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Gadolinium doped ceria (GDC) is a promising material for solid oxide cells. GDC is conventionally used as an ionic conductor in composites with electron-conducting metal or perovskite materials. However, recent studies demonstrated that pure GDC fuel electrodes can achieve substantial power density if their microstructure is appropriately designed. Four different types of GDC electrodes are investigated in this study, including conventional Nickel (Ni)-GDC composite, GDC-perovskite composite, GDC deposited with Ni nanoparticles and pure GDC. The test results show a clear correlation between GDC surface area and electrode performance. At the same time, the electrode active thickness depends on the electrode microstructure. It is in the range of 5 µm for the nano-size GDC electrodes. When the GDC electrode is thicker than the active thickness, it results in large ohmic resistance due to the electronic conduction in the outer layer.

Germanium hydride Ph2GeH2 can act as an efficient and reusable hydrogen-production/-storage material with the aid of iron catalysts. Hydrogen evolution from Ph2GeH2 as well as regeneration of Ph2GeH2 was realized at around room temperature.

Treatment of 2,6-dimethyl-1,1′-biphenyl-substituted chlorosilane with potassium followed by FeBr2/TMEDA led to the formation of an iron(II) monobromide complex supported by a TMEDA ligand and a carbanion-based ligand containing a six-membered silacycle-bridged biphenyl skeleton. The obtained complex crystalized as a racemic mixture of (Sa, S) and (Ra, R) forms, in which the dihedral angle of the two phenyl rings of the biphenyl moiety was ~43°.

Supersilyl, -Si(SiMe3)3, serves as an effective ligand to afford a series of four-coordinate manganese(ii) complexes. A dinuclear complex, [(THF)Mn{Si(SiMe3)3}(μ-Br)]2 (2), was readily synthesized by the reaction of MnBr2 with KSi(SiMe3)3. A subsequent ligand exchange of Br in 2 to -OtBu, methyl, or hydride afforded the corresponding manganese(ii) complexes.

The denitrogenative reductive coupling of two molecules of CNtBu was achieved on a multinuclear silylene-bridged Ni cluster framework, and two possible intermediary Ni clusters were isolated.

A disilane that contains two diphenylphosphino moieties, (Ph2PCH2)Ph2Si-SiPh2(CH2PPh), was readily synthesized from the reaction of ClPh2Si-SiPh2Cl with (tmeda)Li(CH2PPh2). Treatment of the thus-obtained disilane with the palladium(0) precursor [Pd(CNtBu)2]3 led to the exclusive formation of a trinuclear palladium cluster in which three palladium atoms are arranged in a triangular fashion. Single-crystal X-ray diffraction analysis of the obtained triangular cluster revealed that novel silylphosphido chelating ligands were formed via a skeletal rearrangement of the ligand framework.

Heptanuclear palladium clusters with six palladium atoms in a planar arrangement were obtained from the reaction of [Pd(CNtBu)2]3 with Ph-substituted cyclotetrasilane or cyclopentasilane via the migration of a phenyl group. The molecular structures of these clusters as well as those of two possible intermediates were determined by single-crystal X-ray diffraction analyses.

Reaction mechanisms of hydrosilylation of ketone and alkene with tertiary silane using the Wilkinson-type catalyst were theoretically investigated on the basis of density functional calculations using ωB97XD functional. Previously proposed three mechanisms, the Chalk-Harrod (CH) mechanism, the modified Chalk-Harrod (mCH) mechanism, and the outer-sphere mechanism were examined. Besides, we also found two mechanisms, the alternative CH (aCH) mechanism and the double hydride (DH) mechanism. In the aCH mechanism, a four-coordinate rhodium hydride complex formed through the elimination of R

Studies on the deactivation mechanism of the reaction of N,N-dialkylamides with TMDS catalyzed by Vaska’s complex, IrCl(CO)(PPh3)2 (1a), triggered the discovery of highly active Ir-PPh3 catalysts: photochemically activated 1a and thermally activated IrCl(PPh3)3 (8). Both catalysts showed excellent activity toward the selective conversion of a variety of N,N-dialkyl-, N-alkyl-N-aryl-, and N,N-diarylamides to the corresponding enamines with low catalyst loadings. The 14-electron species “ClIr(PPh3)2”, which is stabilized by solvents or reactants in the actual catalytic reactions, could be involved in the catalysis, which produces “HIr(PPh3)2” and “SiIr(PPh3)2” (Si = Me2HSiOMe2Si−) species in the catalytic cycle. An in situ generation method for the “ClIrL2” species was established by simply mixing [IrCl(η4-COD)]2 with PPh3 or other phosphorus ligands, which realized the facile large-scale syntheses of enamines.

The activation of the silicon–silicon bond in disilane Ph2Si(μ-PzMe2)2SiPh2 (1), which possesses two five-coordinate silicon centers, was achieved by a reaction with Pd(CNtBu)2 or in situ generated Ni(0)–NHC precursors of modest steric demand.

Palladium-catalyzed reactions of dodecamethylcyclohexasilane [(SiMe2)6] (1) with alkynes led to efficient preparation of 1,1,4,4-tetramethyl-1,4-disilacyclohexadienes (3). The reactions were best catalyzed by Pd(0) species generated from Pd2(dba)3·CHCl3 and 1-isocyanoadamantane (AdNC). Terminal and internal alkynes bearing aryl and alkyl substituents could be used as substrates, and the reaction allowed gram-scale preparation of 3. A dimethylsilylene (Me2Si:) species, generated by activation of Si–Si bonds in 1 by Pd(0) species, was involved in the reaction mechanism. The DFT calculations suggest that oxidative addition of Si–Si bonds in 1 to Pd(CNAd)2 species is followed by extrusion of a Me2Si═Pd(CNAd) intermediate. Reaction of the resulting palladium-coordinated silylene with an alkyne forms a silacyclopropene, which dimerizes to give 3. The extrusion is accompanied by ring contraction of 1 to generate (SiMe2)5, which also contributes to formation of 3 and (SiMe2)4 by the Pd(0)-catalyzed reaction with ...

Suzuki–Miyaura couplings of tertiary-alkyl moieties are accomplished in the presence of a copper catalyst, in which quaternary carbons possessing various functional groups can be synthesized via a radical reaction. Mechanistic studies revealed that 1-alkenylcopperI plays an important role in this coupling reaction. We expect that the radical-organometallic combined process will become one of the best options for the synthesis of quaternary carbons.

A disilaruthenacyclic complex (1) showed extremely high catalytic activity for hydrosilane reduction of aldehydes and ketones to silyl ethers and secondary and tertiary amides to the corresponding amines. An σ-CAM mechanism was proposed to explain the activity.

There are several reports on the synthesis of alkylamines, but most of the reported methods are not suitable for the synthesis of hindered amines. In this research, we found that a copper catalyst is effective for the formation of congested C-N bonds at room temperature. Control experiments revealed that a copper amide is a key intermediate. Moreover, when a chiral amine was used, a quaternary carbon stereogenic center was created with good selectivity.

The hydrogenation of alkenes catalyzed by disilametallacyclic carbonyl complexes of iron, ruthenium or osmium was studied experimentally and theoretically. The disilaruthenacycle 2 with two CO ligands in the trans-configuration was prepared, characterized, and its ability to catalyze hydrogenation was studied. Similar to the corresponding iron analogue 1 in which the CO ligands are in the cis-configuration, 2 contains a H2MSi4 core with Si⋯H⋯Si SISHA (secondary interaction of silicon and hydrogen atoms) and catalyzed the hydrogenation of several alkenes under mild conditions. DFT calculations of 1 and 2 with cis- and trans-CO configurations (cis-1, trans-1, cis-2 and trans-2) revealed that the mechanism of ethylene hydrogenation comprises three catalytic cycles, and a key step involves the H-H bond of H2 being activated by an M-Si bond through oxidative hydrogen migration. These mechanisms are a variety of σ-CAM (σ-complex-assisted metathesis) mechanisms. Further calculations suggest that these catalytic ...

This article discusses two new features of disilametallacyclic chemistry that contribute to the development of efficient catalytic reactions in organic synthesis. The first is disilametallacyclic intermediates in the hydrosilane reduction of carbonyl compounds. Experimental and theoretical studies on disilaplatinacycles suggested that the H2Pt(IV)Si2 species generated by oxidative addition of 1,2-bis(dimethylsilyl)benzene behaves as a highly reactive hydride to reduce amides to amines. This mechanism via disilametallacyclic intermediates explains the efficient hydrosilane reduction of carbonyl compounds with α,ω-bifunctional hydrosilanes catalyzed by other transition metals. The second is hydrogenation of alkenes by disilaferra- or disilaruthenacyclic complexes as catalyst precursors. A new mechanism not involving the conventional oxidative addition of H2 was suggested from DFT calculations, in which activation of the H–H bond occurs in the metal–silicon bond of the disilametallacyclic intermediate. Disilametallacyclic intermediates contribute to efficient catalytic reactions through this σ-CAM (σ-complex assisted mechanism) type mechanism.

A coordinatively unsaturated iron(II)-digermyl complex, Fe[Ge(SiMe3)3]2(THF)2 (1), was synthesized in one step by the reaction of FeBr2 with 2 equiv of KGe(SiMe3)3. Complex 1 shows catalytic activity comparable to that of its silicon analogue in reduction reactions. In addition, 1 acts as an effective precursor for the catalytic dehydrogenation of ammonia borane. Catalytically active species can also be generated in situ by simple mixing of the easy-to-handle precursors FeBr2, Ge(SiMe3)4, KOtBu, and phenanthroline.

An isolable 14-electron iron bis(supersilyl) complex, Fe[Si(SiMe3)3]2(THF)2, was successfully synthesized from the reaction of FeBr2 with K[Si(SiMe3)3] and its structure was unambiguously determined by single-crystal X-ray diffraction analysis. The complex is coordinatively unsaturated and exhibits high catalytic activity toward the hydrosilylation of carbonyl compounds and the reductive silylation of dinitrogen.

The Pt-catalyzed D-glucose oxidation reaction in neutral electrolytes was investigated for implantable power applications. A reaction mechanism involving two possible oxidation pathways, namely direct and OHads-mediated oxidation, was proposed based on the mass change during electrochemical measurement. PtPd and Pt2Pd were synthesized as anodic catalysts by a solvothermal method, and single-chamber glucose-air fuel cells using a neutral aqueous electrolyte were prototyped successfully. Higher fuel cell performance was achieved with the PtPd catalyst, with a maximum power density of 27.6 μW cm−2 and open-circuit voltage of 0.616 V. Collectively, the present study contributes to maximize the performance of glucose fuel cells.

Dinuclear iron carbonyl complex 2, which contains an elongated unsupported Fe–Fe bond, was synthesized by the reaction between Fe2(CO)9 and phosphinyl radical 1. Thermal Fe–Fe bond homolysis led to the generation of a four-coordinate carbonyl-based iron-centered radical, 3, which is stabilized by π-donation. Complex 3 exhibited high reactivity toward organic radicals to form diamagnetic five-coordinate Fe(II) complexes.

This paper theoretically analyzes the throughput of the dynamic multi-hop networks under high traffic load condition. In order to reduce the number of hops and improve the throughput performance, the shortcut path between the non-neighboring nodes is established. However, the preceding packet hinders the establishment of the shortcut path when the traffic load is high. To eliminate the interference from the preceding packet, we introduce intra-flow interference canceller (IFIC). We derive the theoretical packet delivery rate (PDR) expression by taking into account the existence of preceding packets. Theoretical analysis and numerical evaluation elucidate the effectiveness of IFIC to improve the throughput performance in dynamic multi-hop networks even under high traffic load condition.

Disilaferra- and disilaruthenacyclic complexes containing mesityl isocyanide as a ligand, 3′ and 4′, were synthesized and characterized by spectroscopy and crystallography. Both 3′ and 4′ showed excellent catalytic activity for the hydrogenation of alkenes. Compared with iron and ruthenium carbonyl analogues, 1′ and 2′, the isocyanide complexes 3′ and 4′ were more robust under the hydrogenation conditions, and were still active even at higher temperatures (∼80 °C) under high hydrogen pressure (∼20 atm). The iron complex 3′ exhibited the highest catalytic activity toward hydrogenation of mono-, di-, tri-, and tetrasubstituted alkenes among currently reported iron catalysts. Ruthenium complex 4′ catalyzed hydrogenation under very mild conditions, such as room temperature and 1 atm of H2. The remarkably high catalytic activity of 4′ for hydrogenation of unfunctionalized tetrasubstituted alkenes was especially notable, because it was comparable to the activity of iridium complexes reported by Crabtree and Pfa...

Nanosheet compounds Pd11 (SiiPr)2 (SiiPr2 )4 (CNtBu)10 (1) and Pd11 (SiiPr)2 (SiiPr2 )4 (CNMes)10 (2), containing two Pd7 (SiiPr)(SiiPr2 )2 (CNR)4 plates (R=tBu or Mes) connected with three common Pd atoms, were investigated with DFT method. All Pd atoms are somewhat positively charged and the electron density is accumulated between the Pd and Si atoms, indicating that a charge transfer (CT) occurs from the Pd to the Si atoms of the SiMe2 and SiMe groups. Negative regions of the Laplacian of the electron density were found between the Pd and Si atoms. A model of a seven-coordinated Si species, that is, Pd5 (Pd-SiMe), is predicted to be a stable pentagonal bipyramidal molecule. Five Pd atoms in the equatorial plane form bonding overlaps with two 3p orbitals of the Si atom. This is a new type of hypervalency. The Ge analogues have geometry and an electronic structure similar to those of the Si compounds. But their formation energies are smaller than those of the Si analogues. The use of the element Si is crucial to synthesize these nanoplate compounds.

The appropriate design of a ligand (L) in IrCl(CO)(L)2 (4) realized the efficient synthesis of π-conjugated enamines possessing hole-transport properties. The iridium complex with electron-withdrawing phosphorus ligands catalyzed the hydrosilylation of amides to the corresponding silylhemiaminals, which were transformed to the enamines by heat or by treatment with acids. High catalytic efficiency (TON > 10,000) was achieved, which made it possible for the residual iridium in the enamine product to be below 20 ppb.

(COT)2Fe and the open ferrocenes (MPDE)2Fe (MPDE = η5-3-methylpentadienyl) and (DMPDE)2Fe (DMPDE = η5-2,4-dimethylpentadienyl) were found to function as catalyst precursors for the hydrosilylation of alkenes in the presence of auxiliary ligands. Screening trials determined that the optimal catalyst system was composed of (COT)2Fe and adamantyl isocyanide, allowing the selective hydrosilylation of styrene derivatives with trisubstituted hydrosiloxanes and a polydimethylsiloxane bearing Me2SiH moieties as the end groups. Under the appropriate conditions, the dehydrogenative silylation side reaction was completely suppressed, and the reaction TON exceeded 5000.

A platinum-catalyzed amide reduction through hydrosilylation with 1,2-bis(dimethylsilyl) benzene (BDSB) was investigated on a theoretical basis. While the platinum-catalyzed hydrosilylation of alkenes is well known, that of carbonyl groups rarely occurs. The only exception involves the use of bifunctional hydrosilanes having dual, closely located Si-H groups, which accelerate the hydrosilylation of carbonyl groups, leading to successful reduction of amides to amines under mild conditions. In the present study, we determined through density functional theory calculations that the platinum-catalyzed hydrosilylation of the C=O bond proceeds via a Pt(IV)-disilyl-dihydride intermediate with an associated activation energy of 29.6 kcal mol(-1). Although it was believed that the hydrosilylation of carbonyl groups does not occur via the classical Chalk-Harrod cycle, the computational results support a mechanism involving the insertion of the amide CvO bond into a Pt-H bond. This insertion readily occurs because a Pt-H bond in the Pt(IV)-disilyl-dihydride intermediate is highly activated due to the strong s-donating interaction of the silyl groups. The modified Chalk-Harrod mechanism that occurs preferentially in rhodium-catalyzed hydrosilylation as well as the ionic outer sphere mechanism associated with iridium-catalyzed amide reduction were both safely ruled out as mechanisms for this platinum-catalyzed amide reduction, because of the unexpectedly large activation barrier (>40 kcal mol(-1)) for the Si-O bond formation.

Solution-phase synchrotron X-ray absorption spectroscopy (XAS) is a powerful tool for structural and mechanistic investigations of paramagnetic organoiron intermediates in solution-phase reactions. For paramagnetic organotransition metal intermediates, difficulties are often encountered with conventional NMR- and EPR-based analyses. By using solution-phase XAS, we succeeded in identifying the organoiron species formed in the reaction of iron bisphosphine with mesitylmagnesium bromide, MesMgBr, and 1-bromodecane in a [FeX2(SciOPP)]-catalyzed Kumada–Tamao–Corriu (KTC)-type cross-coupling reaction. X-ray absorption near-edge structure (XANES) spectra showed that the resulting aryliron species possessed a divalent oxidation state. Extended X-ray absorption fine structure (EXAFS) demonstrated that the solution-phase molecular geometries of these species are in satisfactory agreement with the crystallographic geometries of [FeIIBrMes(SciOPP)] and [FeIIMes2(SciOPP)]. By combining GC-quantitative analysis and solution-phase XAS, the cross-coupling reactivities of these aryliron species were successfully investigated in the reaction with 1-bromodecane under stoichiometric and catalytic conditions., 放射光施設SPring-8で鉄触媒の作用を直接観察. 京都大学プレスリリース. 2015-03-16.

The planar tetrapalladium cluster Pd4{Si(iPr)2}3(CNtBu)4 (4) was synthesised in 86% isolated yield by the reaction of palladium(0) bis(isocyanide) Pd(CNtBu)2 with octaisopropylcyclotetrasilane (3). In the course of this reaction, the palladium atoms are clustered via insertion into the Si–Si bonds of 3, followed by extrusion of one SiiPr2 moiety and reorganisation to afford 4 with a 54-electron configuration. The CNtBu ligand in 4 was found to be easily replaced by N-heterocyclic carbene (iPr2IMMe) to afford the more coordinatively unsaturated cluster Pd4{Si(iPr)2}3(iPr2IMMe)3 (5) having the planar Pd4Si3 core. On the other hand, the replacement of CNtBu with a sterically compact ligand trimethylolpropane phosphite {P(OCH2)3CEt} led to a planar tripalladium cluster Pd3{Si(iPr)2}3{P(OCH2)3CEt}3 (6) and Pd{P(OCH2)3CEt}4 in 1:1 molar ratio as products.

Well-defined iron complex-mediated catalytic C-3-selective silylation of indole derivatives and stoichiometric C–H bond functionalization of arenes were achieved using an iron dicarbonyl complex containing the disilaferracycle moiety [o-(SiMe2)2C6H4]Fe(CO)2[o-{η2-(H-SiMe2)2}C6H4] (1). Facile liberation of the η2-(H-Si) groups in 1 was the key to effective promotion of these reactions.

Environmentally friendly iron(II) catalysts for atom-transfer radical polymerization (ATRP) were synthesized by careful selection of the nitrogen substituents of N,N,N-trialkylated-1,4,9-triazacyclononane (R3 TACN) ligands. Two types of structures were confirmed by crystallography: "[(R3 TACN)FeX2 ]" complexes with relatively small R groups have ionic and dinuclear structures including a [(R3 TACN)Fe(μ-X)3 Fe(R3 TACN)](+) moiety, whereas those with more bulky R groups are neutral and mononuclear. The twelve [(R3 TACN)FeX2 ]n complexes that were synthesized were subjected to bulk ATRP of styrene, methyl methacrylate (MMA), and butyl acrylate (BA). Among the iron complexes examined, [{(cyclopentyl)3 TACN}FeBr2 ] (4 b) was the best catalyst for the well-controlled ATRP of all three monomers. This species allowed easy catalyst separation and recycling, a lowering of the catalyst concentration needed for the reaction, and the absence of additional reducing reagents. The lowest catalyst loading was accomplished in the ATRP of MMA with 4 b (59 ppm of Fe based on the charged monomer). Catalyst recycling in ATRP with low catalyst loadings was also successful. The ATRP of styrene with 4 b (117 ppm Fe atom) was followed by precipitation from methanol to give polystyrene that contained residual iron below the calculated detection limit (0.28 ppm). Mechanisms that involve equilibria between the multinuclear and mononuclear species were also examined.

Base-stabilized silanone molybdenum complexes were synthesized by the oxygenation of the M=Si bond in the silyl(silylene)molybdenum complex with 1 eq. of PNO in the presence of Lewis base L. The PNO-coordinated silanone complex (L = PNO) was converted to cis-[Cp*(OC)2Mo{OSiMes2(OSiMe3)}(PMe3)] in the presence of excess PMe3.

A series of group 8 half-sandwich disilametallacycles, (η6-arene)MII(Me2SiC6H4SiMe2)L and (η6-arene)MIV(H)2(Me2SiC6H4SiMe2) (M = Fe, Ru) in the formal oxidation states of M(II) and M(IV) were synthesized and characterized. Both the M(II) and the M(IV) oxidation states were effectively stabilized by the disilametallacycle skeleton, and facile interconversion between (η6-arene)MII–dinitrogen, (η6-arene)MII–carbonyl, and (η6-arene)MIV–dihydride complexes bearing a disilaferracycle framework was accomplished. These M(II) and M(IV) complexes can easily generate coordinatively unsaturated 16e disilametallacycles, (η6-arene)MII(Me2SiC6H4SiMe2), by dissociation of L or H2, and stoichiometric and/or catalytic double silylation of alkenes and alkynes was realized thorough this 16e intermediate.

The mechanisms associated with the hydrogenation of alkenes catalyzed by the iron complex Fe(cis-CO)2{o-(SiMe2)2C6H4}2(H)2 (1) were investigated by DFT calculations. The complex 1 has a structure in which the iron center is bonded to four silicon atoms and two hydrides. Secondary Si···H···Si interactions were also observed. The exchange of a 1,2-bis(dimethylsilyl)benzene ligand with ethylene and hydrogen gives a disilaferracycle bearing η2-(CH2═CH2) and η2-H2 ligands. The catalytic cycle initiated from the disilaferracycle involves cleavage of a H–H linkage assisted by an Fe–Si bond to form Fe–H and η1-(H–Si) moieties (step 1), hydrogen migration from the Fe–H group to the η2-(CH2═CH2) ligand which accomplishes the insertion of ethylene into the Fe–H bond (step 2), and reaction of the resulting β-agostic ethyl moiety with the η2-(H–Si) group to form ethane on the iron atom (step 3). The octahedral geometry of 1 as well as the presence of π-acidic CO ligands and Fe–Si σ-bonds contributes to all of the cata...

A mixture of an iron or a cobalt carboxylate and an isocyanide ligand catalyzed the hydrosilylation of alkenes with hydrosiloxanes with high efficiency (TON >10(3)) and high selectivity. The Fe catalyst showed excellent activity for hydrosilylation of styrene derivatives, whereas the Co catalyst was widely effective in reaction of alkenes. Both of them catalyzed the reaction with allylic ethers. Chemical modification and cross-linking of silicones were achieved by choosing the right catalyst and reaction conditions.