Pyrolysis of the homoleptic azido complex [P(N-3)(6)](-) was simulated using density functional theory based molecular dynamics and analyzed further using electronic structure calculations in atom-centered basis sets to calculate the geometries and electronic structures. Simulations at 600 and 1200 K predict a thermally induced and, on the simulation time scale, irreversible dissociation of an azido anion. The ligand loss is accompanied by a barrierless (free-energy) transition of the geometry of the complex coordination sphere from octahedral to trigonal bipyramidal. [P(N-3)(5)] is fluxional and engages in pseudorotation via a Berry mechanism.