On precipitation effects of aluminum,lanthanum, iron (III), and thorium phosphates

Summary Typical precipitation curves of various metal phosphates have been obtained using the turbidimetric technique. The following systems have been investigated: Al(NO₃)₃-K₃PO₄, Al(NO₃)₃-KH₂PO₄, Al(NO₃)₃NaH₂PO₄, FeCl₃-K₃PO₄, FeCl₃-(NH₄)₂HPO₄, FeCl₃K₂HPO₄, FeCl₃-KH₂PO₄, FeCl₃-NaH₂PO₄, La(NO₃)₃K₃PO₄,La(NO₃)₃-K₂HPO₄,La(NO₃)₃-KH₂PO₄,La(NO₃)₃NaH₂PO₄ and Th(NO₃)₄-K₂HPO₄. Typical precipitation curves indicated concentration ranges of phosphate precipitation and of complex solubility.

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Zusammenfassung Typische F?llungskurven verschiedener Metallphosphate, die mittels Trübungsmessungen erhalten wurden, wurden graphisch dargestellt. Die folgenden Systeme wurden untersucht: Al(NO₃)₃-K₃PO₄,Al(NO₃)₃KH₂PO₄, Al(NO₃)₃-NaH₂PO₄, FeCl₃-K₃PO₄, FeCl₃(NH₄)₂HPO₄, FeCl₃-K₂HPO₄, FeCl₃-KH₂PO₄, FeCl₃NaH₂PO₄, La(NO₃)₃-K₃PO₄, La(NO₃)₃-K₂HPO₄, La(NO₃)₃-KH₂PO₄, La(NO₃)₃-NaH₂PO₄ und Th(NO₃)₄K₂HPO₄. Typische F?llungskurven zeigten Konzentrationsgebiete, in welchen die Metallphosphate gef?llt werden, sowie Konzentrationen, die zur Komplexbildung führten.

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Supported in part by the U.S. Army Research Office, Contract No. DA-ORD-10.     

Acetamidiniumhexafluorometallate von Aluminium,Gallium, Indium,Vanadium, Chrom,Mangan, Eisen und Cobalt

Acetamidiniumhexafluorometallates of Aluminium, Gallium, Indium, Vanadium, Chromium, Manganese, Iron and Cobalt The title compounds were crystallized from F-containing aqueous solutions of their hexafluoro-metallate acids by adding acetamidine. Their unit cells were determined and the thermal decomposition was investigated thermoanalytically. The crystal structure of [CH₃C(NH₂)₂]₃AlF₆ was determined: Space group P4₁2₁2/P4₃2₁2, a = 8,987(1), c = 17,894(3) Å, R = 0,054. The unit cell parameters: .     

Synthese und Kristallstrukturen von Bromid—Thiosilicaten Ln3Br[SiS4]2 der Lanthanide (Ln = La,Ce, Pr,Nd, Sm,Gd)

Synthesis and Crystal Structures of Lanthanide Bromide Thiosilicates Ln₃Br[SiS₄]₂ (Ln = La, Ce, Pr, Nd, Sm, Gd) Single crystals of the bromide—thiosilicates Ln₃Br[SiS₄]₂ were prepared by reaction of lanthanide metal (Ln = La, Ce, Pr, Nd, Sm, Gd), sulfur, silicon and bromine in quartz glass tubes. The thiosilicates crystallize in the monoclinic spacegroup C2/c (Z = 4) isotypically to the iodide analogues Ln₃I(SiS₄)₂ and the A—type chloride—oxosilicates Ln₃Cl[SiO₄]₂ with the following lattice constants: La₃Br[SiS₄]₂: a = 1583.3(4) pm, b = 783.0(1) pm, c = 1098.2(3) pm, β = 97.33(3)° Ce₃Br[SiS₄]₂: a = 1570.4(3) pm, b = 776.5(2) pm, c = 1092.2(2) pm, β = 97.28(2)° Pr₃Br[SiS₄]₂: a = 1562.6(3) pm, b = 770.1(2) pm, c = 1088.9(2) pm, β = 97.50(2)° Nd₃Br[SiS₄]₂: a = 1561.4(4) pm, b = 766.0(1) pm, c = 1085.3(2) pm, β = 97.66(3)° Sm₃Br[SiS₄]₂: a = 1555.4(3) pm, b = 758.5(2) pm, c = 1079.9(2) pm, β = 98.28(2)° Gd₃Br[SiS₄]₂: a = 1556.5(3) pm, b = 750.8(1) pm, c = 1074.5(2) pm, β = 99.26(2)° In the crystal structures the bromide ions form chains along [001] with trigonal planar coordination by lanthanide cations, while the [SiS₄]^4‐—building units display isolated distorted tetrahedra.     

Heterocyclic thiocarboxylato complexes of iron: synthesis,characterization, electrochemistry,and reactions

Heterocyclic-thiocarboxylato complexes of iron, CpFe(CO)₂SCO-het (het?=?2-C₄H₃O, 2-C₄H₃S, CH₂-2-C₄H₃S), have been synthesized via the reaction of iron sulfides, (μ-S _x )[CpFe(CO)₂]₂ (x?=?3,?4), with heterocyclic acid chlorides het-COCl. Photolytic substitutions of these complexes CpFe(CO)₂SCO-het with triphenylphosphine, triethylphosphite, triphenylarsine, and triphenylantimony [ER₃ (E?=?P, R?=?Ph, OC₂H₅; E?=?As, Sb, R?=?Ph)] exclusively gave the monosubstituted complexes CpFe(CO)(ER₃)SCO-het in good yields. The new complexes have been characterized by elemental analysis, UV-Vis, IR, ¹H, and ³¹P NMR spectroscopies and by cyclic voltammetry for a representative family (1, 4a–d). The solid state structures of CpFe(CO)₂SCO(2-C₄H₃S) (2), CpFe(CO)(PPh₃)SCO(2-C₄H₃S) (5a), CpFe(CO)(AsPh₃)SCO(2-C₄H₃S) (5b), and CpFe(CO)(SbPh₃)SCO(2-C₄H₃S) (5c) were determined by X-ray crystal structure analysis.     

Neue Synthesen und Kristallstrukturen von Bis(fluorphenyl)quecksilber,Hg(Rf)2 (Rf = C6F5, 2, 3, 4, 6‐F4C6H, 2, 3, 5, 6‐F4C6H, 2, 4, 6‐F3C6H2, 2, 6‐F2C6H3)

New Syntheses and Crystal Structures of Bis(fluorophenyl) Mercury, Hg(R_f)₂ (R_f = C₆F₅, 2, 3, 4, 6‐F₄C₆H, 2, 3, 5, 6‐F₄C₆H, 2, 4, 6‐F₃C₆H₂, 2, 6‐F₂C₆H₃) Bis(fluorophenyl) mercury compounds, Hg(R_f)₂ (R_f = C₆F₅, C₆HF₄, C₆H₂F₃, C₆H₃F₂), are prepared in good yields by the reactions of HgF₂ with Me₃SiR_f. The crystal structures of Hg(2, 3, 4, 6‐F₄C₆H)₂ (monoclinic, P2₁/n), Hg(2, 3, 5, 6‐F₄C₆H)₂ (monoclinic, C2/m), Hg(2, 4, 6‐F₃C₆H₂)₂ (monoclinic, P2₁/c) and Hg(2, 6‐F₂C₆H₃)₂ (triclinic, P1) are described.     

Aminomethyl Transfer (Mannich) Reactions Between an O-Triethylsilylated Hemiaminal and Anilines,RnC6H5−nNH2 Leading to New Diamines,Triamines, Imines,or 1,3,5-Triazines Dependent upon Substituent R

The reactions of the Mannich reagent Et₃SiOCH₂NMe₂ ( 1 ) with a variety of anilines (mono-substituted RC₆H₄NH₂, R=H, 4-CN, 4-NO₂, 4-Ph, 4-Me, 4-MeO, 4-Me₂N; di-substituted R₂C₆H₃NH₂, R₂=3,5-(CH₃)₂, 3,5-(CF₃)₂; tri-substituted R₃C₆H₂NH₂, R₃=3,5-Me₂-4-Br and a “super bulky” aniline (Ar*NH₂) [Ar*=2,6-bis(diphenylmethyl)-4-tert-butylphenyl]) led to the formation of a range of products dependent upon the substituent. With electron-withdrawing substituents, previously unknown diamines, RC₆H₄NH(CH₂NMe₂) [R=CN ( 2 a ), NO₂ ( 2 b )] and R₂C₆H₃NH(CH₂NMe₂) [R₂=3,5-(CF₃)₂ ( 2 c) ] were formed. Further reaction of 2 a , b , c with 1 yielded the corresponding triamines RC₆H₄N(CH₂NMe₂)₂ (R=CN ( 3 a ), NO₂ ( 3 b ) and R₂C₆H₃N(CH₂NMe₂)₂, R₂=3,5-(CF₃)₂ ( 3 c ). The new polyamines were characterized by NMR spectroscopy, and for 2 a , 2 c _, and 3 c , by single crystal XRD. In the case of electron-donating groups, R=4-OMe, 4-NMe₂, 4-Me, 3,5-Me₂, 3,5-Me₂-4-Br, and for R=4-Ph, the reactions with 1 immediately led to the formation of the related 1,3,5-triazines, R=4-MeO ( 5 a ), 4-Me₂N ( 5 b ), 4-Me ( 5 c ), 3,5-Me₂ ( 5 d ), 3,5-Me₂-4-Br ( 5 e ), 4-Ph ( 5 f ), 4-Cl ( 5 g ). The “super bulky” aniline rapidly produced a single product, namely the corresponding imine Ar*N=CH₂ ( 4 ) which was also characterized by single crystal XRD. Imine 4 is both thermally and oxidatively stable. All reactions are very fast, thus based upon the presence of Si we are tempted to denote the reactions of 1 as examples of “Silick” chemistry.     

Electrospray Mass Spectrometry Study on Polynuclear Pd(II) and Ni (II) Complexes of 3, 6, 9, 16, 19, 22‐Hexaazatricyclo [22. 2.2.211,14] triaconta‐11, 13, 24, 26 (1), 27, 29‐Hexaene

Polynuclear Pd(II) and Ni(II) complexes of macrocyclic polyamine 3,6,9,16,19,22‐hexaazatricyclo[22.2.2.2^11,14]‐triaconta 11,13,24,26(l),27,29‐hexaene (L) in solution were investigated by electrospray ionization mass spectrometry (ESIMS). For methanol solution of complexes M₂LX₄ (M = Pd(II) and Ni(II), X= Cl and I), two main clusters of peaks were observed which can be assigned to [M₂LX₃]⁺ and [M₂LX₂]²⁺. When Pd₂LCl₄ was treated with 2 or 4 mol of AgNO₃, it gave rise formation of Pd₂LCl₂ (NO₃)₂ · H₂O and [Pd₂L(H₂O)_m(NO₃)_n]^(4‐n)+, respectively. ESMS spectra show that the dissociation of the former in the ionization process gave peaks of [Pd₂LCl₂]²⁺ and [(Pd₂LCl₂)NO₃]⁺, while dissociation of the later gave the peaks of [Pd₂L(CH₃CO₂)₂]²⁺ and [Pd₂L(CH₃CO₂)₂](NO₃) ⁺ in the presence of acetic acid. Similar species were observed for Pd₂LI₄ when treated with 4 mol of AgNO₃. When [Pd₂L · (H₂O)_m(NO₃)_n]^(4‐n)+ reacted with 2 mol of oxalate anions at 40°C, [Pd₄L₂(C₂O₄)₂(NO₃)₂]²⁺ and [Pd₄L₂(C₂O₄)₂ (NO₃)]³⁺ were detected. This implies the formation of square‐planar molecular box Pd₄L₂(C₂O₄)₂(NO₃)₄ in which C₂O₄^? may act as bridging ligands as confirmed by crystal structure analysis. The dissociation form and the stability of complex cations in gaseous state are also discussed. This work provides an excellent example of the usefulness of ESIMS in the identification of metal complexes in solution.     

A New Type of Divalent Europium Compound MEuPO4 (M = K,Rb, Cs), its Synthesis,Crystal Structure,and Properties

Phosphates MEuPO₄ with M = K, Rb, and Cs were synthesized by the reduction of EuPO₄ with alkali metal vapour under 1 Pa of argon pressure at 260–530°C in sealed tantalum or niobium lined glass tubes. All the compounds belong to the β-K₂SO₄ orthorhombic structure with a = 7.359(3), b = 9.630(4), c = 5.569(2) Å, V = 394.7(2) ų for KEuPO₄, a = 7.462(3), b = 9.797(3), c = 5.649(2) Å, V = 413.0(2) ų for RbEuPO₄ and a = 7.889(2), b = 10.099(2), c = 5.820(4) Å, V = 463.6(2) ų for CsEuPO₄. Samples are stable and not hygroscopic in air at room temperature but hydrolyse to Eu₅(PO₄)₃OH, hexagonal, a = 9.764(2), c = 7.262(2) Å, on heating in water and decompose to Eu₃(PO₄)₂, hexagonal, a = 5.393(1), c = 19.838(3) Å, under argon at ca. 600°C. All the five compounds are paramagnetic.     

Phosphaniminato-Komplexe des Zinks mit Hydrido-, Alkinylo-, Alkenylo- und Amido-Liganden

Phosphoraneiminato Complexes of Zinc with Hydrido, Alkynylo, Alkenylo, and Amido Ligands Synthesis and properties of the phosphoraneiminato complexes [ZnCl(NPMe₃)]₄ ( 1 ), [ZnH(NPMe₃)]₄ ( 2 ) as well as of the alkynylo derivatives [Zn(C≡C–SiMe₃)(NPMe₃)]₄ ( 3 ), [Zn(C≡C–C≡C–SiMe₃)(NPR₃)]₄ [R = Me ( 4 a ), R = Et ( 4 b )], [Zn(C≡C–Ph)(NPMe₃)]₄ ( 5 ) and of the alkenylozinc complexes [Zn(CH=CHMe)(NPR₃)]₄ [R = Me ( 6 a ), R = Et ( 6 b )] are described. According to crystal structure analyses of 1 , 3 , and 4 b these complexes possess heterocubane structures with only slightly distorted Zn₄N₄ cubic skeletons. Experiments to substitute the terminal ligands at the zinc atoms by bis(trimethylsilyl)amido groups lead to disintegration of the heterocubanes and formation of the dimeric complex [Zn(μ₂-NPEt₃){N(SiMe₃)₂}]₂ ( 7 ) and of the trinuclear derivative [Zn₃(μ₂-NPMe₃)₄{N(SiMe₃)₂}₂] ( 8 ), in which the central zinc atom is surrounded by the four N atoms of the NPEt₃^– groups in a spiro-cyclic fashion. 7 and 8 are also characterized by crystal structure analyses.     

Organometallic Molybdenum(V) Complexes with Primary Phosphine Ligands. Syntheses,Spectroscopic Properties and Molecular Structures of [Cp°MoCl4(PH2R)] (R = But, 1‐Ad,Cy, Ph, 2, 4, 6‐Me3C6H2, 2, 4, 6‐Pri3C6H2, Cp° = C5EtMe4)

[Cp°MoCl₄] (Cp° = C₅EtMe₄) reacts with primary phosphines PH₂R to give the paramagnetic phosphine complexes [Cp°MoCl₄(PH₂R)] [Cp° = C₅EtMe₄, R = Bu^t ( 1 ), 1‐Ad (1‐Ad = 1‐adamantyl; 2 ), Cy ( 3 ), Ph ( 4 ), Mes (Mes = 2, 4, 6‐Me₃C₆H₂; 5 ), Tipp (Tipp = 2, 4, 6‐Prⁱ₃C₆H₂; 6 )]. 1 — 6 were characterized spectroscopically (IR, MS), and X‐ray crystal structures were determined for 1 — 4 and 6 . EPR investigations in liquid and frozen solution confirmed the presence of Mo^V species, and the data were used to analyze the spin‐density distribution in the first coordination sphere. Complexes 3 and 4 react with two equivalents of NEt₃ with formation of [Cp°MoCl₂(η³‐P₄Cy₄H)] ( 7 ) and [Cp°₂Mo₂(μ‐Cl)₂(μ‐P₄Ph₄)] ( 8 ), respectively, in low yield. Complexes 7 and 8 were characterized by X‐ray crystallography.     

Electronic structure,geometry, and stability of organic cations,dications, and donor-acceptor complexes

Geometric, electronic, and energy characteristics of the complexes formed in the CF₄ ·nAIF₃ (n = I or 2) and CBr₄ ·nAIBr₃ (n = 1, 2, or 4) systems have been determined by the semiempirical AM I method. Besides the donor-acceptor complexes, the CBr₃ ⁺...AIBr₄ ^–, CBr₃ ⁺...Al₂Br₇ ^–, CBr2²⁺...(AlBr₄ ^–)₂, and CBr₂ ²⁺...(Al₂Br₇ ^–)₂ ionic complexes can be formed in the CBr₄ ·nAlBr₃ systems. In the cations and dications of polyhalomethanes (when Hal = Cl, Br, or l) in both the free and bound (included in ionic complexes) states, carbon atoms carry negative charges, the C-Hal bonds are substantially shortened, and the positive charges are located on one-coordinate halogen atoms. These cations and dications can be considered as halenium ions that differ from halenium salts with dicoordinate halogen atoms. In the cationic and dicationic complexes of the CBr₄ ·nAlBr₃ systems, the maximum positive charges on the Br atoms are 0.39 and 0.94, respectively. Fluorine-containing cations and dications have structures similar to those of carbenium ions, whereas in the CF₄ ·nAIF₃ systems (n = l or 2), only donor-acceptor complexes are formed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya. No. 3, pp. 554–560, March, 1996.     

Preparation,Crystal Structures,and Thermal Studies of Alkaline Earth Nitrocarboxylates

The preparation, crystal structures, and thermal properties of [Ca(pyr)₂(4‐nba)₂]_n ( 1 ) (pyr = pyrazole; 4‐nba = 4‐nitrobenzoate) {[Ca(H₂O)₂(3‐npth)] · H₂O}_n ( 2 ) (3‐npth = 3‐nitrophthalate), [Mg(H₂O)₅(3‐npth)] · 2H₂O ( 3 ), and [Mg(H₂O)₄(2‐nba)₂] ( 4 ) (2‐nba = 2‐nitrobenzoate) are reported. The anhydrous Ca^II compound 1 and the diaqua Ca^II‐3‐nitrophthalate monohydrate 2 are one‐dimensional coordination polymers containing a hexacoordinate Ca^II ion located on a center of inversion in 1 and a heptacoordinated Ca^II ion in 2 . In 1 , the 4‐nitrobenzoate moiety acts as a μ₂‐bridging bidentate ligand, whereas the 3‐nitrophthalate anion exhibits a μ₃‐bridging pentadentate coordination mode in 2 . The hexacoordinate Mg^II‐containing compounds 3 and 4 do not contain a [Mg(H₂O)₆]²⁺ unit and the central Mg^II ion is coordinated to at least one monodentate carboxylate unit namely the monodentate 3‐npth molecule in 3 and two trans monodentate 2‐nba molecules in 4 . Hydrogen bonding between the lattice water molecules results in the formation of a water dimer in 3 . A comparative study of 17 alkaline earth nitrocarboxylates is described.     

Design and synthesis of novel quinoline derivatives bearing oxadiazole,isoxazoline, triazolothiadiazole,triazolothiadiazine, and piperazine moieties

A new series of 2,3-disubstituted quinoline derivatives were synthesized from 2-chloroquinoline-3-carbaldehyde. In the reaction sequence, acetanilide was cyclized to give 2-chloroquinoline-3-carbaldehyde 1 , which was transformed to 2-(4-phenylpiperazin-1-yl)quinolin-3-carbaldehyde 2 by reaction with 4-phenylpiperazine in DMF-containing anhydrous K₂CO₃; then, compound 2 was oxidized by iodine in methanol, and methyl 2-(4-phenylpiperazin-1-yl)quinoline-3-carboxylate 3 was synthesized. The key intermediate 4 , 4-amino-5-[2-(4-phenylpiperazin-1-yl)quinolin-3-yl]-4H-1,2,4-triazole-3-thiol, was prepared using the ester 3 by a series of step. Reaction of 5 with various aromatic carboxylic acids or phenacyl bromides yielded 1,2,4-triazolo[3,4-b][1,3,4]thiadiazoles 5a-c and 1,2,4-triazolo[3,4-b][1,3,4]thiadiazines 6a-c , respectively. Moreover, compound 2 condensed with o-phenylenediamine to give 2-[2-(4-phenylpiperazin-1-yl)quinolin-3-yl]-1H-benzimidazole 7 . Interaction of 7 and 2-chloromethyl-5-aryl-1,3,4-oxadiazoles in the presence of K₂CO₃ led to the title compounds 8a-c . Furthermore, 4,5-dihydroisoxazoline derivatives 9a-c were obtained by the reaction of readily accessible starting materials including 2-(4-phenylpiperazin-1-yl)quinolin-3-carbaldehyde 2 , 1-phenyl-2-(triphenylphosphoranylidene)ethanone and hydroximoyl chlorides under mild conditions in the presence of Et₃N. The hydrazone intermediates 10a-c were obtained by the condensation of 2 with aroylhydrazides in ethanol, then, refluxing in acetic anhydride yielded 3-acetyl-5-aryl-2-[2-(4-phenylpiperazin-1-yl)quinolin-3-yl]-2,3-dihydro-1,3,4-oxadiazoles 11a-c . Structures of these compounds were established by their elemental analysis, IR, ¹H NMR, and mass spectral data.     

Spinel, YbFe2O4, and Yb2Fe3O7 types of structures for compounds in the In2O3 and Sc2O3---A2O3---BO systems [A: Fe, Ga, or Al; B: Mg, Mn, Fe, Ni, Cu, or Zn] at temperatures over 1000°C

In the Sc₂O₃---Ga₂O₃---CuO, Sc₂O₃---Ga₂O₃---ZnO, and Sc₂O₃---Al₂O₃---CuO systems, ScGaCuO₄, ScGaZnO₄, and ScAlCuO₄ with the YbFe₂O₄-type structure and Sc₂Ga₂CuO₇ with the Yb₂Fe₃O₇-type structure were obtained. In the In₂O₃---A₂O₃---BO systems (A: Fe, Ga, or Al; B: Mg, Mn, Fe, Ni, or Zn), InGaFeO₄, InGaNiO₄, and InFe³⁺MgO₄ with the spinel structure, InGaZnO₄, InGaMgO₄, and InAlCuO₄ with the YbFe₂O₄-type structure, and In₂Ga₂MnO₇ and In₂Ga₂ZnO₇ with the Yb₂Fe₃O₇-type structure were obtained. InGaMnO₄ and InFe₂O₄ had both the YbFe₂O₄-type and spinel-type structures. The revised classification for the crystal structures of AB₂O₄ compounds is presented, based upon the coordination numbers of constituent A and B cations.     

Synthesis,spectroscopic, thermal,crystal structure properties,and characterization of new Hofmann-Td-type complexes with 3-aminopyridine

In this study, synthesis of two new tetracyanocadmate(II) and tetracyanozincate(II) complexes based on 3-aminopyridine (3AP) and investigation of their structural properties were reported. These complexes were characterized by using vibration spectroscopy, elemental, thermal analysis and single crystal X-ray diffraction (SC-XRD) techniques. Investigation of the elemental, spectral and single crystal data of these complexes showed that the formulas [Cd(3AP)₂Zn(μ₄-CN)₄]_n (1) and [Cd(3AP)₂Cd(μ₄-CN)₄]_n (2) fully explained their crystal structure. General information about the structural and chemical properties of these complexes obtained in single crystal form was obtained by observing the changes in the characteristic peaks of the 3AP with the [Zn(μ₄-CN)₄]^2- and [Cd(μ₄-CN)₄]^2- structures that make up these complexes. The behaviors of these complexes against changes in temperature were obtained by examining the temperature-dependent changes of their mass. The asymmetric unit of the heterometallic complexes 1 and 2 consist of half Cd(II) ion, half M ion [M = Zn1 in 1 and Cd2 in 2], two cyanide ligands and one 3AP.     

Rates of base-catalysed cleavage of pyridyl-, quinolyl-, picolyl- and (quinolylmethyl)-trimethylsilanes

Rates of cleavage of some picoyl- and (quinolylmethyl)-trimethylsilanes (RSiMe₃, where R = PyCH₂ or QnCH₂SiMe₃) have been measured in “90%” aqueous methanolic sodium methoxide at 50°C. Relative reactivities are: 2-PyCH₂, 1.0; 3-PyCH₂, 0.030; 4-PyCH₂, 8.9; 2-QnCH₂, 41; 3-QnCH₂, 0.161; 4-QnCH₂, 37. The rates correlate well with those for base-catalysed hydrogen-exchange in the parent carbon acids RH. Approximate pK_a's (based on the scale of ion-pair acidities in CsNHC₆H₁₁H₂NC₆H₁₁, with pK_a of 9-phenylfluorene = 18.6) for the carbon acids, RH, can be derived as follows: 2-PyCH₃, 29.5; 3-PyCH₃, 34; 4-PyCH₃, 27; 2-QnCH₃, 25; 3-QnCH₃, 32; 4-QnCH₃, 25.Rates of cleavage of pyridyl- and quinolyl-trimethylsilanes (PySiMe₃ and QnSiMe₃) by sodium hydroxide in 4 : 1 v/v Me₂SO/H₂O at 50°C have also been measured; and the relative reactivities are: 2-Py, 1.0; 3-Py, 2.9; 4-Py, 8.4; 2-Qn, 15.9; 3-Qn, 12.7; 4-Qn, 184. The sequence of reactivity differes from that for base-catalysed hydrogen-exchange at the relevant positions of pyridine and quinoline, indicating that the reactivities are not determined in both cases (if in either) solely by the stabilities of the corresponding carbanions.     

Synthesis,crystal structures,thermal properties,and DNA-binding studies of transition metal complexes with imidazole ligands

A new series of complexes of transition metal (Cu, Zn, Ni) perchlorate with imidazole have been synthesized and characterized by elemental analysis, infrared (IR), UV-Vis spectroscopy, and single-crystal X-ray diffraction. Based on elemental and spectral data, the complexes are M(C₃H₄N₂) _x (ClO₄)₂ (M?=?Cu, Zn, x?=?4; M?=?Ni, x?=?6; C₃H₄N₂?=?imidazole). The crystal structures of Cu(C₃H₄N₂)₄(ClO₄)₂ (1) and Zn(C₃H₄N₂)₄(ClO₄)₂ (2) show metals surrounded by four nitrogens of imidazole, while the nickel complex Ni(C₃H₄N₂)₆(ClO₄)₂ (3) has six nitrogens of imidazole. Intra- and inter-molecular hydrogen bonds exist between hydrogen of imidazole and oxygen of perchlorate. The thermal stabilities of 1, 2, and 3 at different heating rates (β?=?5°C?min^?1, 10°C?min^?1, and 15°C?min^?1) show that all the complexes exhibit two thermal decomposition stages; the sequence of thermal stability is 2?>?1?>?3. 1, 2, 3, and imidazole display DNA binding ability, ascertained by UV-Vis titration.     

Hexanuclear Co4Dy2, Zn4Dy2, and Co4Y2 Complexes with Defect Tetracubane Cores: Syntheses,Structures, and Magnetic Properties

A hexanuclear heterometallic cluster of composition [Dy₂Co₄(L)₄(NO₃)₂(OH)₄(C₂H₅OH)₂] ⋅ 2 C₂H₅OH ( 1 ) was synthesized by employing a Schiff base 2-(((2-hydroxy-3-methoxybenzyl) imino)methyl)-4-methoxyphenol (H₂L) as ligand and utilizing Dy(NO₃)₃ ⋅ 6H₂O and Co(NO₃)₂ ⋅ 6H₂O as metal ion sources. X-ray single-crystal diffraction analysis indicated that complex 1 contains a defect tetracubane core and possesses central symmetric structure, with two Dy^III ions being in the central body position of the molecule and four Co^II ions being arranged at the outer sites. Magnetic studies reveal that complex 1 behaves as single-molecule magnet (SMM) with energy barrier of 27.50 K. To investigate the individual contribution of Dy^III and Co^II ions to the SMM behavior, another two complexes of formulae [Dy₂Zn₄(L)₄(NO₃)₂(OH)₄] ⋅ 4CH₃OH ( 2 ) and [Y₂Co₄(L)₄(NO₃)₂(OH)₄(C₂H₅OH)₂] ⋅ 2 C₂H₅OH ( 3 ) were prepared. Complexes 1 and 3 are isomorphous. The coordination geometries of Dy^III ions in 1 and 2 are different. The Dy^III ions are eight-coordinated in 2 and nine-coordinated in 1 . Complex 2 exhibits SMM behavior with energy barrier of 69.67 K, but complex 3 does not display SMM property. These results reveal that the SMM behaviors of 1 and 2 are mainly originated from Dy^III ions. It might be the higher symmetry of Dy^III ions in 2 that results in the higher energy barrier.