A Concert of Weak Interactions Generates the Very Complex {Cu(tmeda)[Au(CN)4]2}‚1/3H2O Structure Michael J. Katz,† Harini Kaluarachchi,† Raymond J. Batchelor,† Gabriele Schatte,‡ and Daniel B. Leznoff*,†
CRYSTAL GROWTH & DESIGN 2007 VOL. 7, NO. 10 1946-1948
Department of Chemistry, Simon Fraser UniVersity, 8888 UniVersity DriVe, Burnaby, British Columbia, V5A 1S6 Canada, and Saskatchewan Structural Science Centre, UniVersity of Saskatchewan, 110 Science Place, Saskatoon, Saskatchewan, S7N 5C9 Canada ReceiVed June 19, 2007
ABSTRACT: An elaborate coordination polymer is formed using the weak Lewis-base [Au(CN)4]- coupled to a Jahn-Teller distorted CuII ion. Such structural complexity is inaccessible if a stronger structure-directing bonding interaction is present, as in the simpler NiII analog. Coordination polymer research has been strongly driven by the formation of fascinating supramolecular structures, topologies, and their subsequent physical properties.1-3 In the rational design of such polymers, cyanometalate building blocks have been used extensively because of their strict geometric constraints and the strong Lewis-base character of the N-cyano donors.4 The resulting M′-NC-M coordination interactions govern the polymer’s primary supramolecular structure and geometry, whereas secondary π-π stacking,5 hydrogen-bonding,6 and/or metallophilic interactions7,8 guide the overall polymer topology.9,10 The relatively neglected square-planar tetra-cyanoaurate(III) anion [Au(CN)4]- has proven to be a weak Lewis-base,11,12 unlike the related [Pt(CN)4]2- and the linear [Au(CN)2]-,13-15 which form a wide range of coordination polymers. Rational design of coordination polymers becomes more difficult when using only weak donors, in part because of the presence of many potential energy minima, each of which represents a different stable structure; this is a common origin of polymorphism.3,16,17 On the other hand, the removal of a strong structure-directing binding motif may allow access to a new range of highly complex structures,18 albeit with a lower predictability factor. To illustrate this point, we hereby report two coordination polymers using [Au(CN)4]- and [M(tmeda)]2+ units (tmeda ) N,N,N′,N′-tetramethylethylenediamine, M ) NiII, CuII), in which the weak Lewis-base N-cyano character of [Au(CN)4]- coupled with the weak binding associated with the Jahn-Teller axis of the CuII ion produces a remarkably complex coordination polymer structure, which greatly simplifies upon substitution of the CuII with the isotropic NiII cation. The aqueous reaction between Ni(NO3)2‚6H2O, tmeda, and KAu(CN)4 produces single crystals of {Ni(tmeda)[Au(CN)4]2} (1).19,20 The structure of 1 is a simple (4,4) corrugated net having octahedral NiII atoms at the vertices and AuIII atoms along the edges (Figure 1);1,21 the NiII-N(cyano) bond lengths span a short range of 2.052-2.120 Å. The square 10.3 Å net is delineated by the set of Ni4Au4(CN)8 atoms. In contrast with the metallophilicity observed in [Pt(CN)4]2- and [Au(CN)2]- systems,7,22,23 only AuIII-N(cyano) interactions impact [Au(CN)4]--based structures in general.11,24 This is also the case in 1, where the 2D sheets utilize Au(2)-N(1†) and Au(3)-N(6′′) interactions of 2.889(6) and 3.008(6) Å to stack the sheets (Figure 1b). These distances are similar to other previously reported unsupported Au-N interactions11 and are less than the sum of the van der Waals radii (3.12-3.27 Å).25 Intrasheet Au(2)-N(8‡) interactions of 3.091(5) Å are also present. * Corresponding author. Fax: 778-782-3765. Tel: 778-782-4887. Email:
[email protected]. † Simon Fraser University. ‡ University of Saskatchewan.
Figure 1. (a) 2D sheet of 1 viewed down the b-axis (AuIII-N interactions not shown). Note: “CN3” indicates C(3) and N(3) group, etc.; Au, yellow; Ni, purple; C, green; N, blue. Symmetry transformations: * -1 + x, -1 + y, z; † x, 1 + y, z; ′′ x, -1 + y, z; ‡ 1 + x, 1 + y, z. Selected bond lengths (Å) and angles (deg): Ni(1)-N(5) 2.052(4), Ni(1)-N(3) 2.059(4), Ni(1)N(7) 2.098(4), Ni(1)-N(2) 2.120(4), Ni(1)-N(12) 2.151(4), Ni(1)-N(11) 2.163(4), N(5)-Ni(1)-N(3) 171.50(18), N(7)-Ni(1)-N(12) 174.65(17), N(2)-Ni(1)-N(11) 174.23(16), C(2)-N(2)-Ni(1) 157.7(4), C(3)-N(3)Ni(1) 173.9(4), C(5)-N(5)-Ni(1) 167.5(4), C(7)-N(7)-Ni(1) 159.5(4). (b) Two sheets of 1 viewed end-on, showing intersheet Au-N interactions.
Under similar reaction conditions, substituting a CuII cation in place of NiII, blue needles of {Cu(tmeda)[Au(CN)4]2}‚1/3H2O (2) were initially produced in 26% yield. Blue blocks of the previously described molecular polymorph of {[Cu(tmeda)(µ-OH)]2[Au(CN)4]2} formed after subsequent solvent evaporation,19,20,26 thereby illustrating the extreme sensitivity of the system to reaction and crystallization conditions. The asymmetric unit of 2 consists of three unique CuII and seven AuIII atoms (Au(1) and Au(7) are on the inversion center and 2-fold axis special positions, respectively). The CuII centers are all bound by equatorial tmeda ligands and 2-4 N(cyano) groups; Cu(1) also binds a H2O ligand. The equatorial Cu-N(cyano) bonds span from 1.976(10) to 2.037(9) Å, similar to 1, but the axial ones are much longer (2.421(12)-2.456(11) Å;
10.1021/cg070557r CCC: $37.00 © 2007 American Chemical Society Published on Web 09/12/2007
Communications
Crystal Growth & Design, Vol. 7, No. 10, 2007 1947
Figure 2. Single (6,3) repeat unit with the Au(1*) from the interpenetrated network. TMEDA carbons as well as the cyanides of Au(7) and Au(5) removed for clarity. Note: “CN63” indicates C(63) and N(63) group, etc.; Au, yellow; Cu, red; C, green; N, blue; O, pink. Symmetry tranformations: ′ x, -y, 1/2 + z; ′′ x, -y, -1/2 + z; * 1 - x, y, 3/2 - z; † 1 - x, -1 - y, 2 - z; ‡ x, -1 - y, -1/2 + z; § 1/2 - x, -1/2 - y, 2 - z; 1/2 - x, -1/2 + y, 3/2 - z. Bond lengths (Å): Cu(1)-N(11‡) 2.636(12), Cu(1)-N(12) 2.037(9), Cu(1)-N(21) 2.456(11), Cu(2)-N(22) 2.032(11), Cu(2)-N(31) 2.421(12), Cu(2)-N(41) 1.995(11), Cu(3)-N(62′) 2.453(13), Cu(3)-N(42) 2.018(10), Cu(3)-N(61) 1.976(10). Bond angles (deg): N(12)-Cu(1)-N(21) 88.7(4), N(22)-Cu(2)-N(31) 82.0(4), N(22)-Cu(2)-N(41) 92.8(4), N(31)-Cu(2)-N(41) 88.1(4), N(62′)-Cu(3)-N(42) 85.5(4), N(62′)-Cu(3)-N(61) 86.5(4), N(42)-Cu(3)-N(61) 87.5(4). For additional bond lengths and angles for the metal environments, see the Supporting Information.
Figure 3. (a) Two parallel interpenetrated (6,3) nets; Au(4) atoms make up the six connection points. (b) Two sets of interpenetrated nets viewed edge-on down the c-axis. Au-N interactions link neighboring sets to one another (gray circle). (c) Interpenetrated nets are also held together via Au-N interactions along the c-axis (gray ellipse). Note: “CN63” indicates C(63) and N(63) group, etc.; Au, yellow; Cu, red; C, green; N, red; O, pink. Bond length (Å): Au(1)-N(73) 3.107(7) Bond angle (deg): C(73)-N(73)-Au(1) 112.6(3). (d) Close up view of the 10 Au(CN)4-cluster held via Au-N interactions involved in the stacking of the interpenetrated nets. Bond lengths (Å): Au(2)-N(32) 3.070(14), Au(2)-N(63) 3.052(12), Au(3)-N(52) 3.039(12), Au(4)-N(51) 2.764(13), Au(5)-N(23) 2.874(11), Au(6)-N(54′′) 3.068(10). Bond angles (deg): Au(2)-N(32)-C(32) 120.2(13), Au(2)-N(63)-C(63) 133.1(12), Au(3)N(52)-C(52) 146.3(12), Au(4)-N(51)-C(51) 148.4(13), Au(5)-N(23)-C(23) 148.8(12), Au(6)-N(54′′)-C(54′′) 162.1(14). For additional bond lengths and angles for the metal environments see ESI. See the Figure 2 caption for symmetry operations.
see the Supporting Information for a detailed description of each coordination sphere). The coppers and five gold centers form a
quarter of a 30 × 11.5 Å repeat unit (Figure 2). The shortest path traversed around this ring consists of 84 atoms, delineated by
1948 Crystal Growth & Design, Vol. 7, No. 10, 2007 Cu14Au14(CN)28 units. Axial Jahn-Teller bonds in CuII have been found to be 0.1-0.4 Å greater than the equatorial bonds; any such contacts in 2 above 2.5 Å were thus considered as weak interactions at best.27 These large rings in 2 repeat in two dimensions to yield a corrugated (6,3) net with vertices formed by each Au(4) unit. Because of the large size of the ring, a second (6,3) net interpenetrates through the center of the first (Figure 3a). The overall topology of 2 can be considered as two parallel interpenetrated (6,3) nets:1,21 weak Jahn-Teller Cu(1)-N(11q) interactions of 2.636(12) Å link interpenetrated sheets together. In addition, Au-N(cyano) interactions of 3.107(7) Å form a 1D chain, linking the interpenetrated sheets at Au(1) via CN(73) of the free Au(7) (Figure 3c), reinforcing the overall structure. As in 1, the 2D sheets in 2 stack via Au-N(cyano) interactions (Au(2)-N(63) ) 3.052(12) Å (panels b and d in Figure 3). This interaction helps support a cluster of 10 [Au(CN)4]- units linked to one another via Au-N interactions ranging from 2.764(13) to 3.070(14) Å (Figure 3d). Of these distances, the 2.764(13) and 2.874(11) Å are the shortest ever obtained for the [Au(CN)4]moiety; indeed, they are similar in length to AuIII-N distances in typical gold(III)-amine complexes.28,29 Thus, the concert of weak interactions, including N-cyanoaurate(III) binding to Jahn-Teller sites of CuII and Au-N(cyano) interactions, have produced a much more complex structure in 2 versus 1. The magnetic properties of both 1 and 2 were investigated in order to probe the ability of the AuIII building block to mediate magnetic exchange. The NiII polymer (1) has a χMT value of 1.18 cm3 K mol-1 at 300 K, consistent with an isolated octahedral NiII center. No change in χMT was observed until 35 K, at which point χMT decreased to 0.65 cm3 K mol-1 at 1.8 K. This data was fit to the Curie-Weiss equation, yielding g ) 2.2009(7) and θ ) -1.18(3) K. The data was also fit to an isolated NiII center with zero-field splitting (D) to yield g ) 2.1894(12) and D ) 6.02(20).30 The D value of 1 is larger than expected for this system, suggesting that some AuIII-mediated antiferromagnetic interactions are present.31 The room temperature χMT value of 2 was 0.39 cm3 K mol-1, as expected for an isolated Cu(II) ion. The χMT value is temperatureindependent until 14 K, below which it decreases to 0.32 cm3 K mol-1 at 1.8 K. This was fit to the Curie-Weiss equation, yielding g ) 2.0619(8) and θ ) -0.28(3), suggesting weak antiferromagnetic interactions.30 In general, it appears that [Au(CN)4]- is a poor mediator of magnetic exchange in these systems. These structures illustrate that a set of weak interactions acting in concert can generate extremely complex supramolecular structures that would otherwise be inaccessible using a dominant structure-directing bonding motif. Acknowledgment. financial support.
The authors acknowledge NSERC for
Supporting Information Available: Synthesis and CIF files for 1 and 2; detailed structural information for each metal coordination sphere in 2 (PDF). This material is available free of charge via the Internet at http:// pubs.acs.org.
Communications
References (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12)
(13) (14) (15) (16) (17) (18) (19)
(20) (21) (22) (23) (24) (25) (26) (27) (28) (29) (30) (31)
Batten, S.; Robson, R. R. Angew. Chem., Int. Ed. 1998, 37, 1460. Janiak, C. Dalton Trans. 2003, 2781. Moulton, B.; Zaworotko, M. J. Chem. ReV. 2001, 101, 1629. Dunbar, K. R.; Heintz, R. A. Prog. Inorg. Chem. 1997, 45, 283. Janiak, C. J. Chem. Soc., Dalton Trans. 2000, 3885. Beatty, A. M. CrystEngComm 2001, 51, 1. Gliemann, G.; Yersin, H. Struct. Bonding 1985, 62, 87. Schmidbaur, H. Chem. Soc. ReV. 1995, 24, 391. Roesky, H. W.; Andruh, M. Coord. Chem. ReV. 2003, 236, 91. Hartgerink, J. D.; Zubarev, E. R.; Stupp, S. I. Curr. Opin. Solid State. Mater. Sci. 2001, 5, 355. Shorrock, C. J.; Jong, H.; Batchelor, R. J.; Leznoff, D. B. Inorg. Chem. 2003, 42, 3917. Vitoria, P.; Muga, I.; Gutierrez-Zorilla, J. M.; Luque, A.; Roman, P.; Lezama, L.; Zuniga, F. J.; Beitia, J. I. Inorg. Chem. 2003, 42, 960. Falvello, L. R.; Toma´s, M. Chem. Commun. 1999, 273. Katz, M. J.; Aguiar, P. M.; Batchelor, R. J.; Bokov, A. A.; Ye, Z.G.; Kroeker, S.; Leznoff, D. B. J. Am. Chem. Soc. 2006, 128, 3669. Lefebvre, J.; Callaghan, F.; Katz, M. J.; Sonier, J. E.; Leznoff, D. B. Chem.sEur. J. 2006, 12, 6748. Bernstein, J. Polymorphism in Molecular Crystals; Oxford University Press: Oxford, U.K., 2002. Braga, D.; Grepioni, F. Chem. Soc. ReV. 2000, 29, 229. Blatov, V. A.; Carlucci, L.; Ciani, G.; Proserpio, D. M. CrystEngComm 2004, 6, 377. Crystal data for 1: C14H16N10Au2Ni, MW ) 777.01, triclinic, space group P1h, a ) 7.7850(5) Å, b ) 10.3020(12) Å, c ) 15.0958(11) Å, R ) 90.999(5)°, β ) 90.994(5)°, γ ) 112.195(5)°, V ) 1120.45(17) Å3, Z ) 2, Fcalcd ) 2.303 g cm-3, λ(Mo-KR) ) 13.912, T ) 173(2) K, 6860 unique reflections, 6085 observed (Io > 2.0σ(Io)). The final RF ) 0.0309 and RWF ) 0.0719 (observed data). Crystal data for 2: C14H16.66N10Au2CuO0.33, MW ) 787.83, monoclinic, space group C2/c, a ) 49.060(2) Å, b ) 24.6174(8) Å, c ) 11.4733(6) Å, β ) 100.313(2)°, V ) 13632.9(10) Å3, Z ) 24, Fcalcd ) 2.303 g cm-3, λ(Mo-KR) ) 25.064, T ) 293(2) K, 12235 unique reflections, 8331 observed (Io > 3.0σ(Io)). The final RF ) 0.0364 and RWF ) 0.0490 (observed data). See the Supporting Information for synthetic details. Wells, A. F. Three-Dimensional Nets and Polyhedra; John Wiley & Sons: New York, 1977. Leznoff, D. B.; Xue, B.-Y.; Batchelor, R. J.; Einstein, F. W. B.; Patrick, B. O. Inorg. Chem. 2001, 40, 6026. Leznoff, D. B.; Xue, B.-Y.; Patrick, B. O.; Sanchez, V.; Thompson, R. C. Chem. Commun. 2001, 259. Imakubo, T.; Tajima, N.; Tamura, M.; Kato, R.; Nishio, Y.; Kajita, K. J. Mater. Chem. 2002, 12, 159. Bondi, A. J. Phys. Chem. 1964, 68, 441. Katz, M. J.; Shorrock, C. J.; Batchelor, R. J.; Leznoff, D. B. Inorg. Chem. 2006, 45, 1757. Hathaway, B. J. In ComprehensiVe Coordination Chemistry; Wilkinson, G., Ed.; Pergamon Press: New York, 1987; Vol. 5. Maranogni, G.; Pitteri, B.; Bertolasi, V.; Gilli, G.; Ferretti, V. J. Chem. Soc., Dalton Trans. 1986, 1941. Robinson, W. T.; Sinn, E. J. Chem. Soc., Dalton Trans. 1975, 726. Kahn, O. Molecular Magnetism; VCH: Weinheim, Germany, 1993. Draper, N. D.; Katz, M. J.; Batchelor, R. J.; Leznoff, D. B. J. Inorg. Organomet. Polym. Mater. 2006, 447.
CG070557R
