216 research outputs found
Actinide Triamidoamine (Tren<sup>R</sup>) Chemistry:Uranium and Thorium Derivatives Supported by a DiphenylâtertâButylâSilylâTren Ligand
We report the synthesis and characterisation of thorium(IV), uranium(III), and uranium(IV) complexes supported by a sterically demanding triamidoamine ligand with N-diphenyl-tert-butyl-silyl substituents. Treatment of ThCl4(THF)3.5 or UCl4 with [Li3(TrenDPBS)] (TrenDPBS = {N(CH2CH2NSiPh2But)3}3-) afforded [An(TrenDPBS)Cl] (An = Th, 1Th; U, 1U). Complexes 1An react with benzyl potassium to afford the cyclometallates (TrenDPBScyclomet) [An{N(CH2CH2NSiPh2But)2(CH2CH2NSiPhButC6H4)}] (An = Th, 2Th; U, 2U). Treatment of 1An with sodium azide affords [An(TrenDPBS)N3] (An = Th, 3Th; U, 3U). Reaction of 3Th with potassium graphite affords 2Th. In contrast, 3Th reacts with cesium graphite to afford the doubly-cyclometallated (TrenDPBSd-cyclomet) ate complex [Th{N(CH2CH2NSiPh2But) CH2CH2NSiPhButC6H4)}2Cs(THF)3] (4). In contrast to 3Th, reaction of 3U with potassium graphite produces the uranium(III) complex [U(TrenDPBS)] (5), and 5 can also be prepared by reaction of potassium graphite with 1U. The loss of azide instead of conversion to nitrides contrasts to prior work when the silyl group is iso-propyl silyl, underscoring how ligand substituents profoundly drive the reaction chemistry. Several complexes exhibit T-shaped meta-C-H¡¡¡phenyl and staggered parallel p-p-stacking interactions, demonstrating subtle weak interactions that drive ancillary ligand geometries. Compounds 1An-3An, 4, and 5 have been variously characterised by single crystal X-ray diffraction, multi-nuclear NMR spectroscopy, infrared spectroscopy, UV/Vis/NIR spectroscopy, and elemental analyses
Uranium-Carbene-Imido Metalla-Allenes: Ancillary-Ligand-Controlled Cis-/Trans-Isomerisation and Assessment of Trans-Influence in the R2C=UIV=NR' Unit (R = Ph2PNSiMe3; R' = CPh3)
Thorium(IV) alkyl synthesis from a thorium(III) cyclopentadienyl complex and an Nheterocyclic olefin
Synthesis and Characterisation of Lanthanide N-Trimethylsilyl and -Mesityl Functionalised Bis(iminophosphorano)methanides and -Methanediides
We report the extension of the series of {BIPMTMSH}â (BIPMR = C{PPh2NR}2, TMS = trimethylsilyl) derived rare earth methanides by the preparation of [Ln(BIPMTMSH)(I)2(THF)] (Ln = Nd, Gd, Tb), 1aâc, in 34â50% crystalline yields via the reaction of [Ln(I)3(THF)3.5] with [Cs(BIPMTMSH)]. Similarly, we have extended the range of {BIPMMesH}â (Mes = 2,4,6-trimethylphenyl) derived rare earth methanides with the preparation of [Gd(BIPMMesH)(I)2(THF)2], 3, (49%) and [Yb(BIPMMesH)(I)2(THF)], 4, (26%), via the reaction of [Ln(I)3(THF)3.5] with [{K(BIPMMesH)}2]. Attempts to prepare dysprosium and erbium analogues of 3 or 4 were not successful, with the ion pair species [Ln(BIPMMesH)2][BIPMMesH] (Ln  = Dy, Er), 5aâb, isolated in 31â39% yield. The TMEDA (N',N',N",N"-tetramethylethylenediamine) adducts [Ln(BIPMMesH)(I)2(TMEDA)] (Ln = La, Gd), 6aâb, were prepared in quantitative yield via the dissolution of [La(BIPMMesH)(I)2(THF)] or 3 in a TMEDA/THF solution. The reactions of [Ln(BIPMMesH)(I)2(THF)] [Ln = La, Ce, Pr, and Gd (3)] or 6aâb with a selection of bases did not afford [La(BIPMMes)(I)(S)n] (S = solvent) as predicted, but instead led to the isolation of the heteroleptic complexes [Ln(BIPMMes)(BIPMMesH)] (Ln = La, Ce, Pr and Gd), 7aâd, in low yields due to ligand scrambling
Photolytic and Reductive Activations of 2âArsaethynolate in a UraniumâTriamidoamine Complex: Decarbonylative Arsenic GroupâTransfer Reactions and Trapping of a Highly Bent and Reduced Form
Little is known about the chemistry of the 2-arsaethynolate anion, but to date it has exclusively undergone fragmentation reactions when reduced. Herein, we report the synthesis of [U(Tren(TIPS))(OCAs)] (2, Tren(TIPS)=N(CH(2)CH(2)NSiiPr(3))(3)), which is the first isolable actinide-2-arsaethynolate linkage. UV-photolysis of 2 results in decarbonylation, but the putative [U(Tren(TIPS))(As)] product was not isolated and instead only [{U(Tren(TIPS))}(2)(mu-eta(2):eta(2)-As2H2)] (3) was formed. In contrast, reduction of 2 with [U(Tren(TIPS))] gave the mixed-valence arsenido [{U(Tren(TIPS))}(2)(mu-As)] (4) in very low yield. Complex 4 is unstable which precluded full characterisation, but these photolytic and reductive reactions testify to the tendency of 2-arsaethynolate to fragment with CO release and As transfer. However, addition of 2 to an electride mixture of potassium-graphite and 2,2,2-cryptand gives [{U(Tren(TIPS))}(2){mu-eta(2)(OAs):eta(2)(CAs)-OCAs}][K(2,2,2-cryptand)] (5). The coordination mode of the trapped 2-arsaethynolate in 5 is unique, and derives from a new highly reduced and bent form of this ligand with the most acute O-C-As angle in any complex to date (O-C-As angle approximate to 128 degrees). The trapping rather than fragmentation of this highly reduced O-C-As unit is unprecedented, and quantum chemical calculations reveal that reduction confers donor-acceptor character to the O-C-As unit
The âHiddenâ Reductive [2+2+1]âCycloaddition Chemistry of 2âPhosphaethynolate Revealed by Reduction of a ThâOCP Linkage
The reduction chemistry of the newly emerging 2âphosphaethynolate (OCP)â is not well explored, and many unanswered questions remain about this ligand in this context. We report that reduction of [Th(TrenTIPS)(OCP)] (2, TrenTIPS=[N(CH2CH2NSiPri3)]3â), with RbC8 via [2+2+1] cycloaddition, produces an unprecedented hexathorium complex [{Th(TrenTIPS)}6(ÎźâOC2P3)2(ÎźâOC2P3H)2Rb4] (5) featuring four fiveâmembered [C2P3] phosphorus heterocycles, which can be converted to a rare oxo complex [{Th(TrenTIPS)(ÎźâORb)}2] (6) and the known cyclometallated complex [Th{N(CH2CH2NSiPri3)2(CH2CH2SiPri2CHMeCH2)}] (4) by thermolysis; thereby, providing an unprecedented example of reductive cycloaddition reactivity in the chemistry of 2âphosphaethynolate. This has permitted us to isolate intermediates that might normally remain unseen. We have debunked an erroneous assumption of a concerted fragmentation process for (OCP)â, rather than cycloaddition products that then decompose with [Th(TrenTIPS)O]â essentially acting as a protecting then leaving group. In contrast, when KC8 or CsC8 were used the phosphinidiide CâH bond activation product [{Th(TrenTIPS)}Th{N(CH2CH2NSiPri3)2[CH2CH2SiPri2CH(Me)CH2C(O)ÎźâP]}] (3) and the oxo complex [{Th(TrenTIPS)(ÎźâOCs)}2] (7) were isolated
Isolation of elusive HAsAsH in a crystalline diuranium(IV) complex
The HAsAsH molecule has hitherto only been proposed tentatively as a short-lived species generated in electrochemical or microwave-plasma experiments. After two centuries of inconclusive or disproven claims of HAsAsH formation in the condensed phase, we report the isolation and structural authentication of HAsAsH in the diuranium(IV) complex [{U(TrenTIPS)}2(Îź-Ρ2:Ρ2-As2H2)] (3, TrenTIPS=N(CH2CH2NSiPri3)3; Pri=CH(CH3)2). Complex 3 was prepared by deprotonation and oxidative homocoupling of an arsenide precursor. Characterization and computational data are consistent with back-bonding-type interactions from uranium to the HAsAsH Ď*-orbital. This experimentally confirms the theoretically predicted excellent Ď-acceptor character of HAsAsH, and is tantamount to full reduction to the diarsane-1,2-diide form
Synthesis and characterisation of halide, separated ion pair, and hydride cyclopentadienyl iron bis(diphenylphosphino)ethane derivatives
Treatment of anhydrous FeXâ (X = Cl, Br, I) with one equivalent of bis(diphenylphosphino)ethane (dppe) in refluxing THF afforded analytically pure white (X = Cl), light green (X = Br), and yellow (X = I) [FeXâ(dppe)]n (X = Cl, I; Br, II; I, III). Complexes IâIII are excellent synthons from which to prepare a range of cyclopentadienyl derivatives. Specifically, treatment of IâIII with alkali metal salts of Câ
Hâ
(Cp, series 1), Câ
Meâ
(Cp*, series 2), Câ
HâSiMeâ (Cpâ˛, series 3), Câ
Hâ(SiMeâ)â (Cpâ˛â˛, series 4), and Câ
Hâ(But)â (Cptt, series 5) afforded [Fe(Cpâ )(Cl)(dppe)] 1Clâ5Cl, [Fe(Cpâ )(Br)(dppe)] 1Brâ5Br, and [Fe(Cpâ )(I)(dppe)] 1Iâ5I (Cpâ = Cp, Cp*, Cpâ˛, Cpâ˛â˛, or Cptt). Dissolution of 1Iâ5I in acetonitrile, or treatment of 1Clâ5Cl with MeâSiI in acetonitrile (no halide exchange reactions were observed in other solvents) afforded the separated ion pair complexes [Fe(Cpâ )(NCMe)(dppe)][I] 1SIPâ5SIP. Attempts to reduce 1Clâ5Cl, 1Brâ5Br, and 1Iâ5I with a variety of reductants (Li-Cs, KCâ, Na/Hg) were unsuccessful. Treatment of 1Clâ5Cl with LiAlHâ gave the hydride derivatives [Fe(Cpâ )(H)(dppe)] 1Hâ5H. This report provides a systematic account of reliable methods of preparing these complexes which may find utility in molecular wire and metalâmetal bond chemistries. The complexes reported herein have been characterised by X-ray diffraction, NMR, IR, UV/Vis, and MĂśssbauer spectroscopies, cyclic voltammetry, density functional theory calculations, and elemental analyses, which have enabled us to elucidate the electronic structure of the complexes and probe the variation of iron redox properties as a function of varying the cyclopentadienyl or halide ligand
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