H3CPS, the first organophosphorus species with a PIIIS double bond, could be generated as intermediate by dehalogenation of the phosphorane H3CP(S)Cl2 with highly reactive magnesium. It was trapped with Mn2(CO)10. The H3CPS ligand in complex 1 is coupled side-on with Mn(CO)4 and end-on via the P atom with Mn(CO)5.