Synthesis and crystal structure of some new cadmium (II) macrocyclic Schiff-base complexes containing piperazine moiety

The metal templated Cd(II) cyclocondensation of 2,6-diacetylpiridine or 2,6-pyridinedicarbaldehyde and two different amines containing piperazine moieties have been investigated. The resulting ligands, L¹ and L² are 16- and L³ and L⁴ 17-membered pentaaza macrocycles. The complexes have been characterized by a variety of methods including IR, ¹H, ¹³C NMR, DEPT, COSY(H,H), HMQC(H,C), FAB spectrometry and conductivimetry measurements. The crystal structures of [CdL²Cl](CH₃OH)ClO₄ (2) and [CdL⁴(NO₃)(H₂O)]ClO₄ (4) have been also determined, and it was shown that the geometry of the Cd(II) ion in the complexes is slightly distorted pentagonal pyramidal and pentagonal bipyramidal, respectively. The gas-phase structures of ligands, L² and L⁴ and their Cd(II) complexes have also theoretically studied.     

1H and 13C NMR study of 8-hydroxyquinoline and some of its 5-substituted analogues

¹H and ¹³C NMR spectra of 8-hydroxyquinoline (oxine) and its 5-Me, 5-F, 5-Cl, 5-Br and 5-NO₂ derivatives have been studied in DMSO-d₆ solution. The ¹H and ¹³C chemical shifts and proton–proton, proton–fluorine, carbon–proton and carbon–fluorine coupling constants have been determined. The ¹H and ¹³C chemical shifts have been correlated with the charge densities on the hydrogen and carbon atoms calculated by the CNDO/2 method. The correlation of the ¹H and ¹³C chemical shifts with the total charge densities on the carbon atoms is approximately linear (r_H² = 0.85, r_C² = 0.84). The proton in peri position to the nitro group in 5-NO₂-oxine is an exception.     

Aromatic protonation—4: On the 1H-2H exchange of three 9-n-alkylanthracenes on reaction with CF3CO2[2H] and FSO3[2H]

The reactions of 9-methyl-, 9-ethyl- and 9-propyl-anthracene with CF₃CO₂[²H] in C[²H]Cl₃ and with FSO₃[²H] in SO₂ClF have been investigated. Using 4 equivalents of CF₃CO₂[²H] at 50° ¹H-²H exchange was observed only for the 10-H and the side-chain α-hydrogens, and on using 8 and 12 equivalents at 50° also for the aromatic α-hydrogens. Treatment of the substrates with FSO₃[²H] at -60° leads to the stable 9-alkyl-[10-²H]-10-anthracenium ions. On warming up to ?25° a slow ¹H-²H exchange of only the 10-¹H of these anthracenium ions is observed. A mechanism for the ¹H-²H exchange of the aromatic and the side-chain α-hydrogens of the 9-alkylanthracenes is presented.     

Synthesis and properties of carboxy-substituted half-sandwich ruthenium complexes with chelating bisphosphine ligands (η-C5H4CO2H)Ru(η-L)X (X = I, H)

Several Ru(II) complexes (η⁵-C₅H₄CO₂H)Ru(η²-L)I have been prepared by the hydrolysis of the ester linkage in (η⁵-C₅H₄CO₂t-Bu)Ru(η²-L)Cl with trimethylsilyl iodide. The hydrides (η⁵-C₅H₄CO₂H)Ru(η²-L)H may be prepared by reduction of the iodide complexes in KOH/MeOH solutions followed by acidification. Complexes with several chelating bisphosphine ligands have been prepared in this way. The carboxylate anions [(η⁵-C₅H₄CO₂)Ru(η²-L)H]⁻ are readily protonated by weak acids to give the carboxyCp complexes. The pK_a of the carboxy proton of (η⁵-C₅H₄CO₂H)Ru(dppe)H (dppe = 1,2-bis(diphenylphosphino)ethane) is 11.3 in DMSO. Protonation of the neutral hydride complex (η⁵-C₅H₄CO₂H)Ru(dppf)H gives the cationic dihydride (η⁵-C₅H₄CO₂H)Ru(dppf)H⁺₂; the dihydride structure has been confirmed by measuring the T₁ of its ¹H NMR hydride resonance over a range of temperatures. The oxidations of the halide complexes (η⁵-C₅H₄CO₂H)Ru(dppf)I and (η⁵-C₅H₄CO₂t-Bu)Ru(dppf)Cl (dppf = 1,1′-bis(diphenylphosphino)ferrocene) have been studied by cyclic voltammetry.     

β-Diketonates of Cyclopalladated Arylazonaphthalenes: Synthesis, Characterization and Redox Activity

The synthesis of monomeric mixed species of the type [PdLK] (L = cyclopalladated arylazonaphthalenes) have been achieved by splitting the halogeno-bridge in [Pd₂L₂Cl₂] by β-diketones (HK). The compounds have been characterized on the basis of spectral (IR, UV–VIS, FAB mass, ¹H and ¹³C{¹H}NMR) and elemental analysis data. Some of the [PdLK] cyclometallates occur as isomeric mixtures whose composition have been established by ¹H-NMR data. Electron transfer properties of the cyclopalladates in DMF have been thoroughly examined using cyclic voltammetry.     

Nucleophilic Reactions of Osmanaphthalynes with PMe3 and H2O

Members of a new class of complexes, 2 (CF₃), 2 (H), 2 (Br), 2 (I), and 2 (OCH₃), have been synthesized in a one-pot method involving the treatment of osmanaphthalynes bearing corresponding substituents ( 1 (CF₃), 1 (H), 1 (Br), 1 (I), and 1 (OCH₃)) with trimethylphosphine (PMe₃) and water. The main reaction process involves two steps, namely a ligand-exchange with trimethylphosphine and nucleophilic addition of water to the Os≡C bond of the osmanaphthalyne. The substituents have a significant influence on the rate of the reaction, as befits a nucleophilic addition. Fortunately, the key intermediate [ 1 (OCH₃)]′ could be successfully captured, and the detailed reaction mechanism has been explored with the aid of density functional theory (DFT) calculations, which were in excellent agreement with the experimental findings. All of the target complexes have been fully characterized by ¹H, ³¹P{¹H}, and ¹³C{¹H} NMR spectroscopy, high-resolution mass spectrometry, and elemental analysis.     

Intramolecular rearrangement of the bridging σ,π-acetylide ligand in the Os3H(CO)9(L)(μ-η2-CCPh) (L = CO,PMe2Ph) clusters and crystal structure of Os3H(CO)9(PMe2Ph)(μ-η2-CCPh)

Clusters Os₃H(Cl)(CO)₉(L) (L= CO, PMe₂Ph) react with lithium phenyl-acetylide to yield Os₃H(CO)₉(L)(μ-η²-CCPh),which has a bridging acetylide ligand. The Os₃H(CO)₁₀(μ-η²-CCPh) complex (II) is fluxional owing to rapid π → σ, σ → π interchange of acetylide ligand between the bridged osmium atoms, whereas the phosphine-substituted derivative, Os₃H(CO)₉(PM₂Ph)(μ-η²-CCPh) (III), is stereochemically rigid and exists at room temperature in two isomeric forms. These isomers have been isolated as solids and have been characterized by ¹H and ³¹P{¹H} NMR spectroscopy. According to the spectroscopic data, in the major (IIIa) and minor (IIIb) isomers the phosphine ligand is coordinated to the metal atom which is σ- or π-bonded to the bridging acetylide group, respectively. The isomerization of IIIb into IIIa occurs only at 80°C. The structure of IIIa has been confirmed by an X-ray diffraction study.     

Verflüchtigung von Radionukliden im Luftstrom und Ihre Abscheidung im Temperaturgradientrohr

The Hg-, Cd- and UO₂-targets bombarded by protons have been treated using the sublimation and evaporation techniques. The Hg and Cd nuclei have been separated from non-isotopic products by distillation in the hydrogen stream. The separation of the groups of Re, Os, Ir, Mo, Tc and Ru oxides has been carried out in the air stream. No monotonic temperature dependence of the Tl, Ru, Mo, Tc, Te, Pb and Po release has been observed in the oxidation of the UO₂-ceramics in the air stream. The values of (−ΔH _a ⁰ ) of volatile products adsorbed on quartz have been determined from the chromatographic data. The relation between the adsorption heat (−ΔH _a ⁰ ) and the standard sublimation heat (ΔH ₂₉₈ ⁰ subl.) has been found to be linear, i.e. −ΔH _a ⁰ =(4.04±1.97)+(0.69±0.04)ΔH ₂₉₈ ⁰ (subl.). As an example of the thermochromatographic generator of isotopes, the separation of⁹⁹Mo to^99mTc has been investigated.      

Interaction of carboxyl functionalized catechols with palladium(II) and platinum(II) halide complexes

Summary A series of stable carboxyl substituted catecholato metal complexes of the type M(1,2-O₂C₆H₃R-4)(PPh₃)₂: M = Pd^II an Pt^II: R = CO₂H, CH₂CO₂H, C₂H₄CO₂H; have been prepared in high yield from reaction of the metal halide complex with catechols in the presence of a base. The compounds have been characterized on the basis of their elemental analyses. i.r. and n.m.r. spectra. The possibility of a metal carboxylato chelation had been considered and discussed on the light of the i.r. and n.m.r. spectra.     

Ion–molecule reaction in the gas phase 3—nucleophilic substitution of 17ξ-R-5α,14β-androstane-14,17ξ-diols under [NH4]+ chemical ionization conditions1

Under Ammonia chemical Ionization conditions the source decompositions of [M + NH₄]⁺ ions formed from epimeric tertiary steroid alchols 14 OH_β, 17OH_α or 17 OH_β substituted at position 17 have been studied. They give rise to formation of [M + NH₄? H₂O]⁺ dentoed as [MH_sH]⁺, [M_sH? H₂O]⁺, [M_sH? NH₃]⁺ and [M_sH? NH₃? H₂O]⁺ ions. Stereochemical effects are observed in the ratios [M_sH? H₂O]⁺/[M_sH? NH₃]⁺. These effects are significant among metastable ions. In particular, only the [M_sH]⁺ ions produced from trans-diol isomers lose a water molecule. The favoured loss of water can be accounted for by an S_N2 mechanism in which the insertion of NH₃ gives [M_sH]⁺ with Walden inversion occurring during the ion-molecule reaction between [M + NH₄]⁺ + NH₃. The S_N1 and S_Ni pathways have been rejected.     

Spin-orbit Splitting and Lifetime Broadening in the A2Δ Electronic State of l-C5H

Optical absorption bands at ～18772 and ～18807 cm^-1, previously assigned to A²Δ-X2Π electronic origin band transitions of the linear carbon-chain radicals C₅H and C₅D, respec-tively, have been reinvestigated. The spectra have been recorded in direct absorption apply-ing cavity ring-down spectroscopy to a supersonically expanding acetylene/helium plasma. The improved spectra allow deducing a l-C₅H upper state spin-orbit coupling constant A'=-0.7(3) cm^-1 and a A²Δ lifetime of 1.6±0.3 ps.     

1,2‐Bis[(pyridin‐2‐ylmethyl)sulfanyl]ethane and its dimorphic hydrochloride salt

Although having been described as a liquid in the literature for 41 years, 1,2‐bis[(pyridin‐2‐ylmethyl)sulfanyl]ethane, C₁₄H₁₆N₂S₂, (I), has now been obtained as monoclinic crystals via a new and convenient method of purification. Molecules of (I) are located on crystallographic inversion centres and are held together by C—H...N and C—H...S interactions, resulting in the formation of a three‐dimensional network structure. In addition, two polymorphs of the corresponding hydrochloride salt, 2‐[({2‐[(pyridin‐1‐ium‐2‐ylmethyl)sulfanyl]ethyl}sulfanyl)methyl]pyridin‐1‐ium dichloride, C₁₄H₁₈N₂S₂²⁺·2Cl⁻, (II) and (III), have been isolated. Molecules of (II) and (III) have similar conformations and are located on inversion centres. Both polymorphs form three‐dimensional networks through N—H...Cl, C—H...Cl and C—H...S interactions. The structure of (III) displays voids of 35 ų.     

Proton-coupled 13C NMR spectra of 2- and 3-substituted pyridines

The proton-coupled ¹³C NMR and PMR spectra of pyridine and the 2- and 3-monosubstituted pyridines NC₅H₄X [where X=CH₃, CN, COCH₃, COOCH₃, N(CH₃)₂, NO₂, OCH₃, Cl, or Br] for one-molar solutions of the compounds in DMSO-D₆, have been analyzed. The signs and values of the ¹³C-¹H HSSCs have been determined. Equations have been obtained connecting the ¹³C-¹H SSCCs in the 2- and 3-substituted pyridines and the monosubstituted benzenes. A satisfactory correlation of ¹JCH with the F and R constants of the substituents has been shown.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1223–1230, September, 1984.     

Synthesis,spectral and antimicrobial studies of diorganotin(IV)3(2′‐hydroxyphenyl)‐5‐(4‐substituted phenyl) pyrazolinates

Diorganotin(IV) dipyrazolinates of the type R₂Sn(C₁₅H₁₂N₂OX)₂ [where C₁₅H₁₂N₂OX = 3(2′‐Hydroxyphenyl)‐5(4‐X‐phenyl)pyrazoline {where X = H ( a ); CH₃ ( b ); OCH₃ ( c ); Cl ( d ) and R = Me, Prⁿ and Ph}] have been synthesized by the reaction of R₂SnCl₂ with sodium salt of pyrazolines in 1:2 molar ratio, in anhydrous benzene. These newly synthesized derivatives have been characterized by elemental analysis (C, H, N, Cl and Sn), molecular weight measurement as well as spectral [IR and multinuclear NMR (¹H, ¹³C and ¹¹⁹Sn)] studies. The bidentate behaviour of the pyrazoline ligands was confirmed by IR, ¹H and ¹³C NMR spectral data. A distorted trans‐octahedral structure around tin(IV) atom for R₂Sn(C₁₅H₁₂N₂OX)₂ has been suggested. The free pyrazoline and diorganotin(IV) dipyrazolinates have also been screened for their antibacterial and antifungal activities. Some diorganotin(IV) dipyrazolinates exhibit higher antibacterial and antifungal effect than free ligand and some of the antibiotics. Copyright © 2006 John Wiley & Sons, Ltd.     

Complexation of inorganic anions by β-cyclodextrin studied by polarography and 1H NMR

Abstract

Complexation of o-chloronitrobenzene with β-cyclodextrin has been studied in 0.1 M aqueous solutions containing PF₆ ^?, ClO₄ ^?, C₂O₄ ^2-, SCN^?, SO₄ ^2- and F^? anions by a polarographic method. Using an equation which takes account of the change in the cyclodextrin concentration due to the simultaneous complexation of the anion, both stability constants have been calculated. Interaction of the ClO₄ ^? anion with β-cyclodextrin has been confirmed by ¹H NMR techniques. It has been found that the ClO₄ ^? anion is trapped in the β-cyclodextrin cavity. The stability constant has been calculated. Results of polarographic and ¹H NMR studies have been compared.     

Synthesis,characterziation, semi-empirical quantum-mechanical study and biological activity of organotin(IV) complexes with 2-ethylanilinocarbonylpropenoic acid

Seven different organotin(IV) complexes have been synthesized by reacting 2-ethylanilinocarbonylpropenoic acid with R₂SnCl₂/R₃SnCl under reflux conditions. The organotin(IV) complexes along with ligand have been characterized by different techniques including elemental analysis, FT-IR and multinuclear NMR (¹H and ¹³C). IR data show that complexation occurs through -COO site and the ligand is bidentate which is also confirmed by the semi-empirical quantum-mechanical study. ¹H and ¹³C NMR data confirm the tetrahedral geometry of complexes in solution. The complexes as well as the ligand were also checked for various     

Zinc(II) complexes of Triaza and Amidinate ligands: Efficient initiators for the ring‐opening polymerization of ε‐Caprolactone and rac‐Lactide

Zinc complexes supported by tertiary 1,3,5‐triazapenta‐1,3‐dienate ligand (L¹) and N ‐benzoyl‐N′ ‐arylbenzamidinate [aryl =2,6‐diisopropylphenyl (L²), phenyl (L³)] ligands have been synthesized and characterized. The reaction of L¹H with ZnEt₂ affords a mononuclear zinc complex [L¹ZnEt] ( 1 ) in good yield. Tetra nuclear zinc complex [(L¹)₂Zn₄O(OAc)₄] ( 2 ) is prepared by treating L¹H with one equivalent of Zn(OAc)₂ in toluene. Further, dinuclear zinc complexes [L²ZnEt]₂ ( 3 ) and [L³ZnEt]₂ ( 4 ) are obtained in good yields from L²H and L³H with ZnEt₂ in toluene respectively_. The complexes 1–4 have been characterized by ¹H/¹³C NMR spectroscopy and single crystal X‐ray diffraction studies. All of the complexes have been explored for their catalytic activity toward the ring‐opening polymerization (ROP) of ε ‐caprolactone. It has been found that complex 1 is an active catalyst for the polymerization of ε ‐caprolactone in presence of a cocatalyst benzyl alcohol (BnOH). While complex 2 is as active as 1 there is no need for a cocatalyst for the polymerization to proceed. Dinuclear zinc complexes 3 and 4 show very high activity for the ROP of ε ‐caprolactone (CL) and rac ‐lactide (LA) without requiring a cocatalyst. The resultant polymers are found to have very high molecular weight (M _n = 296 X 10³ g mol⁻¹) and relatively narrow polydispersity index compared to 1 and 2 .     

Abstraction of hydrogen by methylene

The photolysis of CD₂CO at 313 nm in the presence of neopentane was carried out over the temperature range 576–706 K. Analysis of the products and isotopic analysis of the methanes demonstrate abstraction of H from neopentane and D from CD₂CO by methylene. The relative kinetics of abstraction of H and D have been measured over the temperature range, and the absolute value for the collision yield of the abstraction of H from neopentane by CD₂ at 653 K has been been estimated to be about 1.5 × 10¹¹ mole^?1 cm³ sec^?1, a value 10³ times larger than the corresponding reaction of CH₃.     

Synthesis,spectral and antimicrobial studies of chlorodiorganotin(IV)[3(2′-hydroxyphenyl)-5-(4-substitutedphenyl) pyrazolinates]

Chlorodiorganotin(IV)pyrazolinates of the type R₂SnCl(C₁₅H₁₂N₂O?·?X) [where C₁₅H₁₂N₂O?·?X?=?3(2′-Hydroxyphenyl)-5(4-X-phenyl)pyrazoline {where X?=?H (a); CH₃ (b); OCH₃ (c); Cl (d) and R?=?Me, Pr ⁿ and Ph}] have been synthesized by reaction of R₂SnCl₂ with the sodium salt of pyrazolines in 1?:?1 molar ratio, in anhydrous benzene. These newly synthesized derivatives have been characterized by elemental analysis (C, H, N, Cl and Sn), molecular weight measurement and spectral studies [IR and multinuclear NMR (¹H, ¹³C and ¹¹⁹Sn)]. The bidentate behavior of the ligands was confirmed by IR, ¹H and ¹³C NMR spectral data. Trigonal bipyramidal structure around tin(IV) for R₂SnCl(C₁₅H₁₂N₂O?·?X) is suggested. The free pyrazoline and some chlorodiorganotin(IV) pyrazolinates have been screened for their antibacterial and antifungal activities. Some chlorodiorganotin(IV) pyrazolinates exhibit higher antibacterial and antifungal effect than free pyrazoline and some antibiotics.     

Evidence for long-lived excited states of [CnH2]2+ carbodications

The energetics, structures, stabilities and reactivities of[C_nH₂]²⁺ ions have been investigated using computational methods and experimental mass spectrometric techniques. Spontaneous decompositions of [C_nH₂]²⁺ into [C_nH]⁺ + H⁺ products, observed for ions with odd-n values, have been explained by invoking the formation of excited triplet states. Even-n [C_nH]⁺ ions possess triplet ground states with low-lying excited states, whereas odd-n ions have triplet states with energies several eV above ground singlet states. Radiationless transitions of vibrationally excited long-lived triplet state ions into singlet state continua are suggested as possible mechanisms for spontaneous deprotonation processes of odd-n [C_nH₂]²⁺ ions. Evidence for these long-lived excited states has been obtained in bimolecular single electron transfer reactions.