Volatile (beta)-Ketoiminato- and (beta)-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 (beta)-diketimine or, alternatively, Schiff Base compounds. Reaction of 2 equiv of the bidentate (beta)-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 (beta)-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-2one, 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((beta)ketoiminato)- and tetrakis((beta)-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.