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Z. Naturforsch. 2012, 67b, 759 – 764
doi:10.5560/ZNB.2012-0163
Synthesis, Structure Determination, and Magnetic Properties of [Cr3(dpa)4Cl2][CuCl2], a Compound Comprising a Trinuclear Chain Cation
Dilahan Aydin-Cantürk and Hanne Nuss
Max-Planck-Institut für Festkörperforschung, Heisenbergstraße 1, 70569 Stuttgart, Germany
Reprint requests to H. Nuss. Fax: +49-711-689-1502. E-mail: h.nuss@fkf.mpg.de
Received June 14, 2012 / published online August 20, 2012
The new compound [Cr3(dpa)4Cl2][CuCl2] (1) (dpa = di-2,2′-pyridylamido) was synthesized by reacting Cr2(dpa)4 and anhydrous CuCl2 in dry tetrahydrofuran. Partial oxidation of Cr2(dpa)4 by Cu(II) forms Cr3+ ions, which coordinate to the free N donor atoms of the dpa ligands, and led to the formation of a trinuclear chain cation [Cr3(dpa)4Cl2]+. Recrystallization from CH2Cl2/ethyl ether yielded dark-brown, block-shaped crystals suitable for X-ray structure determination (Pccn (no. 56), a = 1246.8(5), b = 1487.3(3), c = 2184.8(1) pm, V = 4051.6(8) · 106 pm3, Z = 4). The crystal structure is composed of discrete [Cr3(dpa)4Cl2]+ cations and [CuCl2] anions. The Cr3 chain comprises quadruply-bonded diamagnetic (Cr2)4+ dimers and a pseudo-octahedrally coordinated, paramagnetic Cr3+ ion, manifesting itself in the effective magnetic moment μeff of 3.54μB (d3, S = 3/2) and the almost ideal Curie-paramagnetic behavior observed between 2 and 300 K with a Weiss constant θ =− 0.25(4) K and χ0 = 4.9(7) × 10−4 emu mol−1.
Key words: Trinuclear Chromium Complexes, Dichlorocuprate(I) Anion, Extended Metal Atom Chains, Magnetic Properties, Multiple Bonds, Mixed Valence
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