Silver-Dabco Coordination Networks with Distinct Carbaborane

Article pubs.acs.org/crystal

Silver-Dabco Coordination Networks with Distinct Carbaborane Anions: Investigating Ag···H−B and Ag···I−B Interactions Luís Cunha-Silva,*,†,‡ Michael J. Carr,† John D. Kennedy,† and Michaele J. Hardie*,† †

School of Chemistry, University of Leeds, Leeds LS2 9JT, U.K. REQUIMTE & Department of Chemistry and Biochemistry, Faculty of Sciences, University of Porto, 4169-007 Porto, Portugal

‡

S Supporting Information *

ABSTRACT: A novel series of metal−organic frameworks (MOFs) based on Ag(I) and the nitrogen-bridging ligand 1,4diazabicyclo[2.2.2]octane (dabco) along with the incorporation of distinct carbaborane anions were synthesized and isolated as crystalline materials. Single-crystal X-ray diffraction analysis unveiled novel materials formulated as [Ag(dabco)][Cobdc] (1), [Ag(dabco)(PhCB9H9)] (2), [Ag(dabco)(PhCB9H8I)] (3), and [Ag(dabco)(PhCB11H5I6)] (4), which were further characterized by Fourier-transform infrared spectroscopy and elemental analysis. Interestingly, despite the use of distinct carbaborane anions, all the materials feature one-dimensional (1D) coordination networks with most of the bulky anions, particularly all the phenyl-carbaborane anion [PhCB9H9]−, [PhCB9H8I]−, and [PhCB11H5I6]−, incorporated in the coordination networks through Ag···H−B coordinative interactions or Ag···I−B coordination bonds. However, the influence of the distinct carbaborane anions is clearly reflected in the coordination features of Ag(I) centers, since all of them are engaged in different combinations of interactions (coordination bonds Ag−N and Ag−I and both coordinative or electrostatic Ag···H−B interactions) and in the overall characteristics of the 1D coordination networks.

■

INTRODUCTION In the last two decades, the research and development of metal−organic frameworks (MOFs), also designated as coordination polymers or coordination networks, have generated a remarkable progress and high impact in the scientific community.1−10 Initially, the research development of MOFs was almost exclusively related to their unprecedented structural features, but presently, it is mostly associated with their notable potential applicability in diverse technological and industrial areas, such as gas adsorption and capture/ storage,11−15 heterogeneous catalysis,16−20 biomedicine,21−23 nanotechnology,24−27 and sensors.28−30 MOFs are coordination materials with infinite multidimensional (one-, two-, or three-dimensional: 1D, 2D, or 3D) crystalline structures, which depend on several parameters, mainly the coordination requirements of the metal centers, the nature of the multifunctional ligands or the counterions. Consequently, a minor adjustment in any of these parameters potentiates the formation of a considerable number of novel MOF materials with unprecedented extended frameworks. Carbaborane anions, often named carborane anions, are Cand B-based cage cluster compounds with acidic C−H groups with potential to be engaged in weak hydrogen-bonding interactions and/or to act as very weakly coordinating anions. Furthermore, carbaborane compounds may be involved in weaker hydrogen interactions, sometimes described as “agostic” interactions, with diverse metal centers.31−41 In the sequence of © XXXX American Chemical Society

our scientific interest in crystalline supramolecular chemistry, we have been investigating the influence of carbaborane anions on the structural features of coordination networks, as well as the nature of their interactions within the structures of MOF materials.42−52 In recent studies, we reported a series of Ag(I) coordination complexes (either discrete, 1D, 2D, or 3D), incorporating different carbaborane anions and using distinct nitrogen bridging ligands such as alkane-dinitriles [NC(CH2)nCN, where n = 1−6], pyrazine (pyz), 4,4′-bipyridine (bpy), and 2,3-bis-(pyridyl)pyrazine (bppz).46,47,51,52 Herein, the nitrogen-bridging ligand 1,4-diazabicyclo[2.2.2]octane (C6H12N2, dabco) was used in the synthesis of a series of novel Ag(I) coordination networks, incorporating different carbaborane monoanions: [Cobdc]− {Cobdc = cobalt(III) bis(dicarbollide) anion, [Co(C2B9H11)2]−} [PhCB9H9]−, [PhCB9H8I]−, and [PhCB11H5I6]− (Scheme 1). The new MOF materials were formulated as [Ag(dabco)][Cobdc] (1), [Ag(dabco)(PhCB9H9)] (2), [Ag(dabco)(PhCB9H8I)] (3), and [Ag(dabco)(PhCB11H5I6)] (4) on the basis of their respective crystal structure analyses and were further characterized by vibrational spectroscopy and elemental CHN analysis. All the materials featured 1D MOF structures. Additionally, the existence of hydrogen-to-metal interactions Received: April 10, 2013 Revised: May 8, 2013

A

dx.doi.org/10.1021/cg4005328 | Cryst. Growth Des. XXXX, XXX, XXX−XXX

Crystal Growth & Design

Article

corresponding monoacids was performed according to the procedure recently reported.49 Ag[Co(C2B9H11)2] (AgCobdc) was prepared from the commercially available Na+ salt {Na[Co(C2B9H11)2]}, Aldrich, 99%}, following the method described in the literature.54 Infrared (IR) spectra were recorded on the solid phase Perkin-Elmer Spectrum One spectrometer, and the elemental CHN analyses were performed in the University of Leeds microanalytical laboratory. Preparation of the Coordination Networks. [Ag(dabco)][Cobdc] (1). AgCobdc (6.6 mg, 15.2 μmol) was dissolved in a mixture of acetonitrile (MeCN, 1.0 mL) and 2,2,2-trifluorethanol (CF3CH2OH, 1.0 mL). The bridging ligand dabco (3.4 mg, 30.3 μmol) was dissolved separately in the mixture of MeCN/CF3CH2OH (1.0 mL/1.0 mL), and this solution was added to the AgCobdc solution. The final mixture was left to slowly evaporate in a controlled process, leading to the formation of orange crystalline material. Yield relative to AgCobdc: 5.9 mg, 72%. Elemental Analysis (EA) calculated for C10H34AgB18CoN2: C, 22.09; H, 6.31; N, 5.15. EA found: C, 22.25; H, 6.25; N, 5.10. Selected IR (solid phase, ν/cm−1): 3036s, 2962w, 2892w, 2513s, 1464m, 1378m, 1289w, 1234w, 1200m, 1141m, 1113m, 1110m, 1081w, 1014m, 988m, 925m, 884w, 839w, 786m, 747m, 685m, 645w, 616m, 599w, 581w, 565w, 527w. [Ag(dabco)(PhCB9H9)] (2). Ag(PhCB9H9) (7.1 mg, 23.3 μmol) was dissolved in MeCN (2.0 mL), while the dabco (6.4 mg, 57.1 μmol) was dissolved separately also in MeCN (2.0 mL). The two solutions were mixed carefully and left to evaporate in a controlled mode. Colorless single crystals were

Scheme 1. Schematic Representations of the Carbaborane Anions with Distinct Structures Used in the Preparation of the MOF Materials: (a) [Cobdc]−, (b) [PhCB9H9]−, (c) [PhCB9H8I]−, and (d) [PhCB11H5I6]−a

a

Unlabelled vertices are boron vertices.

of type Ag···H−B in the silver coordination centers was carefully evaluated, and the influence of the distinct carbaborane anions in the structures of the MOF materials was investigated.

■

EXPERIMENTAL SECTION Materials and Methods. 1,4-diazabicyclo[2.2.2]octane (C6H12N2, dabco) (Aldrich, ≥99%) and all the AR grade solvents were used as received from the commercial suppliers without further purification. Syntheses of the [NEt4]+ salts of [PhCB9H9]−, [PhCB9H8I]−, and [PhCB9H5I6]− were previously reported,53 and their conversion to the respective Ag(I) salts by the metathesis reaction with AgNO3 through their

Table 1. Details of the Crystal Data Collection and Refinement Details for [Ag(dabco)][Cobdc] (1),[Ag(dabco)(PhCB9H9)] (2), [Ag(dabco)(PhCB9H8I)] (3), and [Ag(dabco)(PhCB11H5I6)] (4)

formula formula weight temperature (K) crystal type crystal size (mm) crystal system space group a (Å) b (Å) c (Å) α (°) β (°) γ (°) volume (Å3) Z ρcalc (g cm−3) μ (mm−1) θ range (°) index ranges

collected reflections independent reflections final R indices [I > 2σ(I)] final R indices (all data) largest difference peak and hole (eÅ−3)

1

2

3

4

C10H34AgB18CoN2 543.77 150(2) orange prism 0.27 × 0.10 × 0.07 monoclinic Cc 6.9544(5) 29.4636(18) 11.2390(5) 90 92.817(2) 90 2300.1(2) 4 1.570 1.576 3.88 − 28.28 −9 ≤ h ≤ 8 −39 ≤ k ≤ 39 −19 ≤ l ≤ 19 21717 5537 (Rint = 0.0181) R1 = 0.0138 wR2 = 0.0394 R1 = 0.0139 wR2 = 0.0395 0.352 and −0.231

C13H26AgB9N2 415.52 150(2) colorless prism 0.40 × 0.23 × 0.15 orthorhombic Pna21 12.594(3) 13.518(3) 11.130(2) 90 90 90 1894.9(7) 4 1.457 1.061 3.72 − 27.51 −16 ≤ h ≤ 16 −17 ≤ k ≤ 17 −14 ≤ l ≤ 14 25725 4301 (Rint = 0.0736) R1 = 0.0351 wR2 = 0.0846 R1 = 0.0404 wR2 = 0.0876 0.673 and −1.436

C13H25AgB9IN2 541.41 150(2) colorless prism 0.10 × 0.05 × 0.03 orthorhombic Pna21 13.4195(7) 8.8476(5) 17.1015(9) 90 90 90 2030.47(19) 4 1.771 2.512 3.81 − 26.37 −16 ≤ h ≤ 16 −11 ≤ k ≤ 10 −21 ≤ l ≤ 21 13634 4019 (Rint = 0.0361) R1 = 0.0221 wR2 = 0.0523 R1 = 0.0233 wR2 = 0.0532 0.397 and −0.527

C13H22AgB11I6N2 1194.51 150(2) colorless prism 0.12 × 0.06 × 0.06 monoclinic P21/n 12.540(3) 12.090(2) 19.751(4) 90 97.51(3) 90 2968.9(1) 4 2.672 6.927 3.65 − 25.03 −14 ≤ h ≤ 14 −14 ≤ k ≤ 14 −23 ≤ l ≤ 23 39303 5227 (Rint = 0.894) R1 = 0.0293 wR2 = 0.0.691 R1 = 0.0342 wR2 = 0.0708 1.319 and −1.464

B



Article

summarizes details of the data collection and structure refinements details for compounds 1−4.

isolated after 5 days. Yield relative to Ag(PhCB9H9): 6.1 mg, 63%. EA calculated for C13H26AgB9N2: C, 37.57; H, 6.32; N, 6.74. EA found: C, 37.80; H, 6.15; N, 6.55. Selected IR (solid phase, ν/cm−1): 3286w, 3077w, 3047m, 3017m, 2975s, 2948s, 2880s, 2566s, 2509s, 1981w, 1965m, 1889m, 1828w, 1769w, 1683w, 1618w, 1619w, 1594m, 1495m, 1456m, 1366w, 1322m, 1187w, 1080m, 1057m, 1018w, 998m, 952m, 931w, 899w, 856w, 834w, 789m, 768m, 701m, 688w, 674w, 615m, 553w, 518w. [Ag(dabco)(PhCB9H8I)] (3). An identical experimental procedure to that described for compound 1 was performed, using 7.2 mg (16.7 μmol) of Ag(PhCB9H8I) and 4.7 mg (41.9 μmol) of the bridging ligand dabco. After 3 days, colorless single crystals were obtained. Yield relative to Ag(PhCB9H8I): 4.1 mg, 45%. EA calculated for C13H25AgB9IN2: C, 28.84; H, 4.66; N, 5.17. EA found: C, 28.55; H, 4.75; N, 5.10. Selected IR (solid phase, ν/cm−1): 3785w, 3067m, 2950m, 2882m, 2502s, 2288w, 2248w, 1958w, 1944m, 1873m, 1084w, 1748m, 1625w, 1598s, 1538w, 1499s, 1455s, 1368s, 1319s, 1180m, 1158w, 1080m, 1055s, 998m, 910m, 858m, 836m, 789m, 752m, 717m, 695m, 620s, 594s, 555s, 5912s. [Ag(dabco)(PhCB11H5I6)] (4). An identical experimental procedure to those described for compounds 1 and 3 was carried out using 8.8 mg (8.1 μmol) of Ag(PhCB11H5I6) dissolved in a mixture of MeCN/CF3CH2OH (2.0 mL/0.5 mL) and 2.4 mg (21.4 μmol) of dabco dissolved in a mixture of MeCN/CF3CH2OH (1.5 mL/0.5 mL). The formation of colorless crystals was observed after 10 days. Yield relative to Ag(PhCB 11 H 5 I 6 ): 6.5 mg, 67%. EA calculated for C13H22AgB11I6N2: C, 13.07; H, 1.86; N, 2.35. EA found: C, 13.25; H, 1.95; N, 2.50. Selected IR (solid phase, ν/cm−1): 3639w, 3562w, 3070m, 2941s, 2876s, 2599s, 2288w, 2249w, 2058w, 1984w, 1960w, 1886w, 1808w, 1597s, 1581m, 1469s, 1479m, 1456s, 1363m, 1317s, 1251w, 1193w, 1181w, 1160w, 1108w, 1082m, 1054s, 1003s, 935s, 875s, 837s, 785s, 742m, 715s, 692m, 742m, 715s, 632s, 620s, 578m. Single-Crystal X-ray Diffraction. Crystalline samples of [Ag(dabco)][Cobdc] (1), [Ag(dabco)(PhCB9H9)] (2), [Ag(dabco)(PhCB9H8I)] (3), and [Ag(dabco)(PhCB11H5I6)] (4) were manually harvested from their respective crystallization vials, immersed in highly viscous oil, and a suitable single crystal of each complex was mounted on a thin glass fiber or cryo loop.55 Data were collected at 150 K on a Bruker X8 APEX II charge-coupled device (CCD) area-detector diffractometer with an Mo-rotating anode controlled by APEX2.56 Images were processed using the software package SAINT+,57 and data were corrected for absorption by the multiscan semiempirical method implemented in SADABS.58 The structures were solved by direct methods, using SHELXS-97,59,60 permitting the direct location of most of the heaviest atoms, and the remaining non-hydrogen atoms were located from difference Fourier maps calculated from successive full-matrix leastsquares refinement cycles on F2, using SHELXL-97.59,61 The positions of carbon atoms within [Cobdc]− anions were established through evaluation of bond lengths and displacement parameters. All non-hydrogen atoms were successfully refined using anisotropic displacement parameters, and hydrogen atoms attached to carbon and boron were set at idealized positions using appropriate HFIX instruction and included in subsequent refinement cycles in riding-motion approximation with isotropic thermal displacements parameters (Uiso) fixed at 1.2 × Ueq of the atom to which they are connected. Table 1

■

RESULTS AND DISCUSSION Four novel Ag-dabco-based coordination networks incorporating distinct carbaborane anions were isolated as crystalline materials suitable for single-crystal XRD analysis. Their structures were determined and formulated as [Ag(dabco)][Cobdc] (1), [Ag(dabco)(PhCB9H9)] (2), [Ag(dabco)(PhCB9H8I)] (3), and [Ag(dabco)(PhCB11H5I6)] (4). Additionally, all the materials were characterized by FT-IR spectroscopy and CNH elemental analysis. Interestingly, despite the use of carbaborane anions with evident distinct structures and potential coordination groups, all the materials isolated revealed 1D coordination networks (chains). [Ag(dabco)][Cobdc] (1) was crystallized from a solution of MeCN/CF3CH2OH in the monoclinic unit cell with the structure solved and refined in space group Cc (see Experimental Section). The asymmetric unit (asu) of the crystal structure contains only one silver cation, one [Cobdc]− anion, and one dabco ligand (Figure 1). The silver center Ag1

Figure 1. Coordination environment of the Ag1 center found in [Ag(dabco)][Cobdc] (1), with the asu represented as ellipsoids (drawn at the 50% probability level) and the symmetry-generated atoms represented as ball-and-stick models. For clarity reasons only the hydrogen atoms involved in Ag···H−B interactions are drawn. Geometric details about the silver coordination center are listed in Table 2.

coordinates to two nitrogen atoms belonging at two crystallographically equivalent dabco ligands [Ag1−N1 and Ag1−N2i distances of 2.1752(17) and 2.180(17) Å, respectively; Table 2; symmetry transformation: (i) x − 1, y, z] and further interacts with three H−B groups belonging at three equivalent [Cobdc]− anions: Ag1···H1−B1, Ag1···H5i−B5i, and Ag1···H17i−B17i (Ag···H distances of 2.8889(2), 2.4465(2), and 2.8958(1) Å, respectively; Table 2). These Ag···H−B interactions are better envisaged as being more electrostatic than agostic interactions, since they are considerably longer than typical agostic distances, and also the Ag···H−B angles reveal significant linearity. The expression “agostic interaction” was originally used some thirty C



Article

Table 2. Selected Interatomic Distances and Angles of the Main Interactions Involving the Ag1 Centre of [Ag(dabco)][Cobdc] (1).a distance (Å) Ag1−N1 Ag1−N2i Ag1···H1 Ag1···H5i Ag1···H17i

angles (deg) 2.175(2) 2.181(2) 2.889(1) 2.446(1) 2.896(1)

N1−Ag1−N2i N1−Ag1···H1 N1−Ag1··· H5i N1−Ag1··· H17i N2i−Ag1···H1 N2i−Ag1···H5i N2i−Ag1···H17i H1···Ag1···H5i H1···Ag1···H17i H5i···Ag1···H17i

179.09(4) 83.17(4) 94.40(3) 102.86(3) 96.46(3) 84.73(2) 77.88(3) 84.16(1) 150.59(1) 123.35(1)

Symmetry transformation used to generate equivalent atoms: (i) x − 1, y, z. a

years ago to describe an attractive proximity of a metal atom with a CH σ bond.62 At the time, this type of interaction was considered unusual and special; however, it is now well-known that they are rather common and are often important features of transition metal-based complexes.63 Currently, they are classified as covalent intramolecular interactions between an electron deficient metal and a σ-bond in close geometric proximity to the metal atom. With regard to this definition, it should be noted that other types of hydrogen-to-metal interactions are now also often called “agostic” by some authors, which can lead to confusion. While the classic agostic cases involve a CH σ bond close to early transition metal atoms like titanium, many more agostic systems have been proposed, which contain CH, SiH, BH, CC, and SiC bonds coordinated to a wide range of metal atoms.64 To distinguish agostic interactions and other weak electrostatic interactions, distance ranges have been established: the metal−hydrogen distance should range from 1.8 to 2.3 Å, while the metal−hydrogen− carbon angles range between 90 and 140°.65 With consideration of the Ag1−N coordination bonds and all the Ag1···H−B interactions, the Ag1 center reveals a geometry highly distorted, which can be visualized as intermediate between a deformed trigonal bipyramid and a distorted square pyramid [τ = 0.323 ; τ = (β−α)/60, where α and β are the two biggest angles found in the metal coordination center; τ = 0 for the ideal square pyramid, and τ = 1 for ideal trigonal bipyramid]66 (Figure 1 and Table 2). The bridging nature of the dabco ligand between the Ag1 centers lead to the formation of cationic linear 1D coordination networks (i.e., chains), [Ag(dabco)]+, which run along the a axis direction of the unit cell with the Ag···Ag intrachain distance of 6.9544(5) Å (Figure 2a). These cationic coordination chains are intercalated by the [Cobdc]− anions, ultimately generating a zigzag arrangement of both the coordination chains and carborane anions in the [1 0 0] direction of the unit cell (Figure 2b). Although the analogous N-bridging nature of the dabco, pyrazine (pyz), and 4,4′-bipyridine (bpy) ligands in the crystal structures of the [Ag(pyz)(MeCN)][Cobdc] and [Ag(bpy)(MeCN)][Cobdc], reported in our previous work,47 reveal crystalline packing arrangements with distinct features. Nevertheless, these three compounds are based in silver-ligand coordination chains without the incorporation of the bulky [Cobdc]− anions in the framework. In the [Ag(pyz)(MeCN)][Cobdc], the Ag(I) center reveals a distorted tetrahedral geometry, coordinating to two MeCN molecules and two pyz ligands, while in the

Figure 2. Views of the crystal structure of compound 1: (a) Linear 1D coordination network [Ag(dabco)]+ running along the a axis of the unit cell; (b) The extended crystalline packing viewed in the [1 0 0] direction of the unit cell, showing the cationic chains [Ag(dabco)]+ surrounded by the [Cobdc]− anions.

[Ag(bpy)(MeCN)][Cobdc], the Ag(I) center coordinates to an MeCN molecule and two bpy ligands in a T-shape arrangement.47 Compound 2, [Ag(dabco)(PhCB9H9)], was isolated as a crystalline material from a solution in MeCN (see Experimental Section for more details). The crystal structure was solved in the orthorhombic space group Pna21, with the asu consisting of one silver cation, one [PhCB9H9]− anion, and one dabco ligand (Figure 3). The unique silver center Ag1 is coordinated by two nitrogen atoms belonging at two crystallographic equivalent dabco ligands [Ag1−N1 and Ag1−N2i with distances of 2.2750(18) and 2.2713(18) Å, respectively; Table 3; symmetry operation: (i) x + 1/2, −y + 3/2, z]. Furthermore, it interacts with two H−B groups of the phenyl-carbaborane anion, [PhCB9H9]−: Ag1···H12−B1 and Ag1···H13−B4. While the

Figure 3. Coordination environment of the Ag1 center present in compound [Ag(dabco)(PhCB9H9)] (2), with the asu represented as ellipsoids (drawn at the 30% probability level), and the symmetrygenerated atoms represented as ball-and-stick models. For clarity reasons, only the hydrogen atoms involved in Ag···H−B interactions are drawn. For geometric details of the Ag1 center, see Table 3. Symmetry operation: (i) x + 1/2, −y + 3/2, z. D



Article

of the coordination chains is closely related with the incorporation of the phenyl-carbaborane anions, [PhCB9H9]−, in the network through the Ag1···H12−B1 and Ag1···H13−B4 interactions. Actually, at each silver center along the chain, the coordinated [PhCB9H9]− anions point in alternating directions, leading to Ag···Ag intrachain distances of 7.121(1) Å and angles between three consecutive silver centers of 124.328(3)°. These coordination-chain structural features (zigzag chain with the adjacent coordinative anions pointing in opposite directions) are considerably similar to that reported in our previous work for the complexes [Ag(bpy)(PhCB9H4I5)]·(CH3CN) and [Ag(bpy)(PhCB11H5I6)]·(CH3CN).51 The individual coordination chains close pack along the b axis, originating structural layers extended in the [0 0 1] direction of the unit cell (Figure 4). Single crystals of the monoiodo-based compound [Ag(dabco)(PhCB9H8I)] (3) were obtained from the self-assembly of [Ag (PhCB9H8I)] with dabco in a solution of MeCN/ CF3CH2OH (detailed information in Experimental Section), and the crystalline structure was unveiled in the orthorhombic space group Pna21. Similarly to that observed in the previous structures, the asu only revealed one silver cation, one carbaborane anion, viz. [PhCB9H8I]−, and one dabco ligand (Figure 5). The silver center Ag1 establishes coordination

Table 3. Selected Interatomic Distances and Angles of the Ag1 Coordination Centre of the Complex [Ag(dabco)(PhCB9H9)] (2).a distance (Å) Ag1−N1 Ag1−N2i Ag1···H12 Ag1···H13

angles (deg) 2.275(2) 2.271(2) 2.353(1) 1.862(1)

N1−Ag1−N2i N1−Ag1···H12 N1−Ag1····H13 N2i −Ag1···H12 N2i −Ag1···H13 H12···Ag1···H13

123.22(1) 99.25(1) 117.30(1) 109.73(1) 111.63(1) 87.93(1)

a

Symmetry transformation used to generate equivalent atoms: (i) x + 1/2, −y + 3/2, z.

Ag1···H12−B1 link reveals a weaker nature, being in the limit to be considered as an agostic interaction [Ag1···H12 distance of 2.3529(6) Å and Ag1···H12−B1 angle of 112.40(1)°; Table 3], the Ag1···H13−B4 is clearly a stronger interaction and with most of the characteristics of a defined agostic interaction [Ag1···H13 distance of 1.8623(4) Å and Ag1···H13−B4 angle of 112.40(1)°; Table 3]. Despite the considerable differences in the distances, both Ag1···H−B interactions are highly directional, being far from the linearity. With consideration of the Ag1−N coordination bonds and all the Ag1···H−B interactions previously described, the Ag1 center shows a geometry resembling a distorted tetrahedron. The distortion of the silver tetrahedral center is confirmed by their respective N−Ag1−N, N−Ag1···H, and H···Ag1···H internal angles, which range between 87.929(2) and 123.225(6)°. The [Ag(dabco)]+ coordination chains formed by the silver in complex 1 are roughly linear, but in complex 2 the 1D coordination network is puckered to create zigzag chains running along the a axis of the unit cell (Figure 4). This profile

Figure 5. Coordination environment of the Ag1 center present in compound [Ag(dabco)(PhCB9H8I)] (3), with the asu represented as ellipsoids (drawn at the 50% probability level) and the symmetry generated atoms represented as ball-and-stick models. For clarity reasons, only the hydrogen atom involved in the Ag···H−B interaction is shown. For geometric details of the Ag1 center, see Table 4. Symmetry operation: (i) x + 1/2, −y + 1/2, z.

bonds with two nitrogen atoms from two crystallographically equivalent dabco ligands [Ag1−N1 and Ag1−N2i with interatomic distances of 2.263(2) and 2.260(2) Å, respectively; Table 4; symmetry transformation: (i) x + 1/2, −y + 1/2, z] and the iodine atom of the phenyl-carbaborane anion [Ag1−I1 with distance of 2.9155(4) Å]. This distance of the Ag1−I1 coordinative interaction is similar to those found in diverse coordination and organometallic complexes previously reported.51,67−73 Additionally, an Ag···H−B interaction is also found between the Ag1 and one H−B group of the chelating [PhCB9H8I]− anion [Ag1···H7−B7 with Ag1···H7 distance of 2.6097(3) Å and Ag1···H7−B7 angle of 123.0(2)°]. Although there is a considerable directionality of this Ag···H−B interaction, the distance Ag···H is too long to be considered as an agostic interaction, being better visualized as a weak

Figure 4. Zig-zag coordination chains of compound 2, running along the a axis with the coordinated [PhCB9H9]− anions of adjacent silver centers pointing in alternated directions, and close packing in the direction of the b axis of the unit cell. For clarity reasons, only the hydrogen atoms involved in Ag···H−B interactions are shown. E



Article

the phenyl-carbaborane anions point in the same direction, leading to Ag···Ag intrachain distances of 7.0923(4) Å and the angle between three consecutive silver centers of 142.193(3)°. As a consequence of the position of the phenyl-carbaborane anions, the angle of the zigzag chains is considerably larger than that observed in the chain of 2 [124.328(3)°]. The individual coordination chains close pack along the c axis of the unit cell (Figure 6b). An identical experimental procedure to those used for compounds 1 and 3, allowed the preparation of the hexaiodo species [Ag(dabco)(PhCB11H5I6)] (4) as a crystalline material (see Experimental Section for more details). The crystal structure was determined in the monoclinic space group P21/n, with the asu comprising one silver cation, one hexaiodocarbaborane anion, viz. [PhCB11H5I6]−, and one dabco ligand (Figure 7). As observed in all the previous MOF materials (1−

Table 4. Selected Interatomic Distances and Angles of the Ag1 Coordination Centre of the Complex [Ag(dabco)(PhCB9H8I)] (3).a distance (Å) Ag1−N1 Ag1−N2i Ag1−I1 Ag1···H7

angles (deg) 2.263(2) 2.260(2) 2.915(1) 2.610(1)

N1−Ag1−N2i N1−Ag1−I1 N1−Ag1····H7 N2i −Ag1−I1 N2i −Ag1···H7 I1−Ag1···H7

142.57(8) 111.90(5) 98.24(5) 105.45(5) 90.05(6) 80.57(8)

a

Symmetry transformation used to generate equivalent atoms: (i) x + 1/2, −y + 1/2, z.

electrostatic interaction. With consideration of the Ag1−N, Ag1−I coordination bonds, and the Ag1···H7−B7 interaction previously described, the Ag1 center displays a tetrahedral geometry highly distorted. This center is considerably more distorted than that observed in the compound 2, and the elevated distortion is clearly verified by the dispersion in the values of the internal angles (N−Ag1−N, N−Ag1−I, N− Ag1···H, and I−Ag1···H), which ranges between 80.57(8) and 142.57(8)°. The Ag1−N and Ag1−I coordinative interactions originate the formation of 1D coordination networks (chains), with the carbaborane anions [(PhCB9H8I)−] incorporated in the chains. As was observed in compound 2, the coordination chains run along the a axis of the unit cell, with some zigzag arrangement (Figure 6a). However, in contrast with the previous chain, all

Figure 7. Coordination environment of the Ag1 center present in compound [Ag(dabco)(PhCB11H5I6)] (4), with the asu represented as ellipsoids (drawn at 50% probability level) and the symmetry generated atoms represented as a ball-and-stick model. Hydrogen atoms were omitted for clarity reasons. Geometric details of the Ag1 center are listed in Table 5. Symmetry operation: (i) −x + 1/2, y + 1/ 2, −z − 1/2.

3), the silver center Ag1 establishes coordination to two nitrogen atoms from two crystallographically equivalent dabco ligands [Ag1−N1 and Ag1−N2i with interatomic distances of 2.346(4) and 2.321(4) Å, respectively; Table 5; symmetry transformation: (i) −x + 1/2, y + 1/2, −z − 1/2]. Furthermore, the Ag1 coordination center is completed by two iodine atoms of the same phenyl-carbaborane anion [Ag1−I2 and Ag1−I3 with interatomic distances of 2.8276(9) Å and 2.8171(8) Å, respectively]. These distances of the Ag−I coordination bonds are similar to those found in compound 3 and in other reported Table 5. Selected Interatomic Distances and Angles of the Ag1 Coordination Centre of the Complex [Ag(dabco)(PhCB11H5I6)] (4).a distance (Å) Ag1−N1 Ag1−N2i Ag1−I2 Ag1−I3

Figure 6. Crystal structure of compound 3: (a) coordination chain [Ag(dabco)(PhCB9H8I)]1∞ running along the a axis of the unit cell; (b) the extended crystalline packing viewed in perspective in the [0 1 0] direction of the unit cell. Hydrogen atoms were omitted for clarity motives.

angles (deg) 2.346(4) 2.321(4) 2.828(1) 2.817(1)

N1−Ag1−N2i N1−Ag1−I2 N1−Ag1−I3 N2i −Ag1−I2 N2i−Ag1−I3 I2−Ag1−I3

111.40(14) 104.96(10) 115.64(11) 116.78(11) 111.78(10) 95.41(3)

Symmetry transformation used to generate equivalent atoms: (i) −x + 1/2, y + 1/2, −z − 1/2.

a

F



Article

diverse coordination and organometallic complexes.51,67−74 The Ag1 is a four-coordinated center with a slightly distorted tetrahedral geometry: N−Ag1−N, N−Ag1−I, and I−Ag1−I internal angles are found in the range between 95.41(3) and 115.64(11)°. In fact the tetrahedral geometry is the most common in four-coordinated Ag centers; square-planar geometry is rare, with just a handful of examples of this unusual geometry reported. For example, Constable and coworkers described a structure where the silver atoms show a square-planar geometry in a disilver complex with the ligand 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine,75 as well as two other complexes with [Ag(tpy)(MeCN)] + and [Ag(dptpy)(MeCN)]+ species (where tpy is 2,2′:6′,2″-terpyridine and dptpy is 6,6″-diphenyl-2,2′:6′,2″-terpyridine).76 The [Ag(dabco)(PhCB11H5I6)]1∞ coordination chains formed in 4, are comparable to those observed in compound 2 (Figure 8a). The chains have a zigzag profile with the adjacent

individual coordination chains close pack along the c axis of the unit cell, leading to a structural packing of considerably higher density. (Figure 8b).

■

CONCLUDING REMARKS Self-assembly reactions of silver and the N-bridging ligand dabco with diverse bulky carbaborane anions in MeCN or MeCN/CF3CH2OH mixtures, yielded a series of novel coordination networks formulated as [Ag(dabco)][Cobdc] (1), [Ag(dabco)(PhCB9H9)] (2), [Ag(dabco)(PhCB9H8I)] (3), and [Ag(dabco)(PhCB11H5I6)] (4). Their structures were unveiled by single-crystal X-ray diffraction, and all the materials were further characterized by elemental CHN analysis and FT-IR spectroscopy. Remarkably, despite the use of distinct carbaborane anions, all the materials feature 1D coordination networks: [Ag(dabco)]1∞ in 1, [Ag(dabco)(PhCB9H9)]1∞ in 2, [Ag(dabco)(PhCB9H8I)]1∞ in 3, and [Ag(dabco)(PhCB11H5I6)]1∞ in 4. Except the bulky [Cobdc]− anion, all the phenyl-carbaborane anions are incorporated in the coordination chains via Ag···H−B coordinative interactions or Ag···I−B coordination bonds. Furthermore, the influence of the distinct carbaborane anions in the MOF structures is clearly reflected in the coordination features of Ag(I) centers, since all of them are engaged in different combinations of interactions (coordination bonds Ag−N and Ag−I, and both coordinative or electrostatic Ag···H−B interactions) and in the overall structural features of the 1D coordination networks. It can be expected that the exploration of other systems, using distinct Nbridging ligands and including different carbaborane anions, will originate diverse MOF materials with further novel structural features and interesting properties.

■

ASSOCIATED CONTENT

S Supporting Information *

Crystallographic information files (CIF) for compounds 1−4 (CCDC 927871-927874, respectively). This material is available free of charge via the Internet at http://pubs.acs.org.

■

AUTHOR INFORMATION

Corresponding Author

*L.C.-S.: e-mail, [email protected]; tel, +351 220402576; fax, +351 220402659. M.J.H.: e-mail, [email protected]; tel, +44 1133436458; fax, +44 1133436565. Author Contributions

The manuscript was written with contributions of all authors. All authors approved the final version of the manuscript. Notes

The authors declare no competing financial interest.

■

Figure 8. Crystal structure of compound 4. (a) Zig-zag coordination chain [Ag(dabco)(PhCB11H5I6)]1∞, running along the a axis of the unit cell with the coordinated carbaborane anions of adjacent silver centers pointing in alternate directions. (b) The extended crystalline packing viewed in the [1 0 0] direction of the unit cell. Alternate layers are drawn in distinct colors and the H atoms were omitted for clarity purposes.

ACKNOWLEDGMENTS The authors acknowledge the Fundação para a Ciência e a Tecnologia (FCT, MEC, Portugal) for their financial support through the strategic project Pest-C/EQB/LA0006/2011 (to Associated Laboratory REQUIMTE) and the R&D project PTDC/CTM/100357/2008. The University of Leeds is also thanked for additional support.

phenyl-hexaiodocarbaborane anions coordinated to the silver center along the chain pointing in opposite directions [Ag···Ag intrachain distances of 7.243(1) Å and an angle between three consecutive Ag centers of 113.147(7)°]. As a consequence of the size of the carbaborane anions, the angle between the consecutive Ag centers in this chain is significantly smaller than those observed in the coordination chains of 2 and 3. The

■

REFERENCES

(1) Li, H.; Eddaoudi, M.; O’Keeffe, M.; Yaghi, O. M. Nature 1999, 402, 276−279. (2) Seo, J. S.; Whang, D.; Lee, H.; Jun, S. I.; Oh, J.; Jeon, Y. J.; Kim, K. Nature 2000, 404, 982−986.

G



Article

(3) Wang, B.; Cote, A. P.; Furukawa, H.; O’Keeffe, M.; Yaghi, O. M. Nature 2008, 453, 207−U206. (4) Yaghi, O. M.; Li, G. M.; Li, H. L. Nature 1995, 378, 703−706. (5) Yaghi, O. M.; O’Keeffe, M.; Ockwig, N. W.; Chae, H. K.; Eddaoudi, M.; Kim, J. Nature 2003, 423, 705−714. (6) Bloch, E. D.; Queen, W. L.; Krishna, R.; Zadrozny, J. M.; Brown, C. M.; Long, J. R. Science 2012, 335, 1606−1610. (7) Chen, B. L.; Eddaoudi, M.; Hyde, S. T.; O’Keeffe, M.; Yaghi, O. M. Science 2001, 291, 1021−1023. (8) Deng, H. X.; Doonan, C. J.; Furukawa, H.; Ferreira, R. B.; Towne, J.; Knobler, C. B.; Wang, B.; Yaghi, O. M. Science 2010, 327, 846−850. (9) Deng, H. X.; Grunder, S.; Cordova, K. E.; Valente, C.; Furukawa, H.; Hmadeh, M.; Gandara, F.; Whalley, A. C.; Liu, Z.; Asahina, S.; Kazumori, H.; O’Keeffe, M.; Terasaki, O.; Stoddart, J. F.; Yaghi, O. M. Science 2012, 336, 1018−1023. (10) Eddaoudi, M.; Kim, J.; Rosi, N.; Vodak, D.; Wachter, J.; O’Keeffe, M.; Yaghi, O. M. Science 2002, 295, 469−472. (11) Li, J. R.; Ma, Y. G.; McCarthy, M. C.; Sculley, J.; Yu, J. M.; Jeong, H. K.; Balbuena, P. B.; Zhou, H. C. Coord. Chem. Rev. 2011, 255, 1791−1823. (12) Li, J. R.; Sculley, J.; Zhou, H. C. Chem. Rev. 2012, 112, 869−932. (13) Makal, T. A.; Li, J. R.; Lu, W. G.; Zhou, H. C. Chem. Soc. Rev. 2012, 41, 7761−7779. (14) Suh, M. P.; Park, H. J.; Prasad, T. K.; Lim, D. W. Chem. Rev. 2012, 112, 782−835. (15) Sumida, K.; Rogow, D. L.; Mason, J. A.; McDonald, T. M.; Bloch, E. D.; Herm, Z. R.; Bae, T. H.; Long, J. R. Chem. Rev. 2012, 112, 724−781. (16) Lee, J.; Farha, O. K.; Roberts, J.; Scheidt, K. A.; Nguyen, S. T.; Hupp, J. T. Chem. Soc. Rev. 2009, 38, 1450−1459. (17) Farrusseng, D.; Aguado, S.; Pinel, C. Angew. Chem., Int. Ed. 2009, 48, 7502−7513. (18) Corma, A.; Garcia, H.; Xamena, F. X. L. Chem. Rev. 2010, 110, 4606−4655. (19) Granadeiro, C. M.; Barbosa, A. D. S.; Silva, P.; Paz, F. A. A.; Saini, V. K.; Pires, J.; de Castro, B.; Balula, S. S.; Cunha-Silva, L. Appl. Catal., A 2013, 453, 316−326. (20) Balula, S. S.; Granadeiro, C. M.; Barbosa, A. D. S.; Santos, I. C. M. S.; Cunha-Silva, L. Catal. Today 2013, (in press) 10.1016/ j.cattod.2012.003. (21) McKinlay, A. C.; Morris, R. E.; Horcajada, P.; Ferey, G.; Gref, R.; Couvreur, P.; Serre, C. Angew. Chem., Int. Ed. 2010, 49, 6260− 6266. (22) Huxford, R. C.; Della Rocca, J.; Lin, W. B. Curr. Opin. Chem. Biol. 2010, 14, 262−268. (23) Della Rocca, J.; Liu, D. M.; Lin, W. B. Acc. Chem. Res. 2011, 44, 957−968. (24) Carne, A.; Carbonell, C.; Imaz, I.; Maspoch, D. Chem. Soc. Rev. 2011, 40, 291−305. (25) Furukawa, Y.; Ishiwata, T.; Sugikawa, K.; Kokado, K.; Sada, K. Angew. Chem., Int. Ed. 2012, 51, 10566−10569. (26) Masoomi, M. Y.; Morsali, A. Coord. Chem. Rev. 2012, 256, 2921−2943. (27) Stavila, V.; Bhakta, R. K.; Alam, T. M.; Majzoub, E. H.; Allendorf, M. D. ACS Nano 2012, 6, 9807−9817. (28) Li, Y.; Zhang, S. S.; Song, D. T. Angew. Chem., Int. Ed. 2013, 52, 710−713. (29) Meilikhov, M.; Furukawa, S.; Hirai, K.; Fischer, R. A.; Kitagawa, S. Angew. Chem., Int. Ed. 2013, 52, 341−345. (30) Tan, H. L.; Liu, B. X.; Chen, Y. ACS Nano 2012, 6, 10505− 10511. (31) Ng, L. L.; Ng, B. K.; Shelly, K.; Knobler, C. B.; Hawthorne, M. F. Inorg. Chem. 1991, 30, 4278−4280. (32) Vinas, C.; Nunez, R.; Flores, M. A.; Teixidor, F.; Kivekas, R.; Sillanpaa, R. Organometallics 1995, 14, 3952−3957. (33) Xie, Z. W.; Liu, Z. X.; Chin, K. Y.; Xue, F.; Mak, T. C. W. Organometallics 1997, 16, 2460−2464. (34) Xie, Z. W.; Liu, Z. X.; Yang, Q. C.; Mak, T. C. W. Organometallics 1999, 18, 3603−3609.

(35) Chui, K. L.; Yang, Q. C.; Mak, T. C. W.; Xie, Z. W. Organometallics 2000, 19, 1391−1401. (36) Wang, S. W.; Li, H. W.; Xie, Z. W. Organometallics 2001, 20, 3842−3844. (37) Westerhausen, M.; Guckel, C.; Schneiderbauer, S.; Noth, H.; Hosmane, N. S. Angew. Chem., Int. Ed. 2001, 40, 1902−1904. (38) Fox, M. A.; Mahon, M. F.; Patmore, N. J.; Weller, A. S. Inorg. Chem. 2002, 41, 4567−4573. (39) Cheung, M. S.; Chan, H. S.; Bi, S. W.; Lin, Z. Y.; Xie, Z. W. Organometallics 2005, 24, 4333−4336. (40) Kasna, B.; Jambor, R.; Dostal, L.; Cisarova, I.; Holecek, J.; Stibr, B. Organometallics 2006, 25, 5139−5144. (41) Drozdova, V. V.; Malinina, E. A.; Belousova, O. N.; Polyakova, I. N.; Kuznetsov, N. T. Russ. J. Inorg. Chem. 2008, 53, 1024−1033. (42) Hardie, M. J.; Raston, C. L. CrystEngComm. 2001, 39. (43) Ahmad, R.; Hardie, M. J. Cryst. Growth Des. 2003, 3, 493−499. (44) Hardie, M. J.; Sumby, C. J. Inorg. Chem. 2004, 43, 6872−6874. (45) Ahmad, R.; Hardie, M. J. New J. Chem. 2004, 28, 1315−1319. (46) Westcott, A.; Whitford, N.; Hardie, M. J. Inorg. Chem. 2004, 43, 3663−3672. (47) Cunha-Silva, L.; Ahmad, R.; Hardie, M. J. Aust. J. Chem. 2006, 59, 40−48. (48) Cunha-Silva, L.; Westcott, A.; Whitford, N.; Hardie, M. J. Cryst. Growth Des. 2006, 6, 726−735. (49) Sumby, C. J.; Carr, M. J.; Franken, A.; Kennedy, J. D.; Kilner, C. A.; Hardie, M. J. New J. Chem. 2006, 30, 1390−1396. (50) Hardie, M. J. J. Chem. Crystallogr. 2007, 37, 69−80. (51) Cunha-Silva, L.; Ahmad, R.; Carr, M. J.; Franken, A.; Kennedy, J. D.; Hardie, M. J. Cryst. Growth Des. 2007, 7, 658−667. (52) Cunha-Silva, L.; Hardie, M. J. CrystEngComm. 2012, 14, 3367− 3372. (53) Franken, A.; Kilner, C. A.; Thornton-Pett, M.; Kennedy, J. D. Collect. Czech. Chem. Commun. 2002, 67, 869. (54) Xie, Z. W.; Jelinek, T.; Bau, R.; Reed, C. A. J. Am. Chem. Soc. 1994, 116, 1907−1913. (55) Kottke, T.; Stalke, D. J. App. Cryst. 1993, 26, 615−619. (56) APEX2, Data Collection, version 2.1-RC13, Bruker AXS: Delft, The Netherlands, 2006. (57) SAINT+, Data Integration Engine version 7.23a, Bruker AXS: Madison, Wisconsin, USA, 1997−2005. (58) Sheldrick, G. M. SADABS version 2.01, Bruker/Siemens Area Detector Absorption Correction Program, Bruker AXS: Madison, Wisconsin, 1998. (59) Sheldrick, G. M. Acta Cryst. A 2008, 64, 112−122. (60) Sheldrick, G. M., SHELXS-97, Program for Crystal Structure Solution, University of Göttingen: Göttingen, Germany, 1997. (61) Sheldrick, G. M., SHELXL-97, Program for Crystal Structure Refinement, University of Göttingen: Göttingen, Germany, 1997. (62) Brookhart, M.; Green, M. L. H. J. Organomet. Chem. 1983, 250, 395−408. (63) Perutz, R. N.; Sabo-Etienne, S. Angew. Chem., Int. Ed. 2007, 46, 2578−2592. (64) Lein, M. Coord. Chem. Rev. 2009, 253, 625−634. (65) Brookhart, M.; Green, M. L. H.; Parkin, G. Proc. Natl. Acad. Sci. U.S.A. 2007, 104, 6908−6914. (66) Addison, A. W.; Rao, T. N.; Reedijk, J.; Vanrijn, J.; Verschoor, G. C. J. Chem. Soc., Dalton Trans. 1984, 1349−1356. (67) Eisler, D. J.; Puddephatt, R. J. Inorg. Chem. 2003, 42, 8192− 8202. (68) Li, N.-Y.; Ren, Z.-G.; Liu, D.; Yuan, R.-X.; Wei, L.-P.; Zhang, L.; Li, H.-X.; Lang, J.-P. Dalton Trans. 2010, 39, 4213−4222. (69) Patmore, N. J.; Ingleson, M. J.; Mahon, M. F.; Weller, A. S. Dalton Trans. 2003, 0, 2894−2904. (70) Wang, X.; Liu, S.; Weng, L.-H.; Jin, G.-X. Organometallics 2006, 25, 3565−3569. (71) Ruiz, J.; Gonzalo, M. P.; Vivanco, M.; Quesada, R.; Mosquera, M. E. G. Dalton Trans. 2009, 0, 9280−9290. (72) Xie, Z.; Wu, B.-M.; Mak, T. C. W.; Manning, J.; Reed, C. A. J. Chem. Soc., Dalton Trans. 1997, 0, 1213−1218. H



Article

(73) Chandran, S. K.; Thakuria, R.; Nangia, A. CrystEngComm 2008, 10, 1891−1898. (74) Young, A. G.; Hanton, L. R. Coord. Chem. Rev. 2008, 252, 1346−1386. (75) Constable, E. C.; Housecroft, C. E.; Kariuki, B. M.; Kelly, N.; Smith, C. B. Inorg. Chem. Commun. 2002, 5, 199−202. (76) Constable, E. C.; Edwards, A. J.; Haire, G. R.; Hannon, M. J.; Raithby, P. R. Polyhedron 1998, 17, 243−253.

I


Silver-Dabco Coordination Networks with Distinct Carbaborane

Recommend Documents