Synthetic and X-ray structural studies on pentabenzylcyclopentadienyl derivatives of manganese, rhenium, and iron

Article abstract of DOI:10.1021/om00105a038

(η⁵-Pentabenzylcyclopentadienyl)tricarbonylmanganese (3) and -rhenium (4) have been prepared in low yields from reactions between pentabenzylcyclopentadiene and dimanganese or dirhenium decacarbonyl in refluxing aromatic solvents. A reaction between pentabenzylcyclopentadienyllithium and anhydrous iron(II) chloride has afforded decabenzylferrocene (5) in 34% yield. The mixed-ring metallocenes pentemethylpentabenzylferrocene (6) and 1,2,3,4,5-pentabenzylferrocene (7) have been obtained via reactions of (C₅R₅)Fe(acac) (R = Me, Bz; acac = acetylacetonate) intermediates. The crystal structures of 3 and 5 have been determined via single-crystal X-ray diffraction. (η⁵-C₅Bz₅)Mn(CO)₃ crystallizes in the monoclinic space group P2₁/n with a = 12.908 (4) A?, b = 14.907 (3), A?, c = 18.575 (8) A?, β = 108.21 (4)°, and D_calcd = 1.28 g cm^-3 for Z = 4. The manganese center is pseudotetrahedral with Mn-C(η⁵) = 2.14 (1) A?, Mn-Cent = 1.77 A?, and Mn-CO = 1.772 (6) A?. (η⁵-C₅Bz₅)₂Fe·2C ₆H₅CH₃ crystallizes in the monoclinic space group P2₁/c with a = 13.871 (6) A?, b = 22.135 (8) A?, c = 23.700 (9) A?, β = 103.47 (5)°, and D_calcd = 1.19 g cm^-3 for Z = 4. The substituted cyclopentadienyl rings are parallel (Cent-Fe-Cent = 179.6°) and are staggered. The average Fe-C and Fe-Cent distances are 2.058 (7) and 1.65 A?, respectively. In 3, four of the phenyl rings are oriented up and away from the manganese center, with the fifth down toward the tripod ligands. Unexpectedly, in 5 all five phenyl rings in each ligand are oriented away from the metal center.