Synthesis, structure and redox properties of single-atom bridged diuranium complexes supported by aryloxides.

Single-atom (group 15 and group 16 anions) bridged dimetallic complexes of low oxidation state uranium provide a convenient route to implement multielectron transfer and promote magnetic communication in uranium chemistry, but remain extremely rare. Here we report the synthesis, redox and magnetic properties of N, O, and S bridged diuranium complexes supported by bulky aryloxide ligands. The U(IV)/U(IV) nitride [Cs(THF)][(U(OAr))(μ-N)], 1 could be prepared and characterized but could not be reduced.

Siloxide tripodal ligands as a scaffold for stabilizing lanthanides in the +4 oxidation state.

Synthetic strategies to isolate molecular complexes of lanthanides, other than cerium, in the +4 oxidation state remain elusive, with only four complexes of Tb(iv) isolated so far. Herein, we present a new approach for the stabilization of Tb(iv) using a siloxide tripodal trianionic ligand, which allows the control of unwanted ligand rearrangements, while tuning the Ln(iii)/Ln(iv) redox-couple. The Ln(iii) complexes, [Ln((OSiPhAr)-arene)(THF)] (1-Ln) and [K(toluene){Ln((OSiPhAr)-arene)(OSiPh)}] (2-Ln) (Ln = Ce, Tb, Pr), of the (HOSiPhAr)-arene ligand were prepared.

Two-Electron Redox Reactivity of Thorium Supported by Redox-Active Tripodal Frameworks.

The high stability of the + IVoxidation state limits thorium redox reactivity. Here we report the synthesis and the redox reactivity of two Th(IV) complexes supported by the arene-tethered tris(siloxide) tripodal ligands [(KOSiR Ar) -arene)]. The two-electron reduction of these Th(IV) complexes generates the doubly reduced [KTh((OSi(O Bu) Ar) -arene)(THF) ] (2 ) and [K(2.

Isolation and redox reactivity of cerium complexes in four redox states.

The chemistry of lanthanides is limited to one electron transfer reactions due to the difficulty of accessing multiple oxidation states. Here we report that a redox-active ligand combining three siloxides with an arene ring in a tripodal ligand can stabilize cerium complexes in four different redox states and can promote multielectron redox reactivity in cerium complexes. Ce(iii) and Ce(iv) complexes [(LO)Ce(THF)] (1) and [(LO)CeCl] (2) (LO = 1,3,5-(2-OSi(OBu)CH)CH) were synthesized and fully characterized.

Bonding and Reactivity in Terminal versus Bridging Arenide Complexes of Thorium Acting as Th Synthons.

Thorium redox chemistry is extremely scarce due to the high stability of Th . Here we report two unique examples of thorium arenide complexes prepared by reduction of a Th -siloxide complex in presence of naphthalene, the mononuclear arenide complex [K(OSi(O Bu) ) Th(η -C H )] (1) and the inverse-sandwich complex [K(OSi(O Bu) ) Th] (μ-η ,η -C H )] (2). The electrons stored in these complexes allow the reduction of a broad range of substrates (N O, AdN , CO , HBBN).

Reactivity of Multimetallic Thorium Nitrides Generated by Reduction of Thorium Azides.

Thorium nitrides are likely intermediates in the reported cleavage and functionalization of dinitrogen by molecular thorium complexes and are attractive compounds for the study of multiple bond formation in f-element chemistry, but only one example of thorium nitride isolable from solution was reported. Here, we show that stable multimetallic azide/nitride thorium complexes can be generated by reduction of thorium azide precursors─a route that has failed so far to produce Th nitrides. Once isolated, the thorium azide/nitride clusters, MTh═N═Th (M = K or Cs), are stable in solutions probably due to the presence of alkali ions capping the nitride, but their synthesis requires a careful control of the reaction conditions (solvent, temperature, nature of precursor, and alkali ion).

Synthesis, structure, and reactivity of uranium(vi) nitrides.

Uranium nitride compounds are important molecular analogues of uranium nitride materials such as UN and UN which are effective catalysts in the Haber-Bosch synthesis of ammonia, but the synthesis of molecular nitrides remains a challenge and studies of the reactivity and of the nature of the bonding are poorly developed. Here we report the synthesis of the first nitride bridged uranium complexes containing U(vi) and provide a unique comparison of reactivity and bonding in U(vi)/U(vi), U(vi)/U(v) and U(v)/U(v) systems. Oxidation of the U(v)/U(v) bis-nitride [K{U(OSi(O Bu))(μ-N)}], , with mild oxidants yields the U(v)/U(vi) complexes [K{U(OSi(O Bu))(μ-N)}], and [K{U(OSi(O Bu))}(μ-N)(μ-I)], while oxidation with a stronger oxidant ("magic blue") yields the U(vi)/U(vi) complex [{U(OSi(O Bu))}(μ-N)(μ-thf)], .

N-Heterocyclic Carbene Copper(I) Rotaxanes Mediate Sequential Click Ligations with All Reagents Premixed.

We have prepared NHC-Cu complexes with a rotaxane structure and used them as sterically sensitive catalysts for one-pot sequential copper-catalyzed azide/alkyne cycloadditions in solutions containing all of the coupling partners premixed in unprotected form. Most notably, a photolabile and sterically encumbered complex first catalyzed the coupling of a less bulky azide/alkyne pair; after removing the protective macrocyclic component from the rotaxane structure, through irradiation with light, the exposed dumbbell-shaped NHC-Cu complex catalyzed the second click reaction of a bulkier azide/alkyne pair. Using this approach, we obtained predominantly, from a single sealed pot, a bis-triazole product (84 %) from a mixture of two sterically distinct azides and a diyne.

Interlocking increases the persistence of N-heterocyclic carbenes in solution.

In this study imidazolium and imidazolinium centers in precursor [2]rotaxanes were deprotonated to obtain interlocked molecules featuring stabilized N-heterocyclic carbene centers. The encircling macrocyclic components enhanced the persistence of the otherwise unstable imidazolidin-2-ylidenes in solution at 253 K for more than a week in the absence of air.