I am conducting Buchwald-Hartwig amination. I use $\ce{Pd_2(dba)3}$ and $\ce{P(o-tol)_3}$ as catalyst and toluene as solvent. Temperature is 100 ℃ and reaction time is 24 hours. During the reaction, formation of dark precipitate is observed. So I filter the reaction mixture through Celite pad when I do work-up.
The dark precipitate is observed. Is this dark material $\ce{Pd}$ metal formed by degradation of $\ce{Pd_2(dba)3}$? Reactant is aza-crown and bromothiophene, base is $\ce{Et_3N}$. Initially I thought that this would be the insoluble salt, $\ce{Et_3NHBr}$, but Pubchem says that its color is white. I searched several papers using keywords 'Buchwald-Hartwig amination byproducts', 'Buchwald-Hartwig amination degradation of catalyst', etc, but couldn't find satisfying answers. If this is really $\ce{Pd}$ metal, is the degradation due to too high temperature?