Influence of the steric demand of the 2,4,6-trialkylphenyl substituents on the structures and reactivity of diarylzinc

The Grignard reaction of 2,4,6-tri(tert-butyl)phenylmagnesium bromide with zinc dichloride in THF yields monomeric bis[2,4,6-tri(tert-butyl)phenyl]zinc (1). Due to the steric demand of the tert-butyl groups 1 has a bent CZnC moiety and the boat-shaped aryl groups are in a staggered conformation. After the transmetallation of 1 with cesium in a solvent mixture of 1,2-dimethoxyethane (DME) and toluene (1,2-dimethoxyethane-O,O′)cesium [2,4,6-tri(tert-butyl) phenolate] (2) is isolated. A polymeric structure is formed in the crystalline state by linkage of these molecules via a Cs-O bond of the phenolate oxygen atoms and a η⁶-coordination of the aryl moiety of another molecule to the cesium cations. Furthermore, in the solid state the cesium cation completes his coordination sphere by bonds to a bidentate ether molecule and by close contacts to a tert-butyl group of a neighboring molecule.