Zirconium-91 nuclear magnetic resonance spectroscopy: the first chemical study

NMR absolute shielding scales and nuclear magnetic dipole moments of transition metal nuclei

This work reports new, accurate nuclear magnetic dipole moments for transition metal nuclei where the long-standing systematic error due to obsolete diamagnetic correction has been eliminated by ab initio calculations of NMR shielding constants.

2000 Alcan Award Lecture Adventures in organometallic NMR: steric restraints, slowed rotations, and skeletal rearrangements

The structures and NMR fluxionality of a wide variety of organometallic complexes (including tetrahedral cluster cations and systems of the type (CnRn)ML3, where R = Et, Ph) are discussed. Barriers to tripodal and peripheral substituent rotations are reported, and the relevance of correlated rotations to molecular machines is outlined. Haptotropic shifts in (cyclopenta[def]phenanthrenyl)MLn and (cyclopenta[l]phenanthrenyl)MLn complexes are rationalized in terms of the aromatic character of the transition states. Likewise, the barriers to silatropic shifts in polyindenylsilanes can be correlated with the aromaticity of the intermediate isoindenes. Finally, the use of cobalt clusters to control cyclohexane ring conformations is described.Key words: NMR ring currents, fluxionality, correlated rotations, molecular rearrangements, haptotropic shifts.