2-Amino-5-methyl­pyridinium (2-amino-5-methyl­pyridine)trichloro­zincate(II)

The title compound, (C₆H₉N₂)[ZnCl₃(C₆H₈N₂)], consists of one 2-amino-5-methyl­pyridinium cation and one (2-amino-5-methyl­pyridine)trichloro­zincate(II) anion, which are held together by N—H...Cl hydrogen bonds and π–π inter­actions. The cation and the pyridine ligand show similar geometric features, except for the N—C bond lengths. Mol­ecules of the title compound are connected by N—H...Cl hydrogen bonds to form chiral chains; these chains are associated further by C—H...Cl hydrogen bonds to form layers, which are in turn linked by π–π inter­actions.

S1. Comment

There are numerous examples of 2-amino-substituted pyridine compounds in which the 2-aminopyridines act as ligands (Ranninger et al., 1985; Krizanovic et al., 1993; Luque et al., 1997; Qin et al., 1999; Yip et al., 1999; Lah et al., 2002; Ren et al., 2002; Rivas et al., 2003) or as protonated cations (Luque et al., 1997; Jin et al., 2000, 2001, 2002, 2005; Albrecht et al., 2003). All of these studies provide important references to further research of 2-aminopyridines. We have synthesized the title compound, (I), where 2-amino-5-methylpyridine (AMP) appears both as a ligand and as a protonated cation.

The title compound consists of one AMP cation (HAMP) and one AMP ligand (LAMP) coordinated with a [ZnCl₃]⁻ anion. These two moieties are held together by N2—H2A···Cl3 [3.301 (3) Å] and N4—H4B···Cl2 [3.322 (3) Å] hydrogen bonds, and by π–π interaction with a separation of 3.623 (3) Å between the centroids of the HAMP and LAMP moieties (Fig. 1 and Table 2). In the formula unit, the LAMP molecule lies almost perfectly parallel to the HAMP cation, as indicated by the dihedral angle of 0.6 (3)° between them. Atom Cl3 lies 0.708 (4) Å out of the LAMP ring plane, while atom Cl2 lies 1.089 (4) Å out of the HAMP ring plane.

In the HAMP cation, the N4—C11 bond length [1.329 (4) Å] is shorter than those of N3—C11 [1.342 (3) Å] and N3—C7 [1.349 (4) Å], and the C10—C11 [1.398 (4) Å] and C8—C9 [1.399 (4) Å] bond lengths are significantly longer than those of C9—C10 [1.351 (4) Å] and C7—C8 [1.347 (4) Å]. In the LAMP molecule, all the C—N bonds are comparable with one another, and the C—C bond length features are similar to those in the HAMP cation (Table 1). In contrast, in the solid-state structure of AMP (Nahringbauer & Kvick, 1977), the N—C bond length out of the ring is clearly longer than that in the ring, and the C—C bond-length differences are less pronounced. The geometric features of the HAMP cation resemble those observed in other 2-aminopyridine structures (Luque et al., 1997; Jin et al., 2000, 2001, 2002, 2005; Albrecht et al., 2003), which are believed to be involved in amino–imino tautomerism (Inuzuka & Fujimoto, 1986, 1990; Ishikawa et al., 2002). The geometric features of the LAMP molecule are similar to those of some other coordinated 2-aminopyridines (Ranninger et al., 1985; Krizanovic et al., 1993; Qin et al., 1999; Yip et al., 1999; Lah et al., 2002; Ren et al., 2002). The reason for deviations of the LAMP geometry from that of a normal AMP molecule remains unknown.

Molecules of (I) are connected to form a one-dimensional chiral chain along the [010] direction via N3—H3N···Cl3ⁱ, N2—H2B···Cl2ⁱ and N4—H4A···Cl1ⁱ hydrogen bonds (Fig. 2; symmetry code as in Table 2). Between two adjacent molecule of (I) in the chain, three hydrogen-bonded rings, R₄⁴(12), R₂²(8) and R₁¹(6) [using the notation of Etter (1990) and Grell et al. (2000)], are embedded in a larger, R₄³(14), hydrogen-bonded ring (Fig. 3). Two neighboring chains, which are inversely related, are associated by a C9—H9···Cl1ⁱⁱ contact, and therefore the chirality is countervailed. A layer of (I) parallel to (101) is established by translation of the two inversely related chains. Finally, the whole structure is established by translation of the layer. There are π–π interactions (Sharma et al., 1993; Pedireddi et al., 1996) between neighboring layers, with a centroid-to-centroid distance of 3.908 (4) Å between the LAMP and HAMP moieties. A C12—H12B···π contact (LAMP; symmetry code: 1/2 + x, −1/2 − y, 1/2 + z) [with a distance of 3.325 (3) Å between the H atom and the centriod of LAMP] plays a subordinative role in stabilizing the structure.

S2. Experimental

2-Amino-5-methylpyridine, ZnCl₂ and aqueous HCl in a molar ratio of 2:1:1 were mixed and dissolved in sufficient ethanol by heating to a temperature at which a clear solution resulted. Crystals of (I) were formed by gradual evaporation of ethanol over a period of one week at 303 K, with a yield of 56% based on AMP. IR (KBr, cm⁻¹): 3415 (s), 3333 (s), 3284 (s), 3200 (s), 3081, 3053, 2924, 1670 (s), 1645 (s), 1617 (s), 1569, 1555, 1515 (s), 1463, 1406, 1347, 1329, 1279, 1239, 1210, 1154, 1091, 1041, 832, 777, 717, 667, 648, 510, 460, 437.

S3. Refinement

H atoms attaching to N atoms were located in difference Fourier maps and their parameters were refined freely. Other H atoms were placed in calculated positions and allowed to ride on their parent atoms at C—H distances of 0.93 (aromatic) and 0.96 Å (methyl), with U_iso(H) values of 1.2 or 1.5 times U_eq of the parent atoms.

Computing details

Data collection: SMART (Bruker, 2000); cell refinement: SMART; data reduction: SAINT (Bruker, 2000); program(s) used to solve structure: SHELXTL (Bruker, 2000); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Figures

	Fig. 1. The cell unit of (I), with atom labels, showing 40% probability displacement ellipsoids. Hydrogen bonds are shown as dashed lines.
	Fig. 2. The chiral hydrogen-bond chain of (I) along the [010] direction. Hydrogen bonds are shown as dashed lines.
	Fig. 3. Layer formation of (I), parallel to (101). Hydrogen bonds are shown as dashed lines.

2-Amino-5-methylpyridinium (2-amino-5-methylpyridine)trichlorozincate(II)

Crystal data

(C6H9N2)[ZnCl3(C6H8N2)]	F(000) = 792
Mr = 389.02	Dx = 1.536 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 3253 reflections
a = 9.254 (3) Å	θ = 2.4–26.0°
b = 13.726 (4) Å	µ = 1.93 mm^−1
c = 13.572 (5) Å	T = 293 K
β = 102.57 (3)°	Prism, colorless
V = 1682.6 (10) Å^3	0.30 × 0.25 × 0.22 mm
Z = 4

Data collection

Bruker SMART Apex CCD area-detector diffractometer	3304 independent reflections
Radiation source: sealed tube	2518 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.049
ϕ and ω scans	θmax = 26.0°, θmin = 2.1°
Absorption correction: multi-scan (SADABS; Bruker, 2000)	h = −11→10
Tmin = 0.57, Tmax = 0.65	k = −15→16
8903 measured reflections	l = −14→16

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)] = 0.031	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.072	H atoms treated by a mixture of independent and constrained refinement
S = 0.93	w = 1/[σ^2(Fo^2) + (0.0325P)^2] where P = (Fo^2 + 2Fc^2)/3
3304 reflections	(Δ/σ)max = 0.001
203 parameters	Δρmax = 0.35 e Å^−3
101 restraints	Δρmin = −0.25 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
Zn	0.84505 (3)	0.46058 (2)	0.76390 (2)	0.04605 (12)
Cl1	1.01068 (8)	0.58350 (5)	0.78368 (6)	0.0614 (2)
Cl2	0.63306 (8)	0.49257 (5)	0.64987 (6)	0.0584 (2)
Cl3	0.79975 (8)	0.42665 (5)	0.91729 (6)	0.0596 (2)
C1	1.0212 (3)	0.3738 (2)	0.6350 (2)	0.0506 (6)
H1	1.0320	0.4399	0.6233	0.061*
C2	1.0866 (3)	0.3098 (2)	0.5812 (2)	0.0565 (7)
C3	1.0699 (3)	0.2114 (2)	0.6019 (2)	0.0627 (7)
H3	1.1133	0.1645	0.5682	0.075*
C4	0.9915 (3)	0.1836 (2)	0.6702 (2)	0.0602 (7)
H4	0.9803	0.1177	0.6828	0.072*
C5	0.9269 (3)	0.25364 (18)	0.7221 (2)	0.0476 (6)
C6	1.1708 (3)	0.3442 (3)	0.5053 (2)	0.0823 (10)
H6A	1.1898	0.4128	0.5139	0.123*
H6B	1.1136	0.3322	0.4384	0.123*
H6C	1.2631	0.3098	0.5148	0.123*
C7	0.7432 (3)	0.1169 (2)	0.4193 (2)	0.0598 (7)
H7	0.7554	0.0505	0.4101	0.072*
C8	0.8044 (3)	0.1808 (2)	0.3650 (2)	0.0595 (7)
C9	0.7798 (3)	0.2795 (2)	0.3815 (2)	0.0587 (7)
H9	0.8188	0.3260	0.3447	0.070*
C10	0.7012 (3)	0.3094 (2)	0.4489 (2)	0.0552 (7)
H10	0.6866	0.3756	0.4578	0.066*
C11	0.6419 (3)	0.24088 (19)	0.5052 (2)	0.0505 (6)
C12	0.8961 (4)	0.1478 (3)	0.2923 (3)	0.0860 (10)
H12A	0.9990	0.1587	0.3215	0.129*
H12B	0.8682	0.1841	0.2306	0.129*
H12C	0.8796	0.0797	0.2785	0.129*
N1	0.9421 (2)	0.34871 (14)	0.70374 (16)	0.0431 (5)
N2	0.8468 (3)	0.22852 (18)	0.7900 (2)	0.0624 (7)
N3	0.6645 (3)	0.14677 (17)	0.4865 (2)	0.0549 (6)
N4	0.5635 (3)	0.2642 (2)	0.5730 (2)	0.0631 (7)
H2B	0.845 (3)	0.1667 (15)	0.805 (3)	0.089 (11)*
H4B	0.562 (4)	0.3254 (16)	0.598 (3)	0.095 (12)*
H2A	0.825 (3)	0.2756 (18)	0.8367 (19)	0.073 (10)*
H4A	0.532 (3)	0.2184 (19)	0.618 (2)	0.092 (11)*
H3N	0.623 (3)	0.1058 (18)	0.520 (2)	0.074 (10)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Zn	0.0580 (2)	0.03524 (18)	0.0481 (2)	0.00135 (13)	0.01856 (15)	−0.00093 (14)
Cl1	0.0750 (5)	0.0420 (4)	0.0710 (5)	−0.0115 (3)	0.0243 (4)	−0.0052 (3)
Cl2	0.0644 (5)	0.0443 (4)	0.0640 (5)	0.0068 (3)	0.0081 (4)	−0.0025 (3)
Cl3	0.0809 (5)	0.0539 (4)	0.0505 (5)	−0.0042 (4)	0.0286 (4)	−0.0020 (3)
C1	0.0545 (14)	0.0474 (13)	0.0520 (15)	0.0016 (11)	0.0159 (12)	0.0009 (12)
C2	0.0548 (14)	0.0650 (15)	0.0512 (15)	0.0075 (12)	0.0151 (12)	−0.0043 (13)
C3	0.0668 (16)	0.0614 (15)	0.0590 (17)	0.0181 (13)	0.0120 (13)	−0.0149 (14)
C4	0.0714 (16)	0.0439 (13)	0.0628 (17)	0.0088 (12)	0.0092 (13)	−0.0087 (13)
C5	0.0539 (13)	0.0356 (12)	0.0523 (14)	0.0018 (11)	0.0093 (12)	−0.0042 (11)
C6	0.080 (2)	0.110 (3)	0.065 (2)	0.0131 (19)	0.0340 (18)	0.000 (2)
C7	0.0627 (15)	0.0516 (14)	0.0613 (16)	0.0018 (12)	0.0052 (13)	−0.0035 (13)
C8	0.0523 (14)	0.0691 (15)	0.0555 (15)	0.0026 (12)	0.0081 (12)	−0.0001 (13)
C9	0.0546 (15)	0.0628 (15)	0.0592 (16)	−0.0064 (12)	0.0136 (13)	0.0120 (13)
C10	0.0572 (15)	0.0473 (13)	0.0599 (16)	−0.0058 (12)	0.0103 (12)	0.0083 (12)
C11	0.0528 (13)	0.0447 (13)	0.0532 (15)	−0.0056 (11)	0.0094 (12)	0.0034 (12)
C12	0.072 (2)	0.114 (3)	0.074 (2)	0.014 (2)	0.0209 (18)	−0.010 (2)
N1	0.0490 (11)	0.0348 (10)	0.0472 (12)	0.0019 (9)	0.0141 (9)	−0.0013 (9)
N2	0.0856 (19)	0.0357 (14)	0.0727 (19)	−0.0077 (12)	0.0320 (15)	0.0017 (13)
N3	0.0613 (13)	0.0437 (12)	0.0591 (14)	−0.0082 (11)	0.0119 (11)	0.0058 (11)
N4	0.0740 (17)	0.0548 (16)	0.0654 (18)	−0.0058 (13)	0.0264 (14)	−0.0006 (14)

Geometric parameters (Å, º)

Zn—N1	2.037 (2)	C7—N3	1.349 (4)
Zn—Cl1	2.2558 (9)	C7—H7	0.9300
Zn—Cl3	2.2597 (11)	C8—C9	1.399 (4)
Zn—Cl2	2.2617 (12)	C8—C12	1.504 (4)
C1—N1	1.351 (3)	C9—C10	1.351 (4)
C1—C2	1.364 (4)	C9—H9	0.9300
C1—H1	0.9300	C10—C11	1.398 (4)
C2—C3	1.394 (4)	C10—H10	0.9300
C2—C6	1.498 (4)	C11—N4	1.329 (4)
C3—C4	1.352 (4)	C11—N3	1.342 (3)
C3—H3	0.9300	C12—H12A	0.9600
C4—C5	1.401 (4)	C12—H12B	0.9600
C4—H4	0.9300	C12—H12C	0.9600
C5—N1	1.342 (3)	N2—H2B	0.873 (19)
C5—N2	1.347 (4)	N2—H2A	0.955 (18)
C6—H6A	0.9600	N3—H3N	0.864 (18)
C6—H6B	0.9600	N4—H4B	0.905 (19)
C6—H6C	0.9600	N4—H4A	0.963 (19)
C7—C8	1.347 (4)
N1—Zn—Cl1	105.31 (6)	C7—C8—C9	116.1 (3)
N1—Zn—Cl3	113.59 (7)	C7—C8—C12	121.8 (3)
Cl1—Zn—Cl3	107.58 (4)	C9—C8—C12	122.0 (3)
N1—Zn—Cl2	105.33 (6)	C10—C9—C8	122.2 (3)
Cl1—Zn—Cl2	113.70 (4)	C10—C9—H9	118.9
Cl3—Zn—Cl2	111.30 (4)	C8—C9—H9	118.9
N1—C1—C2	125.2 (3)	C9—C10—C11	119.9 (3)
N1—C1—H1	117.4	C9—C10—H10	120.0
C2—C1—H1	117.4	C11—C10—H10	120.0
C1—C2—C3	115.8 (3)	N4—C11—N3	119.6 (3)
C1—C2—C6	121.5 (3)	N4—C11—C10	123.7 (3)
C3—C2—C6	122.7 (3)	N3—C11—C10	116.7 (3)
C4—C3—C2	120.8 (3)	C8—C12—H12A	109.5
C4—C3—H3	119.6	C8—C12—H12B	109.5
C2—C3—H3	119.6	H12A—C12—H12B	109.5
C3—C4—C5	120.2 (3)	C8—C12—H12C	109.5
C3—C4—H4	119.9	H12A—C12—H12C	109.5
C5—C4—H4	119.9	H12B—C12—H12C	109.5
N1—C5—N2	118.1 (2)	C5—N1—C1	118.1 (2)
N1—C5—C4	120.1 (3)	C5—N1—Zn	125.85 (18)
N2—C5—C4	121.8 (3)	C1—N1—Zn	115.96 (16)
C2—C6—H6A	109.5	C5—N2—H2B	117 (2)
C2—C6—H6B	109.5	C5—N2—H2A	120.3 (17)
H6A—C6—H6B	109.5	H2B—N2—H2A	119 (3)
C2—C6—H6C	109.5	C11—N3—C7	123.3 (3)
H6A—C6—H6C	109.5	C11—N3—H3N	115 (2)
H6B—C6—H6C	109.5	C7—N3—H3N	122 (2)
C8—C7—N3	121.7 (3)	C11—N4—H4B	122 (2)
C8—C7—H7	119.2	C11—N4—H4A	124.4 (19)
N3—C7—H7	119.2	H4B—N4—H4A	110 (3)
N1—C1—C2—C3	−1.0 (4)	C4—C5—N1—C1	−0.4 (4)
N1—C1—C2—C6	179.2 (3)	N2—C5—N1—Zn	−3.5 (4)
C1—C2—C3—C4	0.9 (4)	C4—C5—N1—Zn	175.5 (2)
C6—C2—C3—C4	−179.2 (3)	C2—C1—N1—C5	0.7 (4)
C2—C3—C4—C5	−0.7 (5)	C2—C1—N1—Zn	−175.5 (2)
C3—C4—C5—N1	0.4 (4)	Cl1—Zn—N1—C5	145.78 (19)
C3—C4—C5—N2	179.4 (3)	Cl3—Zn—N1—C5	28.3 (2)
N3—C7—C8—C9	−1.0 (4)	Cl2—Zn—N1—C5	−93.7 (2)
N3—C7—C8—C12	178.1 (3)	Cl1—Zn—N1—C1	−38.3 (2)
C7—C8—C9—C10	1.0 (4)	Cl3—Zn—N1—C1	−155.77 (17)
C12—C8—C9—C10	−178.0 (3)	Cl2—Zn—N1—C1	82.18 (19)
C8—C9—C10—C11	0.2 (4)	N4—C11—N3—C7	−179.7 (3)
C9—C10—C11—N4	179.9 (3)	C10—C11—N3—C7	1.7 (4)
C9—C10—C11—N3	−1.5 (4)	C8—C7—N3—C11	−0.4 (4)
N2—C5—N1—C1	−179.4 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N2—H2A···Cl3	0.96 (2)	2.38 (2)	3.301 (3)	162 (2)
N2—H2B···Cl2^i	0.87 (2)	2.47 (2)	3.335 (3)	174 (3)
N3—H3N···Cl3^i	0.86 (2)	2.65 (2)	3.279 (3)	131 (2)
N4—H4B···Cl2	0.91 (2)	2.45 (2)	3.322 (3)	162 (3)
N4—H4A···Cl1^i	0.96 (2)	2.37 (2)	3.315 (3)	168 (3)
C9—H9···Cl1^ii	0.93	2.88	3.770 (3)	162

Symmetry codes: (i) −x+3/2, y−1/2, −z+3/2; (ii) −x+2, −y+1, −z+1.