in dichloromethane addn. of P(OMe)3 to a stirred soln. of Mo-complex dissolved in CH2Cl2, colour changes from orangered to pale yellow, reaction for 6 h; removal of solvent and excess of P(OMe)3 under vac., extn. with hexane, removal under reduced pressure gives Mo-complex, recrystn. of remaining solid residue from CH2Cl2/hexane gives ligand;