A Single Source CVD Precursor to MgAl2O4: [Mg{(Ot-Bu)2AlH2}2]

The hydride-modified heterometal alkoxide [Mg{(Ot-Bu)2AlH2}2] (1), a precursor with tailored composition for single-source chemical vapor deposition (CVD) synthesis of MgAl2O4, has been synthesized and characterized using spectroscopic meth- ods and single-crystal X-ray diffraction analysis. Thermal decomposition of 1, in a CVD process, on an inductively heated (45°C) metal substrate (steel, Ni, Cu) gave crystalline deposits of high purity MgAl2O4 with low carbon contamination (<0.5%) and nano-sized crystallites (<010 nm). Analysis of the pyrolysis gases using on-line mass spectroscopy, and comparing the results obtained with the deuterated compound [Mg{(Ot-Bu)2AlD2}2] (2), confirmed the gaseous products to be isobu- tylene (2-methylpropene) and dihydrogen (HD in the case of 2). The 27Al magic angle spinning (MAS) NMR study of the ob- tained spinel shows a partly inverse structure with Al3+ 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.