Showing papers by "Alexander J. Blake published in 2012"
TL;DR: This work reports a non-amine-containing porous solid (NOTT-300) in which hydroxyl groups within pores bind CO(2) and SO( 2) selectively, offering the potential for the application of new 'easy-on/easy-off' captured gases that carry fewer economic and environmental penalties.
Abstract: Understanding the mechanism by which porous solids trap harmful gases such as CO(2) and SO(2) is essential for the design of new materials for their selective removal. Materials functionalized with amine groups dominate this field, largely because of their potential to form carbamates through H(2)N(δ(-))···C(δ(+))O(2) interactions, thereby trapping CO(2) covalently. However, the use of these materials is energy-intensive, with significant environmental impact. Here, we report a non-amine-containing porous solid (NOTT-300) in which hydroxyl groups within pores bind CO(2) and SO(2) selectively. In situ powder X-ray diffraction and inelastic neutron scattering studies, combined with modelling, reveal that hydroxyl groups bind CO(2) and SO(2) through the formation of O=C(S)=O(δ(-))···H(δ(+))-O hydrogen bonds, which are reinforced by weak supramolecular interactions with C-H atoms on the aromatic rings of the framework. This offers the potential for the application of new 'easy-on/easy-off' capture systems for CO(2) and SO(2) that carry fewer economic and environmental penalties.
438 citations
TL;DR: Temperature-dependent adsorption/desorption hysteresis in desolvated NOTT-202a that responds selectively to CO(2) is reported, and stepwise filling of pores generated within the observed partially interpenetrated structure has been modelled by grand canonical Monte Carlo simulations.
Abstract: The selective capture of carbon dioxide in porous materials has potential for the storage and purification of fuel and flue gases. However, adsorption capacities under dynamic conditions are often insufficient for practical applications, and strategies to enhance CO2–host selectivity are required. The unique partially interpenetrated metal–organic framework NOTT-202 represents a new class of dynamic material that undergoes pronounced framework phase transition on desolvation. We report temperature-dependent adsorption/desorption hysteresis in desolvated NOTT-202a that responds selectively to CO2. The CO2 isotherm shows three steps in the adsorption profile at 195 K, and stepwise filling of pores generated within the observed partially interpenetrated structure has been modelled by grand canonical Monte Carlo simulations. Adsorption of N2, CH4, O2, Ar and H2 exhibits reversible isotherms without hysteresis under the same conditions, and this allows capture of gases at high pressure, but selectively leaves CO2 trapped in the nanopores at low pressure.
410 citations
TL;DR: The preparation required use of a rigid, bulky ligand framework to keep the reactive uranium nitride group from binding to another molecule nearby, a pathway that has plagued prior attempts to prepare this class of compounds.
Abstract: The terminal uranium nitride linkage is a fundamental target in the study of f-orbital participation in metal-ligand multiple bonding, but it has previously eluded characterization in an isolable molecule. Here, we report the preparation of the terminal uranium(V) nitride complex [UN(TrenTIPS)][Na(12-crown-4)2] (TrenTIPS = {N(CH2CH2NSiPri3)3}3– Pri = CH(CH3)2) by reaction of the uranium(III) complex [U(TrenTIPS)] with sodium azide followed by abstraction and encapsulation of the sodium cation by the polydentate crown ether 12-crown-4. Single-crystal X-ray diffraction reveals a uranium-terminal nitride bond length of 1.825(15) angstroms. The structural assignment is supported by 15N-isotopic labeling, electronic absorption spectroscopy, magnetometry, electronic structure calculations, elemental analyses, and liberation of ammonia following treatment with water.
248 citations
TL;DR: Attempts to prepare uranyl(VI)- and uranium(VI) carbenes utilizing deprotonation and oxidation strategies suggest that as a function of increasing oxidation state of uranium the radial contraction of the valence 5f and 6d orbitals of uranium may outweigh the increased polarizing power of uranium in 6 compared to 5.
Abstract: We report attempts to prepare uranyl(VI)- and uranium(VI) carbenes utilizing deprotonation and oxidation strategies. Treatment of the uranyl(VI)-methanide complex [(BIPMH)UO2Cl(THF)] [1, BIPMH = HC(PPh2NSiMe3)2] with benzyl-sodium did not afford a uranyl(VI)-carbene via deprotonation. Instead, one-electron reduction and isolation of di- and trinuclear [UO2(BIPMH)(μ-Cl)UO(μ-O){BIPMH}] (2) and [UO(μ-O)(BIPMH)(μ3-Cl){UO(μ-O)(BIPMH)}2] (3), respectively, with concomitant elimination of dibenzyl, was observed. Complexes 2 and 3 represent the first examples of organometallic uranyl(V), and 3 is notable for exhibiting rare cation–cation interactions between uranyl(VI) and uranyl(V) groups. In contrast, two-electron oxidation of the uranium(IV)-carbene [(BIPM)UCl3Li(THF)2] (4) by 4-morpholine N-oxide afforded the first uranium(VI)-carbene [(BIPM)UOCl2] (6). Complex 6 exhibits a trans-CUO linkage that represents a [R2C═U═O]2+ analogue of the uranyl ion. Notably, treatment of 4 with other oxidants such as Me3NO, C5...
142 citations
TL;DR: It is shown that under mild conditions a simple triamidoamine uranium(III) complex can reductively homologate CO and be recycled for reuse and the simplicity of this system suggests that catalytic CO functionalization may soon be within reach.
Abstract: Carbon monoxide (CO) is in principle an excellent resource from which to produce industrial hydrocarbon feedstocks as alternatives to crude oil; however, CO has proven remarkably resistant to selective homologation, and the few complexes that can effect this transformation cannot be recycled because liberation of the homologated product destroys the complexes or they are substitutionally inert. Here, we show that under mild conditions a simple triamidoamine uranium(III) complex can reductively homologate CO and be recycled for reuse. Following treatment with organosilyl halides, bis(organosiloxy)acetylenes, which readily convert to furanones, are produced, and this was confirmed by the use of isotopically 13C-labeled CO. The precursor to the triamido uranium(III) complex is formed concomitantly. These findings establish that, under appropriate conditions, uranium(III) can mediate a complete synthetic cycle for the homologation of CO to higher derivatives. This work may prove useful in spurring wider efforts in CO homologation, and the simplicity of this system suggests that catalytic CO functionalization may soon be within reach.
137 citations
TL;DR: In this article, a bifunctional porous metal-organic framework, [Co(HLdc)]·1.5MeOH·dioxane, incorporates both free-standing carboxyl and pyridyl groups within its pores.
Abstract: The unique bifunctional porous metal–organic framework, [Co(HLdc)]·1.5MeOH·dioxane, incorporates both free-standing carboxyl and pyridyl groups within its pores. Gas adsorption measurements on the desolvated framework reveal unusual selective CO2 adsorption over C2H2 and CH4 linked to a framework phase change from a narrow pore (np) to a large pore (lp) form, mediated by CO2 uptake at 195 K. This phase transition has been monitored by in situ powder X-ray diffraction and IR spectroscopy, and modelled by Grand Canonical Monte Carlo simulations revealing that the reversible np to lp transition is linked to the rotation of pyridyl rings acting as flexible “pore gates”.
114 citations
TL;DR: Reaction of H(3)L with Cd(NO(3))( 2)·4H(2)O in DMF at lower temperatures or with C dCl(2), affords coordination polymer frameworks instead of nanospheres.
Abstract: Reaction of H3L with Cd(NO3)2·4H2O in DMF at 150 °C for 3 days affords the metal–organic nanosphere [Cd66(μ3-OH)28(μ3-O)16(μ5-NO3-O,O,O′,O′,O″,O″)12(L)20(μ2-DMF)12⊂(DMF)9]. The cluster is composed of a spherical shell of 66 Cd(II) cations bridged by 28 μ3-hydroxide, 16 μ3-oxo, and five μ5-NO3– anions surrounded by a shell of 20 tripodal capping ligands (L) and 12 DMF ligands. The 66 Cd(II) cations and 12 NO3– anions form a polydeltahedron that has 78 vertices [Cd(II) or NO3–] (V), 228 edges (E), and 152 triangular faces (F), giving it an Euler characteristic (χ) of 2 (χ = V + F – E). Reaction of H3L with Cd(NO3)2·4H2O at lower temperatures or with CdCl2 affords coordination polymer frameworks instead of nanospheres.
61 citations
TL;DR: The microporous metal-organic framework {[Zn2(L)]·(H2O)3}∞ (H4L = 1,2,4,5-tetrakis(4-carboxyphenyl)benzene) has been synthesised using near-critical water (300 °C) as a cleaner alternative to toxic organic solvents as discussed by the authors.
51 citations
TL;DR: The redox processes associated with BODIPY analogues are studied by electrochemical and spectroscopic methods revealing a characteristic profile for the persistent BODipY radical and quenching of fluorescence upon reduction.
33 citations
TL;DR: In this article, a set of novel lithium Schiff base cluster compounds has been synthesised and characterised for the first time and tested as electron injectors in OLED devices, and their electrical, electronic, thermal and optical properties have been investigated and compared with the industry standards LiF and lithium quinolinolate (LiQ).
Abstract: A set of novel lithium Schiff base cluster compounds has been synthesised and characterised for the first time and tested as electron injectors in OLED devices. Their electrical, electronic, thermal and optical properties have been investigated and compared with the industry standards LiF and lithium quinolinolate (LiQ). Amongst the compounds tested, lithium 2-((o-tolylimino)methyl) phenolate was found to enhance the efficiency of OLEDs by 69% compared to LiF and 15% compared to LiQ. The same electron injector was found to extend the lifetimes of OLEDs by six-fold compared to LiF and 4.3-fold compared to LiQ respectively. The crystal structure of the parent compound, lithium 2-((phenylamino)methyl)phenolate reveals that the compound is tetrameric in contrast to hexameric LiQ. Substituting the methyl group with fluorine causes a remarkable depression of the HOMO and LUMO levels by up to 1.2 eV. Analysis of current density vs. voltage characteristics of single-layer devices for Li–Al/electron injector/Li–Al and Al/electron injector/Al reveals that both sets of devices are operating as electron-only devices indicating that the formation of free lithium is the cause of enhanced electron injection, but either the energetic aluminium atoms (as proposed previously by other workers) or energetic lithium complexes on an aluminium surface (as we have demonstrated in this paper) are all that is required for efficient electron injection.
27 citations
TL;DR: Cobalt(II) diaryl complexes react with CO to afford Co(2)(CO)(8) and sterically encumbered ketones whose structure varies depending on the nature of the aryl ligands.
TL;DR: In this paper, a one-pot reaction of Boc-protected amino alcohols and 2-sulfobenzoic anhydride followed by the addition of a wide variety of primary amines has allowed rapid access to diverse libraries of amidosulfonates 1,2-C6H4(SO3-) (COCHR1CH2NH2+R2) (R1 = Bn, iPr, Ph; R2 = aryl, CHMePh, 1-adamantyl).
TL;DR: A range of nitroalkenes 1 and imines 3 derived from alkyl, aryl, and heteroaryl aldehydes underwent a tandem 1,4-hydride addition nitro-Mannich reaction to afford anti-rich β-nitroamines 4 to allow purification in good yield from the parent nitroalksenes.
Abstract: A range of nitroalkenes 1 and imines 3 derived from alkyl, aryl, and heteroaryl aldehydes underwent a tandem 1,4-hydride addition nitro-Mannich reaction to afford anti-rich β-nitroamines 4. The crude anti-β-nitroamines 4 could be converted to the corresponding anti-β-nitroacetamides 5 (33 examples) to allow purification in good yield from the parent nitroalkenes (60–87%), and with a high diastereomeric ratio (90:10 to mostly >95:5). A representative selection of anti-β-nitroacetamides 5 (five examples) were reduced to vicinal diamines 7 with zinc hydrochloride; concomitant acyl migration provided differentially protected vicinal diamines 7 in good yield (80–91%).
TL;DR: In this article, the crystal structures of dicationic ionic liquids with both modified cation and anion moieties were reported and the influence of the superramolecular ionic liquid architecture that these subtle changes incur.
Abstract: Here we report the crystal structures of dicationic ionic liquids (ILs) with both modified cation and anion moieties and discuss the influence of the “supramolecular ionic liquid architecture” that these subtle changes incur. The four dicationic ILs, 1,8-bis(1-methylimidazolium-3-yl)octane bromide (1), 1,8-bis(1,2-dimethylimidazolium-3-yl)octane bromide (2), 1,8-bis(1,2-dimethylimidazolium-3-yl)octane tetrafluoroborate (3) and 1,12-bis(1-methylimidazolium-3-yl)dodecane bromide (4) were prepared using established literature methods. Single crystals of the materials were grown (as solvates for 1·2H2O and 4·1.2(C7H8)) and the solid-state structural arrangements determined by single crystal X-ray diffraction.
TL;DR: Five new metal-organic frameworks prepared from the ligand 5-bis(3-(1-imidazolyl)propylcarbamoyl)terephthalate and transition metal salts are reported, revealing that the bipta(2-) ligand acts as a tetradentate ligand and combines with four-coordinate cationic metal nodes to give four-connected framework structures.
Abstract: Five new metal-organic frameworks prepared from the ligand 5-bis(3-(1-imidazolyl)propylcarbamoyl)terephthalate (bipta(2-)) and transition metal salts, Zn(2+) (1), Co(2+) (2), Mn(2+) (3, 4) and Cu(2+) (5), are reported. Single crystal X-ray studies reveal that the bipta(2-) ligand acts as a tetradentate ligand and combines with four-coordinate cationic metal nodes to give four-connected framework structures. Whilst reaction of bipta(2-) with Zn(II) gives rise to a framework of diamondoid topology 1, the analogous frameworks with Co(II), Mn(II) and Cu(II) afford frameworks that incorporate square-planar nodes. Whereas 2 and 5 form frameworks of Cd(SO(4)) (cds) and square 4(4) nets (sql), respectively, reaction of Mn(II) with bipta(2-) forms two supramolecular isomers of topology cds for 3 and sql for 4.
TL;DR: This work establishes that main group reagents can achieve selective borylations of fused polycyclic aromatics under mild conditions in good yields.
TL;DR: Multifrequency (Q, X, S, and L-band) EPR spectroscopic analysis of the Pd(II) complexes shows a one-electron oxidation process in MeCN, consistent with Jahn-Teller distortion at a low-spin d(7) Pd (III) center.
Abstract: The Pd(II) complexes [Pd([9]aneS(3))(2)](PF6)(2)center dot 2MeCN (1) ([9]aneS(3) = 1,4,7-trithiacyclononane) and [Pd([18]aneS(6))](PF6)(2) (2) ([18]aneS6 = 1,4,7,10,13,16-hexathiacyclooctadecane) can be oxidized electrochemically or chemically oxidized with 70% HClO4 to [Pd([9]aneS(3))(2)](3+) and [Pd([18]aneS(6))](3+), respectively. These centers have been characterized by single crystal X-ray diffraction, and by UV/vis and multifrequency electron paramagnetic resonance (EPR) spectroscopies. The single crystal X-ray structures of [Pd-III([9]aneS(3))(2)]-(ClO4)(6)center dot(H3O)(3)center dot(H2O)(4) (3) at 150 K and [Pd([18]aneS(6))]-(ClO4)(6)center dot(H5O2)(3) (4) at 90 K reveal distorted octahedral geometries with Pd S distances of 2.3695(8), 2.3692(8), 2.5356(9) and 2.3490(6), 2.3454(5), 2.5474(6) angstrom, respectively, consistent with Jahn-Teller distortion at a low-spin d(7) Pd(III) center. The Pd(II) compound [Pd([9)aneS(3))(2)}(PF6)(2) shows a one-electron oxidation process in MeCN (0.2 M NBu4PF6, 293 K) at E-1/2 = +0.57 V vs. Fc(+)/Fc assigned to a formal Pd(III)/Pd(II) couple. Multifrequency (Q-, X-, S-, and L-band) EPR spectroscopic analysis of [Pd([9]aneS(3))(2))(3+) and [Pd([18]aneS(6))](3+) gives g(iso) = 2.024, vertical bar A(iso(pd))vertical bar = 18.9x 10(-4) cm(-1); g(xx) = 2.046, g(yy) = 2.041, g(zz) = 2.004; vertical bar A(xx(pd))vertical bar = 24 X 10(-4) cm(-1), vertical bar A(yy(Pd))vertical bar = 22 x 10(-4) cm(-1), IA(zz(Pd))vertical bar = 14 x 10(-4) cm(-1), vertical bar a(xx(H))vertical bar = 4 X 10(-4) cm(-1), vertical bar a(yy(H))vertical bar = 5 X 10(-4) cm(-1), vertical bar a(zz(H))vertical bar= 5.5 X 10(-4) cm(-1) for [Pd([9]aneS(3))(2)](3+), and g(iso) = 2.015, broken vertical bar A(iso(pd))vertical bar = 18.8 x 10(-4) cm(-1); g(xx) = 2.048 g(yy) = 2.036, g(zz) = 1.998; vertical bar a(xx(H))vertical bar = 5, la(yy(H))vertical bar = 5, vertical bar a(zz(H))vertical bar = 6 x 10(-4) cm(-1); = vertical bar A(xx(Pd))vertical bar = 23 x 10(-4) cm(-1), vertical bar A(yy(pd))vertical bar = 22 x 10(-4) cm(-1), vertical bar A(zz(pd))vertical bar = 4 X 10(-4) cm(-1) for [Pd([18]aneS(6))](3+). Both [Pd([9]aneS(3))(2)](3+) and [Pd( [18]aneS(6))(3+) exhibit five-line superhyperfme splitting in the g(zz) region in their frozen solution EPR spectra. Double resonance spectroscopic measurements, supported by density functional theory (DFT) calculations, permit assignment of this superhyperfine to through-bond coupling involving four H-1 centers of the macrocyclic ring. Analysis of the spin Hamiltonian parameters for the singly occupied molecular orbital (SOMO) in these complexes gives about 20.
TL;DR: A novel family of paramagnetic tetranuclear ferrous cubanes is reported and two complexes from this family are described and their magnetic properties are discussed in relation to their structures.
TL;DR: This study analysed the OM response in 3 non-osteogenic lines, HEK293, HeLa and NTera, and found that these 2 models can deposit mineral through a mechanism independent of established dexamethasone or bone morphogenetic protein signalling.
Abstract: Bone marrow-derived mesenchymal stem cells (MSCs) are widely used as a cellular model of bone formation, and can mineralize in vitro in response to osteogenic medium (OM). It is unclear, however, whether this property is specific to cells of mesenchymal origin. We analysed the OM response in 3 non-osteogenic lines, HEK293, HeLa and NTera, compared to MSCs. Whereas HEK293 cells failed to respond to OM conditions, the 2 carcinoma-derived lines NTera and HeLa deposited a calcium phosphate mineral comparable to that present in MSC cultures. However, unlike MSCs, HeLa and NTera cultures did so in the absence of dexamethasone. This discrepancy was confirmed, as bone morphogenetic protein inhibition obliterated the OM response in MSCs but not in HeLa or NTera, indicating that these 2 models can deposit mineral through a mechanism independent of established dexamethasone or bone morphogenetic protein signalling.
TL;DR: Using biomimetic chemical reduction or Clostridium perfringens cell extract containing azoreductase, the dimer-fluorescent probe is reduced to the tetra-equatorial 2,4-O-bisdansyl-cyclohexyl-3,5-bisammonium salt which exhibits fluorescence indicative of a dansyl monomer.
TL;DR: In this article, illustrated extracts from the writings of Paul P. Ewald and Max von Laue are presented, together with extensive text contributions from William Lawrence Bragg, who used Trinity College Cambridge as his address on his early papers; experimental work was done by him in the Cavendish Laboratory, Cambridge, and also with his father, W.H.L. Bragg.
Abstract: Illustrative extracts from the writings of Paul P. Ewald and of Max von Laue are presented. The latter in turn contains extensive text contributions from William Lawrence Bragg. These selections we have chosen so as to indicate the nature of the discovery of X-ray diffraction from crystals (experiments undertaken by Friedrich, Knipping and von Laue) and its early and prompt application in crystal structure analyses (by William Henry Bragg and William Lawrence Bragg). The platform for these discoveries was provided by a macroscopic physics problem dealt with by Ewald in his doctoral thesis with Arnold Sommerfeld in the Munich Physics Department, which is also where von Laue was based. W.L. Bragg was a student in Cambridge who used Trinity College Cambridge as his address on his early papers; experimental work was done by him in the Cavendish Laboratory, Cambridge, and also with his father, W.H. Bragg, in the Leeds University Physics Department. Of further historical interest is the award of an Honorary DSc...
TL;DR: In this paper, the authors investigated the mutual role played by the bis (2-methylpyridyl)alkyl(thioalkyl)diamines and the signalling units attached to them in reaching the selectivity of the responses observed.
TL;DR: The title complex, [Cu(ClO(4))(2)(C(9)H(13)N(5)O)(CH(3)OH)], was synthesized from a methanolysis reaction of N-(methylpyridin-2-yl)cyanoguanidine (L(3)) and copper(II) perchlorate hexahydrate in a 1:1 molar ratio.
Abstract: The title complex, [Cu(ClO(4))(2)(C(9)H(13)N(5)O)(CH(3)OH)], was synthesized from a methanolysis reaction of N-(methylpyridin-2-yl)cyanoguanidine (L(3)) and copper(II) perchlorate hexahydrate in a 1:1 molar ratio. The Cu(II) ion is six-coordinated by an N(3)O(3) donor set which confers a highly distorted and asymmetric octahedral geometry. Three N-donor atoms from the chelating 1-(methoxymethanimidoyl)-2-(pyridin-2-ylmethyl)guanidine (L(3m)) ligand and one O atom from the methanol molecule define the equatorial plane, with two perchlorate O atoms in the apical sites, one of which has a long Cu-O bond of 2.9074 (19) A. The dihedral angle between the five- and six-membered chelate rings is 8.21 (8)°. Two molecules are associated into a dimeric unit by intermolecular N-H...O(perchlorate) hydrogen bonds. Additionally, the weakly coordinated perchlorate anions also link adjacent [Cu(ClO(4))(2)(L(3m))(CH(3)OH)] dimers by hydrogen-bonding interactions, resulting in a two-dimensional layer in the (100) plane. Further C-H...O hydrogen bonds link the two-dimensional layers along [100] to generate a three-dimensional network.
TL;DR: The role of pyridyl-based molecules in forming hydrogen-bonded chains with 5,5-diethylbarbituric acid (DEB) was described in this article.
Abstract: Supramolecular interactions play an important role in determining the solid-state structures of many molecular species. In this study, we describe the role of pyridyl-based molecules in forming hydrogen-bonded chains with 5,5-diethylbarbituric acid (DEB). The single crystal X-ray structures of three hydrogen-bonded co-crystals all exhibit one-dimensional chains formed via N–H…N interactions between pyridyl hydrogen bond acceptors and N–H hydrogen bond donors of DEB. Subtle differences are observed between the three related co-crystals. Although both DEB·4,4’-bipy, 1, and DEB·diaz, 2, (diaz = 2,7-diazapyrene) adopt similar one-dimensional chains with a 1:1 DEB:bipyridyl stoichiometry, π–π interactions play a significant role in the solid-state arrangement of 2 only. In 2(DEB)·dpb, 3, (dpb = 1,4-bis(4-pyridyl)-benzene), an alternative 2:1 DEB:bipyridyl stoichiometry is observed. Dimeric DEB hydrogen-bonded units are linked into hydrogen-bonded chains through further hydrogen bonding. The co-crystal DEB·pypm...
TL;DR: In this article, the efficient, widely applicable, and highly diastereoselective method affords β-nitroamines which can be converted into 1,2-diamines.
Abstract: The efficient, widely applicable, and highly diastereoselective method affords β-nitroamines which can be converted into 1,2-diamines.
TL;DR: In the title compound [systematic name: (1Z,3Z)-1,3-dihydrazinylidene-1H-inden-2(3H)-one], C(9)H(8)N(4)O, isolated molecules possess approximate noncrystallographic C(2v) symmetry and their cis conformation and planarity are assisted by a pair of short intramolecular N-H···O hydrogen bonds.
Abstract: In the title compound [systematic name: (1Z,3Z)-1,3-dihydrazinylidene-1H-inden-2(3H)-one], C(9)H(8)N(4)O, isolated molecules possess approximate noncrystallographic C(2v) symmetry and their cis conformation and planarity are assisted by a pair of short intramolecular N-H···O hydrogen bonds. Each molecule is asymmetrically involved in an extensive three-dimensional network of N-H···O and N-H···N hydrogen bonds, and the structure also exhibits weaker π-π and C=O···C interactions. The structure features an R(4)(4)(12) motif consisting solely of N and H atoms and possessing crystallographic 4 symmetry.
TL;DR: New NHC ligand precursors are synthesized, which serve as highly active catalysts (turnover number about 100) for γ-selective additions to cinnamyl electrophiles without the need for metal salts as discussed by the authors.
Abstract: New NHC ligand precursors are synthesized, which serve as highly active catalysts (turnover number about 100) for γ-selective additions to cinnamyl electrophiles without the need for metal salts.