Geometries and Relative Stabilities of AlN Four-Membered-Ring Compound Isomers: Ab initio Study

摘要

Using ab initio method, we have studied the structural stabilities, the electronic structures and properties between the two isomers with C_2h and C_2ロ symmetry of AlN four-membered-ring single precursors [Me₂AlNHR]₂ (R = Me, iPr, and tBu). In the viewpoint of bond lengths in optimized structures, the N-C bonds are considerably affected by the change of the R groups bonded to nitrogen, but the bonding characters of the Al-N and Al-C bonds are little affected. Also the structural stabilities between the two isomers with C_2h and C_2ロ symmetry by using Hartree-Fock (HF) and the second order Moeller-Pleset (MP2) calculations agree well with the experimental results for the relative stability of bis(dimethyl- m-isopropylamido-aluminum) (BDPA) and bis(dimethyl- m-t-butylamido-aluminum) (BDBA), while the semiempirical AM1 and PM3 calculations for BDPA were reverse. Thus, our results may aid in designing an optimum precursor for a given process by explaining the experimental results through the elimination of the R groups bonded to nitrogen.