Synthesis and molecular structure of (η5-pentamethyl-cyclopentadienyl) (η5-cyclopentadienyl) hexacarbonyl molybdenum tungsten

The metathesis reaction of Cp*(CO)3MoBr and NaW(CO)3Cp produced Cp*(CO)3Mo–W(CO)3Cp (1), featuring an unsupported Mo–W bond. Exposure of solutions of 1 to light leads to the quantitative formation of the corresponding homometallic dimers. In the solid state, the title complex exhibits an anti-arrangement of the η5-cyclopentadienyl and the η5-pentamethyl-cyclopentadienyl ligands and six terminal carbonyls. Comparison to corresponding complexes of molybdenum and tungsten reveals that the Mo–W distance is dictated by the presence of a Cp and a Cp* ligand. This is the first time that an unsupported Mo–W single bond distance is reported.