Computational Ligand Design for the Reductive Elimination of ArCF3from a Small Bite Angle PdIIComplex: Remarkable Effect of a Perfluoroalkyl Phosphine

2014 ◽  
Vol 53 (23) ◽  
pp. 5903-5906 ◽  
Author(s):  
Mads C. Nielsen ◽  
Karl. J. Bonney ◽  
Franziska Schoenebeck
Keyword(s):  
Ligand Design ◽  
Reductive Elimination ◽  
Remarkable Effect ◽  
Bite Angle

The natural bite angle — Seen from a ligand's point of view

2007 ◽  
Vol 85 (3) ◽  
pp. 230-238 ◽  
Author(s):  
Olaf Kühl
Keyword(s):  
Bond Length ◽  
Ligand Design ◽  
Point Of View ◽  
Chelate Complexes ◽  
Ligand Effects ◽  
Bite Angle ◽  
Upper Limit ◽  
Metal Atoms

The natural bite angle concept is examined using N,N′-bisphosphino urea ligands as rigid scaffolds. The ligand has an upper limit of about 95° for the observed bite angle in chelate complexes, but prefers a much lower one. The ligand can be described as possessing downward flexibility. The dependence of the bite angle on the P—P distance within the ligand and the M—P bond length is illustrated. The metal tries to force the ligand into its own preferred structure, whereas the ligand wants to achieve a short P—P distance. A truly rigid ligand such as the N,N′-bisphosphino urea family is thus seen to clearly discriminate between metal atoms according to their individual assertiveness, using the P—P distance in the complex as a measure. Although the natural bite angle concept is valid and helpful in determining the possible bite-angle range for ligands before it is actually synthesised, its practical applicability seems to be limited to those cases where the flexibility range of the ligand allows for only one metal-preferred bite angle to be realized.Key words: natural bite angle, ligand effects, ligand design.

scholarly journals Force-Modulated Reductive Elimination from Platinum(II) Diaryl Complexes

2020 ◽  
Author(s):  
Yichen Yu ◽  
Liqi Wang ◽  
Chenxu Wang ◽  
Yancong Tian ◽  
Roman Boulatov ◽  
...  
Keyword(s):  
Transition Metal ◽  
Transition Metal Complexes ◽  
Free Ligand ◽  
Reductive Elimination ◽  
Mechanical Force ◽  
Mechanical Forces ◽  
Bite Angle ◽  
Restoring Forces ◽  
Rate Behavior ◽  
Ground State Geometry

<div><p>Coupled mechanical forces are known to drive a range of covalent chemical reactions, but the interplay of mechanical force applied to a spectator ligand and transition metal reactivity is relatively unexplored. Here we report the effect of mechanical force on the rate of C(sp<sup>2</sup>)-C(sp<sup>2</sup>) reductive elimination from platinum(II) diaryl complexes containing macrocyclic bis(phosphine) force probe ligands. Compressive forces decreased the rate of reductive elimination whereas extension forces increased the rate of reductive elimination relative to the strain-free MeOBiphep complex with a 3.4-fold change in rate over a ~290 pN range of restoring forces. The natural bite angle of the free ligand changes with force, but <sup>31</sup>P NMR analysis strongly suggests no significant force-induced perturbation of the ground state geometry of the (P–P)PtAr<sub>2</sub> complexes. Rather, the force/rate behavior observed across this range of forces (from ca. 65 pN in compression to >200 pN in extension) for reductive elimination is attributed to the coupling of force to the elongation of the O<b><sup>…</sup></b>O distance in the transition state for reductive elimination. The results suggest opportunities to experimentally map geometry changes associated with reactions in transition metal complexes and potential strat-egies for force-modulated catalysis. </p></div><br>

scholarly journals Force-Modulated Reductive Elimination from Platinum(II) Diaryl Complexes

2020 ◽  
Author(s):  
Yichen Yu ◽  
Liqi Wang ◽  
Chenxu Wang ◽  
Yancong Tian ◽  
Roman Boulatov ◽  
...  
Keyword(s):  
Transition Metal ◽  
Transition Metal Complexes ◽  
Free Ligand ◽  
Reductive Elimination ◽  
Mechanical Force ◽  
Mechanical Forces ◽  
Bite Angle ◽  
Restoring Forces ◽  
Rate Behavior ◽  
Ground State Geometry

<div><p>Coupled mechanical forces are known to drive a range of covalent chemical reactions, but the interplay of mechanical force applied to a spectator ligand and transition metal reactivity is relatively unexplored. Here we report the effect of mechanical force on the rate of C(sp<sup>2</sup>)-C(sp<sup>2</sup>) reductive elimination from platinum(II) diaryl complexes containing macrocyclic bis(phosphine) force probe ligands. Compressive forces decreased the rate of reductive elimination whereas extension forces increased the rate of reductive elimination relative to the strain-free MeOBiphep complex with a 3.4-fold change in rate over a ~290 pN range of restoring forces. The natural bite angle of the free ligand changes with force, but <sup>31</sup>P NMR analysis strongly suggests no significant force-induced perturbation of the ground state geometry of the (P–P)PtAr<sub>2</sub> complexes. Rather, the force/rate behavior observed across this range of forces (from ca. 65 pN in compression to >200 pN in extension) for reductive elimination is attributed to the coupling of force to the elongation of the O<b><sup>…</sup></b>O distance in the transition state for reductive elimination. The results suggest opportunities to experimentally map geometry changes associated with reactions in transition metal complexes and potential strat-egies for force-modulated catalysis. </p></div><br>

Charge effects regulate reversible CO2 reduction catalysis

2018 ◽  
Vol 54 (56) ◽  
pp. 7790-7793 ◽  
Author(s):  
Jacob B. Geri ◽  
Joanna L. Ciatti ◽  
Nathaniel K. Szymczak
Keyword(s):  
Formic Acid ◽  
Co2 Reduction ◽  
Ligand Design ◽  
Design Parameters ◽  
Charge Effects ◽  
Bite Angle ◽  
Geometrically Constrained ◽  
Formic Acid Dehydrogenation ◽  
The Impact

Modular but geometrically constrained ligands were used to investigate the impact of key ligand design parameters (charge and bite angle) on CO2 hydrogenation and formic acid dehydrogenation activity.

scholarly journals Mechanistic Investigation on Hydrocyanation of Butadiene: A DFT Study

Catalysts ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 818
Author(s):  
Kaikai Liu ◽  
Shuai Zhang ◽  
Minghan Han
Keyword(s):  
Transition States ◽  
Reductive Elimination ◽  
Dft Study ◽  
Hydrocyanic Acid ◽  
Bite Angle ◽  
Rate Determining Step ◽  
Mechanistic Investigation ◽  
Rate Determining Steps

The nickel-catalyzed addition of Hydrocyanic acid (HCN) to butadiene usually leads to a mixture of the branched 2-methyl-3-butenenitrile (2M3BN) and the linear 3-pentenenitrile (3PN) with a 30:70 ratio by employing mono-dentate phosphites, while a 97% selectivity to 3PN is obtained using a 1,4-bis(diphenyphosphino)butane (dppb) ligand and Ni(COD)2 (1,5-Cyclooctadiene) as catalysts. To explain this phenomenon, a reasonable mechanism of the hydrocyanation, involving the cyano (CN) migration (for 3PN) and the methylallyl rotation (for 2M3BN) pathways, is proposed. The key intermediates and the rate-determining steps in the pathways have been illustrated. The methylallyl rearrangement is the rate-determining step in the formation of 3PN while the reductive elimination governs the reaction to 2M3BN, which is subsequently isomerized to 3PN. Moreover, the opposite changes of the bite angle of the intermediates and transition states explain how the reactions proceed in two different directions.

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