Samarium compounds transition

Investigations of Coulomb transitions in intermediate valent thulium (and samarium) compounds are an obvious development in this field. 

Kasuya, T, 1976, A mechanism for the metal insulator transition and various properties in samarium compounds, in Proc, Int. Conf. on Metal-Nonmetal Transitions, J. Phys. (Paris) Suppl. Colloq. 4, pp. 261-265. 

When HMPA was included in the reaction, 62, containing the correct stereochemistry for the target, was the major product. Compound 62 is thought to arise from transition structure 61, in which HMPA reduces the chelation of samarium to the substrate (Scheme 7.26). Lactone 62 was used to prepare all three botcinins.65... 

Because the 5d orbitals of lanthanide metals are shielded by 4f orbitals, the lanthanide metals cannot effectively back-bond like the transition metals, and the alkynes and the CO are expected to have no significant chemistry with organolanthanide complexes. However, the divalent samarium complex (C5Me5)2Sm(THF)2 can reduce diphenyl ethyne, and subsequently activate CO to generate a tetracyclic compound, as shown in Figure 8.33 [113]. 

Samarium iodide reacts with alkyl halides or ketones to generate radicals by electron transfer (see Volume 1, Chapter 2.1). An example is shown in Scheme 20. It is known that other transition metal compounds (Mn, Ni, Cu, Fe etc.) also act as radical initiators [19j. 

The nature of 4f electrons in lanthanides and their compounds, either localized or itinerant, is responsible for most of their physical and chemical properties. Localized states corresponding to tightly bound electron shells or to narrow bands of correlated electrons near the Fermi level are observed for all lanthanides. Pressure has a striking effect on the electronic structure, which, in turn, induces structural changes. For instance, crystal structure transitions from hexagonal closed packed (hep) samarium type double... 

George Fisher Baker assistant professor position at Cornell University was open so FHS took another temporary position, this time for the period 1935-1937. Spectroscopic studies of other crystalline compounds of samarium continued at Cornell and the studies were expanded to compounds of thulium, gadolinium, neodymium, erbium, and praseodymium. It was during this time, working with Hans Bethe, that FHS showed conclusively that the sharp lines observed in the absorption spectra of rare earth solid compounds arose from the inner shells of the rare earth ions and were due to 4f transitions. 

Structural transition has a drastic effect on the electrical behavior of these indides (abrupt change in the slope), but no observable effect on the magnetic data (table 20). The samarium and ytterbium compoimd show non-Ciuie-Weiss behavior. Specific heat data revealed a high y coefficient of 130 mJ/molK for the cerium compound (Pleger et al., 1987). 

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