<p>It is well-known that f-block
elements can exhibit coordination modes which surpass those of the transition
metals. With uranyl and uranium bis(imido) complexes a strong preference is
shown for the oxo or imido ligands in the <i>trans-</i>
position; a phenomenon which is known as the inverse trans- influence which is
unique to high valent actinides. However, when a third imido is added to the
complex, a decrease in bond order occurs and this preference is diminished.
Through the synthesis of several novel coordination complexes of
tris(2,6-diisopropylphenyl)imido uranium [U(NDipp)<sub>3</sub>] with a variety
of ligands, we were able to analyze the energy differentials between bonding
modes in both the solution and solid state. Furthermore, density functional
theory calculations were employed to model the energetic preferences between
these geometries. The combination of analyses gives rise to the observation
that the orientation of the imido substituents is fluxional depending on the
rigidity of the supporting ligands, and oftentimes exhibits low energetic
barriers for the formation of different conformers.</p>
<p> Uranium
tris(imido) species bearing <i>trans</i>-imidos
are desirable synthons as they can be used to mimic reactivity of more
complicated uranium oxide polymeric systems. Such systems are advantageous as
they are easily soluble in organic solvents, making them amenable to standard
characterization methods and ligand substitution strategies. Our group has
previously shown that uranium tris(imidos), easily synthesized from [(<sup>Mes</sup>PDI<sup>Me</sup>)U(THF)]<sub>2</sub>
and various azides, feature axial imido substituents exhibiting differing bond
characteristics than the adjacent equatorial imido substituent. The aim of this
work is to show that multiple analogues of mixed imido products can be formed
from either the aforementioned dimer or stable tris(imido) synthons by
exploiting reactivity differences between the axial and equatorial positions. </p>
Presented
herein are novel copper-​catalyzed ring opening reactions of cyclopropanols and
various electrophiles to synthesize a variety of beta-​functionalized ketones.
The reactions feature mild conditions and tolerates a wide selection of
functional groups leading to complex products which can be used in the
synthesis of bioactive molecules.
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/7438823 |
| Date | 16 January 2019 |
| Creators | Kristen E. Gettys (5929688) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Journal contribution |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/Synthesis_and_Characterization_of_High_and_Low_Valent_Uranium_Nitrogen_Complexes_and_Copper_Catalyzed_Cross-Coupling_Reactions_of_Brominated_Compounds/7438823 |
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