Various complexes of the types [Mo(DAD)(CO)(3)L] (L = CO, MeCN, MeOH, THF, DMSO, DMP, Me2CO, EtOAc, THT, Im(H), Im(1), tBuNC, nBu(3)P), (ER4)[Mo(DAD)(CO)(3)X] (ER4 = NEt4+; X- = Cl-, Br-, I-, NCS-, CN- and ER4+ = PPh4+; X- = N-3(-)), and (ER4)[{Mo(DAD)(CO)(3)}(2)(mu-X)] (ER4+ = NEW; X- = CN-, OAc- and ER4+ = PPh4+; X = N-3(-); DAD = N,N'-bis(2,6-dimethylphenyl)butane-2,3-diimine) were prepared by ligand exchange from cycloheptatriene molybdenum tricarbonyl. A total of 19 crystal structures were determined, including unprecedented structural characterization of molybdenum(0) coordination by dimethyl sulfoxide (DMSO), methanol, ethyl acetate (EtOAc), acetone, and N,N-dimethylfonnamide (DMF). Correlation of C-13 NAIR shifts with the complex geometry suggests a direct ligand-ligand interaction between DAD and O-bonded coligands with C=O and S=O double bonds, such as EtOAc, Me2CO, DMF, and DMSO. Unexpectedly, the solvatochromic properties of these tricarbonyl complexes [Mo(DAD)(CO)(3)L] are unfavorable for the determination of Kamlet-Taft parameters of the corresponding solvent L. Contrastingly, the UV/vis absorption of [Mo(DAD)(CO)(4)] is strongly correlated with the Kamlet-Taft parameter pi*, which is shown for 22 solvents, including seven room temperature ionic liquids.