Stereochemical nonrigidity in metallocenium ions

Article abstract of DOI:10.1016/0022-328X(95)00114-6

Dynamic NMr spectrscopy of the MeB(C6F5)3^- salts of a series of ring-substituted zirconium- and hafnium-containing metallocenium ions, exemplified by (RCp)2ZrCH3⁺, reveals two exchange processes.One, having the lower free energy of activation, involves shift of the CH3 group from one lateral equatorial orbital to the other.The second results from exchange between the metal-CH3 and B-CH3 groups.Effects of structural variations on exchange barriers are discussed and related to metallocenium ion-catalyzed olefin polymerization.Keywords: Metallocenium ions; Stereochemical nonrigidity; Zirconium; Hafnium