Theoretical and Computational Study of a Complex System Consisting of Transition Metal Element(s): How to Understand and Predict Its Geometry, Bonding Nature, Molecular Property, and Reaction Behavior

Abstract

Complex chemical systems consisting of transition metal element(s) are important and attractive research targets in both experimental chemistry and theoretical chemistry. Transition-metal complexes with carbon dioxide are discussed as one example, in which the coordination geometry, bonding nature, and reactivity are understood well and predicted with the HOMO and the number of d electrons. The spin-multiplicity of inverse sandwich-type dinuclear transition-metal complexes, which have been synthesized recently as a new type of compound, is discussed as another example based on CASPT2 calculations, in which the clear relationship between the spin multiplicity of its ground state and the number of d electrons is presented. Theoretical understanding of various organometallic reactions has been an important endeavor over the last two decades. Insertion reactions of olefin and carbon dioxide into MH and Malkyl bonds and σ-bond activation reactions are discussed with orbital interaction diagrams based on perturbation theory. In particular, detailed discussion of the characteristic features of a new type of oxidative addition to an ML moiety (L = neutral ligand such as alkene and alkyne) and heterolytic σ-bond activation by an MX moiety (X = anionic ligand). It is still a central challenge to elucidate the reaction mechanisms of catalytic reactions by transition metal complexes. The reaction mechanisms and electronic processes of Ru-catalyzed hydrogenation of carbon dioxide, Pt-, Rh-, and Zr-catalyzed hydrosilylations of alkene, Ir-catalyzed borylation of benzene, and the Hiyama cross-coupling reaction are analyzed based on computational results. We wish to present how to understand the mechanism based on the number of d electrons and the energy of d orbitals in discussion. Also, the importance of solvation and crystalline effects in the theoretical study of transition-metal complexes is discussed based on our recent theoretical studies of mixed-valence complex and a single crystal of a Pt(II) complex.

Aromatic C–H σ-Bond Activation by Ni0, Pd0, and Pt0 Alkene Complexes: Concerted Oxidative Addition to Metal vs Ligand-to-Ligand H Transfer Mechanism

“…TS 3/4 -Pt is a transition state typical of a concerted C–H oxidative addition. Similar results are obtained for Pd with a slightly larger Gibbs activation energy, in agreement with a more facile oxidative addition to Pt 0 than to Pd 0 (Figure S1 in the Supporting Information) due to the lower Pd 4d orbital energy in comparison to the Pt 5d. , Thus, the C–H activation mechanism obtained for Ni 0 is unique to this metal. However, these different mechanisms are associated with rather similar Gibbs activation energies (around 30 kcal/mol for Ni 0 and Pt 0 and slightly larger (34 kcal/mol) for Pd 0 ).…”

Reaction Behavior of the NO Molecule on the Surface of an Mn Particle (M = Ru, Rh, Pd, and Ag; n = 13 and 55): Theoretical Study of Its Dependence on Transition-Metal Element

“…However, significant differences are observed in the M–O and M–N bonding interactions at the transition state TS_2/3 and the products ( 3 to 5 ): In TS_2/3 of the reaction on the Ru and Rh clusters, the M–N and M–O bonding interactions are almost completed, while in TS_2/3 of the Pd and Ag reaction systems those bond formations are not observed well. The energy of 4d valence-band top becomes lower following the order Ru > Rh > Pd > Ag, which is fundamental character of the periodic table . Because the high energy 4d band is favorable for formation of the strong M–N and M–O bonds, the Ru and Rh clusters are reactive for NO dissociative adsorption.…”

“…The energy of 4d valence-band top becomes lower following the order Ru > Rh > Pd > Ag, which is fundamental character of the periodic table. 64 Because the high energy 4d band is favorable for formation of the strong M−N and M−O bonds, the Ru and Rh clusters are reactive for NO dissociative adsorption.…”

Reactions of Silanone(silyl)tungsten and -molybdenum Complexes with MesCNO, (Me2SiO)3, MeOH, and H2O: Experimental and Theoretical Studies

“…These changes indicate that the oxidation state of the metal center is increased by +2 in the reaction. This reaction is understood to be oxidative addition to an M–L moiety (L = neutral species) …”