摘要:
Bis(N-methylamidino-O-methylurea)copper(II) cation: a planar building block for the construction of hydrogen-bonded rhombic (4, 4) grids Peter Hubberstey,* Unchulee Suksangpanya and Claire L. Wilson School of Chemistry, University of Nottingham, University Park, Nottingham, UK NG7 2RD. E-mail: peter.hubberstey@nottingham.ac.uk Received 20th July 2000, Accepted 22nd August 2000, Published 30th August 2000 Bis(N-methylamidino-O-methylurea)copper(II) cations and chloride anions self-assemble to form an elegant hydrogen-bonded rhombic (4, 4) grid. The four-fold connectivity of the square planar cation [Cu: 1.957(2), 1.970(2) A, N¡�¡�Cu¡�¡�N 88.91(9)¡Æ] arises from the presence of four pairs of N¡©H donors, set at 90¡Æ to each other, which form hydrogen-bonds to four separate chloride anions.The rhombic (4, 4) grid [Cu¡�¡�¡�Cu separations: edge 10.388(2) A, major diagonal 15.874(2) A, minor diagonal 13.403(2) A] arises from the fact that adjacent cations are twisted through 90¡Æ to generate the same hydrogen-bonded supramolecular synthon in all four directions. The sheets adopt a sinusoidal (corrugated) profile. This somewhat surprising observation is thought to result from a compromise between the structural requirements of the supramolecular synthon and the steric requirements of the four juxtaposed methyl groups which form lipophilic channels running parallel to the x-axis. The construction of metal supported supramolecular architectures1¡©3 is a rapidly expanding facet of crystal engineering.4,5 The level of sophistication attained thus far is such that network structure and topology can be readily controlled by management of the two connecting units, transition metal centre and bridging ligand.1,2 Initially, structural diversity originated in the coordination properties of the metal centre [linear AgI,6 T-shaped MII(NO3)2 (M = Co, Cd),7¡©10 square planar MII (M = Co, Ni, Cu, Zn, Cd)11 or tetrahedral CuI 12], the bridging ligands being restricted to bidentate molecular rods (e.g., 4,4¢¥-bipyridine, 8,9,12 bis(pyridin-4-yl)ethyne,10 3,6-bis(pyridin-4-yl)-1,2,4,5- tetrazine6).More recently, however, diverse multidentate bridging ligands have been devised and synthesised leading to a greater variety in polymer design. The conformations of these connecting units include trigonal planar [e.g., 1,3,5-triazine,13 2,4,6-tris(pyridin-4-yl)-1,3,5-triazine,14 1,3,5-tris(4-ethynylbenzonitrile)benzene15], tetrahedral (e.g., hexamethylenetetramine,16 4,4¢¥,4¢¥¢¥,4¢¥¢¥¢¥-tetracyanotetraphenylmethane17), square planar (e.g., 1,2,4,5- tetracyanobenzene,18 7,7,8,8-tetra-cyanoquinodimethane19) and octahedral [e.g., hexa-kis(imidazol- 1-ylmethyl)benzene20].A further development of this work has involved the replacement of the mononuclear metal centres by molecular clusters. For example, [Cu2X2] (X = Cl, Br or I) rhomboids21,22 and [Cu4X4] cubane tetramers23 act as square planar and tetrahedral connecting centres, respectively. Architectures based on polymeric [Cu¡ÄX¡Ä] chains and sheets have also been constructed.13,21,24 All these supramolecular systems involve coordinate connectivities.We have now embarked on a programme to replace the coordinate links by hydrogen-bonded contacts. Although hydrogen-bonding interactions have long been considered to be of importance in crystal engineering,4,5 it is only recently that transition metal complexes containing ligands with versatile hydrogen bonding capability have been deployed to construct extended architectures.25¡©32 Initially, we designed a cationic hydrogen-bonding building block with linear connectivity, namely, copper(II) coordinated by polymethylene linked bis(amidino-Oalkylurea) ligands (Scheme 1a).26,27 Using two pairs of N¡© H moieties [N131¡©H13B/N104¡©H104 and N231¡© DOI: 10.1039/b005851n H23B/N204¡©H204], these cations alternate with a diversity of anions (e.g., Cl¡©, [ROSO3]¡© (R = Me, Et) and [(MeO)2BF2]¡©)26,27 to form 1D chains (Scheme 2).The observation that by using a single pair of N¡©H moieties [N106¡©H106/N206¡©H206] these cations are also able to hydrogen-bond to anions in a direction orthogonal to the propagation of the chain (Scheme 2), prompted us to devise a planar cationic hydrogen-bonding building block with four-fold connectivity. Such a species has the ability to generate sheet architectures. It is the design, synthesis and structural characterisation of a novel type of (4, 4) network sheet construction based on bis(N-methylamidino-Omethylurea)copper(II) (Scheme 1b) that form the basis of this communication. Scheme 2 Chain formation in [CuLi]Cl2 complexes (Li = N,N¢¥-bis(amidino-O-alkylurea)-1,2-diaminoethane. Methanolysis of N-methyl-2-cyanoguanidine, prepared by reaction of methylamine hydrochloride with sodium dicyanamide in butan-1-ol,¢Ó in the presence of copper(II) chloride gave bis(N-methylamidino-Omethylurea)copper(II) chloride,¢Ô single crystals of which were grown by seeding a saturated solution of the product in MeOH.CrystEngComm, 2000, 26 Scheme 1 Two-fold (linear) (a) and four-fold (square planar) (b) cationic hydrogen-bonding building blocks.Table 1 Crystal data of C8H20Cl2CuN8O2a Values Properties 394.76 Monoclinic, P21/c (no. 14) 5.2682(8) 13.403(2) 11.065(2) 94.561(3) 778.8(2) 21.762 150(2) 4987 1918 1415 0.0372 0.0897 MSpace group a/A b/A c/A ¥â/¡Æ U/A3 Z¥ì/mm¡©1 T/K Reflections Unique reflections (Rint = 0.048) Reflections with I > 2¥ò(I) RawR The data were collected on a Bruker Smart CCD area detector diffractometer equipped with an Oxford Cryosystem open flow cryostat.33 The structure was solved by direct methods using SIR92 34 and refined by full matrix least squares on F2 using SHELXL-93.35 All hydrogen atoms were found in Fourier difference syntheses.Amino and imino hydrogen atoms were refined with restrained N¡©H [0.88(2) A] distances. Methyl hydrogens were placed in geometrically calculated positions and refined using a riding model. The chlorine atom was disordered over two positions with occupation factors of 0.75(5) [Cl(1)] : 0.25(5) [Cl(2)].All structure diagrams were generated using the CAMERON computing package.36 Click here for full crystallographic data (CCDC no. 1350/32). Fig. 1 The square planar [Cu(L1)2]2+ cation showing the four fold connectivity arising from the presence of four pairs of N¡©H donors, set at 90¡Æ to each other, which form hydrogen-bonds to four separate chloride anions. Click image or here to access a 3D representation. Fig. 2 View perpendicular to the (1, 0, 2) plane showing the (4, 4) network motif of the 2D sheet architecture of [Cu(L1)2]Cl2. Click image or here to access a 3D representation. The structure determination revealed an elegant hydrogenbonded 2D sheet structure based on alternating cations and anions (Table 1).The copper(II) atom is located on an inversion centre and coordinated by two symmetry related N-methylamidino-O-methylurea molecules (L1) to give the square planar [Cu(L1)2]2+ cation [Cu¡�¡�¡�N: 1.957(2), 1.970(2) A, N¡�¡�¡�Cu¡�¡�¡�N 88.91(9)¡Æ] (Fig. 1). The four-fold connectivity of the [Cu(L1)2]2+ cation arises from the presence of four pairs of N¡©H donors, set at 90¡Æ to each other, which form hydrogen-bonds to four symmetry related chloride anions (Scheme 1; Fig. 1). Selected interatomic distances and angles for the hydrogen-bonded contacts are collated in Table 2. The [Cu(L1)2]2+ cations are thus linked through chloride anions to generate a 2D (4, 4) network parallel to the (1, 0, 2) plane (Fig.2). Adjacent cations are twisted through 90¡Æ to generate the same supramolecular synthon (Scheme 3) in all four directions. It follorhombic grid with Cu¡�¡�¡�Cu separation of 10.388(2) A, major and minor diagonals of 15.874(2) and 13.403(2) A and an obtuse angle of 99.65(2)¡Æ. The sheets adopt a sinusoidal (corrugated) profile with the cations at 0 and 180¡Æ and the chloride anions at 90 and 270¡Æ (Fig. 3). This is somewhat surprising in view of the planarity of the cation and the preferred planar arrangement of the hydrogen-bonding interactions. Although the reason for the non-planarity of the sheet is uncertain, it may be the result of a compromise between the structural requirements of the hydrogenbonded supramolecular synthon and the steric requirements of the four juxtaposed methyl groups (Fig.2), which form lipophilic channels along (x,0,�ö) and (x,�ö,0). The sheets are stacked in phase, with amino nitrogen atoms N(131) of cations from adjacent sheets located along the axial direction of the copper(II) coordination sphere [Cu¡�¡�¡�N(131) 3.10 A; N(102)¡©Cu¡�¡�¡�N(131) 87.1(1)¡Æ; N(106)¡©Cu¡�¡�¡�N(131) 91.6(1)¡Æ]. This arrangement differs from those seen in the polymethylene linked bis(amidino-O-alkylurea) copper(II) complexes where the anions are remotely located in the axial positions of the copper(II) coordination sphere.26,27Table 2 Pertinent interatomic distances and angles for the hydrogen-bonding contacts in [Cu(L1)2]Cl2a Symmetry of Cl Contact N–H···Cl x, y, z x, y, z 1 – x, –0.5 + y, 0.5 – z 1 + x, 0.5 – y, –0.5 + z x, y, z x, y, z N 131–H 13B···Cl 1 N 104–H 104···Cl 1 N 102–H 102···Cl 1 N 106–H 106···Cl 1 N 131–H 13B···Cl 2 N 104–H 104···Cl 2 N 102–H 102···Cl 2 N 106–H 106···Cl 2 1 – x, –0.5 + y, 0.5 – z 1 + x, 0.5 – y, –0.5 + z 162(3) 160(3) 163(2) 159(2) 158(3) 168(3) 161(3) 153(3) a Two sets of distances are quoted owing to the chloride anion being disordered over two sites with occupancy 0.75(5) [Cl(1)] : 0.25(5) [Cl(2)].Scheme 3 Supramolecular synthon in [Cu(L1)2]Cl2. Fig. 3 View parallel to the (1, 0, 2) plane showing the in-phase sinusoidal profile of the sheet structure of [Cu(L1)2]Cl2.In conclusion, we have shown that the bis(Nmethylamidino-O-methylurea)copper(II) cation can act as a hydrogen-bonding building block with four-fold connectivity linking chloride anions to generate a rhombic (4, 4) grid structure. We are presently pursuing our prediction that this cation will form hydrogen-bonding contacts to a variety of anions to generate a rich diversity of (4, 4) networks. Acknowledgements We thank the EPSRC for the provision of a diffractometer and the Royal Thai Government for financial support (to U.S.). N–H···Cl/° N···Cl/Å H···Cl/Å N–H/Å 3.222(6) 3.125(6) 3.361(6) 3.295(6) 3.45(2) 3.17(2) 3.27(2) 3.40(2) 2.43(2) 2.32(3) 2.55(2) 2.48(2) 2.68(3) 2.34(4) 2.46(3) 2.62(3) 0.82(3) 0.84(3) 0.84(2) 0.85(2) 0.82(3) 0.84(3) 0.84(2) 0.85(2)References 1 A.J. Blake, N. R. Champness, P. Hubberstey, W.-S. Li, M. Schröder and M. A. Withersby, Coord. Chem. 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Pearce, CAMERON, Chemical Crystallography Laboratory, University of Oxford, 1996.37 S. L. Shapiro, E. S. Isaacs and L. Freedman, J. Pharm. Soc., 1961, 50, 798; F. L. Rose and G. Swain, J. Chem. Soc., 1956, 4422. 38 W. A. Baker and M. Daniels, J. Inorg. Nucl. Chem., 1963, 25, 1194; K. Kawano and K. Odo, Yuki Gosei Kagaku Kyokaishi, 1962, 20, 568 (Chem. Abs., 1962, 58, 12150c); R. L. Dutta and P. Ray, J. Ind. Chem. Soc., 1959, 36, 567. Footnotes 1H-NMR (D ¢Ó N-methyl-2-cyanoguanidine, L. A mixture of methylamine hydrochloride (0.05 mole; 3.375 g) and sodium dicyanamide (0.05 mole; 4.45 g) in butan-1-ol (50 cm3) was stirred under reflux overnight.37 Filtration followed by reduction in solvent volume gave a white precipitate, which was washed with MeCN and dried in vacuum. Yield 83% (0.0415 mole; 4.062 g). Mp 60¡©64 ¡ÆC. Found (calc.) for C3H6N4: C 36.20 (36.70); H 6.10 (6.15); N 56.90 (57.10)%. IR ( ¥í/cm¡©1): 3390s,br; 3179s,br; 2995s; 2810mw; 2241mw; 2164s; 1625s; 1470s; 1437s; 1412s; 1241ms; 1162ms; 1124ms; 1007mw; 915ms; 693ms; 572ms; 519ms; 476ms. EI MS (m/z): 98 [M]+, 82 [M¡© NH2]+, 68 [M¡©N2H2] +, 67 [M¡©N2H3]+, 56 [M¡©C2H4N]+. 2O), ¥ä (ppm): 2.74(s, 3H, CH3). 13C-NMR (DMSO), ¥ä (ppm): 27.87 (CH3), 120.65 (CN), 162.16 (C¡© NH2). ¢Ô [Cu(L1)2]Cl2. CuCl2¡�2H2O (1.25 mmoles; 0.213 g) and L (2.5 mmoles; 0.245 g) were dissolved in methanol (50 cm3) and the mixture refluxed for 6 h.38 Reduction in solvent volume gave a purple precipitate. Yield 85% (1.057 mmoles; 0.417g). Found (calc.) for C8H20N8CuCl2O2: C 22.50 (22.30); H 4.90 (5.60); N 26.80 (26.00). IR ( ¥í/cm¡©1): 3237s; 3133ms; 3047ms; 2969ms; 2873ms; 1670vs; 1595s; 1546ms; 1460ms; 1405s; 1258mw,sh; 1230s; 1167ms; 1036w; 987w; 930w; 800mw; 763mw; 729ms; 586w; 476mw. FAB MS (m/z): 322 [Cu(L1¡©H+)]+. UV/VIS (MeOH): ¥ëmax 573 nm ( ¥å = 24 l mol¡©1 cm¡©1). CrystEngComm �Ï The Royal Society of Chemistry
ISSN:1466-8033
DOI:10.1039/b005851n
出版商:RSC
年代:2000
数据来源: RSC