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A novel chloride carbodiimide, K12Pb51(CN2)30Cl54 (1), was successfully synthesized by solid state metathesis reaction. It exhibits the longest unit cell value reported among all known carbodiimides, caused by the superhelical configuration of the stereochemically active lone pair (SALP) Pb2+ cations rotating along the c axis. In addition, 1 has a large birefringence of 0.094 at 1064 nm resulting from the synergistic effect of SALP Pb2+ cations and linear (CN2)2− groups based on first principles calculation.

The dimeric β-diketiminato magnesium hydride, [(BDI)MgH]2, reacts at 80 °C with the terminal alkenes, 1-hexene, 1-octene, 3-phenyl-1-propene and 3,3-dimethyl-butene to provide the respective n-hexyl, n-octyl, 3-phenylpropyl and 3,3-dimethyl-butyl magnesium organometallics. The facility for and the regiodiscrimination of these reactions are profoundly affected by the steric demands of the alkene reagent. Reactions with the phenyl-substituted alkenes, styrene and 1,1-diphenylethene, require a more elevated temperature of 100 °C with styrene providing a mixture of the 2-phenylethyl and 1-phenylethyl products over 7 days. Although the reaction with 1,1-diphenylethene yields the magnesium 1,1-diphenylethyl derivative as the sole reaction product, only 64% conversion was achieved over a 21 day timeframe. Reactions with the α,ω-dienes, 1,5-hexadiene and 1,7-octadiene, provided divergent results. The initial 5-alkenyl magnesium reaction product of the shorter chain diene undergoes 5-exo-trig cyclisation via intramolecular carbomagnesiation to provide a cyclopentylmethyl derivative, which was shown by X-ray diffraction analysis to exist as a three-coordinate monomer. In contrast, 1,7-octadiene provided a mixture of two compounds, a magnesium oct-7-en-1-yl derivative and a dimagnesium-octane-1,4-diide, as a result of single or two-fold activation of the terminal C[double bond, length as m-dash]C double bonds. The magnesium hydride was unreactive towards internal alkenes apart from the strained bicycle, norbornene, allowing the characterisation of the resultant three-coordinate magnesium norbornyl derivative by X-ray diffraction analysis. Computational analysis of the reaction between [(BDI)MgH]2 and 1-hexene using density functional theory (DFT) indicated that the initial Mg-H/C[double bond, length as m-dash]C insertion process is rate determining and takes place at the intact magnesium hydride dimer. This exothermic reaction (ΔH = -14.1 kcal mol-1) traverses a barrier of 18.9 kcal mol-1 and results in the rupture of the dinuclear structure into magnesium alkyl and hydride species. Although the latter three-coordinate hydride derivative may be prone to redimerisation, it can also provide a further pathway to magnesium alkyl species through its direct reaction with a further equivalent of 1-hexene, which occurs via a lower barrier of 15.1 kcal mol-1. This Mg-H/C[double bond, length as m-dash]C insertion reactivity provides the basis for the catalytic hydrosilylation of terminal alkenes with PhSiH3, which proceeds with a preference for the formation of the anti-Markovnikov organosilane product. Further DFT calculations reveal that the catalytic reaction is predicated on a sequence of Mg-H/C[double bond, length as m-dash]C insertion and classical Si-H/Mg-C σ-bond metathesis reactions, the latter of which, with a barrier height of 24.9 kcal mol-1, is found to be rate determining.

Grubbs catalysts are described as a useful alternative to promote intramolecular carbene C-H insertion from α-diazoesters. Moreover, no competition arises from the possible metathesis reactions on substrates bearing alkene and alkyne moieties. DFT calculations were also carried out to gain insight into the reaction mechanism involved in these transformations.

The KCl-bridged phosphinidiide thorium metallocene, {[η5-1,3-(Me3C)2C5H3]2Th(P-2,4,6-iPr3C6H2)(ClK)}2 (2), was isolated in good yield by a salt metathesis reaction of the thorium methyl chloride compound [η5-1,3-(Me3C)2C5H3]2Th(Cl)Me (1) with 2,4,6-iPr3C6H2PHK in toluene. Furthermore, it was fully characterized including its molecular structure. The reactivity of 2 towards various small organic molecules was also explored, e.g., it reacts with alkynes, nitriles, CS2, quinolines, silanes, pyridine and imidazole derivatives, resulting in metallacycles, imidos, carbodithiolates, and phosphido compounds. Density functional theory (DFT) computations were conducted to supplement the experimental investigations.

Complexes of divalent ytterbium (1) and europium (2) with a dianionic o-amidophenolate ligand were prepared by both the direct reduction of 4,6-di-tert-butyl-N-(2,6-diisopropylphenyl)-o-iminobenzoquinone (dpp-IQ) and the salt metathesis reaction of potassium o-amidophenolate with LnI2 (Ln = Yb, Eu). Oxidation of o-amidophenolates 1, 2 with one equivalent of dpp-IQ as well as the salt metathesis reaction of potassium o-iminosemiquinolate with LnI2 afforded ligand mixed-valent o-iminosemiquinonato-amidophenolato complexes of trivalent ytterbium (3) and europium (4). All novel complexes 1-4 were fully characterized, including the solid state structures of 1 and 2 determined by single crystal X-ray diffraction. The magnetic properties of paramagnetic 2-4 were examined.

This work provides new routes for the conversion of U(iv) into U(vi) bis(imido) complexes and offers new information on the manner in which the U(vi) compounds form. Many compounds from the series described by the general formula U(NR)2(EPh)2(L)2 (R = 2,6-diisopropylphenyl, tert-butyl; E = S, Se, Te; L = py, EPh) were synthesized via oxidation of an in situ generated U(iv) amido-imido species with Ph2E2. This synthetic sequence provides a general route into bis(imido) U(vi) chalcogenolate complexes, circumventing the need to perform problematic salt metathesis reactions on U(vi) iodides. Investigation into the speciation of the U(iv) complexes that form prior to oxidation found a significant dependence on the identity of the ancillary ligands, with tBu2bpy forming the isolable imido-(bis)amido complex, U(NDipp)(NHDipp)2(tBu2bpy)2. Together, these data are consistent with the view that the bis(imido) U(vi) motif - much like the uranyl ion, UO22+- is a thermodynamic sink into which simple ligand frameworks are unable to prevent uranium from falling when in the presence of a suitable retinue of imido proligands.

A high-temperature metathesis reaction between CuBr and [Ph4P]2MSe4 (M = Mo or W) gave rise to nanocrystalline Cu2MSe4 with a phase-pure M = Mo compound that was obtained for the first time. After exploring the formation mechanism, we found that the sub-stoichiometric ratios of CuBr to MSe42- resulted in the formation of a linear byproduct impurity, [Ph4P]CuMSe4 (M = Mo or W). However, excess CuBr selectively steered the reaction to the desired Cu2MSe4. As a consequence of the newfound similarity in the reaction conditions for both metals, we have demonstrated the applicability of this method towards a mixed Mo/W quaternary composition.

Triphosphanes R′2PP(R)PR′2 (9a,c: R = Py; 9b R = BTz), 1,3-diphenyl-2-pyridyl-triphospholane 9d and pentaphospholanes (RP)5 (13: R = Py; 18: R = BTz) are obtained in high yield of up to 98% from the reaction of dipyrazolylphosphanes RPpyr2 (5: R = Py; 6: R = BTz; pyr = 1,3-dimethylpyrazolyl) and the respective secondary phosphane (R′2PH, R′ = Cy (9a,b), tBu (9c); PhPH(CH2)2PHPh (9d)). The formation of derivatives 9a–d proceeds via a condensation reaction while the formation of 13 and 18 can only be explained by a selective scrambling reaction. We realized that the reaction outcome is strongly solvent dependent as outlined by the controlled scrambling reaction pathway towards pentaphospholane 13. In our further investigations to apply these compounds as ligands we first confined ourselves to the coordination chemistry of triphosphane 9a with respect to coinage metal salts and discussed the observation of different syn- and anti-isomeric metal complexes based on NMR and X-ray analyses as well as quantum chemical calculations. Methylation reactions of 9a with MeOTf yield triphosphan-1-ium Cy2MePP(Py)PCy2+ (10+) and triphosphane-1,3-diium Cy2MePP(Py)PMeCy22+ (112+) cations as triflate salts. Salt 11[OTf]2 reacts with pentaphospholane 13 in an unprecedented chain growth reaction to give the tetraphosphane-1,4-diium triflate salt Cy2MePP(Py)P(Py)PMeCy22+ (19[OTf]2) via a P–P/P–P bond metathesis reaction. The latter salt is unstable in solution and rearranges via a rare [1,2]-migration of the Cy2MeP-group followed by the elimination of the triphosph-2-en-1-ium cation [Cy2MePPPMeCy2]+ (20+) to yield a novel 1,4,2-diazaphospholium salt (21[OTf]).

Catalytic carbonyl-olefin metathesis reactions have recently been developed as a powerful tool for carbon-carbon bondformation. However, currently available synthetic protocols rely exclusively on aryl ketone substrates while the corresponding aliphatic analogs remain elusive. We herein report the development of Lewis acid-catalyzed carbonyl-olefin ring-closing metathesis reactions for aliphatic ketones. Mechanistic investigations are consistent with a distinct mode of activation relying on the in situ formation of a homobimetallic singly-bridged iron(III)-dimer as the active catalytic species. These “superelectrophiles” function as more powerful Lewis acid catalysts that form upon association of individual iron(III)-monomers. While this mode of Lewis acid activation has previously been postulated to exist, it has not yet been applied in a catalytic setting. The insights presented are expected to enable further advancement in Lewis acid catalysis by building upon the activation principle of “superelectrophiles” and broaden the current scope of catalytic carbonyl-olefin metathesis reactions.

The carbonyl–olefin metathesis reaction could facilitate rapid functional group interconversion and allow construction of complicated organic structures. Herein, we demonstrate that elemental iodine, a very simple catalyst, can efficiently promote this chemical transformation under mild reaction conditions. Our mechanistic studies revealed intriguing aspects of the activation mode via molecular iodine and the iodonium ion that could change the previously established perception of catalyst and substrate design for the carbonyl–olefin metathesis reaction.

Several pnictogen dihalide complexes of the type (WCA-IDipp)EX2 (E=P, As, Sb; X=Cl, Br) that bear an anionic N-heterocyclic carbene ligand with a weakly coordinating borate moiety (WCA-IDipp, WCA=B(C6 F5 )3 , IDipp=1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) were prepared by salt metathesis reactions between the respective pnictogen trihalides EX3 and the lithium salt (WCA-IDipp)Li⋅toluene. Two-electron reduction of the dihalides (WCA-IDipp)EX2 with 1,3-bis(trimethylsilyl)-1,4-dihydropyrazine or elemental magnesium afforded the dipnictenes (WCA-IDipp)2 E2 , which display typical element-element double bonds as observed in diaryldiphosphenes, -arsenes and -stibenes. To provide an insight into the factors contributing to the structural stability of the pnictogen dihalide and dipnictene compounds, quantum chemical calculations were performed at the domain-based local pair natural orbital coupled-cluster (DLPNO-CCSD(T)) level. A local energy decomposition (LED) analysis of the interaction between the carbene and the pnictogen dihalide or dipnictene moiety demonstrates that London dispersion is an essential factor for the stabilization of these compounds.

In this experiment, students are asked to conduct a catalytic cross-metathesis experiment and compare this reaction to the Wittig reaction within the confines of green chemistry. Students synthesize stilbene from styrene using Grubbs second-generation catalyst. Products can be minimally characterized by IR spectroscopy and melting point, but using 1H NMR spectroscopy is preferred. Students find that the Wittig reaction is selective for cis-stilbene while the metathesis reaction produces >98% trans-stilbene. Students determine the cis/trans selectivity, turnover number, and maximum turnover frequency of the reaction. The experiment is conducted alongside the synthesis of stilbene using Wittig chemistry from a published procedure.

A borane B(C6 F5 )3 -catalyzed metathesis reaction between the Si-C bond in the cyclic (alkyl)(amino)germylene (CAAGe) 1 and the Si-H bond in a silane (R3 SiH; 2) is reported. Mechanistic studies propose that the initial step of the reaction involves Si-H bond activation to furnish an ionic species [1-SiR3 ]+ [HB(C6 F5 )3 ]- , from which [Me3 Si]+ [HB(C6 F5 )3 ]- and an azagermole intermediate are generated. The former yields Me3 SiH concomitant with the regeneration of B(C6 F5 )3 whereas the latter undergoes isomerization to afford CAAGes bearing various silyl groups on the carbon atom next to the germylene center. This strategy allows the straightforward synthesis of eight new CAAGes starting from 1. Ministry of Education (MOE) Nanyang Technological University Accepted version We are grateful to the Nanyang Technological University (NTU) and Ministry of Education, Singapore (MOE2015-T1-001-029:RG9/15) for financial support. We also like to thank Dr. Li Yongxin (NTU) for assistance in X-ray crystallographic analysis.

Herein, we report on fluorophore-tagged Grubbs catalysts as turn-on fluorescent probes for the sensitive detection and quantitation of ethylene, a plant hormone that plays a critical role in many phases of plant growth and fruit ripening. The ruthenium-based weak fluorescent probes were prepared handily through the metathesis reaction between the first-generation Grubbs catalyst and selected fluorophores that have high quantum yields and contain terminal vinyl groups. Upon exposure to ethylene, fluorescence enhancement was observed via the release of fluorophore from the probe. Our probe shows an excellent limit of detection for ethylene at 0.9 ppm in air and was successfully applied for monitoring ethylene released during the fruit-ripening process. Our work opens up a new avenue of application of Grubbs catalysts for bioanalytical chemistry of ethylene, which is critically important in plant biology, agriculture, and food industry.

International audience; New platforms for trinuclear complexes, 1,3,5-tris(fluoren-2-yl-R)benzene (Ph{2-FluRH}3; R = H (2a), 6-tBu (2b), 7-tBu (2c), Tet (2d) (Tet = 2,2,5,5-tetramethyl-tetrahydrobenzofluorene), were synthesized via an acid-catalyzed cyclotrimerization of the corresponding substituted 2-acetylfluorenes. Subsequent nucleophilic addition of the [Ph{2-FluR}3]3− trianions onto 6,6,-dimethylfulvene afforded the corresponding isopropylidene-bridged pro-ligands Ph{Me2C(2-FluRH)(C5H5)}3 (3a-d). Discrete trinuclear tris(dichloro-ansa-zirconocene and hafnocene), Ph[{Me2C(2-FluR)(C5H4)}MX2]3 (X = Cl 4b-d-Zr, 4c,d-Hf) were prepared by salt metathesis reactions. Some zirconium complexes were further alkylated towards the corresponding tris(dialkyls) (X = Me 5c,d-Zr; X = CH2SiMe3 6c-Zr). The structures of these metal complexes were determined by elemental analyses, and by 1D, inverse 2D heteronuclear correlation, and DOSY NMR spectroscopy, as well as by theoretical computations. Those studies revealed the existence of two isomers, of C3 and C1 symmetry respectively, originating from the mutual orientation of the three ansa-metallocene fragments. Preliminary studies on the catalytic performances of the dichloro complexes, upon activation with MAO, in ethylene and propylene homopolymerization and ethylene/1-hexene copolymerization were carried out and compared to those of the monometallic analogues under identical conditions.

By combining the diphosphanes Ar2P–PAr2, where Ar = C6H5, 4-C6H4Me, 4-C6H4OMe, 3,5-C6H3(CF3)2, it has been shown that P,P-metathesis generally occurs rapidly under ambient conditions. DFT calculations have shown that the stability of unsymmetrical diphosphanes Z2P–PZ′2 is a function of the difference between the Z and Z′ substituents in terms of size and electronegativity. Of the mechanisms that were calculated for the P,P-metathesis, the most likely was considered to be one involving Ar2P˙ radicals. The observations that photolysis increases the rate of the P,P-metatheses and TEMPO inhibits it, are consistent with a radical chain process. The P,P-metathesis reactions that involve (o-Tol)2P–P(o-Tol)2 are anomalously slow and, in the absence of photolysis, were only observed to take place in CHCl3 and CH2Cl2. The role of the chlorinated solvent is ascribed to the formation of Ar2PCl which catalyses the P,P-metathesis. The slow kinetics observed with (o-Tol)2P–P(o-Tol)2 is tentatively attributed to the o-CH3 groups quenching the (o-Tol)2P˙ radicals or inhibiting the metathesis reaction sterically.

Two “Mo2O2S2”-based complexes with phosphinoyldithioformate ligands were synthesized from the metathesis reaction of [R2P(O)CS2]− with (Me4N)2[Mo2O2(µ-S)2(Cl)4] to give [Mo2O2(µ-S)2{R2P(O)CS2}2] (1, R = Ph, 2, R = Bn). The complexes were fully characterized, including the X-ray crystal structure for 1. Variable temperatures 31P NMR of 1 and 2 exhibit non-rigid behavior in solution where three and two coordination isomers were present, respectively. The organic substituent on the P atom greatly impacts the complex non-rigid properties and behavior. The catalytic activity of 1 and 2 towards sulfur atom transfer (SAT) using propylene sulfide and cyclohexene sulfide was explored, employing homogeneous reaction conditions at an ambient temperature on the NMR scale. The complexes showed distinctly different properties along with high conversions in short reaction times. A catalytic cycle consistent with the results is proposed.

Phosphorus(v) sulfide and Lawesson's reagent are commonly used thionating reagents which are considered to operate after dissociation into highly reactive dithiophosphorane fragments. We report the synthesis and properties of a monomeric thiophosphonium ion [R2P[double bond, length as m-dash]S]+. The highly electrophilic species reacts with carbonyls in oxo-for-sulfido exchange reactions at room temperature and undergoes phosphorus-chalcogen bond metathesis reactions with phosphine chalcogenides.

Planar-chiral transition metal complexes are useful chiral auxiliaries in organic and organometallic chemistry, and they have been utilized as chiral ligands, chiral catalysts, or chiral building blocks, etc. Despite the importance of such planar-chiral species in asymmetric synthesis, their preparation in optically active forms is still a challenging problem. Indeed, reported examples of catalytic enantioselective synthesis of planar-chiral complexes have been rare, and this has been a developing area in this field. In this personal account, recent results from our research group on the catalytic asymmetric synthesis of various planar-chiral transition metal complexes are summarized. The asymmetric ring-closing metathesis reactions catalyzed by the well-defined molybdenum-alkylidene species are powerful methods to control the planar chirality in ferrocenes, ruthenocenes, (η6 -arene)chromium complexes, and (η5 -cyclopentadienyl)manganese(I) complexes. Application of the enantiomerically enriched complexes obtained by our methods is described as well.

The successive auration of p‐tert‐butyltetramercaptotetrathiacalix[4]arene, H4(MTC[4]), with gold(I) phosphine units was investigated. Through deprotonation with NaOMe, followed by salt metathesis reactions with (PR3)AuCl (R=Me, Ph) complexes with two and three [(PR3)Au]+ moieties could be prepared and isolated, namely [(Ph3PAu)2H2(MTC[4])] and [(Me3PAu)3H(MTC[4])]. In [(Me3PAu)3H(MTC[4])] two gold atoms already come close enough to undergo aurophilic interactions. To introduce a fourth [(PR3)Au]+ entity TlOEt had to be used for the deprotonation, which led to the finding that four gold atoms organised by the (MTC[4])4− coordination platform are able to bind and stabilize a TlCl entity, yielding [(Me3PAu)4TlCl(MTC[4])]. As evidenced by structural and theoretical investigations the binding occurs through strong metallophilic interactions, which lead to photoluminescence at low temperatures., p‐tert ‐Butyltetramercaptotetrathiacalix[4]arene was used as a coordination platform to synthesize and investigate gold(I) complexes with varying nuclearity. Aiming at the corresponding tetranuclear complex through salt metathesis it was found capable of binding a neutral, molecular TlCl entity by metallophilic interactions, as shown by structural and theoretical investigations. These Interactions lead to photoluminescence at low temperatures (see figure).

Olefin metathesis, a powerful synthetic method with numerous practical applications, can be improved by developing heterogeneous catalysts that can be recycled. In this study, a single-stage process for the entrapment of ruthenium-based catalysts was developed by the sol–gel process. System effectiveness was quantified by measuring the conversion of the ring-closing metathesis reaction of the substrate diethyl diallylmalonate and the leakage of the catalysts from the matrix. The results indicate that the nature of the precursor affects pore size and catalyst activity. Moreover, matrices prepared with tetraethoxysilane at an alkaline pH exhibit a better reaction rate than in the homogenous system under certain reaction conditions. To the best of our knowledge, this is the first study to present a one-step process that is simpler and faster than the methods reported in the literature for catalyst entrapment by the sol–gel process under standard conditions.

Porous organic frameworks have shown a number of promising properties; however, their industrial application is usually hampered due to the lability of their linkages (imine, boroxine, etc.). Inspired by the outstanding chemical, mechanical and thermal resistance of the 1D polymer polyphenylene sulfide (PPS), we hypothesized that 2D and 3D poly-arylthioether frameworks would merge the attractive features common to porous frameworks and PPS in a single material. Herein, we report a Pd-catalysed C–S/C–S metathesis-based method to prepare new porous poly-arylthioether frameworks in good yields. The self-correcting nature of the process has enabled the synthesis of new, robust materials with high surface areas. Despite the frameworks’ extreme resistance to harsh chemicals, they can be fully recycled to recover the original building blocks using the same catalytic reaction. In addition, we demonstrate preliminary results showing that these materials have great potential in several environmentally relevant applications including metal capture, metal sensing and heterogeneous catalysis. In a broader context, these results clearly demonstrate the untapped potential of emerging single-bond metathesis reactions in the preparation of new materials.

The in-depth knowledge of lipid biological functions calls for a comprehensive lipid structure annotation that implies implementing a method to locate fatty acids unsaturations. To address this challenge we have associated Grubbs' cross metathesis reaction and liquid chromatography hyphenated to tandem mass spectrometry. The pretreatment of lipids containing samples by Grubbs' catalyst and an appropriate alken generates substituted lipids through cross-metathesis reaction under mild, chemoselective and highly reproducible conditions. A systematic LC-MS/MS analysis of the reaction mixture allows locating unambigouslt the double bounds in fatty acid side chains. This method has en successfully applied at a nanomole scale to commerical standard mixtures as well as in lipid extracts from an in vitro model of corneal toxicity.

The bismuth dichloride complex (WCA-IDipp)BiCl2, which bears an anionic N-heterocyclic carbene ligand with a weakly coordinating borate moiety (WCA-IDipp, WCA = B(C6F5)3, IDipp = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene), was prepared by salt metathesis reaction between BiCl3 and the lithium salt (WCA-IDipp)Li·toluene. Subsequent two-electron reduction with 1,4-bis(trimethylsilyl)-1,4-dihydropyrazine afforded the dibismuthene (WCA-IDipp)2Bi2, which displays a bismuth-bismuth double bond.

A general approach for the synthesis of covalent and ionic amine borane complexes containing trinitromethyl fragments has been developed through metathesis reactions between amine chloroborane complexes and potassium salt of trinitromethyl (K[C(NO2)3]). Five covalent and ionic trinitromethyl amine borane complexes have been synthesized in good yields with high purity and it is found that the ionic complex, [H2B(NH3)2][C(NO2)3], might be a promising energetic material on the basis of the investigation of its thermal decomposition behaviour.

Polythiourethanes (PTUs) crosslinked with dynamic disulfide bonds are synthesized via a nonisocyanate approach. First, a difunctional five-membered cyclic trithiocarbonate (1) is synthesized via the reaction of diglycidyl ether of bisphenol A (DGEBA) with carbon disulfide (CS2 ). Thereafter, the step-growth polymerizations of 1 with α,ω-diamino poly(propylene oxide)s with various molar masses are carried out to obtain a series of linear poly(mercapto thiourethane)s. These linear poly(mercapto thiourethane)s are readily crosslinked upon formation of disulfide bonds, which are generated via radical coupling reaction with the side mercapto groups. These crosslinked PTUs can be tailored into the materials from thermosetting plastics to crosslinked elastomers, depending on the molar masses of α,ω-diamino poly(propylene oxide)s. More importantly, these crosslinked PTUs display excellent reprocessing properties at elevated temperatures, which is attributable to the metathesis reaction of dynamic disulfide bonds.

A variety of ene-yne cross metathesis reactions were performed using unsaturated phosphonate and phosphate reagents, affording the corresponding phosphorylated 1,3-diene products in good to excellent yields. These difficult ene-yne metatheses employed a Grubbs catalyst bearing a cyclic amino alkyl carbene ligand. A variety of terminal alkynes of varying substitution underwent the reaction, and different phosphorus-containing alkenes were found to give the conjugated diene products in high yields. The resulting dienes were further transformed by Horner-type Wittig reactions and a Diels-Alder cycloaddition.

Metathesis reactions are one of the most reliable and prevalent ways of creating a C– C bond in synthesis. Photochemical variants exist, and they have proven extremely useful for the construction of complex molecules, from natural products to Möbius rings. A variety of starting materials can undergo photometathesis reactions, including alkenes, alkynes, carbonyls, thiocarbonyls, and ketenes. While many of these reactions proceed with UV light and require harsh conditions, a handful of new techniques for visible-light photometathesis reactions have appeared recently. Given the current developments in visible-light photocatalysis, we believe that many more visible light photometathesis reactions await discovery. In this first review on the subject of photometathesis, we have gathered the relevant literature to give the reader an in-depth understanding of the field, and to inspire further development and synthetic application of these fascinating reactions.

Herein, we report the synthesis and interfacial properties of cholesterol based biocompatible surface-active biosurfactant choline cholate (CC) and choline deoxy cholate (CDC) surfactants, prepared through salt metathesis reaction. The surface activity and aggregation behavior of these surfactants were investigated by surface tension measurements and small angle X-ray scattering (SAXS) technique. CC and CDC both formed well-defined micelles with distinct CMC values as indicated by tensiometry, while the SAXS patterns can be well described by the polydisperse ellipsoid model. Furthermore, it was observed that both CC and CDC showed good foamability ascribed to the foam film rigidity which could be highly beneficial. Also, CC and CDC showed sphere-to rod micellar transition in the presence of CTAB. The study reported here may prove to be highly beneficial for pharmaceutical and personal care product formulations.

While metathesis reactions involving carbon–carbon double bonds, namely olefin metathesis, have been well established with broad utility in organic synthesis and materials science, direct metathesis of kinetically less accessible C–C single bonds is extremely rare. Here we report a ruthenium-catalysed reversible C–C single-bond metathesis reaction that allows redox- and pH-neutral biaryl synthesis. Assisted by directing groups, unstrained homo-biaryl compounds undergo aryl exchanges to generate cross-biaryl products, catalysed by a well-defined air-stable ruthenium(II) complex. Functional groups reactive under typical cross-coupling reactions, such as halogen, silyl and boronate moieties, are compatible under the metathesis conditions. Mechanistic studies disclose an intriguing ‘olefin-metathesis-like’ pathway that involves an unexpected heptacoordinated, 18-electron closed-shell intermediate. The distinct reaction mode discovered here is expected to inspire the development of more general C–C single-bond metathesis and orthogonal cross-coupling reactions. Metathesis reactions involving carbon–carbon double bonds have been well established, but direct metathesis of carbon–carbon single bonds is extremely rare. Now, a ruthenium-catalysed carbon–carbon single-bond metathesis reaction has been developed with unstrained homo-biaryl substrates. The reaction shows wide functional group tolerance and operates via an ‘olefin-metathesis-like’ mechanism.

The development of an asymmetric ‘clip-cycle’ synthesis of 2,2- and 3,3-disubstituted pyrrolidines and spiropyrrolidines, which are increasingly important scaffolds in drug discovery programs, is reported. Cbz-protected bis-homoallylic amines were activated by ‘clipping’ them to thioacrylate via an al-kene metathesis reaction. Enantioselective intramolecular aza-Michael cyclisation onto the activated alkene, catalyzed by a chiral phosphoric acid, formed a pyrrolidine. The reac-tion accommodated a range of substitution to form 2,2- and 3,3-disubstituted pyrrolidines and spiropyrrolidines with high enantioselectivities. The importance of the thioester activating group was demonstrated by comparison to ke-tone and oxoester-containing substrates. DFT studies sup-ported the aza-Michael cyclisation as the rate and stereo-chemical determining step, and correctly predicted the for-mation of the major enantiomer. The catalytic asymmetric syntheses of N-methyl pyrrolidine alkaloids (R)-irnidine and (R)-bgugaine, which possess DNA binding and antibacterial properties were achieved using the ‘clip-cycle’ methodology.

We report the synthesis of bolaamphiphilic alkenyl phosphonic acid (BPC12) through the olefin crossmetathesis reaction of vinylphosphonic acid with 1,11-dodecadiene in the presence of a Ru-carbene catalyst. BPC12 possesses two trans-P-C=C moieties and is thus readily soluble in water up to 3.4 g L-1, as confirmed by 1H nuclear magnetic resonance (NMR) measurements. Surface tension measurements revealed that BPC12 reduced the surface tension of water from 72.0 to 47.0 mN m‒1. The occupied area per molecule at the air/water interface (A) of BPC12 (216 A2) was ten times larger than that of dodecenyl phosphonic acid PC12 (23 A2). Moreover, dynamic light scattering measurement of an aqueous BPC12 solution (5 mM) revealed the formation of large aggregates with an average diameter of 81.8±27.0 nm.

We designed and synthesized helical short oligopeptides with an L-proline on the N-terminus and hydrocarbon stapling on the side chain. Side-chain stapling is a frequently used method for the development of biologically active peptides. Side-chain stapling can stabilize the secondary structures of peptides, and, therefore, stapled peptides may be applicable to peptide-based organocatalysts. Olefin-tethered cis-4-hydroxy-L-proline 1 and L-serine 2 and 8, and (R)-&alpha, allyl-proline 18 were used as cross-linking motifs and incorporated into helical peptide sequences. The Z- and E-selectivities were observed for the ring-closing metathesis reactions of peptides 3 and 11 (i,i+1 series), respectively, while no E/Z-selectivity was observed for that of 19 (i,i+3 series). The stapled peptide B&rsquo, catalyzed the Michael addition reaction of 1-methylindole to &alpha, &beta, unsaturated aldehyde, which was seven times faster than that of unstapled peptide B. Furthermore, the high catalytic activity was retained even at lower catalyst loadings (5 mol %) and lower temperatures (0 &deg, C). The circular dichroism spectra of stapled peptide B&rsquo, showed a right-handed helix with a higher intensity than that of unstapled peptide B. These results indicate that the introduction of side-chain stapling is beneficial for enhancing the catalytic activity of short oligopeptide catalysts.

Bifunctional silsesquioxanes create an attractive group of compounds with a wide range of potential applications, and recently they have gained much interest. They are known to be obtained mainly via hydrosilylation, but we disclose novel synthetic protocols based on different but complementary reactions, i.e., cross-metathesis (CM) and silylative coupling (SC). A series of cubic T8 type silsesquioxane derivatives with a broad scope of styryl substituents were synthesized in a one-pot procedure and characterized by spectroscopic and spectrometric methods. All of the new compounds can be obtained in a one-pot manner, which has an attractive impact on the synthetic procedure, as it is economic in terms of the isolation of intermediate products. Additionally, the methodology disclosed here enables the (E)-stereoselective introduction of styrenes derivative to the cubic T8 type core. The presented compounds can be interesting precursors for a further functionalization that may significantly increase the possibility of their application in the design and synthesis of new functional materials.

A new organocatalyzed fluoride metathesis reaction between fluoroarenes and carbonyl derivatives is reported. The reaction exchanges fluoride (F–) and alternate nucleophiles (OAc–, CO2R–, SR–, Cl–, CN–, NCS–). The approach provides a conceptually novel route to manipulate the fluorine content of organic molecules. By combining fluorination and defluorination steps into a single catalytic cycle, a byproduct free and 100% atom-efficient reaction can be achieved.

In this article, we report on the synthesis and characterization of the tetracarboxylatodirhodium(II) complexes [Rh2(&mu, &ndash, O2CCH2OMe)4(THF)2] (1) and [Rh2(&mu, O2CC6H4&ndash, p&ndash, CMe3)4(OH2)2] (2) by metathesis reaction of [Rh2(&mu, O2CMe)4] with the corresponding ligand acting also as the reaction solvent. The reaction of the corresponding tetracarboxylato precursor, [Rh2(&mu, O2CR)4], with PPh4[Au(CN)2] at room temperature, yielded the one-dimensional polymers (PPh4)n[Rh2(&mu, O2CR)4Au(CN)2]n (R = Me (3), CH2OMe (4), CH2OEt (5)) and the non-polymeric compounds (PPh4)2{Rh2(&mu, O2CR)4[Au(CN)2]2} (R = CMe3 (6), C6H4&ndash, CMe3 (7)). The structural characterization of 1, 3&middot, 2CH2Cl2, 4&middot, 3CH2Cl2, 5, 6, and 7&middot, 2OCMe2 is also provided with a detailed description of their crystal structures and intermolecular interactions. The polymeric compounds 3&middot, 3CH2Cl2, and 5 show wavy chains with Rh&ndash, Au&ndash, Rh and Rh&ndash, N&ndash, C angles in the ranges 177.18&deg, 178.69&deg, and 163.0&deg, 170.4&deg, respectively. A comparative study with related rhodium-silver complexes previously reported indicates no significant influence of the gold or silver atoms in the solid-state arrangement of these kinds of complexes.

The first stable base‐free terminal uranium phosphinidene metallocene is presented; and its structure and reactivity have been studied in detail and compared to that of the corresponding thorium derivative. Salt metathesis reaction of the methyl iodide uranium metallocene Cp’’’2U(I)Me (2, Cp’’’=η 5‐1,2,4‐(Me3C)3C5H2) with Mes*PHK (Mes*=2,4,6‐(Me3C)3C6H2) in THF yields the base‐free terminal uranium phosphinidene metallocene, Cp’’’2U=PMes* (3). In addition, density functional theory (DFT) studies suggest substantial 5f orbital contributions to the bonding within the uranium phosphinidene [U]=PAr moiety, which results in a more covalent bonding between the [Cp’’’2U]2+ and [Mes*P]2− fragments than that for the related thorium derivative. This difference in bonding besides steric reasons causes different reactivity patterns for both molecules. Therefore, the uranium derivative 3 may act as a Cp’’’2U(II) synthon releasing the phosphinidene moiety (Mes*P:) when treated with alkynes or a variety of hetero‐unsaturated molecules such as imines, thiazoles, ketazines, bipy, organic azides, diazene derivatives, ketones, and carbodiimides., The first base‐free terminal uranium phosphinidene metallocene was prepared and it showed a distinctively different reactivity compared to the related thorium phosphinidenes.

The interaction between menin and mixed lineage leukemia (MLL) was identified as an interesting target for treating some cancers including acute leukemia. On the basis of the known crystal structure of the MBM1-menin complex (MBM - menin binding motif), several cyclic peptides were designed. Elaboration of the effective cyclization strategy using a metathesis reaction allowed for a successfully large number of derivatives to be obtained. Subsequent optimization of the loop size, as well as N-terminal, central and C-terminal parts of the studied peptides resulted in structures exhibiting low nanomolar activities. A crystal structure of an inhibitor-menin complex revealed a compact conformation of the ligand molecule, which is stabilized not only by the introduction of a covalent linker but also three intramolecular hydrogen bonds. The inhibitor adopts a figure eight-like conformation, which perfectly fits the cleft of menin. We demonstrated that the development of compact, miniprotein-like structures is a highly effective approach for inhibition of protein-protein interactions.

The ability of locally laboratory-synthesized polyaluminium chloride (PAC) with high Al13 content (PAC-Al13) to remove organic, inorganic matter and colour from potable water, agricultural and electroplating wastewaters was evaluated relative to commercial PAC (PACI). PAC-Al13 used in this study was prepared using batch titration of NaOH into AlCl3·6H2O solution under vigorous stirring as opposed to the conventional slow-base titration method. The highly pure PAC-Al13 (containing 79% polymeric Al13 species) with high basicity (87%) was isolated and extracted using the sulphate displacement method and metathesis reaction. PAC-Al13 showed higher COD (85–96%), metals (95–100%), TDS (86–90%) and colour (90–95%) removal compared with PACI, i.e. COD (57–74%), metals (71–99%), TDS (58–80%) and colour (85–92%). The dominance of polymeric Al13 species in PAC-Al13 was supported from the scanning electron microscopy images (presence of Keggin structure of Al13) and the 27Al nuclear magnetic resonance analysis that showed the appearance of a single peak at 62.1 ppm. This study demonstrated the potential of using a new type of PAC, produced using simple preparation technique and contain high polymeric Al13 species, that has the ability to remove contaminants from water and wastewater systems more efficiently.

Combination of high-throughput experimentation, surface organometallic chemistry and data analysis helps to extract key structural parameters that facilitate olefin metathesis., A combination of high-throughput experimentation (HTE), surface organometallic chemistry (SOMC) and statistical data analysis provided the platform to analyze in situ silica-grafted Mo imido alkylidene catalysts based on a library of 35 phenols. Overall, these tools allowed for the identification of σ-donor electronic effects and dispersive interactions and as key drivers in a prototypical metathesis reaction, homodimerization of 1-nonene. Univariate and multivariate correlation analysis confirmed the categorization of the catalytic data into two groups, depending on the presence of aryl groups in ortho position of the phenol ligand. The initial activity (TOFin) was predominantly correlated to the σ-donor ability of the aryloxy ligands, while the overall catalytic performance (TON1 h) was mainly dependent on attractive dispersive interactions with the used phenol ligands featuring aryl ortho substituents and, in sharp contrast, repulsive dispersive interactions with phenol free of aryl ortho substituents. This work outlines a fast and efficient workflow of gaining molecular-level insight into supported metathesis catalysts and highlights σ-donor ability and noncovalent interactions as crucial properties for designing active d0 supported metathesis catalysts.

While the metathesis reaction between alkynes and carbonyl compounds is an important tool in organic synthesis, the reactivity of alkynes with isoelectronic main-group R2E═O compounds is unexplored. Herein, we show that oxophosphonium ions, which are the isoelectronic phosphorus congeners to carbonyl compounds, undergo [2 + 2] cycloaddition reactions with different alkynes to generate 1,2-oxaphosphete ions, which were isolated and structurally characterized. The strained phosphorus-oxygen heterocycles open to the corresponding heterodiene structure at elevated temperature, which was used to generate six-membered phosphorus heterocycles via hetero Diels-Alder reactions. Insights into the influence of the substituents at the phosphorus center on the energy profile of the oxygen atom transfer reaction were obtained by quantum-chemical calculations.

A set of nitro-activated ruthenium-based Hoveyda-Grubbs type olefin metathesis catalysts bearing sterically modified N-hetero-cyclic carbene (NHC) ligands have been obtained, characterised and studied in a set of model metathesis reactions. It was found that catalysts bearing standard SIMes and SIPr ligands (4a and 4b) gave the best results in metathesis of substrates with more accessible C&ndash, C double bonds. At the same time, catalysts bearing engineered naphthyl-substituted NHC ligands (4d&ndash, e) exhibited high activity towards formation of tetrasubstituted C&ndash, C double bonds, the reaction which was traditionally Achilles&rsquo, heel of the nitro-activated Hoveyda&ndash, Grubbs catalyst.

Carbonyl-ene, Prins and carbonyl-olefin metathesis reactions represent powerful strategies for carbon-carbon bond formation relying on Lewis acid catalysts. Although common Lewis acids are able to provide efficient activation, the reactions often proceed with low regio-, or chemoselectivity while high selectivity frequently requires the use of well-designed metal-ligand complexes. Here we demonstrate that simple Lewis acids including Me2AlCl, FeCl3, and SnCl4 can show remarkable selectivity in dif-ferentiating between distinct transformations of carbonyl and olefin functional groups resulting in either carbonyl-ene or carbonyl-olefin metathesis products. Specifically, we report the development of predictive multivariate linear regression models that rely on kinetic and thermodynamic information obtained in DFT calculations to gain important insights into the complex potential energy surfaces (PES) of these competing reaction paths. The presented results further our understanding of Lewis acid reactivity and suggest that even simple Lewis acids have the potential to function as highly selective catalysts.

Acetylide-protected gold nanoclusters represent a recently described class of nanocluster compounds that are computationally predicted to be more stable than well-studied thiolate-protected clusters. Ligand exchange of thiolates-for-acetylides on these clusters as well as the reverse reaction are so-far unknown. Such reactions can inform a practical understanding of stability and other differences between thiolate- and acetylide-protected gold clusters. Here it is shown that acetylide-for-thiolate ligand exchange is facile when using either a lithium phenylacetylide or a gold(i)-phenylacetylide complex as incoming ligand to thiolate-protected gold clusters, whereas the reaction fails when using phenylacetylene. Both partial and full exchange are possible, as is the reverse reaction. While the overall reaction resembles ligand exchange, it may be better described as a metathesis reaction. Notably, while the simple thiolate-for-acetylide exchange reaction is enthalpically unfavorable, metathesis reactions between these ligands are enthalpically favorable. Intercluster exchange is also observed between thiolate-protected and acetylide-protected clusters.

Olefin cross metathesis has been employed for the first time for the post-polymerization chemical modification of porous polymers. High quality microspheres of poly(divinylbenzene) were synthesized by the precipitation polymerization of divi-nylbenzene-55 in porogenic solvents, and the olefin cross metathesis reactions of the pendent (polymer-bound) vinyl groups not consumed by polymerization were performed with diverse coupling partners in dichloromethane using the Grubbs 2 catalyst, leading to microspheres decorated with a wide range of functional groups.

The development of innovative bio-based skin care products has received an increased attention in the latter years. In the present work, the synthesis of original active principle ingredients based on ionic liquids (ILs) with cholinium cation and vitamins B anions, followed by their incorporation in bacterial nanocellulose (BC) membranes for topical applications, is reported. Three ILs, namely cholinium nicotinate [Ch][B3], cholinium pantothenate [Ch][B5] and cholinium pyridoxylate [Ch][B6], were synthesized through a metathesis reaction and their structure characterized in detail. Thermal analysis confirmed their denomination as ILs and their high thermal resistance. The solubility of these ILs was higher than their vitamin precursors, especially in the case of [Ch][B3] whose solubility increased 30.6-fold enhancing the bioavailability of this vitamin. The incorporation of ILs in BC led to translucent and homogeneous membranes stable up to 190 °C. ILs acted as plasticizers reducing BC brittleness that facilitated their application on irregular skin regions. Moreover, the re-hydration ability of BC-ILs membranes was improved 2.9 to 4.8-fold in comparison to BC, ensuring adequate hydration for ILs release, while the release of ILs in buffer solutions was more complete and faster than the release of vitamins. Finally, BC-ILs were proven not cytotoxic to skin epithelial cells and thus are suitable materials for skin care applications.

A facile method for post-synthetic exchange of anions in an iron(II) spin crossover material using mechanochemistry is described. Dry grinding of the [Fe(atrz)\(_3\)]Cl\(_2\) complex (atrz = 4-amino-1,2,4-triazole) in the presence of an excess of sodium halide salt results in the complete exchange of anions and formation of [Fe(atrz)\(_3\)]Br\(_2\) and [Fe(atrz)\(_3\)]I\(_2\) in a solid-state metathesis reaction. The method represents a new strategy for tuning active switching properties such as the transition temperature in spin crossover systems. Formation of stable by-products was identified as a major driving force for exchange and a straightforward method to predict the likely outcome of such reactions using simple thermodynamic considerations is presented.

The reaction between trans-[AuF2(pyridine)2]+ and [PhI(pyridine)2]2+ results in the formation of PhIF2 and [Au(pyridine)4]3+. Investigation of the reaction pathway using model Pd and Pt analogues of the gold complex indicate that the most likely mechanism is attack by the Au–F onto the I(III), rather than a redox process. This demonstrates that the Au(III)–F fragment can behave in a nucleophilic manner even in a relatively electron-poor cationic complex.

This manuscript includes a comprehensive study of the synthesis and spectroscopic features of 2,5-disilyl boroles. Reacting boron trichloride BCl3 with 2,3-Ph*2-1,4-(SiMe3)2-1,4-dilithiobuta-1,3-diene (Ph* = 3,5-t-Bu2(C6H3)) allowed reliable access to 1-Chloro-2,5-(SiMe3)2-3,4-(Ph*)2-borole in good yields (60%). Unlike 2,3,4,5-tetraphenyl haloboroles, this 2,5-bis-trimethylsilyl substituted chloroborole is thermally stable in solution to up to 130 °C. Metathesis reactions of the chloroborole with metal aryls or of the dilithiobutadiene with arylboron dihalides grant access to 1-Ar-2,5-(SiMe3)2-3,4-(Ph*)2 boroles (Ar = Ph, Mes, Ph*, C6F5). Unlike the generally intensely blue-green 2,3,4,5-tetraaryl boroles, brightly orange/red 2,5-bis-trimethylsilyl substituted boroles reveal blue-shifted π/π*-transitions due to a lack of π-system interaction between borole and 2,5-bound aryls. Light is shed on the synthetic peculiarities for the synthesis of 2,5-disilyl-boroles. While direct treatment of the respective 1,1-dimethyl-stannole with ArBCl2via otherwise well-established B/Sn exchange reactions fails, the selectivity of reactions of 2,3-Ph*2-1,4-(SiMe3)2-1,4-dilithiobuta-1,3-diene with ArBCl2 is solvent dependent and leads to rearranged 3-borolenes in hydrocarbons. Gutmann–Beckett analysis reveal reduced Lewis-acidity of disilylboroles compared to pentaphenyl borole.

The first synthesis of the marine benzoxepane hydroquinone cyclosiphonodictyol A and its bis(sulfato) from commercial (+)-sclareolide is reported. The key steps of the synthetic sequence (11 steps, 46% global) are the nucleophilic attack of a hindered tertiary alkoxide, a ring-closing metathesis reaction, and the Diels-Alder cycloaddition of a dienol acetate.