The potential energy surface for internal rotation about the phosphorus-phosphorus bond was calculated at the PCM DCM /B3LYP/6-311++G(d,p) computational level for a set of eight symmetrical, unsymmetrical and P-stereogenic diphosphines; H 4 P 2 , Me 4 P 2 , (CF 3 ) 4 P 2 , Ph 4 P 2 , Me 2 P-P(CF 3 ) 2 , Me 2 P-PPh 2 , and the meso-and dl-isomers of Me(CF 3 )P-PMe(CF 3 ) and MePhP-PMePh. Certain trends in the data were elucidated and compared with conflicting data from the literature regarding the relative population of anti and gauche rotational isomers. The pyramidal inversion barriers (stereomutation barriers in P-stereogenic cases) for the same set of diphosphines was estimated through the inversion transition states and also compared to literature values. Finally, the Me 4 P 2 + (CF 3 ) 4 P 2 → 2Me 2 (CF 3 ) 2 P 2 metathesis reaction was also explored to evaluate its feasibility versus inversion. The finding of larger barriers in the metathesis than in the inversion rules in favour of an inversion mechanism for the stereomutation of P-stereogenic diphosphines.