Synthesis and Thermal Behavior of Heteroleptic γ‐Substituted Acetylacetonate‐Alkoxides of Titanium

Abstract

A series of heteroleptic titanium derivatives of general formula [Ti(OiPr) 2 (R-acac) 2 ] with acetylacetonate ligands modified in the internal (γ-or 3-) position by different substituents (R = OAc, NO 2 , Me, Et, Cl, Br) has been synthesized and completely characterized by liquid multinuclear NMR and FTIR. The influence of the nature of the group on the thermal stability of the different complexes was studied by thermogravimetric analysis (TGA) and gave the following decreasing stability ranking: H < NO 2 < Cl < Me < Br < Et < OAc. DFT calculations showed that this ranking followed the same order as the stability of the keto-enolate form compared to the β-diketonate form. Other DFT calculations also confirmed that for these molecules the ligands degraded sequentially and that the singular high reactivity of the Et-acac based complex could be due to the rupture of the CÀ C bond to lead to a CH 2°-acac radical, which triggers the decomposition.

Role of Anionic Backbone in NHC‐Stabilized Coinage Metal Complexes: New Precursors for Atomic Layer Deposition**

“…The electron‐withdrawing effect of the coordinated diketonate should thus also influence the carbene‐metal interaction as less electron density is available at the metal nucleus for π‐electron backdonation to the carbenic carbon atom of the NHC which should elongate and thus weaken the C−M bond. A similar study was carried out by Bijou et al., in which the thermodynamic stability of heteroleptic Titanium‐diketonate complexes could be linked to the p K a value of the diketonate species [37] . This effect is observed for the Cu complexes (Figure 3a) with an elongation of the C−M bond from 1.871 (dmm) to 1.895 Å (hfac).…”

“…A similar study was carried out by Bijou et al, in which the thermodynamic stability of heteroleptic Titanium-diketonate complexes could be linked to the pK a value of the diketonate species. [37] This effect is observed for the Cu complexes (Figure 3a) with an elongation of the CÀ M bond from 1.871 (dmm) to 1.895 Å (hfac). Even though a relation between NMR shifts and pK a values for the parent Ag complexes (Figure 3b) can be postulated as expected, there seems to be no significant influence of the electron-withdrawal of the diketonate backbone on the actual CÀ M bond lengths which range from 2.091 (acac) to 2.111 Å (fod).…”

Cover Feature: Role of Anionic Backbone in NHC‐Stabilized Coinage Metal Complexes: New Precursors for Atomic Layer Deposition (Chem. Eur. J. 16/2022)

“…A similar study was carried out by Bijou et al, in which the thermodynamic stability of heteroleptic Titanium-diketonate complexes could be linked to the pK a value of the diketonate species. [37] This effect is observed for the Cu complexes (Figure 3a) with an elongation of the CÀM bond from 1.871 (dmm) to 1.895 Å (hfac). Even though a relation between NMR shifts and pK a values for the parent Ag complexes (Figure 3b) can be postulated as expected, there seems to be no significant influence of the electron-withdrawal of the diketonate backbone on the actual CÀM bond lengths which range from 2.091 (acac) to 2.111 Å (fod).…”