Non-trivial behavior of palladium(ii) acetate

Abstract

Reaction of activated palladium metal with a HNO3/acetic acid mixture produces both orange Pd3(OAc)6, 1, and purple Pd3(OAc)5(NO2), 2. Compound has a trinuclear structure derived from that of the well-known triangular complex 1 in which one acetate group has been replaced by a nitrite group which is bonded to one palladium atom by the nitrogen atom and to another Pd atom using one of the oxygen atoms. Highly pure 1 can be made by continuous removal of the nitric oxides from the reaction mixture using a flow of N2. 1H NMR spectra of solutions of 1 in CDCl3 and C6D6 show several signals of various intensities when a small amount of water is present in the deuterated solvents but only one signal when the solvents are thoroughly dried. These results are consistent with the occurrence of one or more hydrolysis processes when the solvents contain water and suggest that hypotheses about various [Pd(OAc)2]n aggregates that have previously been brought forward in the literature to explain the complexity of the spectrum of 1 are unnecessary, especially for nonpolar solvents. Compound 2 does not hydrolyze, and in wet or dried solvents shows a 1H NMR spectrum that consists of five equal-intensity signals due to the five nonequivalent acetate groups.

Palladium(II)‐Catalyzed Oxidative Carbocyclization of Aza‐Enallenes

“…A plausible explanation for this phenomenon is that the commercially available trimeric palladium acetate needs to be activated or dissociated in order to produce the monomeric species required for catalysis. [18] Another explanation could be that the Diels-Alder adduct participates as a ligand in the reaction; this type of activation has been previously suggested for the diacetoxylation of 1,3-dienes. [19] Once the optimum conditions for the transformation were found, we investigated the scope of the procedure, and the results are given in Table 2.…”

Speciation of Pd(OAc)2in ligandless Suzuki–Miyaura reactions

“…46 This was closely followed by a 1 H NMR study by Cotton and co-workers, which showed that the trimeric structure (1) is largely retained in methanol, chloroform and benzene. 47 The dipole moment or dielectric constant of a solvent is frequently invoked to describe its polarity, although the two properties are intrinsically different. This can be demonstrated by comparing methanol with NMP, which have markedly different dipole moments, yet very similar dielectric constants (Table 1).…”

Trinuclear Palladium(II) Acetate

“…16,17 Recently, we found that a complex pattern in the NMR spectrum in C 6 D 6 and CDCl 3 may be attributed to hydrolysis or to the formation of a nitrite derivative that is formed following some of the recently reported preparations for Pd 3 (OAc) 6 . 18 Here we report a reproducible and dependable two-step procedure for the synthesis of trinuclear Pd 3 (OAc) 6 from PdCl 2 . The method proceeds in high yield to produce a crystalline material that is soluble in various organic solvents and that gives a 1 H NMR spectrum with only one acetate resonance.…”