Triflate Compounds Research Articles

Fabrication, swift heavy ion irradiation, and damage analysis of lanthanide targets

Abstract One limiting factor in progress in the discovery and study of new superheavy elements (SHE) is the maximum achievable thickness and irradiation stability of current generation actinide targets. The desired thickness of targets, using full excitation function widths, cannot be achieved with current target technology, especially the widely used molecular plating (MP). The aim of this study was to transfer progress in the electrochemistry of lanthanides and actinides to the production of targets. Here, we report on the production of lanthanide targets using anhydrous electrochemical routes. In a first irradiation series, thulium thin films with areal densities up to 1800 μg/cm2 were produced using anhydrous triflate compounds and subjected to irradiation tests, using 6.0 MeV/u 48Ca ions at a fluence of 3.9 × 1014 ions/cm2 and 8.6 MeV/u 197Au ions at fluences in the range of 3.0 × 1011 to 1.0 × 1013 ions/cm2. The thin films were characterised before and after the irradiations using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX).

Bis(phenanthrolinyl)amine manganese complexes with pseudo-trigonal prismatic geometry

Two manganese(II) complexes supported by an isoamyl-substituted bis(phenanthrolinyl)amine ligand have been prepared and characterized. Determination of the molecular structures through X-ray crystallography demonstrated that the triflate compound crystallizes as a monomeric species with an outer-sphere anion, while the chloride complex exists as a dimer containing bridging chloride ligands in the solid state. Importantly, these structures revealed a coordination environment about the metal centre that is best described as pseudo-trigonal prismatic in both cases. Computational analysis found an optimized geometry for the triflate complex in a high-spin state that is consistent with the experimental observations, while the low-spin calculation showed a significant shift toward octahedral geometry. These results and their contrast with previously reported data provide evidence for the influence of electronic structure and metal ion size on molecular geometry in this system.

Synthesis and characterization of partially substituted NHC supported alane adducts using triflate or chloride salts

Use of an aldiminium-based triflate salt as group transfer reagent to an N-heterocyclic carbene (NHC) adduct with alane [(IPr)AlH3] (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazole-2-ylidene) led to the substitution of a hydride by triflate and subsequently to the formation of [(IPr)AlH2OTf] (1), which is the first structurally characterized aluminum dihydride triflate compound and the first (trifluoromethanesulfonyl)oxyalane NHC adduct. The related reaction with aldiminium-based chloride salt resulted in similar substitution and formation of mixed products [(IPr)AlH2Cl] and [(IPr)AlHCl2], which co-crystallized in the form of [(IPr)AlH3−xClx], x = 1, 2 (2). This proves that aldiminium-based salts are suitable reagents in alane chemistry. In addition, the adduct [(IPr)AlCl3] (4) was also prepared from AlCl3 and IPr carbene.

Kinetics and photophysical behavior of the P,N-ReI complex [P,N-{(C6H5)2(C5H4N)P}Re(CO)3(O-O3SCF3)]: A directly coordinated (and labile) triflate

The reaction of [P,N-{(C6H5)2(C5H4N)P}Re(CO)3Br] (RePNBr) with silver triflate leads to the complex [P,N-{(C6H5)2(C5H4N)P}Re(CO)3(O-CF3SO3)] (RePNTfO) with moderate yield. This new P,N-ReI triflate compound contains the anion directly coordinated to the metal, completing an octahedral environment. RePNTfO displays in dichloromethane (DCM) solution an irreversible oxidation about +1.35V and three irreversible reduction processes at −1.38V, −2.03V and −2.30V. Oxidation has been attributed to the ReI/ReII couple, while the reduction corresponds to PN-ligand processes, which is consistent with those computed by means of DFT. The absorption spectrum of RePNTfO in DCM displays a maximum at 295nm (ε=7.1×103M−1cm−1) and a shoulder around 350nm (ε=1.8×103M−1cm−1), which have been assigned to intraligand (π→π∗) and metal to ligand charge transfer (MLCT, dπ→π∗) transitions with the help of DFT/TDDFT. Excitation of RePNTfO in DCM at 350nm leads to an emission spectrum centered at 535nm. The analysis of the variation of the absorption and emission spectra in coordinating solvents compared to non-coordinating DCM, DFT/TDDFT calculations modeling and ELF analysis suggests for coordinating solvents that triflate ligand is replaced in the coordination sphere of ReI in solution. Kinetics of the exchange of triflate by bromide measured in DCM at different temperatures allowed to estimate the Eyring parameters: ΔH≠, ΔS≠ and ΔG≠, 50.8kJmol−1, −109.6JK−1mol−1 and 83.5kJmol−1 respectively. The high negative entropy is indicative of a compact transition state, compatible with an associative mechanism, Ia, for the exchange.

The Role of Ancillary Ligands on the Reactivity of Monocyclopentadienyl Tantalum Complexes with Water

The reaction of [TaCp*Me3(OTf)] with chelidamic acid yields the carboxylate derivative [TaCp*Me(OTf)((OOC)2py(OH)-κ3-O,N,O)] (1) that reacts with water to yield the cationic dimetallic complex [{TaCp*((OOC)2py(OH)-κ3-O,N,O)}2(μ2-OH)3](OTf) (2). In an analogous procedure, the reaction of [TaCp*Me3(OTf)] with diglycolic acid renders the triflate compound [TaCp*Me{(OOCCH2)2O}-κ3-O,O,O)(OTf)] (4). Citric acid (CITH4) reacts with [TaCp*Me4] and water to give the dimetallic complex [{TaCp*(CITH)(OH2)}(μ-O){TaCp*(CITH2)(OH)}] (6). Compound [TaCp*Me3(OTf)] reacts with an excess of water in CH2Cl2 to give the trimetallic tantalum hydroxide [{TaCp*(OH)(OH2)}3(μ3-OH)(μ2-O)3](OTf)2 (7). Complexes 2, 6 and 7 have been studied by X-ray diffraction.

Monocyclopentadienyl titanium complexes supported by functionalized Shiff Base ligands

The titanium derivatives [TiCp * Me(κ3-ONO–OOCPhNCHPhO)] (1), [TiCp * Me(κ3-ONO–OCH2PhNCHPhO)] (2) and [TiCp * Me(κ3-ONS–SPhNCHPhO)] (3) have been synthesized by reaction of [TiCp * Me3] (Cp* = η5-C5Me5) with 2-(salicylideneamino)benzoic acid, 2-(hydroxybenzyl)salicylideneamino or 2-(salicylideneamino)thiophenol, respectively, in a 1:1 M ratio. The reaction of [TiCp * Me3] with and 2-(salicylideneamino)thiophenol in 1:2 M ratio yields the titanium compound [TiCp * Me(κ3-ONS–SPhNCHPhO)(κ1-O-PhCHNHPhS)] (5) Complexes 1, 2 and 3 react with tBuNC to yield the iminoacyl-containing compounds [TiCp * (η2-CN–MeCNtBu)(κ3-ONO–OOCPhNCHPhO)] (6), [TiCp * (η2-CN–MeCNtBu)(κ3-ONO–OCH2PhNCHPhO)] (7) and [TiCp * (η2-CN–MeCNtBu)(κ3-ONS–SPhNCHPhO)] (8). Compounds 7 and 8 can be protonated with triflic acid to yield the aminocarbene derivatives (9) and (10), respectively. Moreover, the reaction of complexes 1–3 with triflic acid renders the corresponding triflate compounds [TiCp * (κ3-ONO–OOCPhNCHPhO)(OTf)] (11), [TiCp * (κ3-ONO–OCH2PhNCHPhO)(OTf)] (12) and [TiCp * (κ3-ONS–SPhNCHPhO)(OTf)] (13). The reaction of 1 or 2 with B(C6F5)3 in a 1:1 M ratio yields the carboxylate adduct [TiCp * Me(κ3-ONO–OOCPhNCHPhO·B(C6F5)3)] (14) or the cationic derivative. [TiCp * (κ3-ONO–OCH2PhNCHPhO)]2[MeB(C6F5)3)]2 (15), respectively. The molecular structures of complexes 2, 5, 6, 13 and 15 have been established by X-ray diffraction methods.

Synthesis and characterization of complexes containing Ti–O–Si moieties. Catalytic activity in olefin epoxidation

Reaction of [Cp*TiMe3] with O(SiPh2OH)2 yields the titanium siloxide derivative [Cp*TiMe{(OSiPh2)2O}]. Complex reacts with H2O to yield the corresponding oxo-titanium derivative [(Cp*Ti{(OSiPh2)2O})2(micro-O)]. The molecular structure of complex has been established by X-ray diffraction. Complex reacts with triphenylsilanol to give the asymmetric titanium siloxide [Cp*Ti(OSiPh3){(OSiPh2)2O}]. Treatment of the dinuclear titanium compound [(Cp*TiCl2)2(micro-O)] with an equimolar amount of O(SiPh2OH)2 yields complex [(Cp*TiCl)2{micro-(OSiPh2)2O}(micro-O)] in which the disiloxide moiety is bridging two titanium atoms. The structure of has been determined by X-ray diffraction. Reaction of [Cp*TiMe3] with HOSiPh3 yields the titanium triphenylsiloxide [Cp*TiMe2(OSiPh3)]. Complex reacts with water to yield [{Cp*TiMe(OSiPh3)}2(micro-O)]. The triflate compound [Cp*Ti(OSiPh3)2(OTf)] can be prepared by reaction of with HOTf and triphenylsilanol. We have tested the catalytic activity of some of the complexes in the epoxidation of cyclohexene.

Acylation of 2-methoxynaphthalene with acetic anhydride over silica-embedded triflate catalysts

Silica sol–gel immobilized triflate compounds like La(OTf) 3, tert-butyldimethylsilyl trifluoromethanesulfonate (BDMST) and triflic acid (HOTf) were tested in the acylation of 2-methoxynaphthalene with acetic anhydride, leading to 1-acetyl-2-methoxynaphthalene as the major product. The reaction only proceeded with good yields on BDMST and HOTf catalysts, while La(OTf) 3 presented a low activity. For BDMST in solvent-free conditions, the resulting TOF was superior to that reported in literature for other heterogeneous catalysts and even for homogeneous triflates. The rates of reactions in various solvents strongly depend on the donor number of these solvents.

Two different isomers of tetrahedrally distorted square-planar Cu(II) triflate compounds with 2-guanidinobenzimidazole; synthesis, X-ray and spectroscopic characterisation

In this study we report two isomers of Cu(2gb) 2(CF 3SO 3) 2 (in which 2gb=2-guanidinobenzimidazole), i.e. purple α-Cu(2gb) 2(CF 3SO 3) 2 ( 1) and green β-Cu(2gb) 2(CF 3SO 3) 2 ( 2) compounds. The Cu(II) atoms adopt a distorted tetrahedral geometry in both compounds. The difference between both isomers is the position of the triflate anions. In compound ( 2) one of the triflate anions is at a long semi-coordination distance, while in compound ( 1) the anions are at a much longer distance. That fact implies also that the hydrogen bonding system and the packing is different between the two compounds. The characterisation for both isomers has been performed by X-ray crystallography and infrared spectroscopy. A distortion towards tetrahedral is observed for both Cu(II) compounds with dihedral torsion angles at around 40° in both cases.

Influence of lanthanide triflate compounds on formation of networks from DGEBA and γ‐butyrolactone

AbstractDiglycidylether of bisphenol A (DGEBA) was cured with γ‐butyrolactone (γ‐BL) using different lanthanide triflates as catalysts. Fourier transform infrared spectroscopy was used to study the different evolutions of the four elemental processes that took place during curing with lanthanum and ytterbium triflates. The greatest differences among the lanthanides were in oxophilicity and Lewis acidity. Differences in the coordination ability of the metal to the monomers were shown and according to the Pearson theory, were related to their different characteristics. Differences in the reactivity of the systems were related to the differences in the Lewis acidity of the initiators. The evolution of the contraction during curing using different lanthanide triflates was monitored by thermomechanical analysis. All systems showed that contraction took place in two stages and that there was an intermediate region, associated with gelation, with no contraction. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3782–3791, 2004

Palladium-Catalysed Coupling Reactions: (Z)-Vinyl (N,N-Diisopropyl)carbamate Group as an Efficient Precursor of a (Z)-Vinyl Triflate Function

A (Z)-vinyl (diisopropyl)carbamate group, generated from a Hoppe allylation reaction, was easily transformed either into the corresponding (Z)-vinyl phosphate or (Z)-vinyl triflate function in good yield and high selectivity. It was also shown that the resulting (Z)-vinyl triflate compound could be utilized successfully in palladium-catalysed coupling reactions with vinyl-, phenyl- and acetylenic tin derivatives, without loss of the (Z)-geometry of the double bond.

Synthesis and Reactivity of Aryl- and Alkyl-Rhenium(V) Imido−Triflate Compounds: An Unusual Mechanism for Triflate Substitution

Treatment of the d2 rhenium tolylimido complex TpRe(NTol)X2 with RMgX, RLi, or organozinc reagents yields TpRe(NTol)(R)X [R = Ph, Me, Et, i-Pr, n-Bu; X = Cl or I; Tol = p-tolyl; Tp = hydrotris(1-pyrazolyl)borate] or TpRe(NTol)R2 (R = Ph, Me). Iodide for triflate metathesis with AgOTf yields TpRe(NTol)(X)OTf [X = Ph, Et, Cl, OTf (=OSO2CF3)]. Reaction of TpRe(NTol)(Et)I with excess rather than stoichiometric AgOTf generates the ethylene hydride cation [TpRe(NTol)(η2-C2H4)(H)][OTf], which slowly rearranges by ethylene insertion to form TpRe(NTol)(Et)OTf. Treatment of TpRe(NTol)(Ph)I with AgPF6 gives not iodide abstraction but rather [{TpRe(NTol)(Ph)I}2Ag][PF6], with two Re−I−Ag linkages. Excess pyridine (py) slowly displaces triflate in TpRe(NTol)Ph(OTf) (11) to give [TpRe(NTol)Ph(py)][OTf]. The reaction is first-order in 11 and first-order in py. Triflate substitution is similarly slow in the oxo-Tp* derivative, Tp*Re(O)Ph(OTf) [Tp* = HB(3,5-Me2pz)3]. These reactions are many orders of magnitude slower than...

Preparation, characterisation and reactivity of a series of classical and non-classical rhenium hydride complexes ‡

Hydride complexes [ReH(CO)4L] 1, [ReH(CO)3L2] 2, [ReH(CO)2L3] 3 and [ReH(CO)L4] 4 [L = P(OEt)3 a, PPh(OEt)2 b, PPh2(OEt) c or PPh2(OMe) d] were prepared by treating [ReH(CO)5] with the appropriate phosphite under UV irradiation or reflux. The complexes were characterised by IR, 1H, 13C and 31P NMR spectroscopy and by crystal structure determinations of 1d and 2d. Protonation of the monocarbonyls [ReH(CO)L4] 4 in CD2Cl2 with HBF4·Et2O resulted in an equilibrium mixture of the classical dihydride complexes [ReH2(CO)L4]+BF4– and their non-classical tautomers [Re(η2-H2)(CO)L4]+BF4–. The dihydride [ReH2(CO){PPh(OEt)2}4]BPh4 was also isolated as a solid by protonation of [ReH(CO){PPh(OEt)2}4] in ethanol. Thermally unstable [Re(η2-H2)(CO)4L]+, [Re(η2-H2)(CO)3L2]+ and [Re(η2-H2)(CO)2L3]+ 7 cations were also prepared by protonation of the corresponding monohydrides 1, 2 and 3 and fully characterised in solution. The unsaturated complexes [Re(CO)2L3]BPh4 and [Re(CO)L4]BPh4 11 and the triflate [Re(η1-OSO2CF3)(CO)3L2] were obtained from the η2-H2 derivatives by evolution of H2. The new complexes [Re(CCPh)(CO)3L2], [Re(CCPh)(CO)L4] 13, [Re(4-MeC6H4CN)(CO)2L3]BPh4, [Re(4-MeC6H4NC)(CO)2L3]BPh4 and [Re(4-MeC6H4NC)(CO)L4]BPh4 were prepared by treating the triflate compounds or the unsaturated compounds [Re(CO)2L3]BPh4 and [Re(CO)L4]BPh4 with Li+CCPh– or with the appropriate ligand.

Selective Oxidation of the Alkyl Ligand in Rhenium(V) Oxo Complexes

Rhenium(V) oxo alkyl triflate compounds (HBpz3)ReO(R)OTf [R = Me (4), Et (5), n-Bu (6); HBpz3 = hydrotris(1-pyrazolyl)borate; OTf = OSO2CF3, triflate] are formed on sequential reaction of (HBpz3)ReOCl2 with dialkyl zinc reagents and AgOTf. These triflate compounds are rapidly oxidized at ambient temperatures by oxygen atom donors pyridine N-oxide (pyO) and dimethyl sulfoxide (DMSO) to give (HBpz3)ReO3 (7) and the corresponding aldehyde. In the cases of 5 and 6 this transformation is quantitative. The addition of 2,6-lutidine to a low-temperature oxidation of 5 by DMSO redirects the reaction to form cis-2-butene instead of acetaldehyde. These oxidation reactions do not proceed through alkoxide intermediates, as shown by independent studies of alkoxide oxidations. Reaction of 5 with pyO or DMSO at −47 °C results in the formation of intermediates which are assigned as ylide or “trapped-carbene” complexes [(HBpz3)ReO(OH){CH(L)CH3}]OTf (L = py (8) or SMe2 (9), respectively). Mechanistic studies and analogies with related systems suggest that oxygen atom transfer to 4-6 forms [(HBpz3)ReO2R]+. Transfer of an α-hydrogen from the alkyl group to an oxo ligand then forms an alkylidene complex which is trapped by SMe2 or py to give the observed intermediates. Further oxidation of the ylide complex gives the aldehyde.

Rhenium(V) Oxo-Alkoxide Complexes: Syntheses and Oxidation to Aldehydes

New rhenium(V) oxo-alkoxide compounds (HBpz3)ReO(OR)Z (R = Me (l), Et (2), 'Pr (3), Bu (4), CHrPh (5)) have been prepared in good yields from reaction of (HBpz3)ReOClZ with excess alcohol in the presence of NEt3 [HBpz3 = hydrotris( 1-pyrazoly1)boratel. Treatment of these compounds with Me3SiOTf (OTf = OSO2CF3) forms the reactive triflate compounds (HBpz3)ReO(OR)(OTf) (6-8). The triflate complexes are rapidly oxidized by the oxygen atom donors pyridine N-oxide and MeZSO to give aldehydes or ketones, alcohols, and (HBpz3)Re03 (9). Addition of DMSO to 2 initially gives the sulfoxide adduct [(HBpz3)ReO(OEt)(OSMe2)10Tf (10). Mechanistic studies indicate that 10 rapidly and reversibly loses SMe2 (k'98 = 8.2 (6) s-I) to give a cationic rhenium(VI1) dioxo complex, [(HBpz3)ReOz(OEt)]OTf (11). in which oxidation of the ethoxide ligand occurs. An isotope effect of 4.6 is determined for C-H bond cleavage. Oxidation of the ethoxide ligand in 11 is proposed to occur by hydride transfer to an oxo group. The oxo ligands in 11 are shown to be electrophilic, based on the relative rates of Me2S and Me2SO oxidation, which explains their ability to act as hydride acceptors.

O-Phenylenediamine and related complexes of chromium, vanadium and manganese

Using the ligands (L–L)o-phenylenediamine, 4,5-dimethyl-o-phenylenediamine and phenanthrene-9,10-diamine, anionic chromium(III) complexes of the type [CrCl4(L–L)]–, have been isolated as quaternary phosphonium salts from interaction of CrCl3(thf)3(thf = tetrahydrofuran) and the ligand in the presence of [PPh4]Cl or [PPh3(CH2Ph)]Cl. Interaction in the absence of quaternary phosphonium salts gives [CrCl2(L–L)2]Cl. A similar tetrachloro anion has been obtained using the chelating phosphine 1,2-(HPriP)2C6H4. Similar complexes obtained from VCl3(thf)3 have the form [VCl4(L–L)]– and [VCl2(L–L)2]Cl. Use of the dihalides leads to octahedral complexes trans-MCl2(L–L)2(M = V or Cr) and trans-MnI2(L–L)2. The interaction of [P(CH2Ph)Ph3][CrCl4{(H2N)2C6H2Me2}] with AgO3SCF3 and of [CrCl2{(H2N)2C6H4}2]Cl with trifluoromethanesulfonic acid and diethyl ether leads to the unusual chromium(IV) octahedral triflate compounds Cr(NH2)(O3SCF3)3[(H2N)2C6H2Me2] and Cr(O3SCF3)4[(H2N)2C6H4], respectively. The crystal structures of the compounds [PPh3(CH2Ph)][CrCl4{(H2N)2C6H4}], Cr(NH2)(O3SCF3)3[(H2N)2C6H2Me2], Cr(O3SCF3)4[(H2N)2C6H4] and [PPh4][VCl4{(H2N)2C6H2Me2}] have been determined. All have octahedral structures with chelating diamines. In the tetrachlorochromate(III) salt, the Cr–N distances are ca. 0.05 A longer than those in the chromium(IV) compounds. The VIII–N distances [2.16(1)A] are ca. 0.05 A longer than the CrIII–N distances [2.11(1)A], as expected, but the vanadium complex shows a much greater diffrence in M–Cl distances trans to N [2.336(4)A] or trans to Cl [2.381(4)A] than in the chromium(III) complex [all 2.342–2.356(5)A].