TETRA-, PENTA- AND HEXACOORDINATED ALUMINIUM: NMR AND X-RAY DIFFRACTION STUDIES OF THE COMPLEXES OF ETHYLENEDIAMINE WITH ALUMINIUM ISOPROPOXIDE AND ITS FLUORO ANALOGUES

Abstract The products resulting from the complexation of Al[OCH(CH3)2]3 (A) and Al[OCH(CF2)3], with ethylenediamine have been studied. Four complexes en. Al[OCH(CH3)2]3 (B); en.Al[OCH(CF3)2]3 (D); [en]2. Al[OCH(CF3)2]3 (E) and en. Al(OH)[OCH(CF3)2]3 (F) were isolated and identified by elemental analysis and NMR spectroscopy. The occurence of a further complex (C) en. 2Al[OCH(CH3)2]3 in solution is suggested by the NMR data. A crystal structure determination is reported for the species (F). The structure consists of en.Al(OH)[OCH(CF3)2]2 dimers with characteristic (N2O4) ligand donor sets. The Al-Al distance (2.939 Å indicates that no metal-metal interaction occurs. For the other complexes, the NMR, and in particular the 27Al NMR, data are shown to be consistent with a tetracoordinated aluminium atom in an (O3N) environment (compounds B and D) or with a penta-coordinated aluminium in an (O4 N) environment (C) or in an (O3 N2) environment (E).

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