Synthesis and structural characterisation of the heavier alkaline earth 2,6-di-iso-propylphenolate complexes

Abstract

Redox transmetallation ligand exchange reactions involving a heavy alkaline earth metal, bis(pentafluorophenyl)mercury and 2,6-di-iso-propylphenol (HOdipp) in dme (1,2-dimethoxyethane) afforded alkaline earth aryloxo complexes which were structurally characterised. All complexes obtained were mononuclear, but the ionic radius of the alkaline earth metal was found to influence the number, and binding mode, of ligated dme molecules. Using Ca metal in the reaction afforded [Ca(Odipp)₂(dme)₂] 1 containing a six coordinate Ca metal atom and the phenolate ligands oriented in a cisoidal arrangement. Using Sr metal in the reaction yielded {3[Sr(Odipp)₂(dme)₂]·[Sr(Odipp)₂(dme)₃]} 2 containing both six and seven coordinate Sr metal atoms. The six coordinate species [Sr(Odipp)₂(dme)₂] contains phenolate ligands positioned in a cisoidal geometry. The seven coordinate species [Sr(Odipp)₂(dme)₃] contains a unidentate dme ligand, a rare binding mode for dme in alkaline earth chemistry. Using Ba metal in the reaction afforded [Ba(Odipp)₂(dme)₃] 3, which contains an eight coordinate Ba metal atom.