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A N2 coordination to titanocene monochloride, [Cp2TiCl], in an ionic liquid (IL), 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate (Pyr4FAP), was detected by frozen solution E...

It has been before reported that, in addition to hydration of nitriles, the Fe-type nitrile hydratase (NHase) also catalyzes the hydrolysis of tert-butylisocyanide (tBuNC). In order to investigate the unique isocyanide hydrolysis by NHase, we prepared three related Co(III) model complexes, PPh4[Co(L)] (1), PPh4[Co(L-O3)] (2), and PPh4[Co(L-O4)] (3), where L is bis(N-(2-mercapto-2-methylpropionyl)aminopropyl)sulfide. The suffixes L-O3 and L-O4 indicate ligands with a sulfenate and a sulfinate and with two sulfinates, respectively, instead of the two thiolates of L. The X-ray analyses of 1 and 3 reveal trigonal bipyramidal and square pyramidal structures, respectively. Complex 2, however, has five-coordinate trigonal-bipyramidal geometry with η2-type S–O coordination by a sulfenyl group. Addition of tBuNC to 1, 2, and 3 induces an absorption spectral change as a result of formation of an octahedral Co(III) complex. This interpretation is also supported by the crystal structures of PPh4[Co(L-O4)(tBuNC)] (4) ...

Incorporation of the tridentate phosphine-enamidoiminophosphorane onto cobalt(II) produces tetrahedral Co(NpNPiPr)Cl, 1, which upon reduction under dinitrogen generates the T-shaped, paramagnetic Co(I) complex Co(NpNPiPr), 2. This paramagnetic T-shaped derivative is in equilibrium with the paramagnetic dinitrogen derivative Co(NpNPiPr)(N2), 3, which can be detected by IR and low-temperature UV–vis spectroscopy. Both 1 and 2 act as homogeneous catalysts for the conversion of molecular nitrogen into tris(trimethylsilyl)amine (N(SiMe3)3) (∼200 equiv, quantified as NH4Cl after hydrolysis) in the presence of excess KC8 and Me3SiCl at low temperatures.

The catalytic conversion of CO2 to useful compounds is of great importance from the viewpoint of global warming and development of alternatives to fossil fuels. Electrochemical reduction of CO2 using aromatic N-heterocylic molecules is a promising research area. We describe a high performance electrochemical system for reducing CO2 to formate, methanol, and CO using imidazole incorporated into a phosphonium-type ionic liquid-modified Au electrode, imidazole@IL/Au, at a low onset-potential of −0.32 V versus Ag/AgCl. This represents a significant improvement relative to the onset-potential obtained using a conventional Au electrode (−0.56 V). In the reduction carried out at −0.4 V, formate is mainly generated and methanol and CO are also generated with high efficiency at −0.6 ∼ −0.8 V. The generation of methanol is confirmed by experiments using 13CO2 to generate 13CH3OH. To understand the reaction behavior of CO2 reduction, we characterized the reactions by conducting potential- and time-dependent in situ ...

Heat-treatment of nano-boehmite intercalated with monoethanolamine derivatives (NBM-MEA) affects its photoluminescence properties. The photoluminescence band of NBM-MEA undergoes a red-shift with an increase in temperature. On the basis of IR and ESR spectroscopic behavior and analysis of time-resolved photoluminescence decay, it is concluded that the emission band originates from the F+ center as singly ionized oxygen vacancies in the boehmite structure and from carbon impurities due to decomposition of monoethanolamine derivatives.

Coordination of N2 to [(Cp2TiCl)2] in a non-coordinating ionic liquid, Pyr4FAP, was studied by UV-vis/NIR and EPR spectroscopies. [(Cp2TiCl)2] is in equilibrium between monomeric [Cp2TiCl] and dimeric species [(Cp2TiCl)2]. The frozen solution EPR spectrum revealed the coordination of N2 to [Cp2TiCl], suggesting that Pyr4FAP promotes N2 coordination to the Ti(III) center.

Reported here is the N2 cleavage of a one-electron oxidation reaction using trans-[Mo(depe)2 (N2 )2 ] (1) (depe=Et2 PCH2 CH2 PEt2 ), which is a classical molybdenum(0)-dinitrogen complex supported by two bidentate phosphine ligands. The molybdenum(IV) terminal nitride complex [Mo(depe)2 N][BArf4 ] (2) (BArf4 =B(3,5-(CF3 )2 C6 H3 )4 ) is synthesized by the one-electron oxidation of 1 upon addition of a mild oxidant, [Cp2 Fe][BArf4 ] (Cp=C5 H5 ), and proceeds by N2 cleavage from a MoII -N=N-MoII structure. In addition, the electrochemical oxidation reaction for 1 also cleaved the N2 ligand to give 2. The dimeric Mo complex with a bridging N2 is detected by in situ resonance Raman and in situ UV-vis spectroscopies during the electrochemical oxidation reaction for 1. Density-functional theory (DFT) calculations reveal that the unstable monomeric oxidized MoI species is converted into 2 via the dimeric structure involving a zigzag transition state.

Electrochemical synthesis of NH3 from dinitrogen and protons from water by using Cp2TiCl2 supported in a hydrophobic ionic liquid, 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate ([C9H20N]+[(C2F5)3PF3]−), was achieved in a solid polymer electrolyte (SPE) cell under ambient conditions. The yield of NH3 per Cp2TiCl2 and current efficiency are 27% and 0.2%, respectively, which are improved in comparison with those reported previously. Keywords: Dinitrogen fixation, Ionic liquid, Transition metal complex, Ammonia

A novel nickel(II) complex [Ni(L)2 Cl]Cl with a bidentate phosphinopyridyl ligand 6-((diphenylphosphino)methyl)pyridin-2-amine (L) was synthesized as a metal-complex catalyst for hydrogen production from protons. The ligand can stabilize a low Ni oxidation state and has an amine base as a proton transfer site. The X-ray structure analysis revealed a distorted square-pyramidal Ni(II) complex with two bidentate L ligands in a trans arrangement in the equatorial plane and a chloride anion at the apex. Electrochemical measurements with the Ni(II) complex in MeCN indicate a higher rate of hydrogen production under weak acid conditions using acetic acid as the proton source. The catalytic current increases with the stepwise addition of protons, and the turnover frequency is 8400 s(-1) in 0.1 m [NBu4 ][ClO4 ]/MeCN in the presence of acetic acid (290 equiv) at an overpotential of circa 590 mV.

An unstable diiron(II,II) complex possessing O2 binding ability at low temperature was encapsulated and stabilized in an ammonium-type ionic liquid layer polymerized on an electrode. The encapsulated complex revealed catalytic reactivity for four-electron reduction of O2 at an ambient temperature in aqueous solution.

A blue photoluminescent nano boehmite was prepared by a solvothermal reaction of aluminum hydroxide gel in monoethanolamine (MEA) at a low temperature of 120 °C for 6 h; it shows a photoluminescence emission at 420 nm with excitation of 360 nm that is attributed to the formation of the carbamate derivative of MEA.

We report the synthesis and luminescent properties of halide-bridged tricopper(I) complexes with a polyaza cryptand having three 2,6-bis(aminomethyl)pyridyl spacers. The asymmetric {Cu3X3} structur...

A Co(III) complex possessing selective nitric oxide (NO) capturing ability was immobilized onto a bulky phosphonium type ionic liquid-modified Au electrode, IL/Au, (Co@IL/Au), which was confirmed b...

Solvothermal reaction of aluminum hydroxide gel (AHG) in monoethanolamine (MEA) was studied at several temperatures (100, 120, 150, and 200 °C) in several reaction times (2, 3, 4, 5, 6, and 13 h). The reaction product prepared at a low temperature of 120 °C in the reaction time more than 6 h gave a blue photoluminescence nanoboehmite intercalated with monoethanolamine derivatives (BM-MEA) in the colloidal solution, which showed a photoluminescence emission centered at 420 nm with an excitation of 360 nm. The powdery samples recovered from the reaction products were characterized by using elemental analysis, XRD analysis, IR spectroscopy, thermogravimetric (TG)-DTA, 13C and 27Al CP/MAS NMR spectroscopies, N2 gas adsorption/desorption isotherm, SEM and TEM images, and photoluminescence spectroscopy. The X-ray diffraction revealed that the basal space in BM-MEA was expanded from 0.61 to 1.2 nm by intercalation of MEA derivatives to boehmite, and the IR and 13C CP/MAS NMR spectra determined that the intercalated MEA derivatives are protonated- and carbamate-substituted MEAs, which are formed in the layers through a covalent bond with Al–OH groups on boehmite surface. The empirical formula of BM-MEA was estimated to be AlO(OH)0.82(OCH2CH2NH3 +)0.05(OCH2CH2NHCOO−)0.13 on the basis of the elemental TG-DTA and IR spectral analyses. We discuss the reaction mechanism of a unique blue photoluminescence BM-MEA formed by proceeding in CO2–H2O–alkanolamine system.

Redox behaviors of monomeric and dimeric titanocenes, [Cp2TiCl2] (1) and [(Cp2TiCl)2] (2), were investigated in two different types of ionic liquid (IL) with non-coordinating and coordinating anions, 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)- trifluorophosphate (Pyr4FAP) and 1-butyl-1-methylpyrrolidinium triflate (Pyr4OTf), respectively. UV-vis/NIR spectra obtained during the electrochemical reduction of 1 revealed that it was converted to 2 in the ILs through the formation of [Cp2TiCl] (3). In Pyr4OTf, 3 was coordinated with the OTf anion in the η1-O mode, during the electrochemical reductions of Ti(IV/III) process, whereas 3 was not coordinated by the FAP anion in Pyr4FAP. Additionally, electrochemical NH3 synthesis was carried out in a solid polymer electrolyte cell by using a gas diffusion electrode coated with Pyr4FAP or Pyr4OTf containing titanocenes. The electrochemical reduction using 2 in Pyr4FAP at −1.5 V (vs. Ag/AgCl) gave a high yield (34 % at 29.9 C) of NH3 per Ti ion. The electrochemical reduction using 1 in Pyr4OTf gave a 6.8 % yield of NH3 per Ti ion at 20 °C. These findings indicate that the use of an IL with a non-coordinating anion such as FAP contributes to the coordination and reduction of N2 to titanocenes.