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7. Rücktitelbild: Isomerisierungsreaktionen in anionischen mesoionischen Carbenboraten und Kontrolle der Eigenschaften und Reaktivität in den entstehenden Co II ‐Komplexen durch agostische Wechselwirkungen (Angew. Chem. 1/2021)

Author

Stubbe, Jessica, primary, Neuman, Nicolás I., additional, McLellan, Ross, additional, Sommer, Michael G., additional, Nößler, Maite, additional, Beerhues, Julia, additional, Mulvey, Robert E., additional, and Sarkar, Biprajit, additional

Published
2020
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8. Back Cover: Isomerization Reactions in Anionic Mesoionic Carbene‐Borates and Control of Properties and Reactivities in the Resulting CoII Complexes through Agostic Interactions (Angew. Chem. Int. Ed. 1/2021)

Author

Stubbe, Jessica, primary, Neuman, Nicolás I., additional, McLellan, Ross, additional, Sommer, Michael G., additional, Nößler, Maite, additional, Beerhues, Julia, additional, Mulvey, Robert E., additional, and Sarkar, Biprajit, additional

Published
2020
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13. LiTMP Trans‐Metal‐Trapping of Fluorinated Aromatic Molecules: A Comparative Study of Aluminum and Gallium Carbanion Traps

Author

McLellan, Ross, Uzelac, Marina, Kennedy, Alan R., Hevia, Eva, and Mulvey, Robert E.

Subjects
gallium, carbanions, Communication, aluminum, Metalation, fluoroaromatic compounds, Communications
Abstract

Fluoroaromatic scaffolds pose a challenge to lithiation due to low stability of lithiated intermediates. Here we apply trans‐metal‐trapping (TMT) to a series of key fluorinated aromatics. In TMT, LiTMP performs the metalation, while an organometallic trap intercepts the emergent carbanion. This study contrasts the trapping abilities of iBu2AlTMP and Ga(CH2SiMe3)3, structurally mapping their TMT reactions and probing relative stabilities of metalated fluoroaromatic intermediates by NMR studies. Results show the installed Al−C(aryl) bonds are more prone to decomposition by benzyne formation and Li‐F liberation, than the Ga−C(aryl) species. The latter are thus better for onward reactivity as demonstrated in cross‐coupling reactions with benzoyl chloride that produce ketones.

Published
2017

14. Equity turbulence, fixed income illiquidity, and portfolio reallocation: the case for synthetic rebalancing

Author

McLellan, Ross, Kinlaw, Will, and Abouzaid, Erin

Subjects
Financial planning -- Management, Financial services industry -- Management, Fixed income securities -- Forecasts and trends, Rate of return -- Forecasts and trends, Stock markets -- Forecasts and trends, Portfolio management, Financial services industry, Return on investment, Stock market, Company business management, Market trend/market analysis, Banking, finance and accounting industries, Business, Economics
Abstract

The catastrophic performance of global equity markets in 2008 has left many asset owners significantly overweight fixed income and underweight equities. As equity markets rally, this imbalance presents significant return [...]

Published
2009

15. The choice of transition provider

Author

McLellan, Ross I.

Subjects
Investment companies -- Services, Portfolio management -- Methods, Banking, finance and accounting industries, Business
Abstract

As recent market reversals drive a reappraisal of asset allocation and risk--and as plan sponsors take a long hard look at their asset managers--the investment management industry is embracing the [...]

Published
2002

16. Diverse outcomes of CO2 fixation using alkali metal amides including formation of a heterobimetallic lithium-sodium carbamato-anhydride via lithium-sodium bis-hexamethyldisilazide

Author

Gauld, Richard M., Kennedy, Alan R., McLellan, Ross, Barker, Jim, Reid, Jacqueline, and Mulvey, Robert E.

Subjects
QD
Abstract

Fixation of CO2 by lithium amides derived from pyrrole and diisopropylamine generates a lithium carbamate polymer and dodecamer respectively. Moving to lithium-sodium hexamethyldisilazide produces a more complicated, intriguing reaction, where unusually the bimetallic composition is maintained in the product but its composition contains both carbamato and anhydride functionalities.

Published
2019

17. A regioselectively 1,1′,3,3′-tetrazincated ferrocene complex displaying core and peripheral reactivity

Author

Honeyman, Gordon W., primary, Armstrong, David R., additional, Clegg, William, additional, Hevia, Eva, additional, Kennedy, Alan R., additional, McLellan, Ross, additional, Orr, Samantha A., additional, Parkinson, John A., additional, Ramsay, Donna L., additional, Robertson, Stuart D., additional, Towie, Stephen, additional, and Mulvey, Robert E., additional

Published
2020
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21. 1-Alkali-metal-2-alkyl-1,2-dihydropyridines : soluble hydride surrogates for catalytic dehydrogenative coupling and hydroboration applications

Author

McLellan, Ross, Kennedy, Alan R., Mulvey, Robert E., Orr, Samantha A., and Robertson, Stuart D.

Subjects
Catalysis | Very Important Paper, main group, Full Paper, catalysis, hydroboration, lithium, dehydrocoupling, QD, Full Papers
Abstract

Equipped with excellent hydrocarbon solubility, the lithium hydride surrogate 1‐lithium‐2‐tert‐butyl‐1,2‐dihydropyridine (1tLi) functions as a precatalyst to convert Me2NH⋅BH3 to [NMe2BH2]2 (89 % conversion) under competitive conditions (2.5 mol %, 60 h, 80 °C, toluene solvent) to that of previously reported LiN(SiMe3)2. Sodium and potassium dihydropyridine congeners produce similar high yields of [NMe2BH2]2 but require longer times. Switching the solvent to pyridine induces a remarkable change in the dehydrocoupling product ratio, with (NMe2)2BH favoured over [NMe2BH2]2 (e.g., 94 %:2 % for 1tLi). Demonstrating its versatility, precatalyst 1tLi was also successful in promoting hydroboration reactions between pinacolborane and a selection of aldehydes and ketones. Most reactions gave near quantitative conversion to the hydroborated products in 15 minutes, though sterically demanding carbonyl substrates require longer times. The mechanisms of these rare examples of Group 1 metal‐catalysed processes are discussed.

Published
2017

25. Structurally Defined Ring‐Opening and Insertion of Pinacolborane into Aluminium‐Nitrogen Bonds of Sterically Demanding Dialkylaluminium Amides.

Author

Pollard, Victoria A., Kennedy, Alan R., McLellan, Ross, Ross, Duncan, Tuttle, Tell, and Mulvey, Robert E.

Subjects
AMIDES, X-ray crystallography, BORONIC esters, HYDROBORATION, DIMERS
Abstract

Dialkylaluminium amides iBu2Al(TMP) and iBu2Al(HMDS) can perform catalytic hydroboration of ketones with pinacolborane to form the expected boronic esters. However, repeating the same reactions stoichiometrically without a ketone leads unexpectedly to ring‐opening of pinacolborane and insertion of its open chain into the Al−N(amido) bond. To date there has been limited knowledge on decomposition pathways of HBpin despite its prominent role in hydroboration chemistry. X‐ray crystallography shows these mixed Al−B products [iBu2Al{OC(Me)2C(Me)2O}B(H)(NR2)]2 (NR2=TMP or HMDS) form dimers with an (AlO)2 core and terminal B−N bonds. Since the bond retention (B−H) and bond breaking (B−O) in these transformations seemed surprising, DFT calculations run using M11/6‐31G(d,p) gave an energy profile consistent with a σ‐bond metathesis mechanism where London dispersion interactions between iBu and (amide) Me groups play an important stabilising role in the final outcome. [ABSTRACT FROM AUTHOR]

Published
2021
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26. Isomerisierungsreaktionen in anionischen mesoionischen Carbenboraten und Kontrolle der Eigenschaften und Reaktivität in den entstehenden CoII‐Komplexen durch agostische Wechselwirkungen.

Author

Stubbe, Jessica, Neuman, Nicolás I., McLellan, Ross, Sommer, Michael G., Nößler, Maite, Beerhues, Julia, Mulvey, Robert E., and Sarkar, Biprajit

Abstract

Copyright of Angewandte Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Published
2021
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27. Isomerization Reactions in Anionic Mesoionic Carbene‐Borates and Control of Properties and Reactivities in the Resulting CoII Complexes through Agostic Interactions.

Author

Stubbe, Jessica, Neuman, Nicolás I., McLellan, Ross, Sommer, Michael G., Nößler, Maite, Beerhues, Julia, Mulvey, Robert E., and Sarkar, Biprajit

Subjects
ISOMERIZATION, ELECTRON paramagnetic resonance spectroscopy, LIGANDS (Chemistry), BORATES, SPINE
Abstract

We present herein anionic borate‐based bi‐mesoionic carbene compounds of the 1,2,3‐triazol‐4‐ylidene type that undergo C−N isomerization reactions. The isomerized compounds are excellent ligands for CoII centers. Strong agostic interactions with the "C−H"‐groups of the cyclohexyl substituents result in an unusual low‐spin square planar CoII complex, which is unreactive towards external substrates. Such agostic interactions are absent in the complex with phenyl substituents on the borate backbone. This complex displays a high‐spin tetrahedral CoII center, which is reactive towards external substrates including dioxygen. To the best of our knowledge, this is also the first investigation of agostic interactions through single‐crystal EPR spectroscopy. We conclusively show here that the structure and properties of these CoII complexes can be strongly influenced through interactions in the secondary coordination sphere. Additionally, we unravel a unique ligand rearrangement for these classes of anionic mesoionic carbene‐based ligands. [ABSTRACT FROM AUTHOR]

Published
2021
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34. Backbone Reactivity of Lithium β‐Diketiminate (NacNac) Complexes with CO2, tBuNCO and iPrNCO.

Author

Gauld, Richard M., McLellan, Ross, Kennedy, Alan R., Barker, Jim, Reid, Jacqueline, and Mulvey, Robert E.

Subjects
*LITHIUM, *ALKALI metals, *LITHIUM compounds, *SPINE, *CARBON dioxide
Abstract

Though alkali metal NacNac (β‐diketiminate) complexes have been utilised in synthesis as NacNac‐transfer agents, studies of them in their own right with small molecules are exceptionally rare. Here, the lithium compound of the common 2,6‐diisopropylphenyl‐β‐methyldiketiminate [NacNac(Dipp, Me)] ligand is investigated with carbon dioxide and isocyanates. In all four cases reaction occurs at the backbone γ‐C atom of the NacNac ligand, which redistributes electronically into a diimine. Insertion of CO2 gives an eight‐atom carboxylate (Li2O4C2) ring at the γ‐C site in a dimer. Insertion of tBuNCO gives a secondary amide at the γ‐C site in a monomer with TMEDA chelating lithium. Double insertion of tBuNCO and (adventitious) oxygen gives a dimer with a (LiO)2 central core involving the latter source. Insertion of less bulky (iPrNCO) gives a dimer with dimerisation through the C=O bonds of the emergent secondary amide function. [ABSTRACT FROM AUTHOR]

Published
2019
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35. Alkali Metal Effects in Trans-Metal-Trapping (TMT): Comparing LiTMP with NaTMP in Cooperative MTMP/Ga(CH2 SiMe3)3 Meta-lation Reactions.

Author

McLellan, Ross, Uzelac, Marina, Bole, Leonie J., Gil-Negrete, Jose María, Armstrong, David R., Kennedy, Alan R., Mulvey, Robert E., and Hevia, Eva

Subjects
*METALATION, *CHEMICAL reactions, *TRAPPING, *ANISOLE, *ORGANIC compounds
Abstract

Stepwise metalation and trapping, so called trans-metal-trapping (TMT), of anisole is studied using LiTMP as base and Ga(CH2 SiMe3)3 as trap. The isolated 'trapped' intermediate is also assessed in C–C bond forming reactions, highlighting the inherent advantages and remaining challenges of this system. The same base trap mixture is found to metallate N–Me bonds of the diamines TMEDA and PMDETA. Comparative studies replacing LiTMP by NaTMP have found significant alkali metal effects on the extent of both base-trap cocomplexation and onward reactivities of TMT products. [ABSTRACT FROM AUTHOR]

Published
2019
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36. Diverse outcomes of CO2 fixation using alkali metal amides including formation of a heterobimetallic lithium–sodium carbamato-anhydride via lithium–sodium bis-hexamethyldisilazide.

Author

Gauld, Richard M., Kennedy, Alan R., McLellan, Ross, Barker, Jim, Reid, Jacqueline, and Mulvey, Robert E.

Subjects
ALKALI metals, LITHIUM amides, CARBAMATES
Abstract

Fixation of CO2 by lithium amides derived from pyrrole and diisopropylamine generates a lithium carbamate polymer and dodecamer respectively. Moving to lithium–sodium hexamethyldisilazide produces a more complicated, intriguing reaction, where unusually the bimetallic composition is maintained in the product but its composition contains both carbamato and anhydride functionalities. [ABSTRACT FROM AUTHOR]

Published
2019
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42. Bis‐Calix[4]arenes: From Ligand Design to the Directed Assembly of a Metal–Organic Trigonal Antiprism

Author

Coletta, Marco, primary, McLellan, Ross, additional, Murphy, Paul, additional, Leube, Bernhard T., additional, Sanz, Sergio, additional, Clowes, Rob, additional, Gagnon, Kevin J., additional, Teat, Simon J., additional, Cooper, Andrew I., additional, Paterson, Martin J., additional, Brechin, Euan K., additional, and Dalgarno, Scott J., additional

Published
2016
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43. Importance of Steric Influences in the Construction of Multicomponent Hybrid Polymetallic Clusters

Author

McLellan, Ross, Palacios, Maria A., Sanz, Sergio, Brechin, Euan K., and Dalgarno, Scott J.

Abstract

The straightforward room temperature synthesis of hybrid polymetallic manganese clusters is investigated, exploiting complementary ligand combinations of p-tert-butylcalix[4]arene and salicylaldoximes. Eight new [MnIII7MnII] clusters have been prepared wherein the simple substitution of alkyl or aryl groups at well-defined positions of the salicylaldoxime scaffold leads to two distinct structure types that, while exhibiting the same general topology, contain the unique MnIIion in different positions. Incorporation of a methyl, ethyl, or isopropyl group at the 3-position of the aromatic skeleton or a phenyl group at the oximic carbon gives structure type A that displays competing weak ferromagnetic and antiferromagnetic interactions. Substitution of a methyl or ethyl group at the oximic carbon atom invokes structure type B, incorporating an additional bulky chloride or nitrate into the metallic core due to the smaller steric imposition and position of the methyl or ethyl group. The distortion of the cluster core is consequently enhanced, switching the magnetic properties and resulting in single-molecule magnet behavior. The presence of tert-butyl groups at the 3- and 5-positions of the salicylaldoxime skeleton leads to a new [MnIV2MnIII2] cluster that is found to be a single-molecule magnet. The bulky tert-butyl group in the 3-position is too large to facilitate Mn8cluster formation, and thus assembly occurs by an alternative pathway. Characteristic bonding modes of the constituent ligands are retained in every case, and the results presented here give insight into the potential of ligand combinations in future studies, highlighting the importance of steric factors in evaluating their relevant compatibilities.

Published
2024
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49. Linked supramolecular building blocks for enhanced cluster formation

Author

McLellan, Ross, Palacios, Maria A., Beavers, Christine M., Teat, Simon J., Piligkos, Stergios, Brechin, Euan K., Dalgarno, Scott J., McLellan, Ross, Palacios, Maria A., Beavers, Christine M., Teat, Simon J., Piligkos, Stergios, Brechin, Euan K., and Dalgarno, Scott J.

Abstract

(Figure Presented). Methylene-bridged calix[4]arenes have emerged as extremely versatile ligand supports in the formation of new polymetallic clusters possessing fascinating magnetic properties. Metal ion binding rules established for this building block allow one to partially rationalise the complex assembly process. The ability to covalently link calix[4]arenes at the methylene bridge provides significantly improved control over the introduction of different metal centres to resulting cluster motifs. Clusters assembled from bis-calix[4]-arenes and transition metal ions or 3d-4 f combinations display characteristic features of the analogous calix[4]arene supported clusters, thereby demonstrating an enhanced and rational approach towards the targeted synthesis of complex and challenging structures.

Published
2015

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