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

Abstract

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(NR(2))(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-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(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(NMe(2))(4). The stability order turned out to be 1 > 5 >> Zr(NMe(2))(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.

Coordination modes in zirconium β-diketiminate complexes

“…Despite the boat-like distortion of the ligand in 2a, its bonding mode is essentially a j 2 -, in-plane coordination. Similar coordination modes have been observed for nacnac dipp ZrCl 3 (dipp = 2,6-diisopropylphenyl) [5] and other diketiminato zirconium complexes [3][4][5][6][7]9]. Despite the unsaturation of the zirconium center, nacnac dipp ZrCl 3 displays a long, non-coordinative distance of 3.4 Å between Zr and the C3 atom of the carbon back-bone.…”

“…In mono- [2][3][4][5][6][7][8][9] and bis(diketiminate) complexes of zirconium [4,6,7,10], as well as in complexes with the related iminomethylaniline [11,12] or azaallylpyridine ligands [13,14], the ligand is bound via the two nitrogen lone pairs with the metal found in the ligand mean plane (Scheme 1, A). Steric crowding around the metal center, in particular with sterically demanding substituents on nitrogen, results in a displacement of the metal out of the ligand mean plane (Scheme 1, B) [1,3].…”

Dichlorido-[N,N′-bis(2,6-dimethylphenyl)pentane-2,4-diiminato](indenyl)zirconium(IV) toluene hemisolvate

“…For comparable coordination of the nacnac ligand in five-coordinated complexes, see Basuli et al (2004) [Cambridge Structural Database (Allen, 2002) refcodes FAPBUU, FAPCAP, FAPCEF and FABCIJ]. For Zr complexes containing 2 -coordinated nacnac, see: Kakaliou et al (1999); Qian et al (1999); Jin & Novak (2000); Franceschini et al (2003); Hamaki et al (2006). For Zr complexes containing 5 -like coordinated nacnac, see: Rahim et al (1998); Vollmerhaus et al (2000).…”

Recent Advances in Chemical Vapor Deposition

“…, the N-methyl analog is unstable at room temperature [46]. This structural anomaly is rationalized by in situ rearrangement of the N-hydrogen substituted compound to form the thermally stable 8-coordinate homoleptic β-ketoiminate (IV').…”