A chelating β-diketonate/phenoxide ligand and its coordination behavior toward titanium and scandium

Abstract

Dibenzoylmethane derivatives with one (L¹H₂) or both (L²H₃, L³H₃) benzenes linked at their ortho positions to 4,6-di-tert-butylphenol moieties by two-carbon linkers have been synthesized. The mono-β-diketone-monophenol ligand L¹H₂ is metalated by titanium alkoxides to form the homoleptic complex (L¹)₂Ti and heteroleptic complexes (L¹)Ti([OCH₂CH₂]₂NR) (R = H, CH₃), and reacts with Cp₃Sc to form CpSc(L¹). These are the first examples of complexes of a β-diketonate ligand which is further chelating to a single metal center. Crystallographic analysis of (L¹)₂Ti indicates that the 10-membered ring allows chelation of the phenoxide with little strain, and both fac and mer geometries are accessible in solution. Protonolysis of the second cyclopentadienyl ring of Cp₃Sc appears to take place by an indirect, Cp₃Sc-catalyzed pathway.