Pd Sandwich Complexes with π-Cyclic Ligands: Theoretical Insight into Stability, Face-Capping Coordination Bond, Trans-Influence, and Backside-Ligand Effect.

Triangle Pd sandwich complexes with two face-capping π-cyclic ligands, [Pd(Cm)(Cn)L] [L = acetonitrile; Cm, Cn = benzene, cycloheptatriene (CHT), cyclooctatetraene (COT), and [2.2]cyclophane (PCP)], are theoretically investigated. The stability increases in the order [Pd(CH)L] ∼ [Pd(CHMe)L] (CHMe = -xylene) < [Pd(COT)L] < < and [Pd(CH)L] ∼ [Pd(CH)(CHMe)L] < [Pd(CH)(PCP)L] < [Pd(CH)(CHT)L] < < [Pd(CHT)(PCP)L] < , where "bold" represents an experimentally isolated complex.

A Multiconfigurational Wave Function Theoretical Study on Electronic Structure and Magnetic Susceptibility of Dilanthanide Single Molecule Magnet.

Single molecule magnets (SMMs) have been a promising material for next-generation high-density information storage and molecular spintronics. N-bridged dilanthanide complexes, {[(MeSi)N]Ln(THF)(μ-η:η-N)(THF)Ln[(MeSi)N]}, exhibit high blocking temperatures and have been one of the promising candidates for future application. Rational understanding should be established between the magnetic properties and electronic structure.

Carbon dioxide adsorption to UiO-66: theoretical analysis of binding energy and NMR properties.

UiO-66 is one of the most valuable metal-organic frameworks because of its excellent adsorption capability for gas molecules and its high stability towards water. Herein we investigated adsorption of carbon dioxide (CO), acetone, and methanol to infinite UiO-66 using DFT calculations on an infinite system under periodic-boundary conditions and post-Hartree-Fock (SCS-MP2 and MP2.5) calculations on cluster models.

Palladium cluster complex [Pd(μ-CH)] (CH = tropylium) with an fcc-close-packed cuboctahedral Pd core and isomers: theoretical insight into ligand-control of the Pd core structure.

One of the challenging targets in today's chemistry is size-, shape- and metal-atom packing-controlled synthesis of nano-scale transition metal cluster complexes because key factors governing these features have been elusive. Here, we present a DFT study on a recently synthesized palladium cluster complex [Pd(μ-CH)] (named Cubo-μ4; CH = tropylium) with an fcc-close-packed cuboctahedral Pd core and possible isomers. The stability decreases in the order Cubo-μ4 > [Pd(μ-CH)(μ-CH)] with an hcp-close-packed anticuboctahedral Pd core (Anti-μ3,4) > [Pd(μ-CH)] with a non-close packed icosahedral Pd core (Ih-μ3) > [Pd(μ-CH)] with an anticuboctahedral Pd core (Anti-μ4) > [Pd(μ-CH)] with a cuboctahedral Pd core (Cubo-μ3).

Soft corrugated channel with synergistic exclusive discrimination gating for CO recognition in gas mixture.

Developing artificial porous systems with high molecular recognition performance is critical but very challenging to achieve selective uptake of a particular component from a mixture of many similar species, regardless of the size and affinity of these competing species. A porous platform that integrates multiple recognition mechanisms working cooperatively for highly efficient guest identification is desired. Here, we designed a flexible porous coordination polymer (PCP) and realised a corrugated channel system that cooperatively responds to only target gas molecules by taking advantage of its stereochemical shape, location of binding sites, and structural softness.

Isolation and Structures of Polyarene Palladium Nanoclusters.

We report that surrounding coordination of neutral six-membered arene rings affords molecularly well-defined organotransition metal nanoclusters. With the use of [2.2]paracyclophane as the face-capping arene ligand, we have isolated two polyarene palladium nanoclusters, one consisting of a hexakis-arene ligand shell and a hexagonal close-packed Pd anticuboctahedron trichloride core, and the other consisting of an octakis-arene ligand shell and a non-close-packed Pd square gyrobicupola dichloride core, both with Pd-Pd direct bonding.

An Iridium/Aluminum Cooperative Strategy for the β-C(sp )-H Borylation of Saturated Cyclic Amines.

Despite the widespread success in the functionalization of C(sp )-H bonds, the deliberate functionalization of C(sp )-H bonds in a highly site- and stereoselective manner remains a longstanding challenge. Herein, we report an iridium/aluminum cooperative catalytic system that enables the β-selective C-H borylation of saturated cyclic amines and lactams. Furthermore, we have accomplished an enantioselective variant using binaphthol-derived chiral aluminum catalysts to forge C-B bonds with high levels of stereocontrol.

Theoretical Study on the Vapochromic Ni(II)-Quinonoid Complex: One-Dimensional Stacking Structure-Based Color Switching.

Vapochromic crystals of Ni(II)-quinonoid complexes were theoretically investigated using density functional theory (DFT) calculations. Kato et al. previously reported that the purple crystals of a four-coordinate Ni(II)-quinonoid complex () exhibited vapochromic characteristics upon exposure to methanol gas, resulting in orange crystals of the six-coordinate methanol-bound complex () [, , 2345-2349].

Theoretical Study of N-H σ-Bond Activation by Nickel(0) Complex: Reaction Mechanism, Electronic Processes, and Prediction of Better Ligand.

N-H σ-bond activation of alkylamine by Ni(PCy) was investigated using density functional theory (DFT) calculations. When simple alkylamine NHMe is a reactant, both concerted oxidative addition in Ni(PCy)(NHMe) and ligand-to-ligand H transfer reaction in Ni(PCy)(CH)(NHMe) are endergonic and need a high activation energy. When NH(Me)(Bs) (Bs = SOPh, a model of tosyl group used in experiments) is a reactant, both reactions are exergonic and occur easily with a much smaller activation energy.

Tunable acetylene sorption by flexible catenated metal-organic frameworks.

The safe storage of flammable gases, such as acetylene, is essential for current industrial purposes. However, the narrow pressure (P) and temperature range required for the industrial use of pure acetylene (100 < P < 200 kPa at 298 K) and its explosive behaviour at higher pressures make its storage and release challenging. Flexible metal-organic frameworks that exhibit a gated adsorption/desorption behaviour-in which guest uptake and release occur above threshold pressures, usually accompanied by framework deformations-have shown promise as storage adsorbents.

Single atom alloys phase separated alloys in Cu, Ag, and Au atoms with Ni(111) and Ni, Pd, and Pt atoms with Cu(111): a theoretical exploration.

A single-atom alloy (SAA) consisting of an abundant metal host and a precious metal guest is a promising catalyst to reduce the cost without a loss of activity. DFT calculations of Ni- and Cu-based alloys X/M(111) (X = Cu, Ag, or Au for M = Ni; X = Ni, Pd, or Pt for M = Cu; = 1-4) reveal that a phase-separated alloy (PSA) is produced by Cu atoms with Ni(111) but an SAA is produced by Au atoms with Ni(111) and Pd and Pt atoms with Cu(111). In the Ni(111)-based Ag alloy and Cu(111)-based Ni alloy, the relative stabilities of the SAA and PSA depend on coverages of Ag on Ni(111) and Ni on Cu(111).

Heterometallic d -d Coupling of Rh(I) and M(0) (M=Pd, Pt) in a Sandwich Framework of π-Conjugated Ligands.

A heterometallic M-M' bond formation is a key to construct atomically precise bimetallic clusters and materials. However, it is sometimes not straightforward to construct a heterometallic M-M' bond through conventional methods including redox condensation. Here, we found that a sandwich framework of π-conjugated unsaturated hydrocarbon ligands provides a unique coordination environment that facilitates unusual coupling of d Rh and d M (M=Pd, Pt).

Theoretical Study of NO Dissociative Adsorption onto 3d Metal Particles M (M = Fe, Co, Ni, and Cu): Relation between the Reactivity and Position of the Metal Element in the Periodic Table.

NO dissociative adsorption onto 3d metal particles M (M = Fe, Co, Ni, and Cu) was investigated theoretically using density functional theory computations. A transition state exists at higher energy in the Cu case but at lower energy in the Fe, Co, and Ni cases than the reactant (sum of M and NO), indicating that Cu is not reactive for NO dissociative adsorption because NO desorption occurs more easily than the N-O bond cleavage in this case, but Fe, Co, and Ni are reactive because NO desorption needs a larger destabilization energy than the N-O bond cleavage. This result agrees with the experimental findings.

Host-Guest Interaction Modulation in Porous Coordination Polymers for Inverse Selective CO /C H Separation.

Controlling gas sorption by simple pore modification is important in molecular recognition and industrial separation processes. In particular, it is challenging to realize the inverse selectivity, which reduces the adsorption of a high-affinity gas and increases the adsorption of a low-affinity gas. Herein, an "opposite action" strategy is demonstrated for boosting CO /C H selectivity in porous coordination polymers (PCPs).

Deacylative Carbon-Carbon Bond Cleavage of Ketone Equivalents: Applications to Radical Carbon-Carbon Bond Formation Reactions.

This article describes the synthetic application of ketone-derived oxaziridines as alkyl radical precursors in copper-catalyzed Carbon-Carbon bond formation reactions. Experimental and computational studies indicate a free radical mechanism, where alkyl radicals are efficiently generated via cleavage of a Carbon-Carbon bond of oxaziridines. Acyclic and unstrained cyclic oxaziridines are applicable to the present radical process, allowing for the generation of various alkyl radicals with good functional group compatibility.

Four-Electron Reduction of Dioxygen on a Metal Surface: Models of Dissociative and Associative Mechanisms in a Homogeneous System.

Two different four-electron reductions of dioxygen (O) on a metal surface are reproduced in homogeneous systems. The reaction of the highly unsaturated (56-electron) tetraruthenium tetrahydride complex with O readily afforded the bis(μ-oxo) complex via a dissociative mechanism that includes large electronic and geometric changes, i.e.

Coordination Flexibility of the Rh(PXP) Complex to NH, CO, and CH (PXP = Diphosphine-Based Pincer Ligand; X = B, Al, and Ga): Theoretical Insight.

The recently synthesized rhodium-aluminum bimetallic complex Rh(PAlP) (PAlP = pincer-type diphosphino-aluminyl ligand Al{[N(CH)]NMe}[CHP(Pr)]) containing a unique Rh-Al direct bond exhibits coordination flexibility because Rh and Al can play the role of coordination site for the substrate. DFT calculations of NH, CO, and CH adducts with show that the Rh atom is favorable for all these substrate but the Al atom is as favorable as the Rh atom for NH and unfavorable for CO and CH. NH and CO prefer the coordination at the Rh-axial (Ax) site to the Rh-equatorial (Eq) site, but CH prefers coordination at the Rh-Eq site to the Rh-Ax site.

O activation by core-shell Ru@Pt particles in comparison with Pt particles: a DFT study.

The reaction of O with a Ru@Pt core-shell particle consisting of a Ru core and a Pt shell was theoretically investigated in comparison with Pt. The O binding energy with Pt is larger than that with Ru@Pt, and O-O bond cleavage occurs more easily with a smaller activation barrier ( ) on Pt than on Ru@Pt. Protonation to the Pt surface followed by one-electron reduction leads to the formation of an H atom on the surface with considerable exothermicity.

Methane Borylation Catalyzed by Ru, Rh, and Ir Complexes in Comparison with Cyclohexane Borylation: Theoretical Understanding and Prediction.

Methane borylation catalyzed by Cp*M(Bpin) (M = Ru or Rh; HBpin = pinacolborane; = 2 or 3) and (TMPhen)Ir(Bpin) (TMPhen = 3,4,7,8-tetramethyl-1,10-phenanthroline) was investigated by DFT in comparison with cyclohexane borylation. Because Ru-catalyzed borylation has not been theoretically investigated yet, its reaction mechanism was first elucidated; Cp*Ru(Bpin) is an active species, and Cp*Ru(Bpin)(H)(CH) is a key intermediate. In , the Ru is understood to have an ambiguous oxidation state between +IV and +VI because it has a H··Bpin bonding interaction with a bond order of about 0.

Fluorosilane Activation by Pd/Ni→Si-F→Lewis Acid Interaction: An Entry to Catalytic Sila-Negishi Coupling.

A new mode of bond activation involving M→Z interactions is disclosed. Coordination to transition metals as σ-acceptor ligands was found to enable the activation of fluorosilanes, opening the way to the first transition-metal-catalyzed Si-F bond activation. Using phosphines as directing groups, sila-Negishi couplings were developed by combining Pd and Ni complexes with external Lewis acids such as MgBr.

Control of local flexibility towards p-xylene sieving in Hofmann-type porous coordination polymers.

Adsorption-based xylene isomer separation is more energy efficient than conventional processes. Herein, three isostructural Hofmann-type porous coordination polymers (PCPs), {M(Pz)[Ni(CN)4]n} (M = Fe, FePzNi, Co, CoPzNi, and Ni, NiPzNi; Pz = pyrazine) were synthesized and shown to exhibit coordination-dependent lability for the selectivity toward p-xylene over m- and o-xylene.

Magnesiation of Aryl Fluorides Catalyzed by a Rhodium-Aluminum Complex.

We report the magnesiation of aryl fluorides catalyzed by an Al-Rh heterobimetallic complex. We show that the complex is highly reactive to cleave the C-F bonds across the polarized Al-Rh bond under mild conditions. The reaction allows the use of an easy-to-handle magnesium powder to generate a range of arylmagnesium reagents from aryl fluorides, which are conventionally inert to such metalation compared with other aryl halides.

Counterion Dependence of Dinitrogen Activation and Functionalization by a Diniobium Hydride Anion.

We report the synthesis of anionic diniobium hydride complexes with a series of alkali metal cations (Li , Na , and K ) and the counterion dependence of their reactivity with N . Exposure of these complexes to N initially produces the corresponding side-on end-on N complexes, the fate of which depends on the nature of countercations. The lithium derivative undergoes stepwise migratory insertion of the hydride ligands onto the aryloxide units, yielding the end-on bridging N complex.

Structural-Deformation-Energy-Modulation Strategy in a Soft Porous Coordination Polymer with an Interpenetrated Framework.

To achieve unique molecular-recognition patterns, a rational control of the flexibility of porous coordination polymers (PCPs) is highly sought, but it remains elusive. From a thermodynamic perspective, the competitive relationship between the structural deformation energy (E ) of soft PCPs and the guest interaction is key for selective a guest-triggered structural-transformation behavior. Therefore, it is vital to investigate and control E to regulate this competition for flexibility control.

Propene oxidation catalysis and electronic structure of M particles (M = Pd or Rh): differences and similarities between Pd and Rh.

Propene oxidation is one of the important reactions that occurs in the presence of a three-way catalyst but its reaction mechanism is unclear. The reaction mechanisms and differences in catalysis between Pd and Rh particles were investigated by DFT calculations employing Pd and Rh as the model catalysts. The O-attack mechanism, in which the O atom adsorbed on the Pd and Rh surfaces attacks the C[double bond, length as m-dash]C double bond of propene, needs to overcome a large activation barrier (E).