A broadly applicable and efficient method for the synthesis of N-alkyliminophosphoranes from phosphines that does not use potentially hazardous alkyl azides is reported. Under iron catalysis, a hydroxylamine-derived triflic acid salt oxidizes phosphines to a wide range of iminophosphorane triflic acid salts. Diphosphines afford phosphine-iminophosphoranes that can serve as ligands in transition metal complexes. The developed method can be employed in the synthesis of mixed diiminophosphoranes and in a traceless Staudinger ligation.