1
|
Sajjad MA, Macgregor SA, Weller AS. A comparison of non-covalent interactions in the crystal structures of two σ-alkane complexes of Rh exhibiting contrasting stabilities in the solid state. Faraday Discuss 2023; 244:222-240. [PMID: 37096331 DOI: 10.1039/d3fd00009e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Non-covalent interactions surrounding the cationic Rh σ-alkane complexes within the crystal structures of [(Cy2PCH2CH2PCy2)Rh(NBA)][BArF4], [1-NBA][BArF4] (NBA = norbornane, C7H12; ArF = 3,5-(CF3)2C6H3), and [1-propane][BArF4] are analysed using Quantum Theory of Atoms in Molecules (QTAIM) and Independent Gradient Model approaches, the latter under a Hirshfeld partitioning scheme (IGMH). In both structures the cations reside in an octahedral array of [BArF4]- anions within which the [1-NBA]+ cation system exhibits a greater number of C-H⋯F contacts to the anions. QTAIM and IGMH analyses indicate these include the strongest individual atom-atom non-covalent interactions between the cation and the anion in these systems. The IGMH approach highlights the directionality of these C-H⋯F contacts that contrasts with the more diffuse C-H⋯π interactions. The accumulative effects of the latter lead to a more significant stabilizing contribution. IGMH %δGatom plots provide a particularly useful visual tool to identify key interactions and highlight the importance of a -{C3H6}- propylene moiety that is present within both the propane and NBA ligands (the latter as a truncated -{C3H4}- unit) and the cyclohexyl rings of the phosphine substituents. The potential for this to act as a privileged motif that confers stability on the crystal structures of σ-alkane complexes in the solid-state is discussed. The greater number of C-H⋯F inter-ion interactions in the [1-NBA][BArF4] system, coupled with more significant C-H⋯π interactions are all consistent with greater non-covalent stabilisation around the [1-NBA]+ cation. This is also supported by larger computed δGatom indices as a measure of cation-anion non-covalent interaction energy.
Collapse
Affiliation(s)
- M Arif Sajjad
- Institute of Chemical Sciences, Heriot-Watt University, Edinburgh, EH14 4AS, UK.
| | - Stuart A Macgregor
- Institute of Chemical Sciences, Heriot-Watt University, Edinburgh, EH14 4AS, UK.
| | - Andrew S Weller
- Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK
| |
Collapse
|
2
|
Doyle LR, Thompson EA, Burnage AL, Whitwood AC, Jenkins HT, Macgregor SA, Weller AS. MicroED characterization of a robust cationic σ-alkane complex stabilized by the [B(3,5-(SF 5) 2C 6H 3) 4] - anion, via on-grid solid/gas single-crystal to single-crystal reactivity. Dalton Trans 2022; 51:3661-3665. [PMID: 35156982 PMCID: PMC8902584 DOI: 10.1039/d2dt00335j] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Microcrystalline (∼1 μm) [Rh(Cy2PCH2CH2PCy2)(norbornadiene)][S-BArF4], [S-BArF4] = [B(3,5-(SF5)2C6H3)4]−, reacts with H2 in a single-crystal to single-crystal transformation to form the σ-alkane complex [Rh(Cy2PCH2CH2PCy2)(norbornane)][S-BArF4], for which the structure was determined by microcrystal Electron Diffraction (microED), to 0.95 Å resolution, via an on-grid hydrogenation, and a complementary single-crystal X-ray diffraction study on larger, but challenging to isolate, crystals. Comparison with the [BArF4]− analogue [ArF = 3,5-(CF3)2(C6H3)] shows that the [S-BArF4]− anion makes the σ-alkane complex robust towards decomposition both thermally and when suspended in pentane. Subsequent reactivity with dissolved ethene in a pentane slurry, forms [Rh(Cy2PCH2CH2PCy2)(ethene)2][S-BArF4], and the catalytic dimerisation/isomerisation of ethene to 2-butenes. The increased stability of [S-BArF4]− salts is identified as being due to increased non-covalent interactions in the lattice, resulting in a solid-state molecular organometallic material with desirable stability characteristics. The thermally and chemically robust σ-alkane complex [Rh(Cy2PCH2CH2PCy2)(norborane)][B(3,5-(SF5)2C6H3)4] is characterized by micro-electron diffraction using on-grid single-crystal to single-crystal reactivity.![]()
Collapse
Affiliation(s)
- Laurence R Doyle
- Department of Chemistry, University of York, Heslington, York YO10 5DD, UK.
| | - Emily A Thompson
- Department of Chemistry, University of York, Heslington, York YO10 5DD, UK.
| | - Arron L Burnage
- Institute of Chemical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, UK.
| | - Adrian C Whitwood
- Department of Chemistry, University of York, Heslington, York YO10 5DD, UK.
| | - Huw T Jenkins
- Department of Chemistry, University of York, Heslington, York YO10 5DD, UK.
| | - Stuart A Macgregor
- Institute of Chemical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, UK.
| | - Andrew S Weller
- Department of Chemistry, University of York, Heslington, York YO10 5DD, UK.
| |
Collapse
|
3
|
Perutz RN, Sabo‐Etienne S, Weller AS. Metathesis by Partner Interchange in σ-Bond Ligands: Expanding Applications of the σ-CAM Mechanism. Angew Chem Int Ed Engl 2022; 61:e202111462. [PMID: 34694734 PMCID: PMC9299125 DOI: 10.1002/anie.202111462] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Indexed: 12/13/2022]
Abstract
In 2007 two of us defined the σ-Complex Assisted Metathesis mechanism (Perutz and Sabo-Etienne, Angew. Chem. Int. Ed. 2007, 46, 2578-2592), that is, the σ-CAM concept. This new approach to reaction mechanisms brought together metathesis reactions involving the formation of a variety of metal-element bonds through partner-interchange of σ-bond complexes. The key concept that defines a σ-CAM process is a single transition state for metathesis that is connected by two intermediates that are σ-bond complexes while the oxidation state of the metal remains constant in precursor, intermediates and product. This mechanism is appropriate in situations where σ-bond complexes have been isolated or computed as well-defined minima. Unlike several other mechanisms, it does not define the nature of the transition state. In this review, we highlight advances in the characterization and dynamic rearrangements of σ-bond complexes, most notably alkane and zincane complexes, but also different geometries of silane and borane complexes. We set out a selection of catalytic and stoichiometric examples of the σ-CAM mechanism that are supported by strong experimental and/or computational evidence. We then draw on these examples to demonstrate that the scope of the σ-CAM mechanism has expanded to classes of reaction not envisaged in 2007 (additional σ-bond ligands, agostic complexes, sp2 -carbon, surfaces). Finally, we provide a critical comparison to alternative mechanisms for metathesis of metal-element bonds.
Collapse
Affiliation(s)
| | - Sylviane Sabo‐Etienne
- CNRSLCC (Laboratoire de Chimie de Coordination)205 route de Narbonne, BP 44099F-31077Toulouse Cedex 4France
| | | |
Collapse
|
4
|
Perutz RN, Sabo‐Etienne S, Weller AS. Metathesis by Partner Interchange in σ‐Bond Ligands: Expanding Applications of the σ‐CAM Mechanism. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202111462] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
| | - Sylviane Sabo‐Etienne
- CNRS LCC (Laboratoire de Chimie de Coordination) 205 route de Narbonne, BP 44099 F-31077 Toulouse Cedex 4 France
| | | |
Collapse
|
5
|
Bukvic A, Burnage AL, Tizzard GJ, Martínez-Martínez AJ, McKay AI, Rees NH, Tegner BE, Krämer T, Fish H, Warren MR, Coles SJ, Macgregor SA, Weller AS. A Series of Crystallographically Characterized Linear and Branched σ-Alkane Complexes of Rhodium: From Propane to 3-Methylpentane. J Am Chem Soc 2021; 143:5106-5120. [PMID: 33769815 PMCID: PMC8154534 DOI: 10.1021/jacs.1c00738] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Indexed: 12/12/2022]
Abstract
Using solid-state molecular organometallic (SMOM) techniques, in particular solid/gas single-crystal to single-crystal reactivity, a series of σ-alkane complexes of the general formula [Rh(Cy2PCH2CH2PCy2)(ηn:ηm-alkane)][BArF4] have been prepared (alkane = propane, 2-methylbutane, hexane, 3-methylpentane; ArF = 3,5-(CF3)2C6H3). These new complexes have been characterized using single crystal X-ray diffraction, solid-state NMR spectroscopy and DFT computational techniques and present a variety of Rh(I)···H-C binding motifs at the metal coordination site: 1,2-η2:η2 (2-methylbutane), 1,3-η2:η2 (propane), 2,4-η2:η2 (hexane), and 1,4-η1:η2 (3-methylpentane). For the linear alkanes propane and hexane, some additional Rh(I)···H-C interactions with the geminal C-H bonds are also evident. The stability of these complexes with respect to alkane loss in the solid state varies with the identity of the alkane: from propane that decomposes rapidly at 295 K to 2-methylbutane that is stable and instead undergoes an acceptorless dehydrogenation to form a bound alkene complex. In each case the alkane sits in a binding pocket defined by the {Rh(Cy2PCH2CH2PCy2)}+ fragment and the surrounding array of [BArF4]- anions. For the propane complex, a small alkane binding energy, driven in part by a lack of stabilizing short contacts with the surrounding anions, correlates with the fleeting stability of this species. 2-Methylbutane forms more short contacts within the binding pocket, and as a result the complex is considerably more stable. However, the complex of the larger 3-methylpentane ligand shows lower stability. Empirically, there therefore appears to be an optimal fit between the size and shape of the alkane and overall stability. Such observations are related to guest/host interactions in solution supramolecular chemistry and the holistic role of 1°, 2°, and 3° environments in metalloenzymes.
Collapse
Affiliation(s)
- Alexander
J. Bukvic
- Department
of Chemistry, University of York, Heslington, York YO10
5DD, U.K.
- Department
of Chemistry, Chemistry Research Laboratories, University of Oxford, Oxford OX1 3TA, U.K.
| | - Arron L. Burnage
- Institute
of Chemical Sciences, Heriot-Watt University, Edinburgh EH14 4AS. U.K.
| | - Graham J. Tizzard
- UK
National Crystallography Service, University
of Southampton, Highfield, Southampton SO17 1BJ, U.K.
| | | | - Alasdair I. McKay
- Department
of Chemistry, Chemistry Research Laboratories, University of Oxford, Oxford OX1 3TA, U.K.
| | - Nicholas H. Rees
- Department
of Chemistry, Chemistry Research Laboratories, University of Oxford, Oxford OX1 3TA, U.K.
| | - Bengt E. Tegner
- Institute
of Chemical Sciences, Heriot-Watt University, Edinburgh EH14 4AS. U.K.
| | - Tobias Krämer
- Institute
of Chemical Sciences, Heriot-Watt University, Edinburgh EH14 4AS. U.K.
| | - Heather Fish
- Department
of Chemistry, University of York, Heslington, York YO10
5DD, U.K.
| | - Mark R. Warren
- Diamond
Light Source Ltd., Diamond House,
Harwell Science and Innovation Campus, Didcot OX11 0DE, U.K.
| | - Simon J. Coles
- UK
National Crystallography Service, University
of Southampton, Highfield, Southampton SO17 1BJ, U.K.
| | - Stuart A. Macgregor
- Institute
of Chemical Sciences, Heriot-Watt University, Edinburgh EH14 4AS. U.K.
| | - Andrew S. Weller
- Department
of Chemistry, University of York, Heslington, York YO10
5DD, U.K.
| |
Collapse
|
6
|
Furfari SK, Tegner BE, Burnage AL, Doyle LR, Bukvic AJ, Macgregor SA, Weller AS. Selectivity of Rh⋅⋅⋅H-C Binding in a σ-Alkane Complex Controlled by the Secondary Microenvironment in the Solid State. Chemistry 2021; 27:3177-3183. [PMID: 33112000 PMCID: PMC7898853 DOI: 10.1002/chem.202004585] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Revised: 10/27/2020] [Indexed: 12/13/2022]
Abstract
Single-crystal to single-crystal solid-state molecular organometallic (SMOM) techniques are used for the synthesis and structural characterization of the σ-alkane complex [Rh(tBu2 PCH2 CH2 CH2 PtBu2 )(η2 ,η2 -C7 H12 )][BArF 4 ] (ArF =3,5-(CF3 )2 C6 H3 ), in which the alkane (norbornane) binds through two exo-C-H⋅⋅⋅Rh interactions. In contrast, the bis-cyclohexyl phosphine analogue shows endo-alkane binding. A comparison of the two systems, supported by periodic DFT calculations, NCI plots and Hirshfeld surface analyses, traces this different regioselectivity to subtle changes in the local microenvironment surrounding the alkane ligand. A tertiary periodic structure supporting a secondary microenvironment that controls binding at the metal site has parallels with enzymes. The new σ-alkane complex is also a catalyst for solid/gas 1-butene isomerization, and catalyst resting states are identified for this.
Collapse
Affiliation(s)
| | - Bengt E. Tegner
- Institute of Chemical SciencesHeriot-Watt UniversityEdinburghEH14 4ASUK
| | - Arron L. Burnage
- Institute of Chemical SciencesHeriot-Watt UniversityEdinburghEH14 4ASUK
| | | | - Alexander J. Bukvic
- Department of ChemistryUniversity of YorkYorkYO10 5DDUK
- Department of ChemistryUniversity of OxfordMansfield RoadOxfordOX1 3TAUK
| | | | | |
Collapse
|
7
|
Peralta RA, Huxley MT, Evans JD, Fallon T, Cao H, He M, Zhao XS, Agnoli S, Sumby CJ, Doonan CJ. Highly Active Gas Phase Organometallic Catalysis Supported Within Metal-Organic Framework Pores. J Am Chem Soc 2020; 142:13533-13543. [PMID: 32650640 DOI: 10.1021/jacs.0c05286] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Metal-organic frameworks (MOFs) can act as a platform for the heterogenization of molecular catalysts, providing improved stability, allowing easy catalyst recovery and a route toward structural elucidation of the active catalyst. We have developed a MOF, 1, possessing vacant N,N-chelating sites which are accessible via the porous channels that penetrate the structure. In the present work, cationic rhodium(I) norbornadiene (NBD) and bis(ethylene) (ETH) complexes paired with both noncoordinating and coordinating anions have been incorporated into the N,N-chelation sites of 1 via postsynthetic metalation and facile anion exchange. Exploiting the crystallinity of the host framework, the immobilized Rh(I) complexes were structurally characterized using X-ray crystallography. Ethylene hydrogenation catalysis by 1·[Rh(NBD)]X and 1·[Rh(ETH)2]X (X = Cl and BF4) was studied in the gas phase (2 bar, 46 °C) to reveal that 1·[Rh(ETH)2](BF4) was the most active catalyst (TOF = 64 h-1); the NBD materials and the chloride salt were notably less active. On the basis of these observations, the activity of the Rh(I) bis(ethylene) complexes, 1·[Rh(ETH)2]BF4 and 1·[Rh(ETH)2]Cl, in butene isomerization was also studied using gas-phase NMR spectroscopy. Under one bar of butene at 46 °C, 1·[Rh(ETH)2]BF4 rapidly catalyzes the conversion of 1-butene to 2-butene with a TOF averaging 2000 h-1 over five cycles. Notably, the chloride derivative, 1 [Rh(ETH)2]Cl displays negligible activity in comparison. XPS analysis of the postcatalysis sample, supported by DFT calculations, suggest that the catalytic activity is inhibited by the strong interactions between a Rh(III) allyl hydride intermediate and the chloride anion.
Collapse
Affiliation(s)
- Ricardo A Peralta
- Centre for Advanced Nanomaterials and Department of Chemistry, The University of Adelaide, North Terrace, Adelaide, South Australia 5000, Australia
| | - Michael T Huxley
- Centre for Advanced Nanomaterials and Department of Chemistry, The University of Adelaide, North Terrace, Adelaide, South Australia 5000, Australia
| | - Jack D Evans
- Department of Inorganic Chemistry, Technische Universität Dresden, Bergstraße 66, 01062 Dresden, Germany
| | - Thomas Fallon
- Centre for Advanced Nanomaterials and Department of Chemistry, The University of Adelaide, North Terrace, Adelaide, South Australia 5000, Australia
| | - Haijie Cao
- Institute of Materials for Energy and Environment, College of Materials Science and Engineering, Qingdao University, Qingdao 266071, PR China
| | - Maoxia He
- Environment Research Institute, Shandong University, Qingdao 266237, PR China
| | - Xiu Song Zhao
- Institute of Materials for Energy and Environment, College of Materials Science and Engineering, Qingdao University, Qingdao 266071, PR China.,School of Chemical Engineering, The University of Queensland, St Lucia,Brisbane 4072, Australia
| | - Stefano Agnoli
- Dipartimento di Scienze Chimiche, Università di Padova, Via Marzolo 1, 35131 Padova, Italy
| | - Christopher J Sumby
- Centre for Advanced Nanomaterials and Department of Chemistry, The University of Adelaide, North Terrace, Adelaide, South Australia 5000, Australia
| | - Christian J Doonan
- Centre for Advanced Nanomaterials and Department of Chemistry, The University of Adelaide, North Terrace, Adelaide, South Australia 5000, Australia
| |
Collapse
|
8
|
Martínez-Martínez AJ, Royle CG, Furfari SK, Suriye K, Weller AS. Solid-State Molecular Organometallic Catalysis in Gas/Solid Flow (Flow-SMOM) as Demonstrated by Efficient Room Temperature and Pressure 1-Butene Isomerization. ACS Catal 2020; 10:1984-1992. [PMID: 32296595 PMCID: PMC7147255 DOI: 10.1021/acscatal.9b03727] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Revised: 01/05/2020] [Indexed: 02/06/2023]
Abstract
![]()
The
use of solid–state molecular organometallic chemistry
(SMOM–chem) to promote the efficient double bond isomerization
of 1-butene to 2-butenes under flow–reactor conditions is reported.
Single crystalline catalysts based upon the σ-alkane complexes
[Rh(R2PCH2CH2PR2)(η2η2-NBA)][BArF4] (R
= Cy, tBu; NBA = norbornane; ArF = 3,5-(CF3)2C6H3) are prepared by hydrogenation
of a norbornadiene precursor. For the tBu-substituted system
this results in the loss of long-range order, which can be re-established
by addition of 1-butene to the material to form a mixture of [Rh(tBu2PCH2CH2PtBu2)(cis-2-butene)][BArF4] and [Rh(tBu2PCH2CH2PtBu2)(1-butene)][BArF4], in an order/disorder/order phase change. Deployment under flow-reactor
conditions results in very different on-stream stabilities. With R
= Cy rapid deactivation (3 h) to the butadiene complex occurs, [Rh(Cy2PCH2CH2PCy2)(butadiene)][BArF4], which can be reactivated by simple addition
of H2. While the equivalent butadiene complex does not
form with R = tBu at 298 K and on-stream conversion
is retained up to 90 h, deactivation is suggested to occur via loss
of crystallinity of the SMOM catalyst. Both systems operate under
the industrially relevant conditions of an isobutene co-feed. cis:trans
selectivites for 2-butene are biased in favor of cis for the tBu system and are more leveled for Cy.
Collapse
Affiliation(s)
| | - Cameron G. Royle
- Department of Chemistry, Chemistry Research Laboratories, University of Oxford, Oxford OX1 3TA, United Kingdom
- Department of Chemistry, University of York, Heslington, York, YO10 5DD, United Kingsdom
| | - Samantha K. Furfari
- Department of Chemistry, Chemistry Research Laboratories, University of Oxford, Oxford OX1 3TA, United Kingdom
- Department of Chemistry, University of York, Heslington, York, YO10 5DD, United Kingsdom
| | - Kongkiat Suriye
- SCG Chemicals, 1 Siam Cement Road, Bangsue, Bangkok 10800, Thailand
| | - Andrew S. Weller
- Department of Chemistry, Chemistry Research Laboratories, University of Oxford, Oxford OX1 3TA, United Kingdom
- Department of Chemistry, University of York, Heslington, York, YO10 5DD, United Kingsdom
| |
Collapse
|
9
|
Martínez-Martínez AJ, Tegner BE, McKay AI, Bukvic AJ, Rees NH, Tizzard GJ, Coles SJ, Warren MR, Macgregor SA, Weller AS. Modulation of σ-Alkane Interactions in [Rh(L 2)(alkane)] + Solid-State Molecular Organometallic (SMOM) Systems by Variation of the Chelating Phosphine and Alkane: Access to η 2,η 2-σ-Alkane Rh(I), η 1-σ-Alkane Rh(III) Complexes, and Alkane Encapsulation. J Am Chem Soc 2018; 140:14958-14970. [PMID: 30351014 DOI: 10.1021/jacs.8b09364] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Solid/gas single-crystal to single-crystal (SC-SC) hydrogenation of appropriate diene precursors forms the corresponding σ-alkane complexes [Rh(Cy2P(CH2) nPCy2)(L)][BArF4] ( n = 3, 4) and [ RhH(Cy2P(CH2)2( CH)(CH2)2PCy2)(L)][BArF4] ( n = 5, L = norbornane, NBA; cyclooctane, COA). Their structures, as determined by single-crystal X-ray diffraction, have cations exhibiting Rh···H-C σ-interactions which are modulated by both the chelating ligand and the identity of the alkane, while all sit in an octahedral anion microenvironment. These range from chelating η2,η2 Rh···H-C (e.g., [Rh(Cy2P(CH2) nPCy2)(η2η2-NBA)][BArF4], n = 3 and 4), through to more weakly bound η1 Rh···H-C in which C-H activation of the chelate backbone has also occurred (e.g., [ RhH(Cy2P(CH2)2( CH)(CH2)2PCy2)(η1-COA)][BArF4]) and ultimately to systems where the alkane is not ligated with the metal center, but sits encapsulated in the supporting anion microenvironment, [Rh(Cy2P(CH2)3PCy2)][COA⊂BArF4], in which the metal center instead forms two intramolecular agostic η1 Rh···H-C interactions with the phosphine cyclohexyl groups. CH2Cl2 adducts formed by displacement of the η1-alkanes in solution ( n = 5; L = NBA, COA), [ RhH(Cy2P(CH2)2( CH)(CH2)2PCy2)(κ1-ClCH2Cl)][BArF4], are characterized crystallographically. Analyses via periodic DFT, QTAIM, NBO, and NCI calculations, alongside variable temperature solid-state NMR spectroscopy, provide snapshots marking the onset of Rh···alkane interactions along a C-H activation trajectory. These are negligible in [Rh(Cy2P(CH2)3PCy2)][COA⊂BArF4]; in [ RhH(Cy2P(CH2)2( CH)(CH2)2PCy2)(η1-COA)][BArF4], σC-H → Rh σ-donation is supported by Rh → σ*C-H "pregostic" donation, and in [Rh(Cy2P(CH2) nPCy2)(η2η2-NBA)][BArF4] ( n = 2-4), σ-donation dominates, supported by classical Rh(dπ) → σ*C-H π-back-donation. Dispersive interactions with the [BArF4]- anions and Cy substituents further stabilize the alkanes within the binding pocket.
Collapse
Affiliation(s)
| | - Bengt E Tegner
- Institute of Chemical Sciences , Heriot-Watt University , Edinburgh EH14 4AS , United Kingdom
| | - Alasdair I McKay
- Chemistry Research Laboratories , University of Oxford , Oxford OX1 3TA , United Kingdom
| | - Alexander J Bukvic
- Chemistry Research Laboratories , University of Oxford , Oxford OX1 3TA , United Kingdom
| | - Nicholas H Rees
- Chemistry Research Laboratories , University of Oxford , Oxford OX1 3TA , United Kingdom
| | - Graham J Tizzard
- UK National Crystallography Service, Chemistry, Faculty of Natural and Environmental Sciences , University of Southampton , Southampton SO17 1BJ , United Kingdom
| | - Simon J Coles
- UK National Crystallography Service, Chemistry, Faculty of Natural and Environmental Sciences , University of Southampton , Southampton SO17 1BJ , United Kingdom
| | - Mark R Warren
- Harwell Science and Innovation Campus, Diamond Light Source Ltd. , Didcot OX11 0DE , United Kingdom
| | - Stuart A Macgregor
- Institute of Chemical Sciences , Heriot-Watt University , Edinburgh EH14 4AS , United Kingdom
| | - Andrew S Weller
- Chemistry Research Laboratories , University of Oxford , Oxford OX1 3TA , United Kingdom
| |
Collapse
|