2923-18-4Relevant articles and documents
A novel approach to RE-OR bond from in situ reaction of rare earth triflates and sodium alkoxides: A versatile catalyst for living ring-opening polymerization of ε-caprolactone
You, Lixin,Shen, Zhiquan,Kong, Jie,Ling, Jun
, p. 2404 - 2410 (2014)
A series of rare earth triflates (RE(OTf)3, RE = Sc, Y and Lu) were used for the first time as moisture-stable precursors to generate rare earth alkoxide complexes through an in situ reaction with sodium alkoxides (NaOR) in tetrahydrofuran. 1H NMR and 13C NMR results confirmed the fast ligands exchange process and the formation of rare earth-oxygen (RE-OR) bond. The in situ formed catalysts displayed high reactivity toward living ring-opening polymerization (ROP) of ε-caprolactone (CL). For instance, Lu(OTf)3/sodium isopropoxide (NaOiPr)-catalyzed ROP of CL with the [CL]0/[NaO iPr]0/[Lu(OTf)3]0 feeding ratio of 300/3/1 produced poly(ε-caprolactone) (PCL) with controlled molecular weight (Mn,exp = 11.9 kDa vs Mn,theo = 11.8 kDa) and narrow polydispersity (PDI) of 1.08 within 3 min at 25°C. The kinetic studies and chain extension confirmed the controlled/living nature for the Lu(OTf)3/NaOiPr-catalyzed ROP of CL. In addition, end-functionalized PCLs bearing vinyl or alkynyl group with narrow PDIs were obtained by using functional sodium alkoxides in the presence of Lu(OTf) 3. 1H NMR and MALDI-ToF MS analyses of the obtained PCLs clearly indicated the presence of the residue of OR groups at the chain ends. A coordination-insertion polymerization mechanism was proposed including a fast ligand exchange between Lu(OTf)3 and NaOR giving the respective lutetium alkoxide complexes, and a CL insertion into RE-OR bond via acyl-oxygen cleavage.
New method of beta-NaYF4: Yb3+, Er3+ synthesis by using beta-cyclodextrin
Fedorova, Anna A.,Fedulin, Andrey I.,Morozov, Igor V.
, p. 173 - 177 (2015)
Abstract The novel method of synthesis of the hexagonal modification beta-NaYF4 doped with Yb3+ (17 at.%) and Er3+ (3 at.%) using beta-cyclodextrin is proposed. Complex fluorides were prepared by decomposition of the mixture of metal fluoroacetates hydrates with and without addition of beta-cyclodextrin and were investigated by X-ray diffraction, energy dispersive X-ray analysis, scanning and transmission electron microscopy. The samples prepared by adding beta-cyclodextrin in the reaction mixture are single phase and have a hexagonal structure. At the same time, decomposition of the mixture of metal trifluoroacetates hydrates without beta-cyclodextrin is accompanied by pyrohydrolysis, leading to a contamination of the products by impurities of yttrium oxyfluorides and sodium fluoride. So a new synthetic approach proposed in this work allows to obtain pure complex fluorides with homogeneous distribution of elements and with homogeneous pore distribution.
Heterometallic trinuclear oxo-centered clusters as single-source precursors for synthesis of stoichiometric monodisperse transition metal ferrite nanocrystals
Brennessel, William W.,Knowles, Kathryn E.,Sanchez-Lievanos, Karla R.,Tariq, Mehrin
, p. 16348 - 16358 (2020)
The use of heterobimetallic metal complexes as molecular single-source precursors is a promising strategy for the targeted synthesis of phase-pure stoichiometric ternary metal oxide nanocrystals. However, the design and synthesis of these precursors is not trivial and can require considerable effort. Using spinel metal ferrite nanocrystals of formula MFe2O4 (M = Fe2+, Co2+, Ni2+, Cu2+, and Zn2+) as a model system, this paper evaluates the efficacy of the single-source precursor approach by comparing directly nanocrystals synthesized from the solvothermal reaction of heterobimetallic trinuclear oxo-bridged clusters of formula MIIFeIII2(μ3-O)(μ2-O2CR)6(H2O)3, R = CF3 to nanocrystals synthesized from the solvothermal reaction of stoichiometric mixtures of multi-source precursors, such as metal acetate or nitrate salts. For each M explored here, the clusters form phase-pure MFe2O4 nanocrystals with significantly narrower size distributions than nanocrystals synthesized from multi-source-precursors. In the case of M = Cu, the multi-source metal salt precursors produce a mixture of CuO and CuFe2O4. Additionally, changing the electronic nature of the R-group on the bridging carboxylate ligand from electron withdrawing (CF3) to electron donating (CH3 or C(CH3)3) decreases the average diameter of the resulting nanocrystals by a factor of two. The cluster molecules therefore offer superior control over both morphology and composition for transition metal ferrite nanocrystals. We hypothesize that this remarkable performance arises from the presence of pre-formed M2+-O-Fe3+ moieties in the cluster molecules that enable direct nucleation of MFe2O4 and preclude nucleation of binary oxide impurities.
Alkali metal trifluoroacetates for the nucleophilic trifluoromethylation of fullerenes
Bogdanov, Viktor P.,Dmitrieva, Veronika A.,Ioutsi, Vitaliy A.,Belov, Nikita M.,Goryunkov, Alexey A.
, (2019/07/17)
Fullerene C60 readily reacts with potassium and cesium trifluoroacetates yielding C60(CF3)–M+ salts, and subsequent acid hydrolysis gives ortho-C60(CF3)H. The reaction rate and the probability of the alternative reaction pathways strongly depend on the particular metal cation. Thus, the reactivity increases in the order Li 2- rather than CF3-functionalization of the fullerene, in good accordance with the hard/soft acids and bases theory. The nucleophilic trifluoromethylation is found to be applicable to other pristine fullerenes like C70 as well as to fullerene derivatives like p7mp-C70(CF3)10. It enables selective preparation of low trifluoromethylated fullerenes via regioselective consecutive trifluoromethylation under accurately controlled solution-phase conditions.
