Nitrite anion effects in cross-coupling reactions at Pd
We have shown how nitrite anion can influence the yields of palladium complexes derived from Pd(OAc)2.
We believe that nitrite anions could influence certain cross-coupling processes, especially those where anionic ligands are present.
The appearance of nitrite anions was explained by nitrite impurities originating from impure Pd(OAc)2.
The figure opposite shows what happens when you react water with "Pd(OAc)2" and how nitrite is able to take up a similar position to acetate in the extended Pd3 cluster complex.
It is straight-forward to analyse the purity of Pd(OAc)2 by NMR spectroscopic analysis.
Pure "Pd(OAc)2" is usually Pd3(OAc)6, with D3h symmetry (one acetate methyl signal in the 1H NMR spectrum - highlighted in green).
The figure below shows how 1H NMR can be used. It should be noted for analysis of polymeric Pd(OAc)2 that solid-state 13C NMR (MAS) methods may be required.
Stacked 1H NMR spectra of various forms of "Pd(OAc)2".