No abstract

The identification of appropriate ligand-metal combinations, which successfully present the features of : (i) having acceptable melting point, (ii) being more thermally stable than hafnium alkylamides, (iii) having sufficient volatility for vapor phase distribution and (iv) enabling the deposition by LI-MOCVD and ALD of hafnium containing thin films, should go through new generations of well-behaved molecular precursors. We report herein the chemical design and full characterizations of a portfolio of novel mono- and di- amidinate and guanidinate alkylamide hafnium complexes of N,N'-unsymmetrically substituted 1,3-amidinate and 1,3-guanidinate [R'-N=CX-NR"]xHf(NR2)4-x (R'≠ R" = Et, iPr, tBu ; R = Me or Et ; X = Me or NMe2 ; x = 1 or 2). We will exemplify the remarkable influence of the molecular structure on the melting point, the volatility and the thermal stability (see figure 1) and the nature (cubic, monoclinic) of HfO2 thin films by LI-MOCVD.

Key indicators: single-crystal X-ray study; T = 110 K; mean (C-C) = 0.002 Å; disorder in main residue; R factor = 0.041; wR factor = 0.105; data-to-parameter ratio = 19.5.The title compound, [Ca 3 (C 13 H 25 N 2 O) 6 ]ÁC 6 H 14 , is a trinuclear complex with all Ca atoms presenting octahedral coordination. The central Ca atom (as well as the hexane solvent molecule) is located on a crystallographic twofold rotation axis and is coordinated by six bridging O atoms, with Ca-O distances ranging from 2.344 (1) to 2.351 (1) Å . The terminal Ca atoms are coordinated by three bridging O atoms, with Ca-O distances ranging from 2.311 (1) to 2.335 (1) Å , and three N atoms of the -ketoiminate ligands, with Ca-N distances ranging from 2.432 (1) to 2.452 (1) Å . One of the diisopropylamino groups is disordered over two positions, with site occipancy factors of ca 0.54 and 0.46. Hexakis{ 2 -4-[2-(diisopropylamino)ethylamino]pent-3-en-2-onato-3 N,O:O}tricalcium(II) hexane solvate P. Richard, M. Eleter, L. G. Hubert-Pfalzgraf and S. DanieleCommentThe title compound was obtained by reaction between the Ca silylamide Ca[N(SiMe 3 ) 2 ] 2 (THF) 2 (Westerhausen, 1991) and the ketoimine. Its solid state structure is similar to that of the strontium derivative. However, 1 H NMR data in solution (CDCl 3 or C 6 D 6 ) show the presence of two different molecular species. In concentrated solution (1.4 M in CDCl 3 ), one specie accounts for about 90% of the resonances while the amount of the second specie increases by dilution. These data suggest an equilibrium between a trinuclear form (I) having the solid state structure and a dimeric structure which could be similar to that reported for a tetrakis(β-ketoiminate)di-magnesium (Corazza et al., 1988).