Poly[(μ₆-4-amino-3,5,6-trichloro­pyridine-2-carboxyl­ato)aqua­caesium]

In the structure of the title complex, [Cs(C₆H₂Cl₃N₂O₂)(H₂O)]_n, the caesium salt of the commercial herbicide picloram, the Cs⁺ cation lies on a crystallographic mirror plane, which also contains the coordinating water mol­ecule and all non-H atoms of the 4-amino-3,5,6-trichloro­picolinate anion except the carboxyl­ate O-atom donors. The irregular CsCl₄O₅ coordination polyhedron comprises chlorine donors from the ortho-related ring substituents of the picloramate ligand in a bidentate chelate mode, with a third chlorine bridging [Cs—Cl range 3.6052 (11)–3.7151 (11) Å] as well as a bidentate chelate carboxyl­ate group giving sheets extending parallel to (010). A three-dimensional coordination polymer structure is generated through the carboxyl­ate group, which also bridges the sheets down [010]. Within the structure, there are intra-unit water O—H...O_{carboxyl­ate} and amine N—H...N_pyridine hydrogen-bonding inter­actions.

Key indicators

• Single-crystal X-ray study
• T = 200 K
• Mean [sigma](C-C) = 0.005 Å
• R factor = 0.021
• wR factor = 0.053
• Data-to-parameter ratio = 13.1

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT352_ALERT_3_C Short   N-H Bond (0.87A)   N4     -   H41    ...       0.73 Ang.
PLAT774_ALERT_1_C Suspect X-Y Bond in CIF:   CS1    --  CL5     ..       3.72 Ang.
PLAT774_ALERT_1_C Suspect X-Y Bond in CIF:   CS1    --  CL6     ..       3.61 Ang.
PLAT774_ALERT_1_C Suspect X-Y Bond in CIF:   CS1    --  CL3     ..       3.71 Ang.
PLAT774_ALERT_1_C Suspect X-Y Bond in CIF:   CS1    --  CL3     ..       3.71 Ang.
PLAT910_ALERT_3_C Missing # of FCF Reflections Below Th(Min) .....          3
PLAT976_ALERT_2_C Negative Residual Density at 0.87A from N4     .      -0.51 eA-3
PLAT976_ALERT_2_C Negative Residual Density at 0.94A from N4     .      -0.47 eA-3
PLAT976_ALERT_2_C Negative Residual Density at 1.05A from O1W    .      -0.45 eA-3

Alert level G
PLAT004_ALERT_5_G Info: Polymeric Structure Found with Dimension .          3
PLAT005_ALERT_5_G No _iucr_refine_instructions_details  in the CIF          ?
PLAT007_ALERT_5_G Note: Number of Unrefined D-H Atoms ............          3

   0 ALERT level A = Most likely a serious problem - resolve or explain
   0 ALERT level B = A potentially serious problem, consider carefully
   9 ALERT level C = Check. Ensure it is not caused by an omission or oversight
   3 ALERT level G = General information/check it is not something unexpected

   4 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   3 ALERT type 2 Indicator that the structure model may be wrong or deficient
   2 ALERT type 3 Indicator that the structure quality may be low
   0 ALERT type 4 Improvement, methodology, query or suggestion
   3 ALERT type 5 Informative message, check

---

S1. Comment

4-Amino-3,5,6-trichloropyridine-2-carboxylic acid (picloram) is a commercial herbicide (Mullinson, 1985) introduced by Dow Chemicals as Tordon (O'Neil, 2001). Although it has potential as a metal chelating ligand similar to picolinic acid, there are only five metal complexes with picloramato ligands in the crystallographic literature. Examples include picloram as a bidentate chelate ligand [with Mn^II (Smith et al., 1981a) and Cu^II (O'Reilly et al., 1983)], while in the Mg complex (Smith et al., 1981b], picloram acts as a counter-anion. A caesium complex derived from dipicolinic acid has also been reported (Santra et al., 2011).

The reaction of picloram with caesium hydroxide in aqueous ethanol gave crystals of the title compound [Cs(C₆H₂Cl₃N₂O₂)(H₂O)]_n and the structure is reported herein. In this structure, the Cs⁺ cation lies on a crystallographic mirror plane which also contains the coordinating monodentate water molecule and all non-H atoms of the picloramate ligand except the carboxyl O-atom donors (Fig. 1). The irregular CsCl₄O₅ coordination sphere comprises chlorine donors from the ortho-related ring substituents (Cl5, Cl6) in a bidentate chelate mode [Cs—Cl, 3.6052 (11), 3.7151 (11) Å], with the third chlorine (Cl3) [Cs—Cl, 3.7127 (4) Å] bridging neighbouring Cs⁺ cations [Cs···Cs^x, Cs···Cs^xi = 4.9008 (3) Å] [for (x), -x + 1, y - 1/2, -z + 2; for (xi), -x + 1, y + 1/2, -z + 2], as well as a bidentate chelate and bridging carboxyl group. Although in most structures containing caesium and related ligands, the Cl atom is anionic rather than coordinating, an example of a coordinating carbon-bound Cl is known in which 1,2-dichloroethane acts as a bidentate chelate ligand (Levitskaia et al., 2000). The Cs—Cl bond lengths in that structure are shorter than those in the title complex (3.46–3.56 Å).

In the present complex, sheets are formed parallel to (010) (Fig. 2) and these are extended into a three-dimensional coordination polymer structure through the carboxyl group of the picloram ligand which bridges the sheets down [010] (Fig. 3). The amine group gives weak intramolecular N—H···Cl5 and ···Cl6 interactions and as well forms inter-complex N—H···N_pyridine hydrogen bonds which accompany water O—H···O_carboxyl hydrogen-bonding interactions in the structure (Table 2).

Related literature

For background information on picloram, see: Mullinson (1985); O'Neil (2001). For examples of structures of metal complexes with picloram, see: Smith et al. (1981a,b); O'Reilly et al. (1983). For another structure with caesium cations involving coordinating carbon-bound Cl, see: Levitskaia et al. (2000). For a caesium complex with dipicolinic acid, see: Santra et al. (2011).

S2. Experimental

The title compound was synthesized by heating together under reflux for 10 minutes, 0.5 mmol of caesium hydroxide and 0.5 mmol of 4-amino-3,5,6-trichloropicolinic acid in 20 ml of 10% ethanol–water. Room temperature evaporation of the solution to incipient dryness gave colourless crystal plates of the title complex from which a specimen was cleaved for the X-ray analysis.

S3. Refinement

Hydrogen atoms of the coordinating water molecule and the amine group were located in a difference-Fourier synthesis but were allowed to ride in the refinement with U_iso(H) = 1.2U_eq(N) or 1.5U_eq(O).

Computing details

Data collection: CrysAlis PRO (Agilent, 2012); cell refinement: CrysAlis PRO (Agilent, 2012); data reduction: CrysAlis PRO (Agilent, 2012); program(s) used to solve structure: SIR92 (Altomare et al., 1993); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008) within WinGX (Farrugia, 2012); molecular graphics: PLATON (Spek, 2009); software used to prepare material for publication: PLATON (Spek, 2009).

Figures

	Fig. 1. The molecular configuration and atom-numbering scheme for the title compound, with non-H atoms drawn as 50% probability ellipsoids. For symmetry codes: see Table 1.
	Fig. 2. The sheet structure viewed perpendicular to the crystallographic mirror planes, with intermolecular hydrogen bonds and intramolecular N—H···Cl associations shown as dashed lines. For symmetry codes, see Fig. 1 and Table 1.
	Fig. 3. The packing in the unit cell viewed along the the mirror planes showing inter-plane carboxyl bridges and hydrogen-bonding associations (Table 2) as dashed lines.

Poly[(µ₆-4-amino-3,5,6-trichloropyridine-2-carboxylato)aquacaesium]

Crystal data

[Cs(C6H2Cl3N2O2)(H2O)]	F(000) = 368
Mr = 391.37	Dx = 2.382 Mg m^−3
Monoclinic, P21/m	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yb	Cell parameters from 3047 reflections
a = 7.0816 (3) Å	θ = 3.5–28.7°
b = 6.6863 (2) Å	µ = 4.11 mm^−1
c = 11.7382 (5) Å	T = 200 K
β = 101.005 (4)°	Plate, colourless
V = 545.58 (4) Å^3	0.25 × 0.20 × 0.08 mm
Z = 2

Data collection

Oxford Diffraction Gemini-S CCD detector diffractometer	1164 independent reflections
Radiation source: Enhance Mo X-ray source	1118 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.026
Detector resolution: 16.077 pixels mm^-1	θmax = 26.0°, θmin = 3.5°
ω scans	h = −8→7
Absorption correction: multi-scan (CrysAlis PRO; Agilent, 2012)	k = −8→8
Tmin = 0.67, Tmax = 0.98	l = −11→14
3773 measured reflections

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.021	H-atom parameters constrained
wR(F^2) = 0.053	w = 1/[σ^2(Fo^2) + (0.0338P)^2 + 0.1378P] where P = (Fo^2 + 2Fc^2)/3
S = 0.98	(Δ/σ)max = 0.001
1164 reflections	Δρmax = 0.55 e Å^−3
89 parameters	Δρmin = −0.56 e Å^−3
0 restraints	Extinction correction: SHELXL97 (Sheldrick, 2008) within WinGX (Farrugia, 2012), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0132 (11)

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
Cs1	0.29271 (3)	0.2500	0.885412 (19)	0.02831 (13)
Cl3	−0.06235 (13)	0.2500	0.12344 (9)	0.0326 (2)
Cl5	−0.01008 (14)	0.2500	0.58974 (9)	0.0291 (2)
Cl6	0.44747 (14)	0.2500	0.61009 (9)	0.0335 (2)
O1W	−0.1573 (4)	0.2500	0.8385 (3)	0.0433 (8)
H11W	−0.2387	0.1425	0.8335	0.065*
O21	0.4110 (3)	0.0836 (3)	0.14016 (17)	0.0369 (5)
N1	0.3823 (4)	0.2500	0.3865 (3)	0.0223 (6)
N4	−0.2153 (5)	0.2500	0.3441 (3)	0.0380 (8)
H41	−0.2870	0.2500	0.2908	0.046*
H42	−0.2700	0.2500	0.3968	0.046*
C2	0.2692 (5)	0.2500	0.2807 (3)	0.0211 (7)
C3	0.0719 (5)	0.2500	0.2649 (3)	0.0230 (7)
C4	−0.0239 (5)	0.2500	0.3586 (3)	0.0241 (8)
C5	0.0961 (5)	0.2500	0.4690 (3)	0.0224 (7)
C6	0.2937 (5)	0.2500	0.4763 (3)	0.0221 (7)
C21	0.3725 (5)	0.2500	0.1780 (3)	0.0253 (8)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cs1	0.02573 (17)	0.03285 (17)	0.02648 (18)	0.000	0.00536 (11)	0.000
Cl3	0.0204 (5)	0.0427 (5)	0.0316 (5)	0.000	−0.0029 (4)	0.000
Cl5	0.0277 (5)	0.0283 (5)	0.0359 (5)	0.000	0.0172 (4)	0.000
Cl6	0.0263 (5)	0.0492 (6)	0.0243 (5)	0.000	0.0034 (4)	0.000
O1W	0.0298 (16)	0.0423 (17)	0.056 (2)	0.000	0.0042 (15)	0.000
O21	0.0456 (12)	0.0340 (11)	0.0352 (12)	0.0137 (9)	0.0178 (10)	0.0035 (9)
N1	0.0173 (15)	0.0238 (15)	0.0266 (17)	0.000	0.0061 (12)	0.000
N4	0.0158 (16)	0.058 (2)	0.041 (2)	0.000	0.0076 (14)	0.000
C2	0.0187 (17)	0.0181 (16)	0.027 (2)	0.000	0.0048 (14)	0.000
C3	0.0169 (17)	0.0240 (17)	0.027 (2)	0.000	0.0008 (15)	0.000
C4	0.0164 (17)	0.0187 (16)	0.037 (2)	0.000	0.0052 (15)	0.000
C5	0.0198 (17)	0.0196 (16)	0.030 (2)	0.000	0.0116 (15)	0.000
C6	0.0194 (17)	0.0216 (16)	0.0243 (19)	0.000	0.0020 (14)	0.000
C21	0.0149 (16)	0.036 (2)	0.0238 (19)	0.000	0.0002 (14)	0.000

Geometric parameters (Å, º)

Cs1—Cl5	3.7151 (11)	O1W—H11W	0.9200
Cs1—Cl6	3.6052 (11)	O1W—H11W^vii	0.9200
Cs1—O1W	3.129 (3)	N1—C2	1.343 (5)
Cs1—O21^i	3.116 (2)	N1—C6	1.326 (5)
Cs1—O21^ii	3.116 (2)	N4—C4	1.333 (5)
Cs1—O21^iii	3.150 (2)	N4—H42	0.7900
Cs1—O21^iv	3.150 (2)	N4—H41	0.7300
Cs1—Cl3^v	3.7127 (4)	C2—C3	1.374 (5)
Cs1—Cl3^vi	3.7127 (4)	C2—C21	1.525 (5)
Cl5—C5	1.727 (4)	C3—C4	1.398 (5)
Cl6—C6	1.732 (4)	C3—Cl3	1.749 (4)
C21—O21	1.247 (3)	C4—C5	1.408 (5)
C21—O21^vii	1.247 (3)	C5—C6	1.386 (5)
Cl5—Cs1—Cl6	51.87 (2)	Cl3^vi—Cs1—O21^iii	75.19 (4)
Cl5—Cs1—O1W	56.55 (7)	O21^i—Cs1—O21^ii	91.43 (5)
Cl5—Cs1—O21^iv	152.65 (4)	O21^i—Cs1—O21^iii	77.10 (5)
Cl3^v—Cs1—Cl5	78.56 (2)	O21^ii—Cs1—O21^iii	106.40 (5)
Cl3^vi—Cs1—Cl5	78.56 (2)	Cs1^v—Cl3—C3	100.54 (5)
Cl5—Cs1—O21^i	100.91 (4)	Cs1^vi—Cl3—C3	100.54 (5)
Cl5—Cs1—O21^ii	100.91 (4)	Cs1^v—Cl3—Cs1^vi	128.44 (3)
Cl5—Cs1—O21^iii	152.65 (4)	Cs1—Cl5—C5	120.18 (13)
Cl6—Cs1—O1W	108.42 (7)	Cs1—Cl6—C6	124.53 (13)
Cl6—Cs1—O21^iv	141.22 (4)	Cs1^viii—O21—Cs1^ix	102.90 (6)
Cl3^v—Cs1—Cl6	100.49 (2)	Cs1—O1W—H11W	128.00
Cl3^vi—Cs1—Cl6	100.49 (2)	Cs1—O1W—H11W^vii	128.00
Cl6—Cs1—O21^i	65.68 (4)	H11W—O1W—H11W^vii	103.00
Cl6—Cs1—O21^ii	65.68 (4)	C2—N1—C6	116.5 (3)
Cl6—Cs1—O21^iii	141.22 (4)	C4—N4—H41	130.00
O1W—Cs1—O21^iv	104.15 (7)	H41—N4—H42	108.00
Cl3^v—Cs1—O1W	64.39 (1)	C4—N4—H42	123.00
Cl3^vi—Cs1—O1W	64.39 (1)	N1—C2—C21	116.1 (3)
O1W—Cs1—O21^i	131.69 (4)	N1—C2—C3	122.4 (3)
O1W—Cs1—O21^ii	131.69 (4)	C3—C2—C21	121.5 (3)
O1W—Cs1—O21^iii	104.15 (7)	C2—C3—C4	121.8 (3)
Cl3^v—Cs1—O21^iv	75.19 (4)	Cl3—C3—C2	118.9 (3)
Cl3^vi—Cs1—O21^iv	112.36 (4)	Cl3—C3—C4	119.3 (3)
O21^iv—Cs1—O21^i	106.40 (5)	N4—C4—C5	122.5 (3)
O21^iv—Cs1—O21^ii	77.10 (5)	C3—C4—C5	115.2 (3)
O21^iv—Cs1—O21^iii	41.36 (5)	N4—C4—C3	122.3 (3)
Cl3^v—Cs1—Cl3^vi	128.44 (2)	C4—C5—C6	118.8 (3)
Cl3^v—Cs1—O21^i	160.44 (4)	Cl5—C5—C4	118.4 (3)
Cl3^v—Cs1—O21^ii	69.70 (4)	Cl5—C5—C6	122.8 (3)
Cl3^v—Cs1—O21^iii	112.36 (4)	Cl6—C6—C5	120.6 (3)
Cl3^vi—Cs1—O21^i	69.70 (4)	Cl6—C6—N1	114.2 (3)
Cl3^vi—Cs1—O21^ii	160.44 (4)	N1—C6—C5	125.2 (3)
Cl6—Cs1—Cl5—C5	0.00 (1)	C21—C2—C3—C4	180.00 (1)
O1W—Cs1—Cl5—C5	180.00 (1)	N1—C2—C21—O21	89.9 (3)
Cl5—Cs1—Cl6—C6	0.00 (1)	C3—C2—C21—O21	−90.1 (3)
O1W—Cs1—Cl6—C6	0.00 (1)	Cl3—C3—C4—N4	0.00 (1)
Cs1—Cl5—C5—C4	180.00 (1)	Cl3—C3—C4—C5	180.00 (1)
Cs1—Cl5—C5—C6	0.00 (1)	C2—C3—C4—N4	180.00 (1)
Cs1—Cl6—C6—N1	180.00 (1)	C2—C3—C4—C5	0.00 (1)
Cs1—Cl6—C6—C5	0.00 (1)	N4—C4—C5—Cl5	0.00 (1)
C6—N1—C2—C3	0.00 (1)	N4—C4—C5—C6	180.00 (1)
C6—N1—C2—C21	180.00 (1)	C3—C4—C5—Cl5	180.00 (1)
C2—N1—C6—Cl6	180.00 (1)	C3—C4—C5—C6	0.00 (1)
C2—N1—C6—C5	0.00 (1)	Cl5—C5—C6—Cl6	0.00 (1)
N1—C2—C3—Cl3	180.00 (1)	Cl5—C5—C6—N1	180.00 (1)
N1—C2—C3—C4	0.00 (1)	C4—C5—C6—Cl6	180.00 (1)
C21—C2—C3—Cl3	0.00 (1)	C4—C5—C6—N1	0.00 (1)

Symmetry codes: (i) −x+1, y+1/2, −z+1; (ii) −x+1, −y, −z+1; (iii) x, −y+1/2, z+1; (iv) x, y, z+1; (v) −x, y−1/2, −z+1; (vi) −x, y+1/2, −z+1; (vii) x, −y+1/2, z; (viii) x, y, z−1; (ix) −x+1, y−1/2, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1W—H11W···O21^x	0.92	2.00	2.905 (3)	168
N4—H42···N1^xi	0.79	2.44	2.985 (5)	127
N4—H42···Cl5	0.79	2.63	2.971 (4)	108
N4—H41···Cl3	0.73	2.75	2.992 (4)	102

Symmetry codes: (x) −x, −y, −z+1; (xi) x−1, y, z.