A novel ionic complex with insensitivity to moisture and air, bis-[1-butyl-2-diphenylphosphanyl-3-methylimidazolium]tetrachloridorhodium(III) hexafluorophosphate ( 1A ), has been synthesized and fully characterized. The single-crystal X-ray diffraction analysis shows that 1A is composed of the Rh(III)-complex cation and the counter-anion of PF 6 − . The complex cation has highly symmetrical Rh III -centered octahedron geometry with four Cl atoms in the equatorial plane and two imidazolium-substituted phosphine ligands in the axial position. The catalytic performance of 1A , which could be tailored by the ligands and the solvents, was investigated toward the biphasic hydroformylation of 1-octene. It was found that the presence of the hemilabile hybrid P,N-ligand of 3 (1-(2′-piperid-1′-yl-ethyl)-2-diphenylphosphino-3-methylimidazolium hexafluorophosphate), as a kind of ligand-functionalized ionic liquids (ILs), could dramatically spur the catalytic activity of 1A . The use of the RTIL of [PEmim]BF 4 (1-(2′-piperid-1′-yl-ethyl)-3-methylimidazolium tetrafluoroborate) as the solvent not only fulfilled the efficient biphasic hydroformylation of 1-octene, but also guaranteed the successful recovery and recycling of the ionic compositions of 1A and 3 .

An ionic phosphine-ligated rhodium(III) complex as the efficient and recyclable catalyst for biphasic hydroformylation of 1-octene

1-Methylhomopiperazine was coupled with a series of diazonium salts to afford the 4-methyl-1-[2-aryl-1-diazenyl]-1,4-diazepanes (6), a new series of triazenes. These compounds are, in the main, stable crystalline solids (some of the series are stable oils), and they have been characterized by 1H and 13C NMR spectroscopy, IR spectroscopy, and mass spectrometry. NMR assignments were determined by 2D NMR and variable-temperature NMR experiments and by comparison with model compounds. A second series of new compounds, namely, 1,4-di-[2-aryl-1-diazenyl]-1,4-diazepanes (5), were prepared by coupling unsubstituted homopiperazine (1,4-diazepane) with 2 molar equivalents of the diazonium salt and were similarly characterized. The crystal and molecular structure of the parent member of this bis-triazene series (5, X = H) has been determined by single-crystal X-ray diffraction analysis.Key words: triazene, bis-triazene, diazenyl, bis-diazenyl, diazonium salt, NMR, diazepane.

Synthesis and characterization of a series of 4-methyl-1-[2-aryl-1-diazenyl]-1,4-diazepanes and 1,4-di-[2-aryl-1-diazenyl]-1,4-diazepanes

Piperazine-functionalized ordered mesoporous polymer as highly active and reusable organocatalyst for water-medium organic synthesis

Thermo-electro-chemical storage (TECS) of solar energy

1-Methylpiperazine was coupled with a series of diazonium salts to afford the 1-methyl-4-[2-aryl-1-diazenyl]piperazines (2), a new series of triazenes, which have been characterized by 1H and 13C NMR spectroscopy, IR spectroscopy, and elemental analysis. Assignment of the chemical shifts to specific protons and carbons in the piperazine ring was facilitated by comparison with the chemical shifts in the model compounds piperazine and 1-methylpiperazine and by a HETCOR experiment with the p-tolyl derivative (2i). A DEPT experiment with 1-methylpiperazine (6) was necessary to distinguish the methyl and methylene groups in 6, and a HETCOR spectrum of 6 enabled the correlation of proton and carbon chemical shifts. Line broadening of the signals from the ring methylene protons is attributed to restricted rotation around the N2-N3 bond of the triazene moiety in 2. The second series of triazenes, the ethyl 4-[2-phenyl-1-diazenyl]-1-piperazinecarboxylates (3), have been prepared by similar diazonium coupling to et...

Synthesis and characterization of a series of 1-methyl-4-[2-aryl-1-diazenyl]piperazines and a series of ethyl 4-[2-aryl-1-diazenyl]-1-piperazinecarboxylates

The crystal structures of methyl 4-{(E)-2-(4-methylpiperazino)-1-diazenyl}benzoate (2a) and 1,4-di[(E)-2-(2-nitrophenyl)-1-diazenyl]piperazine (3a) have been determined by single crystal X-ray diffraction analysis. The bis-triazene (3a) adopts an unusual pseudo-boat conformation in the piperazine ring, with a dihedral angle of 52.20(0.06)° between the two planes defined within the piperazine ring. The crystal structures of 2a and 3a are compared with the structure of the triazene (4) and the closely related bis-triazene (5). The piperazine ring of 2a adopts a typical chair conformation, whereas the piperazine ring of 3a adopts an unusual boat conformation. Crystal data: 2a C13H18N4O2, monoclinic, space group P21
 /n, a = 13.849(3) A, b = 6.577(1) A, c = 14.904(3) A, α = 90°, β = 96.098(3)°, γ = 90° and V = 1,349.8(4) A3, for Z = 4. 3a C16H16N8O4, triclinic, space group P-1, a = 7.6066(6) A, b = 8.3741(7) A, c = 14.507(1) A, α = 78.673(1)°, β = 81.877(1)°, γ = 73.445(1)° and V = 865.0(1) A3, for Z = 2. The crystal structures of methyl 4-{(E)-2-(4-methylpiperazino)-1-diazenyl}benzoate (2a) and 1,4-di[(E)-2-(2-nitrophenyl)-1-diazenyl]piperazine (3a) have been determined by single crystal X-ray diffraction analysis.

An X-ray Crystallographic Study of the Related Triazenes, 1,4-Di[( E )-2-(2-nitrophenyl)-1-diazenyl]piperazine and Methyl 4-{(E)-2-(4-methylpiperazino)-1-diazenyl}benzoate

A series of 1,4-di-[2-aryl-1-diazenyl]-2-methylpiperazines (4a–n) have been synthesized by the reaction of 2-methylpiperazine with 2 equiv. of the appropriate diazonium salt. The products have been characterized by IR and NMR spectroscopy, and the molecular composition has been verified by HR-EIMS, with accurate mass measurement of the molecular ion. The presence of a chiral centre at C2 of the piperazine ring in the bistriazene 4 creates a multitude of diastereotopic protons in the methylene groups of the piperazine ring, as evidenced by the complexity of the NMR spectra, which nevertheless can be fully assigned in some cases, such as the tolyl- (4h) and phenyl- (4j) derivatives. These two compounds also show a discrimination between the two N-arydiazenyl groups, as evidenced by the doubling of several aromatic-carbon signals in the 13C NMR spectra. The assignment of the proton and carbon signals in 4h and 4j has been aided by the use of 2D NMR spectroscopy. A DEPT spectrum of 4j clearly discriminates th...

Triazene derivatives of (1,x)-diazacycloalkanes. Part X. Synthesis and characterization of a series of 1,4-di[2-aryl-1-diazenyl]-trans-2,5-dimethylpiperazines

Rhodium phosphino-enolate complexes as chemo- and regioselective catalysts for the hydroformylation of styrenes

A thermally regenerative fuel cell (TRFC) on board a long-haul truck would convert waste heat from the engine or exhaust into electrical energy. We propose a TRFC in which waste-heat drives the endothermic dehydrogenation of a secondary benzylic alcohol to the corresponding ketone in a catalytic reaction chamber adjacent to the engine. 1-Phenyl-1-propanol has been identified as a suitable alcohol. In a fully functioning TRFC, the H2 produced from the dehydrogenation will be sent to the fuel cell's anode, while the ketone, propiophenone, will be sent to the cathode to serve as an oxidant, together producing electricity to charge a battery that could power auxiliary vehicle components. The electrochemical reduction of the ketone back to the original benzylic alcohol would take place at the cathode. For such a system to be viable, both reactions must be very selective and rapid. Herein, the initial development of this system and the implications of catalyst and benzylic alcohol choice on the performance of both of these reactions are discussed. For the dehydrogenation of 1-phenyl-1-propanol, Pd/SiO2 offers the highest selectivity (99.65%) at 200 °C. For the re-hydrogenation of the analogous ketone, propiophenone, palladium catalysts offer the highest selectivity, although the highest rates are observed for platinum immobilized on Vulcan XC-72 carbon support; surface modification of commercial catalysts with n-butyl tin also affects the selectivity and rate in a manner that depends on the choice of catalyst support. It has also been shown that the electronic and steric properties of the phenyl ring substituents and the identity of the alkyl chain affect the rate and selectivity.

Vanessa Renee Little

Papers

Synthesis and characterization of a series of 1-methyl-4-[2-aryl-1-diazenyl]piperazines and a series of ethyl 4-[2-aryl-1-diazenyl]-1-piperazinecarboxylates

An X-ray Crystallographic Study of the Related Triazenes, 1,4-Di[( E )-2-(2-nitrophenyl)-1-diazenyl]piperazine and Methyl 4-{(E)-2-(4-methylpiperazino)-1-diazenyl}benzoate

Triazene derivatives of (1,x)-diazacycloalkanes. Part X. Synthesis and characterization of a series of 1,4-di[2-aryl-1-diazenyl]-trans-2,5-dimethylpiperazines

Rhodium phosphino-enolate complexes as chemo- and regioselective catalysts for the hydroformylation of styrenes

Towards an organic thermally regenerative fuel cell for truck engines