Preparation and characterization of volatile alkaline-earth metal complexes with multiply coordinated aminoalkoxide ligands

Abstract

The aminoalkoxide complexes Sr(amak)₂ (1) and Ba(amak)₂ (2) were prepared by treatment of a multiply-chelating fluorinated aminoalcohol ligand HOC(CF₃)₂CH₂N(CH₂CH₂OMe)₂, (amak)H, with the Group 2 metal reagents Sr(OPrⁱ)₂ and BaH₂ respectively. Single crystal X-ray diffraction studies indicate that complex 1 possesses an 8-coordinate distorted bicapped octahedral geometry with all O and N atoms coordinated to the central Sr cation. However, complex 2 adopts a unique 10-coordinate bicapped square antiprismatic structure, of which the coordination number is increased by two fluorine-to-barium dative interactions. Variable temperature ¹⁹F NMR studies show the existence of two inter-convertible isomers in solution and their possible molecular structures are proposed according to their structures in the solid-state. Preliminary investigation suggests that these complexes are good CVD source reagents for depositing SrF₂ and BaF₂ thin films.