Reactivity and Structural and Physical Studies of Tetranuclear Iron(III) Clusters Containing the [Fe 4 (μ 3 -O) 2 ] 8+ “Butterfly” Core: an Fe III 4 Cluster with an S ) 1 Ground State Theocharis C. Stamatatos, ² Athanassios K. Boudalis, ‡ Yiannis Sanakis, ‡ and Catherine P. Raptopoulou* ,‡ Department of Chemistry, UniVersity of Patras, 26504 Patras, Greece, and Institute of Materials Science, NCSR “Demokritos”, 15310 Aghia ParaskeVi, Athens, Greece Received March 22, 2006 The initial use of di-2-pyridyl ketone oxime [(py) 2 CNOH] in iron(III) carboxylate chemistry has yielded the tetranuclear complex [Fe 4 O 2 Cl 2 (O 2 CMe) 2 {(py) 2 CNO} 4 ](1). Compound 1 can be synthesized either by the 1:2:1 molar ratio reaction between Fe III , MeCO 2 - , and (py) 2 CNOH (complex 1a) or by the 1:3 molar ratio reaction between [Fe 3 O(O 2 - CMe) 6 (H 2 O) 3 ]Cl and (py) 2 CNOH (complex 1b). The presence of N 3 - in both reaction mixtures has afforded the tetranuclear complex [Fe 4 O 2 (N 3 ) 2 (O 2 CMe) 2 {(py) 2 CNO} 4 ](2), which can be alternatively synthesized by the reaction of 1 with N 3 - . Compound 1a crystallizes in the tetragonal space group I4 h with (at 25 °C) a ) 35.06(2) Å, b ) 35.06(2) Å, c ) 13.255(6) Å, V ) 16293(2) Å 3 , and Z ) 8. Compound 1b crystallizes in the monoclinic space group P2 1 /c with (at 25 °C) a ) 22.577(7) Å, b ) 17.078(6) Å, c ) 17.394(6) Å,  ) 93.50(1)°, V ) 6694(4) Å 3 , and Z ) 4. Compound 2 crystallizes in the triclinic space group P1 h with (at 25 °C) a ) 13.658(9) Å, b ) 15.815(9) Å, c ) 17.29(1) Å, R) 97.08(3)°,  ) 98.55(3)°, γ ) 112.12(3)°, V ) 3355(4) Å 3 , and Z ) 2. The structures of 1 and 2 contain the [Fe 4 (µ 3 -O) 2 ] 8+ core comprising four Fe III ions in a “butterfly” disposition and two µ 3 -O 2- ions, each bridging three Fe III ions forming the “wings” of the “butterfly”. The Mo ¨ ssbauer spectra of 1b and 2 consist of composite quadrupole-split doublets, with parameters typical for high-spin Fe III in octahedral environments. Magnetic susceptibility measurements on 1a revealed antiferromagnetic interactions between the S ) 5 / 2 ferric ions, with best-fit parameters being J wb ) -40.2 cm -1 and J bb ) -59.4 cm -1 (H ) -2∑J i J j ) for wingtip-body and body- body interactions, respectively, yielding an S ) 1 ground state. Both wingtip-body and body-body interactions are well determined. Introduction Technological applications nowadays are driven by the demand of miniaturization of devices, down to the molecular level. In order for this to happen, a breakthrough has to take place and new chemical species of nanometer size have to be synthesized to replace existing materials. Polynuclear metal complexes (clusters) have been proposed as potential materials for technological applications 1 because of their interesting properties (magnetic, 2 electronic, 3 optical, 4 cata- lytic, 5 etc.). Therefore, the biggest challenge for chemists today is the development of new nanometer-size molecular * To whom correspondence should be addressed. E-mail: craptop@ ims.demokritos.gr. Tel: +3210-6503365. Fax: +3210-6519430. ² University of Patras. ‡ NCSR “Demokritos”. (1) (a) Leuenberger, M. N.; Loss, D. Nature 2001, 410, 789. (b) Cavallini, M.; Gomez-Segura, J.; Ruiz-Molina, D.; Massi, M.; Albonetti, C.; Rovira, C.; Veciana, J.; Biscarini, F. Angew. Chem., Int. Ed. 2005, 44, 888. (2) For recent examples involving Mn and Fe complexes, see: (a) Tasiopoulos, A. J.; Vinslava, A.; Wernsdorfer, W.; Abboud, K. A.; Christou, G. Angew. Chem., Int. Ed. 2004, 43, 2117. (b) Soler, M.; Wernsdorfer, W.; Folting, K.; Pink, M.; Christou, G. J. Am. Chem. Soc. 2004, 126, 2156. (c) Aliaga-Alcalde, N.; Edwards, R. S.; Hill, S. O.; Wernsdorfer, W.; Folting, K.; Christou, G. J. Am. Chem. Soc. 2004, 126, 12503. (d) Wang, S.; Zuo, J.-L.; Zhou, H.-C.; Choi, H. J.; Ke, Y.; Long, J. R.; You, X.-Z. Angew. Chem., Int. Ed. 2004, 43, 5940. (e) Oshio, H.; Hoshino, N.; Ito, T.; Nakano, M. J. Am. Chem. Soc. 2004, 126, 8805. (3) (a) Yu, G.; Yin, S.; Liu, Y.; Shuai, Z.; Zhu, D. J. Am. Chem. Soc. 2003, 125, 14816. (b) Bordiga, S.; Lamberti, C.; Ricchiardi, G.; Regli, L.; Bonino, F.; Damin, A.; Lillerud, K.-P.; Bjorgen, M.; Zecchina, A. Chem. Commun. 2004, 2300. (c) Shi, J.-M.; Xu, W.; Liu, Q,-V.; Liu, F.-I.; Huang, Z.-I.; Lei, H.; Yu, W.-T.; Fang, Q. Chem. Commun. 2002, 756. (d) Coronado, E.; Clemente-Leo ´n, M.; Gala ´n-Mascaro ´s, J. R.; Gime ´nez-Saiz, C.; Go ´mez-Garcı ´a, C. J.; Martı ´nez-Ferrero, E. J. Chem. Soc., Dalton Trans. 2000, 3955. Inorg. Chem. 2006, 45, 7372-7381 7372 Inorganic Chemistry, Vol. 45, No. 18, 2006 10.1021/ic0604821 CCC: $33.50 © 2006 American Chemical Society Published on Web 08/08/2006