Pd(OAc)2 has the distinct Pd(II) peak at ~425 nm on UV-Vis, but adding NaNO2 (without heat) causes the peak to flatten quite a bit. Additionally, the flattened peak disappears completely upon heating briefly. No Pd(0) is in my reaction (not observed by UV-Vis and I can tolerate aryl iodides). Does this mean there is some form of SET/reduction (however, Pd I was never observed by EPR) or is it possible that nitrite (-NO2) binding with Pd affects the UV-Vis spectrum?