catena-Poly­[[di-[mu]-benzoato-[kappa]⁴O:O'-disilver(I)]-[mu]-N,N'-bis(2-fluoro­benzyl­idene)­butane-1,4-di­amine-[kappa]²N:N']

The title complex, [Ag₂(C₇H₅O₂)₂(C₁₈H₁₈F₂N₂)]_n, is a dinuclear silver(I) compound with one inversion centre between pairs of Ag atoms and another at the mid-point of the central C-C bond in the butane-1,4-diamine moiety. Each of the smallest repeat units consists of two silver(I) cations, two benzoate anions and one N,N'-bis(2-fluorobenzyl­idene)­butane-1,4-di­amine Schiff base ligand. Each Ag^I ion is three-coordinated in a trigonal configuration by two O atoms from two benzoate anions and one N atom from a Schiff base ligand. The di-[mu]-benzoato-disilver(I) moieties are linked by the bridging Schiff base ligand, giving zigzag polymeric chains with an [-Ag...Ag-N-C-C-C-C-N-]_n backbone running along the b axis.

S1. Comment

Transition metal compounds containing Schiff base ligands have been of great interest for many years (Yamada, 1999; Chang et al., 1998; Chaturvedl, 1977; Archer & Wang, 1990). These compounds play an important role in the development of coordination chemistry related to catalysis and enzymatic reactions, magnetism and molecular architectures (Costamagna et al., 1992; Bhatia et al., 1981). Inorganic supramolecular chemistry and in particular the construction of polymeric coordination networks is an extremely topical area of research (Xu et al., 2001; Yaghi & Li, 1996). The construction of a wide variety of network topologies has been achieved through ligand design and the use of different counter-anions. Owing to the flexible coordination sphere of Ag^I, coordination numbers from two to six are all possible, and because of the relatively weak nature of many Ag^I-ligand interactions such compounds are particularly susceptible to the influence of weaker supramolecular forces (Khlobystov et al., 2001).

Our work is aimed at obtaining multidimensional metal complexes. On the basis of the above considerations, we designed and synthesized a flexible bidentate ligand, N,N'-bis(2-fluorophenylmethylidene)butane-1,4-diamine (BFBD). The flexible BFBD ligand offers advantages over rigid ligands in that it can adopt a different coordination mode according to the geometric needs of the coordination environment of the transition metal ion. Silver(I) is a good candidate for a trigonal coordination geometry. We report here an interesting one-dimensional infinite chain structure formed by the reaction of the BFBD ligand with silver(I) benzoate.

The title complex, (I), is a polymeric compound with an inversion center (Fig. 1). The smallest repeat unit of the complex contains a BFBD–Ag^I₂ cation and two benzoate anions. Each Ag^I ion is three-coordinated in a trigonal configuration by two O atoms belonging to two benzoate anions and one N atom of a Schiff base ligand. Atom Ag1 lies 0.100 (6) Å out of the plane defined by the three donor atoms [O1/N1/O2ⁱ; symmetry code: (i) 1 − x, 2 − y, 1 − z]. The benzoate anion bridges two silver(I) ions related by the inversion center. The distance [3.051 (2) Å] between the two silver ions is shorter than the van der Waals radii of two Ag atoms (3.44 Å) and comparable to the value of 3.035 (2) Å observed in a silver complex with weak Ag···Ag interactions (Zhu, Shao et al., 2003), indicating the existence of similar interactions in (I).

The Ag1—N1 bond length [2.417 (7) Å; Table 1] is comparable to the value of 2.397 (3) Å observed in another Schiff base–silver(I) complex (Fei et al., 2000). The average Ag—O bond length in (I) [2.216 (6) Å] is essentially the same as the value of 2.210 (4) Å observed in a silver(I)–carboxylate complex (Zhu, Zhang et al., 2003). The O1—Ag1—O2ⁱ bond angle [153.9 (3) °] is larger than the other two bond angles about atom Ag1, viz. N1—Ag1—O2ⁱ [103.8 (2) °] and N1—Ag1—O1 [101.6 (2) °], apparently as a result of the Ag···Ag interactions. The Ag···Ag interactions also flatten the eight-membered Ag1/O1/C10/O2/Ag1ⁱ/O1ⁱ/C10ⁱ/O2ⁱ ring. The diagonal distance between atoms C10 and C10ⁱ [5.439 (9) Å] is much longer than the diagonal distance [3.051 (2) Å] between Ag1 and Ag1ⁱ. The mean deviation of the eight-membered ring from the combined mean plane is 0.109 (7) Å.

The bridging BFBD ligand adopts a trans configuration and coordinates to two Ag atoms belonging to two different repeat units. The C1=N1 bond length [1.287 (10) Å] conforms to the value for a double bond, while the C8—N1 bond length [1.472 (10) Å] conforms to the value for a single bond.

In the crystal structure, the linking of the dibenzoatodisilver(I) moieties by the bridging Schiff base ligand results in zigzag polymeric chains with an [–Ag—Ag—N—C—C—C—C—N–]_n backbone running along the b axis. The molecules stack along the a axis with no short intermolecular contacts (<3.2 Å; see Fig. 2).

S2. Experimental

N,N'-Bis(2-fluorobenzylidene)butane-1,4-diamine (0.1 mmol, 30.0 mg) and silver(I) benzoate (0.2 mmol, 45.8 mg) were dissolved in a 30% ammonia solution (10 ml) with stirring. The mixture was stirred at room temperature for 20 min and then filtered. The filtrate was allowed to stand in air for 17 d, during which time about three-quarters of the original solvent volume evaporated and colourless block-shaped crystals formed at the bottom of the vessel. The crystals were isolated, washed three times with water and dried in a vacuum desiccator using anhydrous CaCl₂ (pure product yield 68.7%). Analysis found: C 50.5, H 3.7, N 3.8%; calculated for C₁₆H₁₄AgFNO₂: C 50.7, H 3.7, N 3.7%.

S3. Refinement

All H atoms were placed in idealized positions and allowed to ride on their parent atoms, with C—H distances of 0.93–0.97 Å and U_iso(H) = 1.2U_eq(C).

Computing details

Data collection: SMART (Bruker, 1998); cell refinement: SMART; data reduction: SAINT (Bruker, 1998); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Sheldrick, 1997); 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. The atom labelled with the suffix A is at the symmetry position (1 − x, 2 − y, 1 − z).
	Fig. 2. The crystal packing of (I), viewed along the a axis. The cross-hatched spheres represent Ag atoms; the diagonal-lined spheres represent O atoms; the dotted spheres represent N atoms.

catena-Poly[[di-µ-benzoato-κ⁴O:O'-disilver(I)]-µ-N,N'- bis(2-fluorobenzylidene)butane-1,4-diamine-κ²N:N']

Crystal data

[Ag2(C7H5O2)2(C18H18F2N2)]	Z = 1
Mr = 758.30	F(000) = 378
Triclinic, p1	Dx = 1.724 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 5.703 (3) Å	Cell parameters from 1624 reflections
b = 10.313 (5) Å	θ = 2.6–23.5°
c = 12.805 (6) Å	µ = 1.39 mm^−1
α = 86.978 (6)°	T = 293 K
β = 84.452 (7)°	Block, colourless
γ = 77.115 (7)°	0.27 × 0.22 × 0.15 mm
V = 730.4 (6) Å^3

Data collection

Bruker SMART CCD area-detector diffractometer	2524 independent reflections
Radiation source: fine-focus sealed tube	1952 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.047
ω scans	θmax = 25.0°, θmin = 2.0°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −6→4
Tmin = 0.705, Tmax = 0.818	k = −10→12
3880 measured reflections	l = −14→15

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)] = 0.080	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.215	H-atom parameters constrained
S = 0.98	w = 1/[σ^2(Fo^2) + (0.1604P)^2] where P = (Fo^2 + 2Fc^2)/3
2524 reflections	(Δ/σ)max < 0.001
190 parameters	Δρmax = 1.86 e Å^−3
0 restraints	Δρmin = −1.84 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	0.75137 (11)	0.91168 (6)	0.50699 (4)	0.0652 (4)
F1	0.8616 (16)	0.7128 (9)	0.9210 (5)	0.116 (2)
N1	0.9338 (12)	0.7175 (7)	0.6085 (5)	0.0612 (16)
O1	0.8060 (10)	1.0757 (6)	0.6018 (5)	0.0657 (14)
O2	0.4124 (10)	1.1708 (7)	0.6162 (5)	0.0757 (17)
C1	0.8822 (17)	0.6933 (9)	0.7067 (7)	0.067 (2)
H1	0.9872	0.6262	0.7411	0.080*
C2	0.6675 (18)	0.7660 (9)	0.7664 (7)	0.068 (2)
C3	0.662 (2)	0.7753 (11)	0.8737 (8)	0.088 (3)
C4	0.462 (3)	0.8432 (16)	0.9346 (11)	0.119 (5)
H4	0.4675	0.8514	1.0062	0.143*
C5	0.261 (3)	0.8967 (14)	0.8869 (12)	0.116 (5)
H5	0.1226	0.9381	0.9271	0.139*
C6	0.256 (2)	0.8913 (11)	0.7785 (11)	0.097 (3)
H6	0.1186	0.9326	0.7457	0.116*
C7	0.4581 (17)	0.8236 (9)	0.7213 (7)	0.070 (2)
H7	0.4534	0.8163	0.6495	0.084*
C8	1.1502 (16)	0.6318 (8)	0.5563 (7)	0.065 (2)
H8A	1.2391	0.5734	0.6078	0.078*
H8B	1.2550	0.6860	0.5213	0.078*
C9	1.0707 (17)	0.5497 (8)	0.4766 (6)	0.065 (2)
H9A	0.9725	0.6098	0.4290	0.078*
H9B	1.2130	0.5024	0.4356	0.078*
C10	0.6218 (13)	1.1569 (7)	0.6407 (6)	0.0528 (17)
C11	0.6576 (13)	1.2485 (7)	0.7235 (5)	0.0484 (16)
C12	0.8733 (17)	1.2292 (9)	0.7694 (7)	0.066 (2)
H12	1.0031	1.1616	0.7472	0.079*
C13	0.8947 (19)	1.3119 (11)	0.8492 (7)	0.080 (3)
H13	1.0382	1.2980	0.8813	0.096*
C14	0.708 (2)	1.4121 (10)	0.8802 (8)	0.082 (3)
H14	0.7223	1.4653	0.9346	0.098*
C15	0.502 (2)	1.4354 (10)	0.8334 (8)	0.080 (3)
H15	0.3781	1.5078	0.8525	0.096*
C16	0.4713 (16)	1.3516 (9)	0.7562 (7)	0.066 (2)
H16	0.3246	1.3654	0.7268	0.079*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ag1	0.0608 (5)	0.0685 (5)	0.0709 (5)	−0.0200 (3)	−0.0106 (3)	−0.0098 (3)
F1	0.130 (6)	0.168 (7)	0.064 (3)	−0.065 (5)	−0.019 (4)	0.007 (4)
N1	0.058 (4)	0.058 (4)	0.067 (4)	−0.010 (3)	−0.006 (3)	−0.001 (3)
O1	0.051 (3)	0.068 (3)	0.081 (4)	−0.016 (3)	0.000 (3)	−0.023 (3)
O2	0.050 (3)	0.102 (5)	0.078 (4)	−0.013 (3)	−0.013 (3)	−0.030 (3)
C1	0.063 (5)	0.072 (5)	0.067 (5)	−0.021 (4)	−0.008 (4)	0.004 (4)
C2	0.070 (6)	0.071 (5)	0.066 (5)	−0.028 (4)	−0.001 (4)	0.000 (4)
C3	0.098 (8)	0.103 (8)	0.077 (6)	−0.051 (7)	−0.005 (6)	−0.005 (6)
C4	0.143 (13)	0.143 (12)	0.093 (8)	−0.087 (11)	0.037 (9)	−0.047 (8)
C5	0.107 (11)	0.119 (11)	0.129 (12)	−0.059 (9)	0.053 (10)	−0.041 (9)
C6	0.071 (7)	0.084 (7)	0.134 (10)	−0.020 (6)	0.010 (7)	−0.007 (7)
C7	0.066 (6)	0.074 (6)	0.074 (5)	−0.025 (4)	0.000 (5)	−0.001 (4)
C8	0.055 (5)	0.063 (5)	0.075 (5)	−0.011 (4)	−0.005 (4)	0.004 (4)
C9	0.069 (5)	0.052 (4)	0.067 (5)	−0.007 (4)	0.014 (4)	−0.008 (3)
C10	0.044 (4)	0.063 (4)	0.055 (4)	−0.018 (3)	−0.003 (3)	−0.001 (3)
C11	0.041 (4)	0.058 (4)	0.051 (4)	−0.020 (3)	−0.001 (3)	−0.004 (3)
C12	0.058 (5)	0.083 (6)	0.062 (5)	−0.026 (4)	−0.006 (4)	−0.008 (4)
C13	0.071 (6)	0.115 (8)	0.070 (5)	−0.047 (6)	−0.024 (5)	−0.005 (5)
C14	0.091 (7)	0.088 (7)	0.076 (6)	−0.038 (6)	0.001 (5)	−0.027 (5)
C15	0.080 (7)	0.079 (6)	0.085 (6)	−0.023 (5)	0.001 (5)	−0.024 (5)
C16	0.060 (5)	0.068 (5)	0.070 (5)	−0.010 (4)	−0.011 (4)	−0.014 (4)

Geometric parameters (Å, º)

Ag1—O2^i	2.206 (6)	C6—H6	0.9300
Ag1—O1	2.227 (5)	C7—H7	0.9300
Ag1—N1	2.417 (7)	C8—C9	1.522 (12)
Ag1—Ag1^i	3.051 (2)	C8—H8A	0.9700
F1—C3	1.357 (14)	C8—H8B	0.9700
N1—C1	1.287 (10)	C9—C9^ii	1.507 (17)
N1—C8	1.472 (10)	C9—H9A	0.9700
O1—C10	1.266 (9)	C9—H9B	0.9700
O2—C10	1.240 (9)	C10—C11	1.514 (10)
O2—Ag1^i	2.206 (6)	C11—C16	1.376 (11)
C1—C2	1.455 (13)	C11—C12	1.384 (11)
C1—H1	0.9300	C12—C13	1.396 (12)
C2—C7	1.376 (13)	C12—H12	0.9300
C2—C3	1.378 (14)	C13—C14	1.355 (14)
C3—C4	1.387 (19)	C13—H13	0.9300
C4—C5	1.35 (2)	C14—C15	1.339 (14)
C4—H4	0.9300	C14—H14	0.9300
C5—C6	1.396 (18)	C15—C16	1.394 (13)
C5—H5	0.9300	C15—H15	0.9300
C6—C7	1.373 (14)	C16—H16	0.9300
O2^i—Ag1—O1	153.9 (3)	N1—C8—H8A	110.0
O2^i—Ag1—N1	103.8 (2)	C9—C8—H8A	110.0
O1—Ag1—N1	101.6 (2)	N1—C8—H8B	110.0
O2^i—Ag1—Ag1^i	73.73 (16)	C9—C8—H8B	110.0
O1—Ag1—Ag1^i	83.45 (15)	H8A—C8—H8B	108.4
N1—Ag1—Ag1^i	137.03 (17)	C9^ii—C9—C8	114.7 (9)
C1—N1—C8	117.5 (7)	C9^ii—C9—H9A	108.6
C1—N1—Ag1	126.3 (6)	C8—C9—H9A	108.6
C8—N1—Ag1	115.4 (5)	C9^ii—C9—H9B	108.6
C10—O1—Ag1	118.5 (5)	C8—C9—H9B	108.6
C10—O2—Ag1^i	134.0 (5)	H9A—C9—H9B	107.6
N1—C1—C2	123.1 (8)	O2—C10—O1	126.2 (7)
N1—C1—H1	118.5	O2—C10—C11	116.0 (7)
C2—C1—H1	118.5	O1—C10—C11	117.8 (7)
C7—C2—C3	116.5 (10)	C16—C11—C12	118.7 (7)
C7—C2—C1	122.8 (8)	C16—C11—C10	119.8 (7)
C3—C2—C1	120.7 (10)	C12—C11—C10	121.4 (7)
F1—C3—C2	117.7 (10)	C11—C12—C13	119.6 (9)
F1—C3—C4	119.2 (12)	C11—C12—H12	120.2
C2—C3—C4	123.1 (13)	C13—C12—H12	120.2
C5—C4—C3	118.1 (13)	C14—C13—C12	120.3 (9)
C5—C4—H4	121.0	C14—C13—H13	119.8
C3—C4—H4	121.0	C12—C13—H13	119.8
C4—C5—C6	121.4 (13)	C15—C14—C13	120.7 (9)
C4—C5—H5	119.3	C15—C14—H14	119.7
C6—C5—H5	119.3	C13—C14—H14	119.7
C7—C6—C5	118.4 (13)	C14—C15—C16	120.3 (10)
C7—C6—H6	120.8	C14—C15—H15	119.8
C5—C6—H6	120.8	C16—C15—H15	119.8
C6—C7—C2	122.4 (10)	C11—C16—C15	120.2 (9)
C6—C7—H7	118.8	C11—C16—H16	119.9
C2—C7—H7	118.8	C15—C16—H16	119.9
N1—C8—C9	108.5 (7)

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