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.