Tuning the Structures of Mercury Cyanide-Based Coordination

May 5, 2004 - Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia, V5A 1S6, Canada. Crystal Growth & De...
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Tuning the Structures of Mercury Cyanide-Based Coordination Polymers with Transition Metal Cations Neil D. Draper, Raymond J. Batchelor, and Daniel B. Leznoff* Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia, V5A 1S6, Canada

CRYSTAL GROWTH & DESIGN 2004 VOL. 4, NO. 3 621-632

Received December 5, 2003

ABSTRACT: A series of complexes containing [MLx]Cl2 (M ) Mn, Cu, Ni; L ) 2,2′-bipyridine (bipy), 1,10phenanthroline (phen), 2,2′:6′,6′′-terpyridine (terpy), diethylenetriamine (dien), tris(2-aminoethyl)amine (tren); x ) 1 or 2) and linear, neutral Hg(CN)2 building blocks have been synthesized and structurally characterized. In general, the Lewis acidic Hg(CN)2 moieties accept chloride ligands from the M(II) centers, in several cases increasing the structural dimensionality of the system as a result. [ML2(µ-Cl)2Hg(CN)2] (M ) Mn, Ni; L ) bipy, phen) (1-4) are molecular complexes in which the chloride ligands bridge the M(II) and mercury(II) centers; π‚‚‚π stacking between the aromatic rings from different molecules increases the structural dimensionality. [Cu(terpy)Cl2(µ-Hg(CN)2)] (5) is an alternating 1-D chain of Cu(terpy)Cl2 and Hg(CN)2 moieties in which the chloride ligands bridge to different mercury(II) centers. When two phen ligands are used with copper(II), an additional Hg(CN)2 unit is incorporated to form {[Cu(phen)2Cl]2Hg(CN)2[Hg(CN)2Cl]2} (6), an alternating 1-D chain of [Hg(CN)2Cl]22- dimers that are N-bound to Hg(CN)2 units that also bind to dangling [Cu(phen)2Cl]+ moieties. In [Cu(dien)Cl][Hg(CN)2Cl] (7), 1-D chloride bridged [Hg(CN)2Cl]nn- double salt chains formed in situ during polymer formation are held in place by chloride bridged [Cu(dien)Cl]22+ cationic dimers to form a 2-D brick-wall layer motif. Two 1-D double salt chains, one cationic and one anionic, which hydrogen bond together to form neutral columns are generated in [Cu(tren)Hg(CN)2Cl][HgX2Cl] (8). N-cyano coordination and chloride bridging from Hg(CN)2 and chloride ligands in {[Ni(tren)]4[Hg(CN)2]8Cl6}HgCl4 (9) generate 1-D cationic columns of {[Ni(tren)]4[Hg(CN)2]8Cl6}n2n+ which hydrogen bond to tetrahedral [HgCl4]2- moieties, increasing the structural dimensionality of this noncentrosymmetric complex. Factors influencing the structural dimensionality and the induction of N-cyano bridging are discussed. Introduction The use of bridging cyanometallate units, in concert with coordinately unsaturated complexes of simple transition metal ions to create multidimensional supramolecular polymers, is of great current interest.1-5 The alteration of the metal center in [M(CN)n]x- building blocks, and the consequent adjustment of the geometric, magnetic, and electronic properties, provides the control and flexibility required to assemble solids with tunable properties.1-5 Novel physical properties are not the sole reason for pursuing the synthesis of bimetallic coordination polymerssthe propagation of structural preferences of two different metal centers in bimetallic systems results in a broader spectrum of polymer structural motifs than is achievable in unimetallic systems.6-9 Compared with octahedral, tetrahedral, and square planar cyanometallates, linear metal cyanides have been relatively neglected as structural building blocks in the formation of coordination polymers. Our previous studies with anionic [M(CN)2]- units (M ) Au, Ag) have shown that these linear cyanometallates are capable of increasing structural dimensionality by forming metallophilic (M‚‚‚M) interactions and also propagate significant magnetic interactions.10-13 We are currently examining the use of mercury(II) cyanide, Hg(CN)2, a virtually unexplored, linear, but neutral building block, to create supramolecular architectures.14,15 We have demonstrated that Hg(CN)2 units can be incorporated * Corresponding author. Tel: 1-604-291-4887; fax: 1-604-2913765; e-mail: [email protected].

into coordination polymers via bridging cyano groups that link to a coordinately unsaturated transition metal center as found in {Cu(tmeda)[Hg(CN)2]2}[HgCl4], a noncentrosymmetric two-dimensional layer system that shows strong optical anisotropy (tmeda ) N,N,N′,N′tetramethylethylenediamine).14 The Hg(CN)2 unit is also known to react with simple salts such as MX (M ) Na, K, Rb, Cs; X ) NCO, NCS, N3, CN, Cl, Br, I; sometimes HgX2 is also added), to yield solid-state “double salt” arrays of the form Mn+Hg(CN)2Xn (n ) 1, 2).16,17 In these reactions, the Lewis-acidity of the Hg(II) center is the key feature controlling the reactivity. Thus, the coordinately unsaturated Hg(II) center can accept compatible ligands during polymer formation to form square-planar, tetrahedral, or higher coordinate moieties in situ, in some cases increasing the structural and magnetic dimensionality of the system as result.15 This formation of double salt mercurate moieties invokes competition between halide and N-cyano coordination to the transition metal complex, with higher dimensionality typically achieved when cyano coordination occurs. In addition, the cyano-nitrile donors of the Hg(CN)2 unit, if not bound to another metal, can participate in hydrogen bonding. There may be either simple or bifurcated hydrogen bonds of the CN‚‚‚H-X type (where X is an electronegative atom) and can play an important role in the packing and stabilization of the structures formed.18,19 Such N-cyano hydrogen bonding has also been proposed as a possible exchange path for magnetic interactions.20,21 We report here the synthesis, structural, and magnetic properties of a series of LxM(II) complexes (L )

10.1021/cg034248m CCC: $27.50 © 2004 American Chemical Society Published on Web 05/05/2004

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bipy, phen, terpy, dien, tren; x ) 1 or 2; M(II) ) Mn, Ni, Cu) that have been reacted with coordinately unsaturated Hg(CN)2 to generate transition metal organoamine-double salt mercurates with several different structural motifs including one-dimensional chains, ribbons and columns, 2-D layers, and 3-D extended structures. We investigate the possible factors influencing Hg(CN)2 nitrile-coordination to transition metal complex cations in the presence of chloride ligands, including transition metal used, the number of open sites available for binding, and ligand basicity. Experimental Procedures General Procedures and Physical Measurements. All manipulations were performed in air using purified solvents. All reagents were obtained from commercial sources and used as received. IR spectra were obtained using a Thermo Nicolet 670 FT-IR spectrometer. Microanalyses (C, H, N) were performed at Simon Fraser University by Mr. Miki Yang. Magnetic susceptibility data were collected using a Quantum Design MPMS-5S or Evercool XL-7 magnetometer working down to 2 or 1.8 K at a 1 T field strength. Sample 5 was measured in a cylindrical, airtight sample holder constructed from PVC,22 while 6 and 7 were measured in low background gel caps and straws. The data were corrected for TIP, the diamagnetism of the sample holder and the constituent atoms (by use of Pascal constants).23 Synthetic Procedures. [Mn(bipy)2(µ-Cl)2Hg(CN)2] (1). To a 5 mL methanolic solution of MnCl2‚4H2O (0.078 g, 0.39 mmol), a 10 mL methanolic solution of bipy (0.124 g, 0.79 mmol) was added. While the sample was stirred, a 5 mL methanolic solution of Hg(CN)2 (0.100 g, 0.40 mmol) was added to this pale yellow solution. After the mixture was left covered for 1 day, small yellow crystal bars of [Mn(bipy)2(µ-Cl)2Hg(CN)2] (1) were collected by vacuum filtration, washed with cold methanol, and were left to air-dry. Yield: 0.186 g (68.3%). Anal. Calcd. for C22H16N6Cl2HgMn: C, 38.25; H, 2.33; N, 12.16. Found: C, 38.09; H, 2.25: N, 11.82. IR (KBr, cm-1): 3190 (w), 3106 (m), 3073 (m), 3060 (m), 3031 (w), 2983 (w), 2950 (w), 2180 (vw), 2147 (vw), 2040 (w), 1996 (w), 1960 (m), 1923 (w), 1887 (w), 1853 (w), 1617 (m), 1602 (s), 1596 (s), 1574 (m), 1563 (m), 1539 (w), 1507 (m), 1492 (s), 1477 (s), 1443 (s), 1399 (m), 1363 (w), 1340 (w), 1317 (m), 1283 (w), 1249 (m), 1218 (w), 1184 (m), 1160 (s), 1120 (w), 1102 (m), 1074 (m), 1062 (s), 1041 (w), 1015 (s), 962 (w), 910 (w), 892 (m), 816 (m), 773 (s), 766 (s), 738 (s), 649 (s), 627 (m), 412 (s). [Mn(phen)2(µ-Cl)2Hg(CN)2] (2). To a 5 mL methanolic solution of MnCl2‚4H2O (0.078 g, 0.39 mmol), a 10 mL methanolic solution of phen (0.157 g, 0.79 mmol) was added. While the sample was stirred, a 5 mL aqueous solution of Hg(CN)2 (0.100 g, 0.40 mmol) was added to this pale yellow solution. After the mixture was left covered for 1 day, small yellow crystal bars of [Mn(phen)2(µ-Cl)2Hg(CN)2] (2) were collected by vacuum filtration, washed with cold methanol, and left to air-dry. Yield: 0.232 g (80.0%). Anal. Calcd. for C26H16N6Cl2HgMn: C, 42.26; H, 2.18; N, 11.37. Found: C, 42.43; H, 2.25: N, 11.11. IR (KBr, cm-1): 3734 (w), 3093 (w), 3051 (m), 3018 (w), 2994 (w), 2940 (w), 2915 (w), 2877 (w), 2830 (w), 2650 (w), 2620 (w), 2600 (w), 2180 (vw), 1983 (m), 1837 (w), 1803 (w), 1777 (w), 1625 (s), 1589 (s), 1576 (m), 1540 (m), 1514 (s), 1499 (m), 1456 (m), 1425 (vs), 1363 (w), 1341 (m), 1302 (w), 1260 (w), 1228 (w), 1149 (m), 1104 (s), 1088 (w), 1031 (w), 985 (w), 940 (w), 898 (w), 864 (vs), 857 (vs), 785 (m), 730 (vs), 723 (vs), 639 (m), 555 (w), 510 (w), 474 (w), 421 (s). [Ni(bipy)2(µ-Cl)2Hg(CN)2] (3). To a 5 mL aqueous solution of NiCl2‚6H2O (0.094 g, 0.40 mmol), a 10 mL methanolic solution of bipy (0.124 g, 0.79 mmol) was added. After reducing the total volume to 5 mL, a 5 mL aqueous solution of Hg(CN)2 (0.100 g, 0.40 mmol) was added to this pale purple solution with stirring. The mixture was allowed to slowly evaporate. Small pale green crystal blocks of [Ni(bipy)2(µ-Cl)2Hg(CN)2] (3) were collected by vacuum filtration, washed with cold H2O

Draper et al. followed by cold methanol, and left to air-dry. Yield: 0.154 g (55.9%). Anal. Calcd. for C22H16N6Cl2HgNi: C, 38.04; H, 2.32; N, 12.01. Found: C, 37.87; H, 2.32: N, 11.88. IR (KBr, cm-1): 3199 (w), 3108 (m), 3078 (m), 3057 (m), 3035 (m), 2986 (w), 2963 (w), 2913 (w), 2882 (w), 2777 (w), 2677 (w), 2627 (w), ν(CN) 2172 (m), 2150 (w), 2040 (w), 1994 (w), 1963 (w), 1917 (w), 1887 (w), 1850 (w), 1783 (w), 1678 (w), 1617 (m), 1600 (s), 1566 (m), 1537 (m), 1507 (m), 1494 (s), 1475 (s), 1449 (s), 1417 (m), 1403 (w), 1360 (w), 1316 (s), 1283 (m), 1251 (m), 1223 (w), 1181 (m), 1162 (s), 1125 (w), 1107 (m), 1060 (m), 1043 (m), 1023 (s), 999 (m), 960 (m), 905 (m), 892 (m), 815 (s), 768 (s), 736 (s), 654 (s), 664 (m), 462 (w), 449 (m), 441 (m), 418 (s), 414 (s). [Ni(phen)2(µ-Cl)2Hg(CN)2] (4). To a 5 mL aqueous solution of NiCl2‚6H2O (0.094 g, 0.40 mmol), a 10 mL methanolic solution of phen (0.157 g, 0.79 mmol) was added. After reducing the total volume to 5 mL, a 5 mL aqueous solution of Hg(CN)2 (0.100 g, 0.40 mmol) was added to this pink solution with stirring. The mixture was allowed to slowly evaporate. Small pale blue crystal platelets of [Ni(phen)2(µ-Cl)2Hg(CN)2] (4) were collected by vacuum filtration, washed with cold H2O followed by cold methanol, and left to air-dry. Yield: 0.182 g (61.9%). Anal. Calcd. for C22H16N6Cl2HgNi: C, 42.05; H, 2.17; N, 11.32. Found: C, 41.79; H, 2.21: N, 11.21. IR (KBr, cm-1): 3090 (w), 3053 (m), 3019 (w), 2990 (w), 2923 (w), 2881 (w), 2173 (w), 1994 (m), 1886 (w), 1842 (w), 1803 (w), 1777 (w), 1716 (w), 1626 (m), 1600 (m), 1580 (m), 1539 (m), 1514 (s), 1500 (m), 1456 (m), 1426 (s), 1342 (m), 1307 (m), 1256 (w), 1230 (m), 1201 (w), 1150 (s), 1107 (m), 1050 (m), 986 (m), 945 (w), 905 (w), 869 (s), 857 (vs), 812 (w), 786 (s), 728 (vs), 643 (m), 509 (w), 484 (w), 425 (s), 414 (m), 404 (m). [Cu(terpy)Cl2(µ-Hg(CN)2)] (5). To a 10 mL aqueous solution of CuCl2‚2H2O (0.075 g, 0.44 mmol), a 5 mL methanolic solution of terpy (0.103 g, 0.44 mmol) was added. While stirring, a 5 mL aqueous solution of Hg(CN)2 (0.112 g, 0.44 mmol) was added to the green solution. The mixture was allowed to slowly evaporate. Large dark green crystal bars of [Cu(terpy)Cl2(µ-Hg(CN)2)] (5) were collected by vacuum filtration, washed with cold H2O followed by cold methanol, and left to air-dry. Yield: 0.252 g (91.0%). Anal. Calcd. for C17H15N5Cl2CuHg: C, 32.92; H, 1.72; N, 11.29. Found: C, 33.20; H, 1.79; N, 11.14. IR (KBr, cm-1): 3195 (w), 3137 (w), 3074 (m), 3035 (w), 2997 (w), 2927 (w), 2860 (w), 2770 (w), 2177 (vw), 2037 (w), 1936 (w), 1893 (w), 1860 (w), 1807 (w), 1764 (w), 1599 (s), 1574 (m), 1566 (m), 1539 (w), 1500 (m), 1475 (s), 1450 (s), 1419 (m), 1410 (m), 1387 (m), 1363 (w), 1328 (s), 1302 (s), 1289 (m), 1255 (s), 1244 (m), 1187 (m), 1176 (m), 1141 (w), 1118 (w), 1098 (m), 1070 (m), 1038 (m), 1021 (s), 1009 (m), 978 (w), 902 (w), 834 (m), 784 (vs), 734 (s), 726 (m), 671 (m), 651 (s), 539 (w), 515 (m), 438 (m), 423 (m), 411 (m). {[Cu(phen)2Cl]2Hg(CN)2[Hg(CN)2Cl]2} (6). To a 10 mL aqueous solution of CuCl2‚2H2O (0.135 g, 0.79 mmol), a 20 mL methanolic solution of phen (0.314 g, 1.58 mmol) was added. While the sample was stirred, a 15 mL aqueous solution of Hg(CN)2 (0.300 g, 1.19 mmol) was added to this green solution. After the mixture was left covered for 1 day, small green crystal platelets of {[Cu(phen)2Cl]2Hg(CN)2[Hg(CN)2Cl]2} (6) were collected by vacuum filtration, washed with cold methanol, and left to air-dry. Crystals suitable for X-ray crystallographic studies were obtained upon slow evaporation of the solution mixture. Yield: 0.594 g (85.8%). Anal. Calcd. for C54H32N14Cl4Cu2Hg3: C, 37.11; H, 1.85; N, 11.22. Found: C, 37.09; H, 1.94; N, 11.05. IR (KBr, cm-1): 3092 (m), 3070 (m), 3059 (m), 3013 (m), 2621 (w), 2513 (w), 2293 (w), ν(CN) 2166 (m), 2000 (w), 1975 (w), 1955 (w), 1936 (w), 1899 (w), 1833 (w), 1809 (w), 1783 (w), 1760 (w), 1627 (m), 1608 (m), 1582 (s), 1519 (s), 1495 (s), 1456 (m), 1427 (vs), 1341 (m), 1322 (m), 1312 (m), 1255 (w), 1224 (s), 1208 (m), 1145 (s), 1106 (s), 1037 (w), 1004 (w), 987 (m), 952 (m), 911 (w), 870 (s), 854 (vs), 846 (vs), 787 (m), 774 (m), 724 (vs), 649 (s), 557 (w), 508 (w), 430 (s), 417 (m). [Cu(dien)Cl][Hg(CN)2Cl] (7). To a 5 mL methanolic solution of CuCl2‚2H2O (0.067 g, 0.39 mmol), a 10 mL methanolic solution of dien (0.041 g, 0.39 mmol) was added. While the sample was stirred, a 5 mL methanolic solution of Hg-

Mercury Cyanide-Based Coordination Polymers (CN)2 (0.100 g, 0.40 mmol) was added to this dark blue solution. The mixture was allowed to slowly evaporate. Dark blue crystal bars of [Cu(dien)Cl][Hg(CN)2Cl] (7) were collected by vacuum filtration, washed with cold methanol, and left to air-dry. Yield: 0.133 g (69.0%). Anal. Calcd. for C6H13N5Cl2CuHg: C, 14.70; H, 2.67; N, 14.29. Found: C, 14.80; H, 2.79; N, 14.05. IR (KBr, cm-1): 3286 (vs), 3244 (vs), 3234 (vs), 3136 (m), 2971 (m), 2959 (m), 2918 (w), 2884 (m), ν(CN) 2178 (w), 1844 (w), 1830 (w), 1712 (s), 1636 (w), 1594 (m), 1580 (m), 1460 (m), 1436 (m), 1362 (m), 1318 (w), 1301 (w), 1223 (m), 1136 (m), 1124 (m), 1092 (s), 1024 (s), 1000 (m), 954 (s), 922 (w), 882 (w), 833 (w), 659 (m), 637 (w), 529 (m), 460 (w). [Cu(tren)Hg(CN)2Cl][HgX2Cl] (8). To a 5 mL aqueous solution of CuCl2‚2H2O (0.067 g, 0.39 mmol), a 20 mL aqueous solution of tren (0.058 g, 0.39 mmol) was added. While the sample was stirred, a 5 mL aqueous solution of Hg(CN)2 (0.200 g, 0.80 mmol) was added to this solution. The mixture was allowed to slowly evaporate. Blue crystal bars of [Cu(tren)Hg(CN)2Cl][HgX2Cl] (8) were collected by vacuum filtration, washed with cold H2O, and left to air-dry. Yield: 0.115 g (55.6%). Anal. Calcd. for C9H18N7Cl3CuHg2: C, 13.59; H, 2.28 N, 12.33. Found: C, 13.94; H, 2.26; N, 12.48. IR (KBr, cm-1): 3351 (vs), 3293 (s), 3293 (vs), ν(CN) 2214 (m), 2178 (w), 1631 (m), 1587 (s), 1480 (m), 1450 (m), 1389 (w), 1311 (m), 1271 (w), 1226 (w), 1117 (m), 1059 (s), 1038 (m), 1013 (m), 992 (s), 902 (m), 867 (m), 748 (w), 665 (w), 616 (w), 545 (m), 476 (m), 419 (vs). {[Ni(tren)]4[Hg(CN)2]8Cl6}HgCl4 (9). To a 5 mL aqueous solution of NiCl2‚6H2O (0.094 g, 0.40 mmol), a 20 mL aqueous solution of tren (0.058 g, 0.39 mmol) was added. While the sample was stirred, a 5 mL aqueous solution of Hg(CN)2 (0.200 g, 0.79 mmol) was added to this solution, followed by a dropwise addition of a 5 mL aqueous solution of HgCl2 (0.027 g, 0.01 mmol). The mixture was allowed to slowly evaporate. Purple crystal bars of {[Ni(tren)]4[Hg(CN)2]8Cl6}HgCl4 (9) were collected by vacuum filtration, washed with cold H2O, and left to air-dry. Yield: 0.228 g (67.5%). Anal. Calcd. for C40H72N32Cl10Hg9Ni4: C, 14.15; H, 2.14; N, 13.20. Found: C, 14.01; H, 2.23; N, 13.09. IR (KBr, cm-1): 3338 (s), 3309 (m), 3277 (m), 3259 (m), 3176 (m), 2990 (m), 2943 (w), 2930 (w), 2905 (m), 2865 (s), ν(CN) 2215 (m), 2184 (vw), 1987 (w), 1880 (w), 1598 (vs), 1581 (vs), 1539 (m), 1479 (s), 1470 (s), 1397 (w), 1373 (w), 1347 (m), 1329 (m), 1318 (m), 1254 (m), 1236 (m), 1167 (m), 1140 (m), 1107 (m), 1081 (s), 1053 (s), 1036 (m), 1026 (s), 996 (s), 980 (vs), 896 (m), 880 (s), 852 (m), 748 (m), 650 (m), 615 (s), 583 (w), 560 (w), 538 (s), 516 (w), 460 (s). X-ray Crystallographic Analysis of 1-9. Crystallographic data for structures 1-9 are collected in Tables 1 (14) and 2 (5-9). All crystals were mounted on glass fibers using epoxy adhesive. Crystal descriptions for each compound are as follows: 1 was a yellow platelet having dimensions 0.06 × 0.17 × 0.43 mm3; 2 was a yellow block having dimensions 0.10 × 0.17 × 0.20 mm3; 3 was a pale green block having dimensions 0.06 × 0.09 × 0.20 mm3; 4 was a pale blue platelet having dimensions 0.06 × 0.17 × 0.20 mm3; 5 was a dark green block having dimensions 0.17 × 0.29 × 0.57 mm3; 6 was a green platelet having dimensions 0.07 × 0.29 × 0.43 mm3; 7 was a dark blue platelet having dimensions 0.07 × 0.17 × 0.40 mm3; 8 was a blue platelet having dimensions 0.06 × 0.09 × 0.51 mm3; and 9 was a purple block having dimensions 0.11 × 0.14 × 0.43 mm3. The data for 1 and 5-9 were collected at room temperature using the diffractometer control program DIFRAC24 and an Enraf Nonius CAD4F diffractometer employing graphite monochromated Mo KR radiation. The following data ranges were recorded: 1 ) 4° e 2θ e 54°; 5 ) 4° e 2θ e 51°; 6 ) 4° e 2θ e 56°; 7 ) 4° e 2θ e 52°; 8 ) 4° e 2θ e 55°; 9 ) 4° e 2θ e 50°. The data were corrected for the effects of absorption using a semiempirical psi-scan method with the following transmission ranges: 1 ) 0.1358-0.2317; 5 ) 0.1237-0.2273; 6 ) 0.0773-0.2979; 7 ) 0.0883-0.1857; 8 ) 0.1406-0.2328; 9 ) 0.0858-0.1489. Data reduction for all compounds included corrections for Lorentz and polarization effects. Final unit-cell dimensions were determined based on the following well-centered reflections: 1 ) 76 reflections with range 40° e 2θ e 54°; 5 ) 20 reflections with range 33° e 2θ

Crystal Growth & Design, Vol. 4, No. 3, 2004 623 e 35°; 6 ) 16 reflections with range 30° e 2θ e 35°; 7 ) 36 reflections with range 48° e 2θ e 52°; 8 ) 38 reflections with range 38° e 2θ e 44°; 9 ) 40 reflections with range 33° e 2θ e 34°. The data for 2-4 was acquired on a Rigaku RAXIS-Rapid curved image plate area detector with graphite monochromated Cu KR radiation at room temperature. Indexing was performed from three, 5° oscillations that were exposed for 90 s. The following data ranges were recorded: 2 ) 6.9° e 2θ e 136.5°; 3 ) 11.0° e 2θ e 136.5°; 4 ) 10.0° e 2θ e 136.5°. A total of 18 images were collected for 2 and 27 images each for 3 and 4. A sweep of data for 2 was done using ω scans from 50.0 to 230.0 in 30° steps, at χ ) 50.0° and φ ) 0.0°. A second sweep was performed using ω scans from 50.0 to 230.0 in 30° steps, at χ ) 50.0° and φ ) 90.0°. A final sweep was performed using ω scans from 50.0 to 230.0 in 30° steps, at χ ) 50.0° and φ ) 180.0°. A sweep of data for 3 and 4 was done using ω scans from 50.0 to 230.0 in 20° steps, at χ ) 50.0° and φ ) 0.0°. A second sweep was performed using ω scans from 50.0 to 230.0 in 20° steps, at χ ) 50.0° and φ ) 90.0°. A final sweep was performed using ω scans from 50.0 to 230.0 in 20° steps, at χ ) 50.0° and φ ) 180.0°. The exposure rate for 2-4 was 90 s/°. In each case, the crystal-to-detector distance was 127.40 mm. An empirical absorption correction was applied which resulted in the following transmission ranges: 2 ) 0.3388-1; 3 ) 0.2363-1; 4 ) 0.2718-1.25 For compounds 1-7 coordinates and anisotropic displacement parameters for the non-hydrogen atoms were refined; for compound 8, the cyano carbon and nitrogen atoms of partial occupancy were refined using isotropic thermal parameters; and for compound 9, all of the cyano carbon and nitrogen atoms were refined using isotropic thermal parameters. For structure 8, the C-N and Hg-C bond lengths for the cyano groups of partial occupancy were restrained to be 1.050(5) and 2.050(5) Å, respectively, and a vibrational restraint was applied between the Hg(2) center and the Cl groups of partial occupancy. For all compounds, hydrogen atoms were placed in calculated positions (d C-H 0.95 Å; d N-H 0.93 Å) and their coordinate shifts were linked with those of the respective carbon or nitrogen atoms during refinement. Isotropic thermal parameters for the hydrogen atoms were initially assigned proportionately to the equivalent isotropic thermal parameters of their respective carbon or nitrogen atoms. Subsequently, the isotropic thermal parameters for the C-H hydrogen atoms were constrained to have identical shifts during refinement, as were those of the N-H hydrogen atoms. Extinction parameters26 were included in the final cycles of full-matrix leastsquares refinement of 1, 3-5, and 7. Selected bond lengths and angles for 1-4, 5, 6, 7, 8, and 9 are found in Tables 3, 4, 5, 6, 7, and 8, respectively. The programs used for all absorption corrections, data reduction, and processing of 1, and 5-9 were from the NRCVAX Crystal Structure System.27 All structures were refined using CRYSTALS.28 Complex scattering factors for neutral atoms were used in the calculation of structure factors.

Results Synthesis and Characterization of 1-9. The reaction of an aqueous/methanolic solution of [ML2]Cl2 (M ) Mn(II), Ni(II); L ) 1,10-phenanthroline, 2,2′-bipyridine) with 1 equiv of Hg(CN)2 yielded single crystals 1-4 with the general formula [ML2][Hg(CN)2Cl2]. The reaction of an aqueous solution of Cu(terpy)Cl2 (terpy ) 2,2′:6′,2′′-terpyridine), with an aqueous solution containing 1 equiv of Hg(CN)2 yielded single crystals of 5 with the “double-salt” formula [Cu(terpy)Cl2(µ-Hg(CN)2)]. A similar reaction with a methanolic solution of Cu(dien)Cl2 (dien ) diethylenetriamine) and a methanolic solution containing 1 equiv of Hg(CN)2 yielded single crystals of 7 with the double salt formula [Cu(dien)Cl][Hg(CN)2Cl]. The reaction of an aqueous

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Table 1. Summary of Crystallographic Data for 1a, and 2-4b empirical formula FW (g mol-1) temperature (K) crystal system space group a (Å) b (Å) c (Å) R (°) β (°) γ (°) Z U (Å3) Dcalc (g cm-3) 2θ limits (°) reflns collected independent reflns reflections observed [I ) 2.5σ(I)] goodness-of-fit on F R1, Rw [I ) 2.5σ(I)]e

1

2

3

4

C22H16N6Cl2HgMn 690.84 293 monoclinic I2/c 16.071(2) 9.015(1) 16.252(2) 90 90.127(8) 90 4 2354.6 1.949 4-54 2973 2765 2167

C24H16N6Cl2HgMn 738.88 293 monoclinic P2/n 15.998(5) 8.853(3) 18.797(8) 90 107.42(3) 90 4 2540.1 1.932 6-137 15828 4721 2713c

C22H16N6Cl2HgNi 694.59 293 monoclinic C2/c 22.521(15) 8.887(7) 16.147(12) 90 135.47(4) 90 4 2266.1 2.036 11-137 7756 2110 1489d

C26H16N6Cl2HgNi 742.63 293 monoclinic P2/n 8.088(2) 8.742(2) 17.763(6) 90 97.08(2) 90 2 1246.3 1.979 10-137 8606 2303 1795d

1.077 0.020, 0.025

1.441 0.064c, 0.064c

1.347 0.047d, 0.060d

1.000 0.037d, 0.045d

a Enraf-Nonius CAD-4 diffractometer, Mo KR radiation (λ ) 0.71069 Å), graphite monochromator. b Rigaku RAXIS-Rapid curved image plate area detector, Cu KR radiation (λ ) 1.54180 Å), graphite monochromator. c Reflections observed [I ) 2.0σ(I)]. d Reflections observed [I ) 2.2σ(I)]. e Function minimized Σw(|Fo| - |Fc|)2 where w-1 ) σ2(Fo) + 0.0002 Fo2, R1 ) Σ||Fo| - |Fc||/Σ|Fo|, Rw ) (Σw(|Fo| - |Fc|2)/ Σw|Fo|2)1/2.

solution of 2 equiv of [Cu(phen)2]Cl2 with 3 equiv of Hg(CN)2 yielded 6 with a resulting formula {[Cu(phen)2Cl]2Hg(CN)2[Hg(CN)2Cl]2}, which is similar to those of 5 and 7. The reaction of an aqueous solution of 1 equiv of CuCl2 with 1 equiv of tris(2-aminoethyl)amine (tren) and 2 equiv of Hg(CN)2 yielded 8 with a resulting formula of [Cu(tren)Hg(CN)2Cl][HgX2Cl] (X ) site of mixed Cl, CN occupancy). A similar reaction of an aqueous solution of 4 equiv of [Ni(tren)]Cl2 with 8 equiv of Hg(CN)2 and 1 equiv of HgCl2 yielded single crystals of 9 with a resulting formula of {[Ni(tren)]4[Hg(CN)2]8Cl6}HgCl4. Migration of the labile chloride ligands from the harder Cu(II) and Ni(II) centers to the coordinately unsaturated, softer Hg(II) centers drives the formation of 6-9.29,30 This halide migration to the Lewis-acidic Hg(CN)2 generates nonlinear Hg(II) products with coordination numbers greater than two, potentially increasing the structural and magnetic dimensionality in the process.13 The IR spectra of 3 and 6-9 clearly show the presence of the CN groups. Their νCN bands range from 2150 cm-1 (3) to 2215 cm-1 (9), and are consistent with either terminal cyanide groups on nonlinear Hg(II) units with coordination numbers greater than two such as in K[Hg(CN)2Cl] anions (νCN ) 2170 cm-1),31 or with strongly N-bound bridging cyanide groups such as in {Cu(tmeda)[Hg(CN)2]2}HgCl4 (νCN ) 2247 cm-1).14 These bands are shifted from the 2194 cm-1 absorbance of Hg(CN)2.32,33 Compounds 1, 2, 4, and 5 show also show IR peaks between 2180 and 2147 cm-1, but they are too weak to assign with certainty. The solid-state structures of complexes 1-9 are described below. Structures of [ML2(µ-Cl)2Hg(CN)2] (M ) Mn(II), Ni(II); L ) bipy, phen) (1-4). The X-ray single-crystal structures of [ML2(µ-Cl)2Hg(CN)2] (M ) Mn(II), Ni(II); L ) bipy, phen) reveal simple molecular complexes in which the coordinately unsaturated Hg(CN)2 unit is bound to the chloride ligands, which act as M-Hg bridging groups (Figure 1). The Mn(II) and Ni(II) centers in 1-4 have a distorted, octahedral geometry,

Figure 1. Molecular structure of [Ni(phen)2(µ-Cl)2Hg(CN)2] (4); the hydrogen atoms have been omitted for clarity (ORTEP, 50% ellipsoids).

with the two amine ligands (bipy or phen) cis-oriented and two chloride ligands completing the coordination sphere. These molecular complexes are analogous to the nickel organoamine-halocadmates [Ni(phen)2Cl2CdI2], [Ni(phen)2X2CdX2] (X ) site of mixed Br, Cl occupancy) and [Ni(bipy)2Cl2CdCl2]2.34 The bond distances and angles for 1-4 are gathered in Table 3. The M-N bond lengths range from 2.057(9) Å (3) to 2.295(11) Å (2), while the M-Cl bond lengths range from 2.4473(18) Å (4) to 2.505(4) Å (2). These values are comparable to those reported for Ni(bipy)2Cl2‚CH3OH (Ni-N ) 2.073(3), 2.077(3), 2.084(3), 2.100(4) Å; Ni-Cl ) 2.3940(13), 2.4213(13) Å),35 Mn(phen)2Cl2 (Mn-N ) 2.073(3), 2.077(3), 2.084(3), 2.100(4) Å; Mn-Cl ) 2.3940(13), 2.4213(13) Å),36 and Mn(bipy)2Cl2 (Mn-N ) 2.281(4), 2.299(4), 2.341(4), 2.371(4) Å; Mn-Cl ) 2.4396(14), 2.4544(13) Å).37 The chloride ligands bridge to the Hg(CN)2 metal centers via Hg-Cl bonds that range in length from 2.771(3) Å (3) to 2.829(4) Å (2) and can be compared to the Hg-Cl bonds lengths of 2.728(6), 2.884(6), and 3.029(7) Å found in the molecular [Cu(bipy)2Hg2Cl6]2 dimer and the 2.710(1) and 2.820(1) Å

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Crystal Growth & Design, Vol. 4, No. 3, 2004 625

Table 2. Summary of Crystallographic Data for 5-9a empirical formula FW (g mol-1) temperature (K) crystal system space group a (Å) b (Å) c (Å) R (°) β (°) γ (°) Z U (Å3) Dcalc (g cm-3) 2θ limits (°) reflns collected independent reflns reflections observed [I ) 2.5σ(I)] goodness-of-fit on F R1, Rw [I ) 2.5σ(I)]b

5

6

7

8

9

C17H15N5Cl2CuHg 624.38 293 triclinic P1 h 7.3434(9) 9.510(1) 13.3533(17) 85.57(1) 82.47(1) 87.594(8) 2 921.2 2.236 4-51 3637 3455 3054

C54H32N14Cl4Cu2Hg3 1747.6 293 triclinic P1 h 10.339(2) 10.911(2) 12.723(3) 69.811(17) 77.55(2) 82.228(18) 1 1312.5 2.211 4-56 6826 6379 4054

C6H13N5Cl2CuHg 490.24 293 monoclinic A2/a 15.7274(18) 8.6102(8) 19.2642(17) 90 97.735(8) 90 8 2484.9 2.519 4-52 2601 2551 1703

C9H18N7Cl3CuHg2 795.37 293 monoclinic P21/a 7.837(2) 17.148(2) 14.423(2) 90 95.67(2) 90 4 1928.8 2.739 4-55 5075 4463 2461

C40H72N32Cl10Hg9Ni4 3395.83 293 tetragonal P4 h 21c 22.358(3) 22.358(3) 8.1101(13) 90 90 90 2 4054.1 2.821 4-50 3204 2160 1454

1.319 0.017, 0.022

1.448 0.031, 0.034

1.232 0.022, 0.027

1.433 0.035, 0.033

1.263 0.031, 0.030

a Enraf-Nonius CAD-4 diffractometer, Mo KR radiation (λ ) 0.71069 Å), graphite monochromator. b Function minimized Σw(|F | o |Fc|)2 where w-1 ) σ2(Fo) + 0.0002Fo2, R1 ) Σ||Fo| - |Fc||/Σ|Fo|, Rw ) (Σw(|Fo| - |Fc|2)/Σw|Fo|2)1/2.

Table 3. Selected Bond Lengths (Å) and Angles (°) for the [M(L)2][(µ-Cl)2Hg(CN)2] Complexes 1-4 M, L M(1)-N(2) M(1)-N(3) M(1)-Cl(1) Hg(1)-Cl(1) Hg(1)-C(1)

1a Mn, bipy

2 Mn, phen

Bond Lengths 2.280(3) 2.272(12), 2.250(11) 2.238(3) 2.240(11), 2.295(11) 2.4951(9) 2.481(4), 2.505(4) 2.8199(9) 2.813(4), 2.829(4) 2.036(4) 2.061(19), 2.070(19)

Bond Angles Cl(1)-Hg(1)-Cl(1*) 80.70(3) 81.50(11) Cl(1)-Hg(1)-C(1) 92.01(12) 92.1(5), 90.9(5) Cl(1*)-Hg(1)-C(1) 99.81(13) 102.0(5), 99.5(5) C(1)-Hg(1)-C(1*) 164.5(2) 163.8(6) Cl(1)-M(1)-Cl(1*) 94.06(4) 95.22(13) Cl(1)-M(1)-N(2) 169.48(7) 170.3(3), 168.4(3) Cl(1*)-M(1)-N(2) 89.79(3) 89.9(2), 90.0(3) N(2)-M(1)-N(2*) 88.14(6) 86.5(4) Cl(1)-M(1)-N(3) 97.50(8) 97.6(3), 95.9(3) Cl(1*)-M(1)-N(3) 95.12(8) 91.5(5), 97.2(3) N(3)-M(1)-N(3*) 161.44(15) 162.7(4) N(2)-M(1)-N(3) 72.4(1) 73.9(4), 73.1(4) N(2)-M(1)-N(3*) 94.1(1) 90.4(4), 98.1(4) Hg(1)-Cl(1)-M(1) 92.62(3) 91.91(13), 91.04(13)

3b Ni, bipy

4c Ni, phen

2.056(9)

2.109(6)

2.066(8)

2.078(5)

2.451(3)

2.4473(18)

2.771(3)

2.7744(17)

2.045(14) 2.034(9)

78.76(11) 79.90(7) 94.5(4) 94.2(2) 99.2(4)

100.9(2)

162.2(7) 160.6(3) 91.66(15) 93.44(7) 174.3(3) 174.37(15) 88.7(3)

88.29(16)

91.5(5) 95.4(3)

90.5(3) 94.97(16)

89.9(3)

90.11(16)

172.4(5) 78.9(4)

172.6(3) 79.7(2)

95.7(4)

95.1(2)

94.79(9)

93.33(6)

a Symmetry transformations: (*) -x + 1, y, -z + 1/ . b Symme2 try transformations: (*) -x + 1, y, -z + 3/2. c Symmetry transformations: (*) -x + 1/2, y, -z + 3/2.

found in the chloride-bridged [Cu(bipy)2(µ-Cl)2Hg(CN)2], a Cu(II) isostructural analogue to 1 and 3 previously reported.15 This results in an effective seesaw coordination sphere based upon linear characteristic coordination for the Hg(II) center with C-Hg-C angles ranging from 160.6(3)° (4) to 164.8(1)° (1) and Cl-Hg-Cl angles ranging from 78.76(11)° (3) to 81.50(11)° (2), which can be compared to the C-Hg-C ) 160.1(8)° and Cl-Hg-

Figure 2. Short segment of [Cu(terpy)Cl2(µ-Hg(CN)2)]n (5), a 1-D chain as viewed along the a-axis; the hydrogen atoms have been omitted for clarity (ORTEP, 50% ellipsoids).

Cl ) 86.99(11)° of [nBu4N][Hg(CN)2Cl]‚0.5H2O.38 This effective seesaw coordination of Hg(II) is also observed in bis(triphen-ylarsine oxide)mercuric chloride,39 mercuric oxycyanide,40 and mercuric dithizonate.41 The M-Hg distances range from 3.805 Å (4) to 3.850 Å (3), but there are no significant intermolecular interactions. In all four cases, there is extended π‚‚‚π stacking of the conjugated ring systems characterized by interplanar distances of 3.4-3.6 Å that are slightly larger than the 3.3-3.5 Å range found for Mn(phen)2Cl2.36,42,43 Importantly, the addition of Hg(CN)2 to ML2Cl2 (M ) Mn(II), Ni(II); L ) bipy, phen) does not induce chloride migration, and no increase in structural dimensionality is observed. The rational synthesis of [Cu(phen)2(µ-Cl)2Hg(CN)2] was attempted, but only complex 6 could be isolated. Structure of [Cu(terpy)Cl2(µ-Hg(CN)2)] (5). The X-ray single-crystal structure of [Cu(terpy)Cl2(µ-Hg(CN)2)] (5) reveals a one-dimensional chain motif of [Cu(terpy)Cl2(µ-Hg(CN)2)]n that runs parallel to the a-axis (Figure 2). Rather than forming two chloride bridges to a single Hg(II) center, the Cu(terpy)Cl2 unit forms two chloride bridges to different Hg(II) centers. The bond distances and angles for 5 are gathered in Table 4.

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Table 4. Selected Bond Lengths (Å) and Angles (°) for [Cu(terpy)Cl2(µ-Hg(CN)2)] (5)a Hg(1)-C(1) Hg(1)-Cl(1*) Cu(1)-Cl(1) Cu(1)-N(3) Cu(1)-N(5) C(1)-Hg(1)-C(2) Cl(1*)-Hg(1)-Cl(2) Cl(1*)-Hg(1)-C(1) Cl(2)-Hg(1)-C(1) Cl(1*)-Hg(1)-C(2) Cl(2)-Hg(1)-C(2) Hg(1)-C(1)-N(1) Hg(1)-C(2)-N(2) N(3)-Cu(1)-N(5) Hg(1′)-Cl(1)-Cu(1)

Bond Lengths 2.046(4) Hg(2)-C(2) 2.9121(9) Hg(1)-Cl(2) 2.2673(9) Cu(1)-Cl(2) 2.029(3) Cu(1)-N(4) 2.021(3)

2.043(4) 2.8080(9) 2.516(1) 1.943(3)

Bond Angles 165.16(15) Cl(1)-Cu(1)-Cl(2) 100.25(3) Cl(1)-Cu(1)-N(3) 92.68(11) Cl(2)-Cu(1)-C(3) 92.18(11) Cl(1)-Cu(1)-N(4) 94.20(12) Cl(2)-Cu(1)-N(4) 155.30(9) N(3)-Cu(1)-N(4) 178.7(4) Cl(1)-Cu(1)-N(5) 178.7(4) Cl(2)-Cu(1)-N(5) 158.07(11) N(4)-Cu(1)-N(5) 100.58(3) Hg(1)-Cl(2)-Cu(1)

100.55(4) 98.28(8) 95.18(8) 155.30(9) 104.15(9) 79.45(11) 97.79(9) 96.44(9) 79.70(11) 105.78(3)

a Symmetry transformations: (*) -x - 1, -y, -z; (′) -x + 2, -y, -z.

The Hg-Cl bond lengths of 2.8080(9) and 2.9121(9) Å are well within the sum of the Hg/Cl van der Waals radii of 3.30 Å44,45 and are shorter than most bridging Hg-Cl bond lengths, such as those found in {Cu(tmeda)[Hg(CN)2]2}HgCl4 (3.051(2) and 3.217(2) Å),14 [Cu(en)2][Hg(CN)2Cl]2 (2.7089(17), 3.0978(15), and 3.2186(15) Å),38 and {[Cu(bipy)(OH)(Cl)]2Hg(CN)2}‚2H2O (2.980(1) Å).15 The Cu(II) center in 5 has a square pyramidal geometry comprised of three nitrogen donors from the terpy ligand and one chloride ligand (Cu(1)-Cl(1) ) 2.2673(9) Å) forming the base, while the second chloride ligand resides in the apical position (Cu(1)-Cl(2) ) 2.516(1) Å). This square pyramidal Cu(II) coordination sphere is also found for Cu(terpy)Cl2‚H2O (Cu-Cleq ) 2.231(2) Å, Cu-Clax ) 2.565(2) Å)46 and is similar to that found for {[Cu(bipy)Hg(CN)2Cl2]2Hg(CN)2} (CuCleq ) 2.3090(16) Å, Cu-Clax ) 2.5560(17)), a 1-D Cu2Hg2 rectangular cluster,15 and [Cu(terpy)CN]NO3‚H2O (Cu-Ceq ) 1.92(2) Å, Cu-NCax ) 2.21(1) Å), a 1-D [Cu(terpy)CN]+ chain.47 The Hg(II) center has an effective seesaw coordination based on linear characteristic coordination where there are two shorter and two longer Hg(II) bonds ((2+2) according to the convention devised by Grdenic),45 with C(1)-Hg(1)-C(2) ) 165.16(15)° and Cl(1*)-Hg(1)-Cl(2) ) 100.25(3)°, similar to the Hg(II) centers in 1-4. The Cu(1)-Hg(1) and Cu(1)-Hg(1′) distances are 4.006 and 4.250 Å, respectively. Although the addition of Hg(CN)2 to Cu(terpy)Cl2 does not induce chloride migration from the hard Cu(II) center to the softer Hg(II) center, the structural dimensionality has increased in the process. Structure of {[Cu(phen)2Cl]2Hg(CN)2[Hg(CN)2Cl]2} (6). Unlike the molecular complexes 2 and 4, reaction of an aqueous solution containing 1 equiv of [Cu(phen)2]Cl2 with 1 equiv of Hg(CN)2 results in the formation of single crystals of {[Cu(phen)2Cl]2Hg(CN)2[Hg(CN)2Cl]2} (6) (Figure 3). The Cu(II) center of the [Cu(phen)2Cl]+ cation is five coordinate with a distorted geometry as exemplified by its tau parameter of τ ) 0.72 (where the τ range from 0 to 1 represents the geometric distortions from a perfect square pyramid to a trigonal bipyramid, respectively).48 The bond distances and angles for 6 are gathered in Table 5. This Cu(II) coordination sphere and the Cu(1)-Cl(2) bond length of 2.3340(17) Å is very similar to that found

Figure 3. Three moieties that constitute {[Cu(phen)2Cl]2Hg(CN)2[Hg(CN)2Cl]2} (6); one [Cu(phen)2Cl]+ cation and the hydrogen atoms have been omitted for clarity (ORTEP, 50% ellipsoids). Table 5. Selected Bond Lengths (Å) and Angles (°) for {[Cu(phen)2Cl]2[Hg(CN)2Hg(CN)2Cl]2 }(6)a Hg(1)-Cl(1) Hg(1)-C(1) Hg(2)-Cl(2) Hg(2)-N(2′) Hg(2)-C(3) Cu(1)-N(4) Cu(1)-N(6)

Bond lengths 2.7217(15) Hg(1)-Cl(1*) 2.077(7) Hg(1)-C(2) 3.2800(16) Hg(2)-Cl(2*a) 3.010(5) Hg(2)-N(2*b) 2.034(7) Cu(1)-Cl(2) 2.105(5) Cu(1)-N(5) 2.100(5) Cu(1)-N(7)

Cl(1)-Hg(1)-Cl(1*) Cl(1*)-Hg(1)-C(1) Cl(1*)-Hg(1)-C(2) Cl(2)-Hg(2)-Cl(2*a) Cl(2*a)-Hg(2)-N(2′) Cl(2*a)-Hg(2)N(2*b) Cl(2)-Hg(2)-C(3) N(2′)-Hg(2)-C(3) C(3)-Hg(1)-C(3*a) N(4)-Cu(1)-N(5) N(5)-Cu(1)-N(6) N(4)-Cu(1)-N(7) N(6)-Cu(1)-N(7) Hg(2)-Cl(2)-Cu(1)

Bond Angles 91.98(4) Cl(1)-Hg(1)-C(1) 93.7(2) Cl(1)-Hg(1)-C(2) 104.16(18) C(1)-Hg(1)-C(2) 180 Cl(2)-Hg(2)-N(2′) 85.49(12) Cl(2)-Hg(2)-N(2*b) 94.51(12) N(2′)-Hg(2)-N(2*b) 94.2(2) 91.0(2) 180 80.92(19) 94.17(19) 93.74(19) 81.14(19) 143.87(7)

Cl(2*a)-Hg(2)-C(3) N(2*b)-Hg(2)-C(3) Cl(2)-Cu(1)-N(4) N(4)-Cu(1)-N(6) Cl(2)-Cu(1)-N(7) N(5)-Cu(1)-N(7) Hg(1)-Cl(1)-Hg(1*)

2.7831(17) 2.061(7) 3.2800(16) 3.010(5) 2.3340(17) 1.998(4) 1.994(4) 97.74(18) 101.74(17) 152.9(3) 94.51(12) 85.49(12) 180 85.8(2) 89.0(2) 128.75(14) 105.00(18) 93.98(15) 171.8(2) 88.02(4)

a Symmetry transformations: (*) -x, -y + 1, -z + 1; (*a) -x + 1, -y + 1, -z + 2; (*b) -x + 1, -y + 1, -z + 1; (′) x, y, z + 1.

in the molecular complex [Cu(bipy)2Hg2Cl6]2 (τ ) 0.47, Cu-Cl ) 2.320(7) Å).15 One chloride ligand has migrated to generate an [Hg(CN)2Cl]- anion which in turn dimerizes via Hg-Cl bridges to form a [Hg(CN)2Cl]22double salt moiety as has been found in [PPN][Hg(CN)2Cl]‚H2O,[nBu4N][Hg(CN)2Cl]‚0.5H2O,and[Ni(terpy)2][Hg(CN)2Cl]2.38 This [Hg(CN)2Cl]22- unit is analogous to the Hg2Cl62- bitetrahedron reported for the molecular complex [Cu(en)2][Hg2Cl6].49 The additional, neutral Hg(CN)2 unit serves two functions: (1) to act as bridging units between the [Hg(CN)2Cl]22- anions via N-cyano interactions from the anion to the neutral Hg(CN)2 metal center (N(2′)-Hg(2) ) 3.010(5) Å), and (2) to act as bridging units for the [Cu(phen)2Cl]+ cations via chloride bridges (Cl(2)-Hg(2) ) 3.2800(16) Å). The net result is the formation of a 1-D anionic chain of {[Hg(CN)2Cl]2Hg(CN)2}n2n- with associated [Cu(phen)2Cl]+ units that dangle along its length (Figure 4). This Hg(CN)2 bridging mode is related to those reported for the 1-D complexes {[Cu(bipy)Hg(CN)2Cl2]2Hg(CN)2}15 and {[Cu(bipy)(OH)(Cl)]2Hg(CN)2}‚2H2O,15 and similar to an example where HgCl2 bridges Cu4 clusters.29

Mercury Cyanide-Based Coordination Polymers

Crystal Growth & Design, Vol. 4, No. 3, 2004 627 Table 6. Selected Bond Lengths (Å) and Angles (°) for [Cu(dien)Cl][Hg(CN)2Cl] (7)a Hg(1)-Cl(1) Hg(1)-Cl(2) Hg(1)-C(11) Cu(1)-Cl(1) Cu(1)-N(1) Cu(1)-N(7)

Figure 4. A segment of the 1-D chain {[Cu(phen)2Cl]2Hg(CN)2[Hg(CN)2Cl]2} (6) as viewed along the c-axis; the hydrogen atoms have been omitted for clarity (ORTEP, 50% ellipsoids).

Bond Lengths 3.2143(15) Hg(1)-Cl(1*) 2.9219(16) Hg(1)-Cl(2′) 2.066(8) Hg(1)-C(12) 2.2875(16) Cu(1)-Cl(1*a) 2.014(5) Cu(1)-N(4) 2.017(5)

Cl(1)-Hg(1)-Cl(1*) Cl(1*)-Hg(1)-Cl(2) Cl(1*)-Hg(1)-Cl(2′) Cl(1)-Hg(1)-C(11) Cl(2)-Hg(1)-C(11) Cl(1)-Hg(1)-C(12) Cl(2)-Hg(1)-C(12) C(11)-Hg(1)-C(12) Cl(1)-Cu(1)-N(1) Cl(1)-Cu(1)-N(4) Cl(1)-Cu(1)-N(7) N(1)-Cu(1)-N(4) N(4)-Cu(1)-N(7) Hg(1)-Cl(1)-Cu(1) Hg(1)-Cl(1)-Cu(1*a) Cu(1)-Cl(1)-Cu(1*a)

3.2483(16) 2.9345(16) 2.055(7) 2.7608(17) 2.001(5)

Bond Angles 103.17(4) Cl(1)-Hg(1)-Cl(2) 175.19(4) Cl(1)-Hg(1)-Cl(2′) 79.37(4) Cl(2)-Hg(1)-Cl(2′) 83.0(2) Cl(1*)-Hg(1)-C(11) 92.6(2) Cl(2′)-Hg(1)-C(11) 91.9(2) Cl(1*)-Hg(1)-C(12) 92.8(2) Cl(2′)-Hg(1)-C(12) 171.9(3) Cl(1)-Cu(1)-Cl(1*a) 96.82(16) Cl(1*a)-Cu(1)-N(1) 167.45(17) Cl(1*a)-Cu(1)-N(4) 95.53(15) Cl(1*a)-Cu(1)-N(7) 84.9(2) N(1)-Cu(1)-N(7) 84.4(2) Hg(1)-Cl(1)-Hg(1*) 108.04(6) Hg(1*)-Cl(1)-Cu(1) 136.39(6) Hg(1*)-Cl(1)-Cu(1*a) 88.13(6) Hg(1)-Cl(2)-Hg(1′)

79.94(4) 174.68(4) 97.835(12) 91.4(2) 92.3(2) 83.5(2) 93.0(2) 91.87(6) 87.08(16) 100.65(16) 86.62(17) 166.3(2) 76.83(4) 108.04(6) 137.11(5) 160.82(7)

a Symmetry transformations: (*) -x, -y - 1/ , -z + 1/ ; (*a) 2 2 -x, -y +1/2, -z + 1/2; (′) -x - 1/2, y - 1/2, -z + 1/2.

Figure 5. A segment of the [Hg(CN)2Cl]nn- 1-D chain of (7) (ORTEP, 50% ellipsoids).

The Hg(2) center has an effective octahedral coordination (2+2+2) based on linear characteristic coordination as a result (N(2′)-Hg(2)-N(2*b) ) Cl(2)-Hg(2)-Cl(2*a) ) C(3)-Hg(2)-C(3*a) ) 180°). The Hg‚‚‚ NC interaction is longer than the N‚‚‚Hg interaction of 2.74 Å responsible for the solid-state aggregation of Hg(CN)233 and can be compared with the related [Cu(dien)][Au(CN)4]2 and [Cu(dmeda)2Au(CN)4][Au(CN)4] (-AuCNAu ) 3.002(14) and 2.963(13) Å, respectively) gold(III) complexes50 and [Cu(en)2][Ag2(CN)3][Ag(CN)2] (-AgCNAg ) 2.572(3) Å) silver(I) complex.10 Thus, the addition of Hg(CN)2 to Cu(phen)2Cl2 induces the migration of one chloride ligand from the harder Cu(II) to the softer Hg(II) center, increasing the structural dimensionality from 0 to 1 in complex 6. Extended π‚‚‚π stacking of the conjugated ring systems characterized by interplanar distances of 3.7-4.4 Å further increases the dimensionality from 1 to 2. Structure of [Cu(dien)Cl][Hg(CN)2Cl] (7). The slow evaporation of a solution containing Hg(CN)2 and 1 equiv of Cu(dien)Cl2 yielded single crystals of [Cu(dien)Cl][Hg(CN)2Cl] (7). Migration of one chloride ligand occurs from the Cu(II) center to a Hg(CN)2 unit to form a [Hg(CN)2Cl]- double salt moiety. In contrast to the self-assembled [Hg(CN)2Cl2]2- dimers observed in 6, a 1-D chain of [Hg(CN)2Cl]nn- is formed with Hg(1)-Cl(2) bond lengths of 2.9219(16) and 2.9345(16) Å (Figure 5). The bond distances and angles for 7 are gathered in Table 6. This 1-D anionic chain motif is similar to the [Hg3Cl9]n3n- chains reported for [Co(NH3)6][Hg3Cl9]‚

Figure 6. Dimeric [Cu2(dien)2(µ-Cl)2]2+ cation of (7); hydrogen atoms have been removed for clarity (ORTEP, 50% ellipsoids).

H2O.51 As in 5 and 6, the second chloride ligand remains bound to the Cu(II) center, but in 7 the cations dimerize via two chloride bridges to form [Cu2(dien)2(µ-Cl)2]2+ (Figure 6). Each Cu(II) center has a distorted square pyramidal geometry where the three N atoms of the dien ligand and one chloride ligand (Cl1) form the basal plane, while the second chloride Cl(1*a) occupies the apical position. The three Cu-N distances are very similar (2.014(5), 2.015(5), 2.001(5) Å), while the Cu-Cl apical bond is much longer than the basal one (2.7608(17) versus 2.2875(17) Å). The copper centers in the dimer are separated from each other by 3.528 Å and the Cu-ClCu and Cl-Cu-Cl angles are 88.13(6)° and 91.87(6)°, respectively. This can be compared with the Cu-ClCu bond angle of [Cu2(dien)2Cl2][NO3]2 (90.62(1)°),52 and the related [(terpy)CuCl]2[PF6]2 (89.9(1)°).53 The chlorine atoms of the [Cu2(dien)2(µ-Cl)2]2+ cations form two additional bridges to the open coordination site on the Hg(II) centers (Cl(1)-Hg(1) ) 3.2143(15) Å, Cl(1*)-Hg(1) ) 3.2483(16) Å) of the anionic 1-D [Hg(CN)2Cl]nnchains resulting in a 2-D brick-wall layer motif (Figure 7). Each Hg(II) center has an effective octahedral coordination (2+4) based on linear characteristic coordination with bridging chlorine atoms all in the equatorial plane and the cyano ligands perpendicular to the layer.

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Draper et al. Table 7. Selected Bond Lengths (Å) and Angles (°) for [Cu(tren)Hg(CN)2Cl][HgX2Cl] (8)a Hg(1)-Cl(1) Hg(1)-C(11) Hg(2)-Cl(2) Hg(2)-C(10) Hg(2)-Cl(3) Cu(1)-N(1) Cu(1)-N(3)

Figure 7. 2-D layer structure of [Cu(dien)Cl][Hg(CN)2Cl] (7); hydrogen atoms have been omitted for clarity (ORTEP, 50% ellipsoids).

Cl(1)-Hg(1)-Cl(1*) Cl(1*)-Hg(1)-C(11) Cl(1*)-Hg(1)-C(12) Cl(2)-Hg(2)-Cl(2*a) Cl(2*a)-Hg(2)-Cl(3) Cl(2*a)-Hg(2)-Cl(4) N(1)-Cu(1)-N(2) N(2)-Cu(1)-N(3) N(2)-Cu(1)-N(4) N(1)-Cu(1)-N(12) N(3)-Cu(1)-N(12) Hg(1)-Cl(1)-Hg(1*a) C(10)-Hg(2)-C(20) a 1/

Figure 8. 1-D cationic chain of [Cu(tren)Hg(CN)2Cl]+ units observed in 8; hydrogen atoms have been omitted for clarity (ORTEP, 50% ellipsoids).

[NH3(C2H5)]2[Hg(CN)2Cl2],54

The layer is similar to a 2-D chess-board perovskite-like layered structure with Hg-Cl bond lengths of 2.901(2) and 3.432(2) Å. Weak N-H‚‚‚NC interactions (N(11)‚‚‚N(4) ) 3.057 Å) between the cyano groups of one 2D-layer and the amine protons from the layer above and below increase the structural dimensionality of 7 and are shorter than those reported for [Cu(en)2]3[W(CN)8]2‚H2O (3.214 Å,),18 and [Cu(en)2][Ag2(CN)4] (3.195 Å).21 Structure of [Cu(tren)Hg(CN)2Cl][HgX2Cl] (8). The reaction of Cu(tren)Cl2 with 2 equiv of Hg(CN)2 not only induces complete migration of the chloride ligands from the Cu(II) center to the coordinately unsaturated Hg(II) centers, but in the process opens a site for N-cyano binding between the [Hg(CN)2Cl]- double salt unit formed and the [Cu(tren)]2+ cation. These units then assemble into a 1-D cationic chain with the formula [Cu(tren)Hg(CN)2Cl]nn+ via Hg-Cl bridges (Hg(1)-Cl(1) ) 2.795(4) Å, Hg(1)-Cl(1*) ) 2.772(3) Å (Figure 8). The bond distances and angles for 8 are gathered in Table 7. The cationic Cu(II) center in 8 has a distorted fivecoordinate geometry (τ ) 0.65), with one tren and one strongly N-bound Hg(CN)2 completing the coordination sphere (Cu-N-cyano ) 1.966(11) Å). This coordination sphere is very similar to the five-coordinate Cu(II) center reported for the molecular complex [Cu(tren)Au(CN)2][Au(CN)2] (τ ) 0.74; Cu-N-cyano ) 1.950(9) Å).11 Simultaneous chloride migration from harder Cu(II) to softer Hg(II) and cyano bridging from Hg(CN)2 units to an octahedral Cu(II) center has been observed in {Cu-

Bond Lengths 2.757(3) Hg(1)-Cl(1*) 2.028(12) Hg(1)-C(12) 2.658(3) Hg(2)-Cl(2*a) 2.050(5) Hg(2)-C(20) 2.364(7) Hg(2)-Cl(4) 2.051(13) Cu(1)-N(2) 2.135(12) Cu(1)-N(4)

2,

Bond Angles 90.19(7) Cl(1)-Hg(1)-C(11) 98.2(3) Cl(1)-Hg(1)-C(12) 93.1(3) C(11)-Hg(1)-C(12) 92.85(7) Cl(2)-Hg(2)-Cl(3) 100.2(3) Cl(2)-Hg(2)-Cl(4) 96.4(11) Cl(3)-Hg(2)-Cl(4) 84.1(5) N(1)-Cu(1)-N(3) 85.3(4) N(1)-Cu(1)-N(4) 84.9(5) N(3)-Cu(1)-N(4) 89.0(5) N(2)-Cu(1)-N(12) 100.2(5) N(4)-Cu(1)-N(12) 91.3(1) Hg(2)-Cl(2)-Hg(2*) 151.1(17)

2.776(2) 2.054(11) 2.761(3) 2.054(5) 2.306(6) 2.018(11) 2.053(12) 97.6(3) 92.9(3) 164.4(4) 101.7(2) 108.1(3) 145.0(4) 114.6(6) 133.6(6) 109.2(5) 172.5(5) 98.0(5) 104.72(13)

Symmetry transformations: (*) x - 1/2, -y + 1/2, z; (*a) x + -y + 1/2, z.

Figure 9. 1-D anionic chain of [HgX2Cl]- units observed in 8; X sites are of 1:1 mixed Cl/CN occupancy (ORTEP, 50% ellipsoids).

(tmeda)[Hg(CN)2]2}HgCl4 (Cu-Neq cyano ) 1.975(11) Å, Cu-Nax cyano ) 2.583(13) Å).14 The Hg(1) centers have an effective seesaw coordination (2+2) based on linear characteristic coordination (C-Hg-C ) 164.2(6)°, ClHg-Cl ) 90.1(1)°) as found for structures 1-5. A second 1-D chain is also formed but it is anionic, comprised of [HgX2Cl]- units, where X represents sites of 1:1 mixed Cl/CN occupancy (Hg(2)-Cl(2) ) 2.632(4) Å, Hg(2*)Cl(2) ) 2.754(4) Å) (Figure 9). The Hg(2) center shows an effective tetrahedral coordination (2+2) based on linear characteristic coordination (Cl(2*a)-Hg(2)-Cl(2) ) 83.0(2)°, X(3)-Hg(2)X(4) = 142.4°). Unlike structures 6 and 7, no additional Hg-Cl or Hg-N cyano bridging takes place to connect the cationic and anionic components of 8. Rather, weak N-H‚‚‚NC (N(4)-N(11) ) 3.106 Å, N(3)-N(11) ) 3.274 Å) and N-H‚‚‚Cl (N(1)-Cl(2) ) 3.521 Å, N(3)-X(4) = 3.695 Å) interactions bind the [HgX2Cl]nn- chain between the crescent-shaped cleft formed by the [Cu(tren)Hg(CN)2Cl]nn+ chain to generate a neutral [Cu(tren)Hg(CN)2Cl][HgX2Cl] (8) column. Additional N-H‚‚‚Cl interactions (N(4)-Cl(1) ) 3.437 Å) bind different columns together, forming the 2-D layer motif shown in Figure 10. These weak N-H‚‚‚Cl interactions are comparable to those N-Cl distances reported for [Cu(Hbimam)Cl3]2(H2O)2, [Cu(Hbimam)2Cl2]Cl2(H2O)2 (3.266 and 3.277 Å, respectively; bimam ) bis(imidazol-2-yl)-

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Crystal Growth & Design, Vol. 4, No. 3, 2004 629 Table 8. Selected Bond Lengths (Å) and Angles (°) for {[Ni(tren)]4[Hg(CN)2]8Cl6}HgCl4 (9) a Hg(1)-C(1) Hg(1)-Cl(1′) Hg(1)-Cl(1) Hg(2)-Cl(2) Hg(2)-C(4) Ni(1)-N(5) Ni(1)-N(7) Ni(1)-N(1)

Figure 10. Extended 2-D motif of [Cu(tren)Hg(CN)2Cl][HgX2Cl] (8); methylene hydrogen atoms have been omitted for clarity. Color scheme: Hg, pink; Cu, red; Cl, green; N, blue; C, gray; H, white.

methylaminomethane),55 trans-[PtCl2(NH3)2] (3.41 Å),56 and 2,6-diphenylpyridinium tetrachloroaurate (3.45 Å, 3.75 Å).57 Structure of {[Ni(tren)]4[Hg(CN)2]8Cl6}HgCl4 (9). Reaction of an aqueous solution containing 4 equiv of Ni(tren)Cl2 with 8 equiv of Hg(CN)2 and 1 equiv of HgCl2 results in the formation of single crystals of {[Ni(tren)]4[Hg(CN)2]8Cl6}HgCl4 (6). Complete migration of both chloride ligands from Ni(II) to Hg(II) drives the formation of the product similar to that found with complex 8 and the 2-D layer complex {Cu(tmeda)[Hg(CN)2]2}HgCl4.14 The IR spectrum clearly shows a blueshifted υCN (2215 cm-1) band relative to free Hg(CN)2, consistent with the formation of a bridging cyanide ligand. The crystal structure has an asymmetric unit consisting of a six-coordinate Ni(II) center with distorted octahedral geometry (one tren ligand, one bridging Hg(CN)2, and one bridging [Hg(CN)2Cl]-), an additional Cl atom and a [HgCl4]2- moiety (Ni-N(1)cyano ) 2.13(3) Å, Ni-N(3)cyano ) 2.06(3) Å). The bond distances and angles for 9 are gathered in Table 8. Similar cyano bridging to Ni(II) centers is reported for [Ni(tren)Au(CN)2][Au(CN)2] (Ni-N-cyano ) 2.12(1) Å, 2.05(2) Å),58 [Ni(tren)Ag(CN)2][Au(CN)2] (Ni-Ncyano ) 2.098(3) Å, 2.039(3) Å),10 and [Ni(tren)][N(CN)2]2 (Ni-N-cyano ) 2.108(3) Å, 2.064(3) Å).59 The Ni-N distances range from 2.03(3) to 2.11(3) Å for the Ni-N(tren), which are in the expected range for NiN(amine) bonds. The Ni(II)-bound [Hg(CN)2Cl]- moiety (Hg(2)-Cl(2) ) 2.754(9) Å) forms a second chloride bridge to a different Ni(II)-bound [Hg(CN)2Cl]- unit (Hg(2)-Cl(2*) )2.768(9) Å) that is inverted with respect to its Ni(II) center, resulting in an alternating chain of four coordinate, seesaw Hg(2) centers. A third chloride bridge to the Hg(CN)2 unit, N-bound to the same Ni(II) center (Hg(1)-Cl(2) ) 3.187(9) Å) is also formed. The Cl(1) atoms forms two chloride bridges between two different Hg(1) centers (Cl(1)-Hg(1) ) 2.825(9) Å, Cl(1)-Hg(1′a) ) 2.92(1) Å) of the same Hg(2) containing chain and another two chloride bridges between two different Hg(1) centers of a second Hg(2) containing chain resulting in a complex 1-D {[Ni(tren)]4[Hg(CN)2]8Cl6}2+ ribbon (Figure 12). The Hg(1) centers have an effective square pyramidal coordination (2+3) based on linear characteristic coordination with two chloride and two cyano ligands in trans positions making up the basal plane; a third Cl ligand is found in the apical position.

Bond Lengths 2.06(3) Hg(1)-C(2) 2.92(1) Hg(2)-C(3) 2.825(9) Hg(1)-Cl(2) 2.754(9) Hg(2)-Cl(2*) 2.09(3) Hg(3)-Cl(3) 2.10(3) Ni(1)-N(6) 2.03(3) Ni(1)-N(8) 2.13(3) Ni(1)-N(3)

C(1)-Hg(1)-C(2) Cl(1)-Hg(1)-Cl(2) Cl(1)-Hg(1)-Cl(1′) Cl(1)-Hg(1)-C(2) Cl(2)-Hg(2)-C(3) Cl(2)-Hg(2)-C(4) C(3)-Hg(2)-C(4) N(5)-Ni(1)-N(6) N(6)-Ni(1)-N(7) N(6)-Ni(1)-N(8) N(5)-Ni(1)-N(1) N(7)-Ni(1)-N(1) N(5)-Ni(1)-N(3) N(7)-Ni(1)-N(3) N(1)-Ni(1)-N(3) Hg(1)-Cl(1)-Hg(1′′) Hg(1′′)-Cl(1)-Hg(1′a) Hg(1′′)-Cl(1)-Hg(1*) a 1/

Bond Angles 174.0(15) Cl(1)-Hg(1)-C(1) 106.0(3) Cl(1′)-Hg(1)-Cl(2) 89.72(4) Cl(1′)-Hg(1)-C(1) 90.1(12) Cl(1′)-Hg(1)-C(2) 91.5(10) Cl(2*)-Hg(2)-C(3) 94.6(8) Cl(2*)-Hg(2)-C(4) 163.5(12) Cl(2)-Hg(2)-Cl(2*) 93.7(11) N(5)-Ni(1)-N(7) 94.4(13) N(5)-Ni(1)-N(8) 84.2(11) N(7)-Ni(1)-N(8) 87.4(11) N(6)-Ni(1)-N(1) 84.5(13) N(8)-Ni(1)-N(1) 95.0(12) N(6)-Ni(1)-N(3) 99.0(12) N(8)-Ni(1)-N(3) 83.7(11) Hg(2)-Cl(2)-Hg(2*a) 92.9(4) Hg(1)-Cl(1)-Hg(1′a) 91.33(4) Hg(1)-Cl(1)-Hg(1*) 166.25(4) Hg(1′a)-Cl(1)-Hg(1*)

2.04(4) 2.06(3) 3.187(9) 2.768(9) 2.48(1) 2.11(3) 2.01(3) 2.06(3) 95.0(11) 164.2(3) 98.5(11) 84.8(12) 94.1(10) 99.2(8) 104.6(3) 163.0(13) 82.0(12) 83.9(13) 178.8(11) 95.8(11) 96.4(11) 177.0(13) 101.9(3) 166.25(7) 91.33(4) 88.3(4)

Symmetry transformations as x, y, z: (*) y + 1/2, x - 1/2, z + + 1/2, x - 1/2, z - 1/2, (′) -y + 3/2, -x + 3/2, z - 1/2; (′a) -y + 3/2, z + 1/2; (′′) -x + 2, -y + 1, z.

2; (*a) y + 3/2, -x

Figure 11. Asymmetric unit of {[Ni(tren)]4[Hg(CN)2]8Cl6}HgCl4 (9); hydrogen atoms have been omitted for clarity (ORTEP, 50% ellipsoids).

Figure 12. 1-D cationic ribbon of {[Ni(tren)]4[Hg(CN)2]8Cl6}2+ (9); tren ligands have been omitted for clarity (ORTEP, 50% ellipsoids).

The double salt complex 9 crystallizes in the noncentrosymmetric, tetragonal space group P4 h 21c, suggesting that interesting optical properties such as birefringence may be accessed.14 The [HgCl4]2- moieties, which chargebalance the cationic ribbons, template the 3-D packing

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Figure 13. 3-D extended structure of {[Ni(tren)]4[Hg(CN)2]8Cl6}HgCl4 (9); tren ligands have been omitted for clarity. Color scheme: Hg, pink; Ni, red; Cl, green; N, blue; C, gray; H, white.

of the {[Ni(tren)]4[Hg(CN)2]8Cl6}2+ ribbons via the formation of weak N-H‚‚‚NC interactions (Cl(3)-N(amine) ) 3.500 Å, 3.569 Å, 3.590 Å) into a 3-D superstructure (Figure 13). Magnetic Properties. For most of the reported complexes, the paramagnetic transition metal centers are well separated in space with no viable magnetic coupling pathway. However 5, 6, and 7 all have structural features that might mediate magnetic interactions. Accordingly, the temperature (T) dependence of the molar magnetic susceptibility (χM) of polycrystalline samples of these three compounds were measured from 1.8 to 300 K. For 6, µeff ) 2.65 µB (per Cu(II) pair) at 300 K, and remains constant until 30 K, at which point it decreases, reaching 2.18 µB at 1.8 K. No maximum in χM vs T is observed. This behavior is consistent with weak antiferromagnetic (AF) exchange between S ) 1/2 Cu(II) centers. From the X-ray structure, the two Cu(II) centers are connected via a nearly linear Cl-Hg-Cl chain; each pair of such Cu(II) centers is magnetically (but not structurally) isolated from the next. Thus, 6 can be treated as a simple bimetallic Cu(II) species, and accordingly the magnetic data were fitted with the Bleaney-Bowers dimer model (using H ˆ ) -2JS1S2)60 to yield J ) -0.70 ( 0.01 cm-1 and g ) 2.16 ( 0.01. This interaction is quite weak on account of the long Hg-Cl bonds (3.2800(16) Å) that disrupt the exchange pathway. The magnetic behavior of 5 is very similar to 6. The µeff ) 1.92 µB at 300 K and is temperature-independent until 30 K, upon which it drops to 1.58 µB at 2 K. The pathway for the AF interactions in 5 is also a Cl-HgCl bridge, but in this case the Cu(II) centers form a 1-D chain (Figure 2); hence, the magnetic data were fitted using the theoretical expression for a 1-D Heisenberg AF chain of S ) 1/2 centers61 to give best-fit values of J ) -0.45 ( 0.01 cm-1 and g ) 2.22 ( 0.01. Unlike for 6, the Cl-Hg-Cl bridge in 5 is not linear but kinked, and the Cu(II) centers are connected in an equatorial/axial fashion. Despite this difference, the magnitude of the coupling interaction is similar and weak, but stronger than that found in {[Cu(bipy)Hg(CN)2Cl2]2Hg(CN)2}, which has a linear, axial/axial Cl-Hg-Cl bridge mediating Cu(II) magnetic exchange.15

Draper et al.

Figure 14. Temperature dependence of χM and µeff for 7; a maximum at 4 K is observable. The solid line is theory (see text).

As would be expected, 7, which contains a chlorobridged Cu(dien) dimer cation, shows the strongest magnetic interaction. At 300 K, µeff ) 2.57 µB (per dimer), and this remains unchanged until 4 K, at which point it drops, reaching 1.58 µB at 1.8 K. Importantly, there is a maximum in χM at 4.0 K (Figure 14), indicative of significant AF interactions.23 An examination of the structure shows that the [Cu(dien)(µ-Cl)]22+ dimers are connected in a 2-D array via Cl-Hg-Cl bridges similar to 5. Thus, the magnetic data was fitted using the Bleaney-Bowers equation with an additional magnetic field parameter (zJ′) to account for the weaker interdimer interactions and a paramagnetic impurity factor (P).23 This gave best fit values of J ) -1.16 ( 0.11 cm-1, g ) 2.08 ( 0.05, P ) 0.003, and zJ′ ) -0.14 ( 0.01 cm-1; the fit is shown as a solid line in Figure 14. The edge-sharing apical/basal coordination geometry of 7 is less common than edge-shared basal/basal systems.62 Other examples similar to 7 include [Cu(dien)(µ-Cl)]2(ClO4)263 and [Cu(terpy)(µ-Cl)]2(PF6)2,53 which show magnetic exchange interactions of J ) -5.9 and +0.4 cm-1, respectively. A magnetostructural correlation62 based on the Cu-Cl-Cu angle has been proposed, and it predicts an antiferromagnetic interaction of -11.5 cm-1; however, only three compounds were used to define the correlation. The J value in 7 is found to be significantly smaller than the Cu-Cl-Cu anglebased prediction due to the extreme asymmetry of the Cu-Cl bond lengths in 7 (2.7608(17) and 2.2875(17) Å); the related complexes used for the magnetostructural correlation have more symmetric copper-chloride cores than that found in 7. That said, theoretical calculations64 suggest that the coupling in these apical/basal systems should generally be weak and this is certainly reflected in the magnetic data for 7. Also, the weak interdimer interaction (zJ′) in 7 is consistent with the fact that it is mediated by long (>3.2 Å) Hg-Cl bonds, as is the case for the weak coupling in 6. Discussion In an effort to comprehend the type of bridging mode (chloride versus N-cyano) favored in the transition metal organoamine double salt mercurates, structures 1-9 can be examined by considering the effects of (a) the transition metal used, (b) the effective coordination

Mercury Cyanide-Based Coordination Polymers

sphere of the transition metal (i.e., capping ligand employed), and (c) the capping ligand basicity. None of the transition metal cations utilized here in this study are coordinately saturated, thus ensuring either chloride or N-cyano coordination to the transition metal center. When 2 equiv of bipy and phen are employed with Mn(II) or Ni(II) centers, blocking four of six possible coordination sites, only molecular complexes incorporating Hg(CN)2 units are obtained (1-4) after the addition of Hg(CN)2; migration of the chloride ligands does not occur, and there is no increase in structural dimensionality. However, changing the transition metal to Cu(II) causes partial migration of the chloride ligands (from Cu(II) to Hg(II)) to occur, resulting in the formation of new moieties (e.g., [Hg(CN)2Cl]22-) and an increase in structural dimensionality to a 1-D chain in the case of 6. The increased lability of Cu(II) vs the more inert Mn(II) or Ni(II) centers may enable this facile chloride migration to occur. Although chloride migration from Cu(II) does not occur upon substitution of bipy or phen for 1 equiv of terpy, an increase of dimensionality also occurs (complex 5). In this case, the plasticity of the Cu(II) center enables a facile change in coordination sphere of the Cu(II) from octahedral to distorted trigonal bipyramidal geometry also resulting in the formation of a 1-D chain. Typically, an increase in the number of available coordination sites at the transition metal site by changing the amine ligand should result in an increase in structural dimensionality. In this case, with the use of neutral Hg(CN)2, it is difficult to ascertain the impact of different denticity amines because the chloride atoms can act as ligands themselves; there is not a clear correlation of capping amine denticity and structural dimensionality. On the other hand, the basicity of the amine capping ligand appears to be a very important factor influencing the type of structure that is observed. Thus, systems containing the basic trialkylamine ligand tren have Hg(CN)2 units N-bound to the transition metal; this generally results in an increase in structural dimensionality and particularly complicated, interesting structures that may have useful materials properties (e.g., 9). In the highly birefringent 2-D layer structure {Cu(tmeda)[Hg(CN)2]2}HgCl4, which has four N-bound cyano units per Cu(II), the capping ligand is also a trialkylamine (tmeda).14 Compounds containing the much less basic heterocyclic amine ligands bipy, phen, and terpy as capping ligands do not, for the most part, have N-bound Hg(CN)2 units and generally have a lower overall dimensionality as compared with the trencontaining structures. The dien capping group has an intermediate basicity, and thus 7 shows elements of systems containing both types of ligand. The impact of ligand basicity can be rationalized in terms of its influence on the transition-metal electron density. In these syntheses, both chloro- and N-cyano ligands are present and either (or both) can bind to the transition-metal (which also has a certain lability, as described above). A more electron-deficient transitionmetal cation would likely opt to ligate the anionic Clunits rather than the less electron-rich nitrile moieties of neutral Hg(CN)2, resulting in the chloride-bound structures observed in 1-7. Upon use of a basic capping

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ligand such as tren, however, the resulting electron-rich transition-metal cation more appropriately interacts with the neutral nitrile donors, yielding the N-cyano bridged structures 8 and 9. Note that ligand basicity was not observed to have a significant impact in a related study of amine-capped transition metal cations with [M(CN)2]- (M ) Au, Ag)10,11 as, in these cases, the nitrile donors are significantly more basic in their own right. We are currently expanding the range of capping ligand basicities in an effort to further control and increase structural dimensionality in Hg(CN)2-based coordination polymers and thereby enhance their potentially useful bulk materials properties. Acknowledgment. Financial support from Imperial Oil, NSERC, and Natural Resources of Canada are gratefully acknowledged. Supporting Information Available: Complete crystallographic data in CIF format for all nine reported crystal structures. This material is available free of charge via the Internet at http://pubs.acs.org.

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