Theoretical investigation of the structure and nature of the interaction in metal–alkane σ-complexes of the type [M(CO)5(C2H6)] (M = Cr, Mo, and W)

Silva, Júlio C. S. Da; Almeida, Wagner B. De; Rocha, Willian R.

doi:10.1016/j.chemphys.2009.10.008

Cited by 13 publications

(8 citation statements)

References 56 publications

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“…(3) an analog of the first model system in which BH 2 Cl is substituted by CH 2 Cl 2 . The formation of such complexes was proposed in the literature 70,79 and was reported with Li as a metallic center, 80 but not, to our knowledge, in the case of transition metal complexes. On the other hand, cases in which the three hydrogen atoms of a CH 3 -R group are simultaneously involved in agostic bonding with a same metallic center, were reported or proposed in the literature.…”

Section: Characterization Of Double R-bh 2 and R-ch 2 Interactions With A Metallic Centermentioning

confidence: 67%

Activation of C–H and B–H bonds through agostic bonding: an ELF/QTAIM insight

Zins

Silvi

Alikhani

2015

Phys. Chem. Chem. Phys.

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Agostic bonding is of paramount importance in C-H bond activation processes. The reactivity of the σ C-H bond thus activated will depend on the nature of the metallic center, the nature of the ligand involved in the interaction and co-ligands, as well as on geometric parameters. Because of their importance in organometallic chemistry, a qualitative classification of agostic bonding could be very much helpful. Herein we propose descriptors of the agostic character of bonding based on the electron localization function (ELF) and Quantum Theory of Atoms in Molecules (QTAIM) topological analysis. A set of 31 metallic complexes taken, or derived, from the literature was chosen to illustrate our methodology. First, some criteria should prove that an interaction between a metallic center and a σ X-H bond can indeed be described as "agostic" bonding. Then, the contribution of the metallic center in the protonated agostic basin, in the ELF topological description, may be used to evaluate the agostic character of bonding. A σ X-H bond is in agostic interaction with a metal center when the protonated X-H basin is a trisynaptic basin with a metal contribution strictly larger than the numerical uncertainty, i.e. 0.01 e. In addition, it was shown that the weakening of the electron density at the X-Hagostic bond critical point with respect to that of X-Hfree well correlates with the lengthening of the agostic X-H bond distance as well as with the shift of the vibrational frequency associated with the νX-H stretching mode. Furthermore, the use of a normalized parameter that takes into account the total population of the protonated basin, allows the comparison of the agostic character of bonding involved in different complexes.

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Section: Characterization Of Double R-bh 2 and R-ch 2 Interactions With A Metallic Centermentioning

confidence: 67%

Activation of C–H and B–H bonds through agostic bonding: an ELF/QTAIM insight

Zins

Silvi

Alikhani

2015

Phys. Chem. Chem. Phys.

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“…From the AIM analysis, we have then located the bond critical points (bcps) in the Nb–C and Nb–H bonding interactions of MP and TS1: i.e., points where the charge density function ( q ( r )) is a minimum along the bond path and a maximum in the other two directions. The reason for this is, as has been shown in the literature, due to the fact that a fairly good linear correlation exists between the charge densities at bcps and the strengths of the linkages. , The AIM parameters of the main computed bcps of the MP and TS1 structures are collected in Table . It is worth noting that these AIM parameters localized at bcps are powerful tools for the characterization of chemical bonds and are also used for the analysis of chemical problems involving bond-breaking and -forming reactions. , In many applications, ρ( r ) has been used as a measure of the strength of the bonding interaction, particularly the σ interaction; ∇ 2 ρ( r ) indicates the regions where ρ( r ) is depleted or concentrated.…”

Section: Resultsmentioning

confidence: 84%

Methane Dehydrogenation by Niobium Ions: A First-Principles Study of the Gas-Phase Catalytic Reactions

et al. 2013

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The issue of reactivity differences of the ions Nb+ and Nb2+ toward methane (CH4 + Nb+ → NbCH2 + + H2 and CH4 + Nb2+ → NbCH2 2+ + H2) is addressed using CCSD(T)//MP2 and CCSD(T)//B3LYP calculations. A thorough description of the reaction mechanisms and analyses of the geometrical structures, chemical bonds, and molecular orbitals provide important insights into the chemistry of the niobium species. The overall results indicate highly labile kinetics and more favorable thermochemical conditions for Nb2+. The NBO, AIM, and FERMO analyses provide a better understanding of the reactivity differences in the niobium reactions.

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“…Metal-alkane σ-complexes are commonly proposed as coordination intermediates, either as a prelude to oxidative addition or as a result of reductive coupling. , For alkanes, because their interaction with metal centers are weak, these intermediates have generally been proposed based on experimental isotope effects, time-resolved IR, , or static density functional theory (DFT) calculations, , and, more recently, X-ray characterization . For methane, Brookhart and co-workers reported that protonation of the (PONOP)Rh−methyl complex ( 1 ) stimulated reductive coupling to the NMR-characterized [(PONOP)Rh(CH 4 )] + σ-complex ( 2 , Figure a). , Static DFT calculations indicate that 2 is ∼8 kcal/mol lower in energy than 1 , and that this σ-complex has an unsymmetrical η 2 -C,H interaction between methane and Rh.…”

Section: Introductionmentioning

confidence: 99%

Paddle Ball Dynamics during Conversion of a Rh–Methyl Hydride Complex to a Rh–Methane σ-Complex through Reductive Coupling

et al. 2019

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We used quasiclassical direct dynamics simulations to examine reaction pathways for protonation-induced reductive coupling of a pincer (PONOP)Rh–methyl hydride complex. These dynamics simulations revealed that the majority of trajectories (>90%) emerging from a vibrationally averaged velocity distribution of the Rh–methyl hydride reductive coupling transition state led to the Rh–methane σ-complex. Only a few trajectories (<10%) dynamically deviated and did not sample this σ-complex structure and resulted in direct methane reductive elimination/dissociation. This indicates that the Rh–methane σ-complex is directly dynamically connected to the Rh–methyl hydride reductive coupling transition state and is not the result of methane rebound due to a solvent cage. Unexpectedly, trajectories that resulted in a Rh–methane σ-complex occurred with paddle ball motion where methane began to leave the Rh coordination sphere but then returned to the σ-complex, and so the distinction between reductive coupling and elimination is blurred. Trajectories also revealed that immediately after reductive coupling, there is relatively fast methane tumbling motion that generally sampled η1-C,H- and η2-C,H-type structures, and this motion is correlated with the paddle ball motion.

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Theoretical investigation of the structure and nature of the interaction in metal–alkane σ-complexes of the type [M(CO)5(C2H6)] (M = Cr, Mo, and W)

Cited by 13 publications

References 56 publications

Activation of C–H and B–H bonds through agostic bonding: an ELF/QTAIM insight

Activation of C–H and B–H bonds through agostic bonding: an ELF/QTAIM insight

Methane Dehydrogenation by Niobium Ions: A First-Principles Study of the Gas-Phase Catalytic Reactions

Paddle Ball Dynamics during Conversion of a Rh–Methyl Hydride Complex to a Rh–Methane σ-Complex through Reductive Coupling

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