BIMETALLIC ALKOXIDES OF ALUMINUM-HAFNIUM AND ALUMINUM-ZIRCONIUM - X-RAY STRUCTURE OF AL2HF(OPRI)(10)

The solubility studies in the Al(OR)(3)-M(OR)(4) . ROH-ROH (R = Pr-i) systems at 20 degrees C revealed the existence of the only complex, Al (2)M(OR)(10), [M = Hf(I), Zr(II)]. The literature data on the existenc e of the AlM(OR)(7) species were disproved. According to the results o f the single crystal X-ray diffraction study of I, its molecule has a two-fold symmetry axis and involves two peripheral tetrahedrally coord inated Al atoms, each of their coordination tetrahedra sharing one com mon edge with the coordination octahedron of the central Hf atom, [(RO )(2)Al(mu-OR)(2)]Hf-2(OR)(2). The mean planes of almost planar [AlO2Hf ] cycles form the dihedral angle of 82 degrees with each other. Mass-s pectra of I and II show two fragmentation pathways, viz.: (1) the elim ination of the ether molecule accompanied by the formation of oxo grou ps, and (2) the Al(OR), molecule abstraction producing the AlM(OR)(6)( +) ions. According to the X-ray powder diffraction data crystals of I and II are isostructural. The influence of the oligomeric Zr and Hf ox oalkoxides, formed as a result of partial thermolysis of M(OR)(4) . RO H, on the processes of formation of complexes with Al(OR)(3) has been elucidated. The non-crystalline solid Al2Hf(OEt)(10) was isolated from ethanol solution, its mass-spectral fragmentation being analogous to that of I and II. Copyright (C) 1996 Elsevier Science Ltd