Metallomicellar catalysis: effects of bridge-connecting ligands on the hydrolysis of PNPP catalyzed by Cu(II) complexes of ethoxyl-diamine ligands in micellar solution

The syntheses of three ligands are reported: N,N,N′,N′-tetra(2-hydroxyethyl)-1,3-propylene-diamine (1), N,N,N′,N′-tetra(2-hydroxyethyl)-1,10-decadiamine (2), N,N,N′,N′-tetra(2-hydroxyethyl)-1,4-xylyldiamine (3). The catalytic hydrolysis of p-nitrophenyl picolinate (PNPP) by the bivalent metal ion Cu(II) complexes of these ligands was studied kinetically in a buffered CTAB or Brij35 micellar solutions at 25 °C and different pH values. The results indicate that 1:2 and 2:1 complexes of these ligands and metal ion are the active species for the catalytic hydrolysis of PNPP in CATB and Brij35 micellar solutions. The ternary complex kinetic model for metallomicellar catalysis was employed to obtain the relative kinetic and thermodynamic parameters. The effects of the structure of the ligands and the microenvironment of reaction on the hydrolytic reaction of PNPP have been discussed in detail.     

Cyano-bridged bimetallic complexes of copper(II) with tetracyanonickelate(II). Crystal structure of [Cu(dpt)Ni(CN)4]

Five new complexes of composition [Cu(dpt)Ni(CN)₄] (1) (dpt=dipropylenetriamine), [Cu(dien)Ni(CN)₄]·2H₂O (2) (dien=diethylenetriamine), [Cu(N,N′-dimeen)Ni(CN)₄]·H₂O (3) (N,N′-dimeen=N,N′-dimethylethylenediamine), [Cu(N,N-dimeen)Ni(CN)₄]·H₂O (4) (N,N-dimeen=N,N-dimethylethylenediamine) and [Cu(trimeen)Ni(CN)₄] (5) (trimeen=N,N,N′-trimethylethylenediamine) have been obtained by the reactions of the mixture of Cu(ClO₄)₂·6H₂O, appropriate amine and K₂[Ni(CN)₄] in water and have been characterized by IR and UV–Vis spectroscopies and magnetic measurements. The crystal structure of [Cu(dpt)Ni(CN)₄] (1) has been determined by single-crystal X-ray analysis. The structure of 1 consists of a one-dimensional polymeric chain ---Cu(dpt)---NC---Ni(CN)₂---CN---Cu(dpt)--- in which the Cu(II) and Ni(II) atoms are linked by CN groups. The nickel atom is four coordinate with four cyanide-carbon atoms (two cyano groups are terminal and two cyano groups (in cis fashion) are bridged) in a square-planar arrangement and the copper atom is five coordinate with two cyanide-nitrogen and three dpt-nitrogen atoms, in a distorted square-pyramidal arrangement. The temperature dependence of magnetic susceptibility (2–300 K) was measured for compound 1. The magnetic investigation showed the presence of a very weak antiferromagnetic interaction (J=−0.16 cm⁻¹) between the copper atoms within each chain through the diamagnetic Ni(CN)₄ ²⁻ ions.     

Synthesis and spectroscopic analysis of tetraphenylporphyrinatoantimony(V) complexes linked to boron-dipyrrin chromophore on axial ligands

Tetraphenylporphyrinatoantimony(V) complexes, linked to boron-dipyrrin chromophores on axial ligands, were synthesized. The fluorescence spectra of 1a, 1b and 1c (3-[4-(N,N′-difluorobornyl-5-dipyrrinyl)phenyl]propoxo(methoxo)antimony(V) tetraphenylporphyrin bromide (1a); 6-[4-(N,N′-difluorobornyl-5-dipyrrinyl)phenyl]hexyloxo(methoxo)antimony(V) tetraphenylporphyrin bromide (1b); bis{3-[4-(N,N′-difluorobornyl-5-dipyrrinyl)phenyl]propoxo}antimony(V) tetraphenylporphyrin bromide (1c)) were analyzed under the excitations of N,N′-difluorobornyl-5-dipyrrinylphenyl (Bdpy) and tetraphenylporphyrinatoantimony(V) (Sb(TPP)) chromophores. Under the irradiation of Bdpy chromophore, the excitation energy was transferred from Bdpy chromophore to the Sb(TPP) moiety at 0.13–0.40 of the quantum yields, even in a polar solvent. On the other hand, the emission of Sb(TPP) chromophores was quenched by Bdpy chromophores at rate constants of 10⁸–10⁹ s⁻¹, independent of on the solvent polarity. Under the excitation of the Bdpy chromophore of 1d (3-[4-(N,N′-difluorobornyl-5-dipyrrinyl)phenyl]propoxo(phenyloxo)antimony(V) tetraphenylporphyrin bromide) involving both the Bdpy and the phenoxy chromophores on the axial ligands, the excited singlet state of the Sb(TPP) chromophore generated by the energy transfer from the Bdpy chromophore was quenched by the phenoxy ligand via non-radiative processes involving electron transfer. However, rapid back electron-transfer may occur because no absorption of the anion radical of Sb(TPP) was observed by nanosecond laser photolysis.     

A ring-fission/C–C bond cleavage reaction with an N-alkyl-N-methyl-N-[(5-phenyl-1,2,4-oxadiazol-3-yl)methyl]amine

The reaction of N-(3,4-dichlorophenethyl)-N-methylamine (1) with 3-chloromethyl-5-phenyl-1,2,4-oxadiazole (2) was investigated. Employment of an equimolar amount of 1 and 2 in the presence of potassium carbonate led to the expected tertiary amine 3 (N-[(3,4-dichlorophenyl)ethyl]-N-methyl-N-[(5-phenyl-1,2,4-oxadiazol-3-yl)methyl]amine), whereas an excess of 1 and prolonged reaction time resulted in ring fission of the oxadiazole system in 3 and finally in the formation of N′-benzoyl-N-[(3,4-dichlorophenyl)ethyl]-N-methylguanidine (4) and N,N′-bis[(3,4-dichlorophenyl)ethyl]-N,N′-dimethylmethanediamine (5). The structures of products 3–5 were determined by means of ¹H and ¹³C NMR-spectroscopy, mass spectrometry and IR-spectroscopy, for 3 (as picrate) and 4 also X-ray structure analysis was employed. A possible mechanism of the reaction pathway leading to compounds 4 and 5 is proposed.     

Reaction of alkynylsilanes with CuCl in polar solvents leading to alkynyl group transfer from Si to Cu

The reaction of 1-phenyl-2-trimethylsilylethyne with CuCl at 80–100°C in N,N-dimethylformamide (DMF) or N,N-dimethylimidazolidinone (DMI) yielded the alkynylcopper species [Cu₂Cl(CCPh)]_n (1) in 56–63% yields. Heating 1 at 80°C under aerobic conditions gave 1,4-diphenyl-1,3-butadiyne in 82% yield via an oxidative coupling of the phenylethynyl ligands.     

Effect of a third component on the interactions in a binary mixture determined from the fluctuation theory of solutions

The Kirkwood–Buff (KB) theory of solution is applied to a ternary mixture by deriving explicit expressions for the various Kirkwood–Buff integrals (KBIs) and the corresponding excesses of the number of molecules around central ones. However, the ideal solution should be considered non-aggregated, and the above expressions for the excesses provide non-zero values for such a case. For this reason, in order to obtain information about clustering one must subtract from the traditional excesses those which correspond to a reference state, thus ensuring that for an ideal mixture the excesses are zero. The expressions derived for the latter excesses have been applied to the investigation of the N,N-dimethylformamide–methanol–water mixture, to conclude that: (i) in the vicinity of the water molecules there are excesses of water and N,N-dimethylformamide molecules and a deficit of methanol molecules; (ii) in the vicinity of the methanol molecules there are excesses of methanol and N,N-dimethylformamide molecules and a deficit of water molecules; (iii) in the vicinity of the N,N-dimethylformamide molecules there are excesses of methanol and water molecules and a deficit of N,N-dimethylformamide molecules; (iiii) the excesses of N,N-dimethylformamide around water and methanol molecules and those around N,N-dimethylformamide are weakly dependent on the concentration of the third component in a large range of concentrations of the latter, and these results are compatible with the existence of N,N-dimethylformamide–water and N,N-dimethylformamide–alcohol complexes.     

Metal complexes of biologically important ligands: Synthesis of amino acidato complexes of Pd containing a C,N-cyclometallated group as an ancillary ligand

New amino acidato complexes of Pd^II of stoichiometry [Pd(C---N)(Aa)] (C---N=C,N-cyclometallated ligand, Aa = N,O-amino acidato ligand) have been obtained by reaction of [Pd(C---N)(acac)] (C---N=N,N-dimethylbenzylamine-C²,N (dmba) (1) or N,N-dimethyl(S--phenylethyl)amine-C²,N (S-dmphea) (2)) with glycine, chiral amino acids (alanine, phenylalanine and valine), and amino acid derivatives (N-acetylglycine and N-acetyl-,β-dehydroalanine) in MeOH. The compounds are characterized by IR, ¹H and ¹³C NMR. The geometry of these complexes has been unambiguously determined by NOE difference experiments and NOESY measurements.     

Zr-TUD-1: A novel heterogeneous catalyst for the Meerwein–Ponndorf–Verley reaction

A series of Schiff-base complexes has been synthesized by the condensation of 1,2-diaminocyclohexane with salicylaldehyde, 2-pyridinecarboxaldehyde, and 2-hydroxy-1-naphthaldehyde, followed by the metallation with manganese (1, 2, 3a), cobalt (3b), copper (3c) and iron (3d) salts. These Schiff-base ligands L₁–L₃ and complexes 1, 2, 3a–d were then characterized by IR, ¹H NMR, ¹³C NMR, UV–vis spectra, and DSC measurement. Schiff-base Mn complex (3a) resulting from N,N′-bis(2-hydroxy-1-naphthalidene)cyclohexanediamine (L₃) ligand was considerably active for the catalytic epoxidation of styrene under mild conditions, in which the highest yield of styrene oxide reached 91.2 mol%, notably higher than those achieved from simple salt catalysts Mn(Ac)₂·4H₂O and MnSO₄·H₂O. However, another two salen–Mn complexes 1 and 2 derived from ligands N,N′-bis(salicylidene)cyclohexanediamine (L₁) and N,N′-bis(2-pyridine carboxalidene)cyclohexanediamine (L₂) exhibited relatively poor activity under identical experimental conditions.     

The synthesis of 1-amino-2-hydroxy- and 2-amino-1-hydroxy-substituted ethylene-1,1-bisphosphonic acids and their N-methylated derivatives

A synthesis of 2-amino-1-hydroxyethylene-1,1-bisphosphonic acid 3 has been developed from N-phthaloylglycine via dimethyl 2-(N-phthaloylamino)acetylphosphonate 1. The preparation of the N-methylated and N,N-dimethylated derivatives 4 and 5 has been achieved by the reaction of 3 with formic acid and formaldehyde. The synthesis of 1-amino-2-hydroxyethylene-1,1-bisphosphonic acid 9 (R=R′=H) and its N-methylated and N,N-dimethylated analogues has been achieved by the reaction of phosphorus trichloride and phosphorous acid with the appropriate O-benzyl protected hydroxyacetamide, followed by catalytic hydrogenolysis of the protecting group.     

Syntheses, crystal structure and ab initio calculations of two new phosphoric triamides

The reaction of N-benzoylphosphoramidic dichloride with piperidine and 4-methylpiperidine lead to PhC(O)N(H)P(O)R₂ with R=piperidine (1) and R=4-methylpiperidine (2) as N-benzoyl-N′,N″-bis(piperidine) phosphoric triamide and N-benzoyl-N′,N″-bis(4-methylpiperidine) phosphoric triamide, respectively. The products have been characterized by ¹H, ¹³C, ³¹P NMR spectra, and by elemental analysis. The crystalline solid for (1) and (2) consists surprisingly of four and two independent molecules, respectively. There is a disorder in one amine group due to ring inversion in each conformer in compound 1. In the solid state, comparable magnitudes for the stabilization of the stable conformers for the more or less discrete molecules, the polarization effects, hydrogen bonding and the packing effects could be anticipated.

The geometry of compound (1) optimized by density functional calculations at the B3LYP/6-31++G* (d,p) level, is in good agreement with data obtained from X-ray crystallography.     

New synthetic method to 1,2-benzisothiazoline-3-one- 1,1-dioxides and 1,2-benzisothiazoline-3-one-1-oxides from N-alkyl(o-methyl) arenesulfonamides

Various N-alkylsaccharins were easily prepared in moderate to good yields by the reaction of N-alkyl(o-methyl)arenesulfonamides with (diacetoxyiodo)benzene in the presence of iodine under irradiation with a tungsten lamp (W-hν). On the other hand, irradiation of N-alkyl(o- methyl)arenesulfonamide derivatives bearing various subslituents on the aromatic ring with a high- pressure mercury lamp (Hg-hν), in the presence of (diacetoxyiodo)benzene and iodine gave the corresponding N-alkyl-1,2-benzisothiazoline-3-one-1-oxide derivatives in moderate yields, together with N-alkyl-1,2-benzisothiazoline-3-one-1,1-dioxide (saccharin) derivatives.     

Structural and spectral characterization of two 1-phenyl-1,2-propanedione bis{N(4)-alkylthiosemicarbazones}

1-phenyl-1,2-propanedione bis{N(4)-methyl- and {N(4)-ethylthiosemicarbazone}, H₂Pm4M and H₂Pm4E, respectively, have been prepared, studied spectroscopically (¹H NMR, ultraviolet and infrared) and their crystal structures solved. Intermoiety hydrogen bonding does not occur in H₂Pm4M and H₂Pm4E, in contrast to the analogous bis{N(4)-thiosemicarbazones} prepared from 1-phenylglyoxal. The two thiosemicarbazone moieties are on the opposite side of the carbon–carbon backbone, but the N(4)Hs intramolecularly hydrogen bond to the imine nitrogen for each moiety.     

MP2 study of substituent effects of 2-substituted alkyl ethyl methylcarbamates in homogeneous, unimolecular gas phase elimination reaction

Møller-Plesset MP2/6-31G method was used to examine the gas-phase elimination of 2-substituted alkyl ethyl N,N-dimethylcarbamates. The results of these calculations support a concerted non-synchronous six-membered cyclic transition state mechanism for carbamates containing a C_β–H bond at the alkyl side of the ester. These substrates produce the N,N-dimethylcarbamic acid and the corresponding olefin. The unstable intermediate, N,N-dimethylcarbamic acid, rapidly decomposes through a four-membered cyclic transition state to dimethylamine and CO₂ gas. Correlation of the logarithm of theoretical rate coefficients against original Taft's σ* values gave an approximate straight line (ρ*=−1.39, r=0.9558 at 360 °C). In addition to this fact, when log k_rel is plotted against the theoretical log k_rel for 2-substituted ethyl N,N-dimethylcarbamates a reasonable straight line (r=0.9919 at 360 °C) is obtained, suggesting similar mechanism.     

Reaktionen von bis(η-cyclopentadienyl)zirconiumhydriden mit (iminoacyl)zirconocen-komplexen

The reaction of imidoylzirconocene complexes with zirconocene hydrides yields (N-alkylamido)zirconocene complexes. For a mechanistic study, the specifically substituted imidoylzirconocene complexes 3b–3d have been prepared and treated with the oligomeric metal hydrides (Cp₂ZrH₂)_x (1b) and (Cp₂ZrHCl)_x (1c). (N-Benzyl formimidoyl)zirconocene chloride (3b) was obtained by treating 1c with benzyl isonitrile 2a. Treatment of dimethylzirconocene with 2a gave (N-benzyl acetimidoyl)methylzirconocene (3c), which was treated with PhICl₂ to give (N-benzylacetimidoyl)zirconocene chloride (3d). The reaction of 3d with (Cp₂ZrH₂)_x (1b) yielded (N-benzyl-N-ethylamido)zirconocene chloride (4b) as the only identified product. A 1/1 mixture of 4b and methylzirconocene chloride was obtained upon treatment of 3c with (Cp₂ZrHCl)_x (1c); in contrast, the reaction of 1c with 3b gave an equimolar mixture of Cp₂ZrCl₂ and (N-benzyl-N-methylamido)zirconocene chloride (4c). Reaction paths through binuclear (μ-CHR′=NR) zirconocene intermediates are proposed to explain these experimental observations.     

Conformational isomers in the photocyclodimerization of N-acylated dibenz[b,f]azepine derivatives

The benzophenone-sensitised photodimerizations of N-acetyl- and N-propionyldibenz[e,f]azepine were investigated in acetone as the solvent. In both the systems, the ¹H NMR analysis of the products revealed two isomeric photodimers differing in the chemical shifts and coupling constants of the cyclobutane protons, aromatic protons and the protons of the acetyl or propionyl group. Upon raising the temperature to ca. 70 °C the signals merge. The findings can be ascribed to a single thermally restricted conformational process such as the rotation about the C–N amide bond. The process exhibits free activation energies: ΔG^#=(74±2) kJ mol⁻¹ (N-acetyl) and ΔG^#=(70±2) kJ mol⁻¹ (N-propionyl).     

Theoretical study of the elimination kinetics of several 2-substituted ethyl N,N-dimethylcarbamates in the gas phase, [(CH3)2NCOOCH2CH2Z, Z=CH2Cl, C≡CH, C≡N]

The theoretical studies of the gas-phase elimination of 2-substituted ethyl N,N-dimethylcarbamates (Z=CH₂Cl, C≡CH, C≡N) were performed using ab initio MP2/6-31G and MP2/6-31G(d) levels of theory. The gas phase elimination reaction of these carbamates yields N,N-dimethylcarbamic acid and the corresponding substituted olefin in a rate-determining step. The intermediate N,N-dimethylcarbamic acid is unstable and rapidly decomposes through a four-membered cyclic transition state to dimethylamine and CO₂ gas. The results of these calculations suggest a mechanism to be concerted, asynchronous, and a six-membered cyclic transition state structure. Plotting the relative theoretical rate coefficients against Taft's σ* values gave an approximate straight line (ρ*=0.4057, r=0.9894 at 360 °C). The correlation between experimental log k_rel vs. theoretical log k_rel. for these 2-substituted ethyl N,N-dimethylcarbamates gave an approximate straight line (r=0.9715 at 360 °C), suggesting the same type of mechanism.     

Ethylene oligomerization by diimine iron(II) complexes/EAO

The catalytic properties of a series of Fe(II) diimine complexes (diimine=N,N′-o-phenylenebis(salicylideneaminato), N,N′-ethylenebis(salicylideneaminato), N,N′-o-phenylenebisbenzal, N,N′-ethylenebisbenzal) in combination with ethylaluminoxane (EAO) for ethylene oligomerization have been investigated. Treatment of the iron(II) complexes with EAO in toluene generates active catalytic systems in situ that oligomerize ethylene to low-carbon olefins. The effects of reaction temperature, ratios of Al/Fe and reaction periods on catalytic activity and product distribution have been studied. The activity of complex FeCl₂(PhCH=o-NC₆H₄N=CHPh) with EAO at 200°C is 1.35×10⁵ g oligomers/mol Fe·h, and the selectivity of C_4–10 olefins is 84.8%.     

Effect of “topotactic” reduction product of molybdenum disulfide on catalytic activity of metallocene catalyst for olefin polymerization

N,N-Dimethylanilinium salt of molybdenum disulfide (MoS₂) was developed as a novel cocatalyst for metallocene catalysts. The cocatalyst is composed of N,N-dimethylanilinium ion as a cationic part and “topotactic” reduction product of MoS₂, obtained by acquisition of an electron by neutral host lattice of MoS₂ without structural alteration, as an anionic part. In ethylene polymerization, addition of the N,N-dimethylanilinium salt of MoS₂ to the bis(indenyl)zirconium dichloride (Ind₂ZrCl₂)/triethylaluminum (Et₃Al) catalyst improved the catalytic activity per mmol of Ind₂ZrCl₂. The catalytic activity of this system activated by addition of the cocatalyst depended significantly on the amount of the cocatalyst and the N,N-dimethylanilinium ion content in the cocatalyst. Poly(ethylene) and poly(ethylene-co-1-hexene) obtained with the metallocene catalyst activated by addition of the cocatalyst have typical features such as narrow molecular weight distribution and narrow composition distribution like polymers obtained with conventional metallocene catalysts.     

Photochemistry of N-acetyl and N-benzoyl carbazoles: photo-Fries rearrangement and photoinduced single electron transfer

The photochemistry of two N-acyl carbazoles, N-acetyl and N-benzoyl carbazole, in different pure and mixed organic solvents is studied. Depending on the properties of the medium, photo-Fries rearrangement and photoinduced single electron transfer (PSET) processes are observed yielding the former 1-acyl and 3-acyl carbazoles and the latter 3-chloro-N-acyl carbazole. k_SV, k_Q and φ for fluorescence emission, conversion of N-acyl carbazole and product formation yields have been measured as well as the properties of the N-acyl carbazole radical cations formed during the PSET process (laser flash photolysis experiments). The Rehm-Weller equation is used in order to evaluate the ΔG°_ET of the PSET processes.     

Morphology and optical properties of MgO thin films on Mo(0 0 1)

The photophysical properties of N-(1-naphthyl)-carbazole (1-NACZ), N-(2-naphthyl)-carbazole (2-NACZ), N-(1-naphthyl)-benzimidazole (1-NABI) and N-(2-naphthyl)-benzimidazole (2-NABI) were studied. The emission wavelengths of 1-NACZ and 2-NACZ were very sensitive to the polarity of solvents. The magnitude of change in the dipole moment was calculated based on the Lippert–Mataga equation. 1-NACZ and 2-NACZ had higher change in the dipole moment than that of 1-NABI and 2-NABI . The optical properties, including fluorescence quantum yield and fluorescence decay times, were determined in different polarity solvents. These gave the evidence about the intramolecular charge transfer character in the excited singlet state of 1-NACZ and 2-NACZ.