Cyclopentadienone Vanadium(I) Complex: Synthesis, Red/Ox Activity, and Application to Catalytic Transfer Hydrogenation

Cyclopentadienone late transition metal complexes have exhibited various catalytic transformation and elementary reactions by transferring electrons from the metal to ligand, the so-called metal–ligand cooperation mechanism. Herein, we report a cyclopentadienone low-valent early transition metal, a vanadium(I), complex. The obtained complex furnished the most extended CO bond length among all of the analogous CpO metal complexes, showing a substantial degree of metal-to-ligand electron transfer. The red/ox activity of the vanadium center in the cyclopentadienone V(I) complex was confirmed upon the addition of the proton source to yield the hydroxycyclopentadienyl V(III) complex. The system was applied to catalytic transfer hydrogenation of carbonyl compounds, indicating the possible application of the red/ox of the early transition metals in metal–ligand cooperative organic transformations.