Crystal Structures of Tris(dimethylamido)(pentamethylcyclopentadienyl)zirconium(IV) (Cp*Zr(NMe ₂ ) ₃ ) and Its Temperature-Induced Order–Disorder Phase Transition Behavior

We describe the single-crystal X-ray structures of the highly air-sensitive atomic layer deposition (ALD) precursor tris(dimethylamido)(pentamethylcyclopentadienyl)zirconium(IV) (Cp*Zr(NMe2)3). The crystals of Cp*Zr(NMe2)3 undergo a phase transition between −80 and −173 °C. At −80 °C, Cp*Zr(NMe2)3 crystallizes in the space group Cmce with 3/4 molecules in an asymmetric unit; at −173 °C, the thermal motions become frozen, and the structure can be solved instead in the space group Pbcm with 3/2 molecules in the asymmetric unit. Structural refinements for both crystals were complicated by heavily disordered molecules, which were resolved by a comparative study between the high- and low-temperature structural models. Reliable bond distances and angles for Cp*Zr(NMe2)3 were subsequently obtained. The structural information obtained for Cp*Zr(NMe2)3 serves as important benchmark data for the study of the analogue liquid ALD precursor CpZr(NMe2)3, which currently plays a critical role in microelectronics industries.