Crystal structure and magnetic properties of bis{di-µ-ethoxo-bis[4,4,4-trifluoro-1-(2-thienyl)butane-1,3-dionato]dicopper(II)}

Abstract

The crystal and molecular structure of the title compound has been determined by a single-crystal X-ray diffraction study. The compound crystallizes in the space group Fddd of the orthorhombic system with eight tetrameric molecules in a cell of dimensions a= 14.071(5), b= 14.294(9), and c= 49.93(3)Å. The structure has been refined to an R value of 0.076 for 1 354 independent reflections. The structure consists of D2 symmetry tetranuclear molecules in which copper ions are linked by triply bridging OEt groups. The Cu4O4 core formed by copper atoms and ethoxy-oxygen atoms has a cubane-like structure: the Cu ⋯ Cu separations are 2.977(2), 3.260(2), and 3.281 (2)Å, while the Cu–O bond lengths are 1.945(6), 1.947(6), and 2.411(7)Å the Cu–O–Cu bridging angles are 99.8(3), 97.1 (3), and 96.3(2)°. The co-ordination around each copper centre is roughly square-pyramidal. Magnetic susceptibility data (80–300 K) are interpreted in terms of the Heisenberg–Dirac–Van Vleck model. Substantial antiferromagnetic interactions (2J=–352 cm–1) are found between copper ions in the roughly planar dimeric fragments of the tetranuclear molecule, and small interactions (2J=–10 cm–1) between these fragments.