Co-reporter:Andrew J. Peel;Ryan Ackroyd
Chemical Science (2010-Present) 2017 vol. 8(Issue 7) pp:4904-4916
Publication Date(Web):2017/06/26
DOI:10.1039/C7SC01423F
New reagents have been sought for directed ortho cupration in which the use of cyanide reagents is eliminated. CuOCN reacts with excess TMPLi (TMP = 2,2,6,6-tetramethylpiperidide) in the presence of limited donor solvent to give crystals that are best represented as (TMP)2Cu0.1Li0.9(OCN)Li2(THF) 8, whereby both Lipshutz-type lithiocuprate (TMP)2Cu(OCN)Li2(THF) 8a and trinuclear (TMP)2(OCN)Li3(THF) 8b are expressed. Treatment of a hydrocarbon solution of TMP2CuLi 9a with LiOCN and THF gives pure 8a. Meanwhile, formation of 8b is systematized by reacting (TMPH2)OCN 10 with TMPH and nBuLi to give (TMP)2(OCN)Li3(THF)211. Important to the attribution of lower/higher order bonding in lithiocuprate chemistry is the observation that in crystalline 8, amide-bridging Cu and Li demonstrate clear preferences for di- and tricoordination, respectively. A large excess of Lewis base gives an 8-membered metallacycle that retains metal disorder and analyses as (TMP)2Cu1.35Li0.659 in the solid state. NMR spectroscopy identifies 9 as a mixture of (TMP)2CuLi 9a and other copper-rich species. Crystals from which the structure of 8 was obtained dissolve to yield evidence for 8b coexisting in solution with in situ-generated 9a, 11 and a kinetic variant on 9a (i-9a), that is best viewed as an agglomerate of TMPLi and TMPCu. Moving to the use of DALi (DA = diisopropylamide), (DA)2Cu0.09Li0.91(Br)Li2(TMEDA)212 (TMEDA = N,N,N′,N′-tetremethylethylenediamine) is isolated, wherein (DA)2Cu(Br)Li2(TMEDA)212a exhibits lower-order Cu coordination. The preparation of (DA)2Li(Br)Li2(TMEDA)212b was systematized using (DAH2)Br, DAH and nBuLi. Lastly, metal disorder is avoided in the 2 : 1 lithium amide : Lipshutz-type monomer adduct (DA)4Cu(OCN)Li4(TMEDA)213.
Co-reporter:Arik Kar, Sumanta Sain, David Rossouw, Benjamin R. Knappett, Swapan Kumar Pradhan and Andrew E. H. Wheatley
Nanoscale 2016 vol. 8(Issue 5) pp:2727-2739
Publication Date(Web):14 Dec 2015
DOI:10.1039/C5NR07036H
Recent studies have shown that SnO2-based nanocomposites offer excellent electrical, optical, and electrochemical properties. In this article, we present the facile and cost-effective fabrication, characterization and testing of a new SnO2–PbS nanocomposite photocatalyst designed to overcome low photocatalytic efficiency brought about by electron–hole recombination and narrow photoresponse range. The structure is fully elucidated by X-ray diffraction (XRD)/Reitveld refinement, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET) surface area analysis, and transmission electron microscopy (TEM). Energy-dispersive X-ray spectroscopy (EDX) spectrum imaging analysis demonstrates the intermixing of SnO2 and PbS to form nanocomposites. A charge separation mechanism is presented that explains how the two semiconductors in junction function synergistically. The efficacy of this new nanocomposite material in the photocatalytic degradation of the toxic dye Rhodamine B under simulated solar irradiation is demonstrated. An apparent quantum yield of 0.217 mol min−1 W−1 is calculated with data revealing good catalyst recyclability and that charge separation in SnO2–PbS leads to significantly enhanced photocatalytic activity in comparison to either SnO2 or PbS.
Co-reporter:Yuna Morioka, Aki Matsuoka, Kellie Binder, Benjamin R. Knappett, Andrew E. H. Wheatley and Hiroshi Naka
Catalysis Science & Technology 2016 vol. 6(Issue 15) pp:5801-5805
Publication Date(Web):24 Jun 2016
DOI:10.1039/C6CY00899B
The selective hydrogenation of aromatic compounds to cyclohexanes was found to be promoted by chitin-supported ruthenium nanoparticles (Ru/chitin) under near-neutral, aqueous conditions without the loss of C–O/C–N linkages at benzylic positions.
Co-reporter:Andrew J. Peel, Madani Hedidi, Ghenia Bentabed-Ababsa, Thierry Roisnel, Florence Mongin and Andrew E. H. Wheatley
Dalton Transactions 2016 vol. 45(Issue 14) pp:6094-6104
Publication Date(Web):04 Nov 2015
DOI:10.1039/C5DT03882K
The new area of lithio(thiocyanato)cuprates has been developed. Using inexpensive, stable and safe CuSCN for their preparation, these complexes revealed Lipshutz-type dimeric motifs with solvent-dependent point group identities; planar, boat-shaped and chair shaped conformers are seen in the solid state. In solution, both Lipshutz-type and Gilman structures are clearly seen. Since the advent in 2007 of directed ortho cupration, effort has gone into understanding the structure-reactivity effects of amide ligand variation in and alkali metal salt abstraction from Lipshutz-type cuprates such as (TMP)2Cu(CN)Li2(THF) 1 (TMP = 2,2,6,6-tetramethylpiperidide). The replacement of CN− with SCN− is investigated presently as a means of improving the safety of lithium cuprates. The synthesis and solid state structural characterization of reference cuprate (TMP)2Cu(CN)Li2(THP) 8 (THP = tetrahydropyran) precedes that of the thiocyanate series (TMP)2Cu(SCN)Li2(L) (L = OEt29, THF 10, THP 11). For each of 9–11, preformed TMPLi was combined with CuSCN (2:1) in the presence of sub-stoichiometric Lewis base (0.5 eq. wrt Li). The avoidance of Lewis basic solvents incurs formation of the unsolvated Gilman cuprate (TMP)2CuLi 12, whilst multidimensional NMR spectroscopy has evidenced the abstraction of LiSCN from 9–11 in hydrocarbon solution and the in situ formation of Gilman reagents. The synthetic utility of 10 is established in the selective deprotometalation of chloropyridine substrates, including effecting transition metal-free homocoupling in 51–69% yield.
Co-reporter:Andrew J. Peel, Jonathan Slaughter, Andrew E.H. Wheatley
Journal of Organometallic Chemistry 2016 Volume 812() pp:259-267
Publication Date(Web):15 June 2016
DOI:10.1016/j.jorganchem.2015.09.038
The 2:1 combination of MPLi (MP = 2-methylpiperidide) with CuBr gives the novel complex [(MP)2CuLi(THF)2]2LiBr 12 and introduces the chiral ligand MP to the evolving field of Directed ortho Cupration reagents. Subsequent syntheses have focused on developing heteroleptic bis(amido) arrangements at Cu, with 1:1 mixtures of two out of MPLi, DMPLi and TMPLi (DMP = 2,6-cis-dimethylpiperidide; TMP = 2,2,6,6-tetramethylpiperidide) being reacted with CuI salts in the presence of THF. Resulting lithiocuprates reveal solid state dimers based on the heteroleptic bis(amido) formulations R2N(TMP)Cu(Br)Li2(THF)2 (R2N = MP 13; R2N = DMP 14). The heteroleptic Gilman lithiocuprate PIP(TMP)CuLi (PIP = piperidide) 15 has also been prepared. In each of 12–15, significant variations in the orientations of the amide ligands can be rationalized in terms of steric effects and, in the case of 15, stabilization of the alkali metal by Me…Li interaction is evidenced.Different amines are used to give new bis(amido)cuprates that adhere to the structural principles of Gilman dimers, Lipshutz-type dimers and adducts between Gilman and Lipshutz-type monomers. The dimers incorporate heteroleptic bis(amido)cuprate monomers in which the differing orientations of the amides can be rationalized sterically and in terms of CH…Li stabilization.Figure optionsDownload full-size imageDownload high-quality image (292 K)Download as PowerPoint slide
Co-reporter:Philip J. Harford, Andrew J. Peel, Floris Chevallier, Ryo Takita, Florence Mongin, Masanobu Uchiyama and Andrew E. H. Wheatley
Dalton Transactions 2014 vol. 43(Issue 38) pp:14181-14203
Publication Date(Web):04 Jun 2014
DOI:10.1039/C4DT01130A
Recent advances in the selective deprotometallation of aromatic reagents using alkali metal cuprates are reported. The ability of these synergic bases to effect deprotonation under the influence of a directing group is explored in the context of achieving new and more efficient organic transformations whilst encouraging greater ancillary group tolerance by the base. Developments in our understanding of the structural chemistry of alkali metal cuprates are reported, with both Gilman cuprates of the type R2CuLi and Lipshutz and related cuprates of the type R2Cu(X)Li2 (X = inorganic anion) elucidated and rationalised in terms of ligand sterics. The generation of new types of cuprate motif are introduced through the development of adducts between different classes of cuprate. The use of DFT methods to interrogate the mechanistic pathways towards deprotonative metallation is described. Theoretical modelling of in situ rearrangements undergone by the cuprate base are discussed, with a view to understanding the relationship between R2CuLi and R2Cu(X)Li2, their interconversion and the implications of this for cuprate reactivity. The advent of a new class of adduct between different cuprate types is developed and interpreted in terms of the options for expelling LiX from R2Cu(X)Li2. Applications in the field of medicinal chemistry and (hetero)arene derivatization are explored.
Co-reporter:Philip J. Harford;Andrew J. Peel;Joseph P. Taylor;Dr. Shinsuke Komagawa; Paul R. Raithby;Thomas P. Robinson;Dr. Masanobu Uchiyama;Dr. Andrew E. H. Wheatley
Chemistry - A European Journal 2014 Volume 20( Issue 14) pp:3908-3912
Publication Date(Web):
DOI:10.1002/chem.201304824
Abstract
TMPLi (TMP=2,2,6,6-tetramethylpiperidide) reacts with CuI salts in the presence of Et2O to give the dimers [{(TMP)2Cu(X)Li2(OEt2)}2] (X=CN, halide). In contrast, the use of DMPLi (DMP=cis-2,6-dimethylpiperidide) gives an unprecedented structural motif; [{(DMP)2CuLi(OEt2)}2LiX] (X=halide). This formulation suggests a hitherto unexplored route to the in situ formation of Gilman-type bases that are of proven reactivity in directed ortho cupration.
Co-reporter:Pavel Abdulkin, Yanina Moglie, Benjamin R. Knappett, David A. Jefferson, Miguel Yus, Francisco Alonso and Andrew E. H. Wheatley
Nanoscale 2013 vol. 5(Issue 1) pp:342-350
Publication Date(Web):05 Nov 2012
DOI:10.1039/C2NR32570E
An array of copper and copper–zinc based nanoparticles (NPs) have been fabricated employing a variety of polymeric capping agents. Analysis by TEM, XRPD and XPS suggests that by manipulating reagent, reductant and solvent conditions it is possible to achieve materials that are mono-/narrow disperse with mean particle sizes in the ≤10 nm regime. Oxidative stability in air is achieved for monometallic NPs using poly(methyl methacrylate) (PMMA) anti-agglomerant in conjunction with a variety of reducing conditions. In contrast, those encapsulated by either poly(1-vinylpyrrolidin-2-one) (PVP) or poly(4-vinylpyridine) (PVPy) rapidly show Cu2O formation, with all data suggesting progressive oxidation from Cu to Cu@Cu2O core–shell structure and finally Cu2O. Bimetallic copper–zinc systems, reveal metal segregation and the formation of Cu2O and ZnO. Catalysts have been screened in the synthesis of 1,2,3-triazoles through multicomponent azide–alkyne 1,3-dipolar cycloaddition. Whereas PMMA- and PVPy-coating results in reduced catalytic activity, those protected by PVP are highly active, with quantitative triazole syntheses achieved at room temperature and with catalyst loadings of 0.03 mol% metal for Cu and CuZn systems prepared using NaH2PO2, N2H4 or NaBH4 reductants.
Co-reporter:Benjamin R. Knappett, Pavel Abdulkin, Emilie Ringe, David A. Jefferson, Sergio Lozano-Perez, T. Cristina Rojas, Asunción Fernández and Andrew E. H. Wheatley
Nanoscale 2013 vol. 5(Issue 13) pp:5765-5772
Publication Date(Web):20 Feb 2013
DOI:10.1039/C3NR33789H
Cobalt nanoparticles were synthesised via the thermal decomposition of Co2(CO)8 and were coated in iron oxide using Fe(CO)5. While previous work focused on the subsequent thermal alloying of these nanoparticles, this study fully elucidates their composition and core@shell structure. State-of-the-art electron microscopy and statistical data processing enabled chemical mapping of individual particles through the acquisition of energy-filtered transmission electron microscopy (EFTEM) images and detailed electron energy loss spectroscopy (EELS) analysis. Multivariate statistical analysis (MSA) has been used to greatly improve the quality of elemental mapping data from core@shell nanoparticles. Results from a combination of spatially resolved microanalysis reveal the shell as Fe3O4 and show that the core is composed of oxidatively stable metallic Co. For the first time, a region of lower atom density between the particle core and shell has been observed and identified as a trapped carbon residue attributable to the organic capping agents present in the initial Co nanoparticle synthesis.
Co-reporter:Francesca A. Stokes, Mark A. Vincent, Ian H. Hillier, Tanya K. Ronson, Alexander Steiner, Andrew E. H. Wheatley, Paul T. Wood and Dominic S. Wright
Dalton Transactions 2013 vol. 42(Issue 38) pp:13923-13930
Publication Date(Web):29 Jul 2013
DOI:10.1039/C3DT51632F
The reactions of dilithium 1,2-diamidobenzene, [1,2-(HN)2C6H4]Li2 (L1111H2222)Li2, and dilithium 1,8-diamidonaphthalene, [1,8-(NH)2C10H6]Li2 (L222H222)Li2, with Cp2Ni and Cp2V have been used to obtain the new complexes (L222H222)2Ni{Li(THF)2}2 (3), (L222H222)3V{Li(THF)2}3 (4) and (L1111H2222)6Ni6·{[(L1111H2222)3(L11H)3Ni6Li(THF)]2−·2[Li(THF)4]+} (5), in which retention or oxidation of the initial metal(II) centre is observed. Whereas 3 and 4 contain one transition metal ion within ion-paired structures, 5 has a complicated co-crystalline composition which contains octahedral Ni6-cages constructed from six square-planar (16e) NiII centres.
Co-reporter:Nada Marquise, Philip J. Harford, Floris Chevallier, Thierry Roisnel, Andrew E.H. Wheatley, Philippe C. Gros, Florence Mongin
Tetrahedron Letters 2013 Volume 54(Issue 24) pp:3154-3157
Publication Date(Web):12 June 2013
DOI:10.1016/j.tetlet.2013.04.020
Crystals of a lithiocuprate prepared from copper(I) chloride and lithium 2,2,6,6-tetramethylpiperidide (2 equiv) were isolated and analyzed by X-ray diffraction as (TMP)2Cu(Cl)Li2·THF. The observation of this species is consistent with its having a role in deprotocupration–aroylation. Phenyl pyridyl ketones, phenyl quinolyl ketones, and phenyl thienyl ketones were prepared in tetrahydrofuran using the lithiocuprate and aroyl chorides as electrophiles. Diaryl ketones bearing a chloro group at the 2 position (of a pyridyl or phenyl group) thus synthesized were next converted through palladium-catalyzed ring closure to polycycles of the 5H-indeno[1,2-b]pyridin-5-one, 11H-indeno[1,2-b]quinolin-11-one, 9H-indeno[2,1-c]pyridin-9-one, and 8H-indeno[2,1-b]thiophen-8-one families.
Co-reporter:Francesca A. Stokes, Lars Kloo, Yaokang Lv, Philip J. Harford, Andrew E. H. Wheatley and Dominic S. Wright
Chemical Communications 2012 vol. 48(Issue 92) pp:11298-11300
Publication Date(Web):21 Aug 2012
DOI:10.1039/C2CC35213C
Reactions of the [1,2-(NH)2C6H4]2− dianion (LH22−) with Cp2MII (M = V, Mn) lead to complete or partial oxidation of the metals (M), giving the VIII compound [(η5-Cp)(LH2)2VV(LH2)]−[Li(THF)4]+ (1) and MnII4MnIII2 oxo cage [Mn6(LH2)6(μ6-O)(THF)4] (2).
Co-reporter:Philip J. Harford, Joanna Haywood, Matthew R. Smith, Benjamin N. Bhawal, Paul R. Raithby, Masanobu Uchiyama and Andrew E. H. Wheatley
Dalton Transactions 2012 vol. 41(Issue 20) pp:6148-6154
Publication Date(Web):12 Apr 2012
DOI:10.1039/C2DT12415G
Reaction of in situ generated lithium phosphides with 0.5 eq. Cu(I) is employed as a means of targeting lithium phosphidocuprates of either Gilman- or Lipshutz-type formulation – e.g., (R2P)2CuLi·n(LiX) (n = 0, 1). For R = Ph, X = CN in toluene followed by thf or R = Ph, X = I in thf/toluene an unexpected product results. [(Ph2P)6Cu4][Li·4thf]21 reveals an ion-separated structure in the solid state, with solvated lithium cations countering the charge on an adamantyl dianion [(Ph2P)6Cu4]2−. Deployment of R = Ph, X = CN in thf affords a novel network based on the dimer of Ph2PCu(CN)Li·2thf 2 with trianions based on 6-membered (PCu)3 rings acting as nodes in the supramolecular array and solvated alkali metal counter-ions completing the linkers. Cy2PLi (Cy = cyclohexyl) has been reacted with CuCN in thf/toluene to yield Gilman-type lithium bis(phosphido)cuprate (Cy2P)2CuLi·2thf 3 by the exclusion of in situ generated LiCN. A polymer is noted in the solid state.
Co-reporter:Karolina Zelga, Michał Leszczyński, Iwona Justyniak, Arkadiusz Kornowicz, Maciej Cabaj, Andrew E. H. Wheatley and Janusz Lewiński
Dalton Transactions 2012 vol. 41(Issue 19) pp:5934-5938
Publication Date(Web):26 Jan 2012
DOI:10.1039/C2DT11959E
An equimolar reaction between ZnEt2 and 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (hppH) results in the formation of EtZn(hpp) (1) which crystallizes as a trinuclear agglomerate with the guanidinate ligands spanning 4-coordinate Zn centers. Exposure of a pre-formed THF solution of 1 to undried air leads to a ZnO-incorporating derivative 14·ZnO, while an analogous experiment with CH2Cl2 as solvent leads to a novel tetranuclear mixed aggregate formulated as [EtOZn(hpp)]2[ClZn(hpp)]2 (2). The composition of 2 indicates that its formation proceeds via a complex multi-step reaction route that involves not only the oxygenation of ZnEt moieties, but also the activation of CH2Cl2, causing the transfer of a chloride anion to the Zn center. Compounds were characterized by 1H NMR spectroscopy and single-crystal X-ray diffraction analysis.
Co-reporter:Francesca A. Stokes, Robert J. Less, Joanna Haywood, Rebecca L. Melen, Richard I. Thompson, Andrew E. H. Wheatley, and Dominic S. Wright, Adam Johannes Johansson and Lars Kloo
Organometallics 2012 Volume 31(Issue 1) pp:23-26
Publication Date(Web):December 19, 2011
DOI:10.1021/om200381p
Rather than achieving bis-deprotonation of the phosphine, reaction of Cp2Mn (Cp = cyclopentadienyl) with t-BuPH2 at room temperature yields monodeprotonation of half of the available phosphine in the product (t-BuPH2)(η5-Cp)Mn{μ-(t-BuPH)}2Mn(Cp)(t-BuPH2) (1). This complex comprises a Mn(II) phosphide and is a dimer in the solid state, containing a Mn2P2 diamond core. Consistent with the observation of a relatively short intermetal distance of 2.8717(4) Å in 1, DFT analysis of the full structure points to a singlet ground state stabilized by a direct Mn–Mn single bond. This is in line with the diamagnetic character of 1 and an 18-electron count at Mn.
Co-reporter:Faysal Benaskar;Dr. Volker Engels;Dr. Evgeny V. Rebrov;Narendra G. Patil;Dr. Jan Meuldijk;Dr. Peter C. Thüne;Dr. Pieter C. M. M. Magusin;Brahim Mezari;Dr. Volker Hessel;Dr. Lumbertus A. Hulshof;Dr. Emiel J. M. Hensen;Dr. Andrew E. H. Wheatley;Dr. Jaap C. Schouten
Chemistry - A European Journal 2012 Volume 18( Issue 6) pp:1800-1810
Publication Date(Web):
DOI:10.1002/chem.201102151
Abstract
New routes for the preparation of highly active TiO2-supported Cu and CuZn catalysts have been developed for CO coupling reactions. Slurries of a titania precursor were dip-coated onto glass beads to obtain either structured mesoporous or non-porous titania thin films. The Cu and CuZn nanoparticles, synthesized using a reduction by solvent method, were deposited onto calcined films to obtain a Cu loading of 2 wt %. The catalysts were characterized by inductively coupled plasma (ICP) spectroscopy, temperature-programmed oxidation/reduction (TPO/TPR) techniques, 63Cu nuclear magnetic resonance (NMR) spectroscopy, X-ray diffraction (XRD), scanning and transmission electron microscopy (S/TEM-EDX) and X-ray photo-electron spectroscopy (XPS). The activity and stability of the catalysts obtained have been studied in the CO Ullmann coupling of 4-chloropyridine and potassium phenolate. The titania-supported nanoparticles retained catalyst activity for up to 12 h. However, catalyst deactivation was observed for longer operation times due to oxidation of the Cu nanoparticles. The oxidation rate could be significantly reduced over the CuZn/TiO2 catalytic films due to the presence of Zn. The 4-phenoxypyridine yield was 64 % on the Cu/nonporous TiO2 at 120 °C. The highest product yield of 84 % was obtained on the Cu/mesoporous TiO2 at 140 °C, corresponding to an initial reaction rate of 104 mmol gcat−1 s−1. The activation energy on the Cu/mesoporous TiO2 catalyst was found to be (144±5) kJ mol−1, which is close to the value obtained for the reaction over unsupported CuZn nanoparticles (123±3 kJ mol−1) and almost twice the value observed over the catalysts deposited onto the non-porous TiO2 support (75±2 kJ mol−1).
Co-reporter:Mark A. Vincent;Dr. Alison CampbellSmith;Dr. Morgan Donnard;Philip J. Harford;Dr. Joanna Haywood; Ian H. Hillier; Jonathan Clayden;Dr. Andrew E. H. Wheatley
Chemistry - A European Journal 2012 Volume 18( Issue 35) pp:11036-11045
Publication Date(Web):
DOI:10.1002/chem.201200734
Abstract
Density functional calculations reveal that, whereas the reaction of 2-propyl-N,N-diisopropylbenzamide (6) with tBuLi in the presence of potentially tridentate donor ligands may result in lateral deprotonation of 6, the behavior of the Lewis base is non-trivial. The ability of N and O donor centers in the co-solvent to resist Li+ coordination is found to be synonymous with interaction of lithium with the formally deprotonated carbanion center. Low-energy structures have been identified whose predicted 1H and 13C NMR spectroscopic shifts are in excellent agreement with experiment. Reaction of 2-isopropyl-N,N-diisopropylbenzamide (5) with tBuLi in the presence of bidentate Lewis base N,N,N′,N′-tetramethylethylenediamine (TMEDA) yields material that is suggested by NMR spectroscopy to be laterally deprotonated and to have the formulation 5-Lil⋅TMEDA. In spite of the tertiary aliphatic group at the 2-position in 5, X-ray crystallography reveals that the crystalline material isolated from the treatment of 5/(−)-sparteine with tBuLi is a lateral lithiate in which amide coordination and solvation by bidentate Lewis base results in the Li+ ion interacting with the deprotonated α-C of the 2-iPr group (2.483(8) Å). The tertiary carbanion center remains essentially flat and the adjacent aromatic system is highly distorted. The use of a chiral co-solvent results in two diastereomeric conformers, and their direct observation in solution suggests that interconversion is slow on the NMR timescale.
Co-reporter:Dr. Shinsuke Komagawa;Dr. Shinya Usui;Dr. Joanna Haywood;Philip J. Harford;Dr. Andrew E. H. Wheatley;Dr. Yotaro Matsumoto;Dr. Keiichi Hirano;Dr. Ryo Takita;Dr. Masanobu Uchiyama
Angewandte Chemie International Edition 2012 Volume 51( Issue 48) pp:12081-12085
Publication Date(Web):
DOI:10.1002/anie.201204923
Co-reporter:Joanna Haywood, Francesca A. Stokes, Robert J. Less, Mary McPartlin, Andrew E. H. Wheatley and Dominic S. Wright
Chemical Communications 2011 vol. 47(Issue 14) pp:4120-4122
Publication Date(Web):01 Mar 2011
DOI:10.1039/C1CC10194C
The reaction of chromocene, Cp2Cr, with dilithiated 2,3-diphenylguanidine [(PhNH)2CNH = L2H3] gives the novel, quadruply-bonded tetraanion [Cr2(L2H)4]4−.
Co-reporter:Alison CampbellSmith;Dr. Morgan Donnard;Dr. Joanna Haywood; Mary McPartlin;Dr. Mark A. Vincent; Ian H. Hillier; Jonathan Clayden;Dr. Andrew E. H. Wheatley
Chemistry - A European Journal 2011 Volume 17( Issue 29) pp:8078-8084
Publication Date(Web):
DOI:10.1002/chem.201100240
Abstract
Reaction of 2-isopropyl-(N,N-diisopropyl)-benzamide 5 with tBuLi in ether results in ortho deprotonation and the formation of a hemisolvate based on a tetranuclear dimer of (5-Lio)2⋅Et2O. The solid-state structure exhibits a dimer core in which the amide oxygen atoms fail to stabilize the metal ions but are instead available for interaction with two metalated monomers that reside peripheral to the core. Reaction of 5 with tBuLi in the presence of the tridentate Lewis base PMDTA (N,N,N′,N′′,N′′-pentamethyldiethylenetriamine) takes a different course. In spite of the tertiary aliphatic group at the 2-position in 5, X-ray crystallography revealed that a remarkable benzylic (lateral) deprotonation had occurred, giving the tertiary benzyllithium 5-Lil⋅PMDTA. The solid-state structure reveals that amide coordination and solvation by PMDTA combine to distance the Li+ ion from the deprotonated α-C of the 2-iPr group (3.859(4) Å), thus giving an essentially flat tertiary carbanion and a highly distorted aromatic system. DFT analysis suggests that the metal ion resides closer to the carbanion center in solution. In line with this, the same (benzylic) deprotonation is noted if the reaction is attempted in the presence of tridentate diglyme, with X-ray crystallography revealing that the metal is now closer to the tertiary carbanion (2.497(4) Å). Electrophilic quenches of lithiated 5 have allowed, for the first time, the formation of quaternary benzylic substituents by lateral lithiation.
Co-reporter:Dr. Katia Snégaroff;Tan Tai Nguyen;Nada Marquise;Dr. Yury S. Halauko;Philip J. Harford;Dr. Thierry Roisnel;Dr. Vadim E. Matulis; Oleg A. Ivashkevich;Dr. Floris Chevallier;Dr. Andrew E. H. Wheatley;Dr. Philippe C. Gros; Florence Mongin
Chemistry - A European Journal 2011 Volume 17( Issue 47) pp:13284-13297
Publication Date(Web):
DOI:10.1002/chem.201101993
Abstract
A series of chloro- and bromopyridines have been deprotometalated by using a range of 2,2,6,6-tetramethylpiperidino-based mixed lithium–metal combinations. Whereas lithium–zinc and lithium–cadmium bases afforded different mono- and diiodides after subsequent interception with iodine, complete regioselectivities were observed with the corresponding lithium–copper combination, as demonstrated by subsequent trapping with benzoyl chlorides. The obtained selectivities have been discussed in light of the CH acidities of the substrates, determined both in the gas phase and as a solution in THF by using the DFT B3LYP method.
Co-reporter:Volker Engels, Faysal Benaskar, David A. Jefferson, Brian F. G. Johnson and Andrew E. H. Wheatley
Dalton Transactions 2010 vol. 39(Issue 28) pp:6496-6502
Publication Date(Web):21 Jun 2010
DOI:10.1039/C0DT00134A
A modified polyol-based reduction method in ethylene glycol that incorporates poly(N-vinylpyrrolidone) (PVP, Mav = 10000; 40000; 55000) as polymeric anti-agglomerant alongside a reducing additive (N2H4·H2O, NaBH4, NaH2PO2·H2O) has been employed to investigate the influence of synthetic parameters on the purity, morphology and stability of an array of polymer-coated copper nanoparticles. While data point to ethylene glycol being capable of acting as a reductant in this system, the use of NaH2PO2·H2O as co-reductant in tandem with the presence of PVP (Mav 40000) has rendered nanoparticles with a mean size distribution of 9.6 ± 1.0 nm that exhibit stability towards oxidation for several months. These data allow us to probe fundamentally how oxidatively stable nano-copper might be achieved.
Co-reporter:Volker Engels, Faysal Benaskar, Narendra Patil, Evgeny V. Rebrov, Volker Hessel, Lumbertus A. Hulshof, David A. Jefferson, Jef A. J. M. Vekemans, Saurabh Karwal, Jaap C. Schouten and Andrew E. H. Wheatley
Organic Process Research & Development 2010 Volume 14(Issue 3) pp:644-649
Publication Date(Web):March 11, 2010
DOI:10.1021/op9003423
We report the first liquid−liquid Ullmann etherification process mediated not only by oxidatively stable Cu but also by CuZn and CuSn nanoparticle catalysts in conjunction with microwave heating that also avoids the use of solid and expensive bases. Conditions have led to improved turnovers and excellent yields in heteroaromatic Ullmann-type coupling reactions. Further enhancement is achieved upon the addition of 18-crown-6 as a kinetic promoter.
Co-reporter:Faysal Benaskar, Volker Engels, Narendra Patil, Evgeny V. Rebrov, Jan Meuldijk, Volker Hessel, Lumbertus A. Hulshof, David A. Jefferson, Jaap. C. Schouten, Andrew E.H. Wheatley
Tetrahedron Letters 2010 Volume 51(Issue 44) pp:5849
Publication Date(Web):3 November 2010
DOI:10.1016/j.tetlet.2010.09.001
Co-reporter:Faysal Benaskar, Volker Engels, Narendra Patil, Evgeny V. Rebrov, Jan Meuldijk, Volker Hessel, Lumbertus A. Hulshof, David A. Jefferson, Jaap. C. Schouten, Andrew E.H. Wheatley
Tetrahedron Letters 2010 Volume 51(Issue 2) pp:248-251
Publication Date(Web):13 January 2010
DOI:10.1016/j.tetlet.2009.10.126
The action of nanoparticulate copper catalysts with a mean particle size of 10 nm in the Ullmann ether synthesis is reported using multimode microwave heating and employing stable chloropyridine salts and unactivated phenol, with stabilized copper nanoparticles outperforming other copper catalysts in terms of stability and reusability.The action of nanoparticulate copper catalysts with a mean particle size of 10 nm in the Ullmann ether synthesis is reported using multimode microwave heating and employing stable chloropyridine salts and unactivated phenol, with stabilized copper nanoparticles outperforming other copper catalysts in terms of stability and reusability.
Co-reporter:Volker Engels;Aron Rachamim;Sharvari H Dalal
Nanoscale Research Letters 2010 Volume 5( Issue 5) pp:
Publication Date(Web):2010 May
DOI:10.1007/s11671-010-9567-4
ZnO nanowires have been grown by chemical vapour deposition (CVD) using PdZn bimetallic nanoparticles to catalyse the process. Nanocatalyst particles with mean particle diameters of 2.6 ± 0.3 nm were shown to catalyse the growth process, displaying activities that compare well with those reported for sputtered systems. Since nanowire diameters are linked to catalyst morphology, the size-control we are able to exhibit during particle preparation represents an advantage over existing approaches in terms of controlling nanowire dimensions, which is necessary in order to utilize the nanowires for catalytic or electrical applications.(See supplementary material 1)
Co-reporter:Joanna Haywood
European Journal of Inorganic Chemistry 2009 Volume 2009( Issue 33) pp:5010-5016
Publication Date(Web):
DOI:10.1002/ejic.200900756
Abstract
The recent demonstration that hydride translocation involving alkali metal boron monohydrides can be utilised to trap hydride in metal clusters has led to investigation of the alkali metal salts of triethylborohydride, [Et3BH]–. Treatment of Et3BHM (M = Li, Na, K) with the polydentate donors (L) N,N,N′,N′-tetramethylethylenediamine (TMEDA) and N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA) is reported. For M = Li, L = TMEDA ion separation is noted, with the metal ion encapsulated by two donor ligands. In contrast, for M = Na, K the TMEDA-solvates reveal hydride-bridged centro-symmetric dimers based on M2H2-metallocyclic cores. X-ray diffraction reveals mean Na–H and K–H distances of 2.29 and 2.55 Å, respectively. For M = K, the PMDETA-solvate is also reported, with the hydride-bridged dimer motif being retained, with an expanded mean metal–hydride distance of 2.67 Å. Solution data and 1JBH coupling constants are reported in both polar and non-polar solvents.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Co-reporter:Joanna Haywood, James V. Morey and Andrew E. H. Wheatley, Ching-Yuan Liu, Shuji Yasuike and Jyoji Kurita, Masanobu Uchiyama, Paul R. Raithby
Organometallics 2009 Volume 28(Issue 1) pp:38-41
Publication Date(Web):December 11, 2008
DOI:10.1021/om801101u
CuCN reacts with RLi and TMPLi (TMP = 2,2,6,6-tetramethylpiperidide) to give Gilman-type cuprates R(TMP)CuLi·nL (R = Ph, n = 3, L = THF 2; R = Me, n = 1, L = TMEDA 3). 3 and 3·LiCN have been tested in directed ortho cupration with data suggesting enhanced efficiency for Lipshutz-type 3·LiCN; competition between Lipshutz- and Gilman-type formulations is rationalized by DFT methods.
Co-reporter:Joanna Haywood and Andrew E. H. Wheatley
Dalton Transactions 2008 (Issue 26) pp:3378-3397
Publication Date(Web):06 Feb 2008
DOI:10.1039/B717563A
The sequential treatment of group 12 and 13 Lewis acids with alkali-metal organometallics is well established to yield so-called ‘'ate’ complexes, whereby the Lewis-acid metal undergoes nucleophilic attack to give an anion, at least one group 1 metal acting to counter this charge. However, an alternative, less well recognised, reaction pathway involves the Lewis acid abstracting hydride from the organolithium reagent via a β-elimination mechanism. It has recently been shown that in the presence of N,N′-bidentate ligands this chemistry can be harnessed to yield a new type of molecular main-group metal cluster in which the abstracted LiH is effectively trapped, with the hydride ion occupying an interstitial site in the cluster core. Discussion focuses on the development of this field, detailing advances in our understanding of the roles of Lewis acid, organolithium, and amine substrates in the syntheses of these compounds. Structure-types are discussed, as are efforts to manipulate cluster geometry and composition as well as hydride-coordination. Embryonic mechanistic studies are reported, as well as attempts to generate hydride-encapsulation clusters under catalytic control.
Co-reporter:Cecilia Fernández-Cortabitarte;Felipe García;James V. Morey;Mary McPartlin ;Sanjay Singh Dr.;Andrew E. H. Wheatley Dr.;Dominic S. Wright Dr.
Angewandte Chemie International Edition 2007 Volume 46(Issue 28) pp:
Publication Date(Web):5 JUN 2007
DOI:10.1002/anie.200700925
Breaking up: The first triple-decker sandwich anion [(η5-Cp)Li(η5-Cp)Li(η5-Cp)]− of lithocene (Cp=C5H5) (observed in the charge-separated complex [(L)Li(μ-Cp)Li(μ-Cp)Li(L)]+[(η5-Cp)Li(η5-Cp)Li(η5-Cp)]−) is formed in the reaction of [Cp2V] with hppLi (hppH=1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine). The VV-bonded complex [V2(hpp)4] (L) effectively acts as a ligand to intercept the polymeric structure of [CpLi]∞ (see scheme).
Co-reporter:Cecilia Fernández-Cortabitarte;Felipe García;James V. Morey;Mary McPartlin ;Sanjay Singh Dr.;Andrew E. H. Wheatley Dr.;Dominic S. Wright Dr.
Angewandte Chemie 2007 Volume 119(Issue 28) pp:
Publication Date(Web):5 JUN 2007
DOI:10.1002/ange.200700925
Aufbruch-Stimmung: Das erste Tripeldecker-Sandwichanion [(η5-Cp)Li(η5-Cp)Li(η5-Cp)]− von Lithocen (Cp=C5H5) entsteht bei der Reaktion von [Cp2V] mit hppLi (hppH=1,3,4,6,7,8-Hexahydro-2H-pyrimido[1,2-a]pyrimidin). Der VV-Komplex [V2(hpp)4] (L) bricht als Ligand effektiv die polymere Struktur von [CpLi]∞ auf (siehe Schema).
Co-reporter:Sally R. Boss, Martyn P. Coles, Vicki Eyre-Brook, Felipe García, Robert Haigh, Peter B. Hitchcock, Mary McPartlin, James V. Morey, Hiroshi Naka, Paul R. Raithby, Hazel A. Sparkes, Christopher W. Tate and Andrew E. H. Wheatley
Dalton Transactions 2006 (Issue 47) pp:5574-5582
Publication Date(Web):18 Oct 2006
DOI:10.1039/B612782G
The sequential treatment of Lewis acids with N,N′-bidentate ligands and thereafter with ButLi has afforded a series of hydride-encapsulating alkali metal polyhedra. While the use of Me3Al in conjunction with Ph(2-C5H4N)NH gives Ph(2-C5H4N)NAlMe21 and this reacts with MeLi in thf to yield the simple ’ate complex Ph(2-C5H4N)NAlMe3Li·thf 3, the employment of an organolithium substrate capable of β-hydride elimination redirects the reaction significantly. Whereas the use of ButLi has previously yielded a main group interstitial hydride in which H− exhibits µ6-coordination, it is shown here that variability in the coordination sphere of the encapsulated hydride may be induced by manipulation of the organic ligand. Reaction of (c-C6H11)(2-C5H4N)NH with Me3Al/ButLi yields [{(c-C6H11)(2-C5H4N)N}6HLi8]+[(But2AlMe2)2Li]−6, which is best viewed as incorporating only linear di-coordination of the hydride ion. The guanidine 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (hppH) in conjunction with Me2Zn/ButLi yields the µ8-hydride [(hpp)6HLi8]+[But3Zn]−·0.5PhMe 7. Formation of the µ8-hydride [(hpp)6HLi8]+[ButBEt3]−8 is revealed by employment of the system Et3B/ButLi. A new and potentially versatile route to interstitial hydrides of this class is revealed by synthesis of the mixed borohydride–lithium hydride species [(hpp)6HLi8]+[Et3BH]−10 and [(hpp)6HLi8]+[(Et3B)2H]−12 through the direct combination of hppLi with Et3BHLi.
Co-reporter:Samuel J. Birch, Sally R. Boss, Sarah C. Cole, Martyn P. Coles, Robert Haigh, Peter B. Hitchcock and Andrew E. H. Wheatley
Dalton Transactions 2004 (Issue 21) pp:3568-3574
Publication Date(Web):27 Sep 2004
DOI:10.1039/B410945G
Dimethylzinc reacts with an excess of N-2-pyridylaniline 6 to give the homoleptic species, Zn[PhN(2-C5H4N)]28. Single crystal X-ray diffraction reveals a solid-state dimer based on an 8-membered (NCNZn)2 core motif. Zn[CyN(2-C5H4N)]Me (Cy =
c-C6H11)
10, prepared by the combination of ZnMe2 with the corresponding cyclohexyl-substituted pyridylamine, is also dimeric in the solid state but reveals a central (ZnN)2 metallacycle. Employment of (p-Tol)NH(2-C5H4N)
(p-Tol = 4-MeC6H4)
11 yielded the tris(zinc) adduct Zn3[(p-Tol)N(2-C5H4N)]4Me212, which incorporates a central chiral molecule of ‘Zn[(p-Tol)N(2-C5H4N)]2’
12a, that bridges two ‘Zn[(p-Tol)N(2-C5H4N)]Me’
12b units. A similar trimetallic structure is noted when the pyridylaniline substrate 11 is replaced with the bicyclic guanidine 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (hppH), affording Zn3(hpp)4Me213. Spectroscopic studies point to retention of the solid-state structure of 13 in hydrocarbon solution. Reaction of 13 with dimesityl borinic acid, Mes2BOH (Mes = mesityl), affords Zn3(hpp)4(OBMes2)214 in which the trimetallic core is retained. This reactivity is in contrast to the closely related reaction of dimeric Zn[Me2NC{NiPr}2]Me 15 with Mes2BOH, which yielded Zn[Me2NC{NiPr}2][OBMes2]·Me2NC{NiPr}{NHiPr}
16 as a result of protonation at the guanidine ligand in addition to the Zn–Me bond.
Co-reporter:David R. Armstrong Dr.;Sally R. Boss;Jonathan Clayden ;Robert Haigh Dr.;Basel A. Kirmani;David J. Linton Dr.;Paul Schooler Dr. Dr.
Angewandte Chemie International Edition 2004 Volume 43(Issue 16) pp:
Publication Date(Web):6 APR 2004
DOI:10.1002/anie.200353324
Solvent effects control the regioselectivity with which tert-butyllithium deprotonates 2-ethyl-N,N-diisopropyl-1-benzamide. From THF an ortho-lithiated dimer is isolated but from N,N,N′,N′′,N′′pentamethyldiethylenetriamine (pmdeta) a laterally lithiated monomer is obtained (see scheme). Density functional theory (DFT) calculations point to the importance of Lewis base solvation and aggregation state in determining the chemoselectivity.
Co-reporter:David R. Armstrong Dr.;Sally R. Boss;Jonathan Clayden ;Robert Haigh Dr.;Basel A. Kirmani;David J. Linton Dr.;Paul Schooler Dr. Dr.
Angewandte Chemie 2004 Volume 116(Issue 16) pp:
Publication Date(Web):6 APR 2004
DOI:10.1002/ange.200353324
Lösungsmitteleffekte bestimmen die Regioselektivität der Deprotonierung von 2-Ethyl-N,N-diisopropyl-1-benzamid durch tert-Butyllithium. Aus THF wird ein ortho-lithiiertes Dimer, aus N,N,N′,N′,N′-Pentamethyldiethylentriamin (pmdeta) ein lateral lithiiertes Monomer isoliert (siehe Schema). DFT-Rechnungen zeigen die Bedeutung der Solvatation durch die Lewis-Base für die Chemoselektivität auf.
Co-reporter:Andrew E. H. Wheatley
European Journal of Inorganic Chemistry 2003 Volume 2003(Issue 18) pp:
Publication Date(Web):12 SEP 2003
DOI:10.1002/ejic.200300317
Directed metallation using organolithium bases is one of the best ways of regiospecifically elaborating aromatic systems and their substituents. For benzenoid arenes, deprotonation occurs at the ortho, lateral or peri positions. The reasons for each type of reaction will be considered in the context of the propensities of different directing groups for complex formation with the incoming organolithium base, acidification of the reactive site(s) and post-reaction stabilisation of the metal ion(s). Discussion will concentrate on structural investigations, for the most part by single-crystal X-ray diffraction and/or by multinuclear NMR spectroscopy. Theoretical studies will also be incorporated. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Co-reporter:David R. Armstrong;Robert P. Davies;Robert Haigh;Mark A. Hendy;Paul R. Raithby;Ronald Snaith;Andrew E. H. Wheatley
European Journal of Inorganic Chemistry 2003 Volume 2003(Issue 18) pp:
Publication Date(Web):12 SEP 2003
DOI:10.1002/ejic.200300244
(Trimethylsilyl)diazomethane (1-H) reacts with nBuLi in THF at elevated temperature to afford (previously reported) 1-Li·3/2THF. However, reaction in hexane/TMEDA at low temperature affords instead the N-lithiate Me3SiCNNLi·TMEDA (9), which is a novel “open” pseudo-cubic tetramer in the solid state. Variable-temperature NMR spectroscopy suggests that N-metallated 9, apparently the kinetic product of the reaction, irreversibly rearranges at high temperature in solution to give the thermodynamically preferred C-lithiated isomer. These observations, supported by DFT calculations, influence our understanding of the reactivity of lithiated diazomethanes towards aryl isothiocyanates, suggesting as they do that previously observed product selectivity in these reactions is critically dependent on temperature control exercised during the process. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Co-reporter:Robert P. Davies;M. Giovanna Martinelli;Andrew E. H. Wheatley;Andrew J. P. White;David J. Williams
European Journal of Inorganic Chemistry 2003 Volume 2003(Issue 18) pp:
Publication Date(Web):12 SEP 2003
DOI:10.1002/ejic.200300234
Lithium tellurophosphinite [Ph2PTe][Li(TMEDA)1.33(THF)1.33] (4), ditellurophosphinate, [Ph2PTe2][Li(THF)3.5(TMEDA)0.25] (5), and selenotellurophosphinate [Ph2P(Se)Te][Li(THF)2(TMEDA)] (6) complexes have been prepared from the insertion/oxidation reactions of lithiated secondary phosphanes with elemental chalcogens and characterised by X-ray crystallography. Compounds 4−6 contain no tellurium−lithium bonding interactions in the solid state, instead existing as ion-separated species with THF/TMEDA-solvated lithium cations. Reaction of dilithiated primary phosphanes with more than three equivalents of elemental selenium gives [{(c-C6H11)P(Se)(SeLi)}2·2TMEDA] (7) via a phosphorus-phosphorus coupling reaction. Solid state characterisation of 7 reveals the organo groups in the tetradentate tetraselenohypodisphosphinate ligand to be in an anti conformation to one another and each lithium atom to be coordinated by two selenium atoms, one from each of the diselenophosphinate groups. Multinuclear NMR spectroscopic data are consistent with retention of the solid-state structures of 4−7 in solution. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Co-reporter:Sally R. Boss;Martyn P. Coles Dr.;Robert Haigh Dr.;Peter B. Hitchcock Dr.;Ronald Snaith Dr.
Angewandte Chemie 2003 Volume 115(Issue 48) pp:
Publication Date(Web):10 DEC 2003
DOI:10.1002/ange.200390659
Co-reporter:Sally R. Boss;Martyn P. Coles Dr.;Robert Haigh Dr.;Peter B. Hitchcock Dr.;Ronald Snaith Dr.
Angewandte Chemie 2003 Volume 115(Issue 45) pp:
Publication Date(Web):18 NOV 2003
DOI:10.1002/ange.200351921
Ein Lithiumcluster mit eingeschlossenem Hydridion, [Li8(H)m(hpp)6]n+[X]−n, entsteht als Hauptprodukt bei der Umsetzung des nichtaromatischen Heterocyclus 1,3,4,6,7,8-Hexahydro-2H-pyrimido[1,2-a]pyrimidin (hppH) mit ZnMe2 (m=n=1, X=[ZntBu3]; Kation siehe Bild). Ähnliche Strukturen könnten auch in anderen Polylithium-Architekturen vorliegen. Ersetzt man ZnMe2 durch AlMe3, so erhält man ein Produkt ohne Hydrideinschluss (m=0, n=2, X=[Li(Me2AltBu2)2]).
Co-reporter:Sally R. Boss;Martyn P. Coles Dr.;Robert Haigh Dr.;Peter B. Hitchcock Dr.;Ronald Snaith Dr.
Angewandte Chemie International Edition 2003 Volume 42(Issue 45) pp:
Publication Date(Web):18 NOV 2003
DOI:10.1002/anie.200351921
The reaction of AlMe3or ZnMe2with hppH (hppH=1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine) and then with tBuLi affords [Li8(H)m(hpp)6]n+[X]−n, X=[ZntBu3], m=n=1 (the cation core of which is shown); X=[Li(Me2AltBu2)2], m=0, n=2, as the major product in each case. These data reveal that non-aromatic heterocycle hppH and ZnMe2 can be employed to generate novel hydride-encapsulation main-group-metal clusters, and that related polylithium architectures can also incorporate a central void.
Co-reporter:Sally R. Boss;Martyn P. Coles Dr.;Robert Haigh Dr.;Peter B. Hitchcock Dr.;Ronald Snaith Dr.
Angewandte Chemie International Edition 2003 Volume 42(Issue 48) pp:
Publication Date(Web):10 DEC 2003
DOI:10.1002/anie.200390632
Co-reporter:Robert P. Davies;David J. Linton;Paul Schooler;Ronald Snaith;Andrew E. H. Wheatley
European Journal of Inorganic Chemistry 2001 Volume 2001(Issue 3) pp:
Publication Date(Web):2 FEB 2001
DOI:10.1002/1099-0682(200103)2001:3<619::AID-EJIC619>3.0.CO;2-R
The sequential reaction of PhN(H)C(Ph)NPh (AmH) with AlMe3 and tBuLi leads to the isolation of both the cluster (Li4Am3)+·{Li[(μ-Me)2Al(Me)tBu]2}−(5) and the aluminium tris(amidinate) AlAm3(6). In the solid state, 5 has a polymeric structure based on tetranuclear Li4-cluster cations and lithium bis(aluminate) anions which associate by the formation of weak Li···MeAl bonds.
Co-reporter:Robert P. Davies Dr.;David J. Linton;Paul Schooler Dr.;Ronald Snaith Dr.;Andrew E. H. Wheatley Dr.
Chemistry - A European Journal 2001 Volume 7(Issue 17) pp:
Publication Date(Web):27 JUL 2001
DOI:10.1002/1521-3765(20010903)7:17<3696::AID-CHEM3696>3.0.CO;2-O
The sequential reaction of ZnMe2 with a 2-pyridylamine (HN(2-C5H4N)R, R=Ph: 1; 3,5-Xy (=3,5-xylyl): 2; 2,6-Xy: 3; Bz (=benzyl): 4; Me: 5), tBuLi and thereafter with oxygen affords various lithium zincate species, the solid-state structures of which reveal a diversity of oxo-capture modes. Amine 1 reacts to give both dimeric THF⋅[Li(Me)OZn{N(2-C5H4N)Ph}2] (6), wherein oxygen has inserted into the Zn−C bond of a {MeZn[N(2-C5H4N)Ph]2}− ion, and the trigonal Li2Zn complex, bis(OtBu)-capped (THF⋅Li)2[{(μ3-O)tBu}2Zn{N(2-C5H4N)Ph}2] (7). The structural analogue of 6 (8) results from the employment of 2, while the use of more sterically congested 3 yields a pseudo-cubane dimer [{THF⋅[Li(tBu)OZn(OtBu)Me]}2] (9) notable for the retention of labile Zn−C(Me). Amines 4 and 5 afford the oxo-encapsulation products [(μ4-O)Zn4{(2-C5H4N)NBz}6] (10 b), and [tBu(μ3-O)Li3(μ6-O)Zn3{(2-C5H4N)NMe}6] (11), respectively, with concomitant oxo-insertion into a Li−C interaction resulting in capping of the fac-isomeric (μ6-O)M3M′3 distorted octahedral core of the latter complex by a tert-butoxide group.
Co-reporter:Robert P. Davies, David J. Linton, Ronald Snaith and Andrew E. H. Wheatley
Chemical Communications 2000 (Issue 3) pp:193-194
Publication Date(Web):26 Jan 2000
DOI:10.1039/A909135A
While reaction of a solution of the amidoalane
PhC(O)N(Me)AlMe2 3 with 1 equiv. of ButLi affords the
lithium aluminate PhC(O)N(Me)Al(Me)2(But)Li 4,
deliberate treatment of the reaction mixture with oxygen affords the unique
mixed-anion species {[PhC(O)N(Me)Al(Me)(But)OMe]-
Li·[PhC(O)N(Me)Al(Me)(OBut)OMe]Li}2 5; in
the solid state 5 has a (LiO)4 ladder structure containing
terminal mono-oxygenated aluminate ligands and tripodal bis-oxygenated
aluminate ligands spanning end and central Li+ cations.
Co-reporter:David R. Armstrong;William Clegg;Robert P. Davies;Stephen T. Liddle;David J. Linton;Paul R. Raithby;Ronald Snaith
Angewandte Chemie International Edition 1999 Volume 38(Issue 22) pp:
Publication Date(Web):9 NOV 1999
DOI:10.1002/(SICI)1521-3773(19991115)38:22<3367::AID-ANIE3367>3.0.CO;2-U
Lithium cages containing hydride: The reaction of tBuLi with Me2AlN(2-Pyr)Ph in toluene gave [Li8(H){N(2-Pyr)Ph}6]+[Li(Me2AltBu2)2]−, whose cation is the first molecular main group metal species to contain interstitial hydride (the cluster core is shown in the picture). Treatment of the reaction mixture with THF gave the neutral hydride Li7(H)[N(2-Pyr)Ph]6, which has a capped octahedral (Li+)7 cluster core. 2-Pyr=2-pyridyl.
Co-reporter:Philip J. Harford, Andrew J. Peel, Floris Chevallier, Ryo Takita, Florence Mongin, Masanobu Uchiyama and Andrew E. H. Wheatley
Dalton Transactions 2014 - vol. 43(Issue 38) pp:NaN14203-14203
Publication Date(Web):2014/06/04
DOI:10.1039/C4DT01130A
Recent advances in the selective deprotometallation of aromatic reagents using alkali metal cuprates are reported. The ability of these synergic bases to effect deprotonation under the influence of a directing group is explored in the context of achieving new and more efficient organic transformations whilst encouraging greater ancillary group tolerance by the base. Developments in our understanding of the structural chemistry of alkali metal cuprates are reported, with both Gilman cuprates of the type R2CuLi and Lipshutz and related cuprates of the type R2Cu(X)Li2 (X = inorganic anion) elucidated and rationalised in terms of ligand sterics. The generation of new types of cuprate motif are introduced through the development of adducts between different classes of cuprate. The use of DFT methods to interrogate the mechanistic pathways towards deprotonative metallation is described. Theoretical modelling of in situ rearrangements undergone by the cuprate base are discussed, with a view to understanding the relationship between R2CuLi and R2Cu(X)Li2, their interconversion and the implications of this for cuprate reactivity. The advent of a new class of adduct between different cuprate types is developed and interpreted in terms of the options for expelling LiX from R2Cu(X)Li2. Applications in the field of medicinal chemistry and (hetero)arene derivatization are explored.
Co-reporter:Joanna Haywood, Francesca A. Stokes, Robert J. Less, Mary McPartlin, Andrew E. H. Wheatley and Dominic S. Wright
Chemical Communications 2011 - vol. 47(Issue 14) pp:NaN4122-4122
Publication Date(Web):2011/03/01
DOI:10.1039/C1CC10194C
The reaction of chromocene, Cp2Cr, with dilithiated 2,3-diphenylguanidine [(PhNH)2CNH = L2H3] gives the novel, quadruply-bonded tetraanion [Cr2(L2H)4]4−.
Co-reporter:Francesca A. Stokes, Mark A. Vincent, Ian H. Hillier, Tanya K. Ronson, Alexander Steiner, Andrew E. H. Wheatley, Paul T. Wood and Dominic S. Wright
Dalton Transactions 2013 - vol. 42(Issue 38) pp:NaN13930-13930
Publication Date(Web):2013/07/29
DOI:10.1039/C3DT51632F
The reactions of dilithium 1,2-diamidobenzene, [1,2-(HN)2C6H4]Li2 (L1111H2222)Li2, and dilithium 1,8-diamidonaphthalene, [1,8-(NH)2C10H6]Li2 (L222H222)Li2, with Cp2Ni and Cp2V have been used to obtain the new complexes (L222H222)2Ni{Li(THF)2}2 (3), (L222H222)3V{Li(THF)2}3 (4) and (L1111H2222)6Ni6·{[(L1111H2222)3(L11H)3Ni6Li(THF)]2−·2[Li(THF)4]+} (5), in which retention or oxidation of the initial metal(II) centre is observed. Whereas 3 and 4 contain one transition metal ion within ion-paired structures, 5 has a complicated co-crystalline composition which contains octahedral Ni6-cages constructed from six square-planar (16e) NiII centres.
Co-reporter:Francesca A. Stokes, Lars Kloo, Yaokang Lv, Philip J. Harford, Andrew E. H. Wheatley and Dominic S. Wright
Chemical Communications 2012 - vol. 48(Issue 92) pp:NaN11300-11300
Publication Date(Web):2012/08/21
DOI:10.1039/C2CC35213C
Reactions of the [1,2-(NH)2C6H4]2− dianion (LH22−) with Cp2MII (M = V, Mn) lead to complete or partial oxidation of the metals (M), giving the VIII compound [(η5-Cp)(LH2)2VV(LH2)]−[Li(THF)4]+ (1) and MnII4MnIII2 oxo cage [Mn6(LH2)6(μ6-O)(THF)4] (2).
Co-reporter:Andrew J. Peel, Madani Hedidi, Ghenia Bentabed-Ababsa, Thierry Roisnel, Florence Mongin and Andrew E. H. Wheatley
Dalton Transactions 2016 - vol. 45(Issue 14) pp:NaN6104-6104
Publication Date(Web):2015/11/04
DOI:10.1039/C5DT03882K
The new area of lithio(thiocyanato)cuprates has been developed. Using inexpensive, stable and safe CuSCN for their preparation, these complexes revealed Lipshutz-type dimeric motifs with solvent-dependent point group identities; planar, boat-shaped and chair shaped conformers are seen in the solid state. In solution, both Lipshutz-type and Gilman structures are clearly seen. Since the advent in 2007 of directed ortho cupration, effort has gone into understanding the structure-reactivity effects of amide ligand variation in and alkali metal salt abstraction from Lipshutz-type cuprates such as (TMP)2Cu(CN)Li2(THF) 1 (TMP = 2,2,6,6-tetramethylpiperidide). The replacement of CN− with SCN− is investigated presently as a means of improving the safety of lithium cuprates. The synthesis and solid state structural characterization of reference cuprate (TMP)2Cu(CN)Li2(THP) 8 (THP = tetrahydropyran) precedes that of the thiocyanate series (TMP)2Cu(SCN)Li2(L) (L = OEt29, THF 10, THP 11). For each of 9–11, preformed TMPLi was combined with CuSCN (2:1) in the presence of sub-stoichiometric Lewis base (0.5 eq. wrt Li). The avoidance of Lewis basic solvents incurs formation of the unsolvated Gilman cuprate (TMP)2CuLi 12, whilst multidimensional NMR spectroscopy has evidenced the abstraction of LiSCN from 9–11 in hydrocarbon solution and the in situ formation of Gilman reagents. The synthetic utility of 10 is established in the selective deprotometalation of chloropyridine substrates, including effecting transition metal-free homocoupling in 51–69% yield.
Co-reporter:Volker Engels, Faysal Benaskar, David A. Jefferson, Brian F. G. Johnson and Andrew E. H. Wheatley
Dalton Transactions 2010 - vol. 39(Issue 28) pp:NaN6502-6502
Publication Date(Web):2010/06/21
DOI:10.1039/C0DT00134A
A modified polyol-based reduction method in ethylene glycol that incorporates poly(N-vinylpyrrolidone) (PVP, Mav = 10000; 40000; 55000) as polymeric anti-agglomerant alongside a reducing additive (N2H4·H2O, NaBH4, NaH2PO2·H2O) has been employed to investigate the influence of synthetic parameters on the purity, morphology and stability of an array of polymer-coated copper nanoparticles. While data point to ethylene glycol being capable of acting as a reductant in this system, the use of NaH2PO2·H2O as co-reductant in tandem with the presence of PVP (Mav 40000) has rendered nanoparticles with a mean size distribution of 9.6 ± 1.0 nm that exhibit stability towards oxidation for several months. These data allow us to probe fundamentally how oxidatively stable nano-copper might be achieved.
Co-reporter:Philip J. Harford, Joanna Haywood, Matthew R. Smith, Benjamin N. Bhawal, Paul R. Raithby, Masanobu Uchiyama and Andrew E. H. Wheatley
Dalton Transactions 2012 - vol. 41(Issue 20) pp:NaN6154-6154
Publication Date(Web):2012/04/12
DOI:10.1039/C2DT12415G
Reaction of in situ generated lithium phosphides with 0.5 eq. Cu(I) is employed as a means of targeting lithium phosphidocuprates of either Gilman- or Lipshutz-type formulation – e.g., (R2P)2CuLi·n(LiX) (n = 0, 1). For R = Ph, X = CN in toluene followed by thf or R = Ph, X = I in thf/toluene an unexpected product results. [(Ph2P)6Cu4][Li·4thf]21 reveals an ion-separated structure in the solid state, with solvated lithium cations countering the charge on an adamantyl dianion [(Ph2P)6Cu4]2−. Deployment of R = Ph, X = CN in thf affords a novel network based on the dimer of Ph2PCu(CN)Li·2thf 2 with trianions based on 6-membered (PCu)3 rings acting as nodes in the supramolecular array and solvated alkali metal counter-ions completing the linkers. Cy2PLi (Cy = cyclohexyl) has been reacted with CuCN in thf/toluene to yield Gilman-type lithium bis(phosphido)cuprate (Cy2P)2CuLi·2thf 3 by the exclusion of in situ generated LiCN. A polymer is noted in the solid state.
Co-reporter:Karolina Zelga, Michał Leszczyński, Iwona Justyniak, Arkadiusz Kornowicz, Maciej Cabaj, Andrew E. H. Wheatley and Janusz Lewiński
Dalton Transactions 2012 - vol. 41(Issue 19) pp:NaN5938-5938
Publication Date(Web):2012/01/26
DOI:10.1039/C2DT11959E
An equimolar reaction between ZnEt2 and 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (hppH) results in the formation of EtZn(hpp) (1) which crystallizes as a trinuclear agglomerate with the guanidinate ligands spanning 4-coordinate Zn centers. Exposure of a pre-formed THF solution of 1 to undried air leads to a ZnO-incorporating derivative 14·ZnO, while an analogous experiment with CH2Cl2 as solvent leads to a novel tetranuclear mixed aggregate formulated as [EtOZn(hpp)]2[ClZn(hpp)]2 (2). The composition of 2 indicates that its formation proceeds via a complex multi-step reaction route that involves not only the oxygenation of ZnEt moieties, but also the activation of CH2Cl2, causing the transfer of a chloride anion to the Zn center. Compounds were characterized by 1H NMR spectroscopy and single-crystal X-ray diffraction analysis.
Co-reporter:Andrew J. Peel, Ryan Ackroyd and Andrew E. H. Wheatley
Chemical Science (2010-Present) 2017 - vol. 8(Issue 7) pp:NaN4916-4916
Publication Date(Web):2017/05/04
DOI:10.1039/C7SC01423F
New reagents have been sought for directed ortho cupration in which the use of cyanide reagents is eliminated. CuOCN reacts with excess TMPLi (TMP = 2,2,6,6-tetramethylpiperidide) in the presence of limited donor solvent to give crystals that are best represented as (TMP)2Cu0.1Li0.9(OCN)Li2(THF) 8, whereby both Lipshutz-type lithiocuprate (TMP)2Cu(OCN)Li2(THF) 8a and trinuclear (TMP)2(OCN)Li3(THF) 8b are expressed. Treatment of a hydrocarbon solution of TMP2CuLi 9a with LiOCN and THF gives pure 8a. Meanwhile, formation of 8b is systematized by reacting (TMPH2)OCN 10 with TMPH and nBuLi to give (TMP)2(OCN)Li3(THF)211. Important to the attribution of lower/higher order bonding in lithiocuprate chemistry is the observation that in crystalline 8, amide-bridging Cu and Li demonstrate clear preferences for di- and tricoordination, respectively. A large excess of Lewis base gives an 8-membered metallacycle that retains metal disorder and analyses as (TMP)2Cu1.35Li0.659 in the solid state. NMR spectroscopy identifies 9 as a mixture of (TMP)2CuLi 9a and other copper-rich species. Crystals from which the structure of 8 was obtained dissolve to yield evidence for 8b coexisting in solution with in situ-generated 9a, 11 and a kinetic variant on 9a (i-9a), that is best viewed as an agglomerate of TMPLi and TMPCu. Moving to the use of DALi (DA = diisopropylamide), (DA)2Cu0.09Li0.91(Br)Li2(TMEDA)212 (TMEDA = N,N,N′,N′-tetremethylethylenediamine) is isolated, wherein (DA)2Cu(Br)Li2(TMEDA)212a exhibits lower-order Cu coordination. The preparation of (DA)2Li(Br)Li2(TMEDA)212b was systematized using (DAH2)Br, DAH and nBuLi. Lastly, metal disorder is avoided in the 2:1 lithium amide:Lipshutz-type monomer adduct (DA)4Cu(OCN)Li4(TMEDA)213.
Co-reporter:Yuna Morioka, Aki Matsuoka, Kellie Binder, Benjamin R. Knappett, Andrew E. H. Wheatley and Hiroshi Naka
Catalysis Science & Technology (2011-Present) 2016 - vol. 6(Issue 15) pp:NaN5805-5805
Publication Date(Web):2016/06/24
DOI:10.1039/C6CY00899B
The selective hydrogenation of aromatic compounds to cyclohexanes was found to be promoted by chitin-supported ruthenium nanoparticles (Ru/chitin) under near-neutral, aqueous conditions without the loss of C–O/C–N linkages at benzylic positions.
Co-reporter:Joanna Haywood and Andrew E. H. Wheatley
Dalton Transactions 2008(Issue 26) pp:NaN3397-3397
Publication Date(Web):2008/02/06
DOI:10.1039/B717563A
The sequential treatment of group 12 and 13 Lewis acids with alkali-metal organometallics is well established to yield so-called ‘'ate’ complexes, whereby the Lewis-acid metal undergoes nucleophilic attack to give an anion, at least one group 1 metal acting to counter this charge. However, an alternative, less well recognised, reaction pathway involves the Lewis acid abstracting hydride from the organolithium reagent via a β-elimination mechanism. It has recently been shown that in the presence of N,N′-bidentate ligands this chemistry can be harnessed to yield a new type of molecular main-group metal cluster in which the abstracted LiH is effectively trapped, with the hydride ion occupying an interstitial site in the cluster core. Discussion focuses on the development of this field, detailing advances in our understanding of the roles of Lewis acid, organolithium, and amine substrates in the syntheses of these compounds. Structure-types are discussed, as are efforts to manipulate cluster geometry and composition as well as hydride-coordination. Embryonic mechanistic studies are reported, as well as attempts to generate hydride-encapsulation clusters under catalytic control.
![Pyridine, 2-[3-(2,5-dimethoxyphenyl)-1H-pyrazol-1-yl]-](http://img.cochemist.com/ccimg/200100/200003-00-5.png)
![Pyridine, 2-[3-(2,5-dimethoxyphenyl)-1H-pyrazol-1-yl]-](http://img.cochemist.com/ccimg/200100/200003-00-5_b.png)
![Pyridine, 2,6-bis[3-(2,4,6-trimethylphenyl)-1H-pyrazol-1-yl]-](http://img.cochemist.com/ccimg/214500/214465-03-9.png)
![Pyridine, 2,6-bis[3-(2,4,6-trimethylphenyl)-1H-pyrazol-1-yl]-](http://img.cochemist.com/ccimg/214500/214465-03-9_b.png)
