80 research outputs found
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
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
Evidence for ligand- and solvent-induced disproportionation of uranium(IV)
From Springer Nature via Jisc Publications RouterHistory: received 2020-05-14, accepted 2021-07-21, registration 2021-07-28, pub-electronic 2021-08-10, online 2021-08-10, collection 2021-12Publication status: PublishedFunder: RCUK | Engineering and Physical Sciences Research Council (EPSRC); doi: https://doi.org/10.13039/501100000266; Grant(s): EP/K024000/1, EP/M027015/1, EP/P001386/1, EP/S033181/1Funder: Leverhulme Trust; doi: https://doi.org/10.13039/501100000275; Grant(s): RF-2018-545\4Funder: Royal Society; doi: https://doi.org/10.13039/501100000288; Grant(s): UF110005Abstract: 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. This is facilitated by benzene, but not toluene, since benzene engages in a redox reaction with the uranium(III)-amide product to give uranium(IV)-amide and reduced arene. These disproportionations occur with potassium, rubidium, and cesium counter cations, but not lithium or sodium, reflecting the stability of the corresponding alkali metal-arene by-products. This reveals an exceptional level of ligand- and solvent-control over a key thermodynamic property of uranium, and is complementary to isolobal uranium(V)-oxo disproportionations, suggesting a potentially wider prevalence possibly with broad implications for the chemistry of uranium
Synthesis and Characterisation of Molecular Polarised-Covalent Thorium-Rhenium and -Ruthenium Bonds
Separate reactions of [Th{N(CH2CH2NSiMe2But)2(CH2CH2NSi(Me)(But)(Ο-CH2)]2 (1) with [Re(Ρ5-C5H5)2(H)] (2) or [Ru(Ρ5-C5H5)(H)(CO)2] (3) produced, by alkane elimination, [Th(TrenDMBS)Re(Ρ5-C5H5)2] (ThRe, TrenDMBS = {N(CH2CH2NSiMe2But)3}3-), and [Th(TrenDMBS)Ru(Ρ5-C5H5)(CO)2] (ThRu), which were isolated in crystalline yields of 71% and 62%, respectively. Complex ThRe is the first example of a molecular Th-Re bond to be structurally characterised, and ThRu is only the second example of a structurally authenticated Th-Ru bond. By comparison to isostructural U-analogues, quantum chemical calculations, which are validated by IR and Raman spectroscopic data, suggest that the Th-Re and Th-Ru bonds reported here are more ionic than the corresponding U-Re and U-Ru bonds
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