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An improved synthesis of the simplest nitric acid ester, methyl nitrate, and a new synthesis of fluoromethyl nitrate use the metathesis of the corresponding iodomethanes with silver nitrate. Both compounds were identified by spectroscopy and the structures determined for in situ grown crystals by X-ray diffraction as well as in the gas phase by electron diffraction. Fluorination leads to structures with shorter C-O and N-O bonds, has an energetically destabilizing effect and increases friction sensitivity, but decreases detonation performance., (© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

Colorless crystalline 2,6-dibromo-4,8-dimethyl-1,3,5,7-tetraphenylbenzobis(diazaborole) 4 resulted from the cyclocondensation of 3,6-dimethyl-1,2,4,5-tetraphenylaminobenzene 3d with two equivalents of boron tribromide in the presence of calcium hydride. Synthesis of the dark-red crystalline 2-bromo-N,N'-bis(diisopropylphenyl)acenaphtho-1,3,2-diazaborole 7 was effected by the cyclocondensation of 1,2-bis(N-2',6'-diisopropylphenylimino)acenaphthene (5) and boron tribromide with subsequent sodium amalgam reduction of the initially formed burgundy red diazaborolium salt 6. Compounds 4, 6 and 7 are characterised by elemental analyses, 1 H, 11 B and 13 C NMR spectroscopy, as well as by single X-ray diffraction studies. The electronic structures of 4, 6 and 7 are subject to DFT calculations.

The first terminal arsinidene complexes [{(NHC)C(Ph)}As]Fe(CO)4 (NHC = IPr = C{(NDipp)CH}25, Me-IPr = C{(NDipp)CMe}26; Dipp = 2,6-iPr2C6H3) with a two-coordinated arsenic atom have been reported as crystalline solids. Calculations suggest that 5 and 6 are electrophilic, which has been demonstrated by the reaction of 5 with an NHC nucleophile (IMe4), affording the Lewis adduct [{(IPr)C(Ph)}As(IMe4)]Fe(CO)4 (7) (IMe4 = C(NMeCMe)2).

The divinyldiarsene radical cations [{(NHC)C(Ph)}As] 2 (GaCl 4 ) (NHC=IPr: C{(NDipp)CH} 2 3; SIPr: C{(NDipp)CH 2 } 2 4; Dipp=2,6-iPr 2 C 6 H 3 ) and dications [{(NHC)C(Ph)}As] 2 (GaCl 4 ) 2 (NHC=IPr 5; SIPr 6) are readily accessible as crystalline solids on sequential one-electron oxidation of the corresponding divinyldiarsenes [{(NHC)C(Ph)}As] 2 (NHC=IPr 1; SIPr 2) with GaCl 3 . Compounds 3-6 have been characterized by X-ray diffraction, cyclic voltammetry, EPR/NMR spectroscopy, and UV/vis absorption spectroscopy as well as DFT calculations. The sequential removal of one electron from the HOMO, that is mainly the As-As π-bond, of 1 and 2 leads to successive elongation of the As=As bond and contraction of the C-As bonds from 1/2→3/4→5/6. The UV/vis spectrum of 3 and 4 each exhibits a strong absorption in the visible region associated with SOMO-related transitions. The EPR spectrum of 3 and 4 each shows a broadened septet owing to coupling of the unpaired electron with two 75 As (I=3/2) nuclei., (© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

A series of unique C 2 P 3 -ring compounds [(ADC Ar )P 3 ] (ADC Ar = ArC{(DippN)C} 2 ; Dipp = 2,6-iPr 2 C 6 H 3 ; Ar = Ph 4a , 3-MeC 6 H 4 4b , 4-MeC 6 H 4 4c , and 4-Me 2 NC 6 H 4 4d ) are readily accessible in an almost quantitative yield by the direct functionalization of white phosphorus (P 4 ) with appropriate anionic dicarbenes [Li(ADC Ar )]. The formation of 1,2,3-triphosphol-2-ides ( 4a-4d ) suggests unprecedented [3 + 1] fragmentation of P 4 into P 3 + and P - . The P 3 + cation is trapped by the (ADC Ar ) - to give 4 , while the putative P - anion reacts with additional P 4 to yield the Li 3 P 7 species, a useful reagent in the synthesis of organophosphorus compounds. Remarkably, the P 4 fragmentation is also viable with the related mesoionic carbenes (iMICs Ar ) (iMIC Ar = ArC{(DippN) 2 CCH}, i stands for imidazole-based) giving rise to 4 . DFT calculations reveal that both the C 3 N 2 and C 2 P 3 -rings of 4 are 6π-electron aromatic systems. The natural bonding orbital (NBO) analyses indicate that compounds 4 are mesoionic species featuring a negatively polarized C 2 P 3 -ring. The HOMO-3 of 4 is mainly the lone-pair at the central phosphorus atom that undergoes σ-bond formation with a variety of metal-electrophiles to yield complexes [{(ADC Ar )P 3 }M(CO) n ] (M = Fe, n = 4, Ar = Ph 5a or 4-Me-C 6 H 4 5b ; M = Mo, n = 5, Ar = Ph 6 ; M = W, n = 5, Ar = 4-Me 2 NC 6 H 4 7 )., (This journal is © The Royal Society of Chemistry 2019.)

The reaction of a strongly basic phosphazene (Schwesinger base) with water afforded the corresponding metastable hydroxide trihydrate [OH(OH 2 ) 3 ] - salt. This is the first hydroxide solvate that is not in contact with a cation and furthermore one of rare known water-stabilized hydroxide anions. Thermolysis in vacuum results in the decomposition of the hydroxide salt and quantitative liberation of the free phosphazene base. This approach was used to synthesize the Schwesinger base from its hydrochloride salt after anion exchange in excellent yields of over 97 %. This deprotonation method can also be used for the phosphazene-base-catalyzed preparation of the Ruppert-Prakash reagent Me 3 SiCF 3 using fluoroform (HCF 3 ) as the trifluoromethyl building block and sodium hydroxide as the formal deprotonation agent., (© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

A comprehensive study was performed for the first time to compare two structurally related substance classes, namely indazole-5-carboxamides (11-16) and (indazole-5-yl)methanimines (17-22). Both chemical entities are potent, selective and reversible MAO-B inhibitors and, therefore, may serve as promising lead structures for the development of drug candidates against Parkinson's disease (PD) and other neurological disorders. Compounds 15 (K i  = 170 pM, SI = 25907) and 17 (K i  = 270 pM, SI = 16340) were the most potent and selective MAO-B inhibitors in both series. To investigate the multi-target inhibitory activity, all compounds were further screened for their potency against human AChE and BuChE enzymes. Compound 15 was found to be the most potent and selective AChE inhibitor in all series (hAChE IC 50  = 78.3 ± 1.7 μM). Moreover, compounds 11 and 17 showed no risk of drug-induced hepatotoxicity and a wider safety window, as determined in preliminary cytotoxicity screening. Molecular modeling studies into the human MAO-B enzyme-binding site supported by a HYDE analysis suggested that the imine linker similarly contributes to the total binding energy in methanimines 17-22 as the amide spacer in their carboxamide analogs 11-16. Amplified photophysical evaluation of compounds 17 and 20, including single X-ray analysis, photochemical experiments, and quantum-chemical calculations, provided insights into their more favourable isomeric forms and structural features, which contribute to their biologically active form and promising drug-like properties., (Copyright © 2019 Elsevier Masson SAS. All rights reserved.)

The first calcium complex from nature, Coumamarin (1), 7-hydroxy-3-methoxy-2-oxo-2H-chromene-6-carboxylate Ca(II) complex, was isolated from Aspergillus sydowii ASTI, together with diorcinol (2), violaceol I (3), hydroxysydonic acid (4), cyclo (Trp-Phe), kojic acid, ergosterol, and uracil. The producing strain was isolated from marine water sample collected from Tiran Island, Red Sea, Egypt. Structure 1 was assigned by intensive 1D, 2D NMR, HR-ESIMS, and X-ray crystallography as well. Coumamarin is potentially active against certain tested bacteria and yeasts, while showing no cytotoxic activity against human cervix carcinoma cell line (KB-3-1). Taxonomically, the fungus was identified by phylogenetic analysis of its 18S rRNA gene sequence.

Herein, we report the isolation and stereo-structure of rare pyrane-based cembranoid diterpenes, 9-hydroxy-7,8-dehydro-sarcotrocheliol ( 1 ) and sarcotrocheliol ( 2 ), from Sarcophyton trocheliophorum collected from Red Sea. Absolute configurations of both compounds were revised based on single crystal X-ray analyses.

The synthesis and characterization of the crystalline diphosphene radical cations [{(NHC)C(Ph)}P]2(GaCl4) (NHC = IPr = C{(NDipp)CH}23, SIPr = C{(NDipp)CH2}24; Dipp = 2,6-iPr2C6H3) and dications [{(NHC)C(Ph)}P]2(GaCl4)2 (NHC = IPr 5, SIPr 6) featuring a π-conjugated C2P2C2-framework has been reported.

Weakly coordinating anions (WCAs) are important for academic reasons as well as for technical applications. Tetrakis(pentafluoroethyl)gallate, [Ga(C 2 F 5 ) 4 ] - , a new WCA, is accessible by treatment of [GaCl 3 (dmap)] (dmap=4-dimethylaminopyridine) with LiC 2 F 5 . The anion [Ga(C 2 F 5 ) 4 ] - proved to be reluctant towards deterioration by aqueous hydrochloric acid or lithium hydroxide. Various salts of [Ga(C 2 F 5 ) 4 ] - were synthesized with cations such as [PPh 4 ] + , [CPh 3 ] + , [(O 2 H 5 ) 2 (OH 2 ) 2 ] 2+ , and [Li(dec) 2 ] + (dec=diethyl carbonate). Thermolysis of [(O 2 H 5 ) 2 (OH 2 ) 2 ][Ga(C 2 F 5 ) 4 ] 2 gives rise to a dihydrate of tris(pentafluoroethyl)gallane, [Ga(C 2 F 5 ) 3 (OH 2 ) 2 ]. All products were characterized by NMR and IR spectroscopy, mass spectrometry, X-ray diffraction, and elemental analysis. Furthermore, an outlook for the application of [Li(dec) 2 ][Ga(C 2 F 5 ) 4 ] as a conducting salt in lithium-ion batteries is presented., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The first divinyldiarsenes [{(NHC)C(Ph)}As] 2 (NHC=IPr 3 a, SIPr 3 b; IPr=C{(NAr)CH} 2 ; SIPr=C{(NAr)CH 2 } 2 ; Ar=2,6-iPr 2 C 6 H 3 ) are reported. Compounds 3 a and 3 b were prepared by the reduction of corresponding chlorides {(NHC)C(Ph)}AsCl 2 (NHC=IPr 2 a, SIPr 2 b) with Mg. Calculations revealed a small HOMO-LUMO energy gap of 3.86 (3 a) and 4.24 eV (3 b). Treatment of 3 a with (Me 2 S)AuCl led to the cleavage of the As=As bond to restore 2 a, which is expected to proceed via the diarsane [{(IPr)C(Ph)}AsCl] 2 (4). Remarkably, 4 as well as 2 a can be selectively accessed on treatment of 3 a with an appropriate amount of C 2 Cl 6 . Moreover, 3 a readily reacts with PhEEPh (E=Se or Te) at room temperature to give {(IPr)C(Ph)}As(EPh) 2 (E=Se 5 a; Te 5 b), revealing the cleavage of As=As and E-E bonds and the formation of As-E bonds. Such highly selective stepwise oxidation (3 a→4→2 a) and bond metathesis (3 a→5 a,b) reactions are unprecedented in main-group chemistry., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The olefinic C-H bond functionalization of (NHC)CHPh (NHC=IPr=C{(NAr)CH} 2 1; SIPr=C{(NAr)CH 2 } 2 2; Ar=2,6-iPr 2 C 6 H 3 ), derived from classical N-heterocyclic carbenes (NHCs), with PCl 3 affords the dichlorovinylphosphanes {(NHC)C(Ph)}PCl 2 (NHC=IPr 3, SIPr 4). Two-electron reduction of 3 and 4 with magnesium leads to the formation of the divinyldiphosphenes [{(NHC)C(Ph)}P] 2 (NHC=IPr 5, SIPr 6) as crystalline solids. Unlike literature-known diphosphenes, which are mostly yellow or orange, 5 is a green whereas 6 is a purple solid. Although the P=P bond lengths of 5 (2.062(1)) and 6 (2.055(1) Å) are comparable to those of the known diphosphenes (2.02-2.08 Å), the C-P bond lengths of 5 (1.785(1)) and 6 (1.797(1) Å) are, however, considerably shorter than a C sp 2 -P single bond length (1.85 Å), indicating a considerable π-conjugation between C=C and P=P moieties. The HOMO-LUMO energy gap for 5 (4.15) and 6 (4.52 eV) is strikingly small and thus the narrowest among the diphosphenes (>4.93 eV) reported as yet. Consequently, 5 readily undergoes P=P bond cleavage at room temperature on treatment with sulfur to form the unique dithiophosphorane {(IPr)C(Ph)}P(S) 2 7. Interestingly, reaction of 5 with selenium gives the selenadiphosphirane [{(IPr)C(Ph)}P] 2 Se 8 with an intact P-P bond., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A rotameric tryptamide alkaloid (1a-1b) was isolated from the methanolic extract of the roots of Vepris lecomteana together with the known compounds anhydroevoxine (2), lecomtequinoline C (3), evoxine (4), N-methylflindersine (5), evoxanthine (6), hesperidin, lupeol, β-sitosterol and stigmasterol. The previously not reported 7-(3-anilino-2-hydroxyprenyloxy)-8-methoxydictamine (2a) was obtained by opening the epoxide of anhydroevoxine (2). The structures of above compounds were determined by comprehensive spectroscopic analyses of 1D and 2D NMR, EI-/ESI-MS, X-ray crystallography and comparison with the reported data. At room temperature, 1 H and 13 C NMR spectra show two rotamers (1a and 1b) with integrated intensities of 2/3, whereas at around 60 °C, only the 1b conformer was observed. Furthermore, the crystal structure of 1 was determined by the direct method of single crystal X-ray diffraction. The suggested biosynthesis for the formation of the new rotameric tryptamide alkaloid 1 is presented. Some of the isolated compounds (1, 2 and 2a) were tested in vitro against bacteria, resulting in weak for (1 and 2) to moderate activity for (2a) against Micrococcus luteus and Escherichia coli with MIC values of 15.3 and 15.3 μg/mL, respectively., (Copyright © 2019. Published by Elsevier B.V.)

The structures of the three para-substituted halotetrafluoropyridines with chlorine, bromine, and iodine have been determined in the solid state (X-ray diffraction). The structures of these compounds and that of pentafluoropyridine were also determined in the gas phase (electron diffraction). Structures in the solid state of the bromine and iodine derivatives exhibit halogen bonding as a structure-determining motif. On the way to an investigation of halogen bond formation of halotetrafluoropyridines in the solid state with the stronger Lewis base pyridine, co-crystals of benzene adducts were investigated to gain an understanding of the influence of aryl-aryl interactions. These co-crystals showed halogen bonding only for the two heavier halotetrafluoropyridines. In the pyridine co-crystals halogen bonding was observed for all three para-halotetrafluoropyridines. The formation of homodimers and heterodimers with pyridine is also supported by quantum-chemical calculations of electron density topologies and natural bond orbitals., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

All-cis-1,3,5-triethynyl-1,3,5-triorganyl-1,3,5-trisilacyclohexanes (organyl R = Me, Ph) offer flexible scaffolds with three concordantly oriented ethynyl groups. Lithiation with n-BuLi affords the dimeric {[CH2Si(R)(C2Li)]3(THF)3}2 with a drum-like structure in high yields. They can be transformed into other trinuclear organometallic derivatives like the trimercury cage species [CH2Si(R)C2HgC2(R)SiCH2]3.

Chlorogermane (C 2 F 5 ) 3 GeCl with very electronegative pentafluoroethyl groups was converted with LiCH 2 P(tBu) 2 to obtain the intramolecular frustrated Lewis pair (FLP) (C 2 F 5 ) 3 GeCH 2 P(tBu) 2 , a neutral, germanium-based FLP. Its reactivity was compared to its silicon homologue (C 2 F 5 ) 3 SiCH 2 P(tBu) 2 . Both FLPs cleave NO but give cyclic (Si) and open-chain oxides (Ge). In reactions with HCl both FLPs gave the same adduct type in the solid state, while the proton seems more mobile in solution in the germanium case. Reactions with PhCNO and Me 3 SiCHN 2 result in ring-type adducts. The structures of (C 2 F 5 ) 3 GeCH 2 P(tBu) 2 and of five adducts with substrates were elucidated by X-ray diffraction. The study clearly showed the germanium compound to have a more moderate Lewis acidity compared to the silicon analogue., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The geminal frustrated Lewis pair (FLP) (F 5 C 2 ) 3 SnCH 2 P(tBu) 2 (2) was prepared by reacting (F 5 C 2 ) 3 SnCl with LiCH 2 P(tBu) 2 . It is neutral and contains an extremely electronegatively substituted, but relatively soft (hard-soft acid-base, HSAB) acidic tin function. Its FLP-type reactivity was proven by reaction with a variety of small molecules (CO 2 , SO 2 , CS 2 , PhNCO, HCl, (Ph 3 P)AuCl). However, it shows no reaction in H/D scrambling experiments with H 2 /D 2 mixtures and binds CO 2 reversibly, as was observed by VT-NMR spectroscopy. Compound 2 and all its adducts were completely characterized by means of multinuclear NMR spectroscopy, elemental analysis, and X-ray diffraction experiments., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Two phosphane-gold(i) functions (with tri(para-tolyl)- or tri-n-butylphosphane) were attached to a 1,8-diethynylanthracene backbone. The ligand size prevents direct interaction between the gold atoms, but the initial products rearrange to form macrocyclic anions comprising two 1,8-diethynylanthracene and two gold units, linked to cationic gold(i) fragments by maximising aurophilic interactions.

α,ω-Bis(1,8-dichloroanthracen-10-yl)alkanes with (CH 2 ) n -linker units ( n =1-4) were synthesized starting from 1,8-dichloroanthracen-10(9 H )-one. This was transformed into anthracenes with allyl, bromomethyl and propargyl substituents in position 10; these were converted in various C-C-bond formation reactions (plus hydrogenation), leading to two anthracene units flexibly linked by α,ω-alkandiyl groups. 1,2-Ethandiyl- and 1,3-propandiyl-linked derivatives were functionalized with ethynyl groups in positions 1, 8, 1' and 8', and these terminally functionalized by Me 3 Sn groups using Me 2 NSnMe 3 . All linked bisanthracenes were subjected to UV light induced cyclomerization and a series of 9,10 : 9',10'-photo-cyclomers were obtained. Their thermal cycloreversion and (repeated) switchability was demonstrated. 1,3-Bis{1,8-bis[(trimethylstannyl)ethynyl]anthracen-10-yl}propane served as model compound for photo-switchable acceptor molecules and its open and closed forms were characterized by NMR and DOSY experiments., Competing Interests: The authors declare no conflict of interest.

Para-quinodimethane (pQDM) is a fundamental structural component in many π-conjugated organic molecules and materials. The incorporation of phosphorus atom into π-conjugated frameworks offers unique opportunities for controlling the properties of derived species. A phosphorus analogue of p-quinodimethane (pQDM), (IPrC) 2 P 4 [5, IPr=C{N(Ar)CH 2 } 2 ; Ar=2,6-iPr 2 C 6 H 3 ] featuring a planar P 4 ring, was readily accessible by KC 8 -reduction of (IPrC)(PCl 2 ) 2 (2). Base-mediated C-H functionalization of IPrCH 2 (1) with PCl 3 afforded 2. The formation of 5 was expected to occur through a dimerization of the transient 3H-diphosphirene (IPrC)P 2 (4), which was theoretically suggested to have an intermediate diradical character. Compound 5 underwent photo-induced ring-contraction reaction to form the singlet diradicaloid (IPrCP) 2 VI and white phosphorus (P 4 ). The formation of and VI and P 4 suggested the formal diphosphorus (P 2 ) elimination from 5. Indeed, photolysis of a mixture of 1,3-cyclohexadiene (CHD) and 5 led to the formation of P 2 -entrapped product (CHD) 2 P 2 (6). The compound 5 represents the first organophosphorus species that functions as a P 2 source., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Bidentate boron Lewis acids based on 1,8-diethynylanthracene were synthesised in two steps by initial stannylation of the terminal alkynes and subsequent tin-boron exchange with different chloroboranes. The reactions were very selective, and the target compounds were obtained in high purity and good to excellent yields. Complexation experiments of 1,8-bis[(diphenylboranyl)ethynyl]anthracene with nitrogen bases (pyridine, pyrimidine, TMEDA) afforded three stable adducts, which were structurally characterised by X-ray diffraction. Competition experiments demonstrated the selective exchange of guests, and quantum-chemical calculations provided information on their energetics. NMR experiments at low temperature gave insight into the dynamic behaviour of the TMEDA adduct., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

An extensive study was performed to develop a series of (pyrrolo-pyridin-5-yl)benzamides as reversible MAO-B inhibitors. Compounds 14 (NTZ-2020, hMAO-B IC 50  = 1.11 nM, K i  = 0.56 nM, >9000-fold selective versus MAO-A) and 15 (NTZ-2027, hMAO-B IC 50  = 3.27 nM, K i  = 1.45 nM, SI > 3058) are identified as the most promising BBB permeable derivatives within the series of (1H-pyrrolo[3,2-b]pyridine-5-yl)benzamides, combining both high potency and selectivity with optimal physicochemical and drug-like properties required for CNS active drugs. Extended photophysical analysis, including single X-ray analysis, quantum-chemical calculations and spectroscopic experiments provided insights into their tautomerism and structural behavioral, which relates to their biologically active form. The reversible MAO-B inhibitor 14 (NTZ-2020) exhibits a neuroprotective effect on cortical neuron survival and induces neurite network outgrowth. These effects are associated with a good BBB penetration of 14 that was confirmed in a triple cell neurovascular unit (NVU) model., (Copyright © 2018 Elsevier Masson SAS. All rights reserved.)

A re-cultivation of the thermophilic fungus Aspergillus terreus TM8, and working up of its extract afforded the dichloro-benzophenone derivative, dihydrogeodin (1) in addition to the butyrolactones I (2), V (3) and VI (4). A literature surveying revealed one recent structural assignment trial for dihydrogeodin (1), however, with some inaccuracies. We report herein a full assignment of dihydrogeodin (1) using extensive study of 1D, 2D NMR and ESI HR mass data. For the first time as well, we report the planar structure of 1 using X-ray crystallography. Docking and molecular dynamic simulation of dihydrogeodin (1) on the isomerase cyclophilin A has revealed its significant potential activity as an antiviral and immunosuppressive agent.

In situ grown crystals of CF3I and CF3CH2I are dominated by II and FF interactions. Their co-crystals with benzene, (CF3I)2·C6H6 and CF3CH2I·C6H6, contain two completely different sets of intermolecular interactions. (CF3I)2·C6H6 shows a unique halogen-bond type: above-the-bond C-IπC6H6 interactions. CF3CH2I·C6H6 shows above-the-centre C-HπC6H6 interactions. These interactions are electrostatically dominated type II halogen bonds between single halogenoalkane molecules and weaker dispersion dominated interactions between the co-crystal components. The observed preferences for benzene for the two binding partners match with calculated molecular electrostatic potentials.

Two-fold C-C cross-coupling of N-heterocyclic carbenes [NHCs; SIPr=C(NArCH 2 ) 2 , 1; IPr=C(NArCH) 2 , 2; Me-IPr=C(NArCMe) 2 , 3; Ar=2,6-iPr 2 C 6 H 3 ] with 4,4''-diiodo-p-terphenyl under Ni catalysis furnished [(SIPr)(C 6 H 4 ) 3 (SIPr)](I) 2 (4), [(IPr)(C 6 H 4 ) 3 (IPr)](I) 2 (5), and [(Me-IPr)(C 6 H 4 ) 3 (Me-IPr)](I) 2 (6). Two-electron reduction of 4-6 with KC 8 readily afforded NHC analogues of Müller's hydrocarbon (MH), [(SIPr)(C 6 H 4 ) 3 (SIPr)] (7), [(IPr)(C 6 H 4 ) 3 (IPr)] (8), and [(Me-IPr)(C 6 H 4 ) 3 (Me-IPr)] (9), respectively, as highly colored crystalline solids. Quantum chemical calculations suggested that the singlet ground state for 7-9 possesses a vertical singlet-triplet energy gap ΔE S-T of -7.24 to -7.60 kcal mol -1 , which is significantly lower compared to that of the NHC analogues of Thiele's (TH) and Chichibabin's (CH) (18-38 kcal mol -1 ) hydrocarbons. Importantly, the calculated diradical character (y) of 7-9 (y≈0.6) is considerably higher compared to that of the related TH and CH (y=0.1-0.4), suggesting the open-shell singlet character of 7-9., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The thermally unstable α-fluoroalcohol undecafluorocyclohexanol (c-C6F11OH) was prepared by addition of hydrogen fluoride to the corresponding ketone. c-C6F10(CF3)OH was obtained by protonation of its alkoxide [NMe4]+[C7F13O]-. Decafluorocyclohexane-1,1-diol (c-C6F10(OH)2) was prepared by acidic workup of the corresponding alkoxide [NMe4]+[C6F11O]- with sulfuric acid, which yielded (c-C6F10(OH)2) and fluorosulfonic acid. The structures of c-C6F10(CF3)OH·2H2O and of (c-C6F10(OH)2) were elucidated by single-crystal X-ray and gas-phase electron-diffraction studies.

A series of ten heteroleptic and homoleptic mononuclear Zr(iv) and Hf(iv) complexes bearing differently substituted phenoxy-benzoxazole ligands was synthesised. The complexes were characterised by 1H and 13C{1H} NMR spectroscopy as well as by elemental analyses and X-ray diffraction experiments. The molecular structures show octahedral or tetragonal-antiprismatic coordination motifs at the metal atom. The crystal packing patterns depend on the substitution of the ligands. The intermolecular interactions in the solid state are governed by weak π-π interactions, and are also dependent on the ligand structure. Photo-physical investigations reveal that all ten complexes show a ligand-centered fluorescence with emission maxima in the blue region of the electromagnetic spectrum.

Disulfuryl dichloride ClSO 2 OSO 2 Cl was characterized by vibrational spectroscopy in the gaseous and liquid phase as well as in the Ar-matrix. By varying the temperature, certain bands could be assigned to several conformers. Gas-phase electron diffraction revealed a dominance of the anti-conformer at ambient temperature. The same conformation was found in the solid state. Via the in situ technique for crystallization, not less than four different modifications were identified. Among these different modifications, the structural parameters of the molecules remain relatively constant, but the aggregation pattern changes. Although the molecules aggregate by chlorine⋅⋅⋅oxygen contacts in each modification, the geometrical parameters of these interaction show significant differences and were evaluated and are in part inconsistent with the halogen bonding concept., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Centrohexaindane was converted into its T d -symmetrical 2,3,6,7,10,11,14,15,20,21,26,27-dodecabromo and -dodecaiodo derivatives using N-bromo- and N-iodosuccinimide, respectively, in the presence of trifluoromethanesulfonic acid as a catalyst in single, highly efficient steps. Sonication or microwave irradiation was indispensable to enforce exhaustive halogenation of the twelve equivalent peripheral positions of this Cartesian polyaromatic hydrocarbon. Despite their extremely poor solubility in most organic solvents, the new dodecahalo derivatives were fully characterized, including single crystal X-ray structure analysis. Subsequent Pd 0 -catalyzed twelve-fold C-C cross-coupling reactions furnished the corresponding dodecamethyl, dodeca(phenylethynyl) and dodecaphenyl derivatives in good to excellent yields. The latter hydrocarbon was also analyzed by X-ray diffraction., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Stable N-heterocyclic carbene analogues of Thiele and Chichibabin hydrocarbons, [(IPr)(C 6 H 4 )(IPr)] and [(IPr)(C 6 H 4 ) 2 (IPr)] (4 and 5, respectively; IPr=C{N(2,6-iPr 2 C 6 H 3 )} 2 CHCH), are reported. In a nickel-catalyzed double carbenylation of 1,4-Br 2 C 6 H 4 and 4,4'-Br 2 (C 6 H 4 ) 2 with IPr (1), [(IPr)(C 6 H 4 )(IPr)](Br) 2 (2) and [(IPr)(C 6 H 4 ) 2 (IPr)](Br) 2 (3) were generated, which respectively afforded 4 and 5 as crystalline solids upon reduction with KC 8 . Experimental and computational studies support the semiquinoidal nature of 5 with a small singlet-triplet energy gap ΔE S-T of 10.7 kcal mol -1 , whereas 4 features more quinoidal character with a rather large ΔE S-T of 25.6 kcal mol -1 . In view of the low ΔE S-T , 4 and 5 may be described as biradicaloids. Moreover, 5 has considerable (41 %) diradical character., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Acetonitrile is deprotonated by a combination of the strong Lewis acid (C 2 F 5 ) 3 PF 2 and triethylamine. The resulting cyanomethyl function is bound to the phosphorus moiety, affording the highly stable salt [HNEt 3 ][P(C 2 F 5 ) 3 F 2 (CH 2 CN)]. Salt metathesis reactions furnished the corresponding [Cu(MeCN) 2 ] + and [Ag(MeCN)] + derivatives in which the CH 2 CN substituent of the anion [P(C 2 F 5 ) 3 F 2 (CH 2 CN)] - coordinates to the metal. An investigation of the gas separation capability of the silver salt [Ag(MeCN)][P(C 2 F 5 ) 3 F 2 (CH 2 CN)] shows an uptake of 1.7 equivalents of isobutene from a propane/isobutene mixture. The reaction of (C 2 F 5 ) 3 PF 2 with acetonitrile and diethylamine furnishes [P(C 2 F 5 ) 3 F 2 {NHC(CH 3 )NEt 2 }]-a phosphate featuring an amidine ligand which formally results from hydroamination of acetonitrile by HNEt 2 . Exchange of HNEt 2 with the primary amines H 2 NPh and H 2 NBu leads to comparable amidine salts that exhibit a solvent-dependent conformational isomerism., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The neutral silver(i) dithiocarboxylate complexes silver(i) dithioacetate, silver(i) pentafluorodithiobenzoate, silver(i) 2,4,6-trimethyldithiobenzoate, silver(i) 2,4,6-tri-iso-propyldithiobenzoate and silver(i) 2,6-dimesityl-dithiobenzoate were synthesized and characterized by IR spectroscopy, elemental analyses and single crystal X-ray diffraction. All complexes form primarily dinuclear units with eight-membered rings [Ag2S4C2], which in turn aggregate by argentophilic interactions and additional AgS contacts in their crystal structures. The molecular structures and shapes of aggregation in the solid state are presented and discussed. The layer-like and chain-like aggregates as well as the [Ag] clusters formed are compared with the (almost) analogous gold(i) complexes.

The direct double carbenylation of 1,4-diiodobenzene and 4,4'-dibromobiphenyl with a classical N-heterocyclic carbene, SIPr ( 1 ) (SIPr = :C{ N (2,6-iPr 2 C 6 H 3 )} 2 CH 2 CH 2 ), by means of nickel catalysis gives rise to 1,3-imidazolinium salts [(SIPr)(C 6 H 4 )(SIPr)](I) 2 ( 2 ) and [(SIPr)(C 6 H 4 ) 2 (SIPr)](Br) 2 ( 3 ) as off-white solids. Two-electron reduction of 2 and 3 with KC 8 cleanly yields Kekulé diradicaloid compounds [(SIPr)(C 6 H 4 )(SIPr)] ( 4 ) and [(SIPr)(C 6 H 4 ) 2 (SIPr)] ( 5 ), respectively, as crystalline solids. Structural parameters and DFT as well as CASSCF calculations suggest the closed-shell singlet ground state for 4 and 5 . Calculations reveal a very low singlet-triplet energy gap Δ E S-T for 5 (10.7 kcal mol -1 ), while Δ E S-T for 4 (29.1 kcal mol -1 ) is rather large.

One-electron reduction of C2-arylated 1,3-imidazoli(ni)um salts (IPr Ar )Br (Ar=Ph, 3 a; 4-DMP, 3 b; 4-DMP=4-Me 2 NC 6 H 4 ) and (SIPr Ar )I (Ar=Ph, 4 a; 4-Tol, 4 b) derived from classical NHCs (IPr=:C{N(2,6-iPr 2 C 6 H 3 )} 2 CHCH, 1; SIPr=:C{N(2,6-iPr 2 C 6 H 3 )} 2 CH 2 CH 2 , 2) gave radicals [(IPr Ar )] . (Ar=Ph, 5 a; 4-DMP, 5 b) and [(SIPr Ar )] . (Ar=Ph, 6 a; 4-Tol, 6 b). Each of 5 a,b and 6 a,b exhibited a doublet EPR signal, a characteristic of monoradical species. The first solid-state characterization of NHC-derived carbon-centered radicals 6 a,b by single-crystal X-ray diffraction is reported. DFT calculations indicate that the unpaired electron is mainly located at the original carbene carbon atom and stabilized by partial delocalization over the adjacent aryl group., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Neutral, homoleptic gold(i) dithiocarboxylate complexes with different-sized Me, iPr, Mes, Tip, Mes* and Dmp substituents at the dithiocarboxylate unit were synthesized by reacting the corresponding dithiocarboxylic acid with potassium dicyanoaurate(i). They were characterized by IR spectroscopy and elemental analyses and their structures were determined by single crystal X-ray diffraction. The dinuclear complexes with an intramolecular d10-d10 type aurophilic interaction aggregate through additional intermolecular aurophilic interactions in different binding motifs. The molecular structures and the patterns of aggregation in the solid state are presented and discussed with respect to the influence of the substituent size.

The tin-tin bond cleavage of hexaorganodistannanes by nucleophiles is a long-known reaction and widely used for stannate formation or stannyl group transfer. Herein, we detail our experiments to provide analytical evidence for the existence of the reasonably stable anionic complexes [XSn(C 2 F 5 ) 3 {Sn(C 2 F 5 ) 3 }] - (X=Cl, Br, I, Sn(C 2 F 5 ) 3 ) derived from hexakis(pentafluoroethyl)distannane. NMR investigations at low temperature lend further mechanistic insights. Thus, by detection of the imposing ion [Sn(C 2 F 5 ) 3 {Sn(C 2 F 5 ) 3 } 2 ] - , one can surmise that the chemistry of Sn 2 (C 2 F 5 ) 6 has more in common with the isolobal iodine than with classical distannanes., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

In this contribution we report on the synthesis of bis(pentafluoroethyl)stannane, H 2 Sn(C 2 F 5 ) 2 . In the reaction with donor molecules a ready elimination of hydrogen and the formation of the corresponding donor-stabilized monomeric bis(pentafluoroethyl)stannylene, Sn(C 2 F 5 ) 2 , becomes apparent. With dependence on the Lewis basicity and steric demand of the donor, varying coordination numbers are realized. Whereas the reaction with nitrogen bases like 4-(dimethylamino)pyridine (DMAP) leads to the complexation of two donor molecules, [Sn(C 2 F 5 ) 2 (dmap) 2 ], treatment with PMe 3 or [Sn(C 2 F 5 ) 3 ] - furnished the corresponding neutral or anionic monoadducts, [Sn(C 2 F 5 ) 2 (D)] (D=PMe 3 , [Sn(C 2 F 5 ) 3 ] - ). In contrast, the utilization of sterically demanding donors, such as iPr 2 O, as well as the thermal treatment of ether complexes, [Sn(C 2 F 5 ) 2 (D) n ] (D=Et 2 O, THF), leads to the formation of oligomeric and cyclic stannylene moieties [Sn(C 2 F 5 ) 2 ] n . The reactivity of H 2 Sn(C 2 F 5 ) 2 and the donor-stabilized stannylenes was proven by hydrostannylation and complexation reactions with tetracarbonylnickel and bimetallic compounds. In the latter case, a donor-dependent stannylene or distannylene insertion into the metal-metal bond was observed., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The first C5-protonated abnormal N-heterocyclic carbene (aNHC), PhC{N(2,6-iPr 2 C 6 H 3 )} 2 CHC: (4) is readily accessible by C4-deprotonation of [ArC{N(2,6-iPr 2 C 6 H 3 )} 2 CHCH]X (3 a-X) (Ar=Ph, X=Br or I) with a base. The aNHC 4 is stable at 298 K in [D 8 ]THF solution and has been spectroscopically characterized. The facile availability of 4 enables the synthesis of a series of main-group compounds as well as transition-metal complexes featuring a new phosphorus-aNHC hybrid ligand. Double deprotonation of [ArC{N(2,6-iPr 2 C 6 H 3 )} 2 CHCH]X (Ar=Ph, 3 a-X (X=Br or I); 4-Tol, 3 b-Br; 4-DMP, 3 c-Br; Tol=MeC 6 H 4 , DMP=Me 2 NC 6 H 4 ) with nBuLi yields the C4,C5-ditopic carbanionic aNHCs, [ArC{N(2,6-iPr 2 C 6 H 3 )} 2 (C:) 2 ]Li(THF) n (Ar=Ph, 13 a; 4-Tol, 13 b; 4-DMP, 13 c), which on treatment with Ph 2 PCl affords cationic vicinal bisphosphine derivatives [ArC{N(2,6-iPr 2 C 6 H 3 )} 2 {C(PPh 2 } 2 ]X (Ar=Ph, 14 a-X, X=Br or I; 4-Tol, 14 b-Br; 4-DMP, 14 c-Br)., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A versatile two-step synthesis of tris(pentafluoroethyl)stannane, HSn(C 2 F 5 ) 3 , is presented. Electron-withdrawing C 2 F 5 groups significantly influence the polarity of the tin-hydrogen bond, which allows facile deprotonation of the compound, even in water. The utility of this electron-deficient stannane was illustrated in hydrostannylations of alkenes and alkynes, as well as in dehalogenation reactions. The remarkably high reactivity of HSn(C 2 F 5 ) 3 is demonstrated in fast hydrostannylations, even in the absence of activators, whereby the regioselectivity of this process turns out to be solvent dependent. It is of great advantage that in dehalogenation reactions volatile halogenotris(pentafluoroethyl)stannanes, XSn(C 2 F 5 ) 3 (X=I, Br), are formed that allow facile separation of the tin-containing byproducts from the reaction mixtures., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The unstable dithiocarboxylic acids dithioacetic acid, 2-methyl-dithiopropionic acid, 2,2-dimethyl-dithiopropionic acid and dithiobenzoic acid were synthesized and characterized by NMR spectroscopy and GC/MS. The stable dithiocarboxylic acids 2,4,6-trimethyl benzoic acid, 2,4,6-tri-iso-propylbenzoic acid and 2,6-dimesityl benzoic acid were synthesized, isolated and characterized by spectroscopic methods and in parts by mass spectrometry and X-ray crystallography. The new data were used to re-evaluate literature data on the synthesis, spectroscopy and structural data of dithiocarboxylic acids as a fundamental class of organic compounds in general., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Pentafluoroethyllithium, LiC 2 F 5 , has been established as an efficient and versatile reagent for the transfer of the pentafluoroethyl unit to a number of electrophiles. Here, the stability of this species up to -40 °C is of advantage, particularly in comparison to its smaller congener LiCF 3 . The usual production of LiC 2 F 5 , however, from gaseous HC 2 F 5 or IC 2 F 5 and strong bases requires specially designed apparatuses, which severely impeded its value as a laboratory reagent. In this contribution we communicate an alternative gas-free and highly efficient protocol for the synthesis of LiC 2 F 5 from the already commercialized stannate salt [PPh 4 ][Sn(C 2 F 5 ) 5 ]. The [Sn(C 2 F 5 ) 5 ] - anion represents not only the first example of a structurally characterized hypervalent pentaalkylstannate but also serves as a precursor for the synthesis of the homoleptic tetrakis(pentafluoroethyl)stannane, Sn(C 2 F 5 ) 4 . The reaction of the latter with n-butyllithium provides an insight into the mechanism of LiC 2 F 5 generation., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Terretonin N ( 1 ), a new highly oxygenated and unique tetracyclic 6-hydroxymeroterpenoid, was isolated together with seven known compounds from the ethyl acetate extract of a solid-state fermented culture of Nocardiopsis sp. Their structures were elucidated by spectroscopic analysis. The structure and absolute configuration of 1 were unambiguously determined by X-ray crystallography. The isolation and taxonomic characterization of Nocardiopsis sp. is reported. The antimicrobial activity and cytotoxicity of the strain extract and compound 1 were studied using different microorganisms and a cervix carcinoma cell line, respectively., Competing Interests: The authors declare no conflict of interest.

Peptidotriazolamers are hybrid foldamers combining features of peptides and triazolamers-repetitive peptidomimetic structures with triazoles replacing peptide bonds. We report on the synthesis of a new class of peptidomimetics, containing 1,5-disubstituted 1,2,3-triazoles in an alternating fashion with amide bonds and the analysis of their conformation in solid state and solution. Homo- or heterochiral peptidotriazolamers were obtained from enantiomerically pure propargylamines with stereogenic centers in the propargylic position and α-azido esters by ruthenium-catalyzed azide-alkyne cycloaddition (RuAAC) under microwave conditions in high yields. With such building blocks the peptidotriazolamers are readily available by solution phase synthesis. While the conformation of the homochiral peptidotriazolamer Boc-Ala[5Tz]Phe-Val[5Tz]Ala-Leu[5Tz]Val-OBzl resembles that of a β VIa1 turn, the heterochiral peptidotriazolamer Boc-d-Ala[5Tz]Phe-d-Val[5Tz]Ala-d-Leu[5Tz]Val-OBzl adopts a polyproline-like repetitive structure., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Reactions between 1,8-dichloroanthracenes with substituents in position 10 and ortho -chloroaryne afford mixtures of 1,8,13- ( syn ) and 1,8,16-trichlorotriptycenes ( anti ). The syn / anti ratio is dependent on these substituents. Electropositive substituents like SiMe 3 and GeMe 3 lead to preferred formation of the syn -isomer, whereas CMe 3 groups exclusively afford the anti -isomer. Different quantum chemical calculations including location of transition states give conflicting results, but indicate the importance of dispersion forces for an at least qualitative prediction of results. The syn -trichlorotriptycenes with SiMe 3 and GeMe 3 substituents were characterized by using NMR spectroscopy, mass spectrometry, and X-ray diffraction experiments., Competing Interests: The authors declare no conflict of interest.

The synthesis, structure, and reactivity of the first silylene-functionalized N-heterocyclic carbene (Si-NHC), {(L 1 )Si}(L 2 ), (3) (L 1 =PhC(NtBu) 2 , L 2 =CCH(CNAr) 2 C:, Ar=2,6-diisopropylphenyl) are reported. The ditopic carbanionic-NHC (dc-NHC), [Li(L 2 )] ∞ (1) reacts with the monochlorosilylene (L 1 )SiCl (2) to afford 3. The HOMO of 3 is the silylene lone-pair orbital, whereas the HOMO-1 is located at the carbene carbon atom. Both Si II and C II functionalities of 3 undergo reactions with chalcogens to give heavier ketone derivatives {(L 1 )Si(E)}L 2 (E) (E=S, 4; Se, 5; and Te, 6). Compounds 4-6 feature a highly polarized Si δ+ -E δ- bond with a formal charge of -0.72 (4), -0.64 (5), and -0.50 e (6) on the E atom. The Wiberg bond indices of 1.64 (4), 1.66 (5), and 1.63 (6) for the Si-E bond however indicate a moderate p π -p π interaction between Si and E atoms. Compound 3 functions as a reducing agent and induces disproportionation of Si 2 Cl 6 to yield the silyl-functionalized NHC, {(L 1 )SiCl 2 }(L 2 ) (7). Treatment of 3 with HSiCl 3 leads to the formation of the silyl-functionalized imidazolium salt [{(L 1 )SiCl 2 }(L 2 H)]Cl (8). The silylene moiety of 3 readily forms the iridium-silylene complex [{(L 2 )(L 1 )Si}Ir(cod)Cl] (9) featuring a free NHC ligand on treatment with [Ir(cod)(μ-Cl)] 2 ., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The amide moiety of peptides can be replaced for example by a triazole moiety, which is considered to be bioisosteric. Therefore, the carbonyl moiety of an amino acid has to be replaced by an alkyne in order to provide a precursor of such peptidomimetics. As most amino acids have a chiral center at C α , such amide bond surrogates need a chiral moiety. Here the asymmetric synthesis of a set of 24 N -sulfinyl propargylamines is presented. The condensation of various aldehydes with Ellman's chiral sulfinamide provides chiral N- sulfinylimines, which were reacted with (trimethylsilyl)ethynyllithium to afford diastereomerically pure N -sulfinyl propargylamines. Diverse functional groups present in the propargylic position resemble the side chain present at the C α of amino acids. Whereas propargylamines with (cyclo)alkyl substituents can be prepared in a direct manner, residues with polar functional groups require suitable protective groups. The presence of particular functional groups in the side chain in some cases leads to remarkable side reactions of the alkyne moiety. Thus, electron-withdrawing substituents in the C α -position facilitate a base induced rearrangement to α,β-unsaturated imines, while azide-substituted propargylamines form triazoles under surprisingly mild conditions. A panel of propargylamines bearing fluoro or chloro substituents, polar functional groups, or basic and acidic functional groups is accessible for the use as precursors of peptidomimetics.

Syntheses of salts containing the tris(pentafluoroethyl)stannate(II) ion, [Sn(C 2 F 5 ) 3 ] - , were achieved through deprotonation of the corresponding stannane, HSn(C 2 F 5 ) 3 , as well as by direct pentafluoroethylation of SnCl 2 with LiC 2 F 5 . The electron-withdrawing substituents have substantial influence on the stability and reactivity of the anion as documented by its treatment with main group halides. Alkyl halides (R-X) underwent nucleophilic substitutions to afford RSn(C 2 F 5 ) 3 , whereas Si, Ge, Sn, P halides gave rise to oxidation processes yielding hypervalent [SnX 2 (C 2 F 5 ) 3 ] - salts (X=Cl, Br, I). Moreover the unsymmetrical distannane, nBu 3 SnSn(C 2 F 5 ) 3 , was disclosed as an alternative precursor for the Sn(C 2 F 5 ) 3 moiety. Although neither the solid state structure nor its spectra in alkane solution reveal unexpected peculiarities, unusual dissociation of the compound in coordinating solvents into [nBu 3 Sn(D) n ] + and [Sn(C 2 F 5 ) 3 ] - ions was observed., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Three compounds with phenyl and pentafluorophenyl rings bridged by (CH 2 ) 3 and (CH 2 ) 2 SiMe 2 units were synthesized by hydrosilylation and C-C coupling reactions. Their solid-state structures are dominated by intermolecular π stacking interactions, primarily leading to dimeric or chain-type aggregates. Analysis of free molecules in the gas phase by electron diffraction revealed the most abundant conformer to be significantly stabilized by intramolecular π-π interactions. For the silicon compounds, structures characterized by σ-π interactions between methyl and pentafluorophenyl groups are second lowest in energy and cannot be excluded completely by the gas electron diffraction experiments. C 6 H 5 (CH 2 ) 3 C 6 F 5 , in contrast, is present as a single conformer. The gas-phase structures served as a reference for the evaluation of a series of (dispersion-corrected) quantum-chemical calculations., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A highly efficient nickel catalysed method for the direct C2-arylation of N-heterocyclic carbenes (NHCs) is reported. This protocol enables a facile access to C2-arylated imidazolium salts (NHC-Ar)X (X = Cl, Br, I or OTf). Experimental and theoretical studies suggest the viability of a Ni(i)/Ni(ii) catalytic pathway in which the dinuclear Ni(i) species [(NHC)NiX] 2 plays a key role.