Synthesis and Thermal Study of Hexacoordinated Aluminum(III) Triazenides for Use in Atomic Layer Deposition

Amidinate and guanidinate
ligands have been used extensively to
produce volatile and thermally stable precursors for atomic layer
deposition. The triazenide ligand is relatively unexplored as an alternative
ligand system. Herein, we present six new Al­(III) complexes bearing
three sets of a 1,3-dialkyltriazenide ligand. These complexes volatilize
quantitatively in a single step with onset volatilization temperatures
of ∼150 °C and 1 Torr vapor pressures of ∼134 °C.
Differential scanning calorimetry revealed that these Al­(III) complexes
exhibited exothermic events that overlapped with the temperatures
of their mass loss events in thermogravimetric analysis. Using quantum
chemical density functional theory computations, we found a decomposition
pathway that transforms the relatively large hexacoordinated Al­(III)
precursor into a smaller dicoordinated complex. The pathway relies
on previously unexplored interligand proton migrations. These new
Al­(III) triazenides provide a series of alternative precursors with
unique thermal properties that could be highly advantageous for vapor
deposition processes of Al containing materials.