In conclusion, we have developed a general synthetic route to azophosphines, via the corresponding azophosphine-borane, and probed the fundamental structure of these underexplored compounds. We have demonstrated controlled κ 1 P and κ 2 P,N coordination to Ru(II), highlighting a key difference between the P and N congeners. We are continuing to study the coordination chemistry and catalysis of azophosphines, and their potential to act as functionalised photoswitches.