Ligand Exchange Reactions in Molecular Hydrogen Complexes of Osmium(II):  A Quantum Chemical Study Using Density Functional Theory

Bytheway, Ian; Bacskay, George B.; Hush, Noel S.

doi:10.1021/jp9608584

Cited by 8 publications

(4 citation statements)

References 26 publications

(51 reference statements)

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“…[26] It has been shown by comparative analysis of transitionmetal hydride complexes that BLYP, B3LYP and B3PW91 give qualitatively similar results. [14,15,28,33] However, as has been shown by Orlova et al, for the special case of intermolecular hydrogen-bonded transition metal complexes, the B3PW91 geometries and bond energies are in better overall agreement with the experimental data. [14,29] Comparison of the proposed mechanisms: Two different catalytic cycles are proposed for hydrogen-transfer reactions.…”

Section: Resultssupporting

confidence: 69%

Chiral Induction Effects in Ruthenium(II) Amino Alcohol Catalysed Asymmetric Transfer Hydrogenation of Ketones: An Experimental and Theoretical Approach

et al. 2000

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The enantioselective outcome of transfer hydrogenation reactions that are catalysed by ruthenium(II) amino alcohol complexes was studied by means of a systematically varied series of ligands. It was found that both the substituent at the 1-position in the 2-amino-1-alcohol ligand and the substituent at the amine functionality influence the enantioselectivity of the reaction to a large extent: enantioselectivities (ee values) of up to 95% were obtained for the reduction of acetophenone. The catalytic cycle of ruthenium(II) amino alcohol catalysed transfer hydrogenation was examined at the density functional theory level. The formation of a hydrogen bond between the carbonyl functionality of the substrate and the amine proton of the ligand, as well as the formation of an intramolecular H...H bond and a planar H-Ru-N-H moiety are crucially important for the reaction mechanism. The enantioselective outcome of the reaction can be illustrated with the aid of molecular modelling by the visualisation of the steric interactions between the ketone and the ligand backbone in the ruthenium(II) catalysts.

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Section: Resultssupporting

confidence: 69%

Chiral Induction Effects in Ruthenium(II) Amino Alcohol Catalysed Asymmetric Transfer Hydrogenation of Ketones: An Experimental and Theoretical Approach

et al. 2000

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“…On the other hand, transition-metal complexes can be computed to good accuracy using density functional theory (DFT) methods and molecular hydrogen complexes of osmium (II) , are generally in good agreement with the available experimental data and second-order Møller−Plesset perturbation (MP2) calculations.…”

Section: Methods Of Calculationmentioning

confidence: 69%

Intermolecular MH···HR Bonding in Monohydride Mo and W Complexes

Orlova

Scheiner

1998

J. Phys. Chem. A

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Intermolecular interactions between HR (R ) F, OH, H 2 O + ) and the hydride and NO ligands of Mo(H)-(CO) 2 (L) 2 (L′) (where cis-ligand L ) PH 3 , NH 3 ; trans-ligand L′ ) NO, Cl, H) and the W(H)(CO) 2 (NO)(PH 3 ) 2 complex have been studied using HF/3-21G and DFT (B3LYP, BLYP, B3PW91) methods. The structure of the complexes depends upon the nature of the trans-ligand and the proton donor ability of HR. H‚‚‚H bonding exists in the case of poor and moderate proton donors HR and the strong π-acceptor trans-ligand. A strong σ-donor cis-ligand strengthens the H‚‚‚H bonding. The change from poor proton donor to strongly acidic HR leads to a η 2 -H 2 structure. The dihydride structure is formed with replacement of a π-acceptor transligand by a σ-donor as a result of greater nucleophilicity of the metal atom. Energy decomposition analysis shows that the H‚‚‚H bond consists of a large electrostatic component, with a small but significant contribution from both charge transfer and polarization, distinct from the pattern of the conventional H-bond wherein polarization makes a more minor contribution. Whereas HF/3-21G predicts a preference for a H‚‚‚O interaction, the DFT approaches favor H‚‚‚H. B3PW91 results are in the best agreement with available experimental data.

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“…The methods and basis sets discussed above were used with a good degree of success in our previous work on platinum catalysts as well as molecular hydrogen complexes of osmium(II). , …”

Section: Methodsmentioning

confidence: 99%

Homogeneous Conversion of Methane to Methanol. 2. Catalytic Activation of Methane by cis- and trans-Platin: A Density Functional Study of the Shilov Type Reaction

2000

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The C-H activation of methane catalyzed by cis-and trans-platin in aqueous solution has been studied by density functional based computational methods. By analogy with the Shilov reaction, the initial step is the replacement of an ammonia ligand by methane, followed by the formation of a methyl complex and the elimination of a proton. The computations utilize the B3LYP hybrid functionals, effective core potentials, and double-ζ to polarized double-ζ basis sets and include solvation effects by a dielectric continuum method. In contrast with the Shilov reaction studied by Siegbahn and Crabtree (J. Am. Chem. Soc. 1996, 118, 4442), in the platins the replacement of an ammonia ligand by methane is found to be effectively rate determining, in that the energy barriers to C-H activation are comparable with those of the initial substitution reaction, viz. ∼ 34 and 44 kcal/mol for cis-and trans-platin, respectively. Several reaction pathways for C-H activation and subsequent proton elimination were identified. For cis-platin the energy barriers associated with the oxidative addition and σ-bond metathesis type mechanisms were found to be comparable, while for trans-platin oxidative addition is predicted to be strongly preferred over σ-bond metathesis, which, interestingly, also proceeds through a Pt(IV) methyl hydrido complex as reaction intermediate. In line with accepted ideas on trans influence, the methyl and hydride ligands in the Pt(IV) complexes that arise in the oxidative addition reactions were always found to be cis to each other. On the basis of the population analyses on the Pt(IV) complexes it is suggested that the Pt-H and Pt-CH 3 bonds are best described as covalent bonds and, further, that the preference of the hydride and methyl anions to be cis to each other is a consequence of such covalent bonding. In light of these findings, the energies of several methyl Pt(IV) hydrido bisulfate complexes were also recalculated, with CH 3 and H placed cis to each other. The revised results provide evidence for the thermodynamic feasibility of oxidative addition of methane to catalysts such as [Pt(NH 3 ) 2 (OSO 3 H) 2 ] or [Pt(NH 3 ) 2 (OSO 3 H)(H 2 SO 4 )] + .

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Ligand Exchange Reactions in Molecular Hydrogen Complexes of Osmium(II): A Quantum Chemical Study Using Density Functional Theory

Cited by 8 publications

References 26 publications

Chiral Induction Effects in Ruthenium(II) Amino Alcohol Catalysed Asymmetric Transfer Hydrogenation of Ketones: An Experimental and Theoretical Approach

Chiral Induction Effects in Ruthenium(II) Amino Alcohol Catalysed Asymmetric Transfer Hydrogenation of Ketones: An Experimental and Theoretical Approach

Intermolecular MH···HR Bonding in Monohydride Mo and W Complexes

Homogeneous Conversion of Methane to Methanol. 2. Catalytic Activation of Methane by cis- and trans-Platin: A Density Functional Study of the Shilov Type Reaction

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