Volatile β-Ketoiminato- and β-Diketiminato-Based Zirconium Complexes as Potential MOCVD Precursors

An amine elimination pathway has been used to produce a number of homo- and heteroleptic zirconium complexes,
starting from tetrakis(dialkylamido)zirconium complexes and β-diketimine or, alternatively, Schiff Base compounds.
Reaction of 2 equiv of the bidentate β-diketimine (2Z,4E)-N-methyl-4-(methylimino)pent-2-en-2-amine with Zr(NR2)4
(R = Me, Et) affords the six-coordinate heteroleptic compounds bis(N-methyl-4-(methylimino)pent-2-en-2-amido)bis(dialkylamido)zirconium 1 (alkyl = Me) and 2 (alkyl = Et). The dynamic behavior of these two compounds in
solution has been investigated. Reaction with the isopropyl-substituted β-diketimine (2Z)-N-isopropyl-4-(isopropylimino)pent-2-en-2-amine gives the five-coordinate mono(diketiminato)-substituted compound (N-isopropyl-4-(isoropylimino)pent-2-en-2-amido)tris(dimethylamido )zirconium, 3. With employment of the Schiff base (3Z)-4-(methylamino)pent-3-en-2-one, it was also possible to prepare the six-coordinate bis(4-(methylamino)pent-3-en-2-onato)bis(diethylamido)zirconium compound 4. When the bidentate ligand bearing hydrogen as substituent on the imino-nitrogen
atom was employed, homoleptic tetrakis(β-ketoiminato)- and tetrakis(β-diketiminato)zirconium compounds 5 and 6
can be obtained. Complexes 1 and 5 have been tested for their air stability with reference to Zr(NMe2)4. The
stability order turned out to be 1 > 5 ≫ Zr(NMe2)4. The thermal properties and volatility of all the compounds are
discussed in view of their potential application in metal−organic chemical vapor deposition processes (MOCVD) of
zirconium nitride.