4-(Dimethyl­amino)­pyridinium tetra­chloridoferrate(III)

The title salt, (C₇H₁₁N₂)[FeCl₄], consists of one essentially planar (the r.m.s. deviation for all non-H atoms being 0.004 Å) 4-(dimethyl­amino)­pyridinium cation and a tetra­hedral tetra­chloridoferrate(III) anion. The cations and anions are arranged in layers parallel to (010). Besides electrostatic inter­actions, the crystal packing features N—H...Cl and C—H...Cl hydrogen bonds between cations and anions, forming a three-dimensional network.

Key indicators

• Single-crystal X-ray study
• T = 100 K
• Mean [sigma](C-C) = 0.004 Å
• R factor = 0.034
• wR factor = 0.081
• Data-to-parameter ratio = 22.0

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT911_ALERT_3_C Missing # FCF Refl Between THmin & STh/L=  0.600          5

Alert level G
PLAT005_ALERT_5_G No _iucr_refine_instructions_details  in the CIF          ?
PLAT128_ALERT_4_G Alternate Setting of Space-group P21/c   .......      P21/n
PLAT794_ALERT_5_G Note: Tentative Bond Valency for Fe1     (III)         3.02
PLAT912_ALERT_4_G Missing # of FCF Reflections Above STh/L=  0.600         16

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

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

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S1. Comment

In the course of previuos studies on intermolecular hydrogen-bonding interactions in transition metal hybrid complexes with N-heterocyclic ligands (Bouacida, 2008; Bouacida et al., 2007, 2009), we report here on synthesis and structural characterization of a new organic/inorganic hybrid, involving Fe(III) and 4-(dimethylamino)pyridine, (C₇H₁₁N₂)^+.[FeCl₄]^-, (I). The molecular geometry of the constituents and the atom-numbering scheme of (I) are shown in Fig. 1.

The asymmetric unit of (I) consists of tetrahedral [FeCl₄]^- anions and one protoned 4-(dimethylamino)pyridine cation that is essentially planar; its r.m.s. deviation for all non-H atoms is 0.0043 Å, with a maximum deviation from the mean plane of -0.0094 (2) Å for the C4 atom. The packing of the ionic entities is realized by alternating layers of cations and anions parallel to (010) whereby the dimethylaminopyridinium molecules are oriented in a zig-zag fashion parallel to the (210) and (210) planes, respectively (Fig. 2). The crystal packing is stabilized by N—H···Cl and C—H···Cl hydrogen bonds involving the chloride atoms of the anions as acceptors (Table 1, Fig. 3). All these interactions link the layers together, forming a three-dimensional network and reinforcing the cohesion of the ionic structure.

A similar complex with a 4-(dimethylamino)pyridinium cation but a different metal-based anion, viz. (C₇H₁₁N₂)⁺[Cr(C₂O₄)₂(H₂O)₂]^-, has been reported recently (Nenwa et al., 2010).

Related literature

For background to hybrid compounds based on protonated substituted N-heterocyclic ligands, see: Bouacida (2008); Bouacida et al. (2007, 2009). For a related structure, see: Nenwa et al. (2010).

S2. Experimental

4-(dimethylamino)pyridine and iron(III) chloride hexahydrate were mixed in an equimolar ratio in acidified water (HCl, 37%_wt). The solution was kept at room temperature for ten days after which crystals suitable for X-ray diffraction could be isolated.

S3. Refinement

H atoms were localized from Fourier maps but introduced in calculated positions and treated as riding on their parent C atoms with C—H = 0.98 Å (methyl) or C—H = 0.95 Å (aromatic), and with U_iso(H) = 1.2 U_eq(C_aryl)and U_iso(H) = 1.5 U_eq(C_methyl). H3 attached to the pyridinium N atom was refined without constraints.

Computing details

Data collection: APEX2 (Bruker, 2011); cell refinement: SAINT (Bruker, 2011); data reduction: SAINT (Bruker, 2011); program(s) used to solve structure: SIR2004 (Burla et al., 2005); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012) and DIAMOND (Brandenburg & Berndt, 2001); software used to prepare material for publication: WinGX (Farrugia, 2012).

Figures

	Fig. 1. The asymmetric unit of (I) with the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level. H atoms are represented as small spheres of arbitrary radii.
	Fig. 2. Packing diagram viewed along [001] showing alterning layers of 4-(dimethylamino)pyridinium cations and [FeCl4] tetrahedraparallel to (010).
	Fig. 3. Packing diagram viewed along [100] showing N—H···Cl and C—H···Cl hydrogen-bonding interactions as dashed lines.

4-(Dimethylamino)pyridinium tetrachloridoferrate(III)

Crystal data

(C7H11N2)[FeCl4]	F(000) = 644
Mr = 320.83	Dx = 1.664 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 2278 reflections
a = 9.0360 (2) Å	θ = 2.9–26.5°
b = 14.0492 (5) Å	µ = 1.98 mm^−1
c = 10.2077 (3) Å	T = 100 K
β = 98.7259 (9)°	Plate, orange
V = 1280.85 (7) Å^3	0.17 × 0.12 × 0.04 mm
Z = 4

Data collection

Bruker APEXII CCD diffractometer	2925 independent reflections
Radiation source: sealed tube	2146 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.041
ϕ and ω scans	θmax = 27.5°, θmin = 2.5°
Absorption correction: multi-scan (SADABS; Bruker, 2011)	h = −8→11
Tmin = 0.789, Tmax = 0.924	k = −18→18
11192 measured reflections	l = −13→13

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)] = 0.034	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.081	H atoms treated by a mixture of independent and constrained refinement
S = 1.03	w = 1/[σ^2(Fo^2) + (0.0258P)^2 + 0.6542P] where P = (Fo^2 + 2Fc^2)/3
2925 reflections	(Δ/σ)max = 0.001
133 parameters	Δρmax = 0.94 e Å^−3
0 restraints	Δρmin = −0.56 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
Fe1	−0.02427 (4)	0.25669 (2)	0.72252 (3)	0.02371 (11)
Cl1	−0.16650 (8)	0.13001 (5)	0.71136 (7)	0.0449 (2)
Cl2	0.11905 (7)	0.25489 (4)	0.91821 (6)	0.03315 (17)
Cl3	0.11063 (8)	0.25245 (5)	0.56193 (7)	0.03676 (18)
Cl4	−0.15646 (8)	0.38804 (5)	0.70930 (7)	0.03842 (18)
C1	0.3730 (3)	0.42873 (17)	0.8197 (3)	0.0281 (6)
H1	0.381	0.4214	0.913	0.034*
C2	0.4618 (3)	0.37690 (19)	0.7516 (3)	0.0374 (7)
H2	0.5322	0.3338	0.7976	0.045*
N3	0.4513 (3)	0.38586 (19)	0.6189 (3)	0.0445 (7)
H3	0.506 (4)	0.355 (2)	0.582 (3)	0.059 (11)*
C4	0.3518 (3)	0.4461 (2)	0.5506 (3)	0.0417 (7)
H4	0.3453	0.4501	0.457	0.05*
C5	0.2614 (3)	0.50068 (19)	0.6130 (3)	0.0331 (6)
H5	0.1935	0.5436	0.5635	0.04*
C6	0.2677 (3)	0.49407 (17)	0.7526 (2)	0.0260 (6)
N7	0.1790 (2)	0.54643 (15)	0.8167 (2)	0.0305 (5)
C8	0.1866 (3)	0.5381 (2)	0.9603 (3)	0.0407 (7)
H8A	0.1606	0.4731	0.9829	0.061*
H8B	0.116	0.5829	0.9908	0.061*
H8C	0.2884	0.5529	1.0036	0.061*
C9	0.0706 (3)	0.6131 (2)	0.7463 (3)	0.0448 (8)
H9A	0.1236	0.6617	0.7024	0.067*
H9B	0.0143	0.6437	0.8095	0.067*
H9C	0.0013	0.5786	0.6797	0.067*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Fe1	0.0239 (2)	0.0260 (2)	0.02024 (19)	−0.00208 (14)	0.00016 (14)	0.00140 (15)
Cl1	0.0505 (4)	0.0485 (4)	0.0315 (4)	−0.0268 (3)	−0.0077 (3)	0.0074 (3)
Cl2	0.0327 (3)	0.0370 (4)	0.0261 (3)	−0.0089 (3)	−0.0072 (3)	0.0047 (3)
Cl3	0.0380 (4)	0.0417 (4)	0.0330 (4)	−0.0003 (3)	0.0131 (3)	−0.0032 (3)
Cl4	0.0419 (4)	0.0406 (4)	0.0322 (4)	0.0157 (3)	0.0035 (3)	0.0016 (3)
C1	0.0269 (13)	0.0283 (14)	0.0287 (14)	−0.0048 (11)	0.0035 (11)	0.0028 (11)
C2	0.0331 (15)	0.0305 (15)	0.050 (2)	−0.0057 (12)	0.0092 (13)	0.0032 (13)
N3	0.0481 (16)	0.0367 (15)	0.0554 (18)	−0.0106 (12)	0.0295 (14)	−0.0140 (13)
C4	0.0578 (19)	0.0419 (17)	0.0266 (16)	−0.0218 (15)	0.0103 (14)	−0.0071 (13)
C5	0.0404 (16)	0.0321 (15)	0.0255 (14)	−0.0088 (12)	0.0002 (12)	−0.0008 (11)
C6	0.0276 (14)	0.0264 (13)	0.0235 (13)	−0.0107 (11)	0.0022 (11)	−0.0001 (10)
N7	0.0314 (12)	0.0300 (12)	0.0299 (13)	−0.0015 (9)	0.0036 (10)	−0.0003 (10)
C8	0.0467 (17)	0.0427 (17)	0.0360 (17)	−0.0037 (14)	0.0167 (14)	−0.0030 (13)
C9	0.0347 (16)	0.0370 (17)	0.061 (2)	0.0049 (13)	0.0025 (14)	0.0062 (15)

Geometric parameters (Å, º)

Fe1—Cl3	2.1870 (7)	C4—H4	0.95
Fe1—Cl1	2.1882 (7)	C5—C6	1.420 (3)
Fe1—Cl4	2.1912 (7)	C5—H5	0.95
Fe1—Cl2	2.2097 (7)	C6—N7	1.331 (3)
C1—C2	1.351 (4)	N7—C8	1.462 (3)
C1—C6	1.421 (3)	N7—C9	1.463 (3)
C1—H1	0.95	C8—H8A	0.98
C2—N3	1.350 (4)	C8—H8B	0.98
C2—H2	0.95	C8—H8C	0.98
N3—C4	1.349 (4)	C9—H9A	0.98
N3—H3	0.79 (3)	C9—H9B	0.98
C4—C5	1.348 (4)	C9—H9C	0.98
Cl3—Fe1—Cl1	109.18 (3)	C6—C5—H5	119.9
Cl3—Fe1—Cl4	109.72 (3)	N7—C6—C5	121.4 (2)
Cl1—Fe1—Cl4	111.80 (3)	N7—C6—C1	122.0 (2)
Cl3—Fe1—Cl2	111.12 (3)	C5—C6—C1	116.6 (2)
Cl1—Fe1—Cl2	107.27 (3)	C6—N7—C8	120.6 (2)
Cl4—Fe1—Cl2	107.73 (3)	C6—N7—C9	121.4 (2)
C2—C1—C6	120.4 (3)	C8—N7—C9	118.0 (2)
C2—C1—H1	119.8	N7—C8—H8A	109.5
C6—C1—H1	119.8	N7—C8—H8B	109.5
N3—C2—C1	120.6 (3)	H8A—C8—H8B	109.5
N3—C2—H2	119.7	N7—C8—H8C	109.5
C1—C2—H2	119.7	H8A—C8—H8C	109.5
C4—N3—C2	121.1 (3)	H8B—C8—H8C	109.5
C4—N3—H3	121 (3)	N7—C9—H9A	109.5
C2—N3—H3	118 (3)	N7—C9—H9B	109.5
C5—C4—N3	121.1 (3)	H9A—C9—H9B	109.5
C5—C4—H4	119.4	N7—C9—H9C	109.5
N3—C4—H4	119.4	H9A—C9—H9C	109.5
C4—C5—C6	120.1 (3)	H9B—C9—H9C	109.5
C4—C5—H5	119.9
C6—C1—C2—N3	−0.4 (4)	C2—C1—C6—N7	−179.8 (2)
C1—C2—N3—C4	−0.4 (4)	C2—C1—C6—C5	0.4 (3)
C2—N3—C4—C5	1.3 (4)	C5—C6—N7—C8	179.6 (2)
N3—C4—C5—C6	−1.3 (4)	C1—C6—N7—C8	−0.2 (4)
C4—C5—C6—N7	−179.4 (2)	C5—C6—N7—C9	0.1 (4)
C4—C5—C6—C1	0.4 (3)	C1—C6—N7—C9	−179.7 (2)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N3—H3···Cl2^i	0.79 (3)	2.60 (3)	3.369 (3)	165 (3)
C4—H4···Cl1^i	0.95	2.74	3.604 (3)	152

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