Abstract [Bis (trimethylsilyl)] amino-Nt-butylphospha (III) azene is made in a two step synthesis. It can be oxidized by sulfur and selenium to a stable monomeric metathio-and metaselenophosphoric acid derivative and it forms with methanol the bis (amino) phosphine derivative which can be oxidized by CCl 4 to the aminophospha (V) azene derivative.