Bis(μ-4-chloro­benzoato-κ²O:O)bis[(2-aminopyridine-κN)silver(I)]

The title compound, [Ag₂(C₇H₄ClO₂)₂(C₅H₆N₂)₂], lies about an inversion centre and the Ag atom is three-coordinated by two O atoms and one N atom from three different ligands. The 4-chloro­benzoate anion acts as a monodonor ligand, bridging two inversion-related Ag atoms of the compound into a dimer. There are weak intermolecular N—H...O hydrogen bonds in the structure.

S1. Comment

Pyridine and its derivative metal complexes are of much current interest in coordination chemistry. Indeed, many monomers, dimers and polymers have been prepared and structurally determined. Recently, we reported a few silver(I) complexes with pyridine and pyridine derivatives (Zhu et al., 2001; Zhu, Liu et al., 2003; Zhu, Usman et al., 2003a; Zhu, Yang et al., 2003; Zhu, Zhang, Sun et al., 2003; Zhu, Zeng et al., 2003). Some of the complexes (Zhu et al., 2001) have high cytotoxicity. To further our work in this field, we report here the crystal structure of the title silver carboxylate complex with 2-aminopyridine, (I). \sch

In compound (I), the Ag atom is three-coordinated by two O atoms from different 4-chlorobenzoate anions and one N atom from the 2-aminopyridine ligand. This AgO₂N coordination forms a Y-shaped geometry at Ag1, with the three angles subtended at the Ag atom being 82.80 (12), 120.37 (12) and 156.79 (13)°. The Ag1—O1 bond length of 2.589 (3) Å is much longer than that [2.103 (5) Å] in bis[aqua(4-chlorobenzoato)silver(I)] (Zhu, Usman et al., 2003b), but is close to that [2.512 (4) Å] found in 4-fluorobenzoatosilver(I) (Zhu, Zeng et al., 2003). The Ag—N bond length [2.137 (4) Å] is comparable with those in similar silver complexes with pyridine derivatives that we have investigated. All other bond lengths (Table 1) in (I) are within normal ranges (Allen et al., 1987).

Some pyramidalization is shown by atom O1, which is 0.407 (3) Å out of the plane through C1, Ag1 and Ag1ⁱ [symmetry code: (i) ?]. The two exocyclic angles about O1 are strongly asymmetric, with Ag1—O1—C1 = 138.0 (3)° being much larger than Ag1ⁱ—O1—C1 = 107.6 (3)°, and this seems to be caused by the N2—H2···O2ⁱ attraction on one side and the H3···H12 steric repulsion on the other. As is shown in (I), the benzoate carboxyl group acts as a monodonor bridging two Ag atoms, forming the title dimeric dinuclear complex.

The central four-membered coordination ring, Ag₂O₂, has a rectangular geometry, Ag1—O1 = 2.589 (3) Å being noticeably longer than Ag1—O1ⁱ = 2.191 (3) Å. The O1—Ag1—O1ⁱ bond angle must be related to the Ag1—O1—Ag1ⁱ angle and the planarity of the central ring, while the asymmetry of the exocyclic bond angles about Ag1 is related to the planarity of the Ag-bonds and the different interactions in which the two sides of the aminopyridine ligand are involved, namely the H1···H12 (2.71 Å) contact on the side of the narrower O1—Ag1—N1 [120.4 (1)°] angle and the N2—H2A···O2A intramolecular hydrogen bond on the side of the larger N1—Ag1—O1ⁱ [156.8 (1)°] angle. The ring is on a plane, which makes dihedral angles with the two aromatic rings of 42.4 (2)° with benzene and 38.1 (2)° with pyridine. The two aromatic rings are approximately coplanar, the dihedral angle they form being only 12.4 (2)°. The displacement from perfect coplanarity is probably caused by steric hindrance between the two organic ligands, which is also related to the more pronounced displacement from coplanarity which these ligands show with respect to the central coordination ring.

The intramolecular C3—H3···O1 and C7—H7···O2 interactions, the H···O distances of which are significantly less than the sum of the van der Waals radii, are remarkable for the conformation of the anionic ligand. In the crystal structure of (I), the molecules are interconnected, in columns parallel to the b axis, by intermolecular N2—H2B—O2ⁱⁱ and N2—H2A···O2ⁱⁱⁱ hydrogen bonds (Table 2; symmetry codes as in Table 2?).

S2. Experimental

Ag₂O (0.5 mmol, 116 mg) and 4-chlorobenzoic acid (1 mmol, 157 mg) were dissolved in a 30% aqueous ammonia solution (10 ml), and the resulting solution was stirred for ca 10 min until a clear solution was obtained. A solution of 2-aminopyridine (1 mmol, 94 mg) in acetonitrile (2 ml) was added to the above solution. The resulting solution was kept in air for 2 d with ammonia gas escaping. Colourless crystals of (I) were collected and washed with water and acetonitrile in turn, and then dried in a vacuum desiccator over CaCl₂ (yield 44%). Analysis, calculated for C₁₂H₁₀AgClN₂O₂: C 40.31, H 2.82, N 7.83%; found: C 39.95, H 2.88, N 7.69%.

S3. Refinement

All H atoms were placed in geometric positions and constrained to ride on their parent atoms, with N—H and C—H distances of 0.90 and 0.96 Å, respectively. They were treated as riding atoms, with U_iso(H) = 1.2U_eq(C) or 1.2U_eq(N).

Computing details

Data collection: SMART (Siemens, 1996); cell refinement: SMART; data reduction: SAINT (Siemens, 1996); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997a); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997a); molecular graphics: SHELXTL (Sheldrick, 1997b); software used to prepare material for publication: SHELXTL.

Figures

Fig. 1. The structure of (I) showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level and H atoms are shown as small spheres of arbitrary radii.

4-chlorobenzoato-2-aminopyridinesilver(I)

Crystal data

[Ag2(C7H4ClO2)2(C5H6N2)2]	F(000) = 704
Mr = 715.08	Dx = 1.921 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
a = 14.366 (5) Å	Cell parameters from 1840 reflections
b = 5.545 (2) Å	θ = 2.8–22.2°
c = 15.530 (6) Å	µ = 1.84 mm^−1
β = 92.360 (6)°	T = 298 K
V = 1236.0 (8) Å^3	Prism, colourless
Z = 2	0.42 × 0.30 × 0.09 mm

Data collection

Siemens SMART CCD area-detector diffractometer	2179 independent reflections
Radiation source: fine-focus sealed tube	1566 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.038
ϕ and ω scans	θmax = 25.0°, θmin = 1.9°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −17→17
Tmin = 0.512, Tmax = 0.852	k = −5→6
5997 measured reflections	l = −15→18

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)] = 0.035	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.111	H-atom parameters constrained
S = 0.99	w = 1/[σ^2(Fo^2) + (0.0606P)^2] where P = (Fo^2 + 2Fc^2)/3
2179 reflections	(Δ/σ)max = 0.001
163 parameters	Δρmax = 0.58 e Å^−3
0 restraints	Δρmin = −0.81 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
Ag1	1.04733 (3)	0.22215 (8)	0.07387 (3)	0.0661 (2)
Cl1	0.60593 (12)	0.8949 (3)	0.15038 (11)	0.0784 (5)
N1	1.0469 (3)	0.5162 (7)	0.1628 (2)	0.0395 (9)
N2	1.1726 (3)	0.3458 (7)	0.2375 (3)	0.0523 (11)
H2A	1.1758	0.2383	0.1978	0.063*
H2B	1.2116	0.3433	0.2810	0.063*
O1	0.8921 (2)	0.0524 (6)	0.0085 (2)	0.0525 (9)
O2	0.7910 (2)	0.0630 (6)	−0.1029 (2)	0.0529 (9)
C1	0.8189 (3)	0.1321 (8)	−0.0307 (3)	0.0419 (11)
C2	0.7646 (3)	0.3176 (8)	0.0160 (3)	0.0414 (11)
C3	0.7860 (4)	0.3775 (10)	0.1002 (3)	0.0554 (14)
H3	0.8347	0.2980	0.1297	0.066*
C4	0.7373 (4)	0.5525 (11)	0.1422 (4)	0.0611 (15)
H4	0.7526	0.5906	0.1994	0.073*
C5	0.6667 (4)	0.6682 (9)	0.0993 (4)	0.0533 (14)
C6	0.6408 (5)	0.6093 (12)	0.0171 (4)	0.079 (2)
H6	0.5905	0.6856	−0.0109	0.094*
C7	0.6907 (4)	0.4331 (11)	−0.0242 (4)	0.0713 (18)
H7	0.6735	0.3923	−0.0808	0.086*
C8	1.1065 (3)	0.5180 (8)	0.2315 (3)	0.0368 (10)
C9	1.1016 (3)	0.6953 (8)	0.2958 (3)	0.0452 (12)
H9	1.1432	0.6937	0.3433	0.054*
C10	1.0353 (4)	0.8693 (9)	0.2875 (4)	0.0530 (13)
H10	1.0306	0.9869	0.3298	0.064*
C11	0.9750 (4)	0.8705 (9)	0.2161 (4)	0.0544 (14)
H11	0.9300	0.9901	0.2089	0.065*
C12	0.9827 (3)	0.6947 (8)	0.1569 (3)	0.0455 (12)
H12	0.9415	0.6961	0.1092	0.055*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ag1	0.0748 (4)	0.0710 (3)	0.0508 (3)	0.0119 (2)	−0.0171 (2)	−0.0239 (2)
Cl1	0.0897 (11)	0.0602 (10)	0.0877 (12)	0.0128 (8)	0.0353 (10)	−0.0058 (8)
N1	0.042 (2)	0.041 (2)	0.036 (2)	−0.0049 (17)	−0.0062 (18)	−0.0002 (17)
N2	0.056 (3)	0.050 (2)	0.050 (3)	0.012 (2)	−0.020 (2)	−0.012 (2)
O1	0.0468 (19)	0.064 (2)	0.045 (2)	0.0167 (17)	−0.0177 (17)	−0.0119 (17)
O2	0.056 (2)	0.065 (2)	0.036 (2)	0.0097 (17)	−0.0154 (17)	−0.0073 (16)
C1	0.044 (3)	0.043 (3)	0.038 (3)	−0.001 (2)	−0.003 (2)	0.003 (2)
C2	0.040 (3)	0.047 (3)	0.037 (3)	0.001 (2)	−0.002 (2)	0.004 (2)
C3	0.047 (3)	0.070 (4)	0.048 (3)	0.011 (3)	−0.010 (3)	−0.009 (3)
C4	0.058 (3)	0.076 (4)	0.049 (4)	0.007 (3)	−0.003 (3)	−0.017 (3)
C5	0.062 (3)	0.047 (3)	0.052 (4)	0.004 (3)	0.020 (3)	−0.002 (2)
C6	0.089 (5)	0.095 (5)	0.052 (4)	0.052 (4)	0.000 (3)	0.009 (3)
C7	0.080 (4)	0.091 (5)	0.042 (3)	0.040 (4)	−0.013 (3)	−0.006 (3)
C8	0.038 (2)	0.037 (2)	0.035 (3)	−0.006 (2)	−0.003 (2)	0.0002 (19)
C9	0.044 (3)	0.047 (3)	0.044 (3)	−0.004 (2)	−0.005 (2)	−0.010 (2)
C10	0.053 (3)	0.049 (3)	0.058 (4)	−0.004 (3)	0.007 (3)	−0.011 (3)
C11	0.052 (3)	0.044 (3)	0.067 (4)	0.011 (2)	−0.001 (3)	−0.001 (3)
C12	0.042 (3)	0.050 (3)	0.043 (3)	0.001 (2)	−0.012 (2)	0.009 (2)

Geometric parameters (Å, º)

Ag1—N1	2.137 (4)	C3—H3	0.9300
Ag1—O1^i	2.191 (3)	C4—C5	1.352 (7)
Ag1—O1	2.589 (3)	C4—H4	0.9300
Cl1—C5	1.741 (5)	C5—C6	1.354 (8)
N1—C8	1.341 (6)	C6—C7	1.385 (8)
N1—C12	1.353 (6)	C6—H6	0.9300
N2—C8	1.347 (6)	C7—H7	0.9300
N2—H2A	0.8600	C8—C9	1.404 (6)
N2—H2B	0.8600	C9—C10	1.358 (7)
O1—C1	1.272 (5)	C9—H9	0.9300
O1—Ag1^i	2.191 (3)	C10—C11	1.378 (7)
O2—C1	1.237 (5)	C10—H10	0.9300
C1—C2	1.496 (7)	C11—C12	1.348 (7)
C2—C7	1.369 (7)	C11—H11	0.9300
C2—C3	1.373 (7)	C12—H12	0.9300
C3—C4	1.376 (7)
N1—Ag1—O1^i	156.79 (13)	C4—C5—C6	121.4 (5)
N1—Ag1—O1	120.37 (12)	C4—C5—Cl1	119.9 (4)
O1^i—Ag1—O1	82.80 (12)	C6—C5—Cl1	118.7 (5)
C8—N1—C12	117.4 (4)	C5—C6—C7	118.7 (5)
C8—N1—Ag1	120.1 (3)	C5—C6—H6	120.7
C12—N1—Ag1	122.3 (3)	C7—C6—H6	120.7
C8—N2—H2A	120.0	C2—C7—C6	121.7 (5)
C8—N2—H2B	120.0	C2—C7—H7	119.2
H2A—N2—H2B	120.0	C6—C7—H7	119.2
C1—O1—Ag1^i	107.6 (3)	N1—C8—N2	118.4 (4)
C1—O1—Ag1	138.0 (3)	N1—C8—C9	121.4 (4)
Ag1^i—O1—Ag1	97.20 (12)	N2—C8—C9	120.2 (4)
O2—C1—O1	123.8 (4)	C10—C9—C8	119.0 (5)
O2—C1—C2	119.8 (4)	C10—C9—H9	120.5
O1—C1—C2	116.4 (4)	C8—C9—H9	120.5
C7—C2—C3	117.5 (5)	C9—C10—C11	119.7 (5)
C7—C2—C1	120.7 (5)	C9—C10—H10	120.2
C3—C2—C1	121.8 (4)	C11—C10—H10	120.2
C2—C3—C4	121.6 (5)	C12—C11—C10	118.6 (5)
C2—C3—H3	119.2	C12—C11—H11	120.7
C4—C3—H3	119.2	C10—C11—H11	120.7
C5—C4—C3	119.2 (5)	C11—C12—N1	123.9 (4)
C5—C4—H4	120.4	C11—C12—H12	118.0
C3—C4—H4	120.4	N1—C12—H12	118.0
O1^i—Ag1—N1—C8	−43.6 (6)	C3—C4—C5—C6	2.6 (9)
O1—Ag1—N1—C8	140.2 (3)	C3—C4—C5—Cl1	−178.5 (4)
O1^i—Ag1—N1—C12	142.2 (4)	C4—C5—C6—C7	−2.6 (10)
O1—Ag1—N1—C12	−34.0 (4)	Cl1—C5—C6—C7	178.4 (5)
N1—Ag1—O1—C1	51.9 (5)	C3—C2—C7—C6	1.9 (10)
O1^i—Ag1—O1—C1	−126.6 (5)	C1—C2—C7—C6	−178.5 (6)
N1—Ag1—O1—Ag1^i	178.52 (14)	C5—C6—C7—C2	0.4 (11)
O1^i—Ag1—O1—Ag1^i	0.0	C12—N1—C8—N2	−178.2 (4)
Ag1^i—O1—C1—O2	−1.0 (6)	Ag1—N1—C8—N2	7.3 (6)
Ag1—O1—C1—O2	122.3 (5)	C12—N1—C8—C9	1.1 (7)
Ag1^i—O1—C1—C2	178.1 (3)	Ag1—N1—C8—C9	−173.4 (4)
Ag1—O1—C1—C2	−58.6 (6)	N1—C8—C9—C10	−0.4 (7)
O2—C1—C2—C7	−8.0 (8)	N2—C8—C9—C10	178.9 (5)
O1—C1—C2—C7	172.9 (5)	C8—C9—C10—C11	−0.8 (8)
O2—C1—C2—C3	171.6 (5)	C9—C10—C11—C12	1.2 (8)
O1—C1—C2—C3	−7.5 (7)	C10—C11—C12—N1	−0.5 (8)
C7—C2—C3—C4	−2.0 (9)	C8—N1—C12—C11	−0.7 (7)
C1—C2—C3—C4	178.4 (5)	Ag1—N1—C12—C11	173.7 (4)
C2—C3—C4—C5	−0.2 (9)

Symmetry code: (i) −x+2, −y, −z.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N2—H2A···O2^i	0.86	2.29	3.141 (5)	170
N2—H2B···O2^ii	0.86	2.16	2.990 (5)	163
C3—H3···O1	0.93	2.49	2.789 (6)	99
C7—H7···O2	0.93	2.52	2.815 (7)	99

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