Improved Synthesis of Pentabenzylcyclopentadiene and Study of the Reaction between Pentabenzylcyclopentadiene and Iron Pentacarbonyl

An improved synthetic route to pentabenzylcyclopentadiene, C₅Bz₅H (1), has been developed, utilizing a larger amount of dicyclopentadiene, sodium, and excess benzyl alcohol as both reactant and solvent. Subsequent extraction and crystallization using hexane produced 1 in 62% yield. A reaction between 1 and iron pentacarbonyl in refluxing toluene led to the formation of [(η⁵-C₅Bz₅)Fe(CO)₂]₂ (2) and (η⁴-C₅Bz₅H)Fe(CO)₃ (3). Unlike the parent compound (η⁴-C₅H₆)Fe(CO)₃, 3 exhibited exceptional air and thermal stability. A single-crystal X-ray diffraction study of 3 has been undertaken and confirms the proposed structure.