Synthesis and Thermolysis of Aluminum Amidinates:  A Ligand-Exchange Route for New Mixed-Ligand Systems

A novel ligand-exchange route for the synthesis of amidinate-containing compounds of aluminum is explored. Syntheses of three new compounds, MeC(NⁱPr)₂AlEt₂ (4), EtC(NⁱPr)₂AlMe₂ (5), and (Me₂NC(NⁱPr)₂)₂AlH (6), are presented. These mixed-ligand compounds are difficult to make in high yields by the more traditional routes of carbodiimide insertion or salt metathesis. The thermal reactivities of these compounds and their parent homoleptic compounds [MeC(NⁱPr)₂]₃Al (1), [Me₂NC(NⁱPr)₂]₃Al (2), and [EtC(NⁱPr)₂]₃Al (3) are explored in detail and analyzed with respect to their utility as potential atomic-layer-deposition precursors for aluminum-containing films. The major mechanism of thermal decomposition is found to be carbodiimide deinsertion to form aluminum alkyls or amides. Because of their thermal characteristics, both compounds 3 and 5 hold promise for use as precursors.