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Diradicals based on a meta-quinodimethane (m-QDM) scaffold generally have a triplet ground state and are rather scarce. Herein, m-QDM-based non-Kekulé diradicals [3,3'-(NHC) 2 BP] (3-NHC) (NHC = SIPr = C{N(Dipp)CH 2 } 2 ; IPr = C{N(Dipp)CH} 2 , Me-IPr = C{N(Dipp)CMe} 2 ; Dipp = 2,6-iPr 2 C 6 H 3 ; BP = 1,1'-C 6 H 4 C 6 H 4 ) featuring N-heterocyclic carbene (NHC) pendants are reported as crystalline solids. The EPR spectra of 3-NHC show both allowed (Δm s = 1) and forbidden (Δm s = 2; 'half-field') transitions characteristic for triplet diradicals. Variable temperature EPR studies however reveal a singlet ground state for 3-SIPr. Consistent with the EPR spectra, calculations predict a remarkably small singlet-triplet energy gap (ΔE ST ≤ 0.26 kcal/mol) for the 3-NHC compounds. The calculated singlet diradical character for the ground states of the 3-NHC compounds amounts to ~99 %., (© 2024 The Author(s). Chemistry - A European Journal published by Wiley-VCH GmbH.)

The reaction of [Ga(C 2 F 5 ) 3 (FSiMe 3 )] with chlorotrimethylsilane leads to the selective substitution of the α-fluorine atoms by chlorine atoms and thus to the formation of [Ga(CCl 2 CF 3 ) 3 (FSiMe 3 )]. The corresponding chlorogallate ion, [Ga(CCl 2 CF 3 ) 3 Cl] - , could be isolated and structurally characterized as its tetraphenylphosphonium salt. The catalytic potential of [Ga(CCl 2 CF 3 ) 3 (FSiMe 3 )] was demonstrated via the chlorodefluorination of Me 3 SiCF 3 , 2,2-difluoropropane and [PPh 4 ][Ga(C 2 F 5 ) 4 ]., (© 2024 The Author(s). Chemistry - A European Journal published by Wiley-VCH GmbH.)

N-Heterocyclic carbene (NHC) analogues of Wittig hydrocarbon, [(NHC)(Stil)(NHC)] (3a-c) (NHC = SIPr (1a) = C[N(Dipp)CH 2 ] 2 , Dipp = 2,6-iPr 2 C 6 H 3 ; IPr (1b) = C[N(Dipp)CH] 2 ; Me-IPr (1c) = C[N(Dipp)CMe] 2 and Stil = C 6 H 4 CHCHC 6 H 4 ) have been reported as crystalline solids. 3a-c are prepared by two-electron reductions of the corresponding bis-1,3-imidazoli(ni)um bromides [(NHC)(Stil)NHC)](Br) 2 (2a-c) with KC 8 in >94 % yields. 2a-c are accessible by the nickel catalyzed direct C-C coupling of NHCs (1a-c) with (E)-4,4'-dibromostilbene. One-electron oxidation of 3a,b yields the corresponding radical cations [(NHC)(Stil)NHC)]B(C 6 F 5 ) 4 4a,b. All compounds have been characterized by UV-Vis/NMR/EPR spectroscopy as well as 2a, 3a, and 3b by single crystal X-ray diffraction. The electronic structures of representative systems have been analyzed by quantum chemical calculations., (© 2024 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Carbocyclic aluminium halides [(ADC)AlX 2 ] 2 (2-X) (X=F, Cl, and I) based on an anionic dicarbene (ADC=PhC{N(Dipp)C} 2 , Dipp = 2,6-iPr 2 C 6 H 3 ) framework are prepared as crystalline solids by dehydrohalogenations of the alane [(ADC)AlH 2 ] 2 (1). KC 8 reduction of 2-I affords the peri-annulated Al(III) compound [(ADC H )AlH] 2 (4) (ADC H= PhC{N(Dipp)C 2 (Dipp H )N}, Dipp H =2-iPr,6-(Me 2 C)C 6 H 3 )) as a colorless crystalline solid in 76 % yield. The formation of 4 suggests intramolecular insertion of the putative bis-aluminylene species [(ADC)Al] 2 (3) into the methine C-H bond of HCMe 2 group. Calculations predict singlet ground state for 3, while the conversion of 3 into 4 is thermodynamically favored by 61 kcal/mol. Compounds 2-F, 2-Cl, 2-I, and 4 have been characterized by NMR spectroscopy and their solid-state molecular structures have been established by single crystal X-ray diffraction., (© 2024 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Herein, reactivity studies of a cyclic bis-hydridostannylene [(ADC)SnH] 2 (1-H 2 ) (ADC=PhC{(NDipp)C} 2 ; Dipp=2,6-iPr 2 C 6 H 3 ) with various unsaturated organic substrates are reported. Reactions of terminal alkynes (RC≡CH) with 1-H 2 afford mixed acetylide-vinyl-functionalized bis-stannylenes via dehydrogenation and hydrostannylation. Treatment of 1-H 2 with PhC≡CCH 3 gives a unique distannabarrelene via dehydrogenative C (sp3) -H stannylation and hydrostannylation of the C≡CCH 3 moiety. 1-H 2 undergoes dehydrogenative [2+2]-cycloaddition reactions with diphenylacetylene, azobenzene, acetone, benzophenone, and benzaldehyde to form the 1,4-distannabarrelene derivatives. The elimination of H 2 in these reactions suggests the masked-diradical property of 1-H 2 . In fact, these [2+2]-cycloaddition products are also accessible on treatments of the Sn(I) diradicaloid [(ADC)Sn] 2 (1) with appropriate reagents. All compounds have been characterized by multinuclear NMR spectroscopy and single crystal X-ray diffraction. Moreover, the catalytic activity of 1-H 2 has been shown for the hydroboration of unsaturated substrates., (© 2024 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Herein, ring-opening of mesoionic carbenes (iMICs) (iMIC=[ArC{N(Dipp)} 2 C(SiMe 3 )C:) (Dipp=2,6-iPr 2 C 6 H 3 , Ar=Ph, 4-Me 2 NC 6 H 4 or 4-PhC 6 H 4 ) based on an 1,3-imidazole scaffold to yield N-ethynylformimidamide (eFIM) derivatives as crystalline solids (eFIM={(Dipp)N=C(Ar)N(Dipp)}C≡CSiMe 3 ) is reported. eFIMs are thermally stable under inert gas atmosphere and show moderate air stability (t 1/2= 3 h for Ar=Ph). eFIMs are excellent surrogates of iMICs, which generally have a limited shelf-life, and readily undergo ring-closing click reactions with a variety of main-group as well as transition metal Lewis acids to form hitherto challenging iMIC-compounds in good to excellent yields. In addition to the relevance of eFIMs in the synthesis of iMIC-compounds, quantification of the stereoelectronic properties of a representative iMIC (Ar=Ph) by experimental and theoretical methods suggests remarkably σ-donor property and steric profile of these new ligand sets., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Cyclic organoalane compounds [(ADC Ar )AlH 2 ] 2 (ADC Ar = ArC{(DippN)C} 2 ; Dipp = 2,6-iPr 2 C 6 H 3 ; Ar = Ph or 4-PhC 6 H 4 (Bp)) based on anionic dicarbene (ADC) frameworks have been reported as crystalline solids. Treatments of Li(ADC Ar ) with LiAlH 4 at room temperature afford [(ADC Ar )AlH 2 ] 2 with the concomitant release of LiH. Compounds [(ADC Ar )AlH 2 ] 2 are stable crystalline solids and are freely soluble in common organic solvents. They are annulated tricyclic compounds with an almost planar central C 4 Al 2 -core embedded between two peripheral 1,3-imidazole (C 3 N 2 ) rings. At room temperature, [(ADC Ph )AlH 2 ] 2 readily reacts with CO 2 to form two- and four-fold hydroalumination products [(ADC Ph )AlH(OCHO)] 2 and [(ADC Ph )Al(OCHO) 2 ] 2 , respectively. Further hydroalumination reactivity of [(ADC Ph )AlH 2 ] 2 has been shown with isocyanate (RNCO) and isothiocyanate (RNCS) species (R=alkyl or aryl group). All compounds have been characterized by NMR spectroscopy, mass spectrometry, and single-crystal X-ray diffraction., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

The two oxygen-bridged geminal frustrated Lewis pairs (FLP) tBu 2 P-O-AlBis 2 (Bis=CH(SiMe 3 ) 2 ; 1) and tBu 2 P-O-Si(C 2 F 5 ) 3 (2) were reacted with the heterocumulenes PhNCO, PhOCN, PhNCS, CS 2 and PhNSO as well as SO 2 . With isocyanate and cyanate, both 1 and 2, form addition products under formation of five-membered rings. With CS 2 , isothiocyanate and sulfinylaniline, only 1 forms stable adducts, whereas 2 shows reactivity towards sulfinylaniline, but the product decomposed after a few minutes. The reaction of 1 with SO 2 led to partial cleavage of the P-O-Al and Al-C units, as confirmed by X-ray diffraction studies of a complex aggregate. The reaction of 2 with SO 2 affords the 1,2-addition product. All adducts were characterized by means of multinuclear NMR spectroscopy, X-ray crystallography and CHN analyses., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

In the rising field of organoindium chemistry little is known about the perfluoroorganyl-substituted indium compounds. The increasing use of indium reagents is explained by their high stability and tolerance towards water and functional groups. Here we report on the synthesis of the novel tetrakis(pentafluoroethyl)indate, [In(C 2 F 5 ) 4 ] - , and its characterization in salts with the cations [Li(thf) 3 ] + , Cs + , [PPh 4 ] + and [H 14 O 6 ] 2+ (thf=tetrahydrofuran). To the best of our knowledge, these salts constitute the first perfluoroalkylindates and, in general, the first isolated perfluoroalkylindium compounds which are fully characterized by NMR spectroscopy, mass spectrometry, elemental analysis and X-ray diffraction analysis., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

The new oxygen-bridged geminal Si/P Frustrated Lewis Pair (FLP) tBu 2 P-O-Si(C 2 F 5 ) 3 (2) is able to reversibly bind carbon dioxide at ambient temperature. We compared its reactivity towards benzil, but-3-en-2-one, nitriles and phenylacetylene to that of the Al/P FLP tBu 2 P-O-AlBis 2 (Bis=-CH(SiMe 3 ) 2 ) (1). When reacted with benzil, both, 1 and 2, form the 1,2-addition product, but in the Si/P FLP 2, the second carbonyl function additionally binds to the silicon atom. With but-3-en-2-one 2 forms the 1,2-addition product, while 1 binds in 1,4-position. The reaction with acetonitrile yielded an unexpected etheneimine adduct for both systems, while only 1 reacted with tert-butylnitrile. With benzonitrile and acrylonitrile, 2 showed reversible addition to the C≡N bond and 1 forms a stable adduct with benzonitrile. Solely 1 shows reactivity towards phenylacetylene affording a mixture of the CH deprotonation adduct tBu 2 P(H)-O-AlBis 2 (CCPh) and the FLP -C≡C 1,2-addition adduct under ring formation. All compounds were characterized by multinuclear NMR spectroscopy, XRD and elemental analysis., (© 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Mesoionic dithiolates [(MIDt Ar )Li(LiBr) 2 (THF) 3 ] (MIDt Ar ={SC(NDipp)} 2 CAr; Dipp=2,6-iPr 2 C 6 H 3 ; Ar=Ph 3 a, 3-MeC 6 H 4 (3-Tol) 3 b, 4-Me 2 NC 6 H 4 (DMP) 3 c) and [(MIDt Ph )Li(THF) 2 ] (4) are readily accessible (in≥90 % yields) as crystalline solids on treatments of anionic dicarbenes Li(ADC Ar ) (2 a-c) (ADC Ar ={C(NDipp) 2 } 2 CAr) with elemental sulfur. 3 a-c and 4 are monoanionic ditopic ligands with both the sulfur atoms formally negatively charged, while the 1,3-imidazole unit bears a formal positive charge. Treatment of 4 with (L)GeCl 2 (L=1,4-dioxane) affords the germylene (MIDt Ph )GeCl (5) featuring a three-coordinated Ge atom. 5 reacts with (L)GeCl 2 to give the Ge-Ge catenation product (MIDt Ph )GeGeCl 3 (6). KC 8 reduction of 5 yields the homoleptic germylene (MIDt Ph ) 2 Ge (7). Compounds 3 a-c and 4-7 have been characterized by spectroscopic studies and single-crystal X-ray diffraction. The electronic structures of 4-7 have been analyzed by DFT calculations., (© 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Phosphoranides are interesting hypervalent species which serve as model compounds for intermediates or transition states in nucleophilic substitution reactions at trivalent phosphorus substrates. Herein, the syntheses and properties of stable trifluoromethylphosphoranide salts are reported. [K(18-crown-6)][P(CF 3 ) 4 ], [K(18-crown-6)][P(CF 3 ) 3 F], and [NMe 4 ][P(CF 3 ) 2 F 2 ] were obtained by treatment of trivalent precursors with sources of CF 3 - or F - units. These [P(CF 3 ) 4-n F n ] - (n=0-2) salts exhibit fluorinating (n=1-2) or trifluoromethylating (n=0) properties, which is disclosed by studying their reactivity towards selected electrophiles. The solid-state structures of [K(18-crown-6)][P(CF 3 ) 4 ] and [K(18-crown-6)][P(CF 3 ) 3 F] are ascertained by single crystal X-ray crystallography. The dynamics of these compounds are investigated by variable temperature NMR spectroscopy., (© 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

The first confacial pentaoctahedron comprised of transition metal ions namely Zn II Fe III A Fe III B Fe III A Zn II has been synthesized by using a dinucleating nonadentate ligand. The face-sharing bridging mode enforces short Zn II ⋅⋅⋅Fe III A and Fe III A ⋅⋅⋅Fe III B distances of 2.83 and 2.72 Å, respectively. Ab-initio CASSCF/NEVPT2 calculations provide significant negative zero-field splittings for Fe III A and Fe III B with |D A |>|D B | with the main component along the C 3 axis. Hence, a spin-Hamiltonian comprised of anisotropic exchange, zero-field, and Zeeman term was employed. This allowed by following the boundary conditions from the theoretical results the simulation in a theory-guided parameter determination with J xy =+0.37, J z =-0.32, D A =-1.21, E A =-0.24, D B =-0.35, and E B =-0.01 cm -1 supported by simulations of high-field magnetic Mössbauer spectra recorded at 2 K. The weak but ferromagnetic Fe III A Fe III B interaction arises from the small bridging angle of 84.8° being at the switch from anti- to ferromagnetic for the face-sharing bridging mode., (© 2021 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

While alkyl-substituted siloxanes are widely known, virtually nothing is known about perfluoroalkyl siloxanes and their congener species, the silanols and silanolates. We recently reported on the tris(pentafluoroethyl)silanide ion, [Si(C 2 F 5 ) 3 ] - , which features Lewis amphoteric character deriving from the pentafluoroethyl substituents and their strong electron-withdrawing properties. Transferring this knowledge, we investigated the Lewis amphoteric behavior of the tris(pentafluoroethyl)silanolate, [Si(C 2 F 5 ) 3 O] - . In order to examine such Lewis amphoteric behavior, we first developed a strategy for the synthesis of the corresponding silanol Si(C 2 F 5 ) 3 OH, which readily condenses at room temperature to the hexakis(pentafluoroethyl)disiloxane, (C 2 F 5 ) 3 SiOSi(C 2 F 5 ) 3 . Deprotonation of Si(C 2 F 5 ) 3 OH employing a sterically demanding phosphazene base allows the characterization of the first example of a dimeric triorganosilanolate: the dianionic hexakis(pentafluoroethyl)disilanolate, [{Si(C 2 F 5 ) 3 O} 2 ] 2- , implies Lewis amphoteric character of the monomeric [Si(C 2 F 5 ) 3 O] - anion., (© 2021 The Authors. Published by Wiley-VCH GmbH.)

The renaissance of Brønsted superbases is primarily based on their pronounced capacity for a large variety of chemical transformations under mild reaction conditions. Four major set screws are available for the selective tuning of the basicity: the nature of the basic center (N, P, …), the degree of electron donation by substituents to the central atom, the possibility of charge delocalization, and the energy gain by hydrogen bonding. Within the past decades, a plethora of neutral electron-rich phosphine and phosphazene bases have appeared in the literature. Their outstanding properties and advantages over inorganic or charged bases have now made them indispensable as auxiliary bases in deprotonation processes. Herein, an update of the chemistry of basic phosphines and phosphazenes is given. In addition, due to widespread interest, their use in catalysis or as ligands in coordination chemistry is highlighted., (© 2021 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

In this work, the syntheses of non-coordinated electron-rich phenolate anions via deprotonation of the corresponding alcohols with an extremely powerful perethyl tetraphosphazene base (Schwesinger base) are reported. The application of uncharged phosphazenes renders the selective preparation of anionic phenol-phenolate and phenolate hydrates possible, which allows for the investigation of hydrogen bonding in these species. Hydrogen bonding brings about decreased redox potentials relative to the corresponding non-coordinated phenolate anions. The latter show redox potentials of up to -0.72(1) V vs. SCE, which is comparable to that of zinc metal, thus qualifying their application as organic zinc mimics. We utilized phenolates as reducing agents for the generation of radical anions in addition to the corresponding phenoxyl radicals. A tetracyanoethylene radical anion salt was synthesized and fully characterized as a representative example. We also present the activation of sulfur hexafluoride (SF 6 ) with phenolates in a SET reaction, in which the nature of the respective phenolate determines whether simple fluorides or pentafluorosulfanide ([SF 5 ] - ) salts are formed., (© 2020 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

The reaction of the strong monophosphazene base with the weakly acidic phenol leads to the formation of a phenol-phenolate anion with a moderately strong hydrogen bond. Application of the more powerful tetraphosphazene base (Schwesinger base) renders the isolation of the corresponding salt with a free phenolate anion possible. This compound represents the first species featuring the free phenolate anion [H 5 C 6 -O] - . The deprotonation of phenol derivatives with tetraphosphazene bases represents a great way for the clean preparation of salts featuring free phenolate anions and in addition allows the selective syntheses of hydrogen bonded phenol-phenolate salts. This work presents a phosphazenium phenolate salt with a redox potential of -0.72 V and its capability for the selective activation of the chemically inert greenhouse gas SF 6 . The performed two-electron reduction of SF 6 leads to phosphazenium pentafluorosulfanide ([SF 5 ] - ) and fluoride salts., (© 2020 The Authors. Published by Wiley-VCH GmbH.)

Metalloradicals are key species in synthesis, catalysis, and bioinorganic chemistry. Herein, two iron radical cation complexes (3-E)GaCl 4 [(3-E) .+ = [{(IPr)C(Ph)E} 2 Fe(CO) 3 ] .+ , E = P or As; IPr = C{(NDipp)CH} 2 , Dipp = 2,6-iPr 2 C 6 H 3 ] are reported as crystalline solids. Treatment of the divinyldipnictenes {(IPr)C(Ph)E} 2 (1-E) with Fe 2 (CO) 9 affords [{(IPr)C(Ph)E} 2 Fe(CO) 3 ] (2-E), in which 1-E binds to the Fe atom in an allylic (η 3 -EEC vinyl ) fashion and functions as a 4e donor ligand. Complexes 2-E undergo 1e oxidation with GaCl 3 to yield (3-E)GaCl 4 . Spin density analysis revealed that the unpaired electron in (3-E) .+ is mainly located on the Fe (52-64 %) and vinylic C (30-36 %) atoms. Further 1e oxidation of (3-E)GaCl 4 leads to unprecedented η 3 -EEC vinyl to η 3 -EC vinyl C Ph coordination shuttling to form the dications (4-E)(GaCl 4 ) 2 ., (© 2021 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Indigoids represent natural product-based compounds applicable as organic semiconductors and photoresponsive materials. Yet modified indigo derivatives are difficult to access by chemical synthesis. A biocatalytic approach applying several consecutive selective C-H functionalizations was developed that selectively provides access to various indigoids: Enzymatic halogenation of l-tryptophan followed by indole generation with tryptophanase yields 5-, 6- and 7-bromoindoles. Subsequent hydroxylation using a flavin monooxygenase furnishes dibromoindigo that is derivatized by acylation. This four-step one-pot cascade gives dibromoindigo in good isolated yields. Moreover, the halogen substituent allows for late-stage diversification by cross-coupling directly performed in the crude mixture, thus enabling synthesis of a small set of 6,6'-diarylindigo derivatives. This chemoenzymatic approach provides a modular platform towards novel indigoids with attractive spectral properties., (© 2021 The Authors. Published by Wiley-VCH GmbH.)

The reactivity of the geminal frustrated Lewis pair (FLP) (F 5 C 2 ) 3 SnCH 2 P(tBu) 2 (1) was explored by reacting it with a variety of small molecules (PhOCN, PhNCS, PhCCH, tBuCCH, H 3 CC(O)CH=CH 2 , Ph[C(O)] 2 Ph, PhN=NPh and Me 3 SiCHN 2 ), featuring polar or non-polar multiple bonds and/or represent α,β-unsaturated systems. While most adducts are formed readily, the binding of azobenzene requires UV-induced photoisomerization, which results in the highly selective complexation of cis-azobenzene. In the case of benzil, the reaction does not lead to the expected 1,2- or 1,4-addition products, but to the non-stereoselective (tBu) 2 PCH 2 -transfer to a prochiral keto function of benzil. All adducts of 1 were characterised by means of multinuclear NMR spectroscopy, elemental analyses and X-ray diffraction experiments., (© 2020 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Herein, we report the first 1,4-diphosphinine-1,4-diide compound [(ADC Ph )P] 2 (5-Ph) (ADC Ph =PhC{(NDipp)C} 2 ; Dipp=2,6-iPr 2 C 6 H 3 ) derived from an anionic dicarbene (ADC Ph ) as a red crystalline solid. Compound 5-Ph containing a 16π-electron planar fused-tricyclic ring system was obtained by the 4e reduction of [(ADC Ph )PCl 2 ] 2 (4-Ph) with Mg (or KC 8 ) in a quantitative yield. Experimental and computational results imply that the central 8π-electrons C 4 P 2 ring of 5-Ph, which is fused between two 6π-electrons C 3 N 2 aromatic rings, is antiaromatic. Thus, each of the phosphorus atoms of 5-Ph has two electron-lone-pairs, one in a p-type orbital is in conjugation with the C=C bonds of the C 4 P 2 ring, while the second resides in a σ-symmetric orbital. This can be shown with the gold complex [(ADC Ph )P(AuCl) 2 ] 2 (6-Ph) obtained by reacting 5-Ph with (Me 2 S)AuCl. A mixture of 5-Ph and 4-Ph undergoes comproportionation in the presence of MgCl 2 to form the intermediate oxidation state compound [(ADC Ar )P] 2 (MgCl 4 ) (7-Ph), which is an aromatic species., (© 2020 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

The reaction of a saline phosphazenium hydroxide hydrate with siloxanes led to a novel kind of silanol-silanolate anions. The weakly coordinating behavior of the cation renders the formation of silanol-silanolate hydrogen bonds possible, which otherwise suffer from detrimental silanolate-oxygen cation interactions. We investigated the influence of various weakly coordinating cations on silanol-silanolate motifs, particularly with regard to different cation sizes. While large cations favor the formation of intramolecular hydrogen bonds resulting in cyclic structures, the less bulky tetramethyl ammonium cation encourages the formation of polyanionic silanol-silanolate chains in the solid state., (© 2020 The Authors. Published by Wiley-VCH GmbH.)

The reactivity of the frustrated Lewis pair (FLP) (F 5 C 2 ) 3 SnCH 2 P(tBu) 2 (1) was investigated with respect to the activation of elemental hydrogen. The reaction of 1 at elevated hydrogen pressure afforded the intramolecular phosphonium stannate(II) (F 5 C 2 ) 2 SnCH 2 PH(tBu) 2 (3). It was characterized by means of multinuclear NMR spectroscopy and single crystal X-ray diffraction. NMR experiments with the two isotopologues H 2 and D 2 showed it to be formed via an H 2 adduct (F 5 C 2 ) 3 HSnCH 2 PH(tBu) 2 (2) and the subsequent formal reductive elimination of pentafluoroethane; this is supported by DFT calculations. Parahydrogen-induced polarization experiments revealed the formation of a second product of the reaction of 1 with H 2 , [HP(tBu) 2 Me][Sn(C 2 F 5 ) 3 ] (4), in 1 H NMR spectra, whereas 2 was not detected due to its transient nature., (© 2020 The Authors. Published by Wiley-VCH GmbH.)

Several ethylenedioxy-bridged bisarenes with a variety of type and number of aryl groups were synthesized to study non-covalent dispersion-driven inter- and intramolecular aryl-aryl interactions in the solid state and gas phase. Intramolecular interactions are preferably found in the gas phase. DFT calculations with and without dispersion correction show larger interacting aromatic groups increase the stabilization energy of folded conformers and decrease the intermolecular centroid-centroid distance. Single-molecule structures generally adopt folded conformations with short intramolecular aryl-aryl contacts. Gas electron diffraction experiments were performed exemplarily for 1-(pentafluorophenoxy)-2-(phenoxy)ethane. A new procedure for structure refinement was developed to deal with the conformational complexity of such molecules. The results are an experimental confirmation of the existence of folded conformations of this molecule with short intramolecular aryl-aryl distances in the gas phase. Solid-state structures are dominated by stretched structures without intramolecular aryl-aryl interactions but interactions with neighboring molecules., (© 2020 The Authors. Published by Wiley-VCH GmbH.)

While perfluorinated aryl, aryloxy and alkoxy aluminum species are well-established as weakly coordinating anions (WCAs), corresponding perfluoroalkyl aluminum derivatives are virtually unknown. Reaction of Si(C 2 F 5 ) 3 CH 3 with Li[AlH 4 ] afforded the tetrakis(pentafluoroethyl)aluminate, [Al(C 2 F 5 ) 4 ] - . Several salts of the [Al(C 2 F 5 ) 4 ] - ion were synthesized and characterized by NMR spectroscopic methods, mass spectrometry, X-ray diffraction studies and elemental analysis., (© 2020 The Authors. Published by Wiley-VCH GmbH.)

Crystalline 1,4-distannabarrelene compounds [(ADC Ar ) 3 Sn 2 ]SnCl 3 (3-Ar) (ADC Ar ={ArC(NDipp) 2 CC}; Dipp=2,6-iPr 2 C 6 H 3 , Ar=Ph or DMP; DMP=4-Me 2 NC 6 H 4 ) derived from anionic dicarbenes Li(ADC Ar ) (2-Ar) (Ar=Ph or DMP) have been reported. The cationic moiety of 3-Ar features a barrelene framework with three coordinated Sn II atoms at the 1,4-positions, whereas the anionic unit SnCl 3 is formally derived from SnCl 2 and chloride ion. The all carbon substituted bis-stannylenes 3-Ar have been characterized by NMR spectroscopy and X-ray diffraction. DFT calculations reveal that the HOMO of 3-Ph (ϵ=-6.40 eV) is mainly the lone-pair orbital at the Sn II atoms of the barrelene unit. 3-Ar readily react with sulfur and selenium to afford the mixed-valence Sn II /Sn IV compounds [(ADC Ar ) 3 SnSn(E)](SnCl 6 ) 0.5 (E=S 4-Ar, Ar=Ph or DMP; E=Se 5-Ph)., (© 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

Pd-mediated reactions have emerged as a powerful tool for the site-selective and bioorthogonal late-stage diversification of amino acids, peptides and related compounds. Indole moieties of tryptophan derivatives are susceptible to C 2 H-activation, whereas halogenated aromatic amino acids such as halophenylalanines or halotryptophans provide a broad spectrum of different functionalisations. The compatibility of transition-metal-catalysed cross-couplings with functional groups in peptides, other biologically active compounds and even proteins has been demonstrated. This Review primarily compiles the application of different cross-coupling reactions to modify halotryptophans, halotryptophan containing peptides or halogenated, biologically active compounds derived from tryptophan. Modern approaches use regio- and stereoselective biocatalytic strategies to generate halotryptophans and derivatives on a preparative scale. The combination of bio- and chemocatalysis in cascade reactions is given by the biocompatibility and bioorthogonality of Pd-mediated reactions., (© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

Three 1,2-diaryltetramethyldisilanes X 5 C 6 -(SiMe 2 ) 2 -C 6 X 5 with two C 6 H 5 , C 6 F 5 , or C 6 Cl 5 groups were studied concerning the importance of London dispersion driven interactions between their aryl groups. They were prepared from 1,2-dichlorotetramethyldisilane by salt elimination. Their structures were determined in the solid state by X-ray diffraction and for free molecules by gas electron-diffraction. The solid-state structures of the fluorinated and chlorinated derivatives are dominated by aryl-aryl interactions. Unexpectedly, Cl 5 C 6 -(SiMe 2 ) 2 -C 6 Cl 5 exists exclusively as an eclipsed syn-conformer in the gas phase with strongly distorted Si-C 6 Cl 5 units due to strong intramolecular interactions. In contrast, F 5 C 6 -(SiMe 2 ) 2 -C 6 F 5 reveals weaker interactions. The contributions to the total interaction energy were analyzed by SAPT calculations., (© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

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.)

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.)

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 anisotropy barrier of polynuclear single-molecule magnets is expected to be higher with less tunneling the better stabilized the spin ground state is so that less M S mixing in the ground state and with excited spin states occur. We have realized this experimentally in two structurally related heptanuclear SMMs: the triplesalen-based [Mn III 6 Cr III ] 3+ and the triplesalalen-based *[Mn III 6 Cr III ] 3+ . The ligand system triplesalen was developed to enforce ferromagnetic interactions by the spin-polarization mechanism. However, we found weak antiferromagnetic couplings, that we assigned to an inefficient spin-polarization by a heteroradialene formation. To prevent this heteroradialene formation, the triplesalalen ligand H 6 talalen t Bu 2 was designed. Here, we present the building block [(talalen t Bu 2 )Mn III 3 ] 3+ and its application for the assembly of [{(talalen t Bu 2 )Mn III 3 } 2 {Cr III (CN) 6 }] 3+ (=*[Mn III 6 Cr III ] 3+ ). Both the trinuclear and heptanuclear complexes are SMMs. The comparison to the related triplesalen complex [(feld t Bu 2 )Mn III 3 ] 3+ proves the absence of heteroradialene character and the enforcement of ferromagnetic Mn III -Mn III interactions in the (talalen t Bu 2 ) 6- complexes. This results in an increase of the barrier for spin reversal U eff from 25 K in the triplesalen-based [Mn III 6 Cr III ] 3+ SMMs to 37 K in the triplesalalen-based *[Mn III 6 Cr III ] 3+ SMM proving the success of our concept. Based on this study, the next step in the rational improvement of our SMMs is discussed., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

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.)

Carbaboranes 1,2-(EH) 2 -closo-1,2-C 2 B 10 H 10 (E=S, Se) were prepared, in the case of E=Se for the first time. Their semi-experimental equilibrium molecular structures were established by the concerted use of quantum-chemical calculations and gas electron diffraction. A method was developed and implemented to quantify the contribution of experimental data to each refined structural parameter. The accuracy of the experimental structures and those calculated at the MP2 level of theory were gauged by comparison of experimental 11 B NMR chemical shifts with quantum-chemically computed values; the inclusion of electron correlation (GIAO-MP2) provided superior results. For the purpose of geometrical prediction, the remaining group 16 elements were considered, and the icosahedral structures for E=O and Te were also computed; for E=O the same theoretical approach was used as for E=S, and for E=Te a description similar to that for E=Se was employed., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

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.)

In this contribution we present an account on pentafluoroethylated compounds of silicon, germanium and tin. The pronounced electron-withdrawing effect of the pentafluoroethyl group leads to a markedly increased Lewis acidity at the central atom which results in the stabilization of hypervalent complexes, anionic element(II) species as well as remarkable reactivities of element-element and element-hydrogen bonds. By addition to unsaturated C-C bonds or by reaction with organic halides as well as transition-metal complexes the molecules bearing a pentafluoroethyl-element group are readily accessible. Moreover, the utilization of pentafluoroethyl groups facilitates the formation of donor-stabilized germylenes and stannylenes. A series of such compounds serves as suitable pentafluoroethylation reagents. Conversely to the well-studied trifluoromethyl derivatives these compounds frequently exhibit a higher thermostability, which allows a more convenient handling., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

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.)

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 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.)

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.)

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.)

Owing to the highly electron-withdrawing C 2 F 5 groups, the tris(pentafluoroethyl)germane (C 2 F 5 ) 3 GeH represents an interesting Brønsted acidic compound. The germane is accessible by the treatment of the corresponding halogenogermanes (C 2 F 5 ) 3 GeX (X=Cl, Br) with Bu 3 SnH. After clarifying its molecular structure in the solid state by X-ray diffraction, the acidity of (C 2 F 5 ) 3 GeH was examined by treatment with different bases, for example, 1,8-bis(dimethylamino)naphthalene. The resulting germanate(II) ion [Ge(C 2 F 5 ) 3 ] - serves as a germyl group transfer reagent. The reaction with main-group and transition-metal complexes or organohalides opens access to a variety of different compounds, the structures of which were mostly determined by X-ray diffraction. The corresponding tricarbonylnickelate(0) complex [(CO) 3 NiGe(C 2 F 5 ) 3 ] - also gives information about the π-acceptor properties of the [Ge(C 2 F 5 ) 3 ] - ligand. Furthermore, hydrogermylation reactions of (C 2 F 5 ) 3 GeH with alkynes afforded different stereoisomers (α,β-cis, β-trans) depending on the respective reaction conditions and substrates., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Halogenating enzymes are increasingly attracting attention for biocatalytic C-H functionalization. Despite its importance for synthetic chemistry, selective introduction of halogens using conventional approaches often remains challenging, whereas biocatalysis offers excellent catalyst-controlled selectivity without requiring protecting groups or hazardous reagents. Owing to the high prevalence of halogenated secondary metabolites, a still growing repertoire of halogenases has been identified. Recently, flavin-dependent tryptophan halogenases came into focus for synthetic use. Nevertheless, these enzymes still suffer from severe deficiencies. Herein, current attempts in optimizing tryptophan halogenases have been compiled. Enzyme discovery, structure elucidation and mechanisms are reviewed with focus on biosynthesis of halogenated arenes. Emphasis is also given to random and rational engineering, high-throughput screening and implementation of halogenases into one-pot processes., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Four-membered biradicaloid compounds containing a N 2 E 2 (E=main group element) framework have been thoroughly investigated; however, the synthesis of stable analogues with a C 2 P 2 skeleton remains a challenge. Base-mediated double C-H functionalization of IPr=CH 2 (1) (IPr=C[N(2,6-iPr 2 -C 6 H 3 )CH] 2 ) with PCl 3 affords [{(IPr)CP} 2 Cl]Cl (2) as a royal blue solid. Treatment of 2 with KC 8 yields the stable phosphorus biradicaloid [(IPr)CP] 2 (3) featuring a four-membered C 2 P 2 ring. Compound 3 is diamagnetic and shows sharp and temperature-independent NMR resonances, revealing its singlet biradicaloid nature. The stability of 3 is attributed to the σ- and π-electron-donating property of the N-heterocyclic vinylidene [(IPr)C] group., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)