Cyclopentadienyl transfer reaction: thermal reaction between Re2(CO)10 and a series of cyclopentadienyl transition metal complexes

A thermal ligand transfer reaction between a series of organometallic cyclopentadienyl complexes and Re2(CO)10 as a source of Re(CO)3 is described. The expected CpRe(CO)3 complex, a very robust molecule, is obtained in yields ranging from poor, when the cyclopentadienyl precursor is thermally too stable or subject to a facile decomposition giving rise too easily to the volatile cyclopentadiene molecule, to excellent, such as with Cp2TiCl2 or Cp2Ni. We interpret the observed behavior by the fact that the hapticity of the ligand in the Ti and Ni substrates changes easily allowing for an extra temporary coordination of [Re2(CO)9], for example, generated in situ and leading to CpRe(CO)3. Heating titanium compound 1 with Re2(CO)10 led to CpRe(CO)3 and the substituted cyclopentadienyltricarbonylrhenium compound 2 with yields of 36 and 37%, respectively.