332 Acta Chim. Slov. 2005, 52, 332–335 Short Communication Synthesis and Structure of a Ni(II)-Cu(II)-Ni(II) THnuclear Complex With a New Macrocyclic Complex Ligand Xiao-Zeng Li,a* Jun-Hong He,a and Dai-Zheng Liaob "Department of Chemistry, Tianjin University, Tianjin 300072, P. R. China. E-mail: tianuleexz@tom.com b Department of Chemistry, Nankai University, Tianjin 300071, P. R. China Received 29-03-2005 Abstract A trinuclear complex, [Cu(NiL)2(NCS)J, was prepared by the reaction of a new m acrocyclic oxamido complex ligand NiL, Cu(C10)2-6H20 and KNCS. L denotes the doubly deprotonated form of dimethyl 5,6,7,8,15,16-hexahydro-15-methyl-6,7-dioxodibenzo[l,4,8,ll]tetraazacyclotetradecine-13,18-dicarboxylate. Excess Cu(C10)2-6H20 is necessary for the formation of the title compound. The structure of the title complex was further characterized by X-ray single-crystal analysis. Cu(II) and each Ni(II) is bridged by the oxamido group from the corresponding macrocyclic ligand. The coordination geometry around each Ni(II) ion is slightly distorted square planar with N4 donor set, and the Cu(II) ion has a distorted octahedral coordination geometry of 04N2 donor set. tt—tt interactions and C-H—O hydrogen bonds link the molecules to form two-dimensional supramolecular layers. Key words: synthesis, crystal structure, macrocyclic compound, complex ligand, Ni(II)-Cu(II)-Ni(II) complex Introduction Macrocyclic complexes have received considerable attention because of their relationship to biomimetic and catalvtic systems and the applications in biologv, medicine and chemical techniques.14 Polynuclear complexes have also attracted extensive interests due to their significance in catalysis, biochemistry, materials science and etc.5~7 “Complexes-as-ligands” is an important approach for preparing polynuclear complexes.6'7 This contribution reports the preparation and crystal structure of a new Ni(II)-Cu(II)-Ni(II) trinuclear macrocyclic complex [Cu(NiL)2(NCS)2], in which NiL is a new tetraazamacrocyclic nickel(II) complex ligand (Chart 1). L denotes the dianion of dimethyl 5,6,7,8,15,16-hexahydro-15-methyl-6,7-dioxodibenzo[ l,4,8,ll]tetraazacyclotetradecine-13,18-dicarboxylate. Two other Ni(II)-Cu(II)-Ni(II) trinuclear complexes, each of which contains two molecules of another NiL like complex ligand, were reported by some of us.8'9 Ali the three complex ligands incorporate oxamido and phenyl groups. Oxamido group is a good bridge capable of linking metals to form polynuclear complexes and mediating ferro- and antiferromagnetic coupling betvveen metal centers.711 Complex fragments similar to NiL can take part in normal and special 77— -77- interactions controlling molecular packing in crystals and playing a role in molecular recognition events betvveen isomers.812 O Ni O^N7 n O Chart 1. NiL. Results and discussion Svnthesis The new macrocyclic complex ligand NiL can be easily synthesized by a method similar to that to prepare its analogues.13 The title complex [Cu(NiL)2(NCS)2] was prepared by the reaction of NiL, Cu(C10)2-6H20 and KNCS in methanol. It is notable that excessive Cu(C10)2-6H20 was necessary for the formation of the title compound. When the molar ratio of NiL and Cu(C10)2-6H20 was 2:1 (the same ratio of NiL and Cu in the title compound), the reaction mixture could not turned into a solution after being stirred and heated, and the solid separated from the reaction mixture was NiL rather than species containing both NiL and Cu, whether in no existence of NCS~ or in the existence of NCS~ in more than 2 times excess. When the molar ratio of NiL, Cu(C10)2-6H20 and KNCS was 1:2:6.3, the reaction mixture changed into an orange solution after O Li et al. Synthesis and Structure of a Ni(II)-Cu(II)-Ni(II) Trinuclear Complex Acta Chim. Slov. 2005, 52, 332–335 333 being stirred and heated at 65 °C for a few min, and the title compound was obtained in the end. The formerly reported Ni(II)-Cu(II)-Ni(II) trinuclear complexes were also prepared by using NiL like complex ligands in the existence of excess Cu(00)2-6H20, which was not discussed in the former contributions.8'9 Crystal Structure of the Title Complex [Cu(NiL)2(NCS)2] The title complex has centrosymmetric molecules (Figure 1). The oxamido groups of the two NiL ligands chelate the Cu center in trans fashion. Cu resides in a distorted octahedral surrounding formed by four oxa-mido O atoms and two N atoms from the NCS~ ligands. The two N atoms and two O atoms occupy the equatorial positions in trans fashion. The other two O atoms oc-cupy the apices. The two Cu-N bonds are shorter than the four Cu-O bonds (See Table 1), which presumably reflects that NCS~ bonds Cu(II) more tightly than the oxamido group due to the negative charge on NCS". Table 1. Selected bond lengths (A) and angles (°) for the title complex. Figure 1. Molecular structure of the title complex. The two Cu-O bonds (2.389 A) involving the apical O atoms are considerably longer than the four coordination bonds on the equatorial plane. Jahn-Teller effect is responsible for the remarkable elongation. In the cases of the two formerh/ reported Ni(II)-Cu(II)-Ni(II) trinuclear complexes with the formulae of [Cu(NiL)2(H20)2](004)2 and [Cu(NiL)2(CH3OH)2] (C104)2}, one oxamido O atom of each complex ligand was involved in the shortest Cu-O bond.8'9 The apices of the Cu(II) coordination octahedron in the former complex are occupied by the other two oxamido O atoms, and those of the later complex are taken by the two CH3OH ligands. The intramolecular distance betvveen the Cu atom and the Ni atom is 5.364 A. The Ni atom resides in a distorted square-planar N4 environment. The devia-tions of the four N atoms from their mean plane are in the range of -0.066—0.066 A. The Ni atom is 0.057 A away from the N4 plane. The Ni-N bond lengths (1.858 ~ 1.871 A) belong to the reported shorter ones14 and are quite similar to those in the Ag(I)-Ni(II) complex of another NiL like ligand.11 Cu(l)-N(5) 1.927(4) Ni(l)-N(4) 1.858(3) Cu(l)-0(1) 2.062(2) Ni(l)-N(3) 1.862(3) Cu(l)-0(2) 2.389(3) Ni(l)-N(l) 1.871(3) Ni(l)-N(2) 1.858(3) 0(l)-Cu(l)-0(2) 74.5(1) N(5)#l-Cu(l)-N(5) 180.0(2) 0(2)#l-Cu(l)-0(2) 180.0(1) N(5)#l-Cu(l)-0(1) 86.9(1) N(2)-Ni(l)-N(4) 179.3(2) N(5)-Cu(l)-0(1) 93.2(1) N(2)-Ni(l)-N(3) 93.1(1) 0(1)-Cu(l)-0(1)#1 180.0(1) N(4)-Ni(l)-N(3) 86.5(1) N(5)-Cu(l)-0(2)#1 92.3(1) N(2)-Ni(l)-N(l) 86.7(1) 0(1)-Cu(l)-0(2)#1 105.5(1) N(4)-Ni(l)-N(l) 93.8(1) N(5)-Cu(l)-0(2) 87.7(1) N(3)-Ni(l)-N(l) 172.4(2) #1 = -x + 1, -y + 2, -z + 1. Figure 2. Plots showing the tt—tt interactions. Only one asym-metric unit of each [Cu(NiL)2(NCS)2] molecule is depicted for the concision of the plots. Each of the two NiL fragments of a trinuclear molecule overlaps on one side with a NiL fragment of a neighboring trinuclear molecule (Figure 2, left) and overlaps on the other side with a NiL fragment of another neighboring trinuclear molecule (Figure 2, right). Many of the atom-to-atom distances betvveen the overlapping NiL fragments fall into the range of tt—tt interactions (<3.80 A).15 As in some cases reported by us 11,12 N(2), N(3) and C(2) (Figure 2) belong to non-aromatic 77--systems. Non-aromatic 77--systems can also be involved in tt—tt interactions, though descriptions on such cases are stili rare.11121618 The above tt---tt interactions link the complex molecules to form su-pramolecular layers (Figure 3) in the crystal. The linking in the layers is further strengthened by intermolecular C-H—O bonds. IR Spectra of the Title Complex The bands at ca 1740 cm4 in the IR spectra of the free NiL ligand and the title complex can be as-signed to the absorption of C=0 (ester).1013 The band at 1670 cm4 for the free NiL ligand is attributed to v(C=0) (oxamido). Two bands at 1630 and 1600 cm4 Li et al. Synthesis and Structure of a Ni(II)-Cu(II)-Ni(II) Trinuclear Complex 334 Acta Chim. Slov. 2005, 52, 332-335 Figure 3. A portion of a supramolecular layer interlinked by tt—tt interactions and C-H—O hydrogen bonds. for the title complex can be ascribed to the absorption of v(C= O) (oxamido), which shows red-shift compared to the corresponding band for the free ligand due to the Cu-O coordination and shows splitting due to the two obviously different Cu-O bond lengths. The band at ca 2080 cm4 in the IR spectra of the title complex is attributed to the absorption of NCS". Conclusions A Ni(II)-Cu(II)-Ni(II) trinuclear complex was synthesized by “complex-as-ligand” approach using a new mononuclear macrocyclic complex ligand. The synthesis unfolded that excess Cu(C10)2-6H20 is neces-sary to form the title compound. This observation may be of meaning in directing assembly processes of like systems. The crystal structure of the title complex was determined by X-ray single crystal analysis. Experimental General. Ali the starting materials were of analyti-cal grade and were used as purchased without further purification. Analyses of C, H and N were carried out on a Perkin-Elmer 240 elemental analyzer. The i.r. spectra were recorded on a BIO-RAD FTS 3000 infrared spectrophotometer. Synthesis. Dimethyl 2,2’-(oxalyldiimino)bis(phen ylglyoxylate) was prepared by a literature method.13 NiL: The mixture of dimethyl 2,2’-(oxalyldiim ino)bis(phenylglyoxylate) (0.8184 g, 1.987 mmol), Ni(Ac)2-4H20 (0.4944 g, 1.987 mmol), triethylamine (1.2 mL), 1,2-propanediamine (0.1474 g, 1.987 mmol) and MeOH (25 mL) was stirred and heated at about 65 °C for 6 h and then cooled to room temperature. The red solid was collected by filtration, washed with MeOH and dried in vacuum to afford NiL as a red powder (0.6848 g, yield 68.0%). Anal. Calcd for C23H20N4NiO6: C 54.47, H 3.98, N 11.05.Found: C 54.35, H 4.03, N 11.00. IR (KBr) v 1741, 1670, 1595, 1549, 1442, 1389, 1347, 1215, 1168, 1045, 748 cm4. [Cu(NiL)2(NCS)2]: The mixture of NiL (0.0507 g, 0.1 mmol), Cu(C104)2-6H20 (0.0741 g, 0.2 mmol), KNCS (0.048 g, 0.63 mmol) and MeOH (70 mL) was stirred and heated at 65 °C for 15 minutes and then cooled to room temperature. The filtrate of the mixture was evaporated at room temperature for 17 days, and orange crystals suitable for X-ray single-crystal analysis were obtained (0.0269g, yield 45.0%). Anal. Calcd for C48H40CuN10Ni2O12S2: C 48.60, H 3.45, N 12.00. Found: C 48.29, H 3.38, N 11.73. IR (KBr) v 2083, 1740, 1630, 1600, 1580, 1550, 1435, 1410, 1340, 1215, 1165, 1040, 750 cm4. X-Ray structure analysis. Diffraction data for the single crystals of the title complex were collected by o)-scans technique on a Bruker Smart-1000-CCD area detector with Mo Ka radiation and graphite monochro-mator. Further details of crystal data, data collection and refinement are listed in Table 2. The structure was solved by direct method and subsequent Fourier difference techniques and refined using full-matrix least-squares procedure on F2 with anisotropic thermal parameters for ali non-hydrogen atoms (SHELXS-97 and SHELXL-97).19 Hydrogen atoms were added geo-metrically and refined with the riding model position parameters and fixed isotropic thermal parameters. Li et al. Synthesis and Structure of a Ni(II)-Cu(II)-Ni(II) Trinuclear Complex Acta Chim. Slov. 2005, 52, 332–335 335 Further details of the crystal structure investigation are available from the Cambridge Crystallographic Center with quotation number CCDC 266794.20 Table 2. Data collection and processing parameters for the title complex. Empirical formula C48H4oCuNioNi2Oi2S2 Formula weight 1193.98 Temperature 293(2) K Wavelength 0.71073 A Monochromator Graphite Crystal system Triclinic Space group Pl Unit celi dimensions a = 9.507(4) A, a= 117.312(6)° b = 11.921(4) A, /3= 96.829(6)" c = 12.536(4) A, y= 99.523(6)" Vohune, Z 1213.8(8) A3, 1 Calculated density 1.633 g/cm3 Absorption coefficient 1.363 mm"1 F(000) 611 Crystal size 0.30 x0.20 x 0.10 mm ^Range for data collection 1.88° to 25.02° Limiting indices -11 2o(I)] Data / restraints / parameters 4240 / 1 / 341 Goodness-of-fit on F2 1.018 Finali? indices [/>2o(i)] Rl = 0.0423, wR2 = 0.0943 R indices (ali data) «1 = 0.0692, wR2 = 0.1050 Largest diff. peak and hole 0.629 and -0.377 e-A~3 References 1. J. Costamagna, G. Ferraudi, B. Matsuhiro, M. Campos-Vallette, J. Canales, M. Villagrán, J. Vargas, M. J. Aguirre, Coord. Chem. Rev. 2000, 196, 125–164. 2. A. McAuley, S. Subramanian, Coord. Chem. Rev. 2000, 200–202, 75–103. 3. T. J. Hubin, Coord. Chem. 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Durant, /. Chem. Soc, Perkin Trans. 2, 1999, 795-800. 15. C. Janiak, /. Chem. Soc, Dalton Trans. 2000, 3885-3896. 16. C. V. K. Sharma, K. Panneerselvam, F. Pilati, G. R. Desiraju, /. Chem. Soc. Perkin Trans. 2, 1993, 2209-2216. 17. Y Kang, C. Seward, D. Song, S. Wang, Inorg. Chem. 2003, 42, 2789-2797. 18. S. Chowdhury, M. G. B. Drew, D. Datta, Inorg. Chem. Commun. 2003, 6, 1014-1016. 19. G. M. Sheldrick. SHEFXS-97 and SHEFXF-97, Softvvare for Crystal Structure Analysis. Siemens Analytical X-ray Instruments Inc., Madision, Wisconsin, 1997. 20. Ouotation number CCDC 266794 at www.ccdc.cam. ac.uk/conts/retrieving.html [or from the Cambridge Crystallographic Data Centre (CCDC), 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44(0)1223-336033; email: deposit@ccdc.cam.ac.uk]. Povzetek Trijedrni kompleks [Cu(NiL)2(NCS)2] smo pripravili z reakcijo novega makrocikličnega oksamido liganda NiL, Cu(ClO)2•6H2O in KNCS (L je oznaka za dvakrat deprotonirano obliko dimetil 5,6,7,8,15,16-heksahidro-15-metil-6,7-dioksodibenzo[1,4,8,11]tetraazaciklotetradecin-13,18-dicarboksilata). Spojini smo določili strukturo z rentgensko strukturno analizo. Bakrovi in nikljevi atomi so povezani z oksamidno skupino. Geometrija štirih dušikovih atomov, koordiniranih na Ni(II), je kvadratno planarna, na Cu(II) pa so oktaedrično koordinirani štirje kisikovi in dva dušikova atoma. ?•••? interakcije in C–H•••O vodikove vezi povezujejo molekule v dvodimenzionalne supramolekularne plasti. Li et al. Synthesis and Structure of a Ni(II)-Cu(II)-Ni(II) Trinuclear Complex