5 research outputs found

    MAIN GROUP AND TRANSITION METAL-BASED CHELATES FOR PET APPLICATIONS

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    [AlCl3(BnMe2-tacn)] was radiolabelled by Cl/18F halide exchange reactions in the presence of 2.99 mol. equiv. of KF at pH 4 CH3CO2Na buffer solution with addition of 18F-target water, to give [Al18F19F2(BnMe2-tacn)] with RCY up to 24 %. The radio-product was purified through a simple SPE purification protocol in 99 % RCP and it shows excellent stability in 50 % EtOH/PBS solution for >3h.[GaF3(BnMe2-tacn)] can be successfully 18F-radiolabelled using a precursor concentration as low as 27 nM through 18F/19F isotopic exchange reactions, using 18F-target water in a 75 % MeCN/H2O solution, in good RCYs (37 ± 5 %) within 10 minutes. The RCY of the reaction starting with a precursor concentration of 268 nM and 2.68 μM were 66 ± 4 % and 73 ± 4 %, respectively. [Ga18F19F2(BnMe2-tacn)] was purified through an SPE cartridge and formulated in 20 % EtOH/water solution showing a RCP of 99 % at t = 0 which decreases to 77-88 % after 2 h. The effect on the RCP of temperature, pH, addition of ascorbic acid, an excess of Cl− or OH− in solution were investigated.The coordination chemistry of Group 13 metal fluorides towards O-donor ligands was developed. The MF3·3H2O (M = Al, Ga, In) were synthesised and the more readily soluble molecular species [MF3(OH2)2(DMSO)] (M = Al, Ga) were used as synthons for reactions with other ligands. The complexes were characterised by 1H, 19F{1H}, microanalysis and IR spectroscopy. The stability of [GaF3(OH2)2(dmso)] was tested to determine whether it could be used as a radiolabelling precursor.The coordination chemistry of the Group 3, Sc(III), Y(III), and lanthanides, La(III) and Lu(III), trichlorides and trifluorides (Sc only) towards neutral N-donor ligands was developed. The complexes were characterised by 1H, 19F{1H} and 45Sc NMR spectroscopy, as appropriate, together with IR spectroscopy and microanalysis. The crystal structures of [ScCl3(terpy)], [MCl3(terpy)(OH2)] (M = Y, Lu), [YI3(Me3-tacn)]·MeCN, [{YI2(Me3-tacn)}2(μ-O)]·MeCN, [{La(terpy)(OH2)Cl2}2(μ-Cl)2], [ScF2Cl(Me3-tacn)] and [ScF2(Me3-tacn)(μ-F)SnMe3Cl] are reported. The first three examples of scandium fluoride complexes with neutral ligands are reported, [ScF3(BnMe2-tacn)], [ScF3(Me3-tacn)] and [ScF3(terpy)]. These complexes were obtained by halide exchange reactions using the trichloride analogues, by reaction with [Me4N]F or Me3SnF as the fluoride source.The first row transition metal fluorides chemistry with terpy and Me3-tacn was explored in order to identify promising systems for 18F radiolabelling. The complexes [MF3(L)] (M = Cr, Mn, Fe, Co; L = Me3-tacn, terpy) were synthesised and fully characterised by UV-vis and IR spectroscopy, microanalysis, and, for the diamagnetic [CoF3(L)], using 1H, 19F{1H} and 59Co NMR spectroscopy. Single crystal X-ray analyses are reported for [MF3(Me3-tacn)] (M = Mn, Co). Stability tests on [MF3(Me3-tacn)] (M = Cr, Mn, Fe, Co) and [CrF3(terpy)] were performed and the Cl/19F halide exchange reactions using [CrCl3(Me3-tacn)] and [FeCl3(Me3-tacn)] were also carried out with added [Me4N]F. The halide exchange reactions allowed partial Cl/F exchange for the Cr(III) systems, and proved to be successful in forming [FeF3(Me3-tacn)] cleanly

    Systematics of boron halide complexes with dichalcogenoether ligands – synthesis, structures and reaction chemistry

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    The complexes [BX3(μ-L−L)BX3] (X = Cl, Br, I; L−L = EtS(CH2)2SEt, MeSe(CH2)2SeMe), [BX′3{o-C6H4(SMe)2}] (X’ = Cl, I), [(BBr3)2{o-C6H4(SMe)2}], [(BBr3)2{o-C6H4(SeMe)2}] and [BI3{o-C6H4(SeMe)2}] have been prepared as moisture-sensitive pale solids by reaction of the appropriate BX3 with the dichalcogenoether in anhydrous n-hexane solution, and characterised by microanalysis, IR and multinuclear (1H, 11B, 77Se{1H}) NMR spectroscopy. In contrast, the [BF3(μ-L−L)BF3], [(BF3)2{o-C6H4(SMe)2}] and [(BF3)2{o-C6H4(SeMe)2}], made from BF3 and the neat ligands, are viscous oils which have a significant vapour pressure of BF3 at ambient temperatures. X-ray crystal structures are reported for [BX3{μ-EtS(CH2)2SEt}BX3] (X = Cl, Br, I), [BBr3{μ-MeSe(CH2)2SeMe}BBr3], [BCl3{o-C6H4(SMe)2}] and [(BBr3)2{μ-o-C6H4(SeMe)2}]. The complexes [(BX3)2{MeTe(CH2)3TeMe}] (X = F, Cl, Br) have been identified in solution by multinuclear NMR spectroscopy, but decompose rapidly, whilst o-C6H4(TeMe)2 decomposes immediately on contact with BBr3 or BCl3. Dealkylation of some of the chalcogenoether ligands at room temperature by BI3, to yield complexes including [BI2{o-C6H4S(SMe)] and [BI2{o-C6H4Se(SeMe)], has been identified and the X-ray structure of [BI2{o-C6H4Se(SeMe)] determined. The trends in behaviour along the series of boron halides and with the various chalcogenoethers are described and compared with the behaviour of BX3 with neutral phosphorus and arsenic donor ligands (Burt et al., Inorg. Chem., 2016, 55, 8852) and with [BX3(EMe2)] (E = S, Se, Te) (Okio et al., J. Organometal. Chem., 2017, 848, 232)

    Complexes of molybdenum(VI) oxide tetrafluoride and molybdenum(VI) dioxide difluoride with neutral N- and O-donor ligands

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    [MoOF4(MeCN)], prepared from reaction of MoF6 with (Me3Si)2O in anhydrous MeCN solution, reacts with the neutral O-donor ligands, thf, Ph3PO, Me3PO, dmf and dmso, (L) in a 1:1 molar ratio under rigorously anhydrous conditions to form six-coordinate [MoOF4(L)], which have been characterised by microanalysis, IR, 1H, 19F{1H} and 95Mo NMR spectroscopy. In the presence of moisture the major products are [MoO2F2(L)2], which can be made directly by reaction of [MoOF4(L)] with a further equivalent of L and (Me3Si)2O. [MoOF4(MeCN)] and 2,2′-bipyridyl produce the insoluble [MoOF4(bipy)], which is probably 7-coordinate. Ph3AsO is quantitatively converted to Ph3AsF2 by [MoOF4(MeCN)], and soft ligands, including Me2S, Me3P and Me3As, reduce the oxide fluoride on contact. Unstable [MoO2F2(MeCN)2] has also been prepared and the X-ray structure of [MoO2F2(MeCN)2]·MeCN is reported. X-ray crystal structures are reported for [MoOF4(Ph3PO)], [MoO2F2(Ph3PO)2], [MoO2F2(Me3PO)(H2O)] and [Mo2O4F2(μ-F)2(Me3PO)2]. Comparisons with the corresponding chemistries of WOF4 and WO2F2 are described

    Group 3 metal trihalide complexes with neutral N-donor ligands – exploring their affinity towards fluoride

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    Fluorination of [ScCl3(Me3-tacn)] (Me3-tacn = 1,4,7-trimethyl-1,4,7-triazacyclononane) and [ScCl3(BnMe2-tacn)] (BnMe2-tacn = 1,4-dimethyl-7-benzyl-1,4,7-triazacyclononane) by Cl/F exchange with 3 mol. equiv. of anhydrous [NMe4]F in CH3CN solution yields the corresponding [ScF3(R3-tacn)] (R3 = Me3 or BnMe2). These are the first examples of scandium fluoride complexes containing neutral co-ligands. The fluorination occurs stepwise, and using a deficit of [NMe4]F produced [ScF2Cl(Me3-tacn)]. Attempts to fluorinate [YCl3(Me3-tacn)], [YI3(Me3-tacn)], [LaCl3(Me3-tacn)(OH2)] or [MCl3(terpy)] (M = Sc, Y or La; terpy = 2,2′:6′2′′-terpyridyl) using a similar method were unsuccessful, due to the Cl/F exchange being accompanied by loss of the neutral ligand from the metal centre. Fluorination of [ScCl3(Me3-tacn)] or [ScCl3(terpy)] with Me3SnF was also successful. The products were identified as the very unusual heterobimetallic [Sc(Me3-tacn)F2(μ-F)SnMe3Cl] and [Sc(terpy)F(μ-F)2(SnMe3Cl)2], in which the Me3SnCl formed in the reaction behaves as a weak Lewis acid towards the scandium fluoride complex, linked by Sc–F–Sn bridges. [Sc(terpy)F(μ-F)2(SnMe3Cl)2] decomposes irreversibly in solution but, whilst multinuclear NMR data show that [Sc(Me3-tacn)F2(μ-F)SnMe3Cl] is dissociated into the [ScF3(Me3-tacn)] and Me3SnCl in CH3CN solution, the bimetallic complex reforms upon evaporation of the solvent. The new scandium fluoride complexes and the chloride precursors have been characterised by microanalysis, IR and multinuclear NMR (1H, 19F, 45Sc) spectroscopy as appropriate. X-ray crystal structures provide unambiguous evidence for the identities of [Sc(Me3-tacn)F2(μ-F)SnMe3Cl], [ScF2Cl(Me3-tacn)], [YI3(Me3-tacn)], [{YI2(Me3-tacn)}2(μ-O)], [ScCl3(terpy)], [YCl3(terpy)(OH2)], and [{La(terpy)(OH2)Cl2}2(μ-Cl)2]. Once formed, the [ScF3(R3-tacn)] complexes are stable in water and unaffected by a ten-fold excess of Cl− or MeCO2−, although they are immediately decomposed by excess F−. The potential use of [ScF3(R3-tacn)] type complexes as platforms for 18F PET (positron emission tomography) radiopharmaceuticals is briefly discussed. Attempts to use the Group 3 fluoride “hydrates”, MF3·xH2O, as precursors were unsuccessful; no reaction with R3-tacn or terpy occurred either on reflux in CH3CN or under hydrothermal conditions (H2O, 180° C, 15 h). PXRD data showed that these “hydrates” actually contain the anhydrous metal trifluorides with small amounts of surface or interstitial water
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