Single-crystal cryogenic X-ray diffraction at 6 K, electron paramagnetic resonance spectroscopy, and correlated electronic structure calculations are combined to shed light on the nature of the metal−tris(aryloxide) and η 2 −H, C metal−alkane interactions in the [(( t•Bu ArO) 3 tacn)U III ( Me cy-C6)]•( Me cy-C6) adduct. An analysis of the ligand field experienced by the uranium center using ab initio ligand field theory in combination with the angular overlap model yields rather unusual U−O ArO and U−N tacn bonding parameters for the metal−tris(aryloxide) interaction. These parameters are incompatible with the concept of σ and π metal−ligand overlap. For that reason, it is deduced that metal− ligand bonding in the [(( t•Bu ArO) 3 tacn)U III ] moiety is predominantly ionic. The bonding interaction within the [(( t•Bu ArO) 3 tacn)-U III ] moiety is shown to be dispersive in nature and essentially supported by the upper-rim t Bu groups of the ( t•Bu ArO) 3 tacn 3− ligand.Our findings indicate that the axial alkane molecule is held in place by the guest−host effect rather than direct metal−alkane ionic or covalent interactions.
We present the synthesis and reactivity of a newly developed, cyclen-based tris-aryloxide ligand, namely cyclen(Me)(t-Bu,t-BuArOH)3, and its coordination chemistry to uranium. The corresponding uranium(III) complex [UIII((OArt-Bu,t-Bu)3(Me)cyclen)] (1) was characterized by...
The activation of chalcogen–chalcogen bonds using
organometallic
uranium complexes has been well documented for S–S, Se–Se,
and Te–Te bonds. In stark contrast, reports concerning the
ability of a uranium complex to activate the O–O bond of an
organic peroxide are exceedingly rare. Herein, we describe the peroxide
O–O bond cleavage of 9,10-diphenylanthracene-9,10-endoperoxide
in nonaqueous media, mediated by a uranium(III) precursor [((Me,AdArO)3N)UIII(dme)] to generate a
stable uranium(V) bis-alkoxide complex, namely, [((Me,AdArO)3N)UV(DPAP)]. This reaction proceeds via
an isolable, alkoxide-bridged diuranium(IV/IV) species, implying that
the oxidative addition occurs in two sequential, single-electron oxidations
of the metal center, including rebound of a terminal oxygen radical.
This uranium(V) bis-alkoxide can then be reduced with KC8 to form a uranium(IV) complex, which upon exposure to UV light,
in solution, releases 9,10-diphenylanthracene to generate a cyclic
uranyl trimer through formal two-electron photooxidation. Analysis
of the mechanism of this photochemical oxidation via density functional
theory (DFT) calculations indicates that the formation of this uranyl
trimer occurs through a fleeting uranium cis-dioxo
intermediate. At room temperature, this cis-configured
dioxo species rapidly isomerizes to a more stable trans configuration through the release of one of the alkoxide ligands
from the complex, which then goes on to form the isolated uranyl trimer
complex.
We report a series of uranium complexes stabilized by the pentakis-benzyl-derivatized cyclopentadienyl ligand, Cp Bn5 . Treatment of [UCl 4 ] and [UI 3 (1,4-dioxane) 1,5 ] with 2 equiv of the potassium salt, Cp Bn5 K, yielded the corresponding complexes [(Cp Bn5 ) 2 U IV (Cl) 2 ] (1) and [(Cp Bn5 ) 2 U III (I)] (4). Subsequently, tetravalent 1 is either methylated to give [(Cp Bn5 ) 2 U IV (Me) 2 ] (2) or reduced to form trivalent [(Cp Bn5 ) 2 U III (μ-Cl) 2 K(OEt 2 ) 3 ] (3). Oxidation of 4 with AgI yields [(Cp Bn5 ) 2 U IV (I) 2 ] (5), which was found to generate rarely observed, linear uranium metallocenes [(Cp Bn5 ) 2 U IV (NCMe) 5 ][X] 2 (X = PF 6 − (6), BPh 4 − (7)) upon abstraction of the iodide ligands with thallium salts in acetonitrile. All complexes were characterized by 1 H NMR spectroscopy, CHN elemental analysis, UV−vis−NIR spectroscopy, and SQUID magnetization measurements. The solid-state molecular structures of 1−7 were determined by single-crystal X-ray diffraction analysis. An in-depth computational analysis revealed the peculiar electronic structure of the linearly coordinated title complex 7 and its closely related, parent [(Cp*) 2 U IV (NCMe 3 ) 5 ] 2+ dication.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.