Reactivity of a triamidoamine terminal uranium(VI)-nitride with 3d-transition metal metallocenes.

Reactions between [(Tren)UN] (1, Tren = {N(CHCHNSiPr)}) and [M(η-CR)] (M/R = Cr/H, Mn/H, Fe/H, Ni/H) were intractable, but M/R = Co/H or Co/Me afforded [(Tren)UN-(η:η-CH)Co(η-CH)] (2) and [(Tren)U-NH] (3), respectively. For M/R = V/H [(Tren)U-NV(η-CH)] (4), was isolated. Complexes 2-4 evidence one-/two-electron uranium reductions, nucleophilic nitrides, and partial N-atom transfer.

-Silanide f-Block Complexes: Insights into Paramagnetic Influence on NMR Chemical Shifts.

The paramagnetism of f-block ions has been exploited in chiral shift reagents and magnetic resonance imaging, but these applications tend to focus on H NMR shifts as paramagnetic broadening makes less sensitive nuclei more difficult to study. Here we report a solution and solid-state (ss) Si NMR study of an isostructural series of locally -symmetric early f-block metal(III) -hypersilanide complexes, [M{Si(SiMe)}(THF)] (; M = La, Ce, Pr, Nd, U); were also characterized by single crystal and powder X-ray diffraction, EPR, ATR-IR, and UV-vis-NIR spectroscopies, SQUID magnetometry, and elemental analysis. Only one SiMe signal was observed in the Si ssNMR spectra of , while two SiMe signals were seen in solution Si NMR spectra of and .

f-Element Zintl Chemistry: Actinide-Mediated Dehydrocoupling of HSb Affords the Trithorium and Triuranium Undeca-Antimontriide Zintl Clusters [{An(Tren)}(μ-Sb)] (An = Th, U; Tren = {N(CHCHNSiPr)}).

Reaction of the cesium antimonide complex [Cs(18C6)][SbH] (, 18C6 = 18-crown-6 ether) with the triamidoamine actinide separated ion pairs [An(Tren)(L)][BPh] (Tren = {N(CHCHNSiPr)}; An/L = Th/DME (); U/THF ()) affords the triactinide undeca-antimontriide Zintl clusters [{An(Tren)}(μ-Sb)] (An = Th (), U ()) by dehydrocoupling. Clusters and provide two new examples of the Sb Zintl trianion and are unprecedented examples of molecular Sb being coordinated to anything since all previous reports featured isolated Sb Zintl trianions in separated ion quadruple formulations with noncoordinating cations. Quantum chemical calculations describe dominant ionic An-Sb interactions in and , though the data suggest that the latter exhibits slightly more covalent An-Sb linkages than the former.

Arene-, Chlorido-, and Imido-Uranium Bis- and Tris(boryloxide) Complexes.

We introduce the boryloxide ligand {(HCNDipp)BO} (NBO, Dipp = 2,6-di-isopropylphenyl) to actinide chemistry. Protonolysis of [U{N(SiMe)}] with 3 equiv of NBOH produced the uranium(III) tris(boryloxide) complex [U(NBO)] (). In contrast, treatment of UCl with 3 equiv of NBOK in THF at room temperature or reflux conditions produced only [U(NBO)(Cl)(THF)] () with 1 equiv of NBOK remaining unreacted.

Thorium(IV)-antimony complexes exhibiting single, double, and triple polar covalent metal-metal bonds.

There is continued burgeoning interest in metal-metal multiple bonding to further our understanding of chemical bonding across the periodic table. However, although polar covalent metal-metal multiple bonding is well known for the d and p blocks, it is relatively underdeveloped for actinides. Homometallic examples are found in spectroscopic or fullerene-confined species, and heterometallic variants exhibiting a polar covalent σ bond supplemented by up to two dative π bonds are more prevalent.

Carbene Complexes of Plutonium: Structure, Bonding, and Divergent Reactivity to Lanthanide Analogs.

Organoplutonium chemistry was established in 1965, yet structurally authenticated plutonium-carbon bonds remain rare being limited to π-bonded carbocycle and σ-bonded isonitrile and hydrocarbyl derivatives. Thus, plutonium-carbenes, including alkylidenes and N-heterocyclic carbenes (NHCs), are unknown. Here, we report the preparation and characterization of the diphosphoniomethanide-plutonium complex [Pu(BIPMH)(I)(μ-I)] (, BIPMH = (MeSiNPPh)CH) and the diphosphonioalkylidene-plutonium complexes [Pu(BIPM)(I)(DME)] (, BIPM = (MeSiNPPh)C) and [Pu(BIPM)(I)(I)] (, I = C(NMeCMe)), thus disclosing non-actinyl transneptunium multiple bonds and transneptunium NHC complexes.

Comparison of group 4 and thorium M(IV) substituted cyclopentadienyl silanide complexes.

We report the synthesis and characterisation of a series of M(IV) substituted cyclopentadienyl hypersilanide complexes of the general formula [M(Cp){Si(SiMe)}(X)] (M = Hf, Th; Cp = Cp', {CH(SiMe)} or Cp'', {CH(SiMe)-1,3}; X = Cl, CH). The separate salt metathesis reactions of [M(Cp)(Cl)] (M = Zr or Hf, Cp = Cp'; M = Hf or Th, Cp = Cp'') with equimolar K{Si(SiMe)} gave the respective mono-silanide complexes [M(Cp'){Si(SiMe)}(Cl)] (M = Zr, 1; Hf, 2), [Hf(Cp'')(Cp'){Si(SiMe)}(Cl)] (3) and [Th(Cp''){Si(SiMe)}(Cl)] (4), with only a trace amount of 3 presumably formed silatropic and sigmatropic shifts; the synthesis of 1 from [Zr(Cp')(Cl)] and Li{Si(SiMe)} has been reported previously. The salt elimination reaction of 2 with one equivalent of allylmagnesium chloride gave [Hf(Cp'){Si(SiMe)}(η-CH)] (5), whilst the corresponding reaction of 2 with equimolar benzyl potassium yielded [Hf(Cp')(CHPh)] (6) together with a mixture of other products, with elimination of both KCl and K{Si(SiMe)}.

Electronic structure comparisons of isostructural early d- and f-block metal(iii) bis(cyclopentadienyl) silanide complexes.

We report the synthesis of the U(iii) bis(cyclopentadienyl) hypersilanide complex [U(Cp''){Si(SiMe)}] (Cp'' = {CH(SiMe)-1,3}), together with isostructural lanthanide and group 4 M(iii) homologues, in order to meaningfully compare metal-silicon bonding between early d- and f-block metals. All complexes were characterised by a combination of NMR, EPR, UV-vis-NIR and ATR-IR spectroscopies, single crystal X-ray diffraction, SQUID magnetometry, elemental analysis and calculations. We find that for the [M(Cp''){Si(SiMe)}] (M = Ti, Zr, La, Ce, Nd, U) series the unique anisotropy axis is conserved tangential to ; this is governed by the hypersilanide ligand for the d-block complexes to give easy plane anisotropy, whereas the easy axis is fixed by the two Cp'' ligands in f-block congeners.

Synthesis and Characterization of Yttrium Methanediide Silanide Complexes.

The salt metathesis reactions of the yttrium methanediide iodide complex [Y(BIPM)(I)(THF)] (BIPM = {C(PPhNSiMe)}) with the group 1 silanide ligand-transfer reagents MSiR (M = Na, R = BuMe or Bu; M = K, R = (SiMe)) gave the yttrium methanediide silanide complexes [Y(BIPM)(SiBuMe)(THF)] (), [Y(BIPM)(SiBu)(THF)] (), and [Y(BIPM){Si(SiMe)}(THF)] (). Complexes provide rare examples of structurally authenticated rare earth metal-silicon bonds and were characterized by single-crystal X-ray diffraction, multinuclear NMR and ATR-IR spectroscopies, and elemental analysis. Density functional theory calculations were performed on to probe their electronic structures further, revealing predominantly ionic Y-Si bonding.

Actinide Pnictinidene Chemistry: A Terminal Thorium Parent-Arsinidene Complex Stabilised by a Super-Bulky Triamidoamine Ligand.

We report the direct synthesis of the terminal pnictidenes [An(Tren )(PnH)][M(2,2,2-cryptand)] (Tren ={N(CH CH NSiCy ) } ; An/Pn/M=Th/P/Na 5, Th/As/K 6, U/P/Na 7, U/As/K 8) and their conversion to the pnictides [An(Tren )(PnH )] (An/Pn=Th/P 9, Th/As 10, U/P 11, U/As 12). Use of the super-bulky Tren ligand was essential to accessing complete families, and 6 is an unprecedented example of a terminal thorium-arsinidene complex and only the second structurally authenticated parent terminal arsinidene complex of any metal. Comparison of the terminal Th=AsH unit of 6 to the bridging ThAs(H)K linkage in structurally analogous [Th(Tren ){μ-As(H)K(15-crown-5)}] (Tren ={N(CH CH NSiPr ) } ) reveals a stronger Th-As bond in the former compared to the latter, and a large response overall to the nature of the Th=AsH bonding upon removal of the electrostatically-bound K-ion; the σ-bond changes little but the π-bond is significantly perturbed.

Mesoionic Carbene Complexes of Uranium(IV) and Thorium(IV).

We report the synthesis and characterization of uranium(IV) and thorium(IV) mesoionic carbene complexes [An{N(SiMe)}(CHSiMeNSiMe){MIC}] (An = U, and Th, ; MIC = {CN(Me)C(Me)N(Me)CH}), which represent rare examples of actinide mesoionic carbene linkages and the first example of a thorium mesoionic carbene complex. Complexes and were prepared via a C-H activation intramolecular cyclometallation reaction of actinide halides, with concomitant formal 1,4-proton migration of an -heterocyclic olefin (NHO). Quantum chemical calculations suggest that the An-carbene bond comprises only a σ-component, in contrast to the uranium(III) analogue [U{N(SiMe)}(MIC)] () where computational studies suggested that the 5f uranium(III) ion engages in a weak one-electron π-backbond to the MIC.

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).

Carbene Complexes of Neptunium.

Since the advent of organotransuranium chemistry six decades ago, structurally verified complexes remain restricted to π-bonded carbocycle and σ-bonded hydrocarbyl derivatives. Thus, transuranium-carbon multiple or dative bonds are yet to be reported. Here, utilizing diphosphoniomethanide precursors we report the synthesis and characterization of transuranium-carbene derivatives, namely, diphosphonio-alkylidene- and -heterocyclic carbene-neptunium(III) complexes that exhibit polarized-covalent σπ multiple and dative σ single transuranium-carbon bond interactions, respectively.

A Series of Rare-Earth Mesoionic Carbene Complexes.

We report the synthesis and characterisation of a series of rare-earth mesoionic carbene complexes, [RE{N(SiMe ) } {CN(Me)C(Me)N(Me)CH}] (3RE, RE=Sc, Ce, Pr, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu), greatly expanding the limited library of f-block mesoionic carbene complexes. These complexes were prepared by treatment of the parent RE-triamides with an N-heterocyclic olefin (NHO), where an NHO backbone proton undergoes a formal 1,4-proton migration to the NHO-methylene group. For all RE(III) metals, as expected, quantum chemical calculations suggest only a σ-component to the metal-carbene bonding, in contrast to a previously reported uranium(III) congener where the 5f metal engages in a weak π-back-bond to the MIC.

A terminal neptunium(V)-mono(oxo) complex.

Neptunium was the first actinide element to be artificially synthesized, yet, compared with its more famous neighbours uranium and plutonium, is less conspicuously studied. Most neptunium chemistry involves the neptunyl di(oxo)-motif, and transuranic compounds with one metal-ligand multiple bond are rare, being found only in extended-structure oxide, fluoride or oxyhalide materials. These combinations stabilize the required high oxidation states, which are otherwise challenging to realize for transuranic ions.

A crystalline tri-thorium cluster with σ-aromatic metal-metal bonding.

Metal-metal bonding is a widely studied area of chemistry, and has become a mature field spanning numerous d transition metal and main group complexes. By contrast, actinide-actinide bonding, which is predicted to be weak, is currently restricted to spectroscopically detected gas-phase U and Th (refs. ), UH and UH in frozen matrices at 6-7 K (refs.

Evidence for ligand- and solvent-induced disproportionation of uranium(IV).

Disproportionation, where a chemical element converts its oxidation state to two different ones, one higher and one lower, underpins the fundamental chemistry of metal ions. The overwhelming majority of uranium disproportionations involve uranium(III) and (V), with a singular example of uranium(IV) to uranium(V/III) disproportionation known, involving a nitride to imido/triflate transformation. Here, we report a conceptually opposite disproportionation of uranium(IV)-imido complexes to uranium(V)-nitride/uranium(III)-amide mixtures.

Si NMR Spectroscopy as a Probe of s- and f-Block Metal(II)-Silanide Bond Covalency.

We report the use of Si NMR spectroscopy and DFT calculations combined to benchmark the covalency in the chemical bonding of s- and f-block metal-silicon bonds. The complexes [M(SiBu)(THF)(THF)] (: M = Mg, Ca, Yb, = 0; M = Sm, Eu, = 1) and [M(SiBuMe)(THF)(THF)] (: M = Mg, = 0; M = Ca, Sm, Eu, Yb, = 1) have been synthesized and characterized. DFT calculations and Si NMR spectroscopic analyses of and (M = Mg, Ca, Yb, No, the last due to experimental unavailability) together with known {Si(SiMe)}-, {Si(SiMeH)}-, and {SiPh}-substituted analogues provide 20 representative examples spanning five silanide ligands and four divalent metals, revealing that the metal-bound Si NMR isotropic chemical shifts, δ, span a wide (∼225 ppm) range when the metal is kept constant, and direct, linear correlations are found between δ and computed delocalization indices and quantum chemical topology interatomic exchange-correlation energies that are measures of bond covalency.

Correlating axial and equatorial ligand field effects to the single-molecule magnet performances of a family of dysprosium bis-methanediide complexes.

Treatment of the new methanediide-methanide complex [Dy(SCS)(SCSH)(THF)] (, SCS = {C(PPhS)}) with alkali metal alkyls and auxillary ethers produces the bis-methanediide complexes [Dy(SCS)][Dy(SCS)(K(DME))] (), [Dy(SCS)][Na(DME)] () and [Dy(SCS)][K(2,2,2-cryptand)] (). For further comparisons, the bis-methanediide complex [Dy(NCN)][K(DB18C6)(THF)(toluene)] (, NCN = {C(PPhNSiMe)}, DB18C6 = dibenzo-18-crown-6 ether) was prepared. Magnetic susceptibility experiments reveal slow relaxation of the magnetisation for , with open magnetic hysteresis up to 14, 12, 15, and 12 K, respectively (∼14 Oe s).

Heteroleptic actinocenes: a thorium(iv)-cyclobutadienyl-cyclooctatetraenyl-di-potassium-cyclooctatetraenyl complex.

Despite the vast array of η -carbocyclic C complexes reported for actinides, cyclobutadienyl (C) remain exceedingly rare, being restricted to six uranium examples. Here, overcoming the inherent challenges of installing highly reducing C-ligands onto actinides when using polar starting materials such as halides, we report that reaction of [Th(η-CH)] with [K{C(SiMe)}] gives [{Th(η-C[SiMe])(μ-η-CH)(μ-η-CH)(K[CHMe])}{K(CHMe)}{K}] (), a new type of heteroleptic actinocene. Quantum chemical calculations suggest that the thorium ion engages in π- and δ-bonding to the η-cyclobutadienyl and η-cyclooctatetraenyl ligands, respectively.

Fragmentation, catenation, and direct functionalisation of white phosphorus by a uranium(IV)-silyl-phosphino-carbene complex.

Room temperature reaction of the uranium(iv)-carbene [U{C(SiMe3)(PPh2)}(BIPMTMS)(μ-Cl)Li(TMEDA)(μ-TMEDA)0.5]2 (1, BIPMTMS = C(PPh2NSiMe3)2) with white phosphorus (P4) produces the organo-P5 compound [P5{C(SiMe3)(PPh2)}2][Li(TMEDA)2] (2) and the uranium(iv)-methanediide [U{BIPMTMS}{Cl}{μ-Cl}2{Li(TMEDA)}] (3). This is an unprecedented example of cooperative metal-carbene P4 activation/insertion into a metal-carbon double bond and also an actinide complex reacting with P4 to directly form an organophosphorus species.

Dipnictogen f-Element Chemistry: A Diphosphorus Uranium Complex.

The first isolation and structural characterization of an f-element dinitrogen complex was reported in 1988, but an f-element complex with the first heavier group 15 homologue diphosphorus has to date remained unknown. Here, we report the synthesis of a side-on bound diphosphorus complex of uranium(IV) using a 7λ-(dimethylamino)phosphadibenzonorbornadiene-mediated P atom transfer approach. Experimental and computational characterization reveals that the diphosphorus ligand is activated to its dianionic (P) form and that in-plane U-P π-bonding dominates the bonding of the U(μ-η:η-P)U unit, which is supplemented by a weak U-P interaction of δ symmetry.

Insights into @metal-symmetry single-molecule magnetism: the case of a dysprosium-bis(boryloxide) complex.

We report the synthesis of the lanthanide-(bis)boryloxide complex [Dy{OB(NArCH)2}2(THF)4][BPh4] (2Dy, Ar = 2,6-Pri2C6H3), with idealised D4h@Dy(iii) point-group symmetry. Complex 2Dy exhibits single-molecule magnetism (SMM), with one of the highest energy barriers (Ueff = 1565(298) K) of any six-coordinate lanthanide-SMM. Complex 2Dy validates electrostatic model predictions, informing the future design of lanthanide-SMMs.