ORCID Profile
0000-0003-1646-8081
Current Organisation
University of York
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Publisher: American Chemical Society (ACS)
Date: 23-01-2023
DOI: 10.1021/JACS.2C12642
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3SC00052D
Publisher: American Chemical Society (ACS)
Date: 02-03-2012
DOI: 10.1021/JA211649A
Abstract: Readily prepared and bench-stable rhodium complexes containing methylene bridged diphosphine ligands, viz. [Rh(C(6)H(5)F)(R(2)PCH(2)PR'(2))][BAr(F)(4)] (R, R' = (t)Bu or Cy Ar(F) = C(6)H(3)-3,5-(CF(3))(2)), are shown to be practical and very efficient precatalysts for the intermolecular hydroacylation of a wide variety of unactivated alkenes and alkynes with β-S-substituted aldehydes. Intermediate acyl hydride complexes [Rh((t)Bu(2)PCH(2)P(t)Bu(2))H{κ(2)(S,C)-SMe(C(6)H(4)CO)}(L)](+) (L = acetone, MeCN, [NCCH(2)BF(3)](-)) and the decarbonylation product [Rh((t)Bu(2)PCH(2)P(t)Bu(2))(CO)(SMePh)](+) have been characterized in solution and by X-ray crystallography from stoichiometric reactions employing 2-(methylthio)benzaldehdye. Analogous complexes with the phosphine 2-(diphenylphosphino)benzaldehyde are also reported. Studies indicate that through judicious choice of solvent and catalyst/substrate concentration, both decarbonylation and productive hydroacylation can be tuned to such an extent that very low catalyst loadings (0.1 mol %) and turnover frequencies of greater than 300 h(-1) can be achieved. The mechanism of catalysis has been further probed by KIE and deuterium labeling experiments. Combined with the stoichiometric studies, a mechanism is proposed in which both oxidative addition of the aldehyde to give an acyl hydride and insertion of the hydride into the alkene are reversible, with the latter occurring to give both linear and branched alkyl intermediates, although reductive elimination for the linear isomer is suggested to have a considerably lower barrier.
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C7SC01491K
Abstract: Solid-state molecular organometallic catalysis (SMOM-cat): synthetic routes, unique structural motifs, mobility in the solid-state and very active gas/solid isomerization catalysts.
Publisher: American Chemical Society (ACS)
Date: 06-01-2020
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9DT03358K
Abstract: Cationic σ-dihydrogen, σ-amine-borane and neutral hydride complexes, based upon {Rh(PONOP)}, are all shown play a role in the dehydrocoupling of H 3 B·NMe 2 H. Movement between the three is promoted by free amine, NMe 2 H.
Publisher: American Chemical Society (ACS)
Date: 23-09-2016
Publisher: Wiley
Date: 11-02-2020
Abstract: The synthesis of rhodium complexes with weakly binding highly fluorinated benzene ligands is described: 1,2,3‐F 3 C 6 H 3 , 1,2,3,4‐F 4 C 6 H 2 and 1,2,3,4,5‐F 5 C 6 H are shown to bind with cationic [Rh(Cy 2 P(CH 2 ) x PCy 2 )] + fragments ( x= 1, 2). Their structures and reactivity with alkenes, and use in catalysis for promoting the Tishchenko reaction of a simple aldehyde, are demonstrated. Key to the synthesis of these complexes is the highly concentrated reaction conditions and use of the [Al{OC(CF 3 ) 3 } 4 ] − anion.
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/D0CC01140A
Abstract: Surface-initiated cationic polymerisation of ethylvinylether at single-crystals of the σ-alkane complex [Rh(Cy 2 PCH 2 CH 2 PCy 2 )(NBA)][BAr F 4 ] imparts air-tolerance to this highly reactive complex.
Publisher: American Chemical Society (ACS)
Date: 03-10-2016
DOI: 10.1021/JACS.6B07968
Abstract: The controlled catalytic functionalization of alkanes via the activation of C-H bonds is a significant challenge. Although C-H activation by transition metal catalysts is often suggested to operate via intermediate σ-alkane complexes, such transient species are difficult to observe due to their instability in solution. This instability may be controlled by use of solid/gas synthetic techniques that enable the isolation of single-crystals of well-defined σ-alkane complexes. Here we show that, using this unique platform, selective alkane C-H activation occurs, as probed by H/D exchange using D
Publisher: American Chemical Society (ACS)
Date: 05-03-2015
Publisher: Wiley
Date: 12-01-2021
Publisher: American Chemical Society (ACS)
Date: 07-02-2012
DOI: 10.1021/JA2108992
Abstract: A Rh(I)-catalyzed method for the efficient functionalization of arenes is reported. Aryl methyl sulfides are combined with terminal alkynes to deliver products of carbothiolation. The overall process results in reincorporation of the original arene functional group, a methyl sulfide, into the products as an alkenyl sulfide. The carbothiolation process can be combined with an initial Rh(I)-catalyzed alkene or alkyne hydroacylation reaction in three-component cascade sequences. The utility of the alkenyl sulfide products is also demonstrated in simple carbo- and heterocycle-forming processes. We also provide mechanistic evidence for the course of this new process.
Publisher: American Chemical Society (ACS)
Date: 27-01-2022
Publisher: Wiley
Date: 21-02-2011
Publisher: American Chemical Society (ACS)
Date: 10-10-2018
DOI: 10.1021/JACS.8B09364
Abstract: Solid/gas single-crystal to single-crystal (SC-SC) hydrogenation of appropriate diene precursors forms the corresponding σ-alkane complexes [Rh(Cy
Publisher: American Chemical Society (ACS)
Date: 17-07-2017
DOI: 10.1021/JACS.7B05713
Abstract: Readily available β-carbonyl-substituted aldehydes are shown to be exceptional substrates for Rh-catalyzed intermolecular alkene and alkyne hydroacylation reactions. By using cationic rhodium catalysts incorporating bisphosphine ligands, efficient and selective reactions are achieved for β-amido, β-ester, and β-keto aldehyde substrates, providing a range of synthetically useful 1,3-dicarbonyl products in excellent yields. A correspondingly broad selection of alkenes and alkynes can be employed. For alkyne substrates, the use of a catalyst incorporating the Ampaphos ligand triggers a regioselectivity switch, allowing both linear and branched isomers to be prepared with high selectivity in an efficient manner. Structural data, confirming aldehyde chelation, and a proposed mechanism are provided.
Publisher: Wiley
Date: 14-11-2011
Publisher: American Chemical Society (ACS)
Date: 22-01-2018
DOI: 10.1021/JACS.7B11975
Abstract: A systematic study of the catalyst structure and overall charge for the dehydropolymerization of H
Publisher: American Chemical Society (ACS)
Date: 26-03-2021
DOI: 10.1021/JACS.1C00738
Publisher: American Chemical Society (ACS)
Date: 27-06-2019
DOI: 10.1021/JACS.9B05577
Publisher: American Chemical Society (ACS)
Date: 04-06-2018
Publisher: American Chemical Society (ACS)
Date: 15-09-2016
Publisher: Wiley
Date: 16-01-2013
Abstract: A new functional-group tolerant, rhodium-catalyzed, sulfide-reduction process is combined with rhodium-catalyzed chelation-controlled hydroacylation reactions to give a traceless hydroacylation protocol. Aryl- and alkenyl aldehydes can be combined with both alkenes, alkynes and allenes to give traceless products in high yields. A preliminary mechanistic proposal is also presented.
Publisher: Elsevier
Date: 2016
Publisher: American Chemical Society (ACS)
Date: 26-07-2022
Publisher: Wiley
Date: 22-03-2018
Abstract: Crabtree's catalyst was encapsulated inside the pores of the sulfonated MIL‐101(Cr) metal–organic framework (MOF) by cation exchange. This hybrid catalyst is active for the heterogeneous hydrogenation of non‐functionalized alkenes either in solution or in the gas phase. Moreover, encapsulation inside a well‐defined hydrophilic microenvironment enhances catalyst stability and selectivity to hydrogenation over isomerization for substrates bearing ligating functionalities. Accordingly, the encapsulated catalyst significantly outperforms its homogeneous counterpart in the hydrogenation of olefinic alcohols in terms of overall conversion and selectivity, with the chemical microenvironment of the MOF host favouring one out of two competing reaction pathways.
Publisher: Wiley
Date: 27-12-2019
Publisher: Elsevier BV
Date: 05-2015
Publisher: Royal Society of Chemistry (RSC)
Date: 2010
DOI: 10.1039/B919209C
Abstract: A combined structural/EPR/computational chemistry investigation is reported on the two paramagnetic hydrido-cluster salts [Rh(6)(PCy(3))(6)H(12)][BAr(F)(4)] and [Rh(6)(PCy(3))(6)H(14)][BAr(F)(4)], the latter being formed by reversible addition of H(2) to the former, [BAr(F)(4)](-) = [B{C(6)H(3)(CF(3))(2)}(4)](-). The solid-state structure of [Rh(6)(PCy(3))(6)H(14)][BAr(F)(4)] shows an expanded cluster core compared to previously reported [Rh(6)(PCy(3))(6)H(12)][BAr(F)(4)] indicative of the addition of hydrogen to the cluster surface. This expansion correlates well with the calculated (PH(3) replaces PCy(3)) structures. EPR measurements on [Rh(6)(PCy(3))(6)H(12)][BAr(F)(4)] indicate two isomers at low temperature, which are tentatively assigned as diastereomers that result from locked phosphine rotation and bridging hydride/semi bridging hydride tautomerism. The EPR signal disappears above 60 K which is suggested to occur due to fast Raman-type relaxation-a phenomenon consistent with the calculated small SOMO/SOMO - 1 and SOMO/LUMO gaps. For [Rh(6)(PCy(3))(6)H(14)][BAr(F)(4)] EPR measurements indicate two isomers, the proportion of which change with temperature and deuteration-one axial isomer and one rhombic isomer. DFT calculations on a number of plausible isomers give EPR parameters which fit the experimentally determined rhombic isomer to one in which there is an interstitial hydride in the cluster and thirteen hydride ligands on the surface, while the axial isomer has two dihydrogen-like ligands on the cluster surface. That these isomers lie close in energy comes from both the EPR measurements (as measured from equilibrium constants over a variable temperature range) and DFT calculations. Deuteration of the hydrides should favour the isomer with the lowest zero-point energy and this is the case, with the axial isomer (two D(2) ligands on the surface) being favoured over the rhombic.
Publisher: American Chemical Society (ACS)
Date: 19-11-2012
DOI: 10.1021/CS300541M
Publisher: Wiley
Date: 23-03-2018
Abstract: The rhodium complex [Rh(Ph
Publisher: Wiley
Date: 22-03-2018
Abstract: Crabtree's catalyst was encapsulated inside the pores of the sulfonated MIL‐101(Cr) metal–organic framework (MOF) by cation exchange. This hybrid catalyst is active for the heterogeneous hydrogenation of non‐functionalized alkenes either in solution or in the gas phase. Moreover, encapsulation inside a well‐defined hydrophilic microenvironment enhances catalyst stability and selectivity to hydrogenation over isomerization for substrates bearing ligating functionalities. Accordingly, the encapsulated catalyst significantly outperforms its homogeneous counterpart in the hydrogenation of olefinic alcohols in terms of overall conversion and selectivity, with the chemical microenvironment of the MOF host favouring one out of two competing reaction pathways.
Publisher: American Chemical Society (ACS)
Date: 09-02-2015
DOI: 10.1021/OM500984Y
Publisher: American Chemical Society (ACS)
Date: 11-03-2019
Publisher: Wiley
Date: 24-08-2018
Abstract: In an attempt to prepare new Fe catalysts for the dehydrocoupling of amine-boranes and to provide mechanistic insight, the paramagnetic Fe
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3DT50817J
Abstract: The synthesis of a range of bis(phosphine)boronium salts is reported [(R2HP)2BH2][X] (R = Ph, (t)Bu, Cy) in which the counter anion is also varied (X(-) = Br(-), [OTf](-), [BAr(F)4](-), Ar(F) = 3,5-(CF3)2C6H3). Characterization in the solid-state by X-ray diffraction suggests there are weak hydrogen bonds between the PH units of the boronium cation and the anion (X(-) = Br(-), [OTf](-)), while solution NMR spectroscopy also reveals hydrogen bonding occurs in the order [BAr(F)4](-) < [OTf](-) < Br(-). [(Ph2HP)2BH2][BAr(F)4] reacts with RhH(PPh3)3, by elimination of H2, forming [Rh(κ(1),η-PPh2BH2·PPh2H)(PPh3)2][BAr(F)4] which shows a β-B-agostic interaction from the resulting base stabilised phosphino-borane ligand. Alternatively such ligands can be assembled directly on the metal centre by reaction of in situ generated {Rh(PPh3)3}(+) and Ph2HP·BH3 to afford [Rh(κ(1),η-PPh2BH2·PPh3)(PPh3)2][BAr(F)4], which was characterised by X-ray crystallography. Addition of H3B·PPh2H to the well-defined 16-electron "T-shaped" complex [Rh(P(i)Bu3)2(PPh3)][BAr(F)4] (characterised by X-ray crystallography) formed of a mixture of base-stabilised phosphino borane ligated complexes [Rh(κ(1),η-PR2BH2·PR3)(PR3)2][BAr(F)4] (R = (i)Bu or Ph). These last observations may lend clues to the formation of bis(phosphine)boronium salts in the catalytic dehydrocoupling reaction of phosphine boranes as mediated by Rh(I) compounds.
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Andrew Weller.