Thermal Decomposition of Dicyclopentadienylniobium(IV)diphenyl

The thermal decomposition of dicyclopentadienylniobium(IV)diphenyl in the solid state and in hydrocarbon solvents has been studied. The compound decomposes with quantitative formation of C6H6 and a Nb-containing residue which has lost the Cp2Nb structure. Experiments with deuterated compounds and solvents show that decomposition proceeds via intramolecular abstraction of a hydrogen atom from a cyclopentadienyl ring. The reaction is first-order with an activation energy of about 35 kcal/mol, both in the solid state and in toluene. Deuteration of the phenyl groups leads to a higher value of the activation energy (~39 kcal/mol), whereas deuteration of the Cp ligands does not. The decomposition mechanism is discussed and compared with that of the analogous titanium compound.