The reaction of SF5Br with select 1,2-dihaloethylenes

SF₅Br reacts with 1,2-haloethylenes (F, Cl, Br) in distinct ways. In the case of F- and Cl-olefins, the expected addition occurs while with 1,2-dibromoethylene a metathetical reaction yielding in a clean reaction a 1:1 mixture of SF₅CHCHBr and CHBr₂CHBr₂ is found. The mechanism for this reaction is discussed.     

Thermal gas-phase reaction of perfluorobuta-1,3-diene with NO2

The reaction of NO₂ with perfluorobuta-1,3-diene, CF₂CFCFCF₂ (C₄F₆), has been studied at 312.9, 323.0, 333.4, 396.0 and 418.0 K, using a conventional static system. The products formed in the temperature range 312.9-333.4 K were CF₂CFCF(NO₂)CF₂(NO₂) (I), CF₂(NO₂)CFCFCF₂(NO₂) (II), CF₂CFCF(NO₂)C(O)F (III) and CF₂(NO₂)CFCFC(O)F (IV) and FNO. The formation of these compounds was detected performing infrared and Raman spectra. The infrared spectrum shows a band at 1785 cm⁻¹, characteristic to the terminal -CFCF₂ group and the Raman spectrum shows a band located at 1733 cm⁻¹, corresponding to -CFCF- group. It indicates, that in this temperature range, NO₂ attacks initially only one double bound of CF₂CFCFCF₂. Since the intermediate radical CF₂CFCFCF₂(NO₂) formed in this process is allylic in nature, so there is no isomerization involved in this process, but rather the allylic radical is able to add the second NO₂ either to CF₂ or CFCF₂(NO₂) end, forming the corresponding products. At 396.0 and 418.0 K different products were observed: CF₂(NO₂)CF(NO₂)C(O)F (V), NO, CF₃C(O)F, C(O)F₂ and traces of epoxide of tetrafluoroethene, showing that, at these temperatures, both double bonds are attacked by NO₂ and detachment of CF₂ group is produced. The mechanisms consistent with experimental results in the temperature range 312.9-333.4 and at 396.0 and 418 K are proposed.     

Monophosphine and diphosphine ligands for diplatinum polyynediyl complexes: Efficient syntheses of new functionality-containing systems and model compounds

Br(CH₂)₄Br and NaO(CH₂)₂CHCH₂ react under suitable conditions to give Br(CH₂)₄O(CH₂)₂CHCH₂ (55%), which is treated with KPPh₂ to yield the ether-containing phosphine Ph₂P(CH₂)₄O(CH₂)₂CHCH₂ (83%). The reaction of CH₃CH₂OC(O)CHC(CH₃)₂ and BrMg(CH₂)₃CHCH₂ in the presence of CuCl (cat.) and ClSiMe₃ yields CH₃CH₂OC(O)CH₂C(CH₃)₂(CH₂)₃CHCH₂ (67%), which is reduced to an alcohol that is brominated, reacted with Grubbs’ catalyst, hydrogenated, and treated with KPPh₂ to give the bis(geminally dimethylated) diphosphine Ph₂P(CH₂)₂C(CH₃)₂(CH₂)₈C(CH₃)₂(CH₂)₂PPh₂ (47% overall). The photochemical reaction of I(CF₂)₈I and H₂CCHCH₂SnBu₃ yields H₂CCHCH₂(CF₂)₈CH₂CHCH₂ (52%), which is converted with 9-BBN to a diol (92%) that is brominated and treated with LiPR₂ to give the fluorinated diphosphines R₂P(CH₂)₃(CF₂)₈(CH₂)₃PR₂ (R = a, p-tol, 67%; b, t-Bu, 69%; c, o-tol, 86%). Reactions of Br(CH₂)_mBr and LiPR₂ similarly yield R₂P(CH₂)_mPR₂ (m/R = 8/a, 95%; 14/a, 96%; 14/p-C₆H₄-t-Bu, 98%). Reactions of KPPh₂ with Br(CH₂)_m′CHCH₂and Br(CH₂)₇CH₃ give the corresponding monophosphines Ph₂P(CH₂)_m′CHCH₂ (m′ = 7, 82%; 10, 84%) and Ph₂P(CH₂)₇CH₃ (85%). When the former is combined with [Pt(μ-Cl)(C₆F₅)(tht)]₂ (tht = tetrahydrothiophene), trans-(C₆F₅)(Ph₂P(CH₂)_m′CHCH₂)₂PtCl (77-70%) is isolated. When the latter (excess) is combined with trans,trans-(C₆F₅)(p-tol₃P)₂Pt(CC)₄Pt(Pp-tol₃)₂(C₆F₅) (RT, 65 °C), trans,trans-(C₆F₅)(Ph₂P(CH₂)₇CH₃)₂Pt(C C)₄Pt(Ph₂P(CH₂)₇CH₃)₂(C₆F₅) (53%) is isolated.     

Functionalized fluoroalkyl and alkenyl silanes: Preparations, reactions, and synthetic applications

Preparations, reactions, and synthetic applications of functionalized fluoroalkyl and alkenyl silanes have been summarized. This review focuses mainly on the chemistries of (1) 1-substituted difluoromethylsilanes (XCF₂SiR₃), (2) 1-substituted 2,2-difluorovinylsilanes (CF₂CXSiR₃), (3) trifluoroisopropenyl, trifluoroacetimidoyl, and trifluoroacetyl silanes [CF₃C(SiR₃)X, XCH₂, NAr, O] and (4) other fluorinated alicyclic silanes.     

Triosmium compounds containing the oxametallacycle [Os(CO)3{C(R)CHC(O)CHC(H)C5H4FeC5H5}] moiety. Synthesis and electrochemical studies

The compounds [Os₃(CO)₁₀{μ,η³-(SCH₂CH₂SCCHC(O)CHCH(C₅H₄)Fe (C₅H₅)}] (2), [Os₃(CO)₉{μ,η³-(SCH₂CH₂SCCHC(O)CHCH(C₅H₄)Fe(C₅H₅)}] (3) and [Os₃(CO)₈{μ₃,η²-{CCHC(O)CHCH(C₅H₄)Fe(C₅H₅)}(SCH₂CH₂S)}] (4) have been obtained by rupture of S-C bonds in the ketene dithioacetal [C₅H₅FeC₅H₄CHCHC(O)CHC(SCH₂CH₂S)], in their reaction with the activated cluster [Os₃(CO)₁₀(NCMe)₂]. The presence of an oxametallacycle in these derivatives has been confirmed by an X-ray diffraction analysis. The electrochemical study has indicated the ability of these compounds to modify the electrode surfaces.     

Intermolecular hydrogen bonding in the binary mixture [(C2H5)2CO + CH3OH] probed by polarized Raman measurements and DFT calculations

The Raman spectra of neat (C₂H₅)₂CO (pentanone) and its binary mixtures with hydrogen donor solvent (CH₃OH), [(C₂H₅)₂CO + CH₃OH] having different mole fractions of the reference system, (C₂H₅)₂CO in the range 0.1-0.9 at a regular interval of 0.1 were recorded in the CO stretching region. In neat liquid, the Raman peak appears asymmetric. The asymmetric nature of the peak has been attributed to the CO stretching mode of the two conformers of (C₂H₅)₂CO having C₂ and C_2v point groups and the corresponding bands at ∼1711 and ∼1718 cm⁻¹, respectively. A careful analysis of the I_iso (isotropic component of the Raman scattered intensity) at different concentrations reveals that upon dilution with methanol, at mole fraction C = 0.6, an additional peak in the CO stretching region is observed at ∼1703 cm⁻¹ which is attributed to the hydrogen bonding with methanol. A peculiar feature in this study is that upon dilution, the peak at ∼1718 cm⁻¹ shows a minimum at C = 0.6, but on further dilution it shows a blue shift. However, the other peak at ∼1711 cm⁻¹ shows a continuous red shift with dilution as well as a maximum at C = 0.7 in the linewidth vs. concentration plot, which is essentially due to competition between motional narrowing and diffusion phenomena. A significant amount of narrowing in the Raman band at ∼1718 cm⁻¹ can be understood in terms of caging effect of the reference molecule by the solvent molecules at high dilution. A density functional theoretic (DFT) calculation on optimized geometries and vibrational frequencies of two conformers of neat (C₂H₅)₂CO in C₂ ad C_2v forms and the complexes with one and two CH₃OH molecules with both the conformers was performed. The experimental results and theoretical calculations together indicate a co-existence of two conformers as well as hydrogen bonded complex with methanol in the binary mixture, [(C₂H₅)₂CO + CH₃OH] at intermediate concentrations.     

The addition of (CF3SO2)2CHBr to vinylidene fluoride

It has been found that a mixture of (CF₃SO₂)₂CH₂ and (CF₃SO₂)₂CBr₂ can be used instead of (CF₃SO₂)₂CHBr in the radical addition to H₂CCF₂; the 1:1 and 1:2 adducts have been isolated and characterized. An improved synthesis of (CF₃SO₂)₂CBr₂ is also reported.     

Crystal structures of amarine and isoamarine and copper(I) coordination chemistry with their allylation products

The crystal structures of amarine (1) and isoamarine (2), important intermediates in the preparation of 1,2-diphenyl-diaminoethane, were successfully determined. Their allylation products, 1,3-diallyl amarine (1)(CH₂CHCH₂)₂Br (3) and isoamarine bromide (2)(CH₂CHCH₂)₂Br (4) [the crystal structures of (1)(CH₂CHCH₂)₂PF₆(3-Br + PF₆) and (2)(CH₂CHCH₂)₂PF₆ (4-Br + PF₆) are also successfully determined to confirm allylation products], react with CuBr to afford (1)₂(CH₂CHCH₂)₄(Cu₂Br₄) (5) and (2)(CH₂CHCH₂)₂(Cu₂Br₃) (6), respectively. Crystal structures of 5 and 6 reveal that 5 is an anion discrete complex without olefin moiety coordination, and 6 has a 1D infinite chain with olefin moiety coordination as a bridging spacer. The fluorescent emission spectra of 5 (λ_emax = 570 nm) and 6 (λ_emax = 642 nm) were measured, and display a significant difference that can be used for solid state fluorescent sensing them.     

Room temperature preparation of α-chloro-β,β-difluoroethenylzinc reagent (CF2CClZnCl) by the metallation of HCFC-133a (CF3CH2Cl) and a high yield one-pot synthesis of α-chloro-β,β-difluorostyrenes

α-Chloro-β,β-difluorovinylzinc reagent [CF₂CClZnCl] was generated in 91% yield by the metallation of a THF solution of commercially available HCFC-133a (CF₃CH₂Cl) and zinc chloride at 15-20 °C using LDA as base. The corresponding reaction with Halothane™ (CF₃CHClBr) produced a poor yield of CF₂CClZnCl. The palladium catalyzed coupling reaction of the CF₂CClZnCl with aryl iodides under mild reaction conditions produced α-chloro-β,β-difluorostyrenes in 64-90% isolated yields. The stability of the intermediate CF₂CClLi and the nature of the zinc reagents are discussed.     

Differentiation of isomeric allylic alkenyl methyl ethers by Raman spectroscopy

The Raman spectra of several pairs of alkenyl methyl ethers of general structure R¹R²CCR⁵C(R³R⁴)OCH₃ and R¹R²C(OCH₃)C(R⁵)CR³R⁴ (R¹, R², R³, R⁴, R⁵ = H or C_nH_2n+1, n = 1-3) are reported and discussed, with a view to establishing whether Raman spectroscopy offers a viable means of distinguishing between these isomeric unsaturated species. Key bands associated with the ν(sp₂CH) and ν(CC) stretching modes are found to be particularly useful in this connection: R¹R²CCHCH₂OCH₃ and R¹R²C(OCH₃)CHCH₂ ethers (R¹, R² = CH₃, C₂H₅) are easily distinguished on this basis. Differentiation of their lower homologues, R¹CHCHCH₂OCH₃ and R¹CH(OCH₃)CHCH₂ (R¹ = CH₃, C₂H₅, C₃H₇), by similar means is also quite straightforward, even in cases where cis and trans isomers are possible. Pairs of isomeric ethers, such as CH₃CHC(CH₃)CH₂OCH₃ and CH₃CH(OCH₃)C(CH₃)CH₂, in which the structural differences are more subtle, may also be distinguished with care. Deductions based on bands ascribed to the stretching vibrations are usually confirmed by consideration of the signals associated with the corresponding δ(sp₂CH) deformation vibrations. Even C₂H₅CHCHCH(C₃H₇)OCH₃ and C₃H₇CHCHCH(C₂H₅)OCH₃ are found to have distinctive Raman spectra, but differentiation of these closely related isomers requires additional consideration of the low wavenumber region.     

A well feasible and general route to (organoethynyl)difluoroboranes, RHCCBF2, and their perfluorinated analogues, RFCCBF2

A representative series of (organoethynyl)difluoroboranes RCCBF₂ (RC₄H₉, (CH₃)₃C, CF₃, C₃F₇, (CF₃)₂CF, CF₃CFCF, C₄F₉CFCF, C₆F₅) was prepared by abstraction of fluoride from the corresponding K[RCCBF₃] salts with BF₃ in appropriate solvents (1,1,1,3,3-pentafluoropropane, 1,1,1,3,3-pentafluorobutane, or dichloromethane).     

Tetrafluoroethylene telomerization using dibromohaloethanes as telogens

Carrier mediated telomerization (CMT) between C₂F₄ and bromochlorofluoroethanes has been evaluated in terms of product distributions arising from CMT and ‘normal’ telomerization. The effect of parameters like type of initiator and telogen, TFE pressure and temperature on the reaction has been studied. The peroxide initiated telomerization between dibromohaloethanes and C₂F₄ offers an easy synthetic route to α,ω-dibromo perfluoroalkanes Br(CF₂)_nBr with n = 2, 4, 6 and 8. The selectivity of the CMT products versus those from “normal” telomerization depends mainly on the choice of telogen and on its ability to act as ‘bromine donor’ in the radical telomerization. These perfluoroalkyl dibromides are useful intermediates for other derivatives, for example, perfluorinated mono- and diolefins, Br(CF₂)_nCHCH₂ and CH₂CH(CF₂)_nCHCH₂.     

From alkenylphosphane aminoallenylidene ruthenium(II) complexes to highly unsaturated ruthenaphosphabicycloheptene complexes

The alkenylaminoallenylidene complex [Ru(η⁵-C₉H₇){CCC(NEt₂)[C(Me)CPh₂]}{κ(P)-Ph₂PCH₂CHCH₂}(PPh₃)][PF₆] (2) has been prepared by the reaction of the allenylidene [Ru(η⁵-C₉H₇)(CCCPh₂){κ(P)-Ph₂PCH₂CHCH₂}(PPh₃)][PF₆] (1) with the ynamine MeCCNEt₂. The reaction proceeds regio- and stereoselectively, and the insertion of the ynamine takes place exclusively at the C_βC_γ bond of the unsaturated chain. The secondary allenylidene [Ru(η⁵-C₉H₇){CCC(H)[C(Me)CPh₂]}{κ(P)-Ph₂PCH₂CHCH₂}(PPh₃)][PF₆] (3) is obtained, in a one-pot synthesis, from the reaction of aminoallenylidene 2 with LiBHEt₃ and subsequent treatment with silica. Moreover, the addition of an excess of NaBH₄ to a solution of the complex 2 in THF at room temperature gives exclusively the alkynyl complex [Ru(η⁵-C₉H₇){CCCH₂[C(Me)CPh₂]}{κ(P)-Ph₂PCH₂CHCH₂}(PPh₃)] (5). The heating of a solution of allenylidene derivative 3 in THF at reflux gives regio- and diastereoselectively the cyclobutylidene complex [Ru(η⁵-C₉H₇) (PPh₃)][PF₆](4) through an intramolecular cycloaddition of the CC allyl and the C_αC_β bonds in the allenylidene complex 3. The structure of complex 4 has been determined by single crystal X-ray diffraction analysis.     

Nickel alkynyl and allenylidene complexes: Synthesis and properties

Copper-catalyzed reaction of [Cp(PPh₃)NiCl] with the terminal alkynes H-CC-C(O)R (R = O-Menthyl, NMe₂, Ph) yields the alkynyl complexes [Cp(PPh₃)Ni-CC-C(O)R]. Subsequent O-methylation with either [Me₃O]BF₄ or MeSO₃CF₃ affords cationic allenylidene complexes, [Cp(PPh₃)NiCCC(OMe)R]⁺X¯ (X = BF₄, SO₃CF₃). N-Alkylation of Cp(PPh₃)Ni-pyridylethynyl complexes likewise gives cationic allenylidene complexes. [Cp(PPh₃)Ni-CC-C(CH)₄N] adds BF₃ at nitrogen. Modification of the ligand sphere in these nickel allenylidene complexes is possible by replacing PPh₃ by PMe₃ in the alkynyl complex precursors. The first allenylidene(carbene)nickel cation, [Cp(SIMes)NCCC(OMe)NMe₂]⁺, is accessible by successive reaction of [Cp(SIMes)NiCl] with H-CC-C(O)NMe₂ and [Me₃O]BF₄. By the analogous sequence an allenylidene complex containing the chelating (diphenylphosphanyl)ethylcyclopentadienyl ligand can be prepared. DFT Calculations were carried out on the allenylidene complex cation [Cp(PPh₃)NiCCC(OMe)NMe₂]⁺ and on its precursor, the alkynyl complex [Cp(PPh₃)Ni-CC-C(O)NMe₂]. Based on the spectroscopic data and a X-ray structure analysis the bonding in the new nickel allenylidene complexes is best represented by several resonance forms, an alkynyl resonance form considerably contributing to the overall bond.     

Reactions of β-alkoxyvinyl trihalogenomethyl ketones with triethyl phosphite

The Perkow reaction of triethyl phosphite and β-alkoxyvinyl trihalogenomethyl ketones, which have common acyclic or cyclic structural fragment: -O-CC-C(O)CX₂Cl, yielded dienyl phosphates: -O-CC-C[OP(O)(OEt)₂]CX₂ where X = F or Cl, whereas γ-bromo-β-methoxy-α,β-unsaturated trifluoromethyl ketone CF₃C(O)CHC(OMe)CH₂Br gave diene CF₃C[OP(O)(OEt)₂]CH-C(OMe)CH₂.     

Reaction of trifluoromethylated β-alkoxyenones with tris(trimethylsilyl) phosphite: A temperature influence on regioselectivity

The interaction of tris(trimethylsilyl) phosphite (TMSO)₃P and E-trifluoromethyl-β-alkoxyenones CF₃C(O)CHCHOEt and CF₃C(O)CHC(OMe)Me yielded mixtures of E-1,2- and Z-1,4-adducts, CF₃C(OTMS)[P(O)(OTMS)₂]CCH(OAlk)R 2 and CF₃(OTMS)CCHCR(OAlk)[P(O)(OTMS)₂] 3 where R and Alk = H and Me, or both Me. Conversion of these 1,2-adducts to 1,4-isomers was effected by increased temperature or by exposure to more tris(trimethylsilyl) phosphite. Acid hydrolysis of 2b (R and Alk = Me) gave ketophosphonic acid CF₃C(OH)[P(O)(OH)₂]CH₂COMe in 88% yield, whereas hydrolysis of 2a (R = H and Alk = Et) with KOH in methanol gave CF₃C(OH)[P(O)(OK)₂]CHCHOEt in 37% yield. Acid hydrolysis of 3a (R = H and Alk = Et) and 3b (R and Alk = Me) gave phosphonic acid CF₃C(OH)₂CHCHP(O)(OH)₂ in 82% yield and trifluoromethylated 1,2λ⁵σ⁴-oxaphosphol-3-en.     

Synthesis and crystal structures of cyclodiazastannoxides fused cyclopentadienyl M-Sn (M = Mo, W) bonded organometallic heterocycle

The condensation reaction of CH₃COC₅H₄M(CO)₃SnCl₃ (M = Mo or W) with PyCONHNH₂ (Py = 2,3,4-pyridyl or 2-pyridylmethyl) in mild conditions yields cyclodiazastannoxides fused cyclopentadienyl M-Sn bonded organometallic heterocycle {μ-[C₅H₄(CH₃)CN-NC(O)PyH]M(CO)₃SnCl₃}. The similar reaction of CH₃COC₅H₄M(CO)₃SnCl₃ with ArCONHNH₂ (Ar = 2-furanyl) gives complexes μ-[C₅H₄(CH₃)CN-NC(O)Ar]M(CO)₃SnCl₂(H₂O), in which the water molecule can be replaced by other N-donor ligands, such as pyridine or 4,4-bipyridine. Arene-bridged organometallic heterocyclic complexes μ-{[C₅H₄(CH₃)CN-NC(O)]₂C₆H₄}{M(CO)₃SnCl₂(Solvent)}₂ have also been prepared by the reaction of CH₃COC₅H₄M(CO)₃SnCl₃ with terephthaloyl hydrazine. In these new organometallic heterocyclic complexes, it seems that the tin atom prefers to be six-coordinate through absorbing the chloridion or solvent molecules.     

Site directed synthesis of mono and disubstituted SF5-polyfluoroalkyl benzenes

A novel method for the preparation of o-, m-, p-SF₅CF₂CFYC₆H₄X (Y = Br, F and X = m-Br, p-Br, Cl, CH₃, CF₃, NO₂, o-NO₂, F, CF₃, CH(CH₃)₂) derivatives was devised by a two-step reaction: SF₅Br-addition to o-, m-, p-CF₂CFC₆H₄X followed by reaction of AgBF₄ with the o-, m-, p-SF₅CF₂CFBrC₆H₄X adducts. Additional studies have been carried out with several derivatives and includes the preparation of SF₅CF₂C(O)C₆H₅, p-CF₃CFBrC₆H₄NO₂, SF₅CF₂CF₂C₆H₃(NO₂)₂, SF₅CF₂CF₂C₆H₃(NH₂)₂, and an SF₅CF₂CF₂-containing polyimide and dye. The complete characterization (IR, NMR, and MS) of these compounds is given.