Computational Study of Methane C–H Activation by Diiminopyridine Nitride/Nitridyl Complexes of 3d Transition Metals and Main-Group Elements

Abstract

The C-H bond activation of methane using PDI-M≡N [PDI = 2,6-(PhN═CMe)CHN] (M = V, Mn, Fe, Co, Ni, Al, or P) has been studied via three reaction pathways: [2 + 2] addition, hydrogen atom abstraction (HAA), and direct insertion. The activating ligand is a nitride/nitridyl (N), with diiminopyridine (PDI) as the supporting ligand. Calculations show reasonable C-H activation barriers for Co, Ni, Al, and P PDI nitrides, complexes that favor an HAA pathway. ElectrophilicPDI nitride complexes of the earlier metals with a nucleophilic actor ligand-V, Mn, Fe-follow a [2 + 2] addition pathway for methane activation. Free energy barriers for methyl migration, PDI-M(CH)═NH → PDI-M-N(H)CH, are also interesting in the context of alkane functionalization; discriminating factors in this mechanistic step include the strengths of the σ-bond and metal-actor ligand π-bond that are broken and the electrophilicity of the actor ligand to which methyl migrates.

Computational Study of Methane C–H Activation by Main Group and Mixed Main Group–Transition Metal Complexes

“…Furthermore, among the divalent metals studied, Be complexes also had the lowest calculated reaction free energies with a range of ΔG = −8.8 to +5.7 kcal/mol for the 1,2-addition reaction with methane. It is further notable that these reactions are not inordinately exergonic, which is often computed for more traditional d-block metal–2p element active sites [ 28 ]. Such a thermodynamic situation should facilitate subsequent functionalization and catalyst regeneration steps within a catalytic cycle for alkane functionalization.…”

DFT and TDDFT Study of the Reaction Pathway for Double Intramolecular C–H Activation and Functionalization by Iron, Cobalt, and Nickel–Nitridyl Complexes

“…Computational and experimental studies were performed to outline a possible reaction pathway for this transformation and implicated a transient nickel–nitride intermediate. There is evidence of the formation of iron–nitride complexes with nonpincer supporting ligands in the literature. , Transient nitride–nitridyl intermediatespotentially containing a triple-, double-, or single-bonded terminal nitrogen ligand depending on the metal ion’s d-electron countare relevant for their catalytic properties as electrophilic or nucleophilic reagents and are capable of intramolecular and intermolecular activation of C–H bonds by fostering reactions such as alkyl migration, insertion into alkane C–H bonds, radical rebound, and/or C–C recombination reactions . These properties are, in part, a consequence of a perturbation of its electronic structure, derived from both steric and electronic distortions, from a square planar geometry to a disphenoidal geometry (Figure ).…”

Methane Activation by (n=0, 1, 2; m= 1, 2): Reactivity Parameters, Electronic Properties and Binding Energy Analysis

“…In this way, the major challenge facing the chemical industry is how to activate methane in an economical and clean way, causing less damage to the environment . In this context, several works have been accomplished aiming at more effective catalysts of transition metals that could activate the C−H bond in an efficient and selective way, thus making possible its large‐scale application . The efficiency of the transformation reaction concerning the conversion of methane to methanol and the branching ratio of methanol are significantly based on the transition metals …”