The crystal structures obtained by X-ray methods of (tertbutoxy)alane and -gallane (tBuOMH2) are isotypic and are composed of discrete centrosymmetric dimers. The dimers !rise from almost symmetrical Al-0-A1 [1.810(3), 1.815 (3) A] and Ga-0-Ga [1.902(9), 1.908(9) A] bridges forming a central rhombohedra1 four membered M202 cycle [ 0 -A l -0 81.0(2)', 0 -G a -0 ?8.6(5)'] with the metallic atoms in a distorted tetrahedral environment. When one of the hydride ligands on the metals is further substituted by tert-butoxy, Very recently the synthesis and crystal structure determination of bis(tert-buty1)methoxyalane (tBu2HC-0-AlH2) and the corresponding gallane were described['? We have independently studied quite similar compounds. Our intention has been to "bridge" the structural gap between AlH3r21 and AI(O~BU), [~] with the missing mixed compounds, e.g. tBuOAlH, and (tBuO),AlH, and to examine the homologous gallium compounds. We were interested in the structures of these compounds because we had used them in CVD processes [4]. A profound synthetic work on the aluminium compounds has already been published in 1968 by Noth and Suchyf51, and some predictions of structures were made on the basis of IR spectroscopy and molecular weight determinations.The synthesis of the compounds tBuOMH, and (tBuO),MH (M = Al, Ga) was achieved by alcoholysis of diethyl ether solutions of alane and gallanef51 [equation (l)].The correct stoichiometry of the reaction is important for obtaining the desired products and the yields have been very satisfactory. The products were isolated by sublimation and crystallization. tBuOAIHz and tBuOGaHz show very simple NMR spectra in solution: in the 'H-NMR spectrum, the tert-butyl group exhibits a singlet, and in the 13C-NMR spectrum two lines for the pnmary and quaternary carbon atoms are detected. The 'H and I3C-NMR spectra of (tBuO),AlH and (tBuO),GaH are much more complex. In each case two sets of two signals of equal intensity were found that can be attributed to four chemically different tert-butyl groups. In the aluminium denvative, the ratio of the sets of signals is approximately 45:55, whereas it is 33:66 in the case of gallium derivative. We tentatively ascribed the four signals in the 'H-NMR spectra to a mixture of cis and trans isomers [cis and trans refer to the position of the hydrides with respect to the M202 central ring (see structure below)]. The trans isomer presumably leads to higher intensities. The chemical shifts of the signals change with the temperature of the formation of (tBuO),AlH and (tBu0) the NMR probe, but no changes of the intensities or a coalescence phenomenon have been All four compounds are dimeric in benzene, as found by cryoscopy.The data for the X-ray structure determination on single crystals of tBuOMH, and (tBuO),MH (M = Al, Ga) have been assembled in Table 1; the most important bond lengths and angles are summarized in Table 2t7]. As a result of the structure analyses, the molecule tBuOAIHz (tBuOGaH, is isotypic) has been depicted in Figure 1, and the mol...

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The hydride-modified heterometal alkoxide [Mg{(O t Bu) 2 AlH 2 } 2 ] (1), a precursor with tailored composition for single-source chemical vapor deposition (CVD) synthesis of MgAl 2 O 4 , has been synthesized and characterized using spectroscopic methods and single-crystal X-ray diffraction analysis. Thermal decomposition of 1, in a CVD process, on an inductively heated (450 C) metal substrate (steel, Ni, Cu) gave crystalline deposits of high purity MgAl 2 O 4 with low carbon contamination (<0.5 %) and nano-sized crystallites (<10 nm). Analysis of the pyrolysis gases using on-line mass spectroscopy, and comparing the results obtained with the deuterated compound [Mg{(O t Bu) 2 AlD 2 } 2 ] (2), confirmed the gaseous products to be isobutylene (2-methylpropene) and dihydrogen (HD in the case of 2). The 27 Al magic angle spinning (MAS) NMR study of the obtained spinel shows a partly inverse structure with Al 3+ ions occupying both octahedral and tetrahedral sites. This distribution (octahedral/tetrahedral) remains unaltered even on heat treatment. The thin layers obtained were characterized using glow discharge mass spectrometry (GDMS), energy dispersive X-ray (EDX), powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), solid-state NMR and C-H analysis.

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