Ionic or covalent? Can some first hints be derived from the solid state structures of alkaline earth metal halide adducts?

Abstract

Even though the alkaline earth metal iodides are known to behave ionically in water, their bonding situation is not that clear in THF where they behave more like the MX₂ molecules known from the gas phase. Some alkaline earth metal iodide adducts, i.e. [MI₂(thf)₅] (M = Sr and Ba), [CaI₂(L)₄] (L = thf, H₂O), [Ba(OH)I(H₂O)₄] and [CaI₂(dme)(diglyme)] (dme = dimethoxyethane; diglyme = diethylene glycol dimethyl ether) are presented in this context and their bonding situation is discussed.