Aluminum bromide ether adducts. Structures in solution and in the solid state
Article
Monoglyme forms a mol. 1:1 adduct with AlBr3 which dissocs. into the ions AlBr2(DME)2+ and AlBr4- in DME, CH2Br2, and CDCl3 as solvents. A hexacoordinated Al center is present in the solid adduct AlBr3.diglyme. The O and Br atoms are arranged in a meridional configuration as shown by x-ray crystallog. In soln. dissocn. occurs into AlBr2(diglyme)2+ and AlBr4-. Not unexpectedly, AlBr3 forms the adduct AlBr3.2THF with THF. The dioxane adduct AlBr3.diox is polymeric in the solid state and has a chain structure with pentacoordinated trigonal-bipyramidal Al centers. The Br atoms are arranged in a slightly distorted trigonal plane. In soln., the presence of tetracoordinated Al is indicated by 27Al NMR. AlBr3 cleaves one of the C-O bonds of 12-crown-4 leading to the dimer of w-bromo-tetra(ethyleneoxy)aluminum dibromide. This dimer contains pentacoordinated Al centers as proven by x-ray structure anal. The adduct of AlBr3 with 15-crown-5 is most likely an ionic compd., and is best described as [AlBr2(15-crown-5)]AlBr4 based on 27Al NMR and IR data. [on SciFinder (R)]