The infrared spectra of derivatives of manganese carbonyl of the type Mn(CO) 5L (L = H, CH 3, CD 3, C 6H 5, C 6H 5CH 2, Cl, Br, I) as well as of the parent carbonyl have been recorded in the 200–700 cm −1 region in cyclohexane and carbon tetrachloride solutions. In addition, the corresponding spectra of the ionic derivatives [Mn(CO) 6] +-BF 4- and Et 4N-[V(CO) 6]- have been recorded as Nujol mulls. Assignments for the metal-carbon stretching and metal-carbon-oxygen bending modes are discussed with special mention of possible correlations with the relevant carbon-oxygen stretching modes.