122212-53-7Relevant articles and documents
Steric effects associated with monosubstituted cyclopentadienyl transition-metal complexes. Synthesis and NMR spectroscopic and molecular mechanics study of [(η5-C5H4But)Fe(CO)(L)I] complexes and crystal structure determination of [(η5-C5H4But)Fe(CO)(PPh 3)I]
Du Plooy, Karen E.,Marais, Charles F.,Carlton, Laurence,Hunter, Roger,Boeyens, Jan C. A.,Coville, Neil J.
, p. 3855 - 3860 (2008/10/08)
The influence of the bulky cyclopentadienyl substituent tert-butyl (But) on the conformational preferences of complexes of the type [(η5-C5H4But)Fe(CO)(L)I], where L = group 15 donor ligand, was investigated. 1H NMR spectra show that the four protons, H2-H5, on the cyclopentadienyl ligand give rise to four separate resonance groups. The distance between the two outer resonances, corresponding to the two ortho ring protons, increases with increasing size of L and ring substituent (Me, But). NMR coupling and nOe spectroscopy unambiguously indicate a conformational preference where H4 (the "meta" cyclopentadienyl ring proton) and the group 15 donor ligand are close to being eclipsed. Molecular mechanics methods were applied to [(η5-C5H4But)Fe(CO)P(OMe) 3I] to obtain a preferential conformation and energy profile for rotation about the iron-cyclopentadienyl bond axis. The lowest energy conformation obtained corresponded to that deduced from NMR spectroscopy. The crystal and molecular structure of [(η5-C5H4But)Fe(CO)(PPh 3)I] was obtained. (FeC28H28OIP: space group P1; Z = 2; a = 9.231 (2), b = 10.484 (2), c = 14.082 (2) A?; α = 111.47 (2), β = 79.02 (1), γ = 93.17 (2)°; R = 0.049.) The conformation of this compound when viewed along the iron-cyclopentadienyl axis corresponds to the most favorable conformer obtained from NMR and molecular mechanics studies, with H4 close to the PPh3 ligand.
