C-Cl Bond Activation at Rotated vs Unrotated Dinuclear Site Related to [FeFe]-Hydrogenases.

The novel dinuclear complex related to the [FeFe]-hydrogenases active site, [Fe(μ-pdt)(κ-dmpe)(CO)] (), is highly reactive toward chlorinated compounds CHCl ( = 1, 2) affording selectively terminal or bridging chloro diiron isomers through a C-Cl bond activation. DFT calculations suggest a cooperative mechanism involving a formal concerted regioselective chloronium transfer depending on the unrotated or rotated conformation of two isomers of .

Geometrical influence on the non-biomimetic heterolytic splitting of H by bio-inspired [FeFe]-hydrogenase complexes: a rare example of frustrated Lewis pair based reactivity.

Despite the high levels of interest in the synthesis of bio-inspired [FeFe]-hydrogenase complexes, H oxidation, which is one specific aspect of hydrogenase enzymatic activity, is not observed for most reported complexes. To attempt H-H bond cleavage, two disubstituted diiron dithiolate complexes in the form of [Fe(μ-pdt)L(CO)] (L: PMe, dmpe) have been used to play the non-biomimetic role of a Lewis base, with frustrated Lewis pairs (FLPs) formed in the presence of B(CF) Lewis acid. These unprecedented FLPs, based on the bimetallic Lewis base partner, allow the heterolytic splitting of the H molecule, forming a protonated diiron cation and hydrido-borate anion.

Uranium-nitride chemistry: uranium-uranium electronic communication mediated by nitride bridges.

Treatment of [U(N)(Tren)] (1, Tren = {N(CHCHNSiPr)}) with excess Li resulted in the isolation of [{U(μ-NLi)(Tren)}] (2), which exhibits a diuranium(IV) 'diamond-core' dinitride motif. Over-reduction of 1 produces [U(Tren)] (3), and together with known [{U(μ-NLi)(Tren)}] (4) an overall reduction sequence 1 → 4 → 2 → 3 is proposed. Attempts to produce an odd-electron nitride from 2 resulted in the formation of [{U(Tren)}(μ-NH)(μ-NLi)Li] (5).

Terminal uranium(V)-nitride hydrogenations involving direct addition or Frustrated Lewis Pair mechanisms.

Despite their importance as mechanistic models for heterogeneous Haber Bosch ammonia synthesis from dinitrogen and dihydrogen, homogeneous molecular terminal metal-nitrides are notoriously unreactive towards dihydrogen, and only a few electron-rich, low-coordinate variants demonstrate any hydrogenolysis chemistry. Here, we report hydrogenolysis of a terminal uranium(V)-nitride under mild conditions even though it is electron-poor and not low-coordinate. Two divergent hydrogenolysis mechanisms are found; direct 1,2-dihydrogen addition across the uranium(V)-nitride then H-atom 1,1-migratory insertion to give a uranium(III)-amide, or with trimesitylborane a Frustrated Lewis Pair (FLP) route that produces a uranium(IV)-amide with sacrificial trimesitylborane radical anion.

Correction: Facile N-functionalization and strong magnetic communication in a diuranium(v) bis-nitride complex.

[This corrects the article DOI: 10.1039/C8SC05721D.].

Thorium- and uranium-azide reductions: a transient dithorium-nitride isolable diuranium-nitrides.

Molecular uranium-nitrides are now well known, but there are no isolable molecular thorium-nitrides outside of cryogenic matrix isolation experiments. We report that treatment of [M(Tren)(I)] (M = U, ; Th, ; Tren = {N(CHCHNSiMeBu )}) with NaN or KN, respectively, affords very rare examples of actinide molecular square and triangle complexes [{M(Tren)(μ-N)} ] (M = U, = 4, ; Th, = 3, ). Chemical reduction of produces [{U(Tren)}(μ-N)][K(THF)] () and [{U(Tren)}(μ-N)] (), whereas photolysis produces exclusively .

Facile N-functionalization and strong magnetic communication in a diuranium(v) bis-nitride complex.

Uranium nitride complexes are of high interest because of their ability to effect dinitrogen reduction and functionalization and to promote magnetic communication, but studies of their properties and reactivity remain rare. Here we have prepared in 73% yield the diuranium(v) bis-nitride complex [K{[U(OSi(O Bu))](μ-N)}], , from the thermal decomposition of the nitride-, azide-bridged diuranium(iv) complex [K{[U(OSi(O Bu))](μ-N)(μ-N)}], The bis-nitride reacts in ambient conditions with 1 equiv. of CS and 1 equiv.

Structural Snapshots of Cluster Growth from {U } to {U } During the Hydrolysis of UCl.

Herein we report the assembly of large uranium(IV) clusters with novel nuclearities and/or shapes from the controlled hydrolysis of UCl in organic solution and in the presence of the benzoate ligands. {U }, {U }, {U }, {U }, {U } oxo and oxo/hydroxo clusters were isolated and crystallographically characterized. These structural snapshots indicate that larger clusters are slowly built from the condensation of octahedral {U } building blocks.

Nitrogen reduction and functionalization by a multimetallic uranium nitride complex.

Molecular nitrogen (N) is cheap and widely available, but its unreactive nature is a challenge when attempting to functionalize it under mild conditions with other widely available substrates (such as carbon monoxide, CO) to produce value-added compounds. Biological N fixation can do this, but the industrial Haber-Bosch process for ammonia production operates under harsh conditions (450 degrees Celsius and 300 bar), even though both processes are thought to involve multimetallic catalytic sites. And although molecular complexes capable of binding and even reducing N under mild conditions are known, with co-operativity between metal centres considered crucial for the N reduction step, the multimetallic species involved are usually not well defined, and further transformation of N-binding complexes to achieve N-H or N-C bond formation is rare.

CO Cleavage and CO Functionalization under Mild Conditions by a Multimetallic CsU Nitride Complex.

Novel efficient chemical processes involving cheap and widely accessible carbon dioxide or carbon monoxide under mild conditions for the production of valuable chemical products are highly desirable in the current energetic context. Uranium nitride materials act as high activity catalysts in the Haber-Bosch process but the reactivity of molecular nitride compounds remains unexplored. Here we review recent results obtained in our group showing that a multimetallic nitride complex [Cs{[U(OSi(OtBu)3)3]2(μ-N)}] (1) with a CsUIV-N-UIV core, is able to promote N-C bond formation due to its strong nucleophile behaviour.

Synthesis and SMM behaviour of trinuclear versus dinuclear 3d-5f uranyl(v)-cobalt(ii) cation-cation complexes.

Trinuclear versus dinuclear heterodimetallic UOCo complexes were selectively assembled via a cation-cation interaction by tuning the ligand. The trimeric complex 2, with a linear [Co-O[double bond, length as m-dash]U[double bond, length as m-dash]O-Co] core, exhibits magnetic exchange and slow relaxation with a reversal barrier of 30.5 ± 0.

Isolation of a Star-Shaped Uranium(V/VI) Cluster from the Anaerobic Photochemical Reduction of Uranyl(VI).

Actinide oxo clusters are an important class of compounds due to their impact on actinide migration in the environment. The photolytic reduction of uranyl(VI) has potential application in catalysis and spent nuclear fuel reprocessing, but the intermediate species involved in this reduction have not yet been elucidated. Here we show that the photolysis of partially hydrated uranyl(VI) in anaerobic conditions leads to the reduction of uranyl(VI), and to the incorporation of the resulting U species into the stable mixed-valent star-shaped U /U oxo cluster [U(UO ) (μ -O) (PhCOO) (Py) ] (1).

Nucleophilic Reactivity of a Nitride-Bridged Diuranium(IV) Complex: CO2 and CS2 Functionalization.

Thermolysis of the nitride-bridged diuranium(IV) complex Cs{(μ-N)[U(OSi(O(t) Bu)3)3]2} (1) showed that the bridging nitride behaves as a strong nucleophile, promoting N-C bond formation by siloxide ligand fragmentation to yield an imido-bridged siloxide/silanediolate diuranium(IV) complex, Cs{(μ-N(t) Bu)(μ-O2 Si(O(t) Bu)2)U2 (OSi(O(t) Bu)3)5}. Complex 1 displayed reactivity towards CS2 and CO2 at room temperature that is unprecedented in f-element chemistry, affording diverse N-functionalized products depending on the reaction stoichiometry. The reaction of 1 with two equivalents of CS2 yielded the thiocyanate/thiocarbonate complex Cs{(μ-NCS)(μ-CS3 )[U(OSi(O(t)Bu)3)3]2} via a putative NCS(-)/S(2-) intermediate.

Synthesis and Structure of Nitride-Bridged Uranium(III) Complexes.

The reduction of the nitride-bridged diuranium(IV) complex Cs[{U(OSi(OtBu)3)3}2(μ-N)]affords the first example of a uranium nitride complex containing uranium in the +III oxidation state. Two nitride-bridged complexes containing the heterometallic fragments Cs2[U(III---)-N-(---U(IV)] and Cs3[U(III---)-N-(---U(III)] have been crystallographically characterized. The presence of two or three Cs+ cations binding the nitride group is key for the isolation of these complexes.

Heterometallic Fe2 (II) -U(V) and Ni2 (II) -U(V) Exchange-Coupled Single-Molecule Magnets: Effect of the 3 d Ion on the Magnetic Properties.

Uranium-based compounds have been put forward as ideal candidates for the design of single-molecule magnets (SMMs) with improved properties, but to date, only two examples of exchange-coupled 3d-5f SMM containing uranium have been reported and both are based on the Mn(II) ion. Here we have synthesized the first examples of exchange-coupled uranium SMMs based on Fe(II) and Ni(II) . The SMM behavior of these complexes containing a quasi linear {M-O=U=O-M} core arises from intramolecular Fe-U and Ni-U exchange interactions combined with the high Ising anisotropy of the uranyl(V) moiety.

CO2 conversion to isocyanate via multiple N-Si bond cleavage at a bulky uranium(III) complex.

The reaction of the sterically saturated uranium(III) tetrasilylamido complex [K(18c6)][U(N(SiMe3)2)4] with CO2 leads to CO2 insertion into the U-N bond affording the stable U(IV) isocyanate complex [K(18c6)][U(N(SiMe3)2)3(NCO)2]n that was crystallographically characterized. DFT studies indicate that the reaction involves the [2+2] cyclo-addition of a double bond of O=CO to the U-N(SiMe3)2 bond and proceeds to the final product through multiple silyl migration steps.

A zig-zag uranyl(v)-Mn(ii) single chain magnet with a high relaxation barrier.

The synthesis, structural characterization and magnetic properties of a 1D zig-zag coordination polymer based on a cation-cation [(U(V)O2)Mn(II)] repeated unit are reported; it shows single chain magnet (SCM) behaviour with a high energy barrier of 122 K.

Ferrocene-Based Tetradentate Schiff Bases as Supporting Ligands in Uranium Chemistry.

Uranyl(VI), uranyl(V), and uranium(IV) complexes supported by ferrocene-based tetradentate Schiff-base ligands were synthesized, and their solid-state and solution structures were determined. The redox properties of all complexes were investigated by cyclic voltammetry. The bulky salfen-(t)Bu2 allows the preparation of a stable uranyl(V) complex, while a stable U(IV) bis-ligand complex is obtained from the salt metathesis reaction between [UI4(OEt2)2] and K2salfen.

Single-molecule-magnet behavior in mononuclear homoleptic tetrahedral uranium(III) complexes.

The magnetic properties of the two uranium coordination compounds, [K(18c6)][U(OSi(O(t)Bu)3)4] and [K(18c6)][U(N(SiMe3)2)4], both presenting the U(III) ion in similar pseudotetrahedral coordination environments but with different O- or N-donor ligands, have been measured. The static magnetic susceptibility measurements and density functional theory studies suggest the presence of different ligand fields in the two compounds. Alternating-current susceptibility studies conducted at frequencies ranging from 95 to 9995 Hz and at temperatures in the 1.

Self-assembly of a 3d-5f trinuclear single-molecule magnet from a pentavalent uranyl complex.

Mixed-metal uranium compounds are very attractive candidates in the design of single-molecule magnets (SMMs), but only one 3d-5f hetero-polymetallic SMM containing a uranium center is known. Herein, we report two trimeric heterodimetallic 3d-5f complexes self-assembled by cation-cation interactions between a uranyl(V) complex and a TPA-capped M(II)  complex (M=Mn (1), Cd (2); TPA=tris(2-pyridylmethyl)amine). The metal centers were strategically chosen to promote the formation of discrete molecules rather than extended chains.

A uranium-based UO2(+)-Mn2+ single-chain magnet assembled trough cation-cation interactions.

Single-chain magnets (SCMs) are materials composed of magnetically isolated one-dimensional (1D) units exhibiting slow relaxation of magnetization. The occurrence of SCM behavior requires the fulfillment of stringent conditions for exchange and anisotropy interactions. Herein, we report the synthesis, the structure, and the magnetic characterization of the first actinide-containing SCM.

Uranium and manganese assembled in a wheel-shaped nanoscale single-molecule magnet with high spin-reversal barrier.

Discrete molecular compounds that exhibit both magnetization hysteresis and slow magnetic relaxation below a characteristic 'blocking' temperature are known as single-molecule magnets. These are promising for applications including memory devices and quantum computing, but require higher spin-inversion barriers and hysteresis temperatures than currently achieved. After twenty years of research confined to the d-block transition metals, scientists are moving to the f-block to generate these properties.