- Integrated infrared intensity data are presented here for a series of complexes of the type Os(N2)X2[PR2C6H5]3 as well as for their carbonyl analogs. Dipole moment derivatives were calculated which involve both OsN or OsC and NN or CO stretching motions. The effective group dipole moment derivatives were found to be substantially larger for the carbonyl compounds as compared to the molecular nitrogen analogs and to vary within the dinitrogen series systematically with the nature of the phosphine and halide bound to the osmium. It is concluded on the basis of these results that CO is a better -donor and -acceptor ligand than N2. 1971, American Chemical Society. All rights reserved.