Nuclear magnetic resonance studies of uranocenes

Conference · Tue Jan 01 04:00:00 EST 1980 · ACS Symp. Ser.; (United States)

OSTI ID:6507440

Luke, W D; Streitwieser, A Jr

The temperature dependent /sup 1/H NMR spectra of uranocene and a varity of substituted uranocenes verify that uranocenes have effective axial symmetry and the pseudocontact contribution to the total isotropic shift is evaluated. In alkyl-substituted uranocenes, conformational analysis shows that a primary alkyl substituent populates principally conformations in which the dihedral angle between the substituent C/sub ..cap alpha../ - C/sub BETA/ bond and the ring plane is close to 90/sup 0/ on the side of the ring away from the metal. X-ray analysis showed that substituents have ring-C/sub ..cap alpha../ bonds tilted several degrees towards uranium. The ring proton resonances and steric considerations suggest that t-butyl and related substituents are tilted away from uranium. Both contact and pseudocontact interactions contribute to the observed isotropic shifts in uranocenes. The contact component is dominant for ring protons, but rapidly attenuates with increasing number of sigma-bonds between the observed nucleus and the uranium such that the contact shift is effectively zero for BETA-protons. The value of the contact shift for ring protons in uranocene is of the same sign but about 10 to 15 ppM larger in magnitude than the contact shift for ring protons in CP/sub 3/U-X compounds. If a direct correlation exists between the magnitude of the contact shift and the degree of covalency in ligand-metal bonding in these systems, then the NMR data suggest a higher degree of covalency in the ligand-metal bonds in uranocene.

• Research Organization: Lawrence Berkeley La., CA
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 6507440
• Report Number(s): CONF-790917-P4
• Conference Information: Journal Name: ACS Symp. Ser.; (United States) Journal Volume: 131
• Country of Publication: United States
• Language: English

Related Subjects

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
400702* -- Radiochemistry & Nuclear Chemistry-- Properties of Radioactive Materials
ACTINIDE COMPLEXES
ALKENES
ANISOTROPY
CHEMICAL BONDS
COMPLEXES
CYCLOALKENES
CYCLOPENTADIENE
DIENES
HYDROCARBONS
MAGNETIC PROPERTIES
MAGNETIC RESONANCE
MAGNETIC SUSCEPTIBILITY
MOLECULAR STRUCTURE
NUCLEAR MAGNETIC RESONANCE
ORGANIC COMPOUNDS
ORGANOMETALLIC COMPOUNDS
PHYSICAL PROPERTIES
POLYENES
RESONANCE
SPECTRAL SHIFT
TEMPERATURE DEPENDENCE
URANIUM COMPLEXES