Unprecedented CP systems: Me3SiX (X=Br, I) catalyses rearrangements of PIII esters R′R′′POR into the corresponding phosphoryl systems, providing a simple, mild and efficient route to a variety of structures containing PC bonds. The mechanism has been found to be fundamentally different from that of the Arbuzov–Michaelis reaction and includes three definite steps a, b and c (see scheme).