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A dense artificial neural network, ESE-ΔH-DNN, with two hidden layers for calculating both solvation free energies ΔG°solv and enthalpies ΔH°solv for neutral solutes in organic solvents is proposed. The input features are generalized-Born-type monatomic and pair electrostatic terms, the molecular volume, and atomic surface areas of the solute, as well as five easily available properties of the solvent. ESE-ΔH-DNN is quite accurate for ΔG°solv, with an RMSE (root mean square error) below 0.6 kcal/mol and an MAE (mean absolute error) well below 0.4 kcal/mol. It performs particularly well for alkane, aromatic, ester, and ketone solvents. ESE-ΔH-DNN also exhibits a fairly good accuracy for ΔH°solv prediction, with an RMSE below 1 kcal/mol and an MAE of about 0.6 kcal/mol. [ABSTRACT FROM AUTHOR]

Oxidation of a base‐stabilized phosphinidene (κ2‐NNP)P (12, NNP=phosphinoamidinate) with N2O afforded a labile phosphinidene oxide (κ2‐NNP)P=O (16) which was characterized by NMR spectroscopy. Further oxidation of 16 by N2O or reaction of 12 with two equivalents of pyridine oxide afforded the isolable dioxide (κ2‐NNP)PO2 which was characterized by NMR and SC XRD. Trapping of 16 with tolyl isocyanate resulted in P=O/N=C metathesis, eventually affording a urea‐ligated phosphine (κ1‐NNP)P(NTol)2C=O (17) The mechanism of this reaction was elucidated by DFT calculations. Reactions of phosphinidene 12 with azides generated transient imines (NNP)P=NR, which in the case of R=Tol underwent cycloaddition with tolyl Isocyanate to afford the urea product 17, and in the case of R=SiMe3 reacts with N3SiMe3 via the addition of N−Si across the P=N bond affording, after the extrusion of dinitrogen, a P,N‐heterocyclic compound. Both products of the reactions with azides have been fully characterized, both in solution and the solid‐state. Finally, reaction of phosphinidene 12 with one equivalent of sulfur resulted in the isolation of the base‐stabilized phosphinidene sulfide (κ2‐NNP)P=S that has also been fully characterized. [ABSTRACT FROM AUTHOR]

ESE‐EE (Easy Solvation Estimation with Electronegativity equalization) is a quick method for estimation of solvation‐free energies ΔGºsolv, which uses a thoroughly fitted electronegativity equalization (EE) scheme to obtain atomic charges, which are further employed in a scaled noniterative COSMO‐like calculation to evaluate the electrostatic component of ΔGºsolv. Nonelectrostatic corrections including adjustable parameters are also added. For neutral solutes, ESE‐EE yields a mean absolute error (MAE) in ΔGsolv° of 1.5 kcal/mol for aqueous solutions; 1.0 kcal/mol for nonaqueous polar protic solvents; 0.9 kcal/mol for polar aprotic solvents; and about 0.6 kcal/mol for nonpolar solvents. Since ESE‐EE only requires a molecular geometry as input for a ΔGºsolv prediction, it can be utilized for a rapid screening of ΔGºsolvfor large neutral molecules. However, for ionic solutes, ESE‐EE yields larger errors (typically several kcal/mol) and is recommendable for preliminary estimations only. Upon a special refitting, ESE‐EE is able to yield partition coefficients with a good accuracy. [ABSTRACT FROM AUTHOR]

Reactions of silicon and germanium dichlorides L⋅ECl2 (E=Si, L=IPr; E=Ge, L=dioxane) with the phosphinoamidinato‐supported disilylene ({κ2(N,P)‐NNP}Si)2 resulted in formal tetrylene insertions into the Si−Si bond. In the case of the reaction with silylene, two products were isolated. The first product ({κ2(N,P)‐NNP}Si)2SiCl2, is the formal product of direct SiCl2 insertion into the Si−Si bond of ({κ2(N,P)‐NNP}Si)2 and thus features two separated silylamido silylene centers. Over time, migration of the SiCl2 group to a lateral position afforded the second product, the disilylene {κ2(Si,P)−SiCl2NNP}Si−Si{κ2(N,P)‐NNP}. In contrast, insertion of GeCl2 resulted only in the isolation of the germanium analogue of {κ2(Si,P)−SiCl2NNP}Si−Si{κ2(N,P)‐NNP}, containing a Ge atom in the central position namely, compound {κ2(Si,P)−SiCl2NNP}Ge−Si{κ2(N,P)‐NNP}, which is a rare example of a silylene‐germylene. Finally, reaction of disilylene ({κ2(N,P)−NNP}Si)2 with SiCl4 and SiHCl3 led to the formation of the new bis(silyl)silylene, ({NNP}SiCl2)2Si:. All four new products from these insertion reactions have been characterized by multinuclear NMR and single‐crystal X‐ray diffraction studies. [ABSTRACT FROM AUTHOR]

We propose an efficient and accurate non‐iterative method, dubbed uESE, for calculating solvation free energies. Apart from a COSMO‐like electrostatic term, the model takes into account non‐electrostatic contributions, which depend on atomic surfaces, induced surface charge densities, and the molecular volume. uESE is tested on 35 polar and 57 non‐polar solvents. The calculated and experimental solvation free energies are compared for 2892 systems. The method exhibits an excellent performance, which is superior to major solvation methods. The mean absolute error of predicted solvation energies is found below 1 kcal/mol for neutral solutes and below 3 kcal/mol for ions. The calculated data are almost independent of the quantum‐chemical method or/and basis sets employed. [ABSTRACT FROM AUTHOR]

We present an efficient method with adjustable parameters for calculating the hydration free energy of molecules and ions using the gas-phase geometry and atomic charges. In most cases, the method yields accurate results, with a mean absolute error for neutral molecules below 1 kcal mol−1 and for ions about 3 kcal mol−1. Overall, despite its simplicity, the proposed method shows the best performance among major computational approaches applied to estimate hydration free energies. The method requires as input Cartesian cordinates and CM5 atomic charges only, which are easily available from any DFT calculation, and yields the hydration energy in a matter of seconds for a medium-size molecule or ion. [ABSTRACT FROM AUTHOR]

In the present paper we discuss and compare two different energy decomposition schemes: Mayer’s Hartree–Fock energy decomposition into diatomic and monoatomic contributions [Chem. Phys. Lett. 382, 265 (2003)], and the Ziegler–Rauk dissociation energy decomposition [Inorg. Chem. 18, 1558 (1979)]. The Ziegler–Rauk scheme is based on a separation of a molecule into fragments, while Mayer’s scheme can be used in the cases where a fragmentation of the system in clearly separable parts is not possible. In the Mayer scheme, the density of a free atom is deformed to give the one-atom Mulliken density that subsequently interacts to give rise to the diatomic interaction energy. We give a detailed analysis of the diatomic energy contributions in the Mayer scheme and a close look onto the one-atom Mulliken densities. The Mulliken density ρA has a single large maximum around the nuclear position of the atom A, but exhibits slightly negative values in the vicinity of neighboring atoms. The main connecting point between both analysis schemes is the electrostatic energy. Both decomposition schemes utilize the same electrostatic energy expression, but differ in how fragment densities are defined. In the Mayer scheme, the electrostatic component originates from the interaction of the Mulliken densities, while in the Ziegler–Rauk scheme, the undisturbed fragment densities interact. The values of the electrostatic energy resulting from the two schemes differ significantly but typically have the same order of magnitude. Both methods are useful and complementary since Mayer’s decomposition focuses on the energy of the finally formed molecule, whereas the Ziegler–Rauk scheme describes the bond formation starting from undeformed fragment densities. [ABSTRACT FROM AUTHOR]

The present work provides a generalization of Mayer’s energy decomposition for the density-functional theory (DFT) case. It is shown that one- and two-atom Hartree–Fock energy components in Mayer’s approach can be represented as an action of a one-atom potential VA on a one-atom density ρA or ρB. To treat the exchange-correlation term in the DFT energy expression in a similar way, the exchange-correlation energy density per electron is expanded into a linear combination of basis functions. Calculations carried out for a number of density functionals demonstrate that the DFT and Hartree–Fock two-atom energies agree to a reasonable extent with each other. The two-atom energies for strong covalent bonds are within the range of typical bond dissociation energies and are therefore a convenient computational tool for assessment of individual bond strength in polyatomic molecules. For nonspecific nonbonding interactions, the two-atom energies are low. They can be either repulsive or slightly attractive, but the DFT results more frequently yield small attractive values compared to the Hartree–Fock case. The hydrogen bond in the water dimer is calculated to be between the strong covalent and nonbonding interactions on the energy scale. [ABSTRACT FROM AUTHOR]

In situ oxidation of the GaI compound NacNacGa by either N2O or pyridine oxide results in the generation of a labile monomeric oxide, NacNacGa(O), which can easily cleave the C−H bonds of aliphatic and aromatic substrates featuring good donor sites. The products of this reaction are gallium organyl hydroxides. DFT calculations show that these reactions start with the formation of NacNac‐Ga(O)(L) adducts, the oxo ligand of which can easily abstract protons from nearby C−H bonds, even for sp2‐hybridized carbon centers. Aliphatic amines do not enter this reaction for kinetic reasons, presumably because of the unfavorable sterics. [ABSTRACT FROM AUTHOR]

A simple, non-iterative method to estimate hydration free energies of neutral molecules, ESE, is developed. It requires only atomic charges computed for isolated species. To obtain the solvation free energy, the COSMO electrostatic term is supplemented by an extra correction that describes the cavitation energy, van der Waals and specific interactions. This term depends on atomic parameters that are adjusted using a reference dataset. Despite its simplicity, the ESE method provides accurate hydration energies with a mean absolute error below 1 kcal mol−1, superseding most accurate existing polarization continuum methods. We show that the proposed scheme can be directly extended to non-aqueous solutions. [ABSTRACT FROM AUTHOR]

We propose an atomic charge partitioning scheme, iterative adjusted charge partitioning (I‐ACP), belonging to the stockholder family and based on partitioning of the valence molecular electron density. The method uses a Slater‐type weighting factor cAr2n–2exp(–αAr), where αA is a fixed parameter and cA is determined iteratively. The parameters αA were fitted for 17 main‐group elements. The I‐ACP scheme is shown to produce consistent, chemically meaningful atomic charges. Several stockholder‐type charge‐partitioning are compared. Extensive numerical tests demonstrate that in most cases, I‐ACP surpasses most other methods by reproducing more accurately molecular dipole moments. © 2018 Wiley Periodicals, Inc. An atomic charge scheme, I‐ACP, is based on partitioning of the valence electron density using a Slater‐type weighting factors cAr2n–2exp(–αAr). I‐ACP produces chemically meaningful atomic charges and accurately reproduces molecular dipole moments. [ABSTRACT FROM AUTHOR]

We propose a new atomic-charge analysis, termed adjusted charge partitioning (ACP) scheme. To partition the molecular electronic density into atomic components, weighting factors cAr2n−2exp(−αAr) with atomic parameters cA and αA are used. Extensive numerical tests were performed for 540 molecules containing 17 main-group elements H, Li to F, Na to Cl, Br, and I. The estimated dipole moments and atomic charges are compared with the data provided by a large number of alternative atomic-charge schemes including the Mulliken, Löwdin, Hirshfeld, Hirshfeld Iterative, CM5, ESP, NPA, and QTAIM population analyses. These tests show that the resulting atomic charges are insensitive to basis sets used, chemically consistent and accurately reproduce experimental dipole moments. [ABSTRACT FROM AUTHOR]

Cover Feature: Base-Stabilized Phosphinidene Oxide, Imide and Sulfide (Chem. Eur. J. 59/2023) Iminophosphorane, phosphinidene, phosphinidene imide, phosphinidene oxide, phosphinidene sulfide Keywords: Iminophosphorane; phosphinidene; phosphinidene imide; phosphinidene oxide; phosphinidene sulfide EN Iminophosphorane phosphinidene phosphinidene imide phosphinidene oxide phosphinidene sulfide 1 1 1 10/26/23 20231023 NES 231023 B Phosphinidene conducts an auction for the best P=X bond b : Cyclic phosphinoamidinate-supported phosphinidene (NP)P is a natural precursor to base-stabilized P SP III sp compounds (NP)P=X (X=O, NR, S). [Extracted from the article]

Reaction of the cyclic guanidine TolN=SIMe with the aluminum(I) compound NacNacAl (1) results in the unprecedented cleavage of the C-N multiple bond to give, after rearrangement, the carbene-ligated Al(III) amide, NacNac'Al(NHTol)(SIMe) (6). DFT calculations revealed that these reactions proceed via a bimolecular mechanism in which either the basic Al(I) center or the transient Al=NTol species deprotonates the methyl group of the NacNac ligand. [ABSTRACT FROM AUTHOR]

We report correlation energies, electron densities, and exchange-correlation potentials obtained from configuration interaction and density functional calculations on spherically confined He, Be, Be2+, and Ne atoms. The variation of the correlation energy with the confinement radius Rc is relatively small for the He, Be2+, and Ne systems. Curiously, the Lee-Yang-Parr (LYP) functional works well for weak confinements but fails completely for small Rc. However, in the neutral beryllium atom the CI correlation energy increases markedly with decreasing Rc. This effect is less pronounced at the density-functional theory level. The LYP functional performs very well for the unconfined Be atom, but fails badly for small Rc. The standard exchange-correlation potentials exhibit significant deviation from the 'exact' potential obtained by inversion of Kohn-Sham equation. The LYP correlation potential behaves erratically at strong confinements. © 2016 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

The treatment of cyclic thioureas with the aluminum(I) compound NacNacAl ( 1; NacNac=[ArNC(Me)CHC(Me)NAr]−, Ar=2,6-Pri2C6H3) resulted in oxidative cleavage of the C=S bond and the formation of 3 and 5, the first monomeric aluminum complexes with an Al=S double bond stabilized by N-heterocyclic carbenes. Compound 1 also reacted with triphenylphosphine sulfide in a similar manner, which resulted in cleavage of the P=S bond and production of the adduct [NacNacAl=S(S=PPh3)] ( 8). The Al=S double bond in 3 can react with phenyl isothiocyanate to furnish the cycloaddition product 9 and zwitterion 10 as a result of coupling between the liberated carbene and PhN=C=S. All novel complexes were characterized by multinuclear NMR spectroscopy, and the structures of 5, 9, and 10 were confirmed by X-ray diffraction analysis. The nature of the Al=S bond in 5 was also probed by DFT calculations. [ABSTRACT FROM AUTHOR]

In this work, local exchange potentials corresponding to the Hartree-Fock (HF) electron density have been obtained using the Zhao-Morrison-Parr method for a number of closed-shell confined atoms and ions. The exchange potentials obtained and the resulting density were compared with those given by the Becke-Johnson (BJ) model potential. It is demonstrated that introducing a scaling factor to the BJ potential allows improving the quality of the resulting density. The optimum scaling factor increases with decreasing confinement radius. The performance of Karasiev and Ludeña's SCα-LDA method as well as of the Becke-88 exchange potential for reproducing the HF electron densities in confined atoms has been also examined. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Various metal complexes catalyze exchange between H2 and hydrosilanes. Catalyst screening suggests that the electron deficiency of the metal center is necessary for exchange, but silane and/or hydrogen addition or σ-bond metathesis with the M-Si and M-H bonds are not required. Kinetic measurements for the system [(ArN=)Mo(PMe3)3(H)(SiH2Ph)/H2/H3SiPh] (Ar = 2,6- iPr2C6H3) suggest that the reaction proceeds through activation of the silane. [ABSTRACT FROM AUTHOR]

A series of bis(silyl)bis(hydride) cobalt complexes [Cp*Co(H)2(SiR3)2] (Cp*=pentamethylcyclopentadienyl; SiR3=SiPh2H, SiMe3, SiH3, SiF3, SiCl3, SiBr3, Si(CF3)3; Co1- Co7) as well as the analogous iridium complexes [Cp*Ir(H)2(SiR3)2] (SiR3=SiEt3, SiMe3, SiH3, SiF3, SiCl3, SiBr3, Si(CF3)3; Ir1- Ir7) were studied to detect possible residual Si⋅⋅⋅H interactions. Tests of several density functionals by comparison with coupled-cluster results indicate that the TPSSh functional performs better than B3LYP, BP86, M06, M06L, and PBEPBE. Based on molecular structures, as well as Wiberg bond indices and J(Si,H) spin-spin coupling constants as indicators of a possible Si⋅⋅⋅H interaction, at least two residual Si⋅⋅⋅H interactions in Co2, Co5, and all four possible Si⋅⋅⋅H interactions in Co3 and Co4 have been detected. Co6 and Co7 exhibit stronger Si⋅⋅⋅H bonding than the other complexes studied. On the contrary, the iridium complexes Ir1- Ir3 and Ir5- Ir7 are classical iridium(V) bis(silyl)bis(hydride) complexes with only rudimentary Si⋅⋅⋅H interactions, if any. [ABSTRACT FROM AUTHOR]

A series of rhodium complexes CpRh(SiMe2X)2(SiMe3)(H) (X = Me, Cl, Br, I), Cp1–Cp4, CpRh(SiMe2X)2(PMe3)(H)+(X = Me, Cl, Br, I), Cp5–Cp8, CpRh(SiMe3)2(SiF3)(H), Cp9, CpRh(SiMe3)2(SiH3)(H), Cp10, TpRh(SiH3)2(SiMe3)(H), Tp1, TpRh(SiH3)2(PMe3)(H)+, Tp2, and TpRh(SiF3)2(PMe3)(H)+, Tp3, were studied computationallyto understand the hydrogen behavior in the Si···H···Simoiety. The hydride ligand interacts with at least one of the silyls,and in many cases with both, but is located asymmetrically with regardto them, giving rise to a double-well potential energy surface (PES)for hydrogen motion. The hydrogen transfer barriers ΔEvary from 0.03 to 3 kcal·mol–1.For selected complexes Tp1, Tp2, Tp3, and Cp9the three-dimensional PESs were constructedand the vibrational Schrödinger equation was solved. The PESis highly anharmonic in all four cases. The hydrogen is delocalizedbetween two silicons in complexes Tp1, Tp3, and Cp9, but localized around the energy minima incomplex Tp2. Complex Tp3is an intermediatecase with a substantial tunneling. The delocalized behavior is pertinentto systems with ΔE< 0.25 kcal·mol–1. For complexes Tp1, Tp2, Tp3, and Cp9the J(Si–H)spin–spin coupling constants were calculated taking into accountthe vibrational motion of hydride. For Tp1, Tp3, and Cp9both J(Si1–H)and J(Si2–H) are negative due tosimultaneous Si1···H···Si2interactions, while for Tp2J(Si2–H) is positive, indicating a single Si···Hinteraction only. Negative J(Si–H) valueswere obtained even for Si···H distances as large as2.3 Å (complex Tp3). A possible effect of vibrationson the J(Si–H) values is also discussed. [ABSTRACT FROM AUTHOR]

The borane B(C6F5)3 is a precatalyst for H/D exchange between H2 and deuterium-labeled silanes (D3SiPh, D2SiMePh, DSiMe2Ph, DSiEt3). Experimental and DFT studies reveal that B(C6F5)3 itself cannot activate dthydrogen but converts to HB(C6F5)2 under the action of hydrosilane. The latter species easily activates H-H and Si-H bonds by a σ-bond metathesis mechanism, which was further confirmed by the reactions of BD3·THF with H2. [ABSTRACT FROM AUTHOR]

When used in conjunction with appropriate extrapolation schemes, full configuration interaction (FCI) calculations employing systematic sequences of spherical Gaussian primitives with even-tempered exponents shared by functions of different angular momenta are capable of affording ground-state energies of the two-electron harmonium atoms with a few-μHartree accuracy that is sufficient for calibration and benchmarking of approximate electron correlation theories of quantum chemistry. The present approach, which is slated for use in future computations of electronic properties of harmonium atoms with between three and five electrons, calls for a series of 15 FCI runs involving basis sets with between four and eight Gaussian primitives of the sp, spd and spdf type. Its applicability is limited by linear dependencies among basis functions that become significant for small (i.e.less than 0.03) values of the force constant. [ABSTRACT FROM AUTHOR]

We have performed a computational study of the C−C coupling reaction between coordinated ethylene and two vinyl ligands in the binuclear bis(vinyl)-ethylene complex CpRu(η2-C2H4)(μ-η1:η2-CHCH2)2RuCp (1) to yield the ruthenacyclopentadiene complex CpRu(η2-C2H4)(CMeCH-CHCMe)RuCp (28), described by Suzuki et al. This reaction is a sophisticated multistep process with a large number of possible pathways. Agostic interactions and the cooperativity of both Ru centers play a crucial role in the mechanism of the reaction. Our calculations provide support for Suzuki et al.’s proposal that the conversion of the reactant 1to the final product 28proceeds through the intermediate Cp(H)Ru(μ-H)(CMeCH-CHCMe)RuCp (20). However, the pathway originally proposed by Suzuki et al. leading to the intermediate 20is unfavorable (Δ⧧G°298= 33 kcal·mol−1). We found a new, more favorable pathway with a Δ⧧G°298of 20 kcal·mol−1. The rate-determining step of the mechanism is ethylene coordination to the intermediate CpRu(μ-H)(CHMeCH-CHCMe)RuCp (22). The free energy barrier is about 29 and 24 kcal·mol−1at the BP86 and MPWLYP1M level, correspondingly. [ABSTRACT FROM AUTHOR]

The present work provides a technique for partitioning the atomization energy of a molecule into diatomic contributions. The method is largely based on the redistribution of the kinetic energy term in Mayer's energy partitioning and uses free-atom energies as a reference. The comparison of Mayer's original method, the alternative Ichikawa–Yoshida approach, and the new atomization energy partitioning (AEP) shows that the new approach has advantages in describing trends in diatomic energies in molecules with triple bonds, as well as for hydrogen bonds. The proposed AEP is a viable alternative to Mayer's energy partitioning method. © 2007 Wiley Periodicals, Inc. Int. J. Quantum Chem, 2008 [ABSTRACT FROM AUTHOR]

The article focuses on cationic silane σ-complexes of ruthenium with relevance to catalysis. It cites the potential of these complexes as intermediates in metal catalyzed transformations of organosilanes. It cites the analysis of the catalytic chemistry of compounds [Cp(R3P)Ru(NCMe)2]+. The compound [Cp(Pri3P)Ru(NCMe)2]+ BAF- are said to have catalyzed various hydrosilylation reactions under mild conditions.

The article discusses the search for a cheaper and environmentally benign alternatives for applications in catalysis as a result of the high price of precious metals and their recognized toxicity. According to the author, the abundant and nontoxic iron is identified as a cheap metal that would serve the purpose like hydrosilation.

Studies the versatile and cooperative reactivity of a triruthenium polyhydride complex. Notion of cooperation between three ruthenium (Ru) centers in a multistep transformation; Mechanism for the complex reaction of ruthenacyclopentadiene formation involving direct assistance by two hydride and three Ru centers.