Compounds [Mo(CO)(4)(N-N)] (N-N = 4,4'-bis((4-methylphenyl)carbamoyl)-2,2'-bipyridine, bipy', 1; or 2,2'-biimidazole, H(2)biim, 2), [MoCl(eta(3)-methallyl)(CO)(2)(N-N)] (N-N = bipy', 3; H(2)biim, 4), and [Mo(eta(3)-methallyl)((CNBu)-Bu-t)(CO2)(N-N)]BAr'(4) (Ar' = 3,5-bis(trifluoromethyl)phenyl; N-N= bipy', 5; H(2)biim, 6) were synthesized and characterized, and their behavior toward anions was investigated in solution (IR and H-1 NMR) and in solid state (X-ray diffraction).