One-Dimensional Coordination Polymers with Phenyl-carbaborane

One-Dimensional Coordination Polymers with Phenyl-carbaborane Anions: Ag(I)/4,4′-Bipyridine and 2,3-Bis-(2-pyridyl)pyrazine Complexes Luı´s Cunha-Silva, Ruksanna Ahmad, Michael J. Carr, Andreas Franken, John D. Kennedy, and Michaele J. Hardie*

CRYSTAL GROWTH & DESIGN 2007 VOL. 7, NO. 4 658-667

School of Chemistry, UniVersity of Leeds, Leeds LS2 9JT, U.K. ReceiVed January 16, 2007

ABSTRACT: A series of new silver/4,4′-bipyridine [Ag(I)/bpy] and silver/2,3-bis-(2-pyridyl)pyrazine [Ag(I)/bppz] crystalline complexes with the C-phenyl-carbaborane anion [PhCB9H9]- and the halogenated C-phenyl-carbaborane (HPC) anions [PhCB9H8Br]-, [BrC6H4CB11H11]-, [PhCB9H4I5]-, and [PhCB11H5I6]- has been prepared and characterized by elemental analysis, infrared spectroscopy, and single-crystal X-ray diffraction analysis. While {Ag(bppz)[PhCB9H8Br]} (6) has been isolated as a discrete dimeric complex, all the remaining complexes feature 1D polymeric coordination chains. Among these 1D coordination chains, only [Ag(bpy)][PhCB9H9](CH3CN) (1) and [Ag2(bppz)3][BrC6H4CB11H11]2(CH3CN) (5) exhibit structures where the carbaborane anions act as simple counteranions and thus are not involved directly in the coordination network. In all the other species, significant frameworkconstruction interaction of the silver center with the {BH} or {BI} units of the carbaborane anions is observed. Interestingly, in complex {Ag(bppz)[PhCB9H9]} (CH3CN)0.5 (4) the Ag(I) center has an octahedral geometry with two Ag‚‚‚H-B interactions between the silver atom and phenyl-carbaborane anion. The influence of the carbaborane anions on the structural features of coordination chains is analyzed and discussed, and the preparation of the [NEt4]+ salts of the [PhCB9H8Br]-, [BrC6H4CB11H11]-, and [PhCB9H4I5]anions is also presented. Introduction Coordination polymers, viz., coordination frameworks or metal-organic frameworks, are infinite one-, two-, or threedimensional (1D, 2D, or 3D) coordination complexes with highly ordered structures that have been subjected to remarkable development in the last years.1 This recent progress comes from both their fascinating structural chemistry2 and high potential in a large range of applications, such as gas storage, catalysis, ion-exchange, molecular sieving, magnetism, and switches.3 The applicability of coordination polymer materials is directly associated with their structural features. It is well-known that the nature of multifunctional ligands, the coordination requirements of the metal ion, the metal-ligand ratio, and the counterion are all highly influential on the resulting coordination mode of the metal. Therefore, it is generally likely that subtle changes in any of these factors can lead to new extended network structures affording a large range of new materials.4 As part of our investigations in crystalline supramolecular chemistry, we are studying the influence of carbaborane anions on the structure of coordination polymers, especially systems that have been previously characterized with more traditional weakly coordinating anions. One of these systems is that of Ag(I) and the nitrogen-donor rigid ligands 4,4′-bipyridine (bpy) and 2,3-bis(2-pyridyl)pyrazine (bppz). Of these there is a significant number

of 1D, 2D, and 3D coordination networks incorporating Ag(I) and the rigid bpy ligand.5-8 On the other hand, coordination * Corresponding author. Fax: +44 113 343 6565. Phone: +44 113 343 6458. E-mail: [email protected].

networks involving bppz and Ag(I) are very rare. There are few cases of coordination networks involving Ag(I) and bppz, with only a few 1D chain structures known, as recently reported by us,5 together with a few 2D networks.9 Carbaboranes, often named carboranes, are polyhedral cluster compounds containing both carbon and boron as cluster constituents, derived from boranes and borane anions by the introduction of C-H or C-R groups as cluster vertices.10 Monocarbaboranes s carbaboranes that have only one carbon atom in the cluster s tend to be monoanionic species and may be arylated at carbon vertices to form C-phenyl monocarbaboranes and halogenated at boron vertices to form halogenated C-phenyl-carbaboranes (abbreviated here as “HPC”), Scheme 1.11,12 Monocarbaborane anions are generally weakly coordinating, although halogenated monocarbaboranes may bind to metal centers through their halogen sites13-15 and B-H‚‚‚Ag interactions have also been reported.15-17 Hence, in coordination polymers, carbaborane anions may act as bulky, templating anions or as ligands themselves. Despite these interesting properties, the preparation of new coordination polymers with halogenated carbaborane anions is limited to (a) simple Ag(I) chain structures with bridging halogenated carbaboranes,13 (b) a series of group 1 coordination networks with cyclotriveratrylene as the bridging ligand,18 and (c) a 2D organometallic hexagonal network.19 Most investigations of coordination networks with carbaborane anions have instead focused on the nonhalogenated and commercially available icosahedral [CB11H12]- anion or the sandwich complex [Co(C2B9H11)2]-, the so-called “COSAN” anion. These works have demonstrated a high influence of these carbaborane anions upon the overall structural features of the resultant coordination polymers, with the anions acting as simple counterions17,20 or as part of the coordination sphere.17 In this context, in a recent study we reported the crystalline structures of complexes of Ag(I) and the N-bridging rigid ligands pyrazine, bpy, and bppz with the anions [CB11H12]- and [Co(C2B9H11)2]-.5 In these cases, 1D coordination chains were

10.1021/cg070048p CCC: $37.00 © 2007 American Chemical Society Published on Web 03/21/2007

Ag Complex One-Dimensional Coordination Polymers Scheme 1.

Crystal Growth & Design, Vol. 7, No. 4, 2007 659

Monoanionic Monocarbaboranes Used in This Study

obtained with the bpy or bppz ligands, and the carbaborane anions did not coordinate to the Ag(I) centers. Herein we now report a set of new coordination complexes of Ag(I) and bpy or bppz that incorporate C-phenyl-monocarbaboranes as counteranions, of which some are halogenated at a B-vertex (halogenophenylcarbaboranes, HPC). Specifically, the new complexes are [Ag(bpy)][PhCB9H9](CH3CN) (1), {Ag(bpy)[PhCB9H4I5]}(CH3CN) (2), {Ag(bpy)[PhCB11H5I6]}(CH3CN) (3), [Ag(bppz)[PhCB9H9]}(CH3CN)0.5 (4), [Ag2(bppz)3][BrC6H4CB11H11]2(CH3CN) (5), and {Ag(bppz)[PhCB9H8Br]} (6). Their structures were determined by single-crystal X-ray diffraction analysis, and they are also characterized by elemental analysis and infrared spectroscopy. Among the crystalline compounds isolated, complex {Ag(bppz)[PhCB9H8Br]} (6) uniquely forms a discrete dimeric complex, whereas all the other complexes show 1D coordination network structures. In the Ag(I)/bpy system, while the simple phenyl-carbaborane [PhCB9H9]- acts only as a counteranion in complex 1, the HPC anions [PhCB9H4I5]- and [PhCB11H5I6]-, in 2 and 3, respectively, are coordinated through two iodine atoms to novel zigzag chains. Among the complexes belonging to the system Ag(I)/bppz, both the complexes {Ag(bppz)[PhCB9H9]}(CH3CN)0.5 (4) and [Ag2(bppz)3][BrC6H4CB11H11]2(CH3CN) (5) are 1D coordination polymers. However, they are structurally different: in complex 4, the phenyl-carbaborane [PhCB9H9]- anion is coordinated to the chain through Ag‚‚‚H-B interactions, whereas in 5 the HPC anion [BrC6H4CB11H11]- is not part of the chain and acts only as a simple counteranion. In addition, the modes of coordination between the bppz and Ag(I) are different in the two complexes. Experimental Section General. Bridging N-ligands 4,4′-bipyridine (bpy; Aldrich, 98%) and 2,3-bis-(2-pyridyl)pyrazine (bppz; Aldrich, 98%), nido-B10H14 (Katchem, Prague) as well AR grade solvents were used as received from the commercial suppliers without further purification. Synthesis of the [NEt4]+ salts of [PhCB9H9]-,12c [PhCB11H11]-,12d and [PhCB9H4I5]- 12e have been previously reported. The halogenated anions [PhCB9H8Br]-, [BrC6H4CB11H11]-, and [PhCB11H5I6]- have been mentioned in an overview article,11 but preparative and characterization details were not given. It is convenient here to present their preparation and characterization as their [NEt4]+ salts. The [NEt4]+ salts of all the anions were converted to their Ag(I) salts by metathesis with AgNO3 via their corresponding monoacids, according to the procedure that we have recently reported for the synthesis of Ag[PhCB9H8I].21 The elemental analyses were performed in the University of Leeds microanalytical laboratory, and the infrared (IR) spectra were recorded on the solid-phase Perkin-Elmer Spectrum One spectrometer. NMR spectroscopy was carried out on commercially available instrumentation,

cluster 11B and 1H assignments being made by homonuclear and heteronuclear correlation experiments using general procedures as adequately described elsewhere.12 Chemical shifts δ(11B) are quoted relative to Ξ(11B) ) 32.083972 MHz (nominally [11BF3(OEt2)] in CDCl3). Preparation of Carbaboranes. (a) [NEt4][1-Ph-closo-1-CB9H8-6Br]. [Cs]+[1-Ph-closo-1-CB9H9]- 12c,d (330 mg, 1.0 mmol) was dissolved in CH3CN (10 mL), and N-bromosuccinimide (190 mg, 1.1 mmol) was added. The reaction mixture was stirred for 18 h at ambient temperature, and H2O (30 mL) was added. Following removal of the CH3CN in vacuo, the resulting pale yellow aqueous solution was extracted with Et2O (3 × 30 mL), and the combined ether layers were evaporated in vacuo to yield a colorless oil. This oily residue was dissolved in H2O (30 mL), and, after addition of [NEt4]Cl (500 mg, 3 mmol), a colorless precipitate developed. This precipitate was filtered off and dried in vacuo to yield the colorless [NEt4]+ salt of the [1-Ph-closo-1-CB9H86-Br]- anion as a white solid (375 mg, 920 µmol, 92%). Crystals suitable for a single-crystal X-ray diffraction analysis were obtained from a concentrated solution in (CH3)2CO that was overlayered with a ca. 5-fold excess of Et2O. NMR data for [NEt4][1-Ph-closo-1-CB9H86-Br], in (CD3)2CO at 294-299 K, ordered as assignment δ(11B)/ppm [δ(1H)/ppm] are as follows: BH(10) +26.9 [+5.30], BBr(6) -12.4, BH(4,5) -12.4 [+1.84], BH(2,3) -14.9 [+2.04], BH(7,9) -20.3 [+1.55], and BH(8) -26.1 [+0.70]; additionally, δ(1H)(Ph) at +7.90 (2 H, apparent doublet) and +7.32 (3H, multiplet), with δ(1H)(Et) at +3.48 (8H, quartet) and +1.39 (12H, triplet); also, δ(13C)(Ph) +143.1 (1C), +130.6 (2C), +127.9 (2C), and +126.1 (1C), with δ(13C)(cluster) +67.3 and with δ(13C)(Et) +52.4 and +7.1 ppm. (b) [NEt4][1-{4-Br-C6H4}-closo-1-CB11H11] Part 1: [NEt4][6-{4Br-C6H4}-nido-6-CB9H11]. A cold (ca. 0 °C) solution of KOH (15 g, 250 mmol) in H2O (150 mL) and EtOH (70 mL) was added to B10H14 (6 g, 49 mmol) held at 0 °C. Over a period of 6 h, 4-Br-C6H4-CHO (74 g, 400 mmol) was then added. The EtOH was removed in vacuo, and H2O (200 mL) was added. The alkaline solution was extracted three times with Et2O (3 × 75 mL), and H2O (200 mL) was added to the combined ether extracts. The Et2O was removed under reduced pressure, and [NEt4]Cl (10 g, 60 mmol) was added to the resulting aqueous solution, resulting in a yellowish coloration. After addition of EtOH (100 mL) to the stirred solution, and after further stirring, the resulting colorless precipitate was filtered off, washed with H2O (3 × 40 mL), and dried in vacuo to yield the [NEt4]+ salt of the [6-{4-BrC6H4}-nido-6-CB9H11]- anion as a while crystalline solid (7.06 g, 25.5 mmol, 52%). NMR data for [NEt4] [6-{4-Br-C6H4}-nido-6-CB9H11], in (CD3)2CO at 294-299 K, ordered as assignment δ(11B)/ppm [δ(1H)/ppm], are as follows: BH(5,7) +1.8 [+3.38], BH(9) -1.9 [+2.94], BH(1,3) -4.4 [+2.50], BH(8,10) -12.2 [+2.00], BH(2) -26.0 [+0.61], and BH(4) -37.7 [+0.42], with δ(1H) for µH(8,9;9,10) at -3.32 ppm; additionally, δ(1H)(C6H4) at +7.24 (2H, apparent doublet) and +7.02 (2H, apparent doublet), with δ(1H)(Et) at +3.49 (8H, quartet) and +1.33 (12H, triplet); also, δ(13C)(Ph) +124.1 (1C), +127.3 (2C), +127.6 (2C), and +141.5 (1C), with δ(13C)(cluster) +63.2 and with δ(13C)(Et) +7.1 and +52.5 ppm. Part 2: [NEt4][1-{4-Br-C6H4}-closo-1-CB11H11]. A sample of the [NEt4]+ salt (Ca) of the [6-{4-Br-C6H4}-nido-6-CB9H11]- anion (C)

660 Crystal Growth & Design, Vol. 7, No. 4, 2007

Cunha-Silva et al.

Table 1. Details of Data Collections and Structure Refinements for Complexes 1-6

formula Mr cryst color and shape cryst size/mm cryst syst space group a/Å b/Å c/Å R/° β/° γ/° V/Å3 Z Fc/g cm-3 F(000) µ/cm-1 θ range/deg no. data collected no. unique data Rint no. obs data [I > 2σ(I)] no. params no. restraints R1 (obs data) wR2 (all data) S min and max residual electron density/e Å3

1

2

3

4

5

6

C19H25AgB9N3 500.58 colorless and needles 0.25 × 0.12 × 0.08 monoclinic P21/n 10.1666(2) 11.3757(2) 20.3238(6) 90 91.6694(9) 90 2349.67(9) 4 1.415 1008 0.870 3.32-28.28 17137 5607 0.0420 4069

C19H20B9N3AgI5 1130.07 colorless and prismatic 0.30 × 0.20 × 0.10 monoclinic P21/c 12.1354(9) 20.8408(15) 14.1118(11) 90 112.174(4) 90 3305.1(4) 4 2.271 2048 5.296 2.50-36.86 105872 14569 0.0448 11779

C19H21AgB11I6N3 1279.57 colorless and prismatic 0.18 × 0.09 × 0.04 triclinic P1h 9.5560(2) 11.7740(2) 16.6977(3) 97.0146(7) 96.2209(9) 109.3930(9) 1736.37(6) 2 2.447 1152 5.932 2.67-28.27 35996 8521 0.1560 6407

C22H28.5AgB9N4.5 558.13 pale yellow and prismatic 0.50 × 0.20 × 0.08 monoclinic P21/c 11.8844(2) 14.1195(2) 15.1552(2) 90 95.362(1) 90 2531.94(6) 4 1.464 1124 0.818 1.98-27.51 19402 5765 0.0452 5236

C58H63Ag2B22Br2N13 1555.59 pale yellow and prismatic 0.33 × 0.14 × 0.02 triclinic P1h 12.2071(1) 12.8065(1) 23.8761(3) 98.978(1) 92.003(1) 106.649(1) 3519.73(6) 2 1.468 1552 1.740 2.60-28.35 62897 17162 0.0973 11439

C21H23AgB9BrN4 616.50 pale yellow and prismatic 0.20 × 0.13 × 0.07 monoclinic C2/c 24.6696(6) 12.1740(4) 21.0898(5) 90 124.454(2) 90 5222.9(2) 8 1.568 2432 2.321 2.34-28.34 23246 6156 0.119 4629

293 0 0.0939 0.2402 1.042 -2.900 and 1.924

366 0 0.0386 0.0962 1.135 -2.393 and 2.346

365 0 0.0543 0.1658 1.007 -1.923 and 2.001

420 0 0.0365 0.1000 1.032 -1.121 and 1.033

878 0 0.0535 0.1441 1.020 -1.155 and 1.600

327 0 0.1254 0.4117 1.667 -1.700 and 3.502

(5.1 g, 18 mmol) was dissolved in 1,2-Cl2C2H4 (60 mL), a large excess of [BH3(SMe2)] (30 mL, 316 mmol) was added, and the mixture was heated under reflux for 48 h. After cooling to 0 °C, H2O (50 mL) was added slowly, and then aqueous HCl (10%, 150 mL). Following removal of the 1,2-Cl2C2H4 under reduced pressure, the remaining aqueous layer was extracted with Et2O (3 × 75 mL), and the combined ethereal extracts were evaporated in vacuo to yield a colorless oil. This oily residue was dissolved in H2O (100 mL), and after addition of [NEt4]Cl (4.0 g, 24 mmol) to the stirred solution, a colorless precipitate developed. After further stirring, this precipitate was filtered off and then dried in vacuo, to yield the [NEt4]+ salt of the [1-{4-Br-C6H4}closo-1-CB11H11]- anion as a white crystalline solid (5.5 g, 15.5 mmol, 84%; overall 43% from B10H14). Crystals suitable for a single-crystal X-ray diffraction analysis were obtained from a concentrated solution in (CH3)2CO that was overlayered with a ca. 5-fold excess of Et2O. NMR data for [NEt4][1-{4-Br-C6H4}-closo-1-CB11H11], in CD3CN at 294-299 K, ordered as assignment δ(11B)/ppm [δ(1H)/ppm], are as follows: BH(12) -8.0 [+2.13], BH(2,3,4,5,6) and BH(7,8,9,10,11) accidentally coincident at ca. -12.9 [ca. +1.75]; additionally, δ(1H)(C6H4) at +7.22 (2H, apparent doublet) and +7.03 (2 H, apparent doublet), with δ(1H)(Et) at +3.49 (8H, quartet) and +1.33 (12H, triplet); also, δ(13C)(Ph) +124.3 (1C), +127.2 (2C), +127.6 (2C), and +141.4 (1C), with δ(13C)(Et) +7.1 and +52.5 ppm. (c) [NEt4][1-Ph-closo-1-CB11H5-7,8,9,10,11,12-I6]. [Cs][1-Ph-closo1-CB11H11]- (prepared as in ref 12d; 330 mg, 1 mmol) was dissolved in glacial CH3COOH (10 mL). ICl (3.0 g, 18 mmol) was then added, and the mixture was stirred and heated for 72 h at 110 °C. The reaction mixture was cooled to 0 °C, H2O (50 mL) and Na2SO3 (3.8 g, 30 mmol) were added with stirring, and the solvents were removed under reduced pressure. The residual oil was dissolved in H2O (50 mL), and the solution was filtered. [NEt4]Cl (500 mg, 3 mmol) was added to the filtrate, and a colorless precipitate developed. The white precipitate was filtered off and dried in vacuo to yield the colorless [NEt4]+ salt of the [1-Ph-closo-1-CB11H5-7,8,9,10,11,12-I6]- anion as a white solid (860 mg, 780 µmol, 78%). Crystals suitable for a single-crystal X-ray diffraction analysis were obtained from a concentrated solution in (CH3)2CO that was overlayered with a ca. 5-fold excess of Et2O. NMR data for [NEt4][1-Ph-closo-1-CB11H5-7,8,9,10,11,12-I6], in (CD3)2CO at 294-299 K, ordered as assignment δ(11B)/ppm [δ(1H)ppm] are as follows: BI(12) -7.1, BH(2,3,4,5,6) -11.9 [+3.35], BI(7,8,9,10,11) -18.8; additionally, δ(1H)(Ph) +7.82 (2H, apparent doublet) and +7.47

(3H, multiplet), with δ(1H)(Et) at +3.49 (8H, quartet) and +1.40 (12H, triplet); also, δ(13C)(Ph) +132.6 (1C), +129.9 (2C), +128.7 (2C), and +127.9 (1C), with δ(13C)(cluster) +42.5 and with δ(13C)(Et) +52.4 and +7.1 ppm. Preparation of Complexes. (a) [Ag(bpy)][PhCB9H9](CH3CN), 1. Ag[PhCB9H9] (7.2 mg, 23.7 µmol) was dissolved in acetonitrile (2.0 cm3) and added to a solution of bpy (3.9 mg, 24.9 µmol) dissolved separately in acetonitrile (2.0 cm3). The solution was left to stand uncovered, and after several days colorless crystals of 1 formed. Yield: 5.2 mg, 44%. Anal. Calcd for C19H25N3B9Ag: C, 45.58; H, 5.04; N, 8.40. Found: C, 45.35; H, 4.95; N, 8.10. IR (solid phase, ν cm-1): 3058 w, 2992 s, 2930 s, 2532 s, 2426 s, 2252 s, 1948 s, 1608 s, 1537 s, 1491 s, 1418 s, 1327 s, 1223 s, 1153 s, 1098 s, 1073 s, 1016 s. (b) {Ag(bpy)[PhCB9H4I5]}(CH3CN), 2. Ag[PhCB9H4I5] (5.9 mg, 7.2 µmol) and bpy (1.4 mg, 8.9 µmol) were treated as described for the complex 1. After 7 days of slow evaporation the formation of colorless crystals of 2 was observed. Yield: 5.4 mg, 66%. Anal. Calcd for C19H20N3B9I5Ag: C, 20.19; H, 1.78; N, 3.72. Found: C, 20.55; H, 1.95; N, 3.60. Selected IR (solid phase, ν cm-1): 3055 w, 2571 s, 2439 s, 2159 vs, 2022 vs, 1977 vs, 1606 m, 1532 m, 1494 m, 1487 m, 1412 m, 1369 m, 1219 m, 1154 w, 1109 m, 1065 m, 1004 m, 954 m, 914 m, 804 m, 698 m, 627 m. (c) {Ag(bpy)[PhCB11H5I6]}(CH3CN), 3. Ag[PhCB11H5I6] (6.2 mg, 6.4 µmol) and bpy (1.1 mg, 7.0 µmol) were each dissolved in acetonitrile (2.0 cm3) and then mixed together. The solution was left to stand uncovered, and after several days colorless crystals of 3 formed. Yield: 4.2 mg, 51%. Anal. Calcd for C19H21N3B11I6Ag: C, 17.83; H, 1.66; N, 3.28. Found: C, 18.10; H, 1.85; N, 3.60. Selected IR (solid phase, ν cm-1): 3309 br, 3061 s, 2206 s, 1958 s, 1496 s, 1450 s, 1416 s, 1344 s, 1394 s, 1349 s, 1152 s, 1133 s, 1099 s, 1062 s, 1039 s. (d) {Ag(bppz)[PhCB9H9]}(CH3CN)0.5, 4. Ag(PhCB9H9) (7.9 mg, 26.0 µmol) and bppz (6.1 mg, 26.0 µmol) were treated in the same way as for 1. The solution was left to stand uncovered, and after several days pale yellow crystals of 4 were formed. Yield: 9.3 mg, 46%. Anal. Calcd for C30H41N5B18Ag: C, 47.21; H, 4.87; N, 11.26. Found: C, 47.55; H, 4.65; N, 10.95. Selected IR (solid phase, cm-1): 3071 s, 3060 s, 2507 s, 2210 m, 2133 m, 2089 m, 1589 s, 1494 s, 1400 s, 1297 s, 1243 s, 1158 s, 1125 s, 1102 s, 1058 s, 1038 s, 1002 s. (e) [Ag2(bppz)3][BrC6H4CB11H11]2(CH3CN), 5. Ag(BrC6H4CB11H11) (6.6 mg, 16.3 µmol) and bppz (3.9 mg, 16.6 µmol) were treated in the

Ag Complex One-Dimensional Coordination Polymers


Figure 1. Crystallographically determined molecular structures of the [NEt4]+ salts of newly synthesized carbaborane anions: (a) [1-Ph-closo-1CB9H8-6-Br]- anion (CCDC 184224) monoclinic, Cc, a ) 32.7954(5), b ) 14.2646(2), c ) 14.0084(2) Å, β ) 91.053(1)°; (b) [1-(p-Br-C6H4)closo-1-CB11H11]- anion (CCDC 184223) monoclinic, P21/c, a ) 8.6027(2), b ) 18.1219(4), c ) 16.3411(5) Å, β ) 90.873(1)°; (c) [1-Ph-closo1-CB11H5-7,8,9,10,11,12-I6]- anion (CCDC 184232) monoclinic, C2/c, a ) 34.4096(3), b ) 9.9689(1), c ) 23.2297(3) Å, β ) 127.021(1)° (ref 11).

same way as for 1. The solution was left to stand uncovered, and after several days pale yellow crystals of 5 were formed. Yield: 10.3 mg, 40%. Anal. Calcd for C58H63N13B22Br2Ag2: C, 44.78; H, 4.09; N, 11.71. Found: C, 42.90; H, 4.05; N, 10.50. Selected IR (solid phase, cm-1): 3651 s, 3069 s, 2505 s, 1934 s, 1791 s, 1721 s, 1593 s, 1569 s, 1556 s, 1532 s, 1489 s, 1448 s, 1425 s, 1394 s, 1319 s, 1293 s, 1248 s, 1187 s, 1155 s, 1122 s, 1098 s, 1059 s, 1003 s. (f) {Ag(bppz)[PhCB9H8Br]}, 6. Ag[PhCB9H8Br] (7.4 mg, 19.4 µmol) and bppz (4.7 mg, 20.0 µmol) were treated in the same way as for 1. The solution was left to stand uncovered, and after several days pale yellow crystals of 6 were obtained and isolated. Yield: 3.8 mg, 32%. Anal. Calcd for C21H23N4B9BrAg: C, 40.91; H, 3.77; N, 9.09. Found: C, 40.95; H, 3.50; N, 9.35. Selected IR (solid phase, cm-1): 3070 s, 3058 s, 2513 s, 2210 m, 2130 m, 2078 m, 1926 s, 1583 s, 1490 s, 1402 s, 1297 s, 1243 s, 1158 s, 1102 s, 1062 s, 1041 s, 1004 s. X-ray Data Collections and Structure Determinations. Single crystals of complexes 1-6 were mounted on glass fibers under oil, and X-ray diffraction data were collected with graphite-monochromated Mo KR radiation (λ ) 0.71073 Å) at 150(1) K on a Nonius Kappa CCD diffractometer with sealed-tube Mo source (complexes 1 and 3-6) and on a Bruker Apex II X8 diffractometer with a Mo rotating-anode source (complex 2). Data were corrected for Lorenztian and polarization effects, and absorption corrections were applied using multiscan methods. The structures were solved by direct methods using SHELXS9722 and refined by full-matrix least-squares on F2 using SHELXL97.23 C-H and B-H hydrogen atoms were included at calculated positions with a riding refinement. Unless indicated, all non-hydrogen atoms were refined anisotropically. Details of the data collections and structure refinements are given in Table 1. Two of the iodine atoms in complex 2 were both disordered over two positions. The occupancies were initially refined and then set at 0.94 and 0.06 for I(2) and I(2B), respectively, and at 0.54 and 0.46 for I(3) and I(3B), respectively. In complex 4 there is a symmetry-disordered acetonitrile molecule, which was refined isotropically, and its hydrogen atoms were excluded from the refinement. The high residual electron density in complex 6 was located close to Ag(1), and the high residuals are likely to be as a consequence of poor crystal quality as indicated by the high Rint value.

Results and Discussion [1-Ph-closo-1-CB9H8-6-Br]- was synthesized by the bromination of [1-Ph-closo-1-CB9H9]- with N-bromosuccinimide, and [1-Ph-closo-1-CB11H5-7,8,9,10,11,12-I6]- was made by the iodination of [PhCB11H11]- with iodine monochloride, ICl. [1-{4-Br-C6H4}-closo-1-CB11H11]- was made from the [6-{4BrC6H4}-nido-6-CB9H11]- anion by treatment with excess [BH3(SMe2)], the precursor anion [6-{4-BrC6H4}-nido-6-CB9H11]having been made from the treatment of nido-B10H14 with BrC6H4CHO in aqueous alkaline solution. An alternative synthetic route to the [PPh4]+ salt of [1-{4-Br-C6H4}-closo-1CB11H11]- has been published by Ko¨rbe et al.24 The molecular structures of these anions, taken from the previously deposited crystal structures of their [NEt4]+ salts,11 are shown in Figure 1. No significant intermolecular interactions were observed. The Ag(I) salts of the various HPC anions were allowed to react with the N-bridging ligands bpy and bppz, in various Ag/ ligand proportions, and using a variety of solvents, including ethanol, 2,2,2-trifluoroethanol, methanol, N,N-dimethylformamide, and acetonitrile. The reaction mixtures were allowed to evaporate slowly in a controlled way. Despite attempts using a number of different solvents and combinations of solvents, crystalline complexes were only obtained from acetonitrile solutions. The bridging bidentate ligand bpy with the carbaborane anions [PhCB9H9]-, [PhCB9H4I5]-, and [PhCB11H5I6]thence gave crystalline material of suitable quality for singlecrystal X-ray diffraction analysis, and the polydentate ligand bppz produced crystals of sufficient quality for crystallographic analysis in the presence of [PhCB9H9]-, [BrC6H4CB11H11]-, and [PhCB9H8Br]-. Complexes with bpy. Crystalline material of the complex [Ag(bpy)][PhCB9H9](CH3CN) 1 suitable for single-crystal X-ray analysis was isolated from a mixture of Ag[PhCB9H9] and bpy in an acetonitrile solution. The asymmetric unit of the crystal


Figure 2. Linear two-coordinate silver center in [Ag(bpy)][PhCB9H9] (CH3CN), 1. The CH3CN molecule and the [PhCB9H9]- anion are not close enough to show genuine coordinate bonds to the silver center. Ellipsoids are shown at 50% probability. Symmetry operations: (i) x, 1 + y, z; (ii) x - 1, 1 + y, z; (iii) 3/2 - x, 1/2 + y, 3/2 - z.

structure consists of a [PhCB9H9]- anion, a silver cation coordinated to a bpy ligand, and an uncoordinated acetonitrile solvent molecule. The Ag(I) has two coordinate bonds to two bpy ligands in a near-linear fashion, with an angle N(1)-Ag(1)-N(2) of 177.42(15)° and with Ag-N distances of Ag(1)N(1) 2.132(4) and Ag(1)-N(2) 2.144(5) Å, Figure 2. There are long contacts to an acetonitrile molecule, with a distance Ag‚ ‚‚NCCH3 of 2.867 Å, and to a [PhCB9H9]- anion with a distance B-H‚‚‚Ag of 2.611 Å. These contacts are too long for a genuine coordinative bonding interactions and, furthermore, would give a square-planar Ag(I) geometry, which is rare, with only a handful of examples of this unusual geometry reported: Constable et al. have reported 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,25 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) in which a square-planar unit involving Ag(I) was observed.26 In complex 1, each bpy ligand bridges between two Ag(I) centers to give an infinite linear coordination chain. The chains group together in pairs, with the Ag(I) center of one chain positioned directly above the center of the C4-C4′ bond of the 4,4′-bipyridine of the second chain at a closest Ag‚‚‚C distance of 3.585 Å, Figure 3. There are face-to-face π-stacking interactions between the arene rings of each chain at a centroid separation of 3.793 Å. We have recently reported the formation of straight-chain [Ag(bpy)]+ polymers with [Co(C2B9H11)2]counteranions, though in those cases the Ag(I) coordination spheres also featured terminal solvent ligand(s).5 These previously reported chains also feature π-stacking interactions between them, but with a different relative orientation between adjacent chains, in which the Ag(I) center of one chain is above an arene ring of another chain, either forming into pairs or infinite columns. In complex 1 the [PhCB9H9]- anions do not form any close interactions with other molecular components. The [PhCB9H9]- anions and CH3CN solvent molecules are arranged in a fashion that creates unidirectional channels of rhomboid cross section that run along the y-direction. These channels contain the [Ag(bpy)]+ coordination chains, Figure 3. Interestingly, this is the converse of what occurs with the previously reported [Ag(bpy)(CH3CN)][Co(C2B9H11)2] complexes, in which the [Ag(bpy)(CH3CN)]+ coordination chains pack to create unidirectional channels that contain the [Co(C2B9H11)2]- anions.5

Cunha-Silva et al.

Figure 3. Extended structure of complex 1 showing π-stacking pairs of [Ag(bpy)]+ chains (shown in green) that occupy channels created by the packing of the acetonitrile molecules and [PhCB9H9]- anions. Table 2. Selected Interatomic Distances and Angles for the bpy Complexes 2 and 3 distance/ angstroms Ag(1)-N(1) Ag(1)-N(2) Ag(1)-I(1) Ag(1)-I(2) Ag(1)-I(2B)

2.270(3) 2.270(3) 2.9853(5) 2.8638(7) 2.830(9)

Ag(1)-N(1) Ag(1)-N(3) Ag(1)-I(1) Ag(1)-I(6)

2.242(6) 2.274(6) 2.9214(9) 2.8170(8)

angles/ deg Complex 2 N(1)-Ag(1)-N(2) N(1)-Ag(1)-I(1) N(1)-Ag(1)-I(2) N(1)-Ag(1)-I(2B) N(2)-Ag(1)-I(1) N(2)-Ag(1)-I(2) N(2)-Ag(1)-I(2B) I(1)-Ag(1)-I(2) I(1)-Ag(1)-I(2)

127.42(11) 101.72(9) 114.52(8) 108.46(18) 96.69(8) 112.58(9) 120.35(16) 94.344(16) 90.19(15)

Complex 3 N(1)-Ag(1)-N(3) N(1)-Ag(1)-I(1) N(1)-Ag(1)-I(6) N(3)-Ag(1)-I(1) N(3)-Ag(1)-I(6) I(1)-Ag(1)-I(6)

119.5(2) 103.00(16) 105.65(17) 106.19(17) 121.46(18) 97.09(2)

Complex {Ag(bpy)[PhCB9H4I5]}(CH3CN) 2 was isolated in the form of single crystals from a mixture of Ag[PhCB9H4I5] and bpy in acetonitrile. The asymmetric unit of the crystal structure consists of a [PhCB9H4I5]- anion coordinated to the silver cation via two of its iodo groups, a bpy ligand also bound to the silver center, and an acetonitrile solvent molecule, all on general positions. Two iodine atoms are disordered, but only their major positions are shown in the figures for clarity. The silver center has distorted tetrahedral geometry, with selected interatomic distances and angles as given in Table 2. There are two symmetrically equivalent Ag-N bonds of 2.271(4) Å to bpy ligands. The silver coordination sphere is completed by two iodo groups of the chelating [PhCB9H4I5]- anion, which coordinates to the metal center at Ag-I distances of Ag(1)I(1) 2.9851(5) and Ag(1)-I(2) 2.8642(10) Å, Figure 4a. These distances are in keeping with literature precedent with, for example, Xie et al. reporting Ag-I distances between 2.856 and 3.256 Å in the crystal structure of Ag[CB11H5I6].(C6H6)0.5.14 The [Ag(bpy)]+ coordination chain formed by the silver in complex 1 is roughly linear, but in complex 2 the coordination chain is puckered to create a zigzag chain. At each silver center along the chain the coordinated [PhCB9H4I5]- anions point in alternating directions, Figure 4a. A very similar zig-zagging coordination chain is found with the larger [PhCB11H5I6]- anion in the complex {Ag(bpy)-


Figure 4. Ag(I) coordination environments and zig-zagging coordination chains of complexes 2 and 3: (a) from the complex {Ag(bpy)[PhCB9H4I5]}(CH3CN) 2 with only the major disordered iodine sites shown for the sake of clarity; (b) from the complex {Ag(bpy)[PhCB11H5I6]}(CH3CN) 3. Ellipsoids are shown at 50% probability with the symmetry operation code (i) 1 - x, 1/2 + y, 1/2 - z.

[PhCB11H5I6]}(CH3CN) 3, Figure 4b. Single crystals of 3 were prepared from the slow evaporation of a mixture of Ag[PhCB11H5I6] with bpy in acetonitrile. As with complex 2, each silver atom is coordinated through two Ag-N bonds of two crystallographically distinct bpy ligands at distances of Ag(1)N(1) 2.274(6) and Ag(1)-N(3) 2.242(7) Å and by a chelating interaction with the [PhCB11H5I6]- anion resulting from two Ag-I coordination bonds. Interatomic distances and angles around the distorted tetrahedral silver center are given in Table 2. Each bpy ligand bridges between two silver cations giving a zigzag coordination chain where the coordinated [PhCB11H5I6]anion points in two alternating directions above or below the chain, Figure 4b. Ag‚‚‚Ag distances within the chains are virtually the same for complexes 2 and 3 at 11.66 and 11.56 Å, respectively. The only major difference between the two [Ag(bpy)(HPC)]+ chains is that the arene rings of the bipy ligands are twisted away from one another in complex 2 (the torsion angle between C3-C4 and C3′-C4′ type bonds is around 31°), while they are nearly coplanar for complex 3.


Figure 5. Packing diagrams of (a) complex {Ag(bpy)[PhCB9H4I5]}(CH3CN) 2 viewed slightly displaced from the a-axis and (b) complex {Ag(bpy)[PhCB11H5I6]}(CH3CN) 3 viewed slightly displaced from the b-axis, showing the formation of unidirectional channels throughout the lattices that are occupied by CH3CN guest molecules (shown in space-filling mode).

The basic primary coordination complexes are very similar for complexes 2 and 3. However, the overall structures are not isomorphic, although there are strong similarities in the ways that the chains pack together for each complex. Chains with the same orientation stack in a translated manner and with a slight displacement normal to the translation, such that the phenyl group of the anion of one chain lies behind the silver center of another chain. This occurs in the ab plane for complex 2 with a closest C‚‚‚Ag approach of 3.633 Å and in the (101) plane for complex 3 with closest C‚‚‚Ag distance of 3.848 Å. The layers of coordination chains pack together to create unidirectional channels that run in the direction of the a-axis in the case of complex 2 and the direction of the b-axis in complex 3. These channels contain acetonitrile guest molecules, Figure 5. The relative disposition of these channels is quite distinct for each complex, with a checkerboard arrangement of channels in complex 2, Figure 5a, and a layered arrangement in complex 3, Figure 5b.


Cunha-Silva et al. Table 3. Selected Interatomic Distances and Angles for the bppz Complexes 4-6 distance/ angstroms Ag(1)-N(1) Ag(1)-N(2) Ag(1)-N(3) Ag(1)-N(4) Ag(1)‚‚‚H(101) Ag(1)‚‚‚H(103)

2.3248(19) 2.5929(18) 2.4344(19) 2.4310(18) 2.471 2.291

Ag(1)-N(8) Ag(1)-N(9) Ag(1)-N(11) Ag(1)-N(12) Ag(2)-N(1) Ag(2)-N(2) Ag(2)-N(5) Ag(2)-N(14)

2.356(3) 2.281(3) 2.388(3) 2.355(3) 2.389(3) 2.387(3) 2.353(3) 2.263(3)

Ag(1)-N(1) Ag(1)-N(2) Ag(1)-N(3) Ag(1)-Br(1)

2.332(10) 2.268(9) 2.372(9) 2.9382(11)

Figure 6. Coordination chain and Ag(I) coordination environment in complex {Ag(bppz)[PhCB9H9]}(CH3CN)0.5 4. Symmetry operation: (i) x, 3/2 - y, 1/2 + z.

All three Ag(I)/bpy complexes described here (1-3), as well as those we have previously reported,5 show 1D coordination polymers. The type of polymer formed seems dependent on whether the carbaborane anion binds to the silver center through a halogen site. Thus, the HPC anions bind through halogen to the silver atom and give zig-zagging chains, whereas the other types of (nonhalogenated) carbaborane anions do not bind to the silver atom, giving straight-chain polymers. Additionally, the identity of the carbaborane anion used affects the manner in which the chains pack together in the overall lattice. Presumably, one significant factor here is the steric bulk. It is also notable that, while straight-chain Ag(I)/bpy coordination polymers are relatively common,5,6 to the best of our knowledge these are the first examples of simple Ag(I)/bpy chains with a pronounced zigzag. Complexes with bppz. Crystals of complex {Ag(bppz)[PhCB9H9]}(CH3CN)0.5 4 were obtained by slow evaporation of a solution of Ag[PhCB9H9] and bppz in acetonitrile. The asymmetric unit of the crystal structure consists of a [PhCB9H9]anion, a silver cation, a bppz ligand, and a disordered acetonitrile molecule. The Ag(I) has a distorted six-coordinate geometry, arising from two bidentate chelating interactions with two symmetry-related bppz ligands with Ag-N distances in the range of 2.325(2) and 2.593(2) Å and from two Ag‚‚‚H-B interactions at distances of 2.291 Å [Ag(1)‚‚‚H(103)] and 2.471 Å [Ag(1)‚‚‚H(101)], both involving the same [PhCB9H9]- anion, Figure 6. The longest Ag‚‚‚H-B interactional distance reported in the recent literature is 2.51 Å.16 Interatomic distances and angles around the Ag(I) center are given in Table 3. The bppz ligand in complex 4 acts as a bis-chelating bridging ligand between the Ag(I) centers and thereby propagates a coordination chain that runs parallel with the crystallographic c-axis. Ag‚‚‚Ag separations within the chain are at 7.648 Å. There has been a handful of examples reported in the literature of the bppz ligand bridging in this simple bis-chelate mode to give polymeric coordination chains,27-29 though only species of the type [M(bppz)(H2O)2]2+, where M is Mn or Cu,27 have not involved a second type of bridging ligand. The coordinated [PhCB9H9]- anions of complex 4 are all on one side of the chain but show two alternating orientations along the chain, Figure 7. The chains stack with an identical orientation in the x-direction, such that the phenyl groups of the anions of one chain slot into the grooves created by the pyridine rings of the bppz ligands of an adjacent chain. The orientation of the chains alternates along the y-direction, Figure 7. There is a face-toface π-stacking interaction between two symmetry-related pyridine-type arene rings of the ligand at a centroid separation of 3.935 Å. The closest contact involving the carbaborane phenyl group is a long edge-to-face interaction between a C-H group of the symmetry-distinct pyridine ring and the anion phenyl ring at a C-H‚‚‚πcentroid distance of 2.931 Å and angle of 134.94°.

angles/ deg Complex 4 N(1)-Ag(1)-N(2) N(1)-Ag(1)-N(3) N(1)-Ag(1)-N(4) N(1)-Ag(1)‚‚‚H(101) N(1)-Ag(1)‚‚‚H(103) N(2)-Ag(1)-N(3) N(2)-Ag(1)-N(4) N(2)-Ag(1)‚‚‚H(101) N(2)-Ag(1)‚‚‚H(103) N(3)-Ag(1)-N(4) N(3)-Ag(1)‚‚‚H(101) N(3)-Ag(1)‚‚‚H(103) N(4)-Ag(1)‚‚‚H(101) N(4)-Ag(1)‚‚‚H(103) H(101)‚‚‚Ag(1)‚‚‚(H103)

68.94(6) 130.69(3) 127.06(7) 85.53 119.76 157.07(6) 90.05(6) 121.27 70.43 68.74(6) 76.53 101.77 142.98 94.98 79.59

Complex 5 N(8)-Ag(1)-N(9) N(8)-Ag(1)-N(11) N(8)-Ag(1)-N(12) N(9)-Ag(1)-N(11) N(9)-Ag(1)-N(12) N(11)-Ag(1)-N(12) N(1)-Ag(2)-N(2) N(1)-Ag(2)-N(5) N(1)-Ag(2)-N(14) N(2)-Ag(2)-N(5) N(2)-Ag(2)-N(14) N(5)-Ag(2)-N(14)

111.05(10) 102.47(10) 113.08(10) 132.18(11) 122.33(10) 69.52(10) 68.94(10) 102.38(10) 125.91(10) 99.40(10) 132.70(11) 116.54(10)

Complex 6 N(1)-Ag(1)-N(2) N(1)-Ag(1)-N(3) N(1)-Ag(1)-Br(1) N(2)-Ag(1)-N(3) N(2)-Ag(1)-Br(1) N(3)-Ag(2)-Br(1)

132.6(3) 71.8(3) 130.5(2) 136.1(3) 88.1(2) 99.4(2)

The crystalline complex 5, with composition [Ag2(bppz)3][BrC6H4CB11H11]2(CH3CN), was obtained from the reaction of Ag[BrPhCB11H11] and bppz in acetonitrile. The asymmetric unit of the structure consists of two [BrC6H4CB11H11]- anions, two silver cations, three bppz ligands, and an acetonitrile solvent

Figure 7. Extended structure of complex 4, viewed down the z-direction, with b running from left to right; for clarity, only the hydrogen atoms involved in Ag‚‚‚H-B are shown and the disordered CH3CN molecules have been excluded.


Figure 8. (a) Coordination environment of the silver centers in a fragment [Ag2(bppz)3]2+ of the complex [Ag2(bppz)3][BrC6H4CB11H11]2(CH3CN) 5; symmetry operations: (i) 1 - x, 1 - y, z and (ii) 1 - x, 1 - y, 1 - z. (b) Fragment of the infinite chain {[Ag2(bppz)3]2+}∞ in 5. For clarity, the hydrogen atoms are omitted and the two types of bppz ligands are shown in different colors.

molecule, all on general positions. Each silver center displays a distorted tetrahedral geometry and is coordinated by nitrogen atoms belonging to three different bppz molecules in total, with one chelating interaction per metallic center, Figure 8, with Ag-N distances in the range of 2.263(3)-2.389(3) Å, Table 3. Two types of ligands with different binding motifs can be distinguished. One bridges between two silver centers with a chelating interaction to one metal and a single bond through a pyridine nitrogen atom to the other. There are two such ligands, forming a double bridge between two adjacent silver atoms. The other type of bppz ligand forms a single bridge between two Ag(I) centers and coordinates only through its pyridine nitrogen atoms. Overall, an infinite coordination chain is formed with alternating Ag‚‚‚Ag distances of 5.166 and 7.716 Å, Figure 8. We have previously reported this type of [Ag2(bppz)3]2+ coordination chain with alternating single and double bridges, with the carbaborane counteranions [CB11H12]- and [Co(C2B9H11)2]-.5 In all three complexes, the coordination chains are virtually identical. In its extended structure, complex 5 has a layered motif. Coplanar layers of the [Ag2(bppz)3]2+ chains form in the ac plane through simple translation in the x-direction. Along the b-axis these alternate with a two-tiered layer of [BrC6H4CB11H11]anions. The two crystallographically independent [BrC6H4CB11H11]- anions are oriented with an approximately 80° rotation with respect to each other. There is a weak edgeto-face π-stacking interaction between a pyridyl group of the ligand and the phenyl group of the anion, with a C-H‚‚‚π distance of 2.544 Å, Figure 9. Crystalline material adequate for single-crystal X-ray diffraction experiments was isolated from a solution of Ag[PhCB9H8Br] and bppz in acetonitrile, yielding the complex {Ag(bppz)[PhCB9H8Br]} 6. The asymmetric unit of the crystal structure consists of a [PhCB9H8Br]- anion and a silver cation coordinated by a bppz ligand, all lying on general positions. The Ag(I) center has irregular tetrahedral geometry: Ag(I) coordinates with two bppz ligands, to form a chelating interaction to one ligand [Ag-N distances of Ag(1)-N(1) 2.332(10) and Ag(1)-N(3) 2.372(9) Å], with the third coordination bond


Figure 9. Packing diagram of complex [Ag2(bppz)3][BrC6H4CB11H11]2(CH3CN) 5, viewed down the a-axis.

Figure 10. Irregular tetrahedral geometry of the silver center in the dimeric unit of the {Ag(bppz)[PhCB9H8Br]} complex 6. Hydrogen atoms are not shown for clarity. Symmetry operation: (i) 1/2 - x, 1/2 y, 1 - z.

occurring to the pyridyl nitrogen atom of a second bppz ligand (Ag(1)-N(2) 2.268(9) Å). To complete the coordination environment, the bromo group of the [PhCB9H8Br]- anion coordinates at a Ag(1)-Br(1) distance of 2.9382(11) Å, Figure 10 and Table 3. In contrast with the other complexes reported here, a polymeric structure is not observed for complex 6, and, instead, a discrete dimeric species, {Ag(bppz)(PhCB9H8Br]}2, is formed, Figure 10. The ligand bridges between two symmetry-equivalent silver centers, with a bidentate chelate interaction to one silver center and a single bond through a pyridine nitrogen atom to the second silver center. There is a second, symmetry-related, ligand that behaves in the same way, thus forming a double bridge. This is a similar mode of coordination to that observed within the dimeric subunits of the coordination polymer of complex 5, Figure 8 above. A similarly doubly bridged [Cu2(bppz)2Br2] complex has also been reported.29 In the case of complex 6, the orientation of the [PhCB9H8Br]- anion appears to prevent the formation of a polymeric system with a higher silver coordination number. The bromo group is present on the cage in such a position that the anion can orient to form a face-


to-face π‚‚‚π stacking interaction between its phenyl group and the pyrazine ring of the bppz ligand (centroid separation is 3.846 Å). This may increase the stability of the discrete dimeric complex. All the complexes of the system Ag(I)/bppz (4-6) are structurally different, confirming the strong differential influences of the carbaborane anions in the coordination networks. The use of [PhCB9H8Br]- yields a discrete dimeric complex (6), in contrast to the carbaborane anions [PhCB9H9]- and [BrC6H4CB11H11]- which give the 1D coordination polymers, 4 and 5, respectively. However, complexes 4 and 5 differ considerably from each other. While in 4 the phenyl-carbaborane [PhCB9H9]- is part of the coordination chain through two Ag‚ ‚‚H-B interactions, in complex 5 the brominated anion [BrC6H4CB11H11]- behaves as a simple counteranion. Furthermore, the modes of coordination between the bppz and Ag(I) are different in both chains. As observed and described in our previous work on [Ag2(bppz)3]2+ coordination chains with [Co(C2B9H11)2]- or [CB11H12]- counteranions,5 in 5 there are two modes of coordination to the silver centers by the bppz ligand, but the coordination to the silver centers does not involve all the nitrogen atoms of the bppz ligand, contrasting with the structure of 4, where they are all involved. Conclusions Reactions in acetonitrile of the N-bridging ligands 4,4′bipyridine (bpy) or 2,3-bis-(2-pyridyl)pyrazine (bppz) with the Ag(I) salts of the C-phenyl-carbaborane anion [PhCB9H9]-, or the Ag(I) salts of the various halogenated anions [PhCB9H8Br]-, [BrC6H4CB11H11]-, [PhCB9H4I5]-, and [PhCB11H5I6]-, yield a set of new crystalline coordination-polymer materials. The materials prepared reveal a considerable tendency to form 1D topologies (chains), with the exception of {Ag(bppz)[PhCB9H8Br]}, compound 6, which crystallizes as a dimeric discrete complex. Although most of the coordination complexes have the same formal network topology, the coordination features and remaining structural characteristics are clearly influenced by the use of the different distinct carbaborane anions. Among the compounds of the Ag(I)/bpy system, the HPC anions [PhCB9H4I5]- and [PhCB11H5I6]- are coordinated in zigzag chains in the complexes {Ag(bpy)[PhCB9H4I5]}(CH3CN)} 2 and {Ag(bpy)[PhCB11H5I6]}(CH3CN) 3, respectively. Although the two HPC anions involved are different, the basic structures of 2 and 3 are very similar, representing the first examples of zigzagging Ag(I)/bpy 1D coordination polymers, and also representing rare examples in which the anions also coordinate to the metal atom.7 In the Ag(I)/bppz system the utilization of [PhCB9H9]- and [BrC6H4CB11H11]- anions also results in chain structures, but these are significantly different. In complex 4 the [PhCB9H9]- associates with the coordination chain through two Ag‚‚‚H-B interactions, while [BrC6H4CB11H11]- acts simply as a counteranion in 5. Furthermore, the modes of coordination between the bppz and Ag(I) are not the same in both chains. These results confirm the direct influence of the precise nature of anionic carbaborane anions upon the structures of coordination polymers that involve them: the anions can act as simple counteranions or as coordination agents, leading in both cases to the formation of new interesting structural and network variations. Considering the range of anionic carbaboranes available,11,12,30 it can be expected that exploration of other systems will yield further diverse coordination polymer materials with new framework topologies and potential applications. Acknowledgment. We thank the Fundaç aõ para a Cieˆncia e a Tecnologia, Ministe´rio da Cieˆncia, Tecnologia e Ensino

Cunha-Silva et al.

Superior, Portugal, for the fellowship to L.C.S. (SFRH/BPD/ 14410/2003), the U.K. EPSRC for DTA support (M.J.C.) and equipment funding, the U.K. DTI for support under the LINK ACCP scheme, and the University of Leeds for additional funding. Supporting Information Available: Crystallographic information files (CIF) for the structures of the complexes reported. This material is available free of charge via the Internet at http://pubs.acs.org.

References (1) (a) Steed, J. W.; Atwood, J. L. Supramolecular Chemistry; John Wiley & Sons Ltd.: Chichester, England, 2000. (b) Braga, D.; Grepioni, F.; Orpen, A. G. Crystal Engineering: From Molecules and Crystals to Materials; Kluwer Academic Publishers: Dordrecht, The Netherlands, 1999. (2) For review see: Carlucci, L.; Cianni, G.; Proserpio, D. M. Coord. Chem. ReV. 2003, 246, 247. (3) For recent reviews see: (a) Kitagawa, S.; Uemura, K. Chem. Soc. ReV. 2005, 34, 109. (b) Rowsell, J. L. C.; Yaghi, O. M. Angew. Chem., Int. Ed. 2005, 44, 4670. (c) Kitagawa, S.; Kitaura, R.; Noro, S.-i. Angew. Chem., Int. Ed. 2004, 43, 2334. (d) Kesanli, B.; Lin, W. Coord. Chem. ReV. 2003, 246, 305. (4) Tong, M.-L.; Wu, Y.-M.; Ru, J.; Chen, X.-M.; Chang, H.-C.; Kitagawa, S. Inorg. Chem. 2002, 41, 4846. (5) Cunha-Silva, L.; Ahmad, R.; Hardie, M. J. Aust. J. Chem. 2006, 59, 40. (6) For example, see: (a) Wang, R.; Hong, M.; Luo, J.; Jiang, F.; Han, L.; Lin, Z.; Cao, R. Inorg. Chim. Acta 2004, 357, 103. (b) Kokunov, Yu. V.; Khmelevskaya, L. V.; Gorbunova, Yu. E.; Mikhailov, Yu. N. Russ. J. Inorg. Chem. 2003, 48, 1452. (c) Sun, D.; Cao, R.; Sun, Y.; Bi, W.; Li, X.; Wang, Y.; Shi, Q.; Li, X. Inorg. Chem. 2003, 42, 7512. (d) Blake, A. J.; Baum, G.; Champness, N. R.; Chung, S. S. M.; Cooke, P. A.; Fenske, D.; Khlobystov, A. N.; Lemenovskii, D. A.; Li, W.-S.; Schro¨der, M. J. Chem. Soc., Dalton Trans. 2000, 4285. (7) (a) Wang, L.-S.; Yang, S.-P.; Zhang, J.-F. Acta Crystallogr., Sect. E 2005, 61, m25. (b) Sampanthar, J. T.; Vittal, J. J. Cryst. Eng. 2000, 3, 117. (8) For example, see: (a) Zhao, X.-L.; Mak, T. C. W. Polyhedron 2005, 24, 940. (b) Abrahams, B. F.; Batten, S. R.; Hoskins, B. F.; Robson, R. Inorg. Chem. 2003, 42, 2654. (c) Tong, M.-L.; Chen, X.-M.; Ng, S. W. Inorg. Chem. Commun. 2000, 3, 436. (d) Yaghi, O. M.; Li, H. J. Am. Chem. Soc. 1996, 118, 295. (e) Robinson, F.; Zaworotko, M. J. Chem. Commun. 1995, 2413. (f) Carlucci, L.; Ciani, G.; Proserpio, D. M; Sironi, A. Chem. Commun. 1994, 2755. (9) (a) Wang, Q.-M.; Mak, T. C. W. Inorg. Chem. 2003, 42, 1637. (b) Park, S. H.; Kim, Y. J.; Jung, O.-S. Bull. Korean Chem. Soc. 2002, 23, 629. (10) (a) Fox, M. A.; Hughes, A. K. Coord. Chem. ReV. 2004, 248, 457. (b) Grimes, R. N. Carboranes; Academic Press: New York, 1970. (c) Onak, T. In ComprehensiVe Organometallic Chemistry I; Abel, E. W., Wilkinson, G. W., Stone, F. G. A., Eds.; Pergamon: Oxford, England, 1982; Vol. 1, Chapter 5.4, pp 411-457. (d) Bregadze, V. Chem. ReV. 1992, 92, 209. (e) Sˇ tı´br, B. Chem. ReV. 1992, 92, 25. (f) Onak, T. In ComprehensiVe Organometallic Chemistry II; Abel, E. W., Wilkinson, G. W., Stone, F. G. A., Eds.; Pergamon: Oxford, England, 1995; Vol. 1, Chapter 6, pp 217-255. (11) For review see: Franken, A.; Kilner, C. A.; Thornton-Pett, M.; Kennedy, J. D. Collect. Czech. Chem. Commun. 2002, 67, 869 and references therein. (12) (a) Franken, A.; Kilner, C. A.; Thornton-Pett, M.; Kennedy, J. D. J. Organomet. Chem. 2002, 657, 176. (b) Franken, A.; Kilner, C. A.; Thornton-Pett, M.; Kennedy, J. D. J. Organomet. Chem. 2002, 657, 180. (c) Jelıńek, T.; Kilner, C. A.; Thornton-Pett, M.; Kennedy, J. D. Chem. Commun. 2001, 1790. (d) Franken, A.; Jelıńek, T.; Taylor, R. G.; Ormsby, D. L.; Kilner, C. A.; Thornton-Pett, M.; Kennedy, J. D. Dalton Trans. 2006, 5753. (e) Franken, A.; Kilner, C. A.; Thornton-Pett, M.; Kennedy, J. D. Chem. Commun. 2002, 2048. (13) (a) Xie, Z.; Jelinek, T.; Bau, R.; Reed, C. A. J. Am. Chem. Soc. 1994, 116, 1907. (b) Tsang, C.-T.; Yang, Q.; Sze, E. T.-P.; Mak, T. C. W.; Chan, D. T. W.; Xie, Z. Inorg. Chem. 2000, 39, 3582. (c) Xie, Z.; Tsang, C.-W.; Sze, E. T.-P.; Yang, Q.; Chan, D. T. W.; Mak, T. C. W. Inorg. Chem. 1998, 37, 6444. (14) Xie, L.; Wu, B.-M.; Mak, T. C. W.; Manning, J.; Reed, C. A. J. Chem. Soc., Dalton Trans. 1997, 1213. (15) Xie, Z.; Tsang, C.-W.; Xue, F.; Mak, T. C. W. J. Organomet. Chem. 1999, 577, 197.

Ag Complex One-Dimensional Coordination Polymers (16) (a) Patmore, N. J.; Hague, C.; Cotgreave, J. H.; Mahon, M. F.; Frost, C. G.; Weller, A. S. Chem. Eur. J. 2002, 8, 2088. (b) Ivanov, S. V.; Ivanova, S. M.; Miller, S. M.; Anderson, O. P.; Solntsev, K. A.; Strauss, S. H. Inorg. Chem. 1996, 35, 6914. (c) Shelly, K.; Finster, D. C.; Lee, Y. J.; Scheidt, W. R.; Reed, C. A. J. Am. Chem. Soc. 1985, 107, 5955. (d) Tsang, C.-T.; Sun, J.; Xie, Z. J. Organomet. Chem. 2000, 613, 99. (17) Westcott, A.; Whitford, N.; Hardie, M. J. Inorg. Chem. 2004, 43, 3663. (18) (a) Ahmad, R.; Franken, A.; Kennedy, J. D.; Hardie, M. J. Chem. Eur. J. 2004, 10, 2190. (b) Ahmad, R.; Hardie, M. J. New J. Chem. 2004, 28, 1315. (19) Ivanov, S. V.; Miller, S. M.; Anderson, O. P.; Strauss, S. H. Cryst. Growth Des. 2004, 4, 249. (20) For examples, see: (a) Sumby, C. J.; Fisher, J.; Prior, T. J.; Hardie, M. J. Chem. Eur. J. 2006, 12, 2945. (b) Sumby, C. J.; Hardie, M. J. Cryst. Growth Des. 2005, 5, 1321. (c) Hardie, M. J.; Sumby, C. J. Inorg. Chem. 2004, 43, 6872. (d) Malic, N.; Nichols, P.; Raston, C. L. Chem. Commun. 2002, 16. (e) Hardie, M. J.; Raston, C. L. Cryst. Growth Des. 2001, 1, 53. (f) Long, D.-L.; Blake, A. J.; Champness, N. R.; Wilson, C.; Schro¨der, M. Angew. Chem., Int. Ed. 2001, 40, 2444. (g) Hardie, M. J.; Raston, C. L. Angew. Chem., Int. Ed. 2000, 39, 3835. (21) Sumby, C. J.; Carr, M. J.; Franken, A.; Kennedy, J. D.; Kilner, C. A.; Hardie, M. J. New J. Chem. 2006, 30, 1390. (22) Sheldrick, G. M. SHELXS-97; University of Go¨ttingen: Go¨ttingen, Germany, 1997. (23) Sheldrick, G. M. SHELXL-97; University of Go¨ttingen: Go¨ttingen, Germany, 1997.

Crystal Growth & Design, Vol. 7, No. 4, 2007 667 (24) Ko¨rbe, S.; Sowers, D. B.; Franken, A.; Michl, J. Inorg. Chem. 2004, 43, 8158. (25) Constable, E. C.; Housecroft, C. E.; Kariuki, B. M.; Kelly, N.; Smith, C. B. Inorg. Chem. Commun. 2002, 5, 199. (26) Constable, E. C.; Edwards, A. J.; Haire, G. R.; Hannon, M. J. Polyhedron 1998, 17, 243. (27) (a) Armentano, D.; de Munno, G.; Guerra, F.; Faus, J.; Lloret, F.; Julve, M. Dalton Trans. 2003, 4626. (b) Grove, H.; Sletten, J.; Julve, M.; Lloret, F.; Lezama, L. Inorg. Chim. Acta 2000, 310, 217. (c) Morgan, L. W.; Goodwin, K. V.; Pennington, W. T.; Peterson, J. D. Inorg. Chem. 1992, 31, 1103. (28) Grove, H.; Sletten, J.; Julve, M.; Lloret, F. Dalton Trans. 2001, 2487. (29) Chesnut, D. J.; Kusnetzow, A.; Birge, R. R.; Zubieta, J. Inorg. Chem. 1999, 38, 2663. (30) For example, see: (a) Jelinek, T.; Kilner, C. A.; Thornton-Pett, M.; Kennedy, J. D. Chem. Commun. 2001, 1790. (b) Tsang, C.-W.; Yang, Q.; Sze, E. T.-P.; Mak, T. C. W.; Chan, D. T. W.; Xie, Z. Inorg. Chem. 2000, 39, 5851. (c) Mortimer, M. D.; Knobler, C. B.; Hawthorne, M. F. Inorg. Chem. 1996, 35, 5750. (d) Jelıńek, T.; Baldwin, P.; Scheidt, W. R.; Reed, C. A. Inorg. Chem. 1993, 32, 1982. (e) Franken, A.; Carr, M. J.; Clegg, W.; Kilner, C. A.; Kennedy, J. D., Dalton Trans. 2004, 3552. (f) Bullen, N. J.; Franken, A.; Kilner, C. A.; Kennedy, J. D. Chem. Commun. 2003, 1684. (g) Franken, A.; Kilner, C. A.; Kennedy, J. D. Inorg. Chem. Commun. 2003, 6, 1104.

CG070048P

One-Dimensional Coordination Polymers with Phenyl-carbaborane

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