Cyclopalladated acetate dimers: Crystal structures and VT-NMR

Cyclopalladation of 3-methoxyimino-2-phenyl-3H-indoles

“…1 H and 13 C{ 1 H} NMR studies of 2a and 2b in CDCl 3 at room temperature showed two sets of superimposed signals of relative intensities 2.8:1.0 (for 2a) and 2.7:1.0 (for 2b), which could be indicative of the presence of two isomeric species [hereinafter referred to as 2a I and 2a II (for 2a) and 2b I and 2b II (for 2b)] in solution. Examples of the coexistence of two isomers of related dimeric compounds (l-OAc) 2 [Pd(j 2 -C,N-ligand)] 2 have been reported previously [14][15][16]. 1 H NMR spectra of 2a and 2b, showed that the chemical shifts of the OMe protons were very similar to those of the corresponding Scheme 1. ligand for all the isomers.…”

“…It is well-known that the dimeric cyclopalladated complexes (lOAc) 2 [Pd(j 2 -C,N-ligand)] 2 may exhibit different isomeric forms [14][15][16]18]. In these isomers, the two halves of the molecule could be in a trans-or cis-arrangement (Fig.…”

“…3). It has been reported that for the trans-isomers the resonance of the methyl groups of the bridging ligands appear as one singlet, but it splits into two singlets in the cis-isomers [14,15]. For 2a I and 2b I , one singlet [at 2.29 (for 2a I ) or 2.26 ppm (for 2b I )] was observed in the 1 H NMR spectra; thus, we assumed that in these species the two halves were in a trans-arrangement.…”

Synthesis of Cyclopalladated Derivatives of (E)‐N‐Benzylidene‐2‐(2,6‐dichlorophenyl)ethanamine and Their Reactivity towards Monodentate and Symmetric Bidentate Lewis Bases

“…These data are consistent with a dimeric folded structure with a trans configuration for compound 2, which is the usual structure adopted for acetato-bridged cyclopalladated dimers in CDCl 3 solution and in the solid state. [19] In this dimeric structure, the acetato ligands bridge two palladium(II) centres and the imines are coordinated to them in a chelate mode through their iminic nitrogen and C1 aromatic carbon atoms (Figure 4, A). Furthermore, the 1 H NMR spectrum of compound 2 in CDCl 3 solution is also consistent with its ortho-cyclopalladated nature as two ortho protons, one from each imine ligand, are absent from the spectrum.…”

N-heterocyclic carbenes: Reaction to give anilines

“…In the course of our research into platinum [8][9][10] and palladium [11][12][13][14][15] complexes, we sought to synthesise some NHC complexes of palladium via the direct reaction of an imidazolium chloride salt with palladium acetate. In the process we discovered a new reactivity of the NHC ligand, which we report here.…”