Development of metal-catalyzed asymmetric synthesis of P-stereogenic phosphines has been guided by the hypothesis that pyramidal inversion occurs rapidly in metal–phosphido intermediates, but this process has not been observed directly for all metals of interest. We report an enantioselective copper­(Josiphos)-catalyzed alkylation of secondary phosphines and observation of the reaction intermediates, including variable temperature NMR studies of low-barrier pyramidal inversion at phosphorus in the key P-stereogenic terminal phosphido complexes Cu­(diphos*)­(PRR′), and an investigation of their reversible formation from secondary phosphine–silanolate complexes Cu­(diphos*)­[PHR­(R′)]­(OSiMe3).