Tricarbonyl-eta-4-tricyclo[6.3.0.02.7]undeca-3,5-diene-trimethylphosphite-metal(0) and cis-dicarbonyl-eta-4-tricyclo[6.,3.0.02,7]undeca-3,5-diene-bis(trimethylphosphite)metal(0) complexes of chromium (1,4), molybdenum (2,5) and tungsten (3,6) have been prepared photochemically in high yields from the corresponding pentacarbonyl-trimethylphosphite-meta](0) or tetracarbonyl-bis(trimethylphosphite) metal(0) complexes, respectively, with tricyclo[6.3 .0.02,7 ]undeca-3,5-diene. The stereochemistry of 1-6 was determined by IR and NMR spectroscopy. In the case of tricarbonyl-eta-4-tricyclo[6.3.0.02,7] undeca-3,5-diene-trimethylphosphite-tungsten(0) (3), X-ray crystal and molecular structure analysis confirm the conclusions drawn from the spectroscopic data. The distorted pseudo-octahedral complexes 1-3 are obtained exclusively as f-isomers, and 4-6 as af-isomers. All of them show hindered ligand movements, according to their temperature-dependent NMR spectra. For 1-3 a. carbonyl scrambling, and for 4-6 a rotation of the diene ligand is observed.