Substituted cyclopentadienyl ligands - 10. Intramolecular steric interactions in [(η5-C5H3(SiMe3) 2)Mo(CO)2(L)I]

Article abstract of DOI:10.1016/0277-5387(96)00188-X

Reaction of C₅H₄(SiMe₃)₂ with Mo(CO)₆ yielded [(η⁵-C₅H₃(SiMe₃) ₂)Mo(CO)₃]₂, which on addition of iodine gave [(η⁵-C₅H₃(SiMe₃) ₂)Mo(CO)₃I]. Carbonyl displacement by a range of ligands : [L = P(OMe)₃, P(OPrⁱ)₃, P(O-o-tol)₃, PMe₃, PMe₂Ph, PMePh₂, PPh₃, P(m-tol)₃] gave the new complexes [(η⁵-C₅H₃(SiMe₃) ₂)Mo(CO)₂(L)I]. For all L the trans isomer was the dominant, if not exclusive, isomer formed in the reaction. An NOE spectral analysis of [(η⁵-C₅H₃(SiMe₃) ₂)Mo(CO)₂(L)I] [L = PMe₂Ph, P(OMe)₃] revealed that the L group resided on the sterically uncongested side of the cyclopentadienyl ligand and that the ligand did not access the congested side of the molecule. Quantification of this phenomenon [L = P(OMe)₃] was achieved by means of the vertex angle of overlap methodology. This methodology revealed a steric preference with the trans isomer (less congestion of CO than I with an SiMe₃ group) being the more stable isomer for L = P(OMe)₃. Copyright