Ligand Self-Assembling through Complementary Hydrogen-Bonding in the Coordination Sphere of a Transition Metal Center: The 6-Diphenylphosphanylpyridin-2(1<i>H</i>)-one System

An ew type of ligand, which is able to form axially chiral, supramolecular complexes was designed using DFT calculations.T wo chiral monomers,each featuring acovalently bound chiral auxiliary,form abidentate phosphine ligand with at wisted, hydrogen-bonded backbone upon coordination to at ransition metal center whichr esults in two diastereomeric, tropos complexes.The ratio of the diastereomers in solution is very temperature-and solvent-dependent. Rhodium and platinum complexes were analyzed through ac ombination of NMR studies,E SI-MS measurements,a sw ell as UV-VIS and circular dichroism spectroscopy. The chiral self-organized ligands were evaluated in the rhodium-catalyzed asymmetric hydrogenation of a-dehydrogenated amino acids and resulted in good conversion and high enantioselectivity.T his research opens the wayfor new ligand designs based on stereocontrol of supramolecular assemblies through stereodirecting chiral centers.Ligands with an axially chiral backbone are among the most valuable systems used in asymmetric catalysis. [1][2][3][4] However, the asymmetric synthesis of such an inflexible (atropos) backbone is often long and difficult. Am ore intriguing approach is to use ligands with af lexible (tropos)b ackbone. [5,6] In such adynamic system, the resolution into one of the diastereomers is dependent on transfer of chiral information from as tereoregulating unit. This transfer has been achieved by coordination of achiral co-ligand or anion, [7][8][9][10][11] or control of the backbone by acovalently bound chiral auxiliary (Scheme 1). [12][13][14][15][16] Recently,control of axial chirality in a tropos ligand was demonstrated by association of small chiral molecules through hydrogen bonding. [17,18] In this manner, ab y-design nonlinear amplification of stereoselectivity was achieved.Self-assembly ligand systems have also been used successfully in asymmetric catalysis, [19] and the necessary asymmetric induction has so far been achieved using building blocks with either chiral P-donors [20][21][22][23] or an axially chiral biphenyl moiety as as tereoregulating unit. [24] Theg roups of Raynal and Vidal-Ferran achieved stereocontrol through the coassembly of chiral benzene-1,3,5-tricarboxamides (BTA) with achiral BTAs functionalized with P-donor moieties in ahelical scaffold. [25,26] Theg roup of Reek demonstrated that stereocontrol in asupramolecular catalyst system could be achieved by either entrapment of the rhodium center in asupramolecular metallocage [27] or by molecular recognition of ac hiral cofactor in ab identate ligand. [9,28] Also chiral phosphoric acids have been used for supramolecular stereoregulation through ion pairing in asymmetric catalysis. [29,30] Our group has previously developed self-organizing ligand systems based on self-assembly of monodentate building blocks through hydrogen bonding (6-DPPon = 6-diphenylphosphino pyridone,see Scheme 2f or R = Ph and S* = H), [31] and these bidentate ligands were successfully employed in hydroformylation and hydrocyanation of alkenes. [31]...

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“…[43] Similar behavior was observed when studying 1, 2,a nd 3. [43] Similar behavior was observed when studying 1, 2,a nd 3.…”

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confidence: 73%

Inducing Axial Chirality in a Supramolecular Catalyst

2018

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“…Crystal structure analysis of symmetrical complex 1 demonstrates coordination geometry around each iridium atom is distorted octahedral . Assuming that Cp* serves as a three‐coordinate ligand, the molecular structure of 1 reveals that the six‐coordinate geometry of the Ir (III) center has a three‐legged piano‐stool motif, in which the legs are one N atom of pyrrole ring, one N atom of the imine group, and one chlorido ligand . In addition, the C–N bond lengths are in comparison with the corresponding parameters described for other similarly constituted complexes .…”

Section: Resultsmentioning

confidence: 97%

Half‐sandwich Ir (III) and Rh (III) complexes as catalysts for water oxidation with double‐site

Peng

Liu

Han

et al. 2019

Applied Organom Chemis

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A series of neutral binuclear iridium and rhodium complexes were synthesized based on bis‐imine ligands under mild conditions. These half‐sandwich late transition metal complexes were isolated in good yields and characterized by elemental analysis, 1H NMR, 13C NMR, HR‐MS, and FT‐IR spectroscopies, and the solid state structure of complexes 1 and 2 were further confirmed by single‐crystal X‐ray diffraction. Cyclic voltammetry (CV) characterization indicated that the complex 1 has the best catalyst for water oxidation process with TOF of 0.8 s−1 at low overpotential of 0.325 V in methanol‐phosphate buffer. The proposed double‐site water oxidation mechanism had been also speculated.

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“…Together with molecular mechanics for proton transfer (MMPT), [58] VBT was also successfully used to follow the structural dynamics and associated time scales around platinum complexes relevant to hydroformylation reactions. [59,60] Specifically, all experimentally observed time scales for the reorganization involving the Pt-complex could be quantitatively interpreted based on the simulation results. This highlights the prominent role of atomistic .…”

Section: Solvation Dynamicsmentioning

confidence: 99%

Quantitative Atomistic Simulations of Reactive and Non-Reactive Processes

Meuwly¹

2014

Chimia

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The interpretation of physico-chemical observables in terms of atomic motions is one of the primary objectives of atomistic simulations. Trajectories from a molecular simulation contain much valuable information about the relationship between motion of the atoms and physical observables related to them, provided that the interactions used to generate the trajectories are of sufficiently high quality. On the other hand, many experimental observables are averages over a large number of physical realizations of the system. Thus, a statistically large number of trajectories needs to be generated and analyzed in order to provide a meaningful basis for comparison with and interpretation of experiments. The preferred computational approach which allows such extensive averaging while retaining the quantitative aspects of the intermolecular interactions are accurate force field-based molecular dynamics simulations. This contribution provides an overview of our group's current technological improvements in force field technology and its application to fundamental physico-chemical questions.Keywords: Computational spectroscopy · Force fields · Molecular dynamics simulations · Multipoles · Reaction dynamicsIn the physical sciences simulations provide a third approach -next to experiment and theory -to characterize and understand a wide range of phenomena. For chemistry and chemical physics in particular, atomistic simulations are paramount in providing insights into the energetics and dynamics of complex systems, such as proteins, chemical reactivity, solvation dynamics or spectroscopy.The use of atomistic simulations in reaction dynamics has been established for almost 50 years when molecular dynamics (MD) simulations were used to better understand the H 2 + H reaction dynamics. [1] Since then, MD simulations have become an important complement to investigate complex systems at atomic resolution. The major driving forces behind this development are i) the increase in computational power, ii) the improvement of algorithms and energy functions and iii) the more direct interaction between experiment and simulation. It is the latter that will eventually let this field mature to a degree which allows quantitative and ideally predictive work to be carried out which must be the ultimate goal of atomistic simulations.In the present contribution I will summarize our efforts to item ii) above. More specifically, our group is concerned with improved and widely applicable energy functions for spectroscopic and thermodynamic applications and the development of computational methods to follow chemical reactions in the gas phase and in solution. Quantitative Intermolecular InteractionsWithin the framework of atomistic simulations, intermolecular interactions are described by an empirical energy function ('force field') which is based on a ball-andspring model for the bonded interactions (such as bonds, valence angles, dihedrals) and Coulomb and van der Waals interactions for the nonbonded interactions. [2] This is in contrast t...

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Ligand Self-Assembling through Complementary Hydrogen-Bonding in the Coordination Sphere of a Transition Metal Center: The 6-Diphenylphosphanylpyridin-2(1H)-one System

Cited by 46 publications

References 33 publications

Inducing Axial Chirality in a Supramolecular Catalyst

Inducing Axial Chirality in a Supramolecular Catalyst

Half‐sandwich Ir (III) and Rh (III) complexes as catalysts for water oxidation with double‐site

Quantitative Atomistic Simulations of Reactive and Non-Reactive Processes

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