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Onset of rare earth behavior in the actinides
Journal
of the Less-Common
Metals,
Onset of rare earth behavior
93 (1983)357
357
in the actinides*
J. L. SMITH Los Alamos National Laboratory, Los Alamos, NM87545(U.S.A.) In the rare earth elements almost the entire cross-over from transition metal to localized f electron behavior occurs at cerium. In the actinides this behavior is spread out over uranium, neptunium and plutonium because ofthe more spatially extended 5f electrons [l]. If applied pressure is included, there is completely equivalent behavior between the rare earths and the actinides with only a shift to heavier elements in the actinides. There are then parallels in such properties as superconductivity, magnetism and mixed valence [a]. There are also tantalizing differences. For example some of the mixed valence behavior in samarium materials should occur in americium materials. Then the presence of one more f electron should simplify measurements of the mixed valent properties. The systematics of the actinides is compared with fhat of the rare earths. This work was performed under the auspices of the U.S. Department of Energy. 1 2
J. L. Smith and E. A. Kmetko, J. Less-Common Met., 90(1983) 83. J. L. Smith and Z. Fisk, J. Appl. Phys., 53(1982) 7883. J. L. Smith, Z. Fisk, J. 0. Willis and R. G. Haire, Am. Chem. Sot. Symp. Ser., to be published.
Bond strengths
of organothorium
and organouranium
compounds *
J. W. BRUNO and T. J. MARKS Department of Chemistry, Northwestern
University, Evanston, IL 60201 (U.S.A.)
L. R. MORSS Chemistry Division, (U.S.A.)
Argonne
National
Laboratory,
9700 South Cass Avenue,
Argonne,
IL 60439
The dissociation energies of Th-C, Th-H and U-C bonds were determined in a series of compounds of the general formula [n’-C5(CH3)&MR, where M is thorium or uranium and R represents hydrocarbyl, amide or hydride. Enthalpy data were obtained from heats of solution in toluene followed by heats of alcoholysis with tert-butanol in an inert gas batch titration reaction calorimeter. Calculated Th-R bond dissociation enthalpies range from 56 to 98 kcal mol-‘, decreasing in the order hydride 2 amides > alkyls; corresponding U-R bonds are approximately 8 kcal mol- ’ weaker. These results can be interpreted in terms of ligand geometry and the properties of the actinide ions. The data elucidate organoactinide reaction patterns involving C-H activation, cyclometallation, 8 hydride elimination and CO insertion. This work was performed under the auspices of the Office of Basic Energy Sciences, Division of Chemical Sciences, U.S. Department of Energy under Contract W-31-109-ENG-38 at Argonne National Laboratory and by the National Science Foundation under Grant CHE8009060 t0T.J.M. at Northwestern University.
* Abstract of a paper presented at the Sixteenth Rare Earth Research Conference, The Florida State University, Tallahassee, FL, U.S.A., April 18-21,1983. 0 Elsevier Sequoia/Printed
in The Netherlands
of the Less-Common
Metals,
Onset of rare earth behavior
93 (1983)357
357
in the actinides*
J. L. SMITH Los Alamos National Laboratory, Los Alamos, NM87545(U.S.A.) In the rare earth elements almost the entire cross-over from transition metal to localized f electron behavior occurs at cerium. In the actinides this behavior is spread out over uranium, neptunium and plutonium because ofthe more spatially extended 5f electrons [l]. If applied pressure is included, there is completely equivalent behavior between the rare earths and the actinides with only a shift to heavier elements in the actinides. There are then parallels in such properties as superconductivity, magnetism and mixed valence [a]. There are also tantalizing differences. For example some of the mixed valence behavior in samarium materials should occur in americium materials. Then the presence of one more f electron should simplify measurements of the mixed valent properties. The systematics of the actinides is compared with fhat of the rare earths. This work was performed under the auspices of the U.S. Department of Energy. 1 2
J. L. Smith and E. A. Kmetko, J. Less-Common Met., 90(1983) 83. J. L. Smith and Z. Fisk, J. Appl. Phys., 53(1982) 7883. J. L. Smith, Z. Fisk, J. 0. Willis and R. G. Haire, Am. Chem. Sot. Symp. Ser., to be published.
Bond strengths
of organothorium
and organouranium
compounds *
J. W. BRUNO and T. J. MARKS Department of Chemistry, Northwestern
University, Evanston, IL 60201 (U.S.A.)
L. R. MORSS Chemistry Division, (U.S.A.)
Argonne
National
Laboratory,
9700 South Cass Avenue,
Argonne,
IL 60439
The dissociation energies of Th-C, Th-H and U-C bonds were determined in a series of compounds of the general formula [n’-C5(CH3)&MR, where M is thorium or uranium and R represents hydrocarbyl, amide or hydride. Enthalpy data were obtained from heats of solution in toluene followed by heats of alcoholysis with tert-butanol in an inert gas batch titration reaction calorimeter. Calculated Th-R bond dissociation enthalpies range from 56 to 98 kcal mol-‘, decreasing in the order hydride 2 amides > alkyls; corresponding U-R bonds are approximately 8 kcal mol- ’ weaker. These results can be interpreted in terms of ligand geometry and the properties of the actinide ions. The data elucidate organoactinide reaction patterns involving C-H activation, cyclometallation, 8 hydride elimination and CO insertion. This work was performed under the auspices of the Office of Basic Energy Sciences, Division of Chemical Sciences, U.S. Department of Energy under Contract W-31-109-ENG-38 at Argonne National Laboratory and by the National Science Foundation under Grant CHE8009060 t0T.J.M. at Northwestern University.
* Abstract of a paper presented at the Sixteenth Rare Earth Research Conference, The Florida State University, Tallahassee, FL, U.S.A., April 18-21,1983. 0 Elsevier Sequoia/Printed
in The Netherlands