Fluorohalogeno compounds. II. Sonochemical approach to 3,3,3-trifluoropropionic acids

Fluoropropionic acids of the general formula CF₃CXYCO₂H ( X = F, Cl, Br ; Y = F, Cl, Br, H ) were obtained by the sonochemically promoted reaction of fluorohalogenoethanes CF₃CXYZ ( Z = Cl, Br ) with zinc and carbon dioxide. Penta- and tetrafluoroethanes ( X = Y = F and X = F, respectively ) gave good yields ( 35 – 47 % ) of the acids; with trifluoro derivatives the yields were substantially lower. Hydrogenolysis of the CCl and CBr bonds in CF₃CFClCO₂H and CF₃CFBrCO₂H afforded 2,3,3,3-tetrafluoropropionic acid.     

Halocyclization of Methyl 2‐Alkynylbenzoates to Isocoumarins Using Cupric Halides

Treatment of methyl 2‐alkynylbenzoates with two to three equivalents of CuX₂ (X = Cl or Br) in refluxing acetonitrile gave isocoumarins 2 in good to excellent chemical yields.     

Catalyse par des complexs σ-aryl-nickel de l'electroreduction en biaryles des halogenures aromatiques

In mixed THF/HPMA, electrochemical reduction of NiX₂L₂ (L = PPh₃, X = Cl or Br) yields a zerovalent nickel complex which reacts very rapidly with ArX (X = I, Br, Cl) by oxidative addition to give ArNiXL₂, which also is electroreducible. Thus it is possible to obtain a catalytic electroreduction of ArX which affords mainly biaryls when X = Cl. A mechanism is suggested according the various results especially with a view to explain the loss of catalytic activity. A clear indication of increasing activity is given when aliphatic bromides are added to the solutions.     

Co-ordination compounds of diacetyldihydrazone and diacetylbis(monomethylhydrazone)

Summary Diacetyldihydrazone (DADH) forms only six-coordinate complexes with iron(II), cobalt(II), nickel(II) and zinc(II). In M(DADH)₂X₂ (M=Fe, X=Br or I; M=Co, X=I; M=Ni, X=Cl, Br or NCS) the ligand is chelating in the [M(DADH)₃]²⁺ cations, while in M(DADH)₂X₂ (M=Co, X=Cl or Br; M=Ni, X=Cl or Br) the ligand is probably bridging and bidentate. Diacetylbismonomethylhydrazone (DAMH), by contrast, forms predominantly tetrahedral complexes M(DAMH)X₂ (M=Fe or Co, X=Cl or Br; M=Ni, X=Br; M=Co, X=NCS; M=Zn, X=Cl, Br or NCS) and some octahedral complexes M(DAMH)₂X₂ (M=Co, X=NCS; M=Ni, X=Br). The i.r. spectra, electronic spectra and magnetic moments of the complexes are discussed.     

Free radical addition of cyclopentane and cyclohexane to halogeno derivatives of 1,2-difluoroethene

Free radical addition reactions between cyclopentane and cyclohexane and a range of difluoroalkenes, CF₂CXY (X, Y = H, F, Cl, Br) gave a series of adducts bearing difluoromethylene substituents, R-CF₂-CXYH (R = c-C₅H₉ or c-C₆H₁₁), in reasonable yield even though telomerisation and halogen transfer (when X, Y = Cl, Br) can compete. Dehydrofluorination of the adducts gave several new polyhalogenated alkenes.     

Halocyclization of 2-alkynylthioanisoles by cupric halides: synthesis of 2-substituted 3-halobenzo[b]thiophenes

Reaction of 2-alkynylthioanisoles 3 with 2 equiv of CuX₂ (X=Br or Cl) in refluxing CH₃CN for 2.5 h gave the 2-substituted 3-halobenzo[b]thiophenes 4 in good yields.     

Substitution of arachno-4,6-c2b7h13 carborane

Substitution of the 4,6-C₂B₇H₁₃ cluster yields a series of 3-X-4,6-C₂H₇H₁₂ (X = Cl, Br, I or HS), 5-X-4,6-C₂B₇H₁₂ (X = Br, I, HS or Bu), and 3,5-X₂-4,6-C₂B₇H₁₁ (X = D, Cl, Br or I) derivatives whose ¹H and ¹¹B NMR spectra are reported and discussed.     

A Mechanistic Study on Reactions of Group 13 Diyls LM with Cp*SbX2: From Stibanyl Radicals to Antimony Hydrides

Oxidative addition of Cp*SbX₂ (X=Cl, Br, I; Cp*=C₅Me₅) to group 13 diyls LM (M=Al, Ga, In; L=HC[C(Me)N (Dip)]₂, Dip=2,6-iPr₂C₆H₃) yields elemental antimony (M=Al) or the corresponding stibanylgallanes [L(X)Ga]Sb(X)Cp* (X=Br 1 , I 2 ) and -indanes [L(X)In]Sb(X)Cp* (X=Cl 5 , Br 6 , I 7 ). 1 and 2 react with a second equivalent of LGa to eliminate decamethyl-1,1’-dihydrofulvalene (Cp*₂) and form stibanyl radicals [L(X)Ga]₂Sb ^. (X=Br 3 , I 4 ), whereas analogous reactions of 5 and 6 with LIn selectively yield stibanes [L(X)In]₂SbH (X=Cl 8 , Br 9 ) by elimination of 1,2,3,4-tetramethylfulvene. The reactions are proposed to proceed via formation of [L(X)M]₂SbCp* as reaction intermediate, which is supported by the isolation of [L(Cl)Ga]₂SbCp ( 11 , Cp=C₅H₅). The reaction mechanism was further studied by computational calculations using two different models. The energy values for the Ga- and the In-substituted model systems showing methyl groups instead of the very bulky Dip units are very similar, and in both cases the same products are expected. Homolytic Sb−C bond cleavage yields van der Waals complexes from the as-formed radicals ([L(Cl)M]₂Sb ^. and Cp* ^. ), which can be stabilized by hydrogen atom abstraction to give the corresponding hydrides, whereas the direct formation of Sb hydrides starting from [L(Cl)M]₂SbCp* via concerted β-H elimination is unlikely. The consideration of the bulky Dip units reveals that the amount of the steric overload in the intermediate I determines the product formation (radical vs. hydride).     

Synthesis,structure, and magnetic properties of bis (3-amino-2-chloropyridinium)tetrahalocuprate(II) [halide = Cl or Br]

The reaction of CuX₂ (X = Cl or Br) with 3-amino-2-chloropyridine in aqueous acids (HX; X = Cl or Br) yields bis(3-amino-2-chloropyridinium)tetrachlorocuprate(II) and bis(3-amino-2-chloropyridinium)tetrabromocuprate(II). Both compounds have been characterized by IR, powder X-ray diffraction, single-crystal X-ray diffraction and temperature dependent magnetic susceptibility. The compounds are isomorphous and exhibit weak antiferromagnetic interactions.     

Modulating the frontier orbitals of L(X)Ga-substituted diphosphenes [L(X)GaP]2 (X = Cl,Br) and their facile oxidation to radical cations

Modulating the electronic structures of main group element compounds is crucial to control their chemical reactivity. Herein we report on the synthesis, frontier orbital modulation, and one-electron oxidation of two L(X)Ga-substituted diphosphenes [L(X)GaP]₂ (X = Cl 2a, Br 2b; L = HC[C(Me)N(Ar)]₂, Ar = 2,6-i-Pr₂C₆H₃). Photolysis of L(Cl)GaPCO 1 gave [L(Cl)GaP]₂2a, which reacted with Me₃SiBr with halide exchange to [L(Br)GaP]₂2b. Reactions with ^MeNHC (^MeNHC = 1,3,4,5-tetramethylimidazol-2-ylidene) gave the corresponding carbene-coordinated complexes L(X)GaPP(^MeNHC)Ga(X)L (X = Cl 3a, Br 3b). DFT calculations revealed that the carbene coordination modulates the frontier orbitals (i.e. HOMO/LUMO) of diphosphenes 2a and 2b, thereby affecting the reactivity of 3a and 3b. In marked contrast to diphosphenes 2a and 2b, the cyclic voltammograms (CVs) of the carbene-coordinated complexes each show one reversible redox event at E_1/2 = −0.65 V (3a) and −0.36 V (3b), indicating their one-electron oxidation to the corresponding radical cations as was confirmed by reactions of 3a and 3b with the [FeCp₂][B(C₆F₅)₄], yielding the radical cations [L(X)GaPP(^MeNHC)Ga(X)L]B(C₆F₅)₄ (X = Cl 4a, Br 4b). The unpaired spin in 4a (79%) and 4b (80%) is mainly located at the carbene-uncoordinated phosphorus atoms as was revealed by DFT calculations and furthermore experimentally proven in reactions with ⁿBu₃SnH, yielding the diphosphane cations [L(X)GaPHP(^MeNHC)Ga(X)L]B(C₆F₅)₄ (X = Cl 5a, Br 5b). Compounds 2–5 were fully characterized by NMR and IR spectroscopy as well as by single crystal X-ray diffraction (sc-XRD), and compounds 4a and 4b were further studied by EPR spectroscopy, while their bonding nature was investigated by DFT calculations.

Carbene-coordination allowed for one-electron oxidation of diphosphenes [LGa(X)P]₂ to P-centered radicals cations 4a (X = Cl) and 4b (X = Br), in which the unpaired spin mainly reside at the carbene uncoordinated P-atoms.     

Einkristall-RöntgenStrukturanalysen von Verbindungen mit einer kovalenten Metall-Metall-Bindung. VII. Die Kristall- und Molekülstruktur von dimeren Halogenobis- (pentacarbonylrhenium)indium(III), [(Re(CO)5)2In(μ-X)]2 (X = Cl,Br, I)

Single-Crystal X-Ray Analysis of Compounds with a Covalent Metal-Metal Bond. VII. Crystal and Molecular Structure of the Halogeno-Bridged Dimers of Halogenobis(pentacarbonylrhenium)indium(III), [(Re(CO)₅)₂In(μ-X)]₂ (X = Cl, Br, I) [(Re(CO)₅)₂In(μ-X)]₂ crystallizes if X = Cl and X = Br in the monoclinic system, space group P2₁/c (No. 14), with the lattice constants X = Cl: a = 10.540(6), b = 12.961(7), c = 26.071(12) Å, β = 106.3(1) Å, Z = 4, X = Br: a = 10.548(9), b = 13.108(7), c = 26.192(15) Å, β = 106.0(2)°, Z = 4 and if X = I in the triclinic system, space group P1 (No. 2), with the lattice constants a = 10.739(2), b = 7.160(1), c = 13.647(1) Å, α = 68.65(9), β = 71.89(9), γ = 65.52(9)°, Z = 1. The central molecular fragment consists of a plane In₂X₂ ring with the mean In—X distances: X = Cl: 2.624(6) Å, X = Br: 2.764(3) Å and X = I: 2.986(2) Å and the angles In—X—In/X—In—X, X = Cl: 97.2(2)°/ 82.8(2)°, X = Br: 94.8(1)°/85.2(1)° and X = I: 96.47(5)°/83.53(5)°. Two Re(CO)₅ groups are bonded to each of these In atoms to form a distorted tetrahedral coordination. The mean In—Re bond-distances are: X = Cl: 2.797(2), X = Br: 2.796(2) and X = I:2.811 (2) Å. There is a octahedral coordination around the Re atoms.     

Structure and Conformational Stability of 1,3-Dihalo-2,2,4,4-tetrachloro-1λ3,3λ3-diphosphetidines

The optimal geometry of isomeric molecules of (XP-CCl₂)₂ with X = F, Cl, Br was determined by RHF/6-31G(d) calculations. With X = F and Cl, the electronic correlation was considered on the MP2/6-31G(d) level. The P₂C₂ ring is nonplanar. With X = Cl and Br, the trans conformation is energetically preferable compared to the two possible cis conformations: by 7.8 and 14.2 kJ mol^{- 1} for X = Cl and by 7.5 and 14.1 kJ mol^{- 1} with X = Br. respectively. With X = F, the calculated energies of the cis and trans forms are very close.     

Elektrochemische synthesen: XXII. Die kathodische reduktion von pentacarbonyl-chrom-halogenphosphanen

The cathodic reduction of the trihalophosphane complexes (CO)₅CrPX₃ (1a, X = Cl; 1b, X = Br) leads to the binuclear complexes (CO)₅ Cr(X₂PPX₂)Cr(CO)₅, (2a, X = Cl; 2b, X = Br). Reductive dehalogenation of coordinated organodihalophosphanes, (CO)₅CrPRX₂ (3a, R = Me, X = Cl; 3b, R = Ph, X = Cl; 3c, R = Me, X = Br; 3d, R = Ph, X = Br), in the presence of dimethyldisulfane yields bis(methylthio)organophosphane complexes, (CO)₅CrPR(SCH₃)₂ (5a, R = Me; 5b, R = Ph). The phosphinidene complexes (CO)₅ CrPR are discussed as the reactive intermediates.The organodibromophosphane complexes 3c and 3d can also be partially reduced in the presence of dimethyldisulfane, and (CO)₅CrPBrR(SCH₃) (7a, R = Me; 7b, R = Ph) is obtained. Radical intermediates are probable.     

Reaction of polyfluoroarenesulfonyl bromides with allyl bromide. Synthesis of allyl polyfluoroaryl sulfones

Reactions of polyfluoroarenesulfonyl bromides 4-XC₆F₄SO₂Br (X = F, H, Cl, Br, CF₃) with allyl bromide gave 84–94% of the corresponding allyl polyfluoroaryl sulfones.     

Halogenation of Pyrazoles Using N‐Halosuccinimides in CCl4 and in Water

Reaction of pyrazoles with N‐halosuccinimides (NXS, X=Br, Cl) in either CCl₄ or water gave 4‐halopyrazoles in excellent yields. The reaction was carried out under mild conditions and did not require any catalysts or special precautions. The reaction provides an efficient method for 4‐C halogenation of pyrazoles.     

Darstellung,Kristallstrukturen, Schwingungsspektren und Normalkoordinatenanalysen von trans-(PNP)[TcCl4(Py)2] und trans-(PNP)[TcBr4(Py)2]

Preparation, Crystal Structures, Vibrational Spectra, and Normal Coordinate Analysis of trans-(PNP)[TcCl₄(Py)₂] and trans-(PNP)[TcBr₄(Py)₂] By reaction of (PNP)₂[TcX₆] with pyridine in the presence of [BH₄]^? (PNP)[TcX₄(Py)₂], X = Cl, Br, are formed. X-ray structure determinations on single crystals of these isotypic Tc^III complexes (monoclinic, space group P2₁/n, Z = 2, for X = Cl: a = 13.676(4), b = 9.102(3), c = 17.144(2) Å, β = 91.159(1)°; for X = Br: a = 13.972(2), b = 9.146(3), c = 17.285(4) Å, β = 90.789(2)°) result in the averaged bond distances Tc? Cl: 2.386, Tc? Br: 2.519, Tc? N: 2.132(3) (X = Cl) and 2.143(4) Å (X = Br). The two pyridine rings are coplanar and vertical to the X? Tc? X-axes, forming angles of 42.28° (X = Cl) and 43.11° (X = Br). Using the molecular parameters of the X-ray structure determination and assuming D_2h point symmetry, the IR and Raman spectra are assigned by normal coordinate analysis based on a modified valence force field. Good agreement between observed and calculated frequencies is obtained with the valence force constants f_d(TcCl) = 1.45, f_d(TcBr) = 1.035, f_d(TcN) = 1.37 (X = Cl) and 1.45 mdyn/ Å (X = Br), respectively.     

Stereoselective ring-opening reactions with AcBr and AcCl. A new method for preparation of some haloconduritols

The actions of AcX (X=Br, Cl) on 7-oxa-bicyclo[2.2.1]hept-5-ene-2,3-diol diacetates and a transoid-epoxide prepared from the acetonide of cyclohexa-3,5-diene-cis-1,2-diol were studied. H₂SO₄-catalyzed cleavage of exo-cis-7-oxa-bicyclo[2.2.1]hept-5-ene-2,3-diol diacetate with AcCl gave (1α,2α,3α,6β)-6-chloro-4-cyclohexene-1,2,3-triol triacetate, from which the corresponding chloroconduritol was obtained by trans-esterification (MeOH/HCl). A similar reaction of the exo-diacetate with AcBr in the presence of H₂SO₄ resulted in bromine addition. The formation of bromine from the reaction of AcBr and H₂SO₄ was observed by independent experiments. H₂SO₄-catalyzed reaction of endo-cis-7-oxa-bicyclo[2.2.1]hept-5-ene-2,3-diol diacetate with AcX (X=Br, Cl) gave (1α,2α,3β,6β)-6-halo-4-cyclohexene-1,2,3-triol triacetates. The reaction of the transoid-epoxide with AcX (X=Br, Cl) with no catalyst gave also (1α,2α,3β,6β)-6-halo-4-cyclohexene-1,2,3-triol triacetates.     

α,ω-Bis(4-substituted-3-quinolinylthio)alkanes from reactions of thioquinanthrene with alkoxides

The reaction of thioquinanthrene 1 with sodium alkoxides and α,ω-dihaloalkanes leads to the formation of α,ω-bis[4-(4-methoxy-3-quinolinylthio)-3-quinolinylthio]alkanes 4 . The yield depends on the nature of α,ω-dihalo-alkanes. The effect of α,ω-dihaloalkanes of the following types: XCH₂X (X = Cl,Br,I), X(CH₂)₂X (X = Cl,Br,I), Br(CH₂)₃Br and Br(CH₂)₆Br were studied. The preparation of 4-alkoxy-3′-(ω-bromoalkylthio)-3,4′-diquinolinyl sulfide 3 and their transformation to α,ω-bis(4-alkoxy-3-quinolinylthio)alkanes 6 were studied as well.     

Organomercury compounds : XXVI. Thermal decomposition of mercuric 2,6-disubstituted benzoates

The main thermal decomposition path for mercuric 2,6-disubstituted benzoates, (RCO₂)₂Hg (R = 2,6-X₂C₆H₃; X = F, Cl, Br, or Me), can be varied considerably. In boiling dimethyl sulphoxide, decarboxylation occurs giving the corresponding diarylmercurial (X = F or Cl) or RHgO₂CR derivative (X = Me or Br). There is considerable competition from reaction of the mercuric salt with the solvent in the last three cases. With boiling pyridine as medium, the 2,6-difluorobenzoate yields a mixture of R₂Hg and RHgO₂CR derivatives, but the 2,6-dichlorobenzoate only gives (RCO₂)₂Hg(py)₂. Thermal decomposition of the mercuric benzoates under vacuum yields the carboxylic acids and complex mercuration products, mainly based on 3-mercurated 2,6-disubstituted benzoates, with partial additional mercuration and/or decarboxylation. Pyrolysis of mercuric 2,6-dichlorobenzoate at atmospheric pressure results in both mercuration and decarboxylation, giving m-dichlorobenzene as the main volatile product and a complex mercurial with 1,3-dimercurated-2,6-dichlorobenzene repeating units and 2,6-dichlorophenyl terminal groups.     

(N,N, N′, N′-tetramethylethylenediammonium)Cu2X6 (X=Cl,Br): crystal structure and magnetic interactions

Summary The crystal structures of (Me₄enH₂)Cu₂Cl₆ and (Me₄enH₂)Cu₂Br₆ have been determined. The triclinic crystals contain chains of symmetrically bibridged [Cu₂X₆]^2– dimers. Within the dimers the Cu–X distances average 2.299 Å (Cl) and 2.408 Å (Br) and the Cu–X–Cu angles are 96.4(1)^o (Cl) and 95.7(1)^o (Br). Longer Cu–X bonds, 2.679(1)Å (Cl) and 2.761(3)Å (Br), link dimers together into infinite chains via asymmetrical bridges. The bridging angles for the asymmetric bridge are 92.2(1)^o (Cl) and 89.4(1)^o (Br). Magnetic susceptibility data for both compounds are indicative of antiferromagnetic coupling. Analyses of the data yields J/k=–23(1)K (Cl) and –82(2)K (Br) for the interdimer coupling and J/k=–5(1)K (Cl) and –4(1)K (Br). The intradimer coupling for the chloride is in accord with magneto-structure relations deduced for similar salts. Similarly, the increased antiferromagnetic contribution upon substitution of Cl by Br follows trends previously observed.