Center for Molecular Modeling - S. E. Neale

Shape-selective C–H activation of aromatics to biarylic compounds using molecular palladium in zeolites

massimo — Mon, 16 Nov 2020 16:24:26 +0000

J. Vercammen, M. Bocus, S. E. Neale, A. Bugaev, P. Tomkins, J. Hajek, S. Van Minnebruggen, A. Soldatov, A. Krajnc, G. Mali, V. Van Speybroeck, D. De Vos

Nature Catalysis

3, 1002-1009

2020

Abstract

The selective activation of inert C–H bonds has emerged as a promising tool for avoiding the use of wasteful traditional coupling reactions. Oxidative coupling of simple aromatics allows for a cost-effective synthesis of biaryls. However, utilization of this technology is severely hampered by poor regioselectivity and by the limited stability of state-of-the-art homogeneous Pd catalysts. Here, we show that confinement of cationic Pd in the pores of a zeolite allows for the shape-selective C–H activation of simple aromatics without a functional handle or electronic bias. For instance, out of six possible isomers, 4,4′-bitolyl is produced with high shape selectivity (80%) in oxidative toluene coupling on Pd-Beta. Not only is a robust, heterogeneous catalytic system obtained, but this concept is also set to control the selectivity in transition-metal-catalysed arene C–H activation through spatial confinement in zeolite pores.

DOI

http://dx.doi.org/10.1038/s41929-020-00533-6

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Paper_final.pdf

Accurate computed spin-state energetics for Co(III) complexes: implications for modelling homogeneous catalysis

sneale — Mon, 04 May 2020 10:24:03 +0000

S. E. Neale, D. A. Pantazis, S. A. Macgregor

Dalton Transactions

2020

Published while none of the authors were employed at the CMM

Abstract

Co(III) complexes are increasingly prevalent in homogeneous catalysis. Catalytic cycles involve multiple intermediates, many of which will feature unsaturated metal centres. This raises the possibility of multi-state character along reaction pathways and so requires an accurate approach to calculating spin-state energetics. Here we report an assessment of the performance of DLPNO-CCSD(T) (domain-based local pair natural orbital approximation to coupled cluster theory) against experimental ¹Co to ³Co spin splitting energies for a series of pseudo-octahedral Co(III) complexes. The alternative NEVPT2 (strongly-contracted n-electron valence perturbation theory) and a range of density functionals are also assessed. DLPNO-CCSD(T) is identified as a highly promising method, with mean absolute deviations (MADs) as small as 1.3 kcal mol⁻¹ when Kohn–Sham reference orbitals are used. DLPNO-CCSD(T) out-performs NEVPT2 for which a MAD of 3.5 kcal mol⁻¹ can be achieved when a (10,12) active space is employed. Of the nine DFT methods investigated TPSS is the leading functional, with a MAD of 1.9 kcal mol⁻¹. Our results show how DLPNO-CCSD(T) can provide accurate spin state energetics for Co(III) species in particular and first row transition metal systems in general. DLPNO-CCSD(T) is therefore a promising method for applications in the burgeoning field of homogeneous catalysis based on Co(III) species.

DOI

https://doi.org/10.1039/D0DT00993H

A Structurally Characterized Cobalt(I) σ–Alkane Complex

sneale — Mon, 04 May 2020 10:19:59 +0000

T. M. Boyd, B. Tegner, G. Tizzard, A. Martinez-Martinez, S. E. Neale, M. Hayward, S. Coles, S. A. Macgregor, A. S. Weller

Angewandte Chemie int. Ed.

59 (15), 6177-6181

2020

Published while none of the authors were employed at the CMM

Abstract

A cobalt σ‐alkane complex, [Co(Cy₂P(CH₂)₄PCy₂)(norbornane)][BAr^F₄], was synthesized by a single‐crystal to single‐crystal solid/gas hydrogenation from a norbornadiene precursor, and its structure was determined by X‐ray crystallography. Magnetic data show this complex to be a triplet. Periodic DFT and electronic structure analyses revealed weak C−H→Co σ‐interactions, augmented by dispersive stabilization between the alkane ligand and the anion microenvironment. The calculations are most consistent with a η¹:η¹‐alkane binding mode.

DOI

https://doi.org/10.1002/anie.201914940

A Structurally Characterized Cobalt(I) σ–Alkane Complex

sneale — Mon, 04 May 2020 10:13:41 +0000

T. M. Boyd, B. Tegner, G. Tizzard, A. Martinez-Martinez, S. E. Neale, M. Hayward, S. Coles, S. A. Macgregor, A. S. Weller

Angewandte Chemie int. Ed.

59 (15), 6177-6181

2020

Published while none of the authors were employed at the CMM

Abstract

DOI

http://dx.doi.org/

Reductive Elimination at Carbon under Steric Control

sneale — Mon, 04 May 2020 10:10:35 +0000

D. R. Tolentino, S. E. Neale, C. J. Isaac, S. A. Macgregor, M. K. Whittlesey, R. Jazzar, G. Bertrand

JACS (Journal of the American Chemical Society)

141 (25), 9823-9826

2019

Published while none of the authors were employed at the CMM

Abstract

It has been previously demonstrated that stable singlet electrophilic carbenes can behave as metal surrogates in the activation of strong E–H bonds (E = H, B, N, Si, P), but it was believed that these activations only proceed through an irreversible activation barrier. Herein we show that, as is the case with transition metals, the steric environment can be used to promote reductive elimination at carbon centers.

DOI

https://doi.org/10.1021/jacs.9b04957

N-Heterocyclic Carbene Non-Innocence in the Catalytic Hydrophosphination of Alkynes

sneale — Mon, 04 May 2020 10:06:57 +0000

W. J. M. Blackaby, S. E. Neale, C. J. Isaac, S. Sabater, S. A. Macgregor, M. K. Whittlesey

ChemCatChem

11 (7), 1893-1897

2019

Published while none of the authors were employed at the CMM

Abstract

Studies on alkyne hydrophosphination employing nickel‐NHC catalysts (NHC=N‐heterocyclic carbene) revealed that the free N‐alkyl substituted NHCs themselves were catalytically active. DFT calculations showed the mechanism involves the NHC acting as a Brønsted base to form an imidazolium phosphide species which then undergoes rate‐limiting nucleophilic attack at the terminal alkyne carbon. This mechanism explains the preference seen experimentally for reactions with aryl substituted phosphines and alkynes, while the rearrangements of the alkenyl anion formed upon P−C bond formation account for the observation of both Z‐ and E‐regioisomers of the products.

DOI

https://doi.org/10.1002/cctc.201900220

Chemoselective Allene Aziridination via Ag(I) Catalysis

sneale — Mon, 04 May 2020 10:02:47 +0000

J. W. Rigoli, C. D. Weatherly, B. T. Vo, R. Van Hoveln, S. E. Neale, J. M. Schomaker

Organic Letters

15 (2), 290-293

2013

Published while none of the authors were employed at the CMM

Abstract

Allene aziridination generates useful bicyclic methylene aziridine scaffolds that can be flexibly transformed into a range of stereochemically complex and densely functionalized amine-containing stereotriads. The scope of this chemistry has been limited by the poor chemoselectivity that often results when typical dinuclear Rh(II) catalysts are employed with homoallenic carbamates. Herein, Ag(I) catalysts that significantly improve the scope and yield of bicyclic methylene aziridines that can be prepared via allene aziridination are described.

DOI

https://doi.org/10.1021/ol303167n

Beyond Benzyl Grignards: Facile Generation of Benzyl Carbanions from Styrenes

sneale — Mon, 04 May 2020 09:58:45 +0000

R. D. Grigg, J. W. Rigoli, R. Van Hoveln, S. E. Neale, J. M. Schomaker

Chemistry - A European Journal

18 (30), 9391-9396

2012

Published while none of the authors were employed at the CMM

Abstract

Benzylic functionalization is a convenient approach towards the conversion of readily available aromatic hydrocarbon feedstocks into more useful molecules. However, the formation of carbanionic benzyl species from benzyl halides or similar precursors is far from trivial. An alternative approach is the direct reaction of a styrene with a suitable coupling partner, but these reactions often involve the use of precious‐metal transition‐metal catalysts. Herein, we report the facile and convenient generation of reactive benzyl anionic species from styrenes. A Cu^I‐catalyzed Markovnikov hydroboration of the styrenic double bond by using a bulky pinacol borane source is followed by treatment with KOtBu to facilitate a sterically induced cleavage of the C-B bond to produce a benzylic carbanion. Quenching this intermediate with a variety of electrophiles, including CO₂, CS₂, isocyanates, and isothiocyanates, promotes C-C bond formation at the benzylic carbon atom. The utility of this methodology was demonstrated in a three‐step, two‐pot synthesis of the nonsteroidal anti‐inflammatory drug (±)‐flurbiprofen.

DOI

https://doi.org/10.1002/chem.201200642

Room Temperature Iron-Catalyzed Transfer Hydrogenation and Regioselective Deuteration of Carbon-Carbon Double Bonds

sneale — Mon, 04 May 2020 09:51:21 +0000

M. Espinal-Viguri, S. E. Neale, N. T. Coles, S. A. Macgregor, R. L. Webster

JACS (Journal of the American Chemical Society)

141 (1), 572-582

2019

Published while none of the authors were employed at the CMM

Abstract

An iron catalyst has been developed for the transfer hydrogenation of carbon–carbon multiple bonds. Using a well-defined β-diketiminate iron(II) precatalyst, a sacrificial amine and a borane, even simple, unactivated alkenes such as 1-hexene undergo hydrogenation within 1 h at room temperature. Tuning the reagent stoichiometry allows for semi- and complete hydrogenation of terminal alkynes. It is also possible to hydrogenate aminoalkenes and aminoalkynes without poisoning the catalyst through competitive amine ligation. Furthermore, by exploiting the separate protic and hydridic nature of the reagents, it is possible to regioselectively prepare monoisotopically labeled products. DFT calculations define a mechanism for the transfer hydrogenation of propene with ⁿBuNH₂ and HBpin that involves the initial formation of an iron(II)-hydride active species, 1,2-insertion of propene, and rate-limiting protonolysis of the resultant alkyl by the amine N–H bond. This mechanism is fully consistent with the selective deuteration studies, although the calculations also highlight alkene hydroboration and amine–borane dehydrocoupling as competitive processes. This was resolved by reassessing the nature of the active transfer hydrogenation agent: experimentally, a gel is observed in catalysis, and calculations suggest this can be formulated as an oligomeric species comprising H-bonded amine–borane adducts. Gel formation serves to reduce the effective concentrations of free HBpin and ⁿBuNH₂ and so disfavors both hydroboration and dehydrocoupling while allowing alkene migratory insertion (and hence transfer hydrogenation) to dominate.

DOI

https://doi.org/10.1021/jacs.8b11553

Comprehensive Inorganic Chemistry III (third edition)

massimo — Wed, 29 Sep 2021 07:50:06 +0000

M. Bocus, S. E. Neale, P. Cnudde, V. Van Speybroeck

Elsevier

2023

ISBN

9780124095472

Short content

Chapter 6.08: 'Dynamic evolution of catalytic active sites within zeolite catalysis', pages 165-200.

https://doi.org/10.1016/B978-0-12-823144-9.00012-1

C012_9780128231449.pdf