The synthesis of a series of Mo(CO)5(PPh2XR) complexes are reported. The complexes have been characterized by multinuclear NMR-, infrared,-, and mass spectroscopy. Chemical shift correlations between the carbonyl 13C and 17O, P-C 13C, 31P and 95Mo chemical shifts are demonstrated to depend upon the similarity in size of the XR groups. Fair to excellent correlations between these chemical shifts and similar chemical shifts of some cis-Mo(CO)4(PPh2XR)2 complexes are reported and indicate that the steric effect the PPh2XR ligands are similar in the two sets of complexes. © 1984.