Conformational study of [Cu(CF3COCHCO(C4H3X))2] (X = O or S), a combined experimental and DFT study

Abstract

To date, only the trans isomers of [Cu(β-diketonato)2] complexes are isolated in the solid state. Both experimental solid state structures and density functional theory (DFT) calculations show that for [Cu(CF3COCHCO(C4H3X))2] complexes, the trans-2 conformer with X pointing towards the methine H of the β-diketonato ligand is obtained when X = O (complex 1). However, for X = S (complex 2), the trans-1 conformer with X pointing away from the methine H of the β-diketonato ligand, as well as the trans-2 conformer are possible, with trans-1 as the main conformer. A natural bond orbital (NBO) study provided new insights into the preferred orientation of the C4H3X group with respect to both the Cu(II) central atom and the β-diketonato ligand in [Cu(CF3COCHCO(C4H3X))2] complexes.