A number of derivatives of the halogenocarbonyl-π-cyclopentacarbonylmolybdenum complexes C5H5Mo(CO)3X (X = Cl or l) has been prepared. Three types of compound have been isolated: (i) those containing the substituted cation [C5H5Mo(CO)2L2]+, where L = PEt3 and PPh3 or L2= 1,2-bisdiphenylphosphinoethane (Diphos) and o-phenylenebisdimethylarsine (Diars); (ii) the monosubstituted halides C5H5Mo(CO)2LCl, where L = PPh3, AsPh3, SbPh3, and 1/2Diphos, and C5H5Mo(CO)2Ll, where L = PEt3, P(cyclohexyl)3, PPh3, P(OPh)3, AsMePh2, AsPh3, and SbPh3; (iii) the disubstituted halides C5H5Mo(CO)L2Cl, where L = PEt3, PPh3, AsPh3, and SbPh3 and L2= Diphos, and C5H5Mo(CO)L2l, where L = PEt3, P(OPh)3, AsMePh2, and SbPh3, and L2= Diphos and Diars. The physical properties of these complexes are presented and discussed.