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The dearomative spirocyclisation of benzisoxazoles through a radical chain mechanism is described. Densely functionalised spirocycles were prepared in high yields by reacting benzisoxazole‐tethered ynones with aryl thiols in 1,2‐dichloroethane (DCE) at 60 °C. The identification of stabilising three‐electron interactions was key to the development of this new radical cascade reaction. The obtained spirocyclic products were converted into other spirocyclic scaffolds through a two‐step hydrogenolysis‐cyclisation sequence. [ABSTRACT FROM AUTHOR]

Results from the determination of sixteen X-ray single crystal structures are reported for a series of 3-(4-alkoxyphenyl)-5-perfluoroalkyl-2,4-dimethyl-1,2,4-triazolium salts with tetrafluoroborate, triflate or bistriflimide anions, in which the lengths of the alkoxy and perfluoroalkyl chains are varied systematically. On account of these cations having a hydrocarbon, fluorocarbon and ionic part, they are classified as triphilic. All of the tetrafluoroborate salts crystallised in the P21/c space group, most as acetone solvates, while for the bistriflimide salts, four different space groups were found although all contained a P21 screw axis often with additional symmetry elements. Of the triflates, two crystallised in space groups with a P21 screw axis and two in P1¯. The organisation in the crystalline state tended to reflect the triphilic nature of the materials with cations and anions associating in repeating motifs, while the rest of the space was occupied by either hydrocarbon or fluorocarbon domains with only two exceptions. [ABSTRACT FROM AUTHOR]

Single crystals of the molecular compound, {Cu20Ir6Cl8(C21H24N2)6(C4H4N2)3]·3.18CH3OH or [({Cu10Ir3}Cl4(IMes)3(pyrazine))2(pyrazine)]·3.18CH3OH [where IMes is 1,3-bis (2,4,6-trimethylphenyl)imidazol-2-ylidene], with a unique heterometallic cluster have been prepared and the structure revealed using single-crystal X-ray diffraction. The molecule is centrosymmetric with two {Cu10Ir3} cores bridged by a pyrazine ligand. The polymetallic cluster contains three stabilizing N-heterocyclic carbenes, four Cl ligands, and a non-bridging pyrazine ligand. Notably, the Cu--Ir core is arranged in an unusual shape containing 13 vertices, 22 faces, and 32 sides. The atoms within the tridecametallic cluster are arranged in four planes, with 2, 4, 4, 3 metals in each plane. Ir atoms are present in alternate planes with an Ir atom featuring in the peripheral bimetallic plane, and two Ir atoms featuring on opposite sides of the non-adjacent tetrametallic plane. The crystal contains two disordered methanol solvent molecules with an additional region of non-modelled electron density corrected for using the SQUEEZE routine in PLATON [Spek (2015[Spek, A. L. (2015). Acta Cryst. C71, 9-18.]). Acta Cryst. C71, 9-18]. The given chemical formula and other crystal data do not take into account the unmodelled methanol solvent molecule(s). [ABSTRACT FROM AUTHOR]

Hydrogen-bonded complexes are formed between two chain lengths of 4-alkoxystilbazoles and six different chlorophenols. Single crystal structure determinations were possible for four of the complexes, all of which showed a similar dimeric motif in which two chlorophenols formed a loose back-to-back dimer with a stilbazole hydrogen-bonded at either side. Two of the complexes showed similarities in their three-dimensional packing. Liquid crystal properties were found for all complexes except those containing pentachlorophenol. The phase behaviour of the longer-chain dodecyloxystilbazole complexes was dominated by the observation of the smectic A phase, while both nematic and smectic A phases were found for the octyloxy homologues. The mesophase stability was appreciably lower in these new complexes when compared with fluorophenol analogues reported previously, attributed to a reduction in anisotropy on account of the effects of the greater size of chlorine compared with fluorine. [ABSTRACT FROM AUTHOR]

Pd02(dba)3 (dba = E,E-dibenzylidene acetone) is the most widely used Pd0 source in Pd-mediated transformations. Pd02(dba-Z)3 (Z = dba aryl substituents) complexes exhibit remarkable and differential catalytic performance in an eclectic array of cross-coupling reactions. The precise structure of these types of complexes has been confounding, since early studies in 1970s to the present day. In this study the solution and solid-state structures of Pd02(dba)3 and Pd02(dba-Z)3 have been determined. Isotopic labeling (²H and `3C) has allowed the solution structures of the freely exchanging major and minor isomers of Pd02(dba)3 to be determined at high field (700 MHz). DFT calculations support the experimentally determined major and minor isomeric structures, which show that the major isomer of Pd02(dba)3 possesses bridging dba ligands found exclusively in a s-cis,s-trans conformation. For the minor isomer one of the dba ligands is found exclusively in a s-trans,s-trans conformation. Single crystal X-ray diffraction analysis of Pd02(dba)3·CHC13 (high-quality data) shows that all three dba ligands are found over two positions. NMR spectroscopic analysis of Pd02(dba-Z)3 reveals that the aryl substituent has a profound effect on the rate of Pd-olefln exchange and the global stability of the complexes in solution. Complexes containing the aryl substituents, 4-CF3, 4-F, 4-t-Bu, 4-hexoxy, 4-OMe, exhibit well-resolved ¹H NMR spectra at 298 K, whereas those containing 3,5-OMe and 3,4,5-OMe exhibit broad spectra. The solid-state structures of three Pd02(dba-Z)3 complexes (4-F, 4-OMe, 3,5-OMe) have been determined by single crystal X-ray diffraction methods, which have been compared with Goodson's X-ray structure of Pd02(dba-4-OH)3. [ABSTRACT FROM AUTHOR]

Theeffects of substituting (pseudo)halide for anionic imidateligands in Au(I) and Au(III) (i.e. [AuBr(NHC)] and [AuBr3(NHC)]) complexes have been investigated. [Au(N-imidate)(NHC)]and [AuBr2(N-imidate)(NHC)] complexeswere prepared and the structure and bonding of the complexes examinedspectroscopically and crystallographically. The [AuBr2(N-imidate)(NHC)] complexes, in combination with Ag salts,were tested for catalytic activity in the cycloisomerization of 1,5-enynesand found to be more effective than the tribromide analogues (e.g.[AuBr3(NHC)]). Subtle changes to the anionic imidate ligandstructure had a pronounced effect on the catalytic activity of theAu(III) complexes. [ABSTRACT FROM AUTHOR]

The dimeric di-μ-chlorido anion hexachloridopalladate(II)platinate(II) has been prepared as a mixture with hexachloridodipalladate(II) and hexachloridodiplatinate(II) and has been identified by using a combination of X-ray crystallography and 195Pt NMR spectroscopy. This is the first report of a heterodinuclear dimer of this type. [ABSTRACT FROM AUTHOR]

48 new hydrogen-bonded complexes have been prepared by combining 16 fluorophenols of general formula C6F nH5− nOH with three different alkoxystilbazoles (butyloxy-, octyloxy- and dodecyloxy-). Single-crystal X-ray structures were obtained for 10 of the 16 complexes of octyloxystilbazole from which it was found that most of the structures could be collected into one of two groups according to both the motif shown by the complex and by the solid-state packing. Because all but one crystallised in the P $\bar 1$ space group, meaningful comparisons could be drawn and it was observed that six structures were extremely close in nature so that significant molecular overlap was found. On this basis, doubt is cast on the significance of some of the weaker intermolecular contacts found in the solid state. 40 of the new complexes showed liquid-crystal properties and it was found that although complexes of butyloxystilbazole were all nematic, almost all of those with dodecyloxystilbazole showed a smectic A (SmA) phase. Complexes of octyloxystilbazole showed a mixture of both. Structure/property correlations showed that clearing points were independent of the p Ka of the phenol. The most stable mesophases were found when the fluorophenol contained a fluorine at the 2-position, which was interpreted in terms of the formation of an intramolecular H⋅⋅⋅F hydrogen bond to give a six-membered ring linking the two components into a stable, coplanar conformation. The least stable mesophases were found when no such ring formation was possible and the phenol was relatively free to move. [ABSTRACT FROM AUTHOR]

Abstract: The preparation is described of bimetallic complexes of the multidentate ligand, H6TTHA – triethylenetetraamine-N,N′,N″,N‴-hexaacetic acid. Attempts to use a stepwise approach systematically to prepare heterobimetallic complexes were unsuccessful and led in most cases to homobimetallic complexes or to heterobimetallic complexes whose stoichiometry did not reflect the stoichiometry of the preparation. Nonetheless, on one occasion a monodisperse heterobimetallic complex of rhodium and zinc was isolated, which represents the first properly characterised heterobimetallic complex of TTHA. [Copyright &y& Elsevier]

The intermolecular Pauson--Khand (PK) reactions of sterically comparable (2-phenylethynyl)heteroaromatic compounds with norbornene, mediated by Co2(CO)8 to give cyclopentenone products, were examined in this study. A synthetic protocol utilizing focused-microwave dielectric heating proved indispensable in the efficient synthesis of the PK cyclopentenone products. "π-Deficient" heteroaromatic substrates, e.g., 2-pyrones, and some "π-excessive" heteroaromatics such as 2- and 3-thiophene and 2-furan favor the β-position in the newly formed cyclopentenone ring. Other π-excessive heteroaromatics such as 2-pyrrole or 2-indole favor the α-position. A πexcessive 3-indole derivative gave a nearly equal mixture of regioisomers. The position of the nitrogen in pyridyl-containing alkyne substrates also affects the regiochemical outcome of the PK reaction. A 2-pyridyl alkyne, possessing a proximal nitrogen, influences the regioselectivity relative to a 4-pyridyl variant quite dramatically, favoring the β-position in the newly formed cyclopentenone ring. A 2-pyrimidylalkyne exhibits similar behavior to the 2-pyridylalkyne. Compounds that do not participate in PK reactions with norbornene include (2-phenylethynyl)imidazoles and the related benzimidazoles, which promote rapid decomposition of the in situ generated (µ2-alkyne) (Co2 (CO)6 complexes. This stands in contrast with other nitrogen-containing heteroaromatics, e. g., pyrrole-, indole-, and pyrimidine-derived compounds, which effectively undergo PK reactions. Overall, the type of hereroaromatic group dramatically influences PK regioselectivity, which can in part be explained by rationalization of the current reaction mechanism, bu not fully. [ABSTRACT FROM AUTHOR]

The synthesis and characterisation of a multidentate conformationally flexible ligand based on the dibenzylidene acetone core structure, dbathiophos (1), is described. Ligand 1has a high affinity for cationic and neutral CuIspecies. Three unique CuIcomplexes (4–6) are reported showing that the ligand backbone of dbathiophos is hemilabile, and able to adopt different 1,4-dien-3-one conformational geometries around CuI. Complexes 4and 6both effectively catalyse the cyclopropanation of styrene with ethyl diazoacetate at low catalyst loadings (1 mol% Cu). [ABSTRACT FROM AUTHOR]

The new heteroditopic ligand 2,3-dihydroxy-N-(1,10-phenanthroline-5-yl)benzamide (H2-L³) was synthesized and coordinated to [Ru(bpy)2(phen)]2+- and [ReBr(CO)3(phen)]-type luminophores (bpy = 2,2′-bipyridine and phen = 1,10-phenanthroline). The resulting chemosensors [Ru(bpy)2(H2-L³)]2+ and [ReBr(CO)3(H2-L³)] were fully characterized and their solid-state structures and spectroscopic properties were investigated to assess how the photophysical properties of the luminescent signaling units affect the performance of the sensors. [Ru(bpy)2(H2-L³)]2+ and [ReBr- (CO)3(H2-L³)] both signal the presence and concentration of molybdate and vanadate in aqueous acetonitrile through a decrease in emission intensity. [ReBr(CO)3(H2-L³)] also detects tungstate. Due to the higher emission intensity of the Ru-based sensor, its detection limits for molybdate (43 µg L-1) and vanadate (24 ,µ L-1) are almost 1 order of magnitude lower than the ones achieved with the Re-based sensor. The optimum working pH of the chemosensors is determined by the PKa values of the 2-hydroxy-groups of the receptor units: pH 4 for [ReBr(CO)3(H2-L³)] and pH 3 for [Ru(bpy)2(H2-L³)]2+. Both sensors are selective: equimolar amounts of PO43-, SO42-, ReO4-, Mn(ll), Fe(lll), Co(II), Ni(ll), Cu(ll), and Zn(lI) do not interfere with the detection of molybdate or vanadate. [ABSTRACT FROM AUTHOR]

The C^N^C ligand 2,6-bis(2,3-dialkoxyphenyl)pyridine forms dimercury and orthopalladated complexes, both of which may be transmetallated to gold(III) complexes; the gold complexes may also be formed directly in a Rh(III)-catalysed process, hence it is possible to circumvent the use of organomercury intermediates in the synthesis of this important class of compound. [ABSTRACT FROM AUTHOR]

Polyesters are important materials with a wide range of applications, but there has been increasing concern over their sustainability. One example is the need for safer, bio-derived solvents to replace those currently in use for the polymer’s synthesis and processing. In this work, several variants of the bio-based cellulose/levoglucosenone derived solvent Cyrene, namely the ketal derivatives dioxolane Cygnet, dioxane Cygnet and dioxepane Cygnet were synthesized and tested as media for enzymatic polycondensation reactions using bio-based building blocks. Dioxolane Cygnet and dioxepane Cygnet were found to be suitable solvents for enzymatic polycondensation reactions, with dioxolane Cygnet being the preferred solvent, yielding polymers with a Mn >22 kDa. In addition, these solvents were tested in the biocatalyzed synthesis of levoglucosenone-based polyesters. The alternative solvents gave superior yields to those previously observed, demonstrating the versatility of these solvents in enzymatic polycondensation reactions, representing the first synthetic polymer-solvent system fully derived from cellulose. [ABSTRACT FROM AUTHOR]

Floridoside (2-α-O-D-galactopyranosyl glycerol) is a glycerol glycoside that is biosynthesised by most species of red algae and has been implicated as an intracellular regulator of various homeostatic functions. Here, we report the identification of two unforeseen crystal forms of the ubiquitous natural osmolyte floridoside including a seemingly unheralded second anhydrous conformational polymorph and the unambiguous description of an elusive monohydrated variant. By employing a variety of thermal and spectroscopic techniques, we begin to explore both their macro and molecular physicochemical properties, which are notably different to that of the previously reported polymorph. This work advances the characterisation of this important natural biomolecule which could aid in facilitating optimised utilisation across a variety of anthropocentric applications and improve comprehension of its role in-vivo as a preeminent compatible solute. Floridoside is a glycerol glycoside that is biosynthesised by most species of red algae and has been implicated as an intracellular regulator of various homeostatic functions. Here the authors report and characterise previously unforeseen crystal forms of floridoside: an anhydrous polymorph and a crystalline stoichiometric monohydrate. [ABSTRACT FROM AUTHOR]

Progress towards the total synthesis of the macrolide natural product anthracimycin is described. This new approach utilises an intermolecular Diels-Alder strategy followed by epimeirsation to form the key trans-decalin framework. The route culminates in the stereoselective synthesis of an advanced tricyclic lactone intermediate, containing five contiguous sterogenic centres with the correct relative and absolute stereochemistry required for the anthracimycin core motif. [ABSTRACT FROM AUTHOR]

Macrocyclic and medium‐sized ring ketones, lactones and lactams can all be made from common acryloyl imide starting materials through divergent, one‐pot cascade ring‐expansion reactions. Following either conjugate addition with an amine or nitromethane, or osmium(VIII)‐catalysed dihydoxylation, rearrangement through a four‐atom ring expansion takes place spontaneously to form the ring expanded products. A second ring expansion can also be performed following a second iteration of imide formation and alkene functionalisation/ring expansion. In the dihydroxylation series, three‐ or four‐atom ring expansion can be performed selectively, depending on whether the reaction is under kinetic or thermodynamic control. [ABSTRACT FROM AUTHOR]

Co(II), Ni(II) and Ag(I) complexes of mefenamic acid (Hmef)/tolfenamic acid (Htolf) and metronidazole (met) formulated as [Co(mef)2(met)2] (1), [Ni(tolf)2(met)2] (2) and [Ag(met)2](NO3)·Htolf (3) have been synthesized and characterized. Single-crystal X-ray crystallography of 1 reveals a polymeric motif in a distorted octahedral geometry. Each unit of 1 consists of two mef moieties which coordinate monodentately to the Co(II) ion via deprotonated carboxylate groups, two met ligands coordinate to the Co(II) center through the N-atom, while the hydroxyethyl oxygen of another molecule complete the octahedral geometry around the Co(II) ion. The FTIR of 2 and 3 suggested that coordination occurred through the imine N-atom of met and O-atom of tolf. Cyclic voltammogram of 1 represents a two-step, one-electron process, assignable to Co(III)/Co(II) and Co(II)/Co(I) redox pairs, while the ill-defined voltammogram of 2 suggested a Ni(II)/Ni(I) reduction process. The radical scavenging and ferrous ion chelating potentials of the three compounds indicated better antioxidant capacity (p < 0.05) than the standard (BHT). Iron chelating ability (IC50 values) of the compounds is in the order 1 > BHT > 3 > 2 > met > Hmef > Htolf. The toxicology for 1-3 using Drosophila melanogaster model revealed a good safety level. [ABSTRACT FROM AUTHOR]

A dinuclear, butadiene-bridged complex, trans-μ2:η2,η2-1,3-butadiene-bis(trichloroplatinate(ii)) (1) was unexpectedly obtained on photolysis of acetone solutions of (NBu4)2[PtCl6]. [ABSTRACT FROM AUTHOR]

It has been shown for the first time that the PtIV complex cis‐[Pt(N^C‐tolpy)2Cl2] (tolpy=2‐(4‐tolyl)pyridinyl) can be prepared in a one‐pot reaction from K2[PtCl4], although analogous complexes containing 2,5‐bis(4‐dodecyloxyphenyl)pyridine (=HL) could be prepared using existing routes. The resulting complexes cis‐[Pt(N^C‐L)2Cl2] are liquid crystals and small‐angle X‐ray scattering suggests formation of a lamellar mesophase. Surprisingly, heating [Pt(κ2‐N^C‐L)2Cl(κ1‐N^C‐LH)] also leads to a mesomorphic compound, which results from thermally induced oxidation to cis‐[Pt(N^C‐L)2Cl2] and what is presumed to be another geometric isomer of the same formula. The PtIV complexes are quite strongly luminescent in deoxygenated solution, with φ≈10 % and show vibrationally structured emission spectra, λmax(0,0)=532 nm, strongly displaced to the red compared to cis‐[Pt(N^C‐tolpy)Cl2]. Long luminescence lifetimes of 230 μs are attributed to a lower degree of metal character in the excited state accompanying the extension of conjugation in the ligand. There is no significant difference between the emission properties of the bromo‐ and chloro‐complexes, in contrast with the known complexes cis‐[Pt(N^C‐ppy)X2], where the quantum yield for X=Br is some 30 times lower than for X=Cl (ppyH=2‐phenylpyridine). The lower energy of the excited state in the new complexes probably ensures that deactivating LLCT/LMCT states remain thermally inaccessible, even when X=Br. The platinum(IV) complexcis‐[Pt(N^C‐tolpy)2Cl2] (tolpy=2‐(4‐tolyl)pyridine) can be prepared directly in a one‐pot reaction from K2[PtCl4]. Analogous complexes cis‐[Pt(N^C‐L)2Cl2] that contain the related, elaborated ligand 2,5‐bis(4‐dodecyloxyphenyl)pyridine are better prepared by a multistep route and show both emissive and liquid‐crystalline properties. Heating the neat platinum(II) complex [Pt(κ2‐N^C‐L)2Cl(κ1‐N^C‐LH)] results in a thermally induced oxidation to cis‐[Pt(N^C‐L)2Cl2]. The physical properties of these complexes were studied using a variety of techniques and TD‐DFT was used to rationalise the photophysical response. [ABSTRACT FROM AUTHOR]

Dihydrolevoglucosenone (Cyrene®) has been successfully utilised as a bio-based platform molecule for the synthesis of pharma-ceutically relevant intermediates through aldol condensation reactions. Utilising sustainable synthetic methodologies, the self-aldol condensation reaction of Cyrene was achieved in high purity, with isolated yields of 81.3%. Claisen-Schmidt reactions with a range of aromatic and heteroaromatic aldehydes yielded several previously unreported Cyrene-based compounds, characterised by single-crystal X-ray diffraction, FT-IR, NMR and MS. [ABSTRACT FROM AUTHOR]

A novel scaffold for the construction of self-organised ionic liquids and ionic liquid crystals bearing both perfluorocarbon and hydrocarbon moieties has been developed. The phase behaviour and physical properties of these materials can be tuned as a function of chain length and fluorine content and significant structural elaboration is possible, giving a highly flexible system. [ABSTRACT FROM AUTHOR]

Mn(I) C−H functionalization of coumarins provides a versatile and practical method for the rapid assembly of fused polycyclic pyridinium‐containing coumarins in a regioselective manner. The synthetic strategy enables application of bench‐stable organomanganese reagents in both photochemical‐ and thermal‐promoted reactions. The cyclomanganated intermediates, and global reaction system, provide an ideal testing ground for structural characterization of the active Mn(I) carbonyl‐containing species, including transient species observable by ultra‐fast time‐resolved spectroscopic methods. The thermodynamic reductive elimination product, solely encountered from reaction between alkynes and air‐stable organometallic cyclomanganated coumarins, has enabled characterization of a critical seven‐membered Mn(I) intermediate, detected by time‐resolved infrared spectroscopy, enabling the elucidation of the temporal profile of key steps in the reductive elimination pathway. Quantitative data are provided. Manganated polycyclic products are readily decomplexed by AgBF4, opening‐up an efficient route to the formation of π‐extended hybrid coumarin‐pyridinium compounds. [ABSTRACT FROM AUTHOR]

A computational study of the C(methyl)–O bond activation of fluorinated aryl methyl ethers by a platinum(0) complex Pt(PCyp3)2 (Cyp = cyclopentyl) (N. A. Jasim, R. N. Perutz, B. Procacci and A. C. Whitwood, Chem. Commun., 2014, 50, 3914) demonstrates that the reaction proceeds via an SN2 mechanism. Nucleophilic attack of Pt(0) generates an ion pair consisting of a T-shaped platinum cation with an agostic interaction with a cyclopentyl group and a fluoroaryloxy anion. This ion-pair is converted to a 4-coordinate Pt(ii) product trans-[PtMe(OArF)(PCyp3)2]. Structure-reactivity correlations are fully consistent with this mechanism. The Gibbs energy of activation is calculated to be substantially higher for aryl methyl ethers without fluorine substituents and higher still for alkyl methyl ethers. These conclusions are in accord with the experimental results. Further support was obtained in an experimental study of the reaction of Pt(PCy3)2 with 2,3,5,6-tetrafluoro-4-allyloxypyridine yielding the salt of the Pt(η3-allyl) cation and the tetrafluoropyridinolate anion [Pt(PCy3)2(η3-allyl)][OC5NF4]. The calculated activation energy for this reaction is significantly lower than that for fluorinated aryl methyl ethers. [ABSTRACT FROM AUTHOR]

Two new ring expansion strategies are reported for the synthesis of medium sized ring and macrocyclic sulfonamides. Both methods can be performed without using classical protecting groups, with the key ring expansion step initiated by nitro reduction and amine conjugate addition respectively. Each method can be used to make diversely functionalised cyclic sulfonamides in good to excellent yields, in a range of ring sizes. The ring size dependency of the synthetic reactions is in good agreement with the outcomes modelled by Density Functional Theory calculations. [ABSTRACT FROM AUTHOR]

Two new ring expansion strategies are reported for the synthesis of medium sized ring and macrocyclic sulfonamides. Both methods can be performed without using classical protecting groups, with the key ring expansion step initiated by nitro reduction and amine conjugate addition respectively. Each method can be used to make diversely functionalised cyclic sulfonamides in good to excellent yields, in a range of ring sizes. The ring size dependency of the synthetic reactions is in good agreement with the outcomes modelled by Density Functional Theory calculations. [ABSTRACT FROM AUTHOR]

Strongly halogen-bonded complexes are formed between 4-alkoxyphenyl-4-pyridines and iodine as well as the interhalogen compounds ICl and IBr, and examples of each are characterised by single crystal X-ray crystallography. On heating, all but one of the complexes display a liquid-crystalline smectic A phase, although there is evidence of decomposition as the materials are heated through the mesophase. For such short molecules, the mesophases are rather stable and small-angle X-ray scattering shows that the complexes form a type of antiparallel, head-to-head dimeric arrangement in the mesophase. Quantum chemical calculations at the DFT (M06-2X) and MP2 levels of theory show the complexes to have very high dipole moments (between ≈ 9–12 D) and the mesophase stability of the complexes is rationalised in terms of antiparallel correlations induced by the strong molecular dipoles. [ABSTRACT FROM AUTHOR]

The reaction between [IrCl(COD)]2 and dppe in a 1 : 2 ratio was investigated in detail under three different conditions. [IrCl(COD)(dppe)], 1, is formed at room temperature in the absence of base. In the presence of a strong base at room temperature, hydride complexes that retain the carbocyclic ligand in the coordination sphere are generated. In isopropanol, 1 is converted into [IrH(1,2,5,6-η2:η2-COD)(dppe)] (2) on addition of KOtBu, with k12 = (1.11 ± 0.02) × 10−4 s−1, followed by reversible isomerisation to [IrH(1-κ-4,5,6-η3-C8H12)(dppe)] (3) with k23 = (3.4 ± 0.2) × 10−4 s−1 and k32 = (1.1 ± 0.3) × 10−5 s−1 to yield an equilibrium 5 : 95 mixture of 2 and 3. However, when no hydride source is present in the strong base (KOtBu in benzene or toluene), the COD ligand in 1 is deprotonated, followed by β-H elimination of an IrI–C8H11 intermediate, which leads to complex [IrH(1-κ-4,5,6-η3-C8H10)(dppe)] (4) selectively. This is followed by its reversible isomerisation to 5, which features a different relative orientation of the same ligands (k45 = (3.92 ± 0.11) × 10−4 s−1; k5-4 = (1.39 ± 0.12) × 10−4 s−1 in C6D6), to yield an equilibrated 32 : 68 mixture of 4 and 5. DFT calculations assisted in the full rationalization of the selectivity and mechanism of the reactions, yielding thermodynamic (equilibrium) and kinetic (isomerization barriers) parameters in excellent agreement with the experimental values. Finally, in the presence of KOtBu and isopropanol at 80 °C, 1 is transformed selectively to K[IrH4(dppe)] (6), a salt of an anionic tetrahydride complex of IrIII. This product is also selectively generated from 2, 3, 4 and 5 and H2 at room temperature, but only when a strong base is present. These results provide an insight into the catalytic action of [IrCl(COD)(LL)] complexes in the hydrogenation of polar substrates in the presence of a base. [ABSTRACT FROM AUTHOR]

The luminescent and mesomorphic properties of a series of metal complexes based on hexacatenar 2,2′:6′,2′′-terpyridines are investigated using experimental methods and density functional theory (DFT). Two types of ligand are examined, namely 5,5′′-di(3,4,5-trialkoxyphenyl)terpyridine with or without a fused cyclopentene ring on each pyridine and their complexes were prepared with the following transition metals: ZnII, CoIII, RhIII, IrIII, EuIII and DyIII. The exact geometry of some of these complexes was determined by single X-ray diffraction. All complexes with long alkyl chains were found to be liquid crystalline, which property was induced on complexation. The liquid-crystalline behaviour of the complexes was studied by polarising optical microscopy and small-angle X-ray diffraction. Some of the transition metal complexes (for example, those with ZnII and IrIII) are luminescent in solution, the solid state and the mesophase; their photophysical properties were studied both experimentally and using DFT methods (M06-2X and B3LYP). [ABSTRACT FROM AUTHOR]

The synthesis of bis-oxindoles via the copper(II)-mediated double cyclisation of linear bis-anilides is described. Cu(OAc) 2 ·H 2 O was identified as an efficient and inexpensive catalyst for this process. In contrast to previous methods, which rely on the synthesis of the central core from existing oxindole building blocks, this new approach focusses on concurrent formation of both oxindole rings from a simple linear precursor, allowing the formation of bis-oxindoles containing a diverse range of cyclic and acyclic linkers using a single synthetic method. [ABSTRACT FROM AUTHOR]

Organofluorine chemistry plays a key role in materials science, pharmaceuticals, agrochemicals, and medical imaging. However, the formation of new carbon-fluorine bonds with controlled regiochemistry and functional group tolerance is synthetically challenging. The use of metal complexes to promote fluorination reactions is of great current interest, but even state-of-the-art approaches are limited in their substrate scope, often require activated substrates, or do not allow access to desirable functionality, such as alkenyl C (sp2)-F or chiral C(sp3)-F centers. Here, we report the formation of new alkenyl and alkyl C-F bonds in the coordination sphere of ruthenium via an unprecedented outersphere electrophilic fluorination mechanism. The organometallic species involved are derived from nonactivated substrates (pyridine and terminal alkynes), and C-F bond formation occurs with full regio- and diastereoselectivity. The fluorinated ligands that are formed are retained at the metal, which allows subsequent metal-mediated reactivity. [ABSTRACT FROM AUTHOR]

Reaction of cis-[RuCl2(dppm)2]BF4 with TlBF4 and 1,4-diethynyl-benzenes results in the formation of the vinylidene cations trans-[Ru(=C=CH–C6H2-2,5-R2-4-C≡CH)Cl(dppm)2]+ (R = H, Me). Subsequent reaction with [NnBu4]Cl results in nucleophilic attack at the coordinated organic ligand, but not at the expected metal-bound carbon atom. Instead, trans-[Ru(C≡C–C6H2-2,5-R2-4-CCl=CH2)Cl(dppm)2] was generated which, when coupled with DFT calculations, provides evidence for an intermediate quinoidal cumulene complex. [ABSTRACT FROM AUTHOR]

Two novel succinimide-based palladium complexes, AsCat and FurCat, are highly efficient catalysts for room-temperature Stille cross-coupling of organostannanes with benzyl chlorides. The air- and moisture-stable catalysts are prepared in one step, and the coupling reactions proceed with a high selectivity for the benzyl position under mild conditions without the need for additives. [ABSTRACT FROM AUTHOR]

Reactionof the alkenyl-substituted carbene complex [Ru(κ2-O2CMe)(OC{Me}O(CCHCH2)(PPh3)2]+with PPh3resultsin the formation of the vinylidene-containing species [Ru(κ1-O2CMe)(κ2-O2CMe)(CCHCH2PPh3)(PPh3)2]+, among other products. This complex could also be obtained by reactionof [Ru(κ2-O2CR)(PPh3)2] (R = Me, Ph) with [HCCCH2PPh3]+although in this instance competitive formation of allene-containing[Ru(κ1-O2CR)(κ2-O2CR)(η2-H2CCCHPPh3)(PPh3)2] occurred. Reaction of [Ru(κ2-O2CMe)2(PPh3)2] with [H2CCCHPPh3]+gives this allene complex in a selective fashion. Similar resultswere obtained when [RhCl(PiPr3)2]2was used as the metal precursor. The reaction with [H2CCCHPPh3]+gave [RhCl(η2-H2CCCHPPh3)(PiPr3)2]+, whereas treatment with[HCCCH2PPh3]+afforded amixture of the same complex and [RhCl(η2-HCCCH2PPh3)(PiPr3)2]+, which subsequently isomerized to vinylidene-containing [RhCl(CCHCH2PPh3)(PiPr3)2]+via the alkynyl hydride complex [RhCl(H)(CCCH2PPh3)(PiPr3)2]+. Consistent with previous findings [HCCCH2PPh3]+isomerizes to [H2CCCHPPh3]+in the absence of a metal and the balance betweenthe vinylidene and allene complexes formed in these reactions appearsto relate to the efficiency of the reaction with each substrate. [ABSTRACT FROM AUTHOR]

The single crystal structure of five halogen-bonded co-crystals are reported, formed between para-hydrotetrafluoroiodobenzene and C4, C6, C8 and C10 stilbazoles as well as between C6 stilbazole and ortho- and meta-hydrotetrafluoroiodobenzene. Five of these co-crystals are formed from a 1 : 1 ratio of stilbazole to iodoaromatic, while in three cases, all with para-hydrotetrafluoroiodobenzene, a 2 : 1 stoichiometry is found. Halogen bond distances are between 2.795(2) and 2.877(3) Å, while the I…N–Cipso angle is between 160.22(6) and 174.9(1)°. The packing of these co-crystals is described and is discussed in relation to the efficient filling of space, leading to the conclusion that the halogen bond will adopt a non-ideal disposition to facilitate better solid-state packing. It is also shown that steric interactions between alkyl hydrogens and aromatic fluorines contribute to the determination of packing efficiency. Unexpectedly, in the case of the C6 stilbazole complexed by para-hydrotetrafluoroiodobenzene, there is a C–H…N hydrogen bond with an N…H separation of 2.273(2) Å. Non-linear halogen bonds lead to an unsymmetric disposition of the iodine with respect to the pyridyl ring leading to significant differences in non-covalent C…I distances, some of which can formally be considered as covalent. This unsymmetric approach of the C–I bond to the pyridyl ring is interpreted in relation to the sum of the forces governing formation of the unit cell. [ABSTRACT FROM AUTHOR]

Microcrystalline (∼1 μm) [Rh(Cy2PCH2CH2PCy2)(norbornadiene)][S-BArF4], [S-BArF4] = [B(3,5-(SF5)2C6H3)4]−, reacts with H2 in a single-crystal to single-crystal transformation to form the σ-alkane complex [Rh(Cy2PCH2CH2PCy2)(norbornane)][S-BArF4], for which the structure was determined by microcrystal Electron Diffraction (microED), to 0.95 Å resolution, via an on-grid hydrogenation, and a complementary single-crystal X-ray diffraction study on larger, but challenging to isolate, crystals. Comparison with the [BArF4]− analogue [ArF = 3,5-(CF3)2(C6H3)] shows that the [S-BArF4]− anion makes the σ-alkane complex robust towards decomposition both thermally and when suspended in pentane. Subsequent reactivity with dissolved ethene in a pentane slurry, forms [Rh(Cy2PCH2CH2PCy2)(ethene)2][S-BArF4], and the catalytic dimerisation/isomerisation of ethene to 2-butenes. The increased stability of [S-BArF4]− salts is identified as being due to increased non-covalent interactions in the lattice, resulting in a solid-state molecular organometallic material with desirable stability characteristics. [ABSTRACT FROM AUTHOR]

Abstract: Reaction of HCe:hsp sp="0.25" />=uracil) with [RhCl(PiPr3)2] results in the formation of the vinylidene complex [RhCl(PiPr3)2(h name="dbnd" />C{H}Ur)]. In the solid state this complex forms a hydrogen bonded network which consists of complementary interactions between uracil groups on neighbouring rhodium complexes and with the methanol of crystallisation. The η2-alkyne complexes [RhCl(PiPr3)2(η2-PhC [Rh(η5-C5H5)(PiPr3)(η2-PhCe also been prepared. In contrast to the behaviour of [Rh(η5-C5H5)(PiPr3)(η2-PhChCl(PiPr3)2(η2-PhCws little evidence for the formation of hydrogen bonded aggregates in solution. The difference in behaviour between the two species is rationalised on the basis of steric effects. [Copyright &y& Elsevier]

Abstract: Reaction of cis-[RuCl2(dppm)2] (dppm=1,2-bis(diphenylphosphino)methane) with PhCPF6 utilising methanol as solvent results in the formation of the η3-butenynyl complex [Ru(η3-PhCh name="sbnd" />Cm)2][PF6] in good yield. Similar reactions with Bu t C n Ced in the corresponding alkyl-substituted complexes and all three of these compounds have been characterised by NMR spectroscopy and X-ray crystallography. The mechanism of this reaction has been probed by employing labelling experiments with both PhCC 13CH allowing the identity of possible intermediates in the reaction to be determined. Furthermore, [Ru(η3-PhCh name="sbnd" />Cm)2][PF6] has been shown to be an effective regio- and stereo-selective catalyst for the dimerisation of PhC:italic>Z-PhCh name="sbnd" />CHhe absence of solvent. In contrast, no evidence for the formation of alkyne coupling was obtained from the reaction of cis-[RuCl2(dppe)2] (dppe=1,2-bis(diphenylphosphino)ethane) with PhCPF6. [Copyright &y& Elsevier]

Abstract: Cross-linking of ethylene propylene diene monomer (EPDM) rubbers containing different amounts of dicyclopentadiene (DCPD), 5-ethylidene-2-norbornene (ENB) and 5-vinyl-2-norbornene (VNB) dienes was examined by EPR spectroscopy. The cross-linking was initiated by thermal decomposition of dicumyl peroxide at 440K. The concentration of free radicals increased towards the end of the cross-linking process before reaching a maximum and decaying to zero. This is explained by the spatial confinement of the radicals in the cross-linked rubber, which leads to increased life time and, hence, higher radical concentration at a time when most peroxide has decomposed. The EPR spectra showed the presence of two components: a well-resolved spectrum overlapping a broad line. Both components are assigned to allyl radicals possessing different mobility. The more mobile component is assigned to allyl radicals along the EPDM chains, whereas the immobilised allyl radicals are formed in the cross-links. The stability of the allyl radicals decreases in the order DCPD>ENB>VNB. EPDMs containing two dienes show more persistent radicals than their single-diene counterparts. The most persistent radicals are observed for highly cross-linked (e.g., 28% ENB) or mixed diene EPDMs (e.g., 2.2% DCPD–4.4% ENB); the EPR spectra of free radicals in these systems can be observed for several hours. [Copyright &y& Elsevier]

Abstract: Reaction between 3-((1R,2R)-2-{[1-(3,5-di-tert-butyl-2-hydroxy-phenyl)-meth-(E)-ylidene]-amino}-cyclohexyl)-1-isopropyl-4-phenyl-3H-imidazol-1-ium bromide (1a) or the derivative 3-((1R,2R)-2-{[1-(2-hydroxy-5-nitro-phenyl)-meth-(E)-ylidene]-amino}-cyclohexyl)-1-isopropyl-4-phenyl-3H-imidazol-1-ium bromide (1b) and metal halides MCl x .yTHF (M=Zr, x =4, y =2; M=V, x = y =3; M=Cr, x = y =3), in THF, at −78°C gives the metal complexes of general formula [MCl x (κ2-N,O-OC6H2R1R2C(H)C6H10–Im)2][Br]2 (where M=Zr, x =2, R1 =R2 = t Bu, 2; M=Zr, x =2, R1 =H, R2 =NO2, 3; M=V, x =1, R1 =R2 = t Bu, 4; M=Cr, x =1, R1 =R2 = t Bu, 5; M=Fe, x =0, R1 =R2 = t Bu, 6; Im=1-isopropyl-4-phenyl-3H-imidazol-1-ium-3-yl). 1H and 13C NMR spectroscopy of 2 and 3 indicate κ2-N,O-ligand coordination via the phenoxy-imine moiety with pendant imidazolium salt that is corroborated by a single crystal structure of 6. Compounds 2, 3, 4 and 5 were tested as precatalysts for ethylene polymerisation in the presence of methylaluminoxane (MAO) cocatalyst, showing low activity. Selected polymer samples were characterised by GPC showing multimodal molecular weight distributions. [Copyright &y& Elsevier]

The scope and limitations of the organolithium-mediated conversion of β-methoxy N-tosyl aziridines derived from acyclic allylic alcohols into substituted allylic sulfonamides are described. [ABSTRACT FROM AUTHOR]

Abstract: The diastereoselective pot, atom and step economic (PASE) synthesis of highly functionalized piperidines has been realized. The procedure simply involves mixing methyl acetoacetate, 2equiv of aldehyde and 2equiv of aniline together in the presence of InCl3. In most cases the piperidine precipitates out of solution. [Copyright &y& Elsevier]

Abstract: Reaction between 9,9′-spirobifluorene and [CpM]+ (where M=Fe and Ru) equivalents gives the complexes [CpRu(η6-SBF)][PF6] (1), [(CpRu)2(η6,η6-SBF)][PF6]2 (2) and [(CpFe)2(η6,η6-SBF)][PF6]2 (3), respectively. Single crystal X-ray structures of 1 and 3 show that the metal atoms exhibit distorted η6-coordination to SBF phenyl moieties primarily as a consequence of steric interactions between Cp and SBF. The structure of 3 contains each of the possible C2 enantiomers whereas NMR spectroscopy shows signals consistent with a 1:1 mixture of C2 and C1 stereoisomers for both 2 and 3. In conjunction with electrochemical data the observations are consistent with SBF acting as a molecule containing two independent biphenyl moieties. [Copyright &y& Elsevier]

Abstract: The synthesis of monodentate and bidentate phosphinite ligands, possessing the unusual bicyclo[3.2.0]heptane framework, are reported. A convenient, tin-free synthesis of a key intermediate, namely 3-endo-6-endo-dihydroxybicyclo[3.2.0]heptane, is described. The air-sensitive phosphinite ligand 1 was either protected as the borane adduct, which is air-stable, or reacted directly with bis(acetonitrile)palladium(II)chloride to give the novel air and moisture stable palladium(II) complex 11. A platinum(II) relative 12 has also been synthesised by reaction of phosphinite 1 with bis(benzonitrile)platinum(II)chloride. Each complex has been thoroughly characterised and their molecular structures confirmed by X-ray diffraction studies. In catalytic applications, such as cross-coupling reactions of organometallic reagents with organohalides, an unexpectedly poor activity has been established for 11. For example, Suzuki–Miyaura cross-coupling of activated and deactivated aryl bromides with aryl boronic acids, in the presence of catalytic quantities of 11, proceed in low yield, accompanied by substantial homocoupling. Palladium agglomeration, to produce catalytically inactive Pd black, is rapid in these reactions, under both aqueous and non-aqueous conditions. The poor reactivity is proposed to arise through an unfavourable near tetrahedral ‘(PP′)Pd(0)’ geometry, which slows the oxidative addition step in the catalytic cycle with either activated or deactivated aryl halides. The steric bulk of the ligand and the associated large P–M–P′ bite angle, particularly at the palladium zero oxidation state, is proposed to account for the poor reactivity. However, we have established that cationic derivatives of 11 promote the cycloisomerisation of diallylmalonate in a regioselective fashion. [Copyright &y& Elsevier]

Two new inclusion compounds of 9,9′-spirobifluorene (SBF) incorporating benzene [(I), C25H16·C6H6] and biphenyl [(II), C25H16·C12H10], and a new polymorph of SBF [(III), C25H16] are reported. All three exhibit C—H…π(arene) hydrogen bonds between adjacent SBF molecules. Compound (II) also contains biphenyl C—H to SBF π-arene interactions. Collectively, hydrogen bonding gives rise to a chain and a layered motif in compounds (I) and (II), respectively. [ABSTRACT FROM AUTHOR]

This article reports the synthesis of two novel amino-acid derivatives in which the side chain of glutamic acid (Glu) is coupled with different amines – tert-butylamine (ligand A) or a first generation `Newkome'' type dendron (ligand B). Consequently, ligand B possesses a bulkier branch than ligand A. Ligands A and B bind Cu2+ ions in solution, generating copper complexes A–Cu (Mr=508) and B–Cu (Mr=1077). These complexes were fully characterised and, in particular, have been investigated by electrochemical and electron spin resonance techniques to determine the extent of encapsulation of the copper ions. There were significant differences between the two complexes, indicating that Cu2+ may be more deeply encapsulated by ligand B and hence less able to interact with its surroundings. This indicates that metal ions can be sensitive reporters of even relatively small amounts of organic functionality, and emphasises the important role which protein superstructures can play in modulating the function of active metal ions. [Copyright &y& Elsevier]

A Pd-mediated direct C–H bond functionalisation of tryptophan has been developed, both as a single amino acid residue and within peptides. Important mechanistic insight into this process has been gained by characterising a Pd catalytically competent nanoparticle phase which evolves during the early stages of reaction. [ABSTRACT FROM AUTHOR]

"GaOTf" is a simple, convenient source of low‐valent gallium for synthetic chemistry and catalysis. However, little is currently known about its composition or reactivity. In this work, 71Ga NMR spectroscopy shows the presence of [Ga(arene)n]+ salts on oxidation of Ga metal with AgOTf in arene solvents. However, a more complex picture of speciation is uncovered by X‐ray diffraction studies. In all cases, mixed‐valence compounds containing Ga‐arene and Ga‐OTf coordination motifs, in addition to an unusual "naked" [Ga]+ ion, are found. Addition of 18‐crown‐6 allows for the isolation of a discrete GaI crown complex. Evidence of a potential intermediate in the formation of "GaOTf" has been isolated in the form of the bimetallic silver(I)/gallium(I) cluster anion [Ag4{Ga(OTf)3}4(μ‐Ga)6(OTf)4]2−. [ABSTRACT FROM AUTHOR]

"GaOTf" is a simple, convenient source of low‐valent gallium for synthetic chemistry and catalysis. However, little is currently known about its composition or reactivity. In this work, 71Ga NMR spectroscopy shows the presence of [Ga(arene)n]+ salts on oxidation of Ga metal with AgOTf in arene solvents. However, a more complex picture of speciation is uncovered by X‐ray diffraction studies. In all cases, mixed‐valence compounds containing Ga‐arene and Ga‐OTf coordination motifs, in addition to an unusual "naked" [Ga]+ ion, are found. Addition of 18‐crown‐6 allows for the isolation of a discrete GaI crown complex. Evidence of a potential intermediate in the formation of "GaOTf" has been isolated in the form of the bimetallic silver(I)/gallium(I) cluster anion [Ag4{Ga(OTf)3}4(μ‐Ga)6(OTf)4]2−. [ABSTRACT FROM AUTHOR]

The crystal structure of [Al(tBu-salen)]2O·HCl shows major changes compared to that of [Al(tBu-salen)]2O. The additional proton is localized on the bridging oxygen atom, making the aluminium atoms more electron deficient. As a result, a water molecule coordinates to one of the aluminium atoms, which becomes six-coordinate. This pushes the salen ligand associated with the six-coordinate aluminium ion closer to the other salen ligand and results in the geometry around the five-coordinate aluminium atom becoming more trigonal bipyramidal. These results experimentally mirror the predications of DFT calculations on the interaction of [Al(tBu-salen)]2O and related complexes with carbon dioxide. Variable temperature NMR studies of protonated [Al(tBu-salen)]2O complexes revealed that the structures were dynamic and could be explained on the basis of an intramolecular rearrangement in which the non-salen substituent of a five-coordinate aluminium(tBu-salen) unit migrates from one face of a square based pyramidal structure to the other via the formation of structures with trigonal bipyramidal geometries. Protonated [Al(tBu-salen)]2O complexes were shown to have enhanced Lewis acidity relative to [Al(tBu-salen)]2O, coordinating to water, dioxane and 1,2-epoxyhexane. Coordinated epoxyhexane was activated towards ring-opening, to give various species which remained coordinated to the aluminium centers. The protonated [Al(tBu-salen)]2O complexes catalysed the synthesis of cyclic carbonates from epoxides and carbon dioxide both in the presence and absence of tetrabutylammonium bromide as a nucleophilic cocatalyst. The catalytic activity was principally determined by the nature of the nucleophilic species within the catalyst structure rather than by changes to the Lewis acidity of the metal centers. [ABSTRACT FROM AUTHOR]