Functionalization of Carbon Nanotubes with Vaska's Complex: A Theoretical Approach

The functionalization of single-walled carbon nanotubes (CNTs) with Vaska's complex trans-Ir(CO)Br(PPh3)2 has been investigated by means of hybrid quantum mechanics/molecular mechanics (QM/MM) calculations. The formation of a stable adduct has been experimentally evidenced by Wong et al. (Nano Lett. 2002, 2, 49), but microscopical details on the metal−nanotube interaction are still unclear. Our calculations show a low propensity to η2 coordination of Vaska's complex with the perfect hexagonal network of CNTs. Rather, a stronger interaction takes place when the transition metal center coordinates to carbon atoms belonging to pentagonal rings, as in topological defects or end-caps

Functionalization of Carbon Nanotubes with Vaska's Complex: A Theoretical Approach

The functionalization of single-walled carbon nanotubes (CNTs) with Vaska's complex trans-Ir(CO)Br(PPh3)2 has been investigated by means of hybrid quantum mechanics/molecular mechanics (QM/MM) calculations. The formation of a stable adduct has been experimentally evidenced by Wong et al. (Nano Lett. 2002, 2, 49), but microscopical details on the metal−nanotube interaction are still unclear. Our calculations show a low propensity to η2 coordination of Vaska's complex with the perfect hexagonal network of CNTs. Rather, a stronger interaction takes place when the transition metal center coordinates to carbon atoms belonging to pentagonal rings, as in topological defects or end-caps

Functionalization of Carbon Nanotubes with Vaska's Complex: A Theoretical Approach

The functionalization of single-walled carbon nanotubes (CNTs) with Vaska's complex trans-Ir(CO)Br(PPh3)2 has been investigated by means of hybrid quantum mechanics/molecular mechanics (QM/MM) calculations. The formation of a stable adduct has been experimentally evidenced by Wong et al. (Nano Lett. 2002, 2, 49), but microscopical details on the metal−nanotube interaction are still unclear. Our calculations show a low propensity to η2 coordination of Vaska's complex with the perfect hexagonal network of CNTs. Rather, a stronger interaction takes place when the transition metal center coordinates to carbon atoms belonging to pentagonal rings, as in topological defects or end-caps

Functionalization of Carbon Nanotubes with Vaska's Complex: A Theoretical Approach

The functionalization of single-walled carbon nanotubes (CNTs) with Vaska's complex trans-Ir(CO)Br(PPh3)2 has been investigated by means of hybrid quantum mechanics/molecular mechanics (QM/MM) calculations. The formation of a stable adduct has been experimentally evidenced by Wong et al. (Nano Lett. 2002, 2, 49), but microscopical details on the metal−nanotube interaction are still unclear. Our calculations show a low propensity to η2 coordination of Vaska's complex with the perfect hexagonal network of CNTs. Rather, a stronger interaction takes place when the transition metal center coordinates to carbon atoms belonging to pentagonal rings, as in topological defects or end-caps

Functionalization of Carbon Nanotubes with Vaska's Complex: A Theoretical Approach

The functionalization of single-walled carbon nanotubes (CNTs) with Vaska's complex trans-Ir(CO)Br(PPh3)2 has been investigated by means of hybrid quantum mechanics/molecular mechanics (QM/MM) calculations. The formation of a stable adduct has been experimentally evidenced by Wong et al. (Nano Lett. 2002, 2, 49), but microscopical details on the metal−nanotube interaction are still unclear. Our calculations show a low propensity to η2 coordination of Vaska's complex with the perfect hexagonal network of CNTs. Rather, a stronger interaction takes place when the transition metal center coordinates to carbon atoms belonging to pentagonal rings, as in topological defects or end-caps

Functionalization of Carbon Nanotubes with Vaska's Complex: A Theoretical Approach

The functionalization of single-walled carbon nanotubes (CNTs) with Vaska's complex trans-Ir(CO)Br(PPh3)2 has been investigated by means of hybrid quantum mechanics/molecular mechanics (QM/MM) calculations. The formation of a stable adduct has been experimentally evidenced by Wong et al. (Nano Lett. 2002, 2, 49), but microscopical details on the metal−nanotube interaction are still unclear. Our calculations show a low propensity to η2 coordination of Vaska's complex with the perfect hexagonal network of CNTs. Rather, a stronger interaction takes place when the transition metal center coordinates to carbon atoms belonging to pentagonal rings, as in topological defects or end-caps

Density Functional Study of the Dissociative Adsorption of Aromatic Molecules on the Si(100) Surface: On the Way from Benzene to Larger Polycyclic Hydrocarbons

Density functional calculations have been performed on possible mechanisms for the hypothetic C−H bond cleavage process of benzene chemisorbed on the Si(100) surface, in order to shed light on the analogous process on larger polycyclic aromatic hydrocarbons. We first identified the minima on the potential energy surface for the benzene adsorption on Si(100) and for the breaking of two C−H bonds, with formation of two Si−H bonds, and then we analyzed possible pathways for the C−H bond cleavage, looking for the transition states connecting the adsorption configurations to the final products of C−H breaking. We identified two adsorbed configurations of benzene from which the breaking of two C−H bonds can be accessible, i.e., the 1,2 tilted di-σ bonded configuration on top of a single dimer (T) and the 1,4 di-σ bonded configuration where benzene bridges two dimer rows (BR). The kinetically most favorable reactive channel on the T configuration involves the abstraction of two hydrogen atoms on the sp3 carbon atoms by the silicon atoms of an adjacent dimer, with an energy barrier of 22.0 kcal mol-1. Although seemingly low, such an activation energy is not expected to be accessible at temperatures below the onset of benzene desorption from this configuration, which requires 15.9 kcal mol-1. The kinetically most favorable reactive channel on the BR configuration, which has not been experimentally detected for the benzene molecule, involves the rupture of one Si−C bond, passing through an energy barrier of 29.8 kcal mol-1, and ends with the formation of a Si−H bond and a vertical phenyl unit anchored on a silicon dimer

Four- and Five-Coordinate CO Insertion in the Copolymerization of Carbon Monoxide and Olefins Catalyzed by Diphosphine Nickel(II) Complexes: A Dynamical Density Functional Study

We have carried out a theoretical study of the migratory insertion step in the cationic Ni(II) [(dppp)Ni(CH3)(CO)]+ complex by means of both static and dynamic density functional methods to shed light on the mechanistic aspects of the migratory insertion and in particular on the role played by five-coordinate species. We find the addition−insertion pathway, taking place via a five-coordinate complex, to be thermodynamically and kinetically favored, with a highest energy barrier of 7.9 kcal mol-1, in agreement with the experimental data. Dynamics simulations have shown that the migratory insertion reaction takes place by a methyl attack on the resting carbonyl group

Full Quantum Mechanical Investigation of the Unimolecular versus Bimolecular Acetylene to Vinylidene Rearrangement in the Prototype <i>trans</i>-Cl-Rh(P<i>i</i>-Pr₃)₂ Complex

We report a full quantum mechanical investigation, based on DFT calculations, on the unimolecular and bimolecular alkyne−vinylidene rearrangements in the prototype [Cl-Rh(Pi-Pr3)2(HC⋮CH)] complex, to solve the discrepancy between theory and recent experimental data and to provide a definitive answer concerning the largely debated molecularity issue of the 1,3-shift in d8 metal complexes. We calculate the intramolecular pathway to be kinetically favored over the intermolecular one by 15.0 kcal/mol, in agreement with recent crossover experiments. Comparison of our DFT calculations performed on the real systems with reduced models shows that a full quantum mechanical description of the investigated systems is mandatory for a correct description of their reactivity, owing to the relevant role played by the electron-donating phosphine ligands

Full Quantum Mechanical Investigation of the Unimolecular versus Bimolecular Acetylene to Vinylidene Rearrangement in the Prototype <i>trans</i>-Cl-Rh(P<i>i</i>-Pr₃)₂ Complex

We report a full quantum mechanical investigation, based on DFT calculations, on the unimolecular and bimolecular alkyne−vinylidene rearrangements in the prototype [Cl-Rh(Pi-Pr3)2(HC⋮CH)] complex, to solve the discrepancy between theory and recent experimental data and to provide a definitive answer concerning the largely debated molecularity issue of the 1,3-shift in d8 metal complexes. We calculate the intramolecular pathway to be kinetically favored over the intermolecular one by 15.0 kcal/mol, in agreement with recent crossover experiments. Comparison of our DFT calculations performed on the real systems with reduced models shows that a full quantum mechanical description of the investigated systems is mandatory for a correct description of their reactivity, owing to the relevant role played by the electron-donating phosphine ligands