A new polynuclear copper(II) complex [Cu7(OH)6Cl2- (pn)6(H2O)2](C(CN)3)4Cl2 with hydroxo-bridging ligands has been prepared; the centrosymmetric cluster cation can be described as two Cu4O3Cl distorted cubane units sharing one copper cation.Clemente Juan, Juan Modesto, Juan.M.Clemente@uv.es ; Gomez Garcia, Carlos Jose, Carlos.Gomez@uv.es ; Coronado Miralles, Eugenio, Eugenio.Coronado@uv.e

Clemente Juan, Juan Modesto

Coronado Miralles, Eugenio

Golhen, Stéphane

Gómez García, Carlos José

Sala Pala, Jean

Thétiot, Franck

Triki, Smaïl

Smaïl Triki

Franck Thétiot

Jean Sala Pala

Stéphane Golhen

Juan M. Clemente-Juan

Carlos J. Gómez-García

Eugenio Coronado

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Heptanuclear hydroxo-bridged copper cluster of the 
dicubane-like type: structural and magnetic characterisations of 
[Cu7(OH)6Cl2(pn)6(H2
O)2](C(CN)3)4Cl2 (pn = 
1,3-diaminopropane)

A new polynuclear copper(II) complex [Cu7(OH)6Cl2- (pn)6(H2O)2](C(CN)3)4Cl2 with hydroxo-bridging ligands has been prepared; the centrosymmetric cluster cation can be described as two Cu4O3Cl distorted cubane units sharing one copper cation

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Communicationwww.rsc.org/chemcommCHEMCOMMHeptanuclear hydroxo-bridged copper cluster of the dicubane-liketype: structural and magnetic characterisations of[Cu7(OH)6Cl2(pn)6(H2O)2](C(CN)3)4Cl2 (pn = 1,3-diaminopropane)†Smaïl Triki,*a Franck Thétiot,a Jean Sala Pala,a Stéphane Golhen,b Juan M. Clemente-Juan,cCarlos J. Gómez-Garcíac and Eugenio Coronadoca UMR CNRS 6521, Univ. de Bretagne Occidentale, BP 809, 29285 Brest Cedex, France.E-mail: smail.triki@univ-brest.frb UMR CNRS 6511, Univ. de Rennes 1, 35042 Rennes Cedex, Francec Instituto de Ciencia Molecular, Univ. de Valencia, Dr. Moliner 50, 46100 Burjasot, SpainReceived (in Cambridge, UK) 14th June 2001, Accepted 12th September 2001First published as an Advance Article on the web 5th October 2001A new polynuclear copper(II) complex [Cu7(OH)6Cl2-(pn)6(H2O)2](C(CN)3)4Cl2 with hydroxo-bridging ligandshas been prepared; the centrosymmetric cluster cation canbe described as two Cu4O3Cl distorted cubane units sharingone copper cation.Various multinuclear copper(II) complexes have been reportedin the last decade with a great number of simple andsophisticated bridging ligands;1–5 however, some nuclearitiesremain comparatively scarce. In the case of tetranuclearcomplexes with Cu4O4 cubane-like clusters some exampleshave been thoroughly described,2 but to date little is knownabout clusters involving more than four metal centres.3,4Concerning the heptanuclear copper(II) clusters, as far as we areaware, only one example of the dicubane-like type has beendescribed.5 Here we report the structure and preliminarymagnetic studies of a novel vertex sharing dicubane-likeheptanuclear copper(II) cluster [Cu7(OH)6Cl2(pn)6(H2O)2]-(tcm)4Cl2 (1) [pn = 1,3-diaminopropane; tcm2 = C(CN)32 =tricyanomethanide] with chloro- and hydroxo-bridging li-gands.1.00 mL (12 mmol) of 1,3-diaminopropane (pn) was slowlyadded to a warm aqueous solution of CuCl2·2H2O (12 mmol)and then an aqueous solution of sodium hydroxide (12 mmol)was added. To the resulting clear solution were immediately andconsecutively added concentrated aqueous solutions ofCuCl2·2H2O (2 mmol) and potassium tricyanomethanide(8 mmol). Slow evaporation gave prismatic blue crystals of[Cu7(OH)6Cl2(pn)6(H2O)2](tcm)4Cl2 (yield 1.28 g, 42%) suita-ble for crystallography.‡ The structure of 1 is unique andconsists of a centrosymmetric hydroxo-bridged heptanuclearcopper(II) cation (Fig. 1) which can be described as twoCu4O3Cl distorted cubanes which share one copper cation(Cu1) (Fig. 1 and 2). The four crystallographically independentCu(II) centres differ markedly in their co-ordination geometry.The central atom (Cu1) presents a strongly elongated octahedralcoordination which involves a CuO4 equatorial plane withessentially equivalent Cu–O bonds [see Fig. 2(a)] and two semi-coordinated Cl anions in axial positions (Cu…Cl = 3.029(2)Å). The Cu2 and Cu3 cations have distorted square pyramidalCuO2N2Cl environments. In both cases, the basal planes areoccupied by two hydroxo bridging ligands (O1 and O3 for Cu2;O2 and O3 for Cu3) and two nitrogen atoms of the chelating pnligand (Cu–O range 1.977–2.016 Å and Cu–N range1.975–2.021 Å). Both pyramids share a strongly elongated axialposition filled by the bridging Cl1 atom (Cu2–Cl1 = 2.654(2)Å and Cu3–Cl1 = 2.679(2) Å) (Fig. 1). The co-ordination† Electronic supplementary information (ESI) available: detailed synthesisand X-ray crystallography of 1. See http://www.rsc.org/suppdata/cc/b1/b105231b/Fig. 2 (a) Schematic projection of the copper cluster including pertinent bond lengths and bond angles; (b) schematic representation of the magnetic couplingmodel in 1. Code of equivalent positions: (*) 1⁄2 2 x, 1⁄2 2 y, 1 2 z.Fig. 1 ORTEP of the heptanuclear cation in 1 showing atomic labellingscheme (30% probability ellipsoids). Shortest Cu…Cu distances (Å) andselected bond angles (°): Cu1–Cu2 3.3796(5), Cu1–Cu3 3.3719(5), Cu1–Cu4 3.1873(5), Cu2–Cu3 3.2829(8), Cu2–Cu4 3.1607(8), Cu3–Cu42.9610(8); O1–Cu1–O2 83.9(1), O1–Cu2–O3 84.5(1), O2–Cu3–O380.1(1), O1–Cu4–O2 72.0(1), O1–Cu4–O3 73.7(1), O2–Cu4–O3 79.5(1).Code of equivalent positions: (*) 1⁄2 2 x, 1⁄2 2 y, 1 2 z.This journal is © The Royal Society of Chemistry 20012172 Chem. Commun., 2001, 2172–2173 DOI: 10.1039/b105231bpolyhedron of the Cu4 cation can be described as aCu(N2O2)(O2) pseudo-octahedron generated by a CuN2O2plane arising from two nitrogen atoms of the chelating pn ligandand the two m3-hydroxo ligands (O2 and O3), and two axialpositions filled by the O1 hydroxo ligand and a water molecule(O4) (Cu…O4 = 2.524(4) Å). Note that the O1 hydroxo ligandmay be viewed as a m2-bridging group since it involves twoshort and one long Cu–O distances as clearly shown on Fig.2(a). Further examination of the structure shows that the tcmunits, which usually act as m2- or m3-bridging ligands, are hereuncoordinated; however, there are significant hydrogen bondsformed between their nitrogen atoms and the hydroxo-bridgingligands [N7(tcm)…O2 = 2.826(6) Å, O1–H…N7 = 167.3(3)°and N8(tcm)…O1 = 2.961(6) Å, O1–H…N7 = 160.6(2)°].Such intermolecular hydrogen bonds may contribute to thestabilisation of the cluster conformation.Magnetic susceptibility data for 1 were collected in thetemperature range 2–300 K, the cm and cmT product vs. T plotsare depicted in Fig. 3. From room temperature down to 25 K thecmT product decreases continuously and then reaches a plateauclose to 0.43 emu K mol21, which corresponds to an S = 1/2ground state. This behaviour is indicative of an overallantiferromagnetic coupling between the Cu(II) centres; this is inagreement with the strongly reduced magnetic moment at roomtemperature (cmT = 2.01 emu K mol21). Taking into accountthe cluster topology and connectivity (Fig. 2), it is possible todistinguish up to six different exchange pathways. However, inorder to avoid an overparameterization and in view of the Cu–O–Cu angles and connectivity of the OH bridges (m2-OH or m3-OH), these six exchange pathways have been grouped into threeaveraged different exchange parameters. The magnetic datahave been analysed with the following spin Hamiltonian:Hˆ = 22J1(Sˆ1Sˆ2 + Sˆ1Sˆ5) 2 2J2(Sˆ3Sˆ4 + Sˆ6Sˆ7)22J3(Sˆ1Sˆ3 + Sˆ1Sˆ4 + Sˆ2Sˆ3 + Sˆ2Sˆ4 + Sˆ1Sˆ6 + Sˆ1Sˆ7 + Sˆ5Sˆ6 + Sˆ5Sˆ7)Calculations have been performed with the magnetism packageMAGPACK.6 The best fit obtained from a least-squaresanalysis of the cmT is J1 = 2188.4 cm21, J2 = 252.6 cm21,J3 = 210.8 cm21 and g = 2.15 (R = S [((cmT)obs2 2(cmT)calc2)/(cmT)obs2] = 7.8 3 1023). Attempts to fit with onlyone or two averaged exchange parameters failed. As expectedfrom the structural parameters depicted in Fig. 2(a) (Cu–Odistances and Cu–O–Cu angles), the results show the presenceof two weak antiferromagnetic interactions (J2 and J3) asso-ciated to the interactions by m3-OH as have been observed inprevious cubane-type systems2,3 and a strong one (J1) corre-sponding to the exchange interaction between the two Cuconnected by O1 that has a main component of m2-OH and alarge Cu–O–Cu angle (117.6°).This work was supported by CNRS (Centre National de laRecherche Scientifique, UMR 6521), the University of Brest(SUCRI 2E). F. T. thanks the ‘Ministère de l'EducationNationale, de la Recherche et de la Technologie’ for apostgraduate grant.Notes and references‡ Anal. Calc. for C34H70Cl4Cu7N24O8: C, 26.7; H, 4.6; Cl, 9.3; Cu, 29.1; N,22.0. Found: C, 26.9; H, 4.6; Cl, 9.2; Cu, 29.2; N, 21.9%. IR data: n/cm21:3293m, 3247m, 2175s, 2168s, 1588m, 1195m, 1037w, 1023w, 900m,561m, 494m.Crystal data for 1. C34H70N24O8Cl4Cu7, M = 1529.68, monoclinic,space group C2/c (no. 15), a = 24.8994(3), b = 11.9801(2), c = 21.4298(3)Å, b = 112.14(6)°, U = 5920(2) Å3, Z = 4, Dc = 1.72 g cm23, m(Mo-Ka)= 2.72 mm21, T = 288 K, final R = 0.044, wR = 0.065 for 3924 observedreflections [I > 4s(I)] and 351 variables.CCDC reference number 165568. See http://www.rsc.org/suppdata/cc/b1/b105231b/ for crystallographic data in CIF or other electronic format.1 G. Kolks, S. J. Lippard, J. V. Waszczak and H. R. Lilienthal, J. Am.Chem. Soc., 1982, 104, 717; S. Teipel, K. Griesar, W. Haase and B.Krebs, Inorg. Chem., 1994, 33, 456; S. S. Tandon, L. K. Thompson andD. O. Miller, J. Chem. Soc., Chem. Commun., 1995, 1907; V. Tangoulis,C. P. Raptopoulou, S. Paschalidou, A. E. Tsohos, E. G. Bakalbassis, A.Terzis and S. P. Perleps, Inorg. Chem., 1997, 36, 5270.2 J. W. Hall, W. E. Estes, E. D. Estes, R. P. Scaringe and W. E. Hatfield,Inorg. Chem., 1977, 16, 1572; L. Walz, H. Paulus, W. Haase, H. Langhofand F. Nepveu, J. Chem. Soc., Dalton Trans., 1983, 657; J. Sletten, A.Sørensen, M. Julve and Y. Journaux, Inorg. Chem., 1990, 29, 5054; L. P.Wu, T. Kuroda-Sowa, M. Maekawa, Y. Suenaga and M. Munakata,J. Chem. Soc., Dalton Trans., 1996, 2179; X. S. Tan, Y. Fujii, R. Nukada,M. Mikuriya and Y. Nakano, J. Chem. Soc., Dalton Trans., 1999,2415.3 H. Muhonen, W. E. Hatfield and J. H. Helms, Inorg. Chem., 1986, 25,800; V. Tangoulis, S. Paschalidou, E. G. Bakalbassis, S. P. Perlepes, C. P.Raptopoulou and A. Terzis, Chem. Commun., 1996, 1297.4 V. Tangoulis, C. P. Raptopoulou, S. Paschalidou, E. G. Bakalbassis, S. P.Perleps and A. Terzis, Angew. Chem., Int. Ed. Engl., 1997, 36, 1083.5 J. A. Real, G. D. Munno, R. Chiappetta, M. Julve, F. Lloret, Y. Journaux,J.-C. Colin and G. Blondin, Angew. Chem., Int. Ed. Engl., 1994, 33,1184.6 J. J. Borrás-Almenar, J. M. Clemente-Juan, E. Coronado and B.Tsukerblat, Inorg. Chem., 1999, 38, 6081; J. J. Borrás-Almenar, J. M.Clemente-Juan, E. Coronado and B. Tsukerblat, J. Comput. Chem., 2001,22, 985.Fig. 3 Plots of molar susceptibility cm vs. T (the inset shows the cmT productvs. T) for 1 measured in a field of 1 T. The solid line was calculated usingthe magnetic coupling model (see text).Chem. Commun., 2001, 2172–2173 2173

Heptanuclear hydroxo-bridged copper cluster of the dicubane-like type: structural and magnetic characterisations of [Cu7(OH)6Cl2(pn)6(H2O)2](C(CN)3)4Cl2 (pn = 1,3-diaminopropane)

Heptanuclear hydroxo-bridged copper cluster of the dicubane-like type: structural and magnetic characterisations of [Cu7(OH)6Cl2(pn)6(H2O)2](C(CN)3)4Cl2 (pn = 1,3-diaminopropane)

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Repositori d'Objectes Digitals per a l'Ensenyament la Recerca i la Cultura