Bidentate enaminolate-based indium complexes as volatile precursors for atomic layer deposition

A new series of heteroleptic indium precursors—[In(Me)₂(dmadmb)]₂ (1), [In(Me)₂(deadmb)]₂ (2), and [In(Me)₂(emadmb)]₂ (3)—was synthesized by introducing enaminolate ligands, namely dmadmb (1-(dimethylamino)-3,3-dimethylbutan-2-one), deadmb (1-(diethylamino)-3,3-dimethylbutan-2-one), and emadmb (1-(ethyl(methyl)amino)-3,3-dimethylbutan-2-one), into InMe₂Cl. The molecular structures of the synthesized indium complexes 1, 2, and 3 were confirmed by single-crystal X-ray diffraction analysis (SC-XRD), which revealed that all indium complexes adopted dimeric structures featuring distorted trigonal bipyramidal coordination geometries. Thermogravimetric analysis (TGA) demonstrated that all three complexes exhibited single-step weight loss, leaving non-volatile residues of 24 % (1), 30 % (2), and 20 % (3) up to 500 °C. Furthermore, the sublimation temperatures of complexes 1–3 were observed to range from 30 to 35 °C under a reduced pressure of 0.65 Torr. These thermal behaviors and volatility characteristics indicate that complexes 1–3 are promising candidates as precursors for atomic layer deposition (ALD) processes.