Thermische Aktivierung von Methan durch kationische Nickelkomplexe: Einfluss von Liganden und formaler Oxidationsstufe

Abstract

Verwandt und doch ganz anders. Ob eine thermische Aktivierung von Methan durch kationische Nickelkomplexe stattfindet oder nicht, hängt von der Art des Liganden und der formalen Oxidationsstufe des Metalls ab, wie das Beispiel der isomeren Wasserkomplexe zeigt: Während [Ni(H2O)]+ unreaktiv ist, aktiviert [Ni(H)(OH)]+ eine C‐H‐Bindung im Methan.

Quantum Chemical Study of the Reaction between Ni+ and H2S

“…[5] However, there is one more additional important fact that is worth mentioning. In a recent seminal experiment carried out by Schwarz et al [13] it has been shown that, in the particular case of nickel, the four-centered HNiOH …”

“…[5] However, there is one more additional important fact that is worth mentioning. In a recent seminal experiment carried out by Schwarz et al [13] it has been shown that, in the particular case of nickel, the four-centered HNiOH + nickel hydrido-hydroxy intermediate, which occurs in the reaction of Ni + with water, is able to activate the CÀH bond of methane under thermal conditions. Specifically, Schwarz et al verified experimentally that HNiOH + , the central intermediate of the reaction between Ni + and H 2 O, namely [reaction (1)]:…”

“…These two effects have already been described in the chemical literature. [13,15,[17][18][19][20][21][22][23][24][25][26][27][28] The open-shell ligands modulate the intensity of their effect in accordance with their electronegativity. [15] Thus, for the specific case of Ni + , it has been demonstrated that both NiH + and NiCH 3 + activate the CÀH bond of methane, [21] but their reac- tion paths involve two spin crossings.…”

Mechanism of Redox‐Active Ligand‐Assisted Nitrene‐Group Transfer in a ZrIV Complex: Direct Ligand‐to‐Ligand Charge Transfer Preferred

“…These radicaloid species have previously been shown to engage in remarkable reactivity. [17,24] Intuitively, we expect the d-e-c (Scheme 1)/d-e1-e2c (Scheme 2) pathway to be feasible when: 1) the local redox potentials of the L and R ligands are matched as to make the electron transfer energetically viable; and 2) the structural arrangement of the two ligands L and R in the metal complex allow for a donor-acceptor coupling. The donor orbital on the redox-active supporting ligand L and the acceptor orbital on the substrate R need to overlap either directly or through a metal d orbital for the electron transfer to take place.…”

Quantum Chemical Study of the Reactions between Pd+/Pt+ and H2O/H2S

“…[20] Additionally, quantum chemistry mechanistic studies performed for the early, [21][22][23] middle, [24,25] and late [26] first-row transition metals agreed with the experimental evidence, [20] which showed that whereas for early first-row transition metals their bare cations are more reactive than their oxides, the opposite is the case for the late transition-metal cations. [27] Moreover, in most of these reactions there is at least one spin-crossing, and thus, depending on the spin state of the reactants, the efficiency of the reaction varies drastically. [17,19] The reactions with water are important in themselves because water is ubiquitous in most reaction environments as well as in many man-made devices, as a background impuri-ty and, consequently, it constitutes a likely reactive target for transition metal cations.…”