Synthesis of group 13 sesquialkoxides and their application as precursors to crystalline oxide films

The reaction of Me3Ga with an excess of 4-methylbenzyl alcohol (4-MeC6H4CH2OH) in toluene, under reflux conditions, resulted in the formation of the sesquialkoxide [Ga{MeGa(OCH2C6H4Me-4)(3)}(3)] (1). In contrast, reaction of Me3In with excess of 4-methylbenzyl alcohol (4-MeC6H4CH2OH) under the same conditions afforded another type of sesquialkoxide, [In{Me2In(OCH2C6H4Me-4)(2)}(3)] (2). Compounds 1 and 2 have been characterized by NMR, FTIR, and elemental analysis, and the structure of 1 was determined by X-ray crystallography. The structure of 1 consists of a central Ga3+ ion coordinated by three [MeGa(OCH2C6H4Me-4)(mu-OCH2C6H4Me-4)(2)](-) units such that it has a coordination number of six. The surrounding metal ions are four coordinate. H-1 NMR data for 1 indicate that in solution two isomers (1:1) are present, namely, the C-1- and C-3-symmetrical isomers, but in the solid state 1 exists as the C-3-symmetrical isomer. Compound 1 possesses the correct ratio of Ga:O atoms (2:3) for that found in gallium oxide (Ga2O3), and LPCVD of 1 afforded crystalline Ga2O3 films at 600 degrees C. These results are surprising, as Ga2O3 films are typically only crystalline above 700 degrees C.