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

For the structural and magnetic properties of transition metal complexes involving a pyridine or a substituted pyridine ligand, see: Crawford & Hatfield (1977[@bb3]); Marsh *et al.* (1981[@bb4]); Swank & Willett (1980[@bb7]). For Ni---O and Ni---N bond lengths, see: Bentiss *et al.* (2002[@bb1]); Rodopoulos *et al.* (2001[@bb5]).

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

 {#sec2.1}

### Crystal data {#sec2.1.1}

\[Ni(C~2~Cl~3~O~2~)~2~(C~5~H~5~N)~4~\]*M* *~r~* = 699.85Monoclinic,*a* = 9.1073 (18) Å*b* = 17.078 (3) Å*c* = 19.376 (6) Åβ = 106.94 (3)°*V* = 2882.9 (12) Å^3^*Z* = 4Mo *K*α radiationμ = 1.27 mm^−1^*T* = 293 K0.30 × 0.20 × 0.10 mm

### Data collection {#sec2.1.2}

Bruker SMART CCD area-detector diffractometerAbsorption correction: none13819 measured reflections3312 independent reflections2898 reflections with *I* \> 2σ(*I*)*R* ~int~ = 0.054

### Refinement {#sec2.1.3}

*R*\[*F* ^2^ \> 2σ(*F* ^2^)\] = 0.064*wR*(*F* ^2^) = 0.187*S* = 1.073312 reflections177 parametersH-atom parameters constrainedΔρ~max~ = 1.63 e Å^−3^Δρ~min~ = −1.04 e Å^−3^

 {#d5e463}

Data collection: *SMART* (Bruker, 1997[@bb2]); cell refinement: *SAINT* (Bruker, 1997[@bb2]); data reduction: *SAINT*; program(s) used to solve structure: *SHELXS97* (Sheldrick, 2008[@bb6]); program(s) used to refine structure: *SHELXL97* (Sheldrick, 2008[@bb6]); molecular graphics: *SHELXTL* (Sheldrick, 2008[@bb6]); software used to prepare material for publication: *SHELXTL*.

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

Crystal structure: contains datablocks global, I. DOI: [10.1107/S1600536809030025/at2853sup1.cif](http://dx.doi.org/10.1107/S1600536809030025/at2853sup1.cif)

Structure factors: contains datablocks I. DOI: [10.1107/S1600536809030025/at2853Isup2.hkl](http://dx.doi.org/10.1107/S1600536809030025/at2853Isup2.hkl)

Additional supplementary materials: [crystallographic information](http://scripts.iucr.org/cgi-bin/sendsupfiles?at2853&file=at2853sup0.html&mime=text/html); [3D view](http://scripts.iucr.org/cgi-bin/sendcif?at2853sup1&Qmime=cif); [checkCIF report](http://scripts.iucr.org/cgi-bin/paper?at2853&checkcif=yes)

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: [AT2853](http://scripts.iucr.org/cgi-bin/sendsup?at2853)).

The authors thank the Natural Science Foundation of Shandong Province for support (No. Y2008B30).

Comment
=======

The structural and magnetic properties of transition metal complexes in the solid state have been the subjects of numerous recent publications. This is particularly true for the cases where *L* is pyridine or a substituted pyridine (Swank & Willett, 1980; Marsh *et al.*, 1981; Crawford & Hatfield, 1977). Much of this work has been concerned with the correlation of the structural properties of these complexes with their magnetic properties. In order to search for new complexes of this type, we synthesized the title compound and report its crystal structure here.

The title compound contains one nickel(II), four pyridine ligands and two trichloroacetic acid molecules. The coordination sphere of the nickel(II) ion is best described as a slightly distorted octahedron. The Ni---O and Ni---N bond lengths are in agreement with those reported recently (Bentiss *et al.*, 2002; Rodopoulos *et al.*, 2001). The crystal packing is stabilized by C---H···O intra- and intermolecular hydrogen interaction (Table 1).

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

The title compound was obtained by adding pyridine (4 mmol) dropwise to a solution of nickel(II) trichloroacetic acid (1 mmol) in ethanol (30 ml) under stirred for 1 h at room temperature. A green solution was formed and after a few days block crystals precipitated.

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

H atoms were fixed geometrically and allowed to ride on their attached atoms, with C---H and N---H distances of 0.93--0.96 and 0.86 Å, and with *U*~iso~ = 1.2*U*~eq~.

Figures
=======

![The structure of the title compound showing 30% probability displacement ellipsoids and the atom-numbering scheme.](e-65-m1041-fig1){#Fap1}

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

  ---------------------------------------- ---------------------------------------
  \[Ni(C~2~Cl~3~O~2~)~2~(C~5~H~5~N)~4~\]   *F*(000) = 1416
  *M~r~* = 699.85                          *D*~x~ = 1.612 Mg m^−3^
  Monoclinic, *C*2/*c*                     Mo *K*α radiation, λ = 0.71073 Å
  Hall symbol: -C 2yc                      Cell parameters from 2898 reflections
  *a* = 9.1073 (18) Å                      θ = 3.1--27.5°
  *b* = 17.078 (3) Å                       µ = 1.27 mm^−1^
  *c* = 19.376 (6) Å                       *T* = 293 K
  β = 106.94 (3)°                          Block, green
  *V* = 2882.9 (12) Å^3^                   0.30 × 0.20 × 0.10 mm
  *Z* = 4                                  
  ---------------------------------------- ---------------------------------------

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

  ----------------------------------------------- --------------------------------------
  Bruker SMART CCD area-detector diffractometer   2898 reflections with *I* \> 2σ(*I*)
  Radiation source: fine-focus sealed tube        *R*~int~ = 0.054
  graphite                                        θ~max~ = 27.5°, θ~min~ = 3.1°
  φ and ω scans                                   *h* = −11→11
  13819 measured reflections                      *k* = −22→22
  3312 independent reflections                    *l* = −25→25
  ----------------------------------------------- --------------------------------------

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*\[*F*^2^ \> 2σ(*F*^2^)\] = 0.064   Hydrogen site location: inferred from neighbouring sites
  *wR*(*F*^2^) = 0.187                  H-atom parameters constrained
  *S* = 1.07                            *w* = 1/\[σ^2^(*F*~o~^2^) + (0.0862*P*)^2^ + 12.4612*P*\] where *P* = (*F*~o~^2^ + 2*F*~c~^2^)/3
  3312 reflections                      (Δ/σ)~max~ \< 0.001
  177 parameters                        Δρ~max~ = 1.63 e Å^−3^
  0 restraints                          Δρ~min~ = −1.04 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~   
  Ni     0.0000         0.03441 (4)     0.2500         0.0324 (2)           
  Cl1    0.1137 (2)     0.13260 (11)    0.03902 (9)    0.0835 (5)           
  Cl2    0.3294 (2)     0.01282 (11)    0.02840 (8)    0.0816 (5)           
  Cl3    0.40222 (17)   0.11568 (9)     0.14971 (9)    0.0755 (4)           
  O1     0.2031 (5)     −0.0615 (2)     0.1326 (2)     0.0663 (10)          
  O2     0.1059 (4)     0.04555 (17)    0.16902 (15)   0.0444 (7)           
  N2     −0.1503 (4)    0.12325 (18)    0.19207 (16)   0.0366 (7)           
  N1     0.1589 (4)     −0.05134 (18)   0.30435 (17)   0.0369 (7)           
  C1     0.2501 (5)     0.0635 (3)      0.0878 (2)     0.0467 (9)           
  C3B    −0.3058 (6)    0.2490 (3)      0.1124 (3)     0.0587 (12)          
  H3BA   −0.3558        0.2915          0.0857         0.070\*              
  C2A    0.2185 (6)     −0.1699 (3)     0.3717 (3)     0.0556 (11)          
  H2AA   0.1850         −0.2112         0.3946         0.067\*              
  C3A    0.3683 (6)     −0.1660 (3)     0.3713 (3)     0.0603 (12)          
  H3AA   0.4381         −0.2046         0.3936         0.072\*              
  C2     0.1764 (4)     0.0082 (3)      0.1343 (2)     0.0406 (8)           
  C4B    −0.2629 (6)    0.2506 (3)      0.1859 (3)     0.0565 (12)          
  H4BA   −0.2852        0.2940          0.2101         0.068\*              
  C4A    0.4137 (5)     −0.1035 (3)     0.3372 (3)     0.0575 (12)          
  H4AA   0.5147         −0.0992         0.3360         0.069\*              
  C2B    −0.2737 (6)    0.1829 (3)      0.0785 (3)     0.0565 (11)          
  H2BA   −0.3042        0.1796          0.0284         0.068\*              
  C5B    −0.1861 (5)    0.1875 (3)      0.2240 (2)     0.0458 (9)           
  H5BA   −0.1577        0.1894          0.2741         0.055\*              
  C5A    0.3063 (5)     −0.0477 (3)     0.3048 (3)     0.0482 (10)          
  H5AA   0.3376         −0.0055         0.2823         0.058\*              
  C1B    −0.1961 (5)    0.1222 (3)      0.1197 (2)     0.0445 (9)           
  H1BA   −0.1742        0.0781          0.0963         0.053\*              
  C1A    0.1178 (5)     −0.1121 (2)     0.3380 (2)     0.0452 (9)           
  H1AA   0.0162         −0.1155         0.3386         0.054\*              
  ------ -------------- --------------- -------------- -------------------- --

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

  ----- ------------- ------------- ------------- -------------- ------------- --------------
        *U*^11^       *U*^22^       *U*^33^       *U*^12^        *U*^13^       *U*^23^
  Ni    0.0382 (4)    0.0279 (3)    0.0332 (3)    0.000          0.0136 (3)    0.000
  Cl1   0.0853 (10)   0.0995 (12)   0.0730 (9)    0.0308 (9)     0.0347 (8)    0.0410 (8)
  Cl2   0.0984 (11)   0.0965 (11)   0.0680 (8)    0.0099 (9)     0.0529 (8)    −0.0121 (8)
  Cl3   0.0637 (8)    0.0730 (9)    0.0956 (11)   −0.0224 (7)    0.0323 (7)    −0.0145 (8)
  O1    0.070 (2)     0.0427 (17)   0.100 (3)     −0.0004 (16)   0.047 (2)     −0.0027 (18)
  O2    0.0524 (16)   0.0448 (16)   0.0427 (15)   0.0042 (13)    0.0245 (13)   0.0029 (12)
  N2    0.0428 (17)   0.0319 (15)   0.0361 (15)   0.0023 (13)    0.0130 (13)   0.0004 (12)
  N1    0.0396 (16)   0.0324 (15)   0.0386 (16)   0.0006 (12)    0.0114 (13)   0.0020 (12)
  C1    0.051 (2)     0.050 (2)     0.045 (2)     0.0052 (19)    0.0234 (18)   0.0020 (18)
  C3B   0.060 (3)     0.046 (2)     0.067 (3)     0.009 (2)      0.014 (2)     0.015 (2)
  C2A   0.067 (3)     0.045 (2)     0.057 (3)     0.009 (2)      0.020 (2)     0.011 (2)
  C3A   0.059 (3)     0.057 (3)     0.059 (3)     0.018 (2)      0.008 (2)     0.006 (2)
  C2    0.0380 (19)   0.044 (2)     0.042 (2)     −0.0003 (16)   0.0146 (16)   0.0001 (16)
  C4B   0.066 (3)     0.036 (2)     0.068 (3)     0.011 (2)      0.020 (2)     −0.002 (2)
  C4A   0.038 (2)     0.064 (3)     0.067 (3)     0.003 (2)      0.010 (2)     0.003 (2)
  C2B   0.057 (3)     0.066 (3)     0.044 (2)     0.007 (2)      0.0107 (19)   0.009 (2)
  C5B   0.051 (2)     0.041 (2)     0.047 (2)     0.0073 (18)    0.0161 (18)   −0.0020 (17)
  C5A   0.040 (2)     0.049 (2)     0.055 (2)     −0.0046 (17)   0.0125 (18)   0.0059 (19)
  C1B   0.053 (2)     0.043 (2)     0.0371 (19)   0.0042 (18)    0.0130 (17)   −0.0007 (16)
  C1A   0.047 (2)     0.040 (2)     0.052 (2)     0.0021 (17)    0.0204 (18)   0.0031 (18)
  ----- ------------- ------------- ------------- -------------- ------------- --------------

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

  ----------------------- ------------- ----------------------- ------------
  Ni---O2                 2.076 (3)     C3B---C2B               1.379 (7)
  Ni---O2^i^              2.076 (3)     C3B---H3BA              0.9300
  Ni---N1^i^              2.112 (3)     C2A---C3A               1.368 (8)
  Ni---N1                 2.112 (3)     C2A---C1A               1.377 (6)
  Ni---N2^i^              2.131 (3)     C2A---H2AA              0.9300
  Ni---N2                 2.131 (3)     C3A---C4A               1.381 (8)
  Cl1---C1                1.773 (5)     C3A---H3AA              0.9300
  Cl2---C1                1.754 (4)     C4B---C5B               1.377 (6)
  Cl3---C1                1.784 (5)     C4B---H4BA              0.9300
  O1---C2                 1.217 (5)     C4A---C5A               1.378 (7)
  O2---C2                 1.234 (5)     C4A---H4AA              0.9300
  N2---C1B                1.341 (5)     C2B---C1B               1.373 (6)
  N2---C5B                1.346 (5)     C2B---H2BA              0.9300
  N1---C1A                1.335 (5)     C5B---H5BA              0.9300
  N1---C5A                1.342 (5)     C5A---H5AA              0.9300
  C1---C2                 1.585 (6)     C1B---H1BA              0.9300
  C3B---C4B               1.362 (8)     C1A---H1AA              0.9300
                                                                
  O2---Ni---O2^i^         169.48 (17)   C3A---C2A---C1A         119.3 (5)
  O2---Ni---N1^i^         95.06 (13)    C3A---C2A---H2AA        120.3
  O2^i^---Ni---N1^i^      92.23 (12)    C1A---C2A---H2AA        120.3
  O2---Ni---N1            92.23 (12)    C2A---C3A---C4A         118.6 (4)
  O2^i^---Ni---N1         95.06 (13)    C2A---C3A---H3AA        120.7
  N1^i^---Ni---N1         92.18 (18)    C4A---C3A---H3AA        120.7
  O2---Ni---N2^i^         87.95 (12)    O1---C2---O2            131.3 (4)
  O2^i^---Ni---N2^i^      84.56 (12)    O1---C2---C1            116.6 (4)
  N1^i^---Ni---N2^i^      176.54 (12)   O2---C2---C1            112.1 (4)
  N1---Ni---N2^i^         89.39 (13)    C3B---C4B---C5B         119.4 (4)
  O2---Ni---N2            84.56 (12)    C3B---C4B---H4BA        120.3
  O2^i^---Ni---N2         87.95 (12)    C5B---C4B---H4BA        120.3
  N1^i^---Ni---N2         89.39 (13)    C5A---C4A---C3A         118.7 (4)
  N1---Ni---N2            176.54 (12)   C5A---C4A---H4AA        120.6
  N2^i^---Ni---N2         89.20 (17)    C3A---C4A---H4AA        120.6
  C2---O2---Ni            142.6 (3)     C1B---C2B---C3B         119.0 (4)
  C1B---N2---C5B          116.7 (3)     C1B---C2B---H2BA        120.5
  C1B---N2---Ni           119.8 (3)     C3B---C2B---H2BA        120.5
  C5B---N2---Ni           122.9 (3)     N2---C5B---C4B          123.0 (4)
  C1A---N1---C5A          117.1 (4)     N2---C5B---H5BA         118.5
  C1A---N1---Ni           122.2 (3)     C4B---C5B---H5BA        118.5
  C5A---N1---Ni           120.7 (3)     N1---C5A---C4A          123.2 (4)
  C2---C1---Cl2           113.7 (3)     N1---C5A---H5AA         118.4
  C2---C1---Cl1           110.6 (3)     C4A---C5A---H5AA        118.4
  Cl2---C1---Cl1          109.7 (2)     N2---C1B---C2B          123.3 (4)
  C2---C1---Cl3           106.8 (3)     N2---C1B---H1BA         118.4
  Cl2---C1---Cl3          107.5 (2)     C2B---C1B---H1BA        118.4
  Cl1---C1---Cl3          108.2 (3)     N1---C1A---C2A          123.2 (4)
  C4B---C3B---C2B         118.6 (4)     N1---C1A---H1AA         118.4
  C4B---C3B---H3BA        120.7         C2A---C1A---H1AA        118.4
  C2B---C3B---H3BA        120.7                                 
                                                                
  O2^i^---Ni---O2---C2    167.2 (5)     Ni---O2---C2---C1       −169.6 (3)
  N1^i^---Ni---O2---C2    −59.1 (5)     Cl2---C1---C2---O1      11.1 (5)
  N1---Ni---O2---C2       33.3 (5)      Cl1---C1---C2---O1      135.1 (4)
  N2^i^---Ni---O2---C2    122.6 (5)     Cl3---C1---C2---O1      −107.3 (4)
  N2---Ni---O2---C2       −148.0 (5)    Cl2---C1---C2---O2      −171.9 (3)
  O2---Ni---N2---C1B      39.1 (3)      Cl1---C1---C2---O2      −47.9 (4)
  O2^i^---Ni---N2---C1B   −148.3 (3)    Cl3---C1---C2---O2      69.7 (4)
  N1^i^---Ni---N2---C1B   −56.0 (3)     C2B---C3B---C4B---C5B   1.4 (8)
  N2^i^---Ni---N2---C1B   127.1 (3)     C2A---C3A---C4A---C5A   0.0 (8)
  O2---Ni---N2---C5B      −131.3 (3)    C4B---C3B---C2B---C1B   −1.8 (8)
  O2^i^---Ni---N2---C5B   41.3 (3)      C1B---N2---C5B---C4B    −1.3 (6)
  N1^i^---Ni---N2---C5B   133.5 (3)     Ni---N2---C5B---C4B     169.4 (4)
  N2^i^---Ni---N2---C5B   −43.3 (3)     C3B---C4B---C5B---N2    0.2 (8)
  O2---Ni---N1---C1A      −143.2 (3)    C1A---N1---C5A---C4A    0.9 (7)
  O2^i^---Ni---N1---C1A   44.4 (3)      Ni---N1---C5A---C4A     −177.6 (4)
  N1^i^---Ni---N1---C1A   −48.1 (3)     C3A---C4A---C5A---N1    −0.6 (8)
  N2^i^---Ni---N1---C1A   128.8 (3)     C5B---N2---C1B---C2B    0.9 (6)
  O2---Ni---N1---C5A      35.1 (3)      Ni---N2---C1B---C2B     −170.1 (4)
  O2^i^---Ni---N1---C5A   −137.3 (3)    C3B---C2B---C1B---N2    0.6 (8)
  N1^i^---Ni---N1---C5A   130.3 (4)     C5A---N1---C1A---C2A    −0.5 (6)
  N2^i^---Ni---N1---C5A   −52.8 (3)     Ni---N1---C1A---C2A     177.9 (4)
  C1A---C2A---C3A---C4A   0.3 (8)       C3A---C2A---C1A---N1    −0.1 (7)
  Ni---O2---C2---O1       6.8 (8)                               
  ----------------------- ------------- ----------------------- ------------

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

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

  ---------------------- --------- --------- ----------- ---------------
  *D*---H···*A*          *D*---H   H···*A*   *D*···*A*   *D*---H···*A*
  C4A---H4AA···O1^ii^    0.93      2.55      3.442 (7)   162
  C1B---H1BA···O2        0.93      2.59      2.943 (6)   103
  C1A---H1AA···O1^iii^   0.93      2.41      3.253 (7)   151
  ---------------------- --------- --------- ----------- ---------------

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

###### Hydrogen-bond geometry (Å, °)

  *D*---H⋯*A*             *D*---H   H⋯*A*   *D*⋯*A*     *D*---H⋯*A*
  ----------------------- --------- ------- ----------- -------------
  C4*A*---H4*AA*⋯O1^i^    0.93      2.55    3.442 (7)   162
  C1*B*---H1*BA*⋯O2       0.93      2.59    2.943 (6)   103
  C1*A*---H1*AA*⋯O1^ii^   0.93      2.41    3.253 (7)   151

Symmetry codes: (i) ; (ii) .
