Neptunium and plutonium complexes with a sterically encumbered triamidoamine (TREN) scaffold.

The syntheses and characterisation of isostructural neptunium(iv) and plutonium(iv) complexes [An(IV)(TREN(TIPS))(Cl)] [An = Np, Pu; TREN(TIPS) = {N(CH2CH2NSiPr(i)3)3}(3-)] are reported, along with the demonstration that they are likely reduced to the corresponding neptunium(iii) and plutonium(iii) products [An(III)(TREN(TIPS))]; this chemistry provides new platforms from which to target a plethora of unprecedented molecular functionalities in transuranic chemistry and the neptunium(iv) molecule is the first structurally characterised neptunium(iv)-amide complex.

Synthesis and characterization of potassium aryl- and alkyl-substituted silylchalcogenolate ligands.

Treatment of either triphenyl(chloro)silane or tert-butyldiphenyl(chloro)silane with potassium metal in THF, followed by addition of 18-crown-6, affords [K(18-crown-6)][SiPh3] () and [K(18-crown-6)][SiPh2(t)Bu] (), respectively, as the reaction products in high yield. Compounds and were fully characterized including by multi-nuclear NMR, UV/vis and IR spectroscopies. Addition of elemental chalcogen to either or , results in facile chalcogen insertion into the potassium-silicon bond to afford the silylchalcogenolates, [K(18-crown-6)][E-SiPh2R] (E = S, R = Ph (); E = Se, R = Ph (); E = Te, R = Ph (); E = S, R = (t)Bu (); E = Se, R = (t)Bu (); E = Te, R = (t)Bu ()), in moderate to good yield. The silylchalcogenolates reported herein were characterized by multi-nuclear NMR, UV/vis and IR spectroscopies, and their solid-state molecular structures were determined by single-crystal X-ray crystallography. Importantly, the reported compounds crystallize as discrete monomers in the solid-state, a structural feature not previously observed in silylchalcogenolates, providing well-defined access routes into systematic metal complexation studies.

Early-Lanthanide(III) Acetonitrile-Solvento Adducts with Iodide and Noncoordinating Anions.

Dissolution of LnI3 (Ln = La, Ce) in acetonitrile (MeCN) results in the highly soluble solvates LnI3(MeCN)5 [Ln = La (1), Ce (2)] in good yield. The ionic complex [La(MeCN)9][LaI6] (4), containing a rare homoleptic La(3+) cation and anion, was also isolated as a minor product. Extending this chemistry to NdI3 results in the consistent formation of the complex ionic structure [Nd(MeCN)9]2[NdI5(MeCN)][NdI6][I] (3), which contains an unprecedented pentaiodide lanthanoid anion. Also described is the synthesis, isolation, and structural characterization of several homoleptic early-lanthanide MeCN solvates with noncoordinating anions, namely, [Ln(MeCN)9][AlCl4]3 [Ln = La (5), Ce (6), Nd (7)]. Notably, complex 6 is the first homoleptic cerium MeCN solvate reported to date. All reported complexes were structurally characterized by X-ray crystallography, as well as by IR spectroscopy and CHN elemental analysis. Complexes 1-3 were also characterized by thermogravimetric analysis coupled with mass spectrometry to further elucidate their bulk composition in the solid-state.

Coordination chemistry of 2,2'-biphenylenedithiophosphinate and diphenyldithiophosphinate with U, Np, and Pu.

New members of the dithiophosphinic acid family of potential actinide extractants were prepared: heterocyclic 2,2'-biphenylenedithiophosphinic acids of stoichiometry HS2P(R2C12H6) (R = H or (t)Bu). The time- and atom-efficient syntheses afforded multigram quantities of pure HS2P(R2C12H6) in reasonable yields (∼60%). These compounds differed from other diaryldithiophosphinic acid extractants in that the two aryl groups were connected to one another at the ortho positions to form a 5-membered dibenzophosphole ring. These 2,2'-biphenylenedithiophosphinic acids were readily deprotonated to form S2P(R2C12H6)(1-) anions, which were crystallized as salts with tetraphenylpnictonium cations (ZPh4(1+); Z = P or As). Coordination chemistry between [S2P((t)Bu2C12H6)](1-) and [S2P(C6H5)2](1-) with U, Np, and Pu was comparatively investigated. The results showed that dithiophosphinate complexes of U(IV) and Np(IV) were redox stable relative to those of U(III), whereas reactions involving Pu(IV) gave intractable material. For instance, reactions involving U(IV) and Np(IV) generated An[S2P((t)Bu2C12H6)]4 and An[S2P(C6H5)2]4 whereas reactions between Pu(IV) and [S2P(C6H5)2](1-) generated a mixture of products from which we postulated a transient Pu(III) species based on UV-Vis spectroscopy. However, the trivalent Pu[S2P(C6H5)2]3(NC5H5)2 compound is stable and could be isolated from reactions between [S2P(C6H5)2](1-) and the trivalent PuI3(NC5H5)4 starting material. Attempts to synthesize analogous trivalent compounds with U(III) provided the tetravalent U[S2P(C6H5)2]4 oxidation product.

A Linear trans-Bis(imido) Neptunium(V) Actinyl Analog: Np(V)(NDipp)2((t)Bu2bipy)2Cl (Dipp = 2,6-(i)Pr2C6H3).

The discovery that imido analogs of actinyl dioxo cations can be extended beyond uranium into the transuranic elements is presented. Synthesis of the Np(V) complex, Np(NDipp)2((t)Bu2bipy)2Cl (1), is achieved through treatment of a Np(IV) precursor with a bipyridine coligand and lithium-amide reagent. Complex 1 has been structurally characterized, analyzed by (1)H NMR and UV-vis-NIR spectroscopies, and the electronic structure evaluated by DFT calculations.

Lanthanide(III) di- and tetra-nuclear complexes supported by a chelating tripodal tris(amidate) ligand.

Syntheses, structural, and spectroscopic characterization of multinuclear tris(amidate) lanthanide complexes is described. Addition of K3[N(o-PhNC(O)(t)Bu)3] to LnX3 (LnX3 = LaBr3, CeI3, and NdCl3) in N,N-dimethylformamide (DMF) results in the generation of dinuclear complexes, [Ln(N(o-PhNC(O)(t)Bu)3)(DMF)]2(µ-DMF) (Ln = La (1), Ce (2), Nd(3)), in good yields. Syntheses of tetranuclear complexes, [Ln(N(o-PhNC(O)(t)Bu)3)]4 (Ln = Ce (4), Nd(5)), resulted from protonolysis of Ln[N(SiMe3)2]3 (Ln = Ce, Nd) with N(o-PhNCH(O)(t)Bu)3. In the solid-state, complexes 1-5 exhibit coordination modes of the tripodal tris(amidate) ligand that are unique to the 4f elements and have not been previously observed in transition metal systems.

Synthesis and characterization of NpCl4(DME)2 and PuCl4(DME)2 neutral transuranic An(IV) starting materials.

The 1,2-dimethoxyethane (DME) solvento adducts of Np(iv) and Pu(iv) tetrachloride have been prepared and isolated in good and moderate yields, respectively, along with single-crystal structural determinations. These neutral molecules are expected to provide alternative synthetic pathways in the pursuit of non-aqueous and organometallic complexes.

Synthesis and spectroscopic and computational characterization of the chalcogenido-substituted analogues of the uranyl ion, [OUE]2+ (E = S, Se).

Addition of E (E = 0.125S8, Se) to [Cp*2Co][U(O)(NR2)3] (R = SiMe3) in THF results in the isolation of the chalcogen-substituted uranyl analogues [Cp*2Co][U(O)(E)(NR2)3] [E = S (1), Se (2)] in good yields. Similarly, addition of 1 equiv of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) to [Cp*2Co][U(O)(NR2)3] affords the uranyl complex [Cp*2Co][UO2(NR2)3] (3). All of the complexes were fully characterized, including analysis by X-ray crystallography. They were also analyzed by density functional theory calculations to probe the changes in the U-E bond as group 16 is descended.

A complete family of terminal uranium chalcogenides, [U(E)(N{SiMe3}2)3]- (E = O, S, Se, Te).

Addition of 1 equiv of E (E = 0.125 S(8), Se, Te) to U(H(2)C═PPh(3))(NR(2))(3) (R = SiMe(3)) (1) in Et(2)O results in generation of the terminal chalcogenide complexes, [Ph(3)PCH(3)][U(E)(NR(2))(3)] (E = S, 2; Se, 3; Te, 4; R = SiMe(3)), in modest yield. Complexes 2-4 represent extremely rare examples of terminal uranium monochalcogenides. Synthesis of the oxo analogue, [Cp*(2)Co][U(O)(NR(2))(3)] (5), was achieved by reduction of [U(O)(NR(2))(3)] with Cp*(2)Co. All complexes were fully characterized, including analysis by X-ray crystallography. In the solid state, complexes 2-5 feature short U-E bond lengths, suggestive of actinide-ligand multiple bonding.

Synthesis, molecular and electronic structure of U(V)(O)[N(SiMe3)2]3.

Addition of 1 equiv of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) to U(NR(2))(3) in hexanes affords U(O)(NR(2))(3) (2), which can be isolated in 73% yield. Complex 2 is a rare example of a terminal U(V) oxo complex. In contrast, addition of 1 equiv of Me(3)NO to U(NR(2))(3) (R = SiMe(3)) in pentane generates the U(IV) bridging oxo [(NR(2))(3)U](2)(µ-O) (3) in moderate yields. Also formed in this reaction, in low yield, is the U(IV) iodide complex U(I)(NR(2))(3) (4). The iodide ligand in 4 likely originates from residual NaI, present in the U(NR(2))(3) starting material. Complex 4 can be generated rationally by addition of 0.5 equiv of I(2) to a hexane solution of U(NR(2))(3), where it can be isolated in moderate yield as a tan crystalline solid. The solid-state molecular structures and magnetic susceptibilities of 2, 3, and 4 have been measured. In addition, the electronic structures of 2 and 3 have been investigated by density functional theory (DFT) methods.

Facile reduction of a uranyl(VI) ß-ketoiminate complex to U(IV) upon oxo silylation.

Reaction of the uranyl ß-ketoiminate complex UO(2)((tBu)acnac)(2) (1) ((tBu)acnac = (t)BuNC(Ph)CHC(Ph)O) with Me(3)SiI, in the presence of Ph(3)P, results in the reductive silylation of the uranyl moiety and formation of the U(V) bis-silyloxide complex [Ph(3)PI][U(OSiMe(3))(2)I(4)] (2). Subsequent reaction of 2 with Lewis bases, such as 2,2'-bipyridine (bipy), 1,10-phenanthroline (phen), and tetrahydrofuran (THF), results in a further reduction of the metal center and isolation of the U(IV) complexes U(OSiMe(3))(2)I(2)(bipy)(2) (3), U(OSiMe(3))(2)I(2)(phen)(2) (4), and [U(OSiMe(3))(2)I(THF)(4)][I(3)] (5), respectively.

Oxo ligand silylation in a uranyl beta-ketoiminate complex.

Addition of Me(3)SiI to UO(2)((Ar)acnac)(2) (ArNC(Ph)CHC(Ph)O, Ar = 3,5-(t)Bu(2)C(6)H(3)) (1) results in the formation of U(OSiMe(3))(2)I(2)((Ar)acnac) (2) in moderate yield. Also formed in the reaction are I(2) and ArNC(Ph)=CHC(Ph)OSiMe(3), the product of [(Ar)acnac](-) abstraction by Me(3)Si(+). In contrast, reaction of 1 with Me(3)SiX (X = Cl, OTf) only results in the formation of UO(2)(OTf)(2)((Ar)acnacH)(2)(Et(2)O) (3) and UO(2)Cl(2)((Ar)acnacH)(2) (4), respectively.