Structures of the radical P[N(SiMe3)2](NPri2), its dimer, cation and chloro derivativeElectronic supplementary information (ESI) available: The final Cartesian coordinates of the computed structures of the diphosphine 2 and the corresponding radical 3, a selected list of distances and associated amplitudes of vibrations and the correlation matrix from the electron diffraction least-squares refinements. See http://www.rsc.org/suppdata/dt/b4/b402926g/