Gallium and Indium β-Diketonate Complexes: AACVD of [In(thd)3] and the Attempted Synthesis of Gallium and Indium Bis(β-diketonates)

Aerosol-assisted chemical vapour deposition (AACVD) of a suspension of [In(thd)(3)] (thd = 2,2,6,6-tetramethylheptane-3,5-dionate) in CH2Cl2 at 450 degrees C afforded thin crystalline films of indium oxide. The films were analyzed by scanning electron microscopy (SEM), glancing angle X-ray diffraction (XRD) and energy dispersive analysis of X-rays (EDX). Efforts to grow thicker films were hampered by the poor solubility of [In(thd)(3)], so the synthesis of heteroleptic compounds of the type [M(bdk)(2)X] (M = Ga, In; bdk = beta-diketonate; X = chloride, hydride, methyl) was attempted such that the solubility could be improved by tuning the ligands surrounding the metal centre. Reaction of stoichiometric amounts of beta-diketones [Hthd and 2,4-pentanedione (acetylacetone, Hacac)] with Lewis base-stabilized adducts of GaH3 resulted only in the isolation of the homoleptic gallium tris(beta-diketonate) compounds [Ga(bdk)(3)], instead of the expected heteroleptic gallium bis(beta-diketonate) hydride, [GaH(bdk)(2)]. An unexpected reduction of Hthd to 2,2,6,6-tetramethylheptane-3,5-diol was also observed. Other attempted syntheses of gallium bis(beta-diketonate) compounds also resulted in the isolation of homoleptic [Ga(bdk)(3)] complexes and similar results were obtained for indium. The compounds were characterised by H-1 NMR spectroscopy, mass spectrometry and elemental analysis and the structures of [In(thd)(3)] and 2,2,6,6-tetramethylheptane-3,5-diol were determined by X-ray crystallography.