A tetranuclear hydroxo-bridged copper(II) complex with primary N-acylamidines as ligands:: Preparation, structural, and magnetic characterisation

The reaction of N-pivaloylbenzamidine (1a) and tetrakis(acetonitrile)copper(1) hexafluorophosphate in the presence of air yields a hydroxo-bridged copper(II) complex (4). The product was characterised by X-ray diffraction analysis and found to be a cubane-like dimeric complex consisting of two square dimers with the formula [{(1a)2Cu(2)(OH)(2)}(2)](PF6)(4)center dot 4CH(2)Cl(2) (4(.)4 CH2Cl2) with cupric ions and hydroxyl oxygen atoms at alternating vertices of a cube. The complex can be described as consisting of two [ligand-Cu-(OH)(2)-Cu-ligand] units held together by long out-of-plane Cu-O bonds, creating a tetrameric entity with a Cu-4(OH)4 core. Each cupric ion is essentially square-pyramidally coordinated, being bound to three OH bridges, one N atom of the amidine and one N-acylamidme 0 atom. The magnetic properties of this compound have been studied in the 2-300 K temperature range. The measurements revealed that the cupric ions in the cube are anti-ferromagnetically coupled. This observation has been rationalised on the basis of the structural data. (c) Wiley-VCH Verlag GmbH & Co.