1,3,5-Triaroylbenzenes as Ligands: Synthesis and Characterization of

Three new coordination polymers have been prepared from 1,3,5-tris(4-cyanobenzoyl)benzene and the Ag(I) salts AgOTf, AgBF4, and AgPF6. In each instanc...
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1,3,5-Triaroylbenzenes as Ligands: Synthesis and Characterization of Three New Coordination Polymers from the Tritopic Ligand 1,3,5-Tris(4,4′,4′′-tricyanobenzoyl)benzene and Ag(I)X (X ) OSO2CF3, BF4, or PF6)

CRYSTAL GROWTH & DESIGN 2003 VOL. 3, NO. 3 331-337

F. Christopher Pigge,* Michael D. Burgard, and Nigam P. Rath Department of Chemistry and Biochemistry, University of Missouri-St. Louis, 8001 Natural Bridge Road, St. Louis, Missouri 63121-4499 Received December 1, 2002;

Revised Manuscript Received February 4, 2003

W This paper contains enhanced objects available on the Internet at http://pubs.acs.org/crystal.

ABSTRACT: Three new coordination polymers have been prepared from 1,3,5-tris(4-cyanobenzoyl)benzene and the Ag(I) salts AgOTf, AgBF4, and AgPF6. In each instance, the triaroylbenzene derived ligand serves as a nonchelating bridging unit connecting three different silver ions via coordination to the nitrile moieties. The polymers assembled in the presence of noncoordinating counterions (BF4 and PF6) were found to be topologically similar, and these anions appear to facilitate the generation of channels (approximate dimensions 13 × 17 Å) within the crystalline lattice. The presence of these anions, network interpenetration, and the inclusion of small molecule solvates substantially reduce the overall porosity of these polymers. These results demonstrate the feasibility of constructing crystalline metal-organic coordination polymers from triaroylbenzene building blocks and also provide a starting point for the design of more robust and potentially functional materials. Introduction The synthesis and characterization of novel metalorganic networks has emerged as an important focus of contemporary interdisciplinary research efforts at the intersection of materials/polymer chemistry and traditional inorganic/organic endeavors.1 Interest in this topic stems from the belief that functional materials possessing a range of desirable properties (such as porosity, magnetism, conductance, and nonlinear optical behavior) will result once the ability to engineer supramolecular architectures from molecular building blocks has been refined to a level that permits the rational design of complex multicomponent assemblies. Indeed, judicious combination of geometrically rigid multitopic organic ligands with metal ions that possess well-defined coordination numbers and geometries has resulted in the successful construction of various discrete 2-D and 3-D structures (e.g., molecular polygons, polyhedra, capsules, etc.).2-6 Using a similar approach, it has also proven possible to design and construct infinite arrays of metal-organic networks as well.7,8 However, the phenomenon of network interpenetration coupled with the (at times) significant influence of solvent and metal counterion continue to complicate efforts aimed at preparing functional crystalline coordination polymers with predetermined properties. Given the current state-of-the-art in crystal engineering of coordination polymers, a great deal of effort remains directed at identifying organic ligands capable of mediating network assembly via coordination to appropriate metal ions. A widely utilized approach entails preparing and structurally characterizing a * E-mail: [email protected]; Phone: (314) 516-5340; Fax: (314) 516-5342.

range of solid-state networks from a given ligand/metal pair while varying reaction parameters such as solvent and counterion. In this manner, characteristic trends in polymer structure can be identified and subsequently used to aid design of future generation networks as part of an overall iterative synthetic strategy. Typically, rigid multitopic nonchelating ligands are employed to provide a potential basis for predicting a priori network topology and to maintain crystalline integrity. Nitrile-derived multitopic ligands are well established as versatile organic building blocks amenable to incorporation into a range of composite metal-containing assemblies. Organic nitriles are easily accessible (either commercially or synthetically) and form tractable coordination complexes with a number of different transition metal ions. In particular, combinations of nitrile ligands and silver(I) salts have yielded a wealth of structurally and functionally intriguing metal-organic networks. A sampling of nitrile ligands used in this regard is provided in Chart 1 and includes examples of ditopic ligands (L1-L2),9,10 tritopic ligands (L3-L6),11-14 and tetratopic ligands (L7-L8).12,15 A plethora of intricate aesthetically pleasing 2-D and 3-D crystalline coordination polymers of silver have been obtained from these (and other)16-23 nitrile-based ligands, including porous networks that exhibit reversible solvent inclusion and guest exchange.13,14,24 Derivatives of 1,3,5-tribenzoylbenzene (1) are easily prepared via amine-catalyzed cyclotrimerization of aryl ethynyl ketones.25 As part of a larger effort aimed at utilizing this intriguing architecture in a number of supramolecular chemistry applications,26 previous work in this laboratory demonstrated the propensity of certain substituted triaroylbenzenes to form crystalline inclusion complexes with various small molecule (sol-

10.1021/cg025614p CCC: $25.00 © 2003 American Chemical Society Published on Web 03/01/2003

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vent) guests.27 X-ray analyses of these crystalline composites revealed the presence of solvent-filled channels or voids within the host lattice and, in some instances, a network of inter-host and host-guest C-H‚ ‚‚O hydrogen bonds. In view of the relatively rigid bulky polyaromatic nature of 1 and the ability of substituted congeners to enclathrate smaller molecules, the syntheses and structural characterization of metal-organic networks incorporating the triaroylbenzene framework were undertaken. At the outset, it was envisioned that coordination bonds (in place of weak hydrogen bonds) would serve to orient individual triaroylbenzene constituents such that crystalline voids and/or channels may result. Moreover, the limited flexibility of the triaroylbenzene framework should preclude metal-ligating groups positioned on the pendant phenyl rings from participating in the formation of chelated complexes. Toward this end, three new coordination polymers have been prepared and structurally characterized from the tritopic triaroylbezene ligand 2 and AgX (X ) OTf, BF4, PF6).

Results and Discussion Synthesis. The ligand 2 was prepared in a straightforward fashion starting from p-cyanobenzaldehyde as illustrated in Scheme 1. Addition of ethynylmagnesium bromide followed by Jones oxidation of the resulting

Pigge et al. Scheme 1

alcohol gave p-cyanophenyl ethynyl ketone 3 in 63% overall yield. Diethylamine-catalyzed alkyne trimerization afforded ligand 2 with complete regioselectivity in 73% yield. A crystalline coordination polymer (4) of stoichiometry [Ag‚2‚MeNO2][OTf] was obtained by slow diffusion of ether into a nitromethane solution of 2 and excess AgOTf. Additional metal-organic networks (5 and 6) were prepared by simply cooling an acetone solution of 2 and excess AgBF4 or AgPF6. The syntheses of 4-6 are reproducible, but attempts to prepare various other Ag(I) networks from alternative silver salts (AgNO3, AgOAc, AgIO3, Ag2SO4) using similar procedures have thus far been unsuccessful. The crystalline samples obtained in the course of this study were neither light nor air sensitive but became opaque upon removal from the mother liquor. The new coordination polymers were characterized by X-ray diffractometry and elemental analysis. Structure of {[Ag‚2‚MeNO2][OTf]}∞ (4). The coordination polymer 4 crystallizes in the space group Cc, and all silver ions and triaroylbenzene ligands are equivalent. Each silver ion adopts a four-coordinate distorted tetrahedral or “sawhorse” geometry. The coordination sphere consists of three nitrile moieties from three different ligands and a triflate anion (Figure 1).

Figure 1. Coordination sphere of Ag in 4. Selected bond distances (Å) and angles (°): N(1)-Ag(1) ) 2.511; N(2A)-Ag(1) ) 2.190; N(3B)-Ag(1) ) 2.189; O(1)-Ag(1) ) 2.605; N(1)Ag(1)-O(1) ) 116.74; N(2A)-Ag(1)-N(3B) ) 159.74; N(2A)Ag(1)-N(1) ) 90.84.

Silver-N distances between the two trans-oriented nitrile ligands are relatively short (2.190 and 2.189 Å), while the Ag-N(1) and Ag-O(1) bond lengths are longer (2.511 and 2.605 Å, respectively). The nitrile groups trans to each other are nearly linear with respect to the Ag center (N(2)-Ag-N(3) angle ) 159.74°) while the N(1)-Ag-O(1) angle is 116.74°. The N(1)-Ag-N(2) angle is 90.84°. Each tricyanobenzoylbenzene ligand bridges three Ag(I) ions while adopting a conformation in which two carbonyl groups are oriented toward one face of the central 1,3,5-trisubstituted arene with the remaining carbonyl directed toward the opposite face. The three silver ions bridged by a single ligand are separated by distances of 9.557, 18.570, and 18.862 Å. Examination of the crystal packing down b clearly reveals the presence of small holes within the lattice

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Figure 3. Basic packing arrangement observed in 5. Silver centers are shown as large spheres. Hydrogens, BF4 counterions, and noncoordinated acetone molecules omitted for clarity.

Figure 2. Packing diagram of 4 down b showing crystalline voids that are occupied by coordinated triflate ions and MeNO2 solvate molecules (not all MeNO2 molecules are shown). W A rotatable 3D image of the extended packing of 4 in PDB format suitable for viewing using the CHIME plug-in is available.

(Figure 2 and the web-enhanced file). These spaces are almost completely filled by the coordinated triflate counterions and included nitromethane molecules. In addition to typical van der Waals attractions, each nitromethane “guest” appears to participate in two solidstate C-H‚‚‚O hydrogen bonding interactions. The first of these involves an aromatic hydrogen positioned ortho to a nitrile moiety and an oxygen atom of nitromethane (H-O distance ) 2.569 Å, C-H‚‚‚O angle ) 163.4°). The second H-bonding interaction has the methyl group of MeNO2 serving as an H-bond donor to a carbonyl oxygen atom (H-O distance ) 2.528 Å, C-H‚‚‚O angle ) 153.6°, CdO‚‚‚H angle ) 125.3°). It should be noted, however, that on the basis of theoretical calculations MeNO2 is expected to be a poor H-bond donor.28 Calculations performed using the PLATON program29 revealed virtually no solvent accessible void space within the crystal lattice of 4. Furthermore, theoretically removing the MeNO2 molecules results in generation of only ∼315 Å3 (10% of cell volume) of solvent accessible void space. Thus, the combination of ligand conformation and coordinating counterion appears to render 4 unsuitable for elaboration into porous materials. Structure of {[Ag‚2‚(acetone)1.67][BF4]}∞ (5). The coordination polymer assembled from 2 and AgBF4 is topologically much more complex than the previously described structure 4. Network 5 possesses four crystallographically unique silver ions [Ag(1)-Ag(4)], and the tris(cyanobenzoylbenzene) ligand is present in three distinct conformational arrangements. In contrast to the solid-state structure observed in 4, all the triaroylbenzene ligands in 5 adopt a gross conformation in which the three carbonyl oxygen atoms are oriented toward the same face of the central arene ring and the three cyanophenyl moieties are directed toward the opposite face. Three crystallographically distinct ligands result from slight differences in the relative orientation of the cyanophenyl rings. In addition, one ligand is disordered over two sites (vide infra). One included acetone molecule serves as a coordinating ligand, while the remaining fraction is present as a crystalline solvate.

Figure 4. Coordination environments of the Ag ions and bridging arrangements of the triaroylbenzene ligands in 5. The cyanophenyl ring incorporating N(33A) and N(33B) is disordered over two sites.

The four unique silver ions are arranged in two rows (A and B) that form a repeating pattern ...AABAAB... when viewed down the b axis (Figure 3). The tritopic organic ligands occupy positions above and below the mean plane defined by the silver ions and serve to bridge adjacent metal centers within the same row, as well as silver ions in neighboring rows. Such a bonding arrangement gives rise to a corrugated sheet topology. Rows “A” are composed of two alternating four-coordinate silver ions [Ag(1) and Ag(2)] while rows “B” consist of alternating four-coordinate Ag(3) and Ag(4) ions that sit on inversion centers. The crystalline pores present between each row of silver are partially filled by BF4 counterions and noncoordinated acetone solvate molecules (not shown). The coordination sphere of Ag(1) (shown in Figure 4) consists of four nitrile ligands arranged in a square planar array. The Ag-N distances range from 2.151 Å [Ag(1)-N(11)] to 2.794 Å [Ag(1)-N(33B)]. The cyanophenyl group incorporating N(33B) is disordered over two sites and also serves as a ligand toward an adjacent Ag(2) ion in the same row (Ag(2)-N(33A) distance ) 2.519 Å). The other two “arms” of this disordered ligand are attached to Ag(1) and Ag(2) ions in an adjacent row “A”, thereby giving rise to the ...AABAAB... pattern depicted in Figure 3. The remaining two triaroylbenzene ligands that complete the coordination sphere of Ag(1) [i.e., N(11) and N(21)] serve to connect rows “A” and “B”. The Ag-Ag distance in rows “A” alternates between 7.824 and 7.916 Å, while the distance between Ag(3) and Ag(4) (the constituents of rows “B”) is a constant 7.851 Å. As indicated in Figures 3 and 4, Ag(1) in one row is flanked by another Ag(1) ion and a Ag(3) ion in adjacent rows. The distances between these metal centers are 17.323 and 17.199 Å, respectively. Similarly, each Ag(2) is flanked by another Ag(2) and a Ag(4) at distances of 16.626 and 17.543 Å, respectively. The distance

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Figure 5. (a, b) Two views of network interpenetration in the coordination polymer 5. Rotation of panel a 90° along the axis normal to the plane of the paper provides panel b. Silver ions are depicted as large spheres. BF4 ions and acetone solvates are not shown. W A rotatable 3D image of the extended packing of 5 in PDB format suitable for viewing using the CHIME plug-in is available.

between opposing centroids of the 1,3,5-trisubstituted arene rings in the bridging organic ligands shown in Figure 3 is ∼13.5 Å; thus, the channels evident in Figure 3 possess rather sizable two-dimensional openings of approximately 17 × 13 Å. As can be seen in Figure 5 , however, interpenetration of a neighboring polymer sheet (depicted in blue) reduces the effective dimensions of the incipient channels (see the web-enhanced file linked to Figure 5 for a rotatable rendering). Compared to the AgOTf-based coordination polymer 4, the crystalline lattice of 5 potentially possesses greater porosity (despite network interpenetration). Indeed, theoretically removing the noncoordinating acetone molecules of solvation and the BF4 anions results in generation of solvent accessible void space totaling 26% of the overall crystal volume.29 Obviously it is impossible to achieve this level of void space in the current system due to the unavoidable presence of counterions and the instability of the solid-state network (crystallinity is lost upon prolonged removal of 5 from the mother liquor). Structure of {[Ag‚2‚(acetone)2][PF6]}∞ (6). Considering that identical methods of preparation involving silver salts with noncoordinating counterions of comparable size were employed in the synthesis of 5 and 6, one might anticipate a great deal of solid-state structural similarity between these two materials.30 It came as no surprise, then, to find many common topological features in these two metal-organic networks. Interestingly, it appears that the local bonding arrangement in 6 also resembles that observed in 4 with a coordinated acetone molecule taking the place of the triflate ligand in the coordination sphere of silver (the remaining acetone is present as a crystalline solvate). As shown in Figure 6, the geometry about the fourcoordinate Ag(1) atom can be described as distorted tetrahedral or “sawhorse.” The silver is coordinated to three nitrile ligands from three different triaroylbenzenes and an acetone solvent molecule. The longest bond distance between a ligating atom and the silver ion is 2.393 Å (N(3B)-Ag(1) distance). The N(1)-Ag(1)-N(2A) angle is nearly linear (159.12°), while the N(3B)-Ag-

Figure 6. Coordination environment about the silver ion in polymer 6. The silver center is disordered over two sites (50% occupancy). Selected bond lengths (Å) and angles (°): Ag(1)N(1) ) 2.225; Ag(1)-N(2A) ) 2.195; Ag(1)-N(3B) ) 2.393; Ag(1)-O(4) ) 2.170; N(1)-Ag(1)-N(2A) ) 159.12; N(1)-Ag(1)N(3B) ) 100.69; N(1)-Ag(1)-O(4) ) 85.87; N(3B)-Ag(1)-O(4) ) 67.80; Ag(1′)-N(1) ) 2.207; Ag(1′)-N(2A) ) 2.246; N(1)Ag(1′)-N(2A) ) 154.91.

(1)-O(4) angle is 67.80°. It is noteworthy that the single crystallographically unique silver ion in 6 was observed to be disordered over two sites (50% occupancy at each site). The “disordered” silver Ag(1′) was determined to be ligated in a two-coordinate linear arrangement as evidenced by N(1)-Ag(1′) and N(2A)-Ag(1′) distances of 2.207 and 2.246 Å, respectively. The relevant angle about these three atoms is 154.91°. The distances between O(4) and N(3B) to Ag(1′) was deemed to be too long for bonding interactions (2.642 and 3.277 Å, respectively). The one crystallographically distinct triaroylbenzene ligand adopts a conformation similar to those observed in 5, wherein all three carbonyl groups are oriented toward one face of the central trisubstituted arene ring. In terms of gross topology, AgPF6-based polymer 6 closely resembles the network obtained from AgBF4 (i.e., 5). The silver ions in 6 are arranged in parallel rows, and each row is connected to the two adjacent rows via triaroylbenzene bridging ligands, similar to what is

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multitopic ligand 2 and various silver salts. While the specific silver-based networks prepared in the course of this investigation are of limited stability and exhibit considerable crystalline network interpenetration, these results provide the incentive for continued studies as suitable modification of the ligand framework and/or metal ion so as to obviate the need for discrete anionic counterions while at the same time providing for a more robust network may lead to truly functional (e.g., porous) materials and/or supramolecular capsules. The synthetic accessibility of functionalized triaroylbenzene derivatives should greatly facilitate realization of these goals, and studies along these lines are in progress. Experimental Section

Figure 7. Two views of the extended packing in 6. A single PF6 anion and an acetone molecule of solvation are included. W A rotatable 3D image of the extended packing of 6 in PDB format suitable for viewing using the CHIME plug-in is available.

shown in Figure 3. The Ag-Ag distance within a row is 7.927 Å and the distance between silver ions in adjacent rows is 17.776 Å. As was the case in 5, network interpenetration is also observed in 6 as shown in Figure 7 (see the web-enhanced file for a rotatable 3D image). In addition, the noncoordinated acetone molecules of solvation and the PF6 counterions occupy ∼27% of the total crystal volume.29 To rationalize the differences between the crystalline networks of 5 and 6, it is speculated that the slightly larger PF6 anion is better able to template the crystal packing observed in 6 as compared to the smaller BF4 anion present in 5.30 Indeed, all the triaroylbenzene ligands as well as the Ag(I) ions in 6 are crystallographically equivalent (although the silver centers are disordered over two sites), giving rise to a regular and well-ordered packing arrangement that provides just enough space to accommodate the PF6 anions. Such a packing arrangement appears to be incompatible with the smaller BF4 ion. Consequently, the flexible organic ligand adopts several different solid-state conformations and the silver ions exhibit varying coordination environments to achieve a tractable crystalline framework. In line with this rationale, it is perhaps noteworthy that the PF6 anions present in 6 are not disordered in the solid state, whereas the BF4 anions present in 5 are. Thus, while features common to PF6 and BF4 (noncoordinating, similar shape) result in formation of superficially comparable coordination polymers 5 and 6, differences in size appear to contribute to subtle differences in crystalline structure. Conclusions In conclusion, this study demonstrates the feasibility of constructing novel three-dimensional crystalline coordination polymers from a triaroylbenzene-derived

All commercially available reagents and solvents were used as received unless otherwise noted. Diethylamine was distilled from CaH2 and stored over KOH. Toluene was distilled from CaH2. All reactions were performed in oven-dried glassware under an Ar atmosphere unless otherwise indicated. Flash column chromatography was performed using Natland International silica gel 60 (200-400 mesh). 1H- and 13C NMR spectra were obtained using a Varian Unity 300 spectrometer and are referenced to residual CHCl3. IR spectra were obtained using a Perkin-Elmer 1600 FT-IR. Melting points were determined using a Thomas-Hoover melting point apparatus and are uncorrected. Elemental analyses were performed by Atlantic Microlabs, Norcross, GA. Preparations. 4-Cyanophenyl Ethynyl Ketone (3). A round-bottom flask was charged with 2.00 g (15.3 mmol) p-cyanobenzaldehyde and placed in an ice bath. A solution of ethynylmagnesium bromide (0.5 M in THF, 18.3 mmol, 36.6 mL) was added via syringe and the resulting brownish-red reaction mixture was allowed to warm to room temperature and maintained for 2 h. The reaction was quenched with H2O and saturated aq. NH4Cl solution. The mixture was diluted with ether and the layers were separated. The aqueous layer was re-extracted with additional ether and the combined ether solutions were washed with H2O and brine. After the sample was dried over anhydrous MgSO4, the mixture was filtered and concentrated to afford a dark oil. Purification by flash column chromatography (3:1 hexanes/EtOAc) gave the desired propargylic alcohol as a pale yellow solid (2.06 g, 86%). Without further characterization, this material was dissolved in ∼15 mL of acetone and cooled to 0 °C. A solution of the Jones reagent was added dropwise via Pasteur pipet until the red color indicative of Cr(VI) salts persisted. The reaction was quenched by addition of excess 2-propanol. After diluting the reaction mixture with ether, the insoluble Cr(III) salts were removed by filtration through a pad of Celite. The filtrate was washed sequentially with H2O, saturated aq. NaHCO3 solution, H2O, and brine and then dried over anhydrous MgSO4. Filtration and evaporation of the solvent gave a yellow solid that was purified by recrystallization from hexanes/ether. Yield - 1.50 g (74%, 63% over two steps); mp 110-111 °C; 1H NMR (300 MHz, CDCl3) δ 3.58 (1 H, s), 7.83 (2 H, d, J ) 8.7 Hz), 8.27 (2 H, d, J ) 8.7 Hz). 13C NMR (75 MHz, CDCl3) δ 79.57, 82.55, 117.53, 117.62, 129.82, 132.44, 138.63, 175.52. IR (thin film) ν (cm-1) 3322, 2098, 1642. Anal. Calcd for C10H15NO: C 77.41; H 3.25; N 9.03. Found: C 77.14; H 3.43, N 8.93. 1,3,5-Tris(4,4′,4′′-tricyanobenzoyl)benzene (2). To a solution of 3 (1.00 g, 6.45 mmol) in ∼10 mL of toluene was added Et2NH (1 drop). The yellow solution was then heated to reflux for 48 h. After the sample was cooled, the toluene was evaporated under reduced pressure and the resulting brown residue was dissolved in EtOAc. The organic solution was washed with H2O, 10% aq. HCl solution, and brine and then dried over anhydrous MgSO4. Filtration and removal of the solvent gave a dark solid that was purified first by flash column chromatography (1:1 hexanes/EtOAc) followed by recrystallization (hexanes/EtOAc). Yield - 0.73 g (73%); mp 211-213 °C. 1H NMR (300 MHz, CDCl3) δ 7.84 (6 H, d, J )

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8.1 Hz), 7.92 (6 H, d, J ) 8.1 Hz), 8.39 (3 H, s). 13C NMR (75 MHz, CDCl3) δ 116.78, 117.46, 130.13, 132.52, 134.32, 137.46, 139.22, 192.53. IR (thin film) ν (cm-1) 2231, 1670. Anal. Calcd for C30H15N3O3: C 77.41; H 3.25; N 9.03. Found: C 77.54; H 3.41; N 8.87. {[Ag‚2‚MeNO2][OTf]}∞ (4). The ligand 2 (20.0 mg, 0.043 mmol) was dissolved in 2.0 mL of nitromethane in a 20 mL sample vial equipped with a Teflon-lined screw cap. A solution of AgOTf (55.2 mg, 0.215 mmol) in 2.0 mL of MeNO2 was added and the vial was sealed. The mixture was heated in a 120 °C oil bath for 45 min, then while still warm gravity filtered through coarse filter paper into a clean sample vial and allowed to cool to room temperature. Slow diffusion of ether into this solution over ∼10 days resulted in deposition of 4 as pale yellow X-ray quality crystals. No attempt was made to exclude air or moisture throughout this process. The crystals were collected by filtration and dried under vacuum (0.50 Torr, 12 h). Crystal yield - 17.7 mg (53%); mp 172-176 °C (dec). Anal. Calcd for C32H18AgF3N4O8S: C 49.06; H 2.32; N 7.15. Found: C 48.80; H 2.23; N 7.18. {[Ag‚2‚(acetone)1.67][BF4]}∞ (5). A solution of AgBF4 (25.0 mg, 0.128 mmol) in 1.5 mL of acetone was added to a solution of 2 (20.0 mg, 0.043 mmol) in 1.5 mL of acetone in a 20 mL sample vial. The reaction solution was briefly warmed on a hot plate (5 min) then filtered through a cotton plug into a clean 20 mL sample vial. The vial was capped and placed in the freezer (-30 °C). Colorless X-ray quality crystals of 5 formed over 7 days. The crystals were collected by vacuum filtration. Yield - 22.5 mg (69%). An analytical sample was obtained by further drying the crystals under vacuum (0.5 Torr, 12 h), which resulted in partial loss of acetone solvate; mp 168-175 °C (dec). Anal. Calcd for C33.75H22.5AgBF4N3O4.25: C 55.32; H 3.10; N 5.73. Found: C 55.11; H 3.33; N 5.56 ([Ag‚ 2‚(acetone)1.25][BF4]). {[Ag‚2‚(acetone)2][PF6]}∞ (6). Using the procedure described for the preparation of 5, 10.9 mg (0.023 mmol) of 2 and 17.5 mg (0.069 mmol) of AgPF6 afforded 6 (7.4 mg, 38%) as colorless needles. An analytical sample was obtained by filtration followed by drying under vacuum (0.5 Torr, 12 h), which resulted in loss of one acetone molecule of solvation; mp 181-183 °C (dec). Anal. Calcd for C33H21AgF6N3O4P: C 51.05; H 2.73; N 5.41. Found: C 50.75; H 3.10; N 5.08 ([Ag‚ 2‚(acetone)][PF6]). X-ray Crystallography. Crystals of appropriate dimensions were mounted on glass fibers in random orientation. Preliminary examination and data collection were performed using a Bruker SMART charge coupled device (CCD) detector system single-crystal X-ray diffractometer using graphite monochromated Mo KR radiation (λ ) 0.71073 Å) equipped with a sealed tube X-ray source. Preliminary unit cell constants were determined with a set of 45 narrow frames (0.3° in $) scans. Typical data sets consisted of 3636 frames of intensity data collected with a frame width of 0.3° in $ and counting time of 15 to 30 s/frame at a crystal-to-detector distance of 4.950 cm. The double pass method of scanning was used to exclude any noise. The collected frames were integrated using an orientation matrix determined from the narrow frame scans. SMART and SAINT software packages were used for data collection and data integration.31 Analysis of the integrated data did not show any decay. Final cell constants were determined by global refinement of xyz centroids of threshold reflections from the complete data set. Collected data were corrected for systematic errors using SADABS based on the Laue symmetry using equivalent reflections.32 Structure solution and refinement were carried out using the SHELXTL-PLUS software package.33 The structures were solved by direct methods and refined successfully in the space groups Cc, P21/c and P21 for 4, 5, and 6, respectively. Full matrix least-squares refinement was carried out by minimizing Σw(Fo2 - Fc2)2. The non-hydrogen atoms were refined anisotropically to convergence. The hydrogen atoms were treated using appropriate riding models (AFIX m3). Crystalline homogeneity was established by obtaining unit cell dimensions for at least five randomly chosen crystals from two independently prepared samples of each coordination polymer.

Pigge et al. In the case of 5, one of the ligands is disordered. The disorder was modeled with partial occupancy of 56:44%. Several data sets were collected from different preparations of 6, and all crystals were partially twinned. Even though the structure can be solved in the centrosymmetric space group P21/m (this is also suggested by PLATON, ignoring some mismatched and disordered atoms), the refinement was poor in this space group. Therefore, P21 was chosen as the space group for this compound. Also, the Ag(I) position is disordered over two sites around a pseudo inversion center of the centrosymmetric P21/m space group. The Ag was refined as 50% occupancy in two disordered positions. Complete crystallographic details have been deposited with the Cambridge Crystallographic Data Center (CCDC reference numbers 194225, 194226, and 194227). Crystal Data for 4. C32H18AgF3N4O8S, M ) 783.43, monoclinic, space group Cc, a ) 17.4002(13), b ) 11.1573(7), c ) 17.4202(13) Å, β ) 113.479(5)°, V ) 3101.9(4) Å3, Z ) 4, Dcalc ) 1.678 g cm-3, T ) 223(2) K, µ(Mo-KR) ) 0.795 mm-1, 25 206 reflections collected of which 7324 were independent (Rint ) 0.032), all non-hydrogen atoms were refined anisotropically using full matrix least squares on F2 to give R1 ) 0.0394 and wR2 ) 0.0799. Crystal Data for 5. C105H75Ag3B3F12N9O14, M ) 2270.78, monoclinic, space group P21/c, a ) 25.5147(8), b ) 15.7026(6), c ) 28.2414(9) Å, β ) 113.896(2)°, V ) 10344.9(6) Å3, Z ) 4, Dcalc ) 1.458 g cm-3, T ) 218(2) K, µ(Mo-KR) ) 0.650 mm-1, 179 124 reflections collected of which 18 226 were independent (Rint ) 0.0000), all non-hydrogen atoms were refined anisotropically using full matrix least squares on F2 to give R1 ) 0.0776 and wR2 ) 0.2353. Crystal Data for 6. C36H27AgF6N3O5P, M ) 834.45, monoclinic, space group P21, a ) 8.1274(2), b ) 15.7754(6), c ) 14.0542(5) Å, β ) 103.267(2)°, V ) 1753.84(10) Å3, Z ) 2, Dcalc ) 1.580 g cm-3, T ) 140(2) K, µ(Mo-KR) ) 0.699 mm-1, 16 791 reflections collected of which 7629 were independent (Rint ) 0.0213), all non-hydrogen atoms were refined anisotropically using full matrix least squares on F2 to give R1 ) 0.0700 and wR2 ) 0.1988.

Acknowledgment. Acknowledgment is made to the donors of the Petroleum Research Fund, administered by the American Chemical Society, for support of this research (ACS PRF# 37468-AC4). Supporting Information Available: A crystallographic information file (CIF) with data for 4-6. The information is available free of charge via the Internet at http://pubs.acs.org.

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