Clarifying notes on the bonding analysis adopted by the energy decomposition analysis.

We discuss the fundamental aspects of the EDA-NOCV method and address some critical comments that have been made recently. The EDA-NOCV method unlike most other methods focuses on the process of bond formation between the interacting species and not just only on the analysis of the finally formed bond. This is demonstrated using LiF as an example. There is a difference between the interactions between the initial species which form the bond and are also the final product of bond cleavage, and the interactions between the fragments in the eventually formed molecule. The flexibility of the method allows the choice of the interacting fragments which helps to identify the charge and electron configuration of the fragments which describe the bond. This is very helpful in cases where the bond may be described with several Lewis structures. We reject the idea that it would be a disadvantage to have "bond path functions" as the energy components in the EDA, which actually indicate the variability of the method. The bonding analysis in a different sequence of the bond formation gives important results for the various questions that can be asked. This is demonstrated by using CH2, CO2 and the formation of a guanine quartet as examples. The fact that a bond is always defined by the bound molecule, the fragments, and their states is universal and deeply physical, as we show here again for various examples. The results of the EDA-NOCV method are in full accordance with the physical mechanism of the chemical bond as revealed by Ruedenberg.

Exploring the conformational space of cobalt(III)-salen catalyst for CO2 /epoxide copolymerization: Effect of quaternary ammonium salts on preference of alternative isomers.

Model catalysts for CO2 /epoxide copolymerization based on Co(III) complexes were studied, with focus on the preference of their alternative isomers, cisß vs. trans. The systems range from model structures without the co-catalyst, as derived from crystallographic data, to complex models with two (CH2 )4 N+ R3 co-catalyst chains (R = Me, Bu) grafted onto a Co(III)-salcy core. To explore the conformational space of the latter complexes, a computational protocol was developed, combining a systematic model-building approach with static and molecular dynamics calculations, and multilevel energy assessment (PM7 and DFT). Results demonstrate an influence of the co-catalyst on the relative stability of the isomers. The cisß isomer is preferred for complexes without N+ -chains and the cisß â†” trans isomerization is feasible. Five-coordinate species and open-shell electronic configurations are energetically disfavored. The cisß preference decreases with the introduction and enlargement of (CH2 )4 N+ R3 : both isomers can be populated for R = Me, while the trans isomer is visibly preferred for R = Bu. © 2018 Wiley Periodicals, Inc.

ETS-NOCV Decomposition of the Reaction Force: The HCN/CNH Isomerization Reaction Assisted by Water.

The partitioning of the reaction force based on the extended-transition-state natural orbital for chemical valence (ETS-NOCV) scheme has been proposed. This approach, together with the analysis of reaction electronic flux (REF), has been applied in a description of the changes in the electronic structure along the IRC pathway for the HCN/CNH isomerization reaction assisted by water. Two complementary ways of partitioning the system into molecular fragments have been considered ("reactant perspective" and "product perspective"). The results show that the ETS-NOCV picture is fully consistent with REF and bond-order changes. In addition, proposed ETS-NOCV decomposition of the reaction force allows for the quantitative assessment of the influence of the observed bond-breaking and bond-formation processes, providing detailed information about the reaction-driving and reaction-retarding force components within the assumed partitioning scheme. © 2017 Wiley Periodicals, Inc.

The influence of the metal cations and microhydration on the reaction trajectory of the N3 ↔ O2 thymine proton transfer: Quantum mechanical study.

This study involves the intramolecular proton transfer (PT) process on a thymine nucleobase between N3 and O2 atoms. We explore a mechanism for the PT assisted by hexacoordinated divalent metals cations, namely Mg2+ , Zn2+ , and Hg2+ . Our results point out that this reaction corresponds to a two-stage process. The first involves the PT from one of the aqua ligands toward O2. The implications of this stage are the formation of a hydroxo anion bound to the metal center and a positively charged thymine. To proceed to the second stage, a structural change is needed to allow the negatively charged hydroxo ligand to abstract the N3 proton, which represents the final product of the PT reaction. In the presence of the selected hexaaqua cations, the activation barrier is at most 8 kcal/mol. © 2017 Wiley Periodicals, Inc.

Nature of the water/aromatic parallel alignment interactions.

The water/aromatic parallel alignment interactions are interactions where the water molecule or one of its O-H bonds is parallel to the aromatic ring plane. The calculated energies of the interactions are significant, up to ΔE(CCSD)(T)(limit) = -2.45 kcal mol(-1) at large horizontal displacement, out of benzene ring and CH bond region. These interactions are stronger than CH···O water/benzene interactions, but weaker than OH···π interactions. To investigate the nature of water/aromatic parallel alignment interactions, energy decomposition methods, symmetry-adapted perturbation theory, and extended transition state-natural orbitals for chemical valence (NOCV), were used. The calculations have shown that, for the complexes at large horizontal displacements, major contribution to interaction energy comes from electrostatic interactions between monomers, and for the complexes at small horizontal displacements, dispersion interactions are dominant binding force. The NOCV-based analysis has shown that in structures with strong interaction energies charge transfer of the type π → σ*(O-H) between the monomers also exists.

Application of 2-substituted benzyl groups in stereoselective glycosylation.

The use of 2-O-(2-nitrobenzyl) and 2-O-(2-cyanobenzyl) groups controls stereoselective formation of 1,2-trans-glycosidic linkages via the arming participation effect. The observed stereoselectivity likely arises from the intramolecular formation of cyclic intermediate between the electron-rich substituent and the donor oxacarbenium ion providing the expected facial selectivity for attack of the glycoside acceptor. The stereodirecting effect of the 2-nitro- and 2-cyanobenzyl groups attached at the remote position (C-3, C-4, and C-6) of the donor molecule have also been investigated. To prove the postulated mechanism based on the participation effect of 2-substituted benzyl groups in the glycosylation stereoselectivity we used DFT theoretical calculation methodology.

Analysis of the bonding between two M(µ-NAr(#)) monomers in the dimeric metal(II) imido complexes {M(µ-NAr(#))}2 [M = Si, Ge, Sn, Pb; Ar(#) = C6H3-2,6-(C6H2-2,4,6-R3)2]. The stabilizing role played by R = Me and iPr.

The nature of the bonding between the two M(µ-NAr(#)) imido monomers [M = Si, Ge, Sn, Pb; Ar(#) = C6H3-2,6-(C6H2-2,4,6-R3)2; R = Me, iPr] in the {M(µ-NAr(#))}2 dimer is investigated with the help of a newly developed energy and density decomposition scheme as well as molecular dynamics. The approach combines the extended transition state energy decomposition method with the natural orbitals for chemical valence density decomposition scheme within the same theoretical framework. The dimers are kept together by two σ bonds and two π bonds. The σ bonding has two major contributions. The first is a dative transfer of charge from nitrogen to M. It amounts to -188 kcal/mol for {Si(µ-NAr(#))}2, -152 kcal/mol for {Ge(µ-NAr(#))}2 with -105 kcal/mol for {Sn(µ-NAr(#))}2, and -79 kcal/mol for {Pb(µ-NAr(#))}2. The second is a charge buildup within the ring made up of the two dimers. It amounts to -82 kcal/mol for M = Si with -61 kcal/mol for M = Ge and ∼-50 kcal/mol for M = Sn and Pb. We finally have π bonding with a donation of charge from M to nitrogen. It has a modest contribution of ∼-30 kcal/mol. The presence of isopropyl (iPr) groups is further shown to stabilize{M(µ-NAr(#))}2 [M = Si, Ge, Sn, Pb; Ar(#) = C6H3-2,6-(C6H2-2,4,6-iPr3)2] compared to the methylated derivatives (R = Me) through attractive van der Waals dispersion interactions.

Multiple boron-boron bonds in neutral molecules: an insight from the extended transition state method and the natural orbitals for chemical valence scheme.

We have analyzed the character of B═B and B≡B bonds in the neutral molecules of general form: LHB═BHL (2-L) and LB≡BL (3-L), for various ancillary ligands L attached to the boron center, based on a recently developed method that combines the extended transition state scheme with the theory of natural orbitals for chemical valence (ETS-NOCV). In the case of molecules with the B═B bond, 2-L, we have included L = PMe(3), PF(3), PCl(3), PH(3), C(3)H(4)N(2)═C(NHCH)(2), whereas for molecules containing the B≡B connection, 3-L, the following ligands were considered L = CO, PMe(3), PCl(3), (Me(2)NCH(2)CH(2)O)(2)Ge. The results led us to conclude that use of phosphorus ligands leads to strengthening of the B═B bond by 6.4 kcal/mol (for 2-PMe(3)), by 4.4 (for 2-PF(3)) and by 9.2 (for 2-PH(3)), when compared to a molecule developed on the experimental basis, 2-C(3)H(4)N(2) (ΔE(total) = -118.3 kcal/mol). The ETS scheme has shown that all contributions, that is, (i) orbital interaction ΔE(orb), (ii) Pauli repulsion ΔE(Pauli), and (iii) electrostatic stabilization ΔE(elstat), are important in determining the trend in the B═B bond energies, ΔE(total). ETS-NOCV results revealed that both σ(B═B) and π(B═B) contributions are responsible for the changes in ΔE(orb) values. All considered molecules of the type LB≡BL, 3-L, exhibit a stronger B≡B bond when compared to a double B═B connection in 2-L (|ΔE(total)| is lower by 11.8-42.5 kcal/mol, depending on the molecule). The main reason is a lower Pauli repulsion contribution noted for 3-CO, 3-PMe(3), and 3-PCl(3) molecules. In addition, in the case of 3-PMe(3) and 3-PCl(3), the orbital interaction term is more stabilizing; however, the effect is less pronounced compared to the drop in the Pauli repulsion term. In all of the systems with double and triple boron-boron bonds, the electronic factor (ΔE(orb)) dominates over the electrostatic contribution (ΔE(elstat)). Finally, the strongest B≡B connection was found for 3-Ge [L = (Me(2)NCH(2)CH(2)O)(2)Ge], predominantly as a result of the strongest σ- and π-contributions, despite the highest destabilization originating from the sizable bulkiness of the germanium-containing ligand. The data on energetic stability of multiple boron-boron bonds (relatively high values of bond dissociation energies |ΔE(total)|), suggest that it should be possible to isolate experimentally the novel proposed systems with double B═B bonds, 2-PMe(3), 2-PF(3), 2-PCl(3), and 2-PH(3), and those with triple B≡B connections, 3-PMe(3), 3-Ge, and 3-PCl(3).

On the nature of Ni···Ni interaction in a model dimeric Ni complex.

A new dinuclear complex (NiC(5)H(4)SiMe(2)CHCH(2))(2) (2) was prepared by reacting nickelocene derivative [(C(5)H(4)SiMe(2)CH=CH(2))(2)Ni] (1) with methyllithium (MeLi). Good quality crystals were subjected to a high-resolution X-ray measurement. Subsequent multipole refinement yielded accurate description of electron density distribution. Detailed inspection of experimental electron density in Ni···Ni contact revealed that the nickel atoms are bonded and significant deformation of the metal valence shell is related to different populations of the d-orbitals. The existence of the Ni···Ni bond path explains the lack of unpaired electrons in the complex due to a possible exchange channel.

Spin ground state and magnetic properties of cobalt(II): relativistic DFT calculations guided by EPR measurements of bis(2,4-acetylacetonate)cobalt(II)-based complexes.

The spin ground state of the core ion and structure of the bis(2,4-acetylacetonate)cobalt(II) model complex and its synthetic aqua and ethanol derivatives, Co(acac)(2)L(n), (L = EtOH, H(2)O), were examined by means of density functional theory (DFT) calculations supported by electron paramagnetic resonance (EPR) measurements. Geometry optimizations were carried out for low-spin (doublet) and high-spin (quartet) states. For the Co(acac)(2) complex two possible conformations, a square-planar and a tetrahedral one, were taken into account. For all structures relative energies were calculated with both "pure" and hybrid functionals. The calculated data were complemented with the results of the EPR investigations carried out at liquid helium temperature, allowing for definite assignment of the high-spin state for the Co(acac)(2)(EtOH)(2) complex. However, because of the unresolved spectral features, only effective g-values could be assessed, whereas the zero-field splitting parameters (ZFS) were calculated by means of the spin-orbit mean field (SOMF) relativistic DFT method for which direct spin-spin (SS) and spin-orbit coupling (SOC) contributions were quantified.

Palladium catalysts for dehydrogenation of ammonia borane with preferential B-H activation.

Cationic Pd(II) complexes catalyzed the dehydrogenation of ammonia borane in the most efficient manner with the release of 2.0 equiv of H(2) in less than 60 s at 25 degrees C. Most of the hydrogen atoms were obtained from the boron atom of the ammonia borane. The first step of the dehydrogenation reaction was elaborated using density functional theory calculations.

Sterically less-hindered half-titanocene(IV) phenoxides: ancillary-ligand effect on mono-, bis-, and tris(2-alkyl-/arylphenoxy) titanium(IV) chloride complexes.

A series of mono-, bis-, and tris(phenoxy)-titanium(IV) chlorides of the type [Cp*Ti(2-R-PhO)(n)Cl(3-n)] (n=1-3; Cp*=pentamethylcyclopentadienyl) was prepared, in which R=Me, iPr, tBu, and Ph. The formation of each mono-, bis-, and tris(2-alkyl-/arylphenoxy) series was authenticated by structural studies on representative examples of the phenyl series including [Cp*Ti(2-Ph-PhO)Cl(2)] (1 PhCl2), [Cp*Ti(2-Ph-PhO)(2)Cl] (2 PhCl), and [Cp*Ti(2-Ph-PhO)(3)] (3 Ph). The metal-coordination geometry of each compound is best described as pseudotetrahedral with the Cp* ring and the 2-Ph-PhO and chloride ligands occupying three leg positions in a piano-stool geometry. The mean Ti-O distances, observed with an increasing number of 2-Ph-PhO groups, are 1.784(3), 1.802(4), and 1.799(3) A for 1 PhCl2, 2 PhCl, and 3 Ph, respectively. All four alkyl/aryl series with Me, iPr, tBu, and Ph substituents were tested for ethylene homopolymerization after activation with Ph(3)C(+)[B(C(6)F(5))(4)](-) and modified methyaluminoxane (7% aluminum in isopar E; mMAO-7) at 140 degrees C. The phenyl series showed much higher catalytic activity, which ranged from 43.2 and 65.4 kg (mmol of Ti x h)(-1), than the Me, iPr, and tBu series (19.2 and 36.6 kg (mmol of Ti x h)(-1)). Among the phenyl series, the bis(phenoxide) complex of 2 PhCl showed the highest activity of 65.4 kg (mmol of Ti x h)(-1). Therefore, the catalyst precursors of the phenyl series were examined by treating them with a variety of alkylating reagents, such as trimethylaluminum (TMA), triisobutylaluminum (TIBA), and methylaluminoxane (MAO). In all cases, 2 PhCl produced the most catalytically active alkylated species, [Cp*Ti(2-Ph--PhO)MeCl]. This enhancement was further supported by DFT calculations based on the simplified model with TMA.

Sigma-donor and pi-acceptor properties of phosphorus ligands: an insight from the natural orbitals for chemical valence.

The bonding between phosphorus ligands X = PCl(3), PF(3), P(OCH(3))(3), PH(3), PH(2)CH(3), PH(CH(3))(2), P(CH(3))(3) and the metal-containing fragments [Ni(CO)(3)], [Mo(CO)(5)], and [Fe(CO)(4)] have been studied by Natural Orbitals for Chemical Valence (NOCV). The main attention was paid to estimation of donor (Deltaq(d)) /acceptor (Deltaq(bd)) properties of X on the basis of NOCV's charge criterion. All ligands X are found to be both sigma-donors and pi-acceptors. The best sigma-donor and pi-acceptor ligands are P(CH(3))(3) and PY(3) (Y horizontal line F,Cl), respectively, in both the nickel and molybdenum complexes. The NOCV contributions to deformation density show that the sigma-component corresponds to the donation from the lone electron pair of phosphorus, enhanced further by a transfer from ancillary halogen atoms (in the case of PCl(3) and PF(3)) to a bonding region and to oxygen atoms of carbonyls. The pi-bonding is due to the electron transfer from the metal into the empty orbital of X, mostly exhibiting phosphorus 3p character. It was shown that within the molecular orbital framework, the trend for the donor/acceptor strength of X can be explained by the difference in the orbital energies of the orbitals involved in the donation/back-donation. Regarding the influence of the metal fragment on the donor/acceptor properties of X, it was demonstrated that the relative order of the phosphorus ligands remains in general intact. The only exception is the P(OCH(3))(3) ligand changing its position in molybdenum series compared to the nickel complexes. However, a change in the metal-containing fragment can influence the magnitude of electron transfer. For the set of phosphorus ligands studied here the effect is much less pronounced than for other ligands studied previously.

Theoretical analysis of the resonance assisted hydrogen bond based on the combined extended transition state method and natural orbitals for chemical valence scheme.

We have analyzed hydrogen bonding in a number of species, containing from two to four hydrogen bonds. The examples were chosen in such a way that they would enable us to examine three different hydrogen bonds involving OH-O, NH-O, and NH-N. A common feature of the investigated systems is that they all are expected to exhibit resonance assisted hydrogen bonding (RAHB) in the electronic pi-framework. Our analysis was based on a recently developed method that combines the extended transition state scheme with the theory of natural orbitals for chemical valence (ETS-NOCV). We find that hydrogen bonding is associated with charge rearrangement in both the electronic sigma-framework (Deltarho(sigma)) and the electronic pi-framework (Deltarho(pi)). However the stabilization due to Deltarho(sigma) is four times as important as the stabilization (RAHB) due to Deltarho(pi). Stabilization due to the electrostatic interaction (DeltaE(elstat)) between the two monomers that are brought together to form the hydrogen bonds is also important. However DeltaE(el) cannot alone account for the strength of the hydrogen bonds as it is more than compensated for by the repulsive Pauli repulsion (DeltaE(Pauli)). When N' is part of an aromatic ring, N'H-O and N'H-N bonds are similar in strength to OH-O links involving carboxylic groups. However, NH-O bonds involving amide groups (-NH(2)) are considerably weaker than the OH-O links mentioned above. In systems with different hydrogen bonds, their relative strength is determined collectively in such a way as to optimize the total interaction. This can result in that one of the bonds (OH-O, NH-O, and NH-N) becomes particularly strong or exceptionally weak. Even within the same dimer two X'-HX bonds of the same type can show quite different strength.

Theoretical study on preference of open polymer vs. cyclic products in CO2/epoxide copolymerization with cobalt(III)-salen bifunctional catalysts.

The preference of open chain of growing macromolecule vs. possible cyclic form was examined for the bifunctional cobalt(III)-salen catalyst for the copolymerization of CO2 with epoxides. A variety of possible isomers was considered (resulting from trans/cis-ß salen arrangement, different mutual orientation of quaternary ammonium-chains, and possible binding modes). To explore the conformational space, a combined approach was applied, utilizing semiempirical (PM7) MD and the DFT calculations. The preference of the open and cyclic macromolecules attached to the metal center was compared with the corresponding results for isolated model macromolecules, and the systems built of the macromolecule interacting with the tetra-butyl ammonium cation. Result shows that the cyclic structures are strongly preferred for isolated ions, with relatively low cyclization barriers. In the field of positive point charge, the open structures are strongly preferred. For the ions interacting with tetrabutyl ammonium cation, the cyclic structures are preferred, due to delocalization of the positive charge in the cation. For the complexes involving model and "real" Co(III)-salen catalysts, the open structures are strongly preferred. The possible cyclization by dissociation of alkoxide and its transfer to the neighborhood of quaternary ammonium cation is characterized by high activation barriers. Further, the transfer of alkoxide from the metal center to the cation is less likely than the transfer of carbonate, since the metal-alkoxide bond-energy energy is much stronger than energy of metal-carbonate bonding, as shown by ETS-NOCV results. The conclusions are in qualitative agreement with experimental data showing high selectivity towards copolymer formation in the copolymerization processes catalyzed by bifunctional Co(III) salen-complexes. Graphical abstract.

Theoretical analysis of bonding in N-heterocyclic carbene-rhodium complexes.

The natural orbitals for chemical valence and the Ziegler-Rauk bond energy decomposition analysis were used to describe the donor/acceptor character of the N-heterocyclic carbenes (NHC)-metal bond in two groups of square-planar rhodium(I) complexes: (NHC)RhCl(cod) (1-X; cod = 1,5-cyclooctadiene) and (NHC)RhCl(CO)(2) (2-X), with a group X = H, Cl, NO(2), or CN located on the NHC ligand. The results show that the NHC-metal bond consists of the components originating from donation (sigma symmetry) and back-donation (two contributions of the pi symmetry, out-of-plane and in-plane, accompanied by one sigma-back-bonding component). The charge-flow measures from NOCV indicate that the total back-bonding contribution is of comparable importance to donation. The out-of-plane pi component contributes to ca. 50% of the total back-bonding charge-flow. The energy measures from the Ziegler-Rauk analysis show that the total back-bonding energy corresponds to ca. 40% of the orbital interaction energy. The ligand trans to NHC (CO or cod) strongly affects the back-bonding component; for the complexes 1-X, the back-donation is substantially enhanced compared to 2-X. The back-bonding component increases with an increase in the pi-withdrawing ability of X for both, 1-X and 2-X. However, this effect is relatively small. Back-bonding components of the two bonds involving the metal are strongly coupled; an increase in NHC-Rh leads to a decrease in Rh-olefin/CO(trans). The changes in the back-bonding are too small to be followed by the trends in bond energies, which are finally determined by the electrostatic and Pauli repulsion energy.

Bond orbitals from chemical valence theory.

Two sets of orbitals are derived, directly connected to the Nalewajski-Mrozek valence and bond-multiplicity indices: Localized Orbitals from the Bond-Multiplicity Operator (LOBO) and the Natural Orbitals for Chemical Valence (NOCV). LOBO are defined as the eigenvectors of the bond-multiplicity operator. The expectation value of this operator is the corresponding bond index. Thus, the approach presented here allows for a discussion of localized orbitals and bond multiplicity within one common framework of chemical valence theory. Another set of orbitals discussed in the present work, NOCV, are defined as eigenvectors of the overall chemical valence operator. This set of orbitals can be especially useful for a description of bonding in transition metal complexes, as it allows for separation of the deformation density contributions originating from the ligand --> metal donation and metal --> ligand back-donation.

Bond multiplicity in transition-metal complexes: applications of two-electron valence indices.

In the present study the applicability of the bond multiplicities from the Nalewajski and Mrozek valence indices was demonstrated for a variety of transition metal-based systems. The Nalewajski-Mrozek valence indices and bond multiplicity indices have been implemented in the Amsterdam Density Functional program. Selected examples comprise the carbonyl complexes (selected tetra- and hexacarbonyls, binary monocarbonyls of the first-row transition metals), phosphines, the ligands' trans-influence, as well as multiple metal-ligand and metal-metal bonds. The results show that the calculated bond multiplicity indices correspond well to experimental predictions based on bond lengths and vibrational frequencies for all discussed classes of complexes. Almost perfect linear correlation between the bond indices and vibrational frequencies was observed for carbonyls and the oxo complexes; the calculated bond multiplicity reproduces the accepted order for the trans-influence of different ligands, rationalizes unusually low vibrational freqencies in the [OsO 3N] (-)complex compared to other nitrido complexes, explains the geometrical asymmetry in the MoO 3 solid, and confirms the multiple character of the metal-metal bond in the [Re 2Cl 8] (2-) complex. Thus, the Nalewajski and Mrozek method can be successfully used as a supplementary analysis tool for electronic structure for studies involving transition metal complexes.

ETS-NOCV decomposition of the reaction force for double-proton transfer in formamide-derived systems.

The analysis of the electronic-structure changes along IRC paths for double-proton-transfer reactions in the formamide dimer (R1), formamide-thioformamide system (R2), and the thioformamide dimer (R3) was performed based on the extended-transition-state natural orbitals for chemical valence (ETS-NOCV) partitioning of the reaction force, considering the intra-fragments strain and the inter-fragments interaction terms, and further-the electrostatic, Pauli-repulsion and orbital interaction components, with the latter being decomposed into the NOCV components. Two methods of the system partitioning into the fragments were considered ('reactant perspective'/bond-formation, 'product perspective' / bond-breaking). In agreement with previous studies, the results indicate that the major changes in the electronic structure occur in the transition state region; the bond-breaking processes are, however, initiated already in the reactant region, prior to entering the TS region. The electrostatic contributions were identified as the main factor responsible for the increase in the activation barrier in the order R1 < R2 < R3.

Dehydrogenation of ammonia-borane by cationic Pd(II) and Ni(II) complexes in a nitromethane medium: hydrogen release and spent fuel characterization.

A highly electrophilic cationic Pd(II) complex, [Pd(MeCN)4][BF4]2 (1), brings about the preferential activation of the B-H bond in ammonia-borane (NH3·BH3, AB). At room temperature, the reaction between 1 in CH3NO2 and AB in tetraglyme leads to Pd nanoparticles and formation of spent fuels of the general formula MeNHxBOy as reaction byproducts, while 2 equiv. of H2 is efficiently released per AB equiv. at room temperature within 60 seconds. For a mechanistic understanding of dehydrogenation by 1, the chemical structures of spent fuels were intensely characterized by a series of analyses such as elemental analysis (EA), X-ray photoelectron spectroscopy (XPS), solid state magic-angle-spinning (MAS) NMR spectra ((2)H, (13)C, (15)N, and (11)B), and cross polarization (CP) MAS methods. During AB dehydrogenation, the involvement of MeNO2 in the spent fuels showed that the mechanism of dehydrogenation catalyzed by 1 is different from that found in the previously reported results. This AB dehydrogenation derived from MeNO2 is supported by a subsequent digestion experiment of the AB spent fuel: B(OMe)3 and N-methylhydroxylamine ([Me(OH)N]2CH2), which are formed by the methanolysis of the AB spent fuel (MeNHxBOy), were identified by means of (11)B NMR and single crystal structural analysis, respectively. A similar catalytic behavior was also observed in the AB dehydrogenation catalyzed by a nickel catalyst, [Ni(MeCN)6][BF4]2 (2).