Copper(0) does not catalyze the decomposition of dialkylcarbamoyl azides 5a-e but instead it is oxidized to copper(II) while the azides 5 are reduced by uptaking one electron per molecule and eliminating nitrogen. A probable explanation for the formation of the resulting copper(II) diisocyanate diamine complexes 8a, b (see Scheme 2) as well as the other reaction products is given. A mechanism involving a carbamoyl nitrene as well as a Curtius rearrangement can be excluded.