M−C Bond Homolysis in Coinage‐Metal [M(CF3)4]− Derivatives

A comparative study of the homoleptic [M(CF₃)₄]^? complexes of all three coinage metals (M=Cu, Ag, Au) reveals that homolytic M?C bond cleavage is favoured in every case upon excitation in the gas phase (CID‐MS²). Homolysis also occurs in solution by photochemical excitation. Transfer of the photogenerated CF₃^. radicals to both aryl and alkyl carbon atoms was also confirmed. The observed behaviour was rationalized by considering the electronic structure of the involved species, which all show ligand‐field inversion. Moreover, the homolytic pathway constitutes experimental evidence for the marked covalent character of the M?C bond. The relative stability of these M?C bonds was evaluated by energy‐resolved mass spectrometry (ERMS) and follows the order Cu<Ag?Au. The qualitatively similar and rather uniform behaviour experimentally observed for all three coinage metals gives no ground to suggest variation in the metal oxidation state along the group.     

N‐Heterocyclic Carbene (NHC)‐Stabilized Silanechalcogenones: NHC→Si(R2)E (E=O,S, Se,Te)

A series of N‐heterocyclic carbene‐stabilized silanechalcogenones 2 a , b (Si?O), 3 a , b (Si?S), 4 a , b (Si?Se), and 5 a , b (Si?Te) are described. The silanone complexes 2 a , b were prepared by facile oxygenation of the carbene–silylene adducts 1 a , b with N₂O, whereas their heavier congeners were synthesized by gentle chalcogenation of 1 a , b with equimolar amounts of elemental sulfur, selenium, and tellurium, respectively. These novel compounds have been isolated in a crystalline form in high yields and have been fully characterized by a variety of techniques including IR spectroscopy, ESIMS, and multinuclear NMR spectroscopy. The structures of 2 b , 3 a , 4 a , 4 b , and 5 b have been confirmed by single‐crystal X‐ray crystallography. Due to the NHC→Si donor–acceptor electronic interaction, the Si?E (E=O, S, Se, Te) moieties within these compounds are well stabilized and thus the compounds possess several ylide‐like resonance structures. Nevertheless, these species also exhibit considerable Si?E double‐bond character, presumably through a nonclassical Si?E π‐bonding interaction between the chalcogen lone‐pair electrons and two antibonding Si? N σ* orbitals, as evidenced by their high stretching vibration modes and the shortening of the Si–E distances (between 5.4 and 6.3 %) compared with the corresponding Si? E single‐bond lengths.     

Die Synthese von CF3TeTeCF3 und Reaktionen mit den Elementen Hg,Cd, Cu und Ag

The Preparation of CF₃TeTeCF₃ and Reactions with the Elements Hg, Cd, Cu, and Ag (CF₃)₂Te₂ is a main product of the photochemical reaction of (CF₃)₂Te with e.g. furan and can be separated in more than 40% yield. It quantitatively reacts with mercury and cadmium to give the new compounds (CF₃Te)₂Hg and (CF₃Te)₂Cd, respectively. With copper some CF₃? Cu compounds are formed, whereas with silver no reaction takes place.     

Use of the Wilkinson Catalyst for the ortho‐CH Heteroarylation of Aromatic Amines: Facile Access to Highly Extended π‐Conjugated Heteroacenes for Organic Semiconductors

An unprecedented catalytic system composed of the Wilkinson catalyst [Rh(PPh₃)₃Cl] and CF₃COOH enabled the highly regioselective cross‐coupling of aromatic amines with a variety of heteroarenes through dual C? H bond cleavage. This protocol provided a facile and rapid route from readily available substrates to (2‐aminophenyl)heteroaryl compounds, which may be conveniently transformed into highly extended π‐conjugated heteroacenes. The experimental studies and calculations showed that thianaphtheno[3,2‐b]indoles have large HOMO–LUMO energy gaps and low‐lying HOMO levels, and could therefore potentially be high‐performance organic semiconductors. Herein we report the first use of a rhodium(I) catalyst for oxidative C? H/C? H coupling reactions. The current innovative catalyst system is much less expensive than [RhCp*Cl₂]₂/AgSbF₆ and could open the door for the application of this approach to other types of C? H activation processes.     

Multinuclear NMR studies on CF3 substituted sulfur,selenium and tellurium compounds

A systematic investigation of thirty-four CF₃Se(II, IV) and eight CF₃Te(II, IV) compounds by ¹³C, ¹⁹F, ⁷⁷Se and ¹²⁵Te NMR spectroscopy resulted in some general features for chemical shifts and coupling constants which agree with the trends of reported ¹⁹F and new ¹³C NMR data of CF₃S(II, IV) compounds. Moreover, the NMR spectra of molecules of the type E=CXY (E = chalcogen, X, Y = halogen) and substances containing a CSe double bond have been studied. From the comparison of these NMR data with those of CF₃ substituted chalcogen compounds, a partial double bond character of the carbon-fluorine and carbon-chalcogen bond in CF₃ substituted chalcogen compounds can be derived:

     

First example of the correlated calculation of the one‐bond tellurium–carbon spin–spin coupling constants: Relativistic effects,vibrational corrections,and solvent effects

This work reports on the comprehensive calculation of the NMR one‐bond spin–spin coupling constants (SSCCs) involving carbon and tellurium, ¹J(¹²⁵Te,¹³C), in four representative compounds: Te(CH₃)₂, Te(CF₃)₂, Te(C?CH)₂, and tellurophene. A high‐level computational treatment of ¹J(¹²⁵Te,¹³C) included calculations at the SOPPA level taking into account relativistic effects evaluated at the 4‐component RPA and DFT levels of theory, vibrational corrections, and solvent effects. The consistency of different computational approaches including the level of theory of the geometry optimization of tellurium‐containing compounds, basis sets, and methods used for obtainig spin–spin coupling values have also been discussed in view of reproducing the experimental values of the tellurium–carbon SSCCs. Relativistic corrections were found to play a major role in the calculation of ¹J(¹²⁵Te,¹³C) reaching as much as almost 50% of the total value of ¹J(¹²⁵Te,¹³C) while relativistic geometrical effects are of minor importance. The vibrational and solvent corrections account for accordingly about 3–6% and 0–4% of the total value. It is shown that taking into account relativistic corrections, vibrational corrections and solvent effects at the DFT level essentially improves the agreement of the non‐relativistic theoretical SOPPA results with experiment. © 2016 Wiley Periodicals, Inc.     

Computational I(III)—X BDEs for Benziodoxol(on)e‐based Hypervalent Iodine Reagents: Implications for Their Functional Group Transfer Abilities

The first comprehensive I(III)―X (X = F, Br, CN, N₃, CF₃, etc.) bond dissociation energy (BDE) scales for benziodoxol(on)e‐based hypervalent iodine reagents have been developed by virtue of DFT calculations. Excellent correlation is observed between the I(III)―X BDEs and the X―H BDEs, offering a powerful avenue to quickly estimate the group‐transfer ability of a novel benziodoxol(on)e‐based hypervalent reagent.     

Polysulfone ionomers functionalized with benzoyl(difluoromethylenephosphonic acid) side chains for proton‐conducting fuel‐cell membranes

Polysulfones carrying benzoyl(difluoromethylenephosphonic acid) side chains were prepared and investigated for use as proton‐conducting fuel‐cell membranes. In the first step, polysulfones were lithiated and reacted with methyl iodobenzoates to prepare p‐ and o‐iodobenzoyl polysulfones. Next, the phosphonated polysulfones were prepared via CuBr‐mediated cross‐coupling reactions between the iodinated polymer and [(diethoxyphosphinyl)difluoromethyl]zinc bromide. Finally, dealkylation with bromotrimethylsilane afforded highly acidic ? CF₂? PO₃H₂ derivatives. The replacement of the iodine atoms by ? CF₂? PO₃Et₂ units was almost quantitative in the case of o‐iodobenzoyl polysulfone. Membranes based on ionomers having 0.90 mmol of phosphonic acid units/g of dry polymer took up 6 wt % water when immersed at room temperature, and conductivities up to 5 mS cm^?1 at 100 °C were recorded. This level of conductivity was comparable to that reached by a membrane based on a sulfonated polysulfone having 0.86 mmol of sulfonic acid/g of dry polymer. Thermogravimetry revealed that the aryl? CF₂? PO₃H₂ arrangement decomposed at approximately 230 °C via cleavage of the C? P bond. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 269–283, 2007.     

Reaktion von Chlornitrat mit CF3I: Isolierung von Trifluormethylchloriodnitrat CF3I(Cl)ONO2 und Kristallstruktur von Trifluormethylioddinitrat CF3I(ONO2)2

Reaction of Chlorine Nitrate with CF₃I: Isolation of Trifluormethylchloroiodinenitrate CF₃I(Cl)ONO₂ and the Crystal Structure of Trifluormethyliodinedinitrate CF₃I(ONO₂)₂ CF₃I reacts with ClONO₂ to Iodine(III)-compounds. After an addition CF₃I(Cl)ONO₂ is isolated and characterized by vibrational spectra. With surplus ClONO₂ it is formed CF₃I(ONO₂)₂. CF₃I(ONO₂)₂ crystallizes monoclinic in the space group P2₁/c with the cell parameters a = 1 024.3(6) pm, b = 873.5(6) pm, c = 873.4(6) pm and Z = 4. We measered following bonding distances: I? O: 207.3(3) and 220.8(2) pm, I? C: 221.1(4) pm and N? O: from 119.1(4) to 141.5(3) pm. Through an intermolecular I ··· O-contact the central iodine becomes a distorted plane geometry.     

Spektroskopische Charakterisierung und Kristallstruktur von Trifluormethylchloriod(III)‐trifluoracetat (CF3I(Cl)OCOCF3)

Spectroscopic Characterization and Crystal Structure of Trifluoromethyl Iodine(III) Chloride Trifluororacetate (CF₃I(Cl)OCOCF₃) The ternary iodine(III) compound CF₃I(Cl)OCOCF₃ is obtained by reaction between CF₃I(Cl)F and (CH₃)₃SiOCOCF₃ at –50 °C. The molecule was characterized by vibrational spectra, NMR‐spectra, and a crystal structure analysis. CF₃I(Cl)OCOCF₃ crystallizes monoclinic in the space group P2₁/c with a = 1102.7(1) pm, b = 785.6(1) pm, c = 989.7(1) pm, and β = 101.34(1)°.     

A Tunable Trifluoromethyliodonium Reagent

Four complexes of MCl₄ (M=Ti, Zr, Hf) with the hypervalent trifluoromethyl iodine reagent trifluoromethyl‐1,3‐dihydro‐3,3‐dimethyl‐1,2‐benziodoxole ( 1 ,=L) are described. With TiCl₄, an I?O bond cleavage occurs, leading to the formation of the trifluoromethyliodonium alcoholate complexes [Ti₂Cl₆(L)₄]Cl₂ ( 2 a ) and Ti₂Cl₈(L) ( 2 b ). Reactions with ZrCl₄ and HfCl₄ form the complexes ZrCl₄(L)₂ ( 3 ) and HfCl₄(L)₂ ( 4 ), respectively, wherein the original I?O bond is retained and elongated compared to that in free 1 . Therefore, the reactivity of 1 can be easily and practically fine‐tuned by addition of different metal chlorides, following the order ZrCl₄/HfCl₄<TiCl₄<2 TiCl₄. Complexes 2 a , 3 , and 4 are remarkably bench‐stable forms of activated reagent 1 , while 2 b is readily accessible in situ. 2 a and 2 b represent the first “real” trifluoromethyliodonium reagents derived from iodanes, that is, with the I?O bond being completely cleaved. The new complexes were shown to be useful for the trifluoromethylation of para‐toluenesulfonate under aprotic conditions.     

A Regioselective Synthesis of Benzopinacolones through Aerobic Dehydrogenative α‐Arylation of the Tertiary sp3 CH Bond of 1,1‐Diphenylketones with Aromatic and Heteroaromatic Compounds

A regioselective synthesis of symmetrical and unsymmetrical benzopinacolones through aerobic dehydrogenative α‐arylation at the tertiary sp³ C?H bond of substituted 1,1‐diphenylketones with aromatic and heteroaromatic compounds, in the presence of K₂S₂O₈ in CF₃COOH at room temperature, is described. The reaction is proposed to go via a carbocation intermediate, which could be generated directly from cleavage of the sp³ C?H bond of 1,1‐diphenylketone. Subsequent α‐arylation was achieved at the methene sp³ carbon atom of the substituted ketone. A variety of substituted aromatic and heteroaromatic compounds were compatible with this reaction. In addition, benzopinacolones were converted into sterically hindered, tetrasubstituted alkenes and polycyclic aromatic compounds.     

Group 13 Ligand Supported Heavy‐Metal Complexes: First Structural Evidence for Gallium–Lead and Gallium–Mercury Bonds

Heavy‐metal complexes of lead and mercury stabilized by Group 13 ligands were derived from the oxidative addition of Ga(ddp) (ddp=HC(CMeNC₆H₃‐2,6‐iPr₂)₂, 2‐diisopropylphenylamino‐4‐diisopropyl phenylimino‐2‐pentene) with corresponding metal precursors. The reaction of Me₃PbCl and Ga(ddp) afforded compound [{(ddp)Ga(Cl)}PbMe₃] ( 1 ) composed of Ga? Pb^IV bonds. In addition, the monomeric plumbylene‐type compound [{(ddp)Ga(OSO₂CF₃)}₂Pb(thf)] ( 2 a ) with an unsupported Ga‐Pb^II‐Ga linkage was obtained by the reaction of [Pb(OSO₂CF₃)₃] with Ga(ddp) (2 equiv). Compound 2 a falls under the rare example of a discrete plumbylene‐type compound supported by a nonclassical ligand. Interesting structural changes were observed when [Pb(OSO₂CF₃)₃] ? 2 H₂O was treated with Ga(ddp) in a 1:2 ratio to yield [{(ddp)Ga(μ‐OSO₂CF₃)}₂(OH₂)Pb] ( 2 b ) at below ?10 °C. Compound 2 b consists of a bent Ga‐Pb‐Ga backbone with a bridging triflate group between the Ga? Pb bond and a weakly interacting water molecule at the gallium center. Similarly, the reaction of mercury thiolate Hg(SC₆F₅) with Ga(ddp) (2 equiv) produced the bimetallic homoleptic compounds anti‐[{(ddp)Ga(SC₆F₅)}₂Hg] ( 3 a ) and gauche‐[{(ddp)Ga(SC₆F₅)}₂Hg] ( 3 b ), respectively, with a linear Ga‐Hg‐Ga linkage. Compounds 1 – 3 were structurally characterized and these are the first examples of compounds comprised of Ga? Pb^II, Ga? Pb^IV, and Ga? Hg bonds.     

C?H and N?H bond activation in reactions of vinyl acetate,allyl cyanide,allylamine and other amines with (η-C5H5)2Rh2(CO)(CF3C2CF3)

There is activation of olefinic C? H bonds when (η-C₅H₅)₂Rh₂(CO)(CF₃C₂CF₃) is treated with vinyl acetate or allyl cyanide. These reactions are initiated by exposure to sunlight. In the vinyl acetate reaction, each of the three vinylic C? H bonds can be broken, but there is strong preference for cleavage at the substituted carbon. The products formed in these reactions are bisalkenyl complexes of the type (η-C₅H₅)₂Rh₂{μ-C(CF₃)C(CF₃)H}(μ-CR?CR′R″), and all isomers have been thoroughly characterized by NMR analysis. Similar reactions with allylamine and other amines (NH₂R, NHMe₂) occur in the dark and proceed by N? H bond cleavage. Near-quantitative amounts of the products, (η-C₅H₅)Rh₂{C(CF₃)C(CF₃)H}(C(O)NRR′) are isolated. Spectroscopic data indicate a bridging carboxamide ligand attached to the Rh? Rh bond from oxygen and nitrogen donor sites. It is proposed that coordination of O or N to rhodium has a strong influence on all of the reactions studied.     

Synthese,Strukturen und Reaktivität von [(2,4,6-Ph3C6H2)Te(μ2-O)X]2 (X  Br und I)

Synthesis, Structures, and Reactivity of [(2,4,6-Ph₃C₆H₂)Te(μ₂-O)X]₂ (X ? Br, I) [(2,4,6-Ph₃C₆H₂)Te]₂ reacts with iodine affording the aryltellurenic halide (2,4,6-Ph₃C₆H₂)TeI, which is oxidized by oxygen to yield [(2,4,6-Ph₃C₆H₂)Te(μ₂-O)I]₂. It crystallizes with two molecules of dichloromethane in the monoclinic space group P2₁/c with a unit cell of the dimensions a = 911.3(4); b = 1153.3(2); c = 2244.1(9) pm; β = 93.53(2)°, Z = 2). The analogues bromo compound [(2,4,6-Ph₃C₆H₂)Te(μ₂-O)Br]₂ is obtained by the reaction of [(2,4,6-Ph₃C₆H₂)Te(μ₂-O)I]₂ with NH₄Br. It crystallizes with two molecules of xylene in the monoclinic space group P2₁/n (a = 1067.5(5); b = 1018.4(4); c = 2486.5(8) pm; β = 101.71(2)°; Z = 2). Both compounds are built up by two (2,4,6-Ph₃C₆H₂)TeX units (X ? Br, I) which are linked by two oxgen bridges to form centrosymmetric molecules. The Te? O? Te angles are 102°. Distinct Te? O bond lengths have been found (191.4(2) and 208.6(2) pm in [(2,4,6-Ph₃C₆H₂)Te(μ₂-O)I]₂ and 189.8(4)/208.4(5 pm in the bromo compound).     

A Series of Isolable Silanoic Thio‐, Seleno‐, and Telluroesters (LSi(X)OR) with Donor‐Supported SiX Double Bonds (L=β‐Diketiminate; X=S,Se, Te)

The first silicon analogues of carbonic (carboxylic) esters, the silanoic thio‐, seleno‐, and tellurosilylesters 3 (Si?S), 4 (Si?Se), and 5 (Si?Te), were prepared and isolated in crystalline form in high yield. These thermally robust compounds are easily accessible by direct reaction of the stable siloxysilylene L(Si:)OSi(H)L′ 2 (L=HC(CMe)₂[N(aryl)₂], L′=CH[(C?CH₂)‐CMe][N(aryl)]₂; aryl=2,6‐iPr₂C₆H₃) with the respective elemental chalcogen. The novel compounds were fully characterized by methods including multinuclear NMR spectroscopy and single‐crystal X‐ray diffraction analysis. Owing to intramolecular N→Si donor–acceptor support of the Si?X moieties (X=S, Se, Te), these compounds have a classical valence‐bond N⁺–Si–X^? resonance betaine structure. At the same time, they also display a relatively strong nonclassical Si?X π‐bonding interaction between the chalcogen lone‐pair electrons (n_π donor orbitals) and two antibonding Si? N orbitals (σ*_π acceptor orbitals mainly located at silicon), which was shown by IR and UV/Vis spectroscopy. Accordingly, the Si?X bonds in the chalcogenoesters are 7.4 ( 3 ), 6.7 ( 4 ), and 6.9 % ( 5 ) shorter than the corresponding Si? X single bonds and, thus, only a little longer than those in electronically less disturbed Si?X systems (“heavier” ketones).     

Perfluormethyl-Element-Liganden. IX.. Synthese und Eigenschaften von (CF3)2EMn(CO)5 (E = P,As)

Preparation and Properties of (CF₃)₂EMn(CO)₅ (E ? P, As) The complexes (CF₃)₂EMn(CO)₅ (E ? P, As) are formed by the reaction of E₂(CF₃)₄ with HMn(CO)₅. They can be converted quantitatively to the binuclear compounds [Mn(CO)₄E(CF₃)₂]₂ in a thermal (E ? P) or photochemical (E ? P, As) process. u. v. irradiation of a 1:1 mixture gives the mixed derivative Mn₂(CO)₈As(CF₃)₂P(CF₃)₂ together with the symmetrical systems. The Mn? E bond is less reactive with HBr and Me₃SnBr than the M? E bond in derivatives of the type Me₃ME(CF₃)₂ (M ? Si, Ge, Sn; Me ? CH₃). The terminal (CF₃)₂E groups are found to be strong π-acceptor ligands.     

Zweikernkomplexe des Typs Mn2(CO)8E(CF3)2E′R (E = P,As; E′ = S,Se, Te): Darstellung und Struktur

Perfluoromethyl Element Ligands. XLII Binuclear Complexes of the Type Mn₂(CO)₈E(CF₃)₂E′R (E = P, As; E′ = S, Se, Te): Synthesis and Structure Complexes of the type Mn₂(CO)₈E(CF₃)₂E′R, in which the groups E(CF₃)₂ and E′R act as bridging ligands, are prepared either by direct reactions of Mn₂(CO)₁₀ with (F₃C)₂EE′R (E = P, As; E′ = S, Se, Te) or by substitution of the iodine bridge in the representatives Mn₂(CO)₈ E(CF₃)₂I (E = P, As) with mercury compounds Hg(E′R)₂. As a rule the binuclear systems contain four‐membered heterocycles (Mn₂EE′). However, the reactions of Mn₂(CO)₁₀ with (F₃C)₂PE′P(CF₃)₂ (E′ = S, Se) yield five‐membered rings [Mn₂P(E′P)]. The compounds have been characterized by spectroscopic (NMR, IR, MS), analytic (C, H) and X‐ray diffraction investigations. The pyramidal Mn₂E′R fragment shows dynamic behaviour in solution via inversion between two identical structures.     

Ruthenium‐Catalyzed Oxidation of Alkenes,Alkynes, and Alcohols to Organic Acids with Aqueous Hydrogen Peroxide

A protocol that adopts aqueous hydrogen peroxide as a terminal oxidant and [(Me₃tacn)(CF₃CO₂)₂Ru^III(OH₂)]CF₃CO₂ ( 1 ; Me₃tacn=1,4,7‐trimethyl‐1,4,7‐triazacyclononane) as a catalyst for oxidation of alkenes, alkynes, and alcohols to organic acids in over 80 % yield is presented. For the oxidation of cyclohexene to adipic acid, the loading of 1 can be lowered to 0.1 mol %. On the one‐mole scale, the oxidation of cyclohexene, cyclooctene, and 1‐octanol with 1 mol % of 1 produced adipic acid (124 g, 85 % yield), suberic acid (158 g, 91 % yield), and 1‐octanoic acid (129 g, 90 % yield), respectively. The oxidative C?C bond‐cleavage reaction proceeded through the formation of cis‐ and trans‐diol intermediates, which were further oxidized to carboxylic acids via C? C bond cleavage.