Photolysis of hexacarbonyl-chromium(0), -molybdenum(0), and -tungsten(0) in presence of fumaronitrile yields at room temperature pentacarbonyl-fumaronitrile-chromium(0) (1): molybdenum(0) (2), and -tungsten(0) (3). The complexes were purified by crystallization and characterized by IR and C-13-NMR spectroscopy. The fumaronitrile ligand is bonded to the M(CO)(5) moiety by one nitrile nitrogen atom rather than by the carbon-carbon double bond. In toluene 2 dissociates into fumaronitrile and pentacarbonyl-molybdenum(0), which is stabilized by the solvent. Fumaronitrile and solvated pentacarbonyl-molybdenum(0) exist in solution together with 2 in an equilibrium which lies in favour of the former species.