scholarly journals Silver(i), gold(i) and palladium(ii) complexes of a NHC-pincer ligand with an aminotriazine core: a comparison with pyridyl analogues

2016 ◽  
Vol 45 (4) ◽  
pp. 1484-1495 ◽  
Author(s):  
Jamila Vaughan ◽  
Damien J. Carter ◽  
Andrew L. Rohl ◽  
Mark I. Ogden ◽  
Brian W. Skelton ◽  
...  
Keyword(s):  
Pincer Ligands ◽  
Computational Studies ◽  
Pincer Ligand ◽  
Gold Complexes

The twisted vs. linear conformation of newly synthesised silver and gold complexes of chelating C,N,C diethylaminotriazinyl-bridged bis(NHC) pincer ligands have been rationalised by computational studies.

Mechanisms of Electrochemical N2 Splitting by a Molybdenum Pincer Complex

2021 ◽  
Author(s):  
Quinton Bruch ◽  
Santanu Malakar ◽  
Alan Goldman ◽  
Alexander Miller
Keyword(s):  
Electrode Surface ◽  
Redox Reactions ◽  
Catalytic Reduction ◽  
Reaction Pathways ◽  
Bulk Solution ◽  
Mechanistic Study ◽  
Pincer Ligands ◽  
Computational Studies ◽  
Pincer Complex ◽  
Bond Scission

Molybdenum complexes supported by tridentate pincer ligands are exceptional catalysts for dinitrogen fixation using chemical reductants, but little is known about their prospects for electrochemical reduction of dinitrogen. The viability of electrochemical N2 binding and splitting by a molybdenum(III) pincer complex, (pyPNP)MoBr3 (pyPNP = 2,6-bis(tBu2PCH2)-C5H3N)), is established in this work, providing a foundation for a detailed mechanistic study of electrode-driven formation of the nitride complex (pyPNP)Mo(N)Br. Electrochemical kinetic analysis, optical and vibrational spectroelectrochemical monitoring, and computational studies point to two reaction pathways: in the “reaction layer” pathway, the molybdenum(III) precursor is reduced by 2e– and generates a bimetallic molybdenum(I) Mo2(-N2) species capable of N–N bond scission. In the “bulk solution” pathway the precursor is reduced by 3e– at the electrode surface to generate molybdenum(0) species that undergo chemical redox reactions via comproportionation in the bulk solution away from the electrode surface to generate the same bimetallic molybdenum(I) species capable of N2 cleavage. The comproportionation reactions reveal the surprising intermediacy of dimolybdenum(0) complex trans,trans-[(pyPNP)Mo(N2)2](-N2) in N2 splitting pathways. The same “over-reduced” molybdenum(0) species was also found to cleave N2 upon addition of lutidinium, an acid frequently used in catalytic reduction of dinitrogen.

scholarly journals Iron Complexes of a Proton-Responsive SCS Pincer Ligand with Sensitive Electronic Structure

2021 ◽  
Author(s):  
Kazimer Skubi ◽  
Reagan Hooper ◽  
Brandon Mercado ◽  
Melissa Bollmeyer ◽  
Samantha MacMillan ◽  
...  
Keyword(s):  
Strong Field ◽  
Alkali Metal Cation ◽  
Weak Field ◽  
Pincer Ligands ◽  
Zero Field ◽  
Zero Field Splitting ◽  
Pincer Ligand ◽  
Intermediate Spin ◽  
X Ray Absorption ◽  
Phosphine Complex

SCS pincer ligands have an interesting combination of strong-field and weak-field donors that is also present in the nitrogenase active site. Here, we explore the electronic structures of iron(II) and iron(III) complexes with such a pincer ligand, bearing a monodentate phosphine, thiolate S donor, amide N donor, ammonia, or CO. The ligand scaffold features a protonresponsive thioamide site, and the protonation state of the ligand greatly influences the reduction potential of iron in the phosphine complex. The N–H bond dissociation free energy can be quantitated as 56 ± 2 kcal/mol. EPR spectroscopy and SQUID magnetometry measurements show that the iron(III) complexes with S and N as the fourth donors have an intermediate spin (S = 3/2) ground state with large zero field splitting, and X-ray absorption spectra show high Fe–S covalency. The Mössbauer spectrum changes drastically with the position of a nearby alkali metal cation in the iron(III) amido complex, and DFT calculations explain this phenomenon through a change between having the doubly-occupied orbital as dz2 or dyz, as the former is more influenced by the nearby positive charge.

scholarly journals Monomeric alkoxide and alkylcarbonate complexes of nickel and palladium stabilized with the iPrPCP pincer ligand: a model for the catalytic carboxylation of alcohols to alkyl carbonates

2019 ◽  
Vol 48 (4) ◽  
pp. 1351-1366 ◽  
Author(s):  
Luis M. Martínez-Prieto ◽  
Pilar Palma ◽  
Juan Cámpora
Keyword(s):  
Catalytic Synthesis ◽  
Pincer Ligands ◽  
Pincer Ligand ◽  
Organic Carbonates ◽  
Key Steps

Monomeric nickel and palladium alkoxides stabilized with pincer ligands provide a model for the study of key steps in the catalytic synthesis of organic carbonates from alcohols and CO2.

Synthesis, luminescence and electrochemical properties of luminescent dinuclear mixed-valence gold complexes with alkynyl bridges

2015 ◽  
Vol 2 (5) ◽  
pp. 453-466 ◽  
Author(s):  
Ling-Ling Hung ◽  
Wai Han Lam ◽  
Keith Man-Chung Wong ◽  
Eddie Chung-Chin Cheng ◽  
Nianyong Zhu ◽  
...  
Keyword(s):  
Electrochemical Properties ◽  
Photophysical Properties ◽  
Mixed Valence ◽  
Computational Studies ◽  
Gold Complexes

A series of luminescent dinuclear mixed-valence gold alkynyl complexes was synthesized. Their photophysical properties can be tuned by varying the nature of the alkynyl bridges, as supported by computational studies.

Activity-Based Screening of Homogeneous Catalysts through the Rapid Assessment of Theoretically Derived Turnover Frequencies

2019 ◽  
Author(s):  
Matthew Wodrich ◽  
Boodsarin Sawatlon ◽  
Ephrath Solel ◽  
sebastian kozuch ◽  
Clemence Corminboeuf
Keyword(s):  
Free Energy ◽  
Rapid Assessment ◽  
Linear Scaling ◽  
Computational Studies ◽  
Turnover Frequency ◽  
Turnover Number ◽  
Pincer Ligand ◽  
Scaling Relationships ◽  
Energy Profiles ◽  
Hydrogenation Of Co

In homogeneous catalysis, the turnover frequency (TOF) and turnover number (TON) are the most commonly used quantities that experimentally describe catalytic activity. Computational studies, on the other hand, generally yield the ubiquitous free energy profile, which only provides the relative heights of different intermediates and transition states for a given reaction mechanism. This information, however, can be converted into a theoretical TOF through use of the energy span model. Clearly, directly computing turnover frequencies not only allows easy comparison of the activity of different catalysts, but also provides a means of directly comparing theory and experiment. Nonetheless, obtaining detailed free energy profiles for many catalysts is computationally costly. To overcome this and accelerate the rate at which prospective catalysts can be screened, here we use linear scaling relationships in tandem with the energy span model to create volcano plots that relate an easily and quickly computed energetic descriptor variable with a catalyst’s turnover frequency. As a demonstration of their ability, we use these “TOF volcanoes” to rapidly screen prospective transition metal/pincer-ligand catalysts based on activity in facilitating the hydrogenation of CO<sub>2</sub>to formate.

scholarly journals Group 11 Pincer Oxazoline Complexes

2021 ◽  
Author(s):  
Mahroo T. Seighalani
Keyword(s):  
Point Group ◽  
Diffraction Method ◽  
Binding Mode ◽  
Group Symmetry ◽  
Pincer Complexes ◽  
Pincer Ligands ◽  
Henry Reaction ◽  
X Ray Diffraction ◽  
Pincer Ligand ◽  
Nitroaldol Reaction

The synthesis and characterization of new copper pincer complexes via cyclometallation of potentially anionic pincer ligands with C1 point group symmetry is reported. All of these complexes have been characterized by single crystal X-ray diffraction method, which confirms the proposed tridentate binding mode of pincer ligand and the formation of an amido N-Cu bond. The reactivity of two of the complexes was investigated towards C-C bond formation reaction, notably the Henry reaction. One of the complexes, which was derived from the achiral pincer ligand, is shown to be a suitable catalyst for the Henry reaction under the standard conditions. The Henry or nitroaldol reaction is one of the organic reactions which affords a C-C bond. The product of this reaction is a β-nitro alcohol which is formed by addition of a nitroalkane to a carbonyl compound.

Activity-Based Screening of Homogeneous Catalysts through the Rapid Assessment of Theoretically Derived Turnover Frequencies

2019 ◽  
Author(s):  
Matthew Wodrich ◽  
Boodsarin Sawatlon ◽  
Ephrath Solel ◽  
sebastian kozuch ◽  
Clemence Corminboeuf
Keyword(s):  
Free Energy ◽  
Rapid Assessment ◽  
Linear Scaling ◽  
Computational Studies ◽  
Turnover Frequency ◽  
Turnover Number ◽  
Pincer Ligand ◽  
Scaling Relationships ◽  
Energy Profiles ◽  
Hydrogenation Of Co

In homogeneous catalysis, the turnover frequency (TOF) and turnover number (TON) are the most commonly used quantities that experimentally describe catalytic activity. Computational studies, on the other hand, generally yield the ubiquitous free energy profile, which only provides the relative heights of different intermediates and transition states for a given reaction mechanism. This information, however, can be converted into a theoretical TOF through use of the energy span model. Clearly, directly computing turnover frequencies not only allows easy comparison of the activity of different catalysts, but also provides a means of directly comparing theory and experiment. Nonetheless, obtaining detailed free energy profiles for many catalysts is computationally costly. To overcome this and accelerate the rate at which prospective catalysts can be screened, here we use linear scaling relationships in tandem with the energy span model to create volcano plots that relate an easily and quickly computed energetic descriptor variable with a catalyst’s turnover frequency. As a demonstration of their ability, we use these “TOF volcanoes” to rapidly screen prospective transition metal/pincer-ligand catalysts based on activity in facilitating the hydrogenation of CO<sub>2</sub>to formate.

Key factors in pincer ligand design

2018 ◽  
Vol 47 (6) ◽  
pp. 1959-1968 ◽  
Author(s):  
Eduardo Peris ◽  
Robert H. Crabtree
Keyword(s):  
Ligand Design ◽  
Pincer Ligands ◽  
Key Factors ◽  
Pincer Ligand

This tutorial review analyses the reasons of success of pincer ligands.

scholarly journals Ammonia Formation Catalyzed by Dinitrogen-Bridged Dirhenium Complex Bearing PNP-Pincer Ligands under Mild Reaction Conditions

2020 ◽  
Author(s):  
Fanqiang Meng ◽  
Shogo Kuriyama ◽  
Hiromasa Tanaka ◽  
Akihito Egi ◽  
Kazunari Yoshizawa ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Pincer Ligands ◽  
Pincer Ligand ◽  
Reaction Conditions ◽  
Rhenium Atom ◽  
Phosphine Complexes ◽  
Proton Source ◽  
Dinitrogen Complexes ◽  
Dinitrogen Complex ◽  
Ammonia Formation

A series of rhenium complexes bearing a pyridine-based PNP-type pincer ligand are synthesized from rhenium phosphine complexes as precursors. A dinitrogen-bridged dirhenium complex bearing the PNP-type pincer ligands catalytically converts dinitrogen into ammonia in the reaction with KC<sub>8</sub> as a reductant and [HPCy<sub>3</sub>]BAr<sup>F</sup><sub>4</sub> (Cy = cyclohexyl, Ar<sup>F</sup> = 3,5-(CF<sub>3</sub>)<sub>2</sub>C<sub>6</sub>H<sub>3</sub>) as a proton source at –78 °C to afford 8.4 equiv of ammonia based on the rhenium atom of the catalyst. The rhenium-dinitrogen complex also catalyzes silylation of dinitrogen in the reaction with KC<sub>8</sub> as a reductant and Me<sub>3</sub>SiCl as a silylating reagent under ambient reaction conditions to afford 11.3 equiv of tris(trimethylsilyl)amine based on the rhenium atom of the catalyst. These results demonstrate the first successful example of catalytic nitrogen fixation under mild reaction conditions by using rhenium-dinitrogen complexes as catalysts.

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