Organometallic Reactants Research Articles

Size-controllable Rh2P nanoparticles on reduced graphene oxide toward highly hydrogen production

Abundant of defective regions and oxygen-containing groups on graphene oxide (GO) could promote the nucleation and growth of metallic nanoparticles. In this work, the composite catalyst is synthesized by pyrolysis of the mixture powder of GO and rhodium organometallic reactant at 900 °C, Ar atmosphere and low pressure, in which dispersive Rh2P nanoparticles are uniformly attached on reduced graphene oxide (Rh2P/RGO). The sizes of Rh2P nanoparticles are controllable by adjusting the mass proportion of reactants. For the optimized size of Rh2P nanoparticles at 6.0 nm, only 11.7 and 10.3 mV of the overpotentials are required at the current density of 10 mA cm−2 in 0.5 M H2SO4 and 1 M KOH electrolytes, respectively, exhibiting superior HER activity over the commercial Pt/C. Theoretical calculations indicate that the hydrogen adsorption free energy of Rh2P/RGO composites is close to zero, and Bede charge analysis confirms the accelerated electron transport between the RGO and Rh2P. Therefore, the introduction of RGO substrate could not only promote a uniform distribution and tunable size of Rh2P NPs, but also be advantageous to the electron transport from RGO to Rh2P NPs, and a favorable H2 evolution during the HER process. This work provides a facile strategy to control the size of metal phosphide nanoparticles on RGO for the design of advanced HER electrocatalysts.

Electrochemical implications of modulating the solvation shell around redox active organic species in aqueous organic redox flow batteries

Organic and organometallic reactants in aqueous electrolytes, being composed of earth-abundant elements, are promising redox active candidates for cost-effective organic redox flow batteries (ORFBs). Various compounds of ferrocene and methyl viologen have been examined as promising redox actives for this application. Herein, we examined the influence of the electrolyte pH and the salt anion on model redox active organic cations, bis((3-trimethylammonio) propyl)- ferrocene dichloride (BTMAP-Fc) and bis(3-trimethylammonio) propyl viologen tetrachloride (BTMAP-Vi), which have exhibited excellent cycling stability and capacity retention at ≥1.00 M concentration [E. S. Beh, et al. ACS Energy Lett. 2, 639-644 (2017)]. We examined the solvation shell around BTMAP-Fc and BTMAP-Vi at acidic and neutral pH with SO42-, Cl-, and CH3SO3- counterions and elucidated their impact on cation diffusion coefficient, first electron transfer rate constant, and thereby the electrochemical Thiele modulus. The electrochemical Thiele modulus was found to be exponentially correlated with the solvent reorganizational energy (λ) in both neutral and acidic pH. Thus, λ is proposed as a universal descriptor and selection criteria for organic redox flow battery electrolyte compositions. In the specific case of the BTMAP-Fc/BTMAP-Vi ORFB, low pH electrolytes with methanesulfonate or chloride counterions were identified as offering the best balance of transport and kinetic requirements.

Vapor-Phase Infiltration inside a Microporous Porphyrinic Metal-Organic Framework for Postsynthesis Modification.

Vapor-phase infiltration (VPI), a technique derived from atomic layer deposition (ALD) and based on sequential self-limiting chemistry, is used to modify the stable microporous porphyrin-based metal-organic framework (MOF) MIL-173(Zr). VPI is an appealing approach to modifying MOFs by inserting reactants with atomic precision. The microporous nature and chemical stability of MIL-173 enable postsynthesis modification by VPI without MOF degradation even with extremely reactive precursors such as trimethylaluminum (TMA) and diethylzinc (DEZ). VPI proceeds through the diffusion of gaseous organometallic reactants TMA and DEZ inside the microporous framework, where they react with two kinds of chemical sites offered by the porphyrinic linker (phenolic and pyrrolic functions in the porphyrin core), without altering the crystallinity and permanent porosity of the MOF. 27Al NMR, UV-vis absorption, and IR spectroscopies are used to further characterize the modified material. Physisorption of both precursors is computationally simulated by grand canonical Monte Carlo methods and outlines the preferential adsorption sites. The impact of temperature, number of VPI cycles, and pulse length are investigated and show that aluminum and zinc are introduced in a saturating manner inside the MOF on both available reactive sites. The porosity prerequisite is outlined for VPI, which is proven to be much more effective than classical solution-based methods because it is solventless and fast, prevents workup steps, and allows reactions not possible by the classical solution approach.

Stability of Flow Battery Organic and Organometallic Reactant Molecules

Flow batteries for grid scale energy storage have been proposed as a technological solution to the intermittency of renewable energy sources. Aqueous-soluble organic reactant molecules composed of earth abundant elements, such as quinones, show promise for reducing system cost. In addition to low cost, sufficient capacity retention is also a prerequisite for the practical success of any flow battery chemistry. For inorganic systems, capacity retention is often determined by crossover of reactant species, whereas organic reactant crossover is typically lower due to a larger molecular size. Instead of crossover, reactant molecule stability can become the limiting factor for organic flow battery lifetime. In an operating battery, the lifetime of the reactant molecules depends on their chemical stability within the electrolyte as well as on their electrochemical stability during reduction and oxidation. We report here some of the results pertaining to the chemical and electrochemical stability of several organic and organometallic redox reactants in aqueous electrolytes. Chemical stability of molecules is monitored by detection of potential decomposition products by NMR spectroscopy during long duration storage at room temperature and at 60 °C. Electrochemical stability is determined by monitoring oxidation and reduction peak currents during standard three-electrode cyclic voltammetry in addition to capacity measurements in a custom designed two-electrode cell.

Unsymmetrical Saturated Ketones Resulting from Activations of Hydrocarbon C(sp3)–H and C(sp2)–H Bonds Effected by Cp*W(NO)(H)(η3-allyl) Complexes

C–H activations of a C(sp2)–H bond in benzene or a C(sp3)–H bond in mesitylene at 80 °C under CO pressure in undried solvents without rigorous exclusion of air and moisture can be effected with the 18e complexes Cp*W(NO)(H)(η3-CH2CHCMe2) (1), Cp*W(NO)(H)(η3-CH2CHCHMe) (2), and Cp*W(NO)(H)(η3-CH2CHCHPh) (3) (Cp* = η5-C5Me5). These activations are regiospecific and afford in the case of complex 1 good yields of the unsymmetrical saturated ketones 4-methyl-1-phenylpentan-1-one (5) and 1-(3,5-dimethylphenyl)-5-methylhexan-2-one (8), respectively, in which the alkyl groups result from hydrogenation of the allyl ligand in the organometallic reactant. Complex 2 reacts similarly, but complex 3 only produces the ketone from its reaction with CO in benzene. Theoretical calculations indicate that the key mechanistic feature of these conversions is the formation of a 16e η2-alkene complex which is generated by the regiospecific migration of the hydride ligand onto the tertiary carbon of the allyl ligand. The 16e Cp*W...

Ni@Fe2O3 heterodimers: controlled synthesis and magnetically recyclable catalytic application for dehalogenation reactions

Ni@Fe(2)O(3) heterodimer nanoparticles (NPs) were synthesized by thermal decomposition of organometallic reactants. After functionalization, these Ni@Fe(2)O(3) heterodimers became water soluble. The pristine heterodimeric NPs were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Mössbauer spectroscopy and magnetic susceptibility measurements. A special advantage of the heterodimers lies in the fact that nanodomains of different composition can be used as catalysts for the removal of environmentally hazardous halogenated pollutants.

Controlling phase formation in solids: rational synthesis of phase separated Co@Fe2O3 heteroparticles and CoFe2O4 nanoparticles

A wet chemical approach from organometallic reactants allowed the targeted synthesis of Co@Fe(2)O(3) heterodimer and CoFe(2)O(4) ferrite nanoparticles. They display magnetic properties that are useful for magnetic MRI detection.

Phase separated Cu@Fe3O4 heterodimer nanoparticles from organometallic reactants

Cu@Fe3O4 heteroparticles with distinct morphologies were synthesized from organometallic reactants. The shape of the magnetic domains could be controlled by the solvent and reaction conditions. They display magnetic and optical properties that are useful for simultaneous magnetic and optical detection. After functionalization, the Cu@Fe3O4 heterodimers become water soluble. The morphology, structure, magnetic and optical properties of the as-synthesized heterodimer nanoparticles were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), mössbauer spectroscopy, superconducting quantum interference device (SQUID) magnetometry, and dark field imaging. A special advantage of these heterodimers lies in the fact that the nanodomains of different composition can be used e.g. for the formation of nitric oxide (NO) through the Cu domain and heterodimer nanoparticles can be removed from the reaction mixture by means of the magnetic domain (Fe3O4).

Regioselectivity, scope, and limitations of the addition of organolithium and allylmagnesium reagents to 1 H-pyridine-2-thiones; access to 3,4-, 3,6-, and 5,6-dihydropyridine-2-thiones

Organolithium and lithium allyldibutylmagnesate reagents add to readily available NH, NMe, NBn, and NPh substituted pyridine-2-thiones yielding 4- and/or 6-substituted 3,4- or 3,6-dihydropyridine-2-thiones, respectively. The regioselectivity of the addition is dependent on the solvent, temperature, substituent at the nitrogen, and the type or organometallic reactant used, and allows tailoring of both systems. A simple conversion of 6-substituted β,γ-unsaturated δ-thiolactams into their α,β-unsaturated isomers makes the above processes a highly versatile synthetic methodology to access 6-substituted 5,6-dihydropyridine-2-thiones—valuable Michael acceptors.

High-Speed Optimization of Inhibitors of the Malarial Proteases Plasmepsin I and II

Four focused libraries targeted for inhibition of the malarial proteases plasmepsin I and II were designed, synthesized, purified, and screened. Selected carboxylic acids and organometallic reactants with diverse physical properties were attached to the hydroxylethylamine scaffold in the P3 and P1' positions to furnish inhibitors with highly improved activity. The concept of controlled and sequential microwave heating was employed for rapid library generation. This combinatorial optimization protocol afforded plasmepsin inhibitors not only with K(i) values in the low nanomolar range, but also with high selectivity versus the human protease cathepsin D. With this class of inhibitory agents, modifications of the P1' substituents resulted in the largest impact on the plasmepsin/cathepsin D selectivity.

Different Modes of Reaction of Lithium Phosphides with Cp*M(NO)(X)Cl Complexes of Molybdenum and Tungsten

Treatment of Cp*M(NO)(X)Cl complexes (M = Mo, W; X, = CH2SiMe3, CH2CMe3, NHCMe3, OCMe3, Cl) with lithium phosphides can result in one of three different types of reactions. Some reactions involve the starting material undergoing metathesis of a chloro ligand, and others effect reduction of the organometallic reactant, while a third class results in a scrambling of the ligands of the starting complex. Reactions of Cp*M(NO)(X)Cl with LiPPh2 lead to formation of the respective phosphido-containing complexes Cp*M(NO)(X)(PPh2) [M = W, X = CH2SiMe3 (1), CH2CMe3 (2), NHCMe3 (3), OCMe3 (4); M = Mo, X = NHCMe3 (5)]. In contrast, treatment of the molybdenum complexes Cp*Mo(NO)(X)Cl (X = CH2SiMe3, CH2CMe3, OCMe3) with LiPPh2 under identical conditions affords no isolable products. When metathesis of the chloro ligands in the Cp*M(NO)Cl2 complexes of Mo and W is attempted with either LiPPh2 or LiPPhH, the only isolable products formed are those resulting from the reduction of the organometallic reactant. Thus, treatm...

Equilibrium gas phase species for MOCVD of Al xGa 1− xAs

Thermochemical properties have been estimated for plausible gas phase intermediates in metalorganic chemical vapor deposition (MOCVD) of Al x Ga 1− x As. These values have been used in thermodynamic calculations to assess the relative stability of the species for a wide range of operating conditions. The results indicate that polymers and adducts containing Ga and As are unimportant in the gas phase. The most stable intermediates for gallium are GaCH 3 and GaH 2 and, for aluminum, are AlH 3, AlCH 3, and AlH 2. Equilibrium gas phase compositions are presented for different carrier gases and organometallic reactants.

ChemInform Abstract: MONO‐ AND BIMETALLIC CATIONIC DINITROSYLMOLYBDENUM COMPLEXES

AbstractMo‐hexacarbonyl (II) reagiert mit NOPF6 in Methylenchlorid unter verschiedenen experimentellen, wasserfreien Bedingungen stets zum vermutlich polymeren cis‐[)initrosylbis‐[phosphatol‐Mo (I), aber in Nitromethan zum kationischen Komplex (IIIa) (X: PFÖ): Die analogen als Tetrafluoroborate isolierten Solvat‐Komplexe (IIIa) (X: BF4) und (IIIb) sind aus Dichlorodinitrosyl‐Mo (IV) wie aufgezeichnet erhältlich.

Reactions of sulfinyl carbanions with organometallic compounds: Preparation of (η 5-C 5H 5) 2T [formula omitted]6H 4

Sulfinyl carbanions, [RS(O)CHR′] −Li + (R = Ph, Me; R′ = H, Ph) have been observed to have often low reactivity towards neutral transition metal organometallic systems. When reactions do occur they usually involve salt eliminations and formation of complex mixtures containing inter alia organic sulfides, disulfides, freed ligands or their oxides and reduced forms of the organometallic reactants. From the sulfinyl ylide [PhS(O)CH 2]Li, exo-[η 5-C 6H 6CH 2S(O)Ph]Mn(CO) 3 and the new metallocyclic compound (η 5-C 5H 5) 2TiCH 2SC 6H 4 have been prepared, some properties of the latter examined and its sulfonium derivative [(η 5-C 5H 5) 2 TiCH 2S(Me)C 6 H 4]BF 4 isolated.

An unusual oxidative addition-ligand elimination reaction. Preparation and structure of RhCl2(PMe2Ph)2(C3Ph3)

The sym-triphenylcyclopropenium cation (C3Ph3+) stabilized as the Cl− or PF6− salt, undergoes facile reactions at room temperature with trans-Rh(CO)Cl(PMe2Ph)2 to produce complexes which result from the oxidative cleavage of the ring and decarbonylation of the organometallic reactant. The product of the C3Ph3+Cl− reaction has been fully characterized by X-ray analysis and is shown to be RhCl2(PMe2Ph)2(C3Ph3).

Synthesis of poly‐O‐acyl‐amideoximes containing group IV A metals from poly(acrylonitrile)

AbstractPoly(acrylonitrile) was modified to give products of the form below via reaction with hydroxylamine and subsequently with group IV organometallic reactants: magnified image The products obtained with Cl2MR2 are crosslinked. Properties of the new polymers are briefly characterized.