Lewis acidity of a high-valent copper(iii) acetylacetonate.

The Lewis acidity of the stable high-valent copper complex (acac)CuIII(CF3)2 was studied using experimental and computational methods. Pentacoordinated adducts formed via the addition of monodentate Lewis bases (Py, iPrNH2, MeCN, DMF, and Et3PO) were characterized, including using X-ray crystallography. Addition of a primary amine alters the acetylacetonate coordination. Coordination of a square-planar Cu(iii) complex with various N- and O-based ligands weakens the covalent Cu-C bonding, as revealed by NBO studies. The quantitative Lewis acidity of this compound was studied using experimental methods (Gutmann-Beckett) and DFT calculations of the fluoride ion affinity (FIA). The acidity was compared with those of copper(ii) and copper(i) acetylacetonates, which indicated a stepwise increase in Lewis acidity with the formal oxidation state of copper.