Aromatic Metalation Reactions by Palladium(II) and Platinum(II) on Aromatic Aldoximes and Ketoximes

Abstract

Ortho metalation by palladium(II) was observed in the reaction of lithium tetrachloropalladate(II) with various aromatic aldoximes and ketoximes in methanol in the presence of sodium acetate. The obtained chloro-bridged complexes(7) possessed both ortho-attached palladiumcarbon σ-bonding and palladium-nitrogen coordinate bonding to oximes. Reactions of O-acyl and O-methyl oximes with lithium tetrachloropalladate(II) were also carried out. An ortho metalation was observed in the former case, but dichlorobis(O-methyl oxime)palladium(II) type complexes containing no palladium-carbon σ-bonds were predominantly formed in the latter case. The bridge-splitting reaction of chloro-bridged complexes with triphenylphosphine and the metathetic reaction with sodium bromide in acetone were carried out. In the case of potassium tetrachloroplatinate(II), an ortho metalation reaction was observed giving the complexes(10) but chloro-bridged complexes could not be isolated.

Improved Palladium and Nickel Catalysts Heterogenised on Oxidic Supports (Silica, MCM‐41, ITQ‐2, ITQ‐6)

“…The 1600 cm À 1 frequencies may be assigned to C ¼ C and azomethine C ¼ N vibrations, shifted to lower wavenumbers (relative to the free ligands) due to N-coordination of the imine. [16] The IR spectra also shows strong bands at 1290 and $ 1500 cm À 1 assigned to the symmetric and asymmetric n(COO) vibrations, respectively, in agreement with those expected for monocoordinate acetate ligands. [17] New bands in the 500 -600 cm…”

Tetranuclear Complexes of PdII with Tridentate [C,N,O] and [O,N,O] Ligands: Synthesis, Reactivity and Structural Isomerism

“…The reaction of e and f with palladium(II) acetate in toluene gave the non-cyclometallated complexes [Pd{2-O-4,6-(MeO) 2 C 6 H 2 C(H)=N(2-OC 6 H 4 )}] 4 (1e) and [Pd{2-OC 6 H 4 C(H)=N(2-OC 6 H 4 )}] 4 (1f) as yellow and red airstable solids, respectively. The IR spectroscopic data was in good agreement with nitrogen coordination of the imine, [42,43] and absence of the ν(O-H) bands, indicated double deprotonation of the ligands; the latter was confirmed by the absence of the OH resonances in the 1 H NMR spectra. While the 1 H NMR spectrum for 1e showed a high-field shift of the HC=N resonance (δ = 1.19 ppm), similar to that observed for 1a-1c, the HC=N resonance for 1f appeared at δ = 8.94 ppm (shifted by 0.24 ppm), putting forward that the HC=N proton was not in the shielding area of the phenyl ring of an adjacent metallated ligand, probably because of cleavage of the tetranuclear structure caused by the coordination of [D 6 ]dmso used as the NMR solvent (vide supra).…”

“…The IR spectrum showed the shift of the ν(C=N) stretch toward lower wavenumbers from the free ligand value, because of nitrogen coordination of the imine, [42,43] and the absence of the ν(O-H) stretch, as compared to the ligand (3427 cm -1 ), in accordance with loss of the -OH proton. In the 1 H NMR spectrum the HC=N and 5-H resonances were high-field shifted, as compared to the uncoordinated ligand, by 1.43 and 0.9 ppm, respectively; the low δ values in these cases were due to the structure of the complexes, which puts the HC=N and 5-H protons in the proximity of the shielding zone of the phenyl rings of a neighbouring metallated ligand.…”

The First Crystal and Molecular Structure of asyn-Acetato-Bridged Dinuclear Cyclometallated Complex [Pd{2,3,4-(MeO)3C6HC(H)=NCH2CH2OH}(μ-OAc)]2

“…The IR spectrum of 2 shows the ν(CϭN) stretch at 1604 cm Ϫ1 , shifted to lower wavenumbers (relative to the free ligand) due to Ncoordination of the imine. [33,34] The IR spectrum also shows strong bands assigned to the symmetric and asymmetric ν(COO) vibrations, in agreement with bridging acetate ligands [35] (see Exp. Sect.).…”