Salts 2c Research Articles

Dynamics of Chiral Cations in Two-Dimensional CuX4 and PbX4 Perovskites (X = Cl and Br).

Chiral organic ammonium cations ((R)-2-methylphenethylammonium (R-MPhA) and (R)-3,7-dimethyloctylammonium (R-DMOA)) cations were combined with [MX4]2- anions (M = Cu and Pb, X = Cl and Br) to form two-dimensional (2D) perovskites: (R-MPhA)2CuCl4 (1a), (R-MPhA)2CuBr4 (1b), (R-DMOA)2CuCl4 (2a), (R-DMOA)2CuBr4 (2b), (R-DMOA)2PbCl4 (2c), and (R-DMOA)2PbBr4 (2d). The point shearing of the MX4 octahedron formed 2D perovskite layers, which were sandwiched by the bilayer molecular assembly of chiral organic ammonium cations. We found that the flexible and polar organic R-MPhA and R-DMOA cations in the 2D perovskites played an important role in the phase transition behavior and dielectric responses. Salts 2a-2d showed similar solid-solid (S1-S2) phase transitions, for which the temperatures decreased in the order of CuCl4 (2a) > PbCl4 (2c) > CuBr4 (2b) > PbBr4 (2d). The occupation volume of one R-DMOA per MX4 octahedron determined the dynamic crystalline space for the motional freedom of chiral ammonium in the 2D perovskite layer. Although thermally activated dielectric fluctuations were observed in salts 2a, 2b, and 2c, only an order-disorder-type dielectric phase transition was observed in salt 2d. Interband optical transitions were observed in the CuCl4 and CuBr4 2D perovskites, whereas sharp exciton absorptions were observed in the 2D PbCl4 and PbBr4 layers in perovskite salts 2c and 2d.

Triborate and pentaborate salts of non-metal cations derived from N-substituted piperazines: synthesis, structural (XRD) and thermal properties

The synthesis and characterization of a triborate salt, [H2N(CH2CH2)2NH2][B3O3(OH)4]2 (1), and four pentaborate salts, [H2N(CH2CH2)2NH][B5O6(OH)4] (2a), [MeHN(CH2CH2)2NH][B5O6(OH)4] (2b), [MeHN(CH2CH2)2NMe][B5O6(OH)4] (2c) and [Me2N(CH2CH2)2NMe2][B5O6(OH)4]2 (2d) are described. TGA and DSC analysis (in air, 25–1000 °C) indicate that triborate 1 decomposes to B2O3via a multistage process, with the first stage (<250 °C) being dehydration to condensed polymeric hexaborate of approximate composition: [H2N(CH2CH2)2NH2][B6O10]. The pentaborates (2a–2d) are thermally decomposed to B2O3via a 2 stage process involving polymeric [NMC][B5O8]. The anhydrous polyborates were amorphous. BET analysis of materials derived from the thermolysis of 1 at 250, 400, 600, and 1000 °C, were all non-porous (surface area <1.8 m2 g−1). A single-crystal X-ray diffraction study of 1 showed that it contains isolated triborate(1−) anions in a structure comprised of alternating cationic and anionic layers held together via extensive H-bonds. Single-crystal XRD structural studies on pentaborate salts 2c and 2d are also reported.

Bis(4-carbamoylpiperidinium) biphenyl-4,4′-disulfonate

In the title isonipecotamide salt 2C6H13N2O+·C12H8O6S2 2−, the asymmetric unit comprises one biphenyl-4,4′-disulfonate dianion which lies across a crystallographic inversion centre and another in a general position [dihedral angle between the two phenyl rings is 37.1 (1)°], together with three isonipecotamide cations. Two of these cations give a cyclic homomeric amide–amide dimer inter­action [graph set R 2 2(8)], the other giving a similar dimeric inter­action but across an inversion centre, both dimers then forming lateral cyclic R 4 2(8) pyrimidinium–amide N—H⋯O inter­actions. These units are linked both laterally and longitudinally to the sulfonate groups of the dianions through piperidinium N—H⋯O hydrogen bonds, giving a three-dimensional framework structure.

ChemInform Abstract: Studies on the Nucleophilic Addition to 3,5-Disubstituted Pyridinium Salts.

Abstract The reactivity of pyridinium salts 2 towards nucleophiles has been studied. The interaction with enolates derived from esters 1 gave only trace amounts of the expected compounds 3 . Irreversible-type additions, however, allowed the preparation of indolyldihydropyridines 8 and 9 with high yields. Reaction of organometallic 10 with salt 2c , followed by acidic cyclization, afforded tetracycle 12 .

CF3 Oxonium Salts, O-(Trifluoromethyl)dibenzofuranium Salts: In Situ Synthesis, Properties, and Application as a Real CF3+ Species Reagent

We report in situ synthesis of the first CF(3) oxonium salts, thermally unstable O-(trifluoromethyl)dibenzofuranium salts, which furthermore have different counteranions (BF(4)-, PF(6)-, SbF(6)-, and Sb(2)F(11)-) and ring substituents (tert-butyl, F, and OCH(3)), by photochemical decomposition of the corresponding 2-(trifluoromethoxy)biphenylyl-2'-diazonium salts at -90 to -100 degrees C. The yields markedly increased in the order of BF(4)- < PF(6)- < SbF(6)- < Sb(2)F(11)-. The CF(3) oxonium salts were fully assigned by means of (1)H and (19)F NMR spectroscopy at low temperature. The CF(3) salts decomposed to form CF(4) and dibenzofurans. The half-life times at -60 degrees C of the 2-tert-butyl salts having different counteranions were 29 min for BF(4)- salt 2d, 36 min for PF(6)- salt 2c, 270 min for SbF(6)- salt 2a, and 415 min for Sb(2)F(11)- salt 2b. Those at -60 degrees C of the Sb(2)F(11)- salts having different 2-substituents were 13 min for F salt 3b, 63 min for H (unsubstituted) salt 1b, and 415 min for tert-butyl salt 2b. Thus, the stability of the CF(3) oxonium salts increased in the order of BF(4)- < PF(6)- < SbF(6)- < Sb(2)F(11)- and F < H < tert-butyl, which is in accord with the increasing orders of the non-nucleophilicity of counteranions and the electron-donating effect of ring substituents. 2-tert-Butyl-O-(trifluoromethyl)dibenzofuranium hexafluoroantimonate (2a) was thus chosen and successfully applied as a real CF(3)+ species source to the direct O- and N-trifluoromethylations of alcohols, phenols, amines, anilines, and pyridines under very mild conditions. The thermal decomposition method with a mixture of diazonium salt 17a and aryl- or alkylsulfonic acids, pyridine, or pyridines having an electron-withdrawing group also afforded CF(3)O or CF(3)N products. The trifluoromethylation mechanism is discussed and an S(N)2 mechanism containing the transient formation of free CF(3)+ is proposed. Thus, the present study has demonstrated that the exceedingly reactive CF(3)+ species can be generated much easier than the CH(3)+ species, contrary to the common sense that CF(3)+ is extremely difficult to generate in solution.

Synthesis, structure, and interconversion of chiral rhenium oxygen- and sulfur-bound sulfoxide complexes of formula [(η5-C5H5)Re(NO)(PPh3)(OS(Me)R)]+ X−; diastereoselective oxidations of coordinated methyl alkyl sulfides †

Reactions of the chiral chlorobenzene complex [(η5-C5H5)Re(NO)(PPh3)(ClC6H5)]+BF4− (1+ BF4−) and alkyl methyl sulfoxides OS(Me)R (R = a, Me; b, Et; c, i-Pr or d, t-Bu), at −15 °C gave the oxygen-bound sulfoxide complexes [(η5-C5H5)Re(NO)(PPh3)(OS(Me)R)]+ BF4− (2a–2d+BF4−; 94–56%). Above 0 °C, 2a–2d+BF4− rearrange to sulfur-bound linkage isomers [(η5-C5H5)Re(NO)(PPh3)(S(O)(Me)R)]+BF4− (3a–3d+BF4−; 96–20%). The triflate salts 2c,2d+TfO− and 3b,3c+TfO− are analogously prepared from (η5-C5H5)Re(NO)(PPh3)(OTf). Complexes 2b–2d+X− and 3b–3d+X− can exist as two Re, S configurational diastereomers. Stereochemistry is assigned from reactions of (S)- or (R)-1+BF4− with enantiomerically enriched sulfoxides (R)-b–d, and a crystal structure of (SReRS,RReSS)-2d+TfO−·0.5CH2Cl2. Relative diastereomer stabilities, and the basis for the divergent kinetic and thermodynamic oxygen/sulfur binding selectivities, are analysed. The alkyl methyl sulfide complexes [(η5-C5H5)Re(NO)(PPh3)(S(Me)R)]+ X− and dimethyldioxirane react (acetone, −20 °C) to give 3a–3d+X−. Diastereoselectivities (3b–3d+X−) are fair to good. However, some overoxidation to Ph3PO occurs, lowering yields.

Studies on the nucleophilic addition to 3,5-disubstituted pyridinium salts

The reactivity of pyridinium salts 2 towards nucleophiles has been studied. The interaction with enolates derived from esters 1 gave only trace amounts of the expected compounds 3. Irreversible-type additions, however, allowed the preparation of indolyldihydropyridines 8 and 9 with high yields. Reaction of organometallic 10 with salt 2c, followed by acidic cyclization, afforded tetracycle 12.

Synthese, struktur und reaktivität zweikerniger hydridoverbrückter osmium-komplexe mit OsOs-Doppel- und Dreifach-Bindung

The dinuclear mesitylene osmium complexes [(Mes) 2Os 2(μ-H) 3]X ( 2a, b) and [(Mes)OsH(μ-H)] 2 ( 3) are prepared from [(Mes)OsCl 2] n ( 1) and NaBH 4. The complex 2a (X = Cl) and its corresponding BF 4 salt 2c can also be obtained from the reaction of 3 with HCl or HBF 4, respectively. The structures of 2a and 3 have been determined by single-crystal X-ray diffraction studies. The cation of 2a contains two equivalent (Mes)Os fragments linked by a rather short OsOs bond (247.41(2) pm) and three bridging hydride ligands. The midpoints of the six-membered rings together with the two osmium atoms form a linear unit. The metal—metal distance in compound 3 (267.34(6) pm) is significantly longer than that in the cation of 2a and corresponds to an OsOs double bond. The trans arrangement of the mesitylene rings with regard to the metal—metal bond axis indicates that two of the hydride ligands in 3 are terminal and two are bridging. An equilibrium between the cis and trans isomers of 3 probably exists in CD 2Cl 2 solution. Treatment of [(Mes)OsCl 2(PMe 3)] ( 4) with NaBH 4 or LiAlH 4 affords the dihydrido complex [(Mes)OsH 2(PMe 3)] ( 5) which is also one of the products of the reaction of 3 with PMe 3. Compound 5 is photoreactive and on UV irradiation in benzene gives the hydrido phenyl complex [(Mes)OsH(C 6H 5)PMe 3].

Stereoisomerism due to restricted rotation in N-substituted 2,6-di- ortho-tolylpyridirium cations. A molecular design enabling unambiguous identification of isomers

N-alkyl-2,6-di-di- o -tolylpyridinium salts 2a–d were prepared as mixtures of cis,trans-isomers, indicating restricted, rotation around the bonds joining the peripheral rings to the pyridinium ring. The 1HNMR spectra of the salts 2c or 2d display a singlet and an AB quartet for the methylenic protons in the CH 2R fragment, unambiguously assigned to the cis -(achiral) and trans -isomer (chiral), respectively. Tentative isomer assignments for salts 2a and 2b are based on shifts induced by lanthanide shift reagents. The 13CNMR chemical shifts for cis, trans-2a-d as well as the interconversion barriers Δ G # for 2a-c are presented.

Thio-claisen rearrangement approach to the synthesis of 2,3-disubstituted 4-piperidones

The thiopiperidone 1b , prepared from 1a (Lawesson's reagent, 85 %), underwent rapid reaction with allyl bromide to give the 5,6-dihydropyridinium salt 2c . By reaction of 2c with the appropriate Grignard reagents the C-2 functionalized intermediates 3c were obtained. Heating 3c (R = Pr) at 120°C in DME resulted in formation of the cyclized compounds 6 whereas in the presence of added propionic anhydride the thio-ester 7 was obtained. Under these latter conditions 3c (R = C 5H 11CH(OSiX)CC-) rearranged to give a mixture of 8 and 9 whereas in DME containing CH 3COOH-H 2O (trace) the desired 2,3-disubstituted 4-piperidones 11 and 12 were obtained in 95 % combined yield.

Dikationether, 6 [1] Spektroskopische Vergleiche von 9,9′-Oxy-bis(acridinium)- und 9,9′-Thio-bis(acridinium)-Salzen mit anderen 9-substituierten Acridinium-Ionen / Dication Ethers, 6 [1] Spectroscopic Comparisons of 9,9′-Oxy-bis(acridinium)- and 9,9′-Thio-bis(acridinium) Salts with Other 9-Substituted Acridinium Ions

9,9′-Oxy-bis(acridinium) salts 2a and 2b as well as the 9,9′-thio-bis(acridinium) salt 2c have been compared with other 9-substituted acridinium salts by 1H NMR, 13C NMR, and UV/VIS spectra. The data show that the bond state of the acridine rings in 2a-c is quite similar to that in 9-(pseudo)halide-substituted acridinium ions, i.e., the aromatic conjugation throughout the heterocyclic system is not disturbed