^         *U*^23^
  C1    0.0272 (8)    0.0267 (8)   0.0218 (7)   −0.0052 (6)   −0.0029 (6)     0.0016 (6)
  C2    0.0253 (8)    0.0305 (8)   0.0236 (7)   −0.0119 (7)   0.0053 (6)      −0.0019 (6)
  C3    0.0171 (7)    0.0278 (8)   0.0256 (7)   −0.0084 (6)   0.0024 (6)      −0.0035 (6)
  C4    0.0171 (7)    0.0169 (7)   0.0215 (7)   −0.0052 (5)   0.0011 (5)      −0.0050 (5)
  C5    0.0120 (7)    0.0230 (7)   0.0219 (7)   −0.0054 (6)   0.0007 (5)      −0.0006 (5)
  C6    0.0129 (7)    0.0240 (7)   0.0220 (7)   −0.0033 (6)   0.0015 (5)      −0.0015 (6)
  C7    0.0121 (7)    0.0226 (7)   0.0239 (7)   −0.0057 (6)   −0.0001 (5)     −0.0010 (5)
  C8    0.0107 (7)    0.0217 (7)   0.0239 (7)   −0.0031 (5)   0.0017 (5)      −0.0028 (5)
  C9    0.0198 (7)    0.0182 (7)   0.0219 (7)   −0.0057 (6)   −0.0031 (6)     −0.0033 (5)
  C10   0.0208 (8)    0.0327 (8)   0.0262 (8)   −0.0048 (7)   −0.0005 (6)     0.0011 (6)
  C11   0.0320 (9)    0.0415 (9)   0.0236 (8)   −0.0123 (8)   0.0016 (7)      0.0023 (7)
  C12   0.0369 (10)   0.0389 (9)   0.0240 (8)   −0.0077 (8)   −0.0103 (7)     0.0045 (7)
  C13   0.0246 (9)    0.0378 (9)   0.0314 (8)   −0.0030 (7)   −0.0101 (7)     0.0000 (7)
  Cl1   0.0423 (3)    0.0562 (3)   0.0281 (2)   −0.0095 (2)   −0.00750 (18)   0.01386 (18)
  N1    0.0230 (7)    0.0329 (7)   0.0246 (6)   −0.0060 (6)   −0.0038 (5)     0.0034 (5)
  N2    0.0166 (6)    0.0297 (7)   0.0242 (6)   −0.0054 (5)   −0.0023 (5)     0.0033 (5)
  N3    0.0115 (6)    0.0229 (6)   0.0198 (6)   −0.0039 (5)   0.0009 (4)      0.0001 (5)
  N4    0.0119 (6)    0.0230 (6)   0.0209 (6)   −0.0042 (5)   0.0003 (5)      0.0007 (5)
  N5    0.0201 (7)    0.0307 (7)   0.0259 (7)   −0.0037 (5)   −0.0052 (5)     −0.0014 (5)
  ----- ------------- ------------ ------------ ------------- --------------- --------------

Geometric parameters (Å, °) {#tablewrapgeomlong}
===========================

  ----------------------- -------------- --------------------- --------------
  C1---N1                 1.3071 (19)    C7---H7A              0.9700
  C1---C2                 1.388 (2)      C7---H7B              0.9700
  C1---Cl1                1.7401 (16)    C8---N3               1.4661 (18)
  C2---C3                 1.3574 (19)    C8---H8A              0.9700
  C2---H2                 0.9300         C8---H8B              0.9700
  C3---C4                 1.4170 (18)    C9---N5               1.3377 (18)
  C3---H3                 0.9300         C9---N4               1.3909 (17)
  C4---N2                 1.3401 (18)    C9---C10              1.405 (2)
  C4---N3                 1.3784 (17)    C10---C11             1.372 (2)
  C5---N3                 1.4617 (17)    C10---H10             0.9300
  C5---C6                 1.5104 (19)    C11---C12             1.378 (2)
  C5---H5A                0.9700         C11---H11             0.9300
  C5---H5B                0.9700         C12---C13             1.372 (2)
  C6---N4                 1.4582 (18)    C12---H12             0.9300
  C6---H6A                0.9700         C13---N5              1.3402 (18)
  C6---H6B                0.9700         C13---H13             0.9300
  C7---N4                 1.4635 (17)    N1---N2               1.3534 (16)
  C7---C8                 1.5159 (19)                          
                                                               
  N1---C1---C2            124.64 (13)    N3---C8---C7          110.54 (11)
  N1---C1---Cl1           115.24 (12)    N3---C8---H8A         109.5
  C2---C1---Cl1           120.12 (11)    C7---C8---H8A         109.5
  C3---C2---C1            117.20 (13)    N3---C8---H8B         109.5
  C3---C2---H2            121.4          C7---C8---H8B         109.5
  C1---C2---H2            121.4          H8A---C8---H8B        108.1
  C2---C3---C4            117.76 (14)    N5---C9---N4          116.30 (12)
  C2---C3---H3            121.1          N5---C9---C10         121.67 (13)
  C4---C3---H3            121.1          N4---C9---C10         121.97 (13)
  N2---C4---N3            116.16 (11)    C11---C10---C9        118.58 (14)
  N2---C4---C3            121.66 (12)    C11---C10---H10       120.7
  N3---C4---C3            122.04 (13)    C9---C10---H10        120.7
  N3---C5---C6            111.31 (11)    C10---C11---C12       120.29 (14)
  N3---C5---H5A           109.4          C10---C11---H11       119.9
  C6---C5---H5A           109.4          C12---C11---H11       119.9
  N3---C5---H5B           109.4          C13---C12---C11       117.17 (14)
  C6---C5---H5B           109.4          C13---C12---H12       121.4
  H5A---C5---H5B          108.0          C11---C12---H12       121.4
  N4---C6---C5            110.91 (11)    N5---C13---C12        124.63 (14)
  N4---C6---H6A           109.5          N5---C13---H13        117.7
  C5---C6---H6A           109.5          C12---C13---H13       117.7
  N4---C6---H6B           109.5          C1---N1---N2          119.04 (12)
  C5---C6---H6B           109.5          C4---N2---N1          119.68 (11)
  H6A---C6---H6B          108.0          C4---N3---C5          118.35 (11)
  N4---C7---C8            111.62 (11)    C4---N3---C8          121.18 (11)
  N4---C7---H7A           109.3          C5---N3---C8          112.41 (11)
  C8---C7---H7A           109.3          C9---N4---C6          120.47 (11)
  N4---C7---H7B           109.3          C9---N4---C7          118.98 (11)
  C8---C7---H7B           109.3          C6---N4---C7          112.49 (11)
  H7A---C7---H7B          108.0          C9---N5---C13         117.56 (12)
                                                               
  N1---C1---C2---C3       0.4 (2)        C3---C4---N3---C5     −176.37 (12)
  Cl1---C1---C2---C3      −179.57 (11)   N2---C4---N3---C8     154.15 (12)
  C1---C2---C3---C4       −0.8 (2)       C3---C4---N3---C8     −30.0 (2)
  C2---C3---C4---N2       1.2 (2)        C6---C5---N3---C4     −155.41 (12)
  C2---C3---C4---N3       −174.44 (13)   C6---C5---N3---C8     55.41 (15)
  N3---C5---C6---N4       −54.49 (15)    C7---C8---N3---C4     157.23 (12)
  N4---C7---C8---N3       53.56 (15)     C7---C8---N3---C5     −54.57 (15)
  N5---C9---C10---C11     −3.3 (2)       N5---C9---N4---C6     −167.32 (12)
  N4---C9---C10---C11     173.85 (13)    C10---C9---N4---C6    15.4 (2)
  C9---C10---C11---C12    0.6 (2)        N5---C9---N4---C7     −20.90 (18)
  C10---C11---C12---C13   1.6 (3)        C10---C9---N4---C7    161.84 (13)
  C11---C12---C13---N5    −1.5 (3)       C5---C6---N4---C9     −156.99 (12)
  C2---C1---N1---N2       −0.3 (2)       C5---C6---N4---C7     54.58 (15)
  Cl1---C1---N1---N2      179.64 (10)    C8---C7---N4---C9     156.51 (12)
  N3---C4---N2---N1       174.73 (12)    C8---C7---N4---C6     −54.56 (15)
  C3---C4---N2---N1       −1.2 (2)       N4---C9---N5---C13    −173.88 (13)
  C1---N1---N2---C4       0.7 (2)        C10---C9---N5---C13   3.4 (2)
  N2---C4---N3---C5       7.76 (18)      C12---C13---N5---C9   −1.0 (2)
  ----------------------- -------------- --------------------- --------------

Hydrogen-bond geometry (Å, °) {#tablewraphbondslong}
=============================

  ----------------- --------- --------- ----------- ---------------
  *D*---H···*A*     *D*---H   H···*A*   *D*···*A*   *D*---H···*A*
  C3---H3···N1^i^   0.93      2.58      3.346 (3)   140
  ----------------- --------- --------- ----------- ---------------

Symmetry codes: (i) *x*+1, *y*, *z*.

###### Hydrogen-bond geometry (Å, °)

  *D*---H⋯*A*     *D*---H   H⋯*A*   *D*⋯*A*     *D*---H⋯*A*
  --------------- --------- ------- ----------- -------------
  C3---H3⋯N1^i^   0.93      2.58    3.346 (3)   140

Symmetry code: (i) .
