Preparation and characterization of some volatile double isopropoxides of aluminum with alkaline earth metals

Abstract

Reactions of the alkaline earth metal (Mg, Ca, Sr, Ba) with aluminum isopropoxide in boiling isopropanol in the presence of a mercuric chloride catalyst give the corresponding double alkoxides [M[Al(OPrⁱ)₄]₂]_n (n = 1, M =Mg; N = 2, N = Ca, Sr, and Ba) which can be isolated by vacuum distillation or sublimation. Treatment of these double alkoxides with excess of the teritary alcohols tert-butyl alcohol or term-amyl alcohol in boiling benzene results in partial alcoholysis of the isopropoxy groups to give M[Al(OPrⁱ)(OR)₃]₂ (M = Mg, Ca, and Sr) or Ba[Al(OPrⁱ)₂(OR)₂]₂ (R = tert--butyl and tert--amyl ) which are volatile and monomeric. Proton and carbon-13 n.m.r. spectra of some of these double isopropoxides suggest rapid interchange of bridging and terminal isopropoxy groups.