Palladium complexes of trio-o-tolyl phosphine and bis(diphenylphospino)ferrocene catalyze the reaction between aryl halides and either tin amides or amines in the presence of base to form aryl amines by halide substitution. This account describes our mechanistic and synthetic studies related to the amination reactions. These studies include kinetic behavior of the catalytic systems as well as direct observation of the primary stoichiometric reactions comprising the catalysis - including the rare C-N bond-forming reductive eliminations - and the mechanisms of these individual reactions. This paper also describes the development of tin-free amide sources and second generation amination catalysts that have resulted from our mechanistic understanding of the amination chemistry.