Original fluorinated surfactants potentially non-bioaccumulable

This minireview updates non-exhaustive recent strategies of synthesis of original fluorosurfactants potentially non-bioaccumulable. Various strategies have been focused on (i) the preparation of CF₃–X–(CH₂)_n–SO₃Na (with X = O, C₆H₄O or N(CF₃) and n = 8–12), (ii) the oligomerization of hexafluoropropylene oxide (HFPO) to further synthesize oligo(HFPO)–CF(CF₃)CO–R_H (where R_H stands for an hydrophilic chain); (iii) the telomerization of vinylidene fluoride (VDF) with 1-iodopentafluoroethane or 1-iodononafluorobutane to produce C_nF_2n+1–(VDF)₂–CH₂CO₂R (n = 2 or 4, R = H or NH₄), (iv) the radical telomerization of 3,3,3-trifluoropropene (TFP) with isoperfluoropropyliodide or diethyl hydrogenophosphonate to prepare (CF₃)₂CF(TFP)_x–R_H or CF₃–CH₂–CH₂–(TFP)_y–P(O)(OH)₂, and (v) the radical cotelomerization of VDF and TFP, or their controlled radical copolymerization in the presence of (CF₃)₂CFI or a fluorinated xanthate. In most cases, the surface tensions versus the surfactant concentrations have been assessed. These above strategies led to various highly fluorinated (but yet not perfluorinated) telomers whose chemical changes enabled to obtain original surfactants as novel alternatives to perfluorooctanoic acid (PFOA), ammonium perfluorooctanoate (APFO), or perfluorooctylsulfonic acid (PFOS) regarded as bioaccumulable, persistent, and toxic.     

Studies on sulfinatodehalogenation: XVII. The sulfinatodehalogenation of primary perfluoroalkyl iodides and bromides by Rongalite

Using acetonitrile or DMF as cosolvent, both perfluoroalkyl iodides such as Cl(CF₂)_nI (n = 4,6,8, la—lc ), CF₃ (CF₂)_n I (n = 5,6,7, ld—lf ), I (CF₂)_n O (CF₂) SO₃ Na(n = 2,4,6, lg—li ) and perfluoroalkyl bromides such as Cl (CF₂)_n Br (n = 4,6, 3a—3b ) and C₇F₁₅ Br (3e) reacted with Rongalite in aqueous solution to give the corresponding sulfinates Cl (CF₂)_n SO₂ Na (n = 4,6,8, 2a—2c ), CF₃-(CF₂)_nSO₂Na (n = 5,6,7, 2d—2f ) and NaO₂S(CF₂)_nO(CF₂)₂SO₃Na (n = 2,4,6, 2g—2i ) in moderate yields. 1 H-perfluoroalkanes were formed as the main products when other solvents such as ethanol. iso-propanol, 1,4-dioxane and morpholine were used.     

Studies on sulfinatodehalogenation: IV. The sulfinatodebromination of primary perfluoroalkyl bromides and perfluoroalkylene α, ω-dibromides

Using PTC or cosolvent, both perfluoroalkyl bromides such as Br (CF₂)₂O(CF₂)₂SO₂Na ( 1 ), Br(CF₂)₂OCF₂CO₂H ( 2 ), Cl(CF₂)₄Br ( 3 ), Cl(CF₂Br ( 4 ), n-C₆F₁₃Br ( 5 ), n-C₈F₁₇Br ( 6 ), H(CF₂)₈Br ( 7 ), α, ω-dibromides O(CF₂CF₂Br)₂ ( 8 ), Br(CF₂)₆Br ( 9 ) and Br(CF₂)₈Br ( 10 ) reacted readily with Na₂S₂O₄ in the presence of NaHCO₃ in aqueous solution to form the corresponding perfluoroalkane sulfinates NaO₂S(CF₂)₂O(CF₂)₂SO₂Na ( 11 ), NaO₂S(CF₂)₂OCF₂CO₂Na ( 12 ), Cl(CF₂)₄SO₂Na ( 13 ), Cl(CF₂)₂SO₂Na ( 14 ), n-C₃F₁₃SO₂Na ( 15 ), n-C₈F₁₇SO₂Na ( 16 ), H(CF₂)₈SO₂Na ( 17 ), α, ω-disulfinates O(CF₂CF₂SO₂Na)₂ ( 18 ), NaO₂S(CF₂)₄SO₂Na ( 19 ) and NaO₂S(CF₂)₈SO₂Na ( 20 ) in 66—97% yields. To this new and general reaction of perfluoroalkyl bromides, the name sulfinatodebromination is proposed.     

Studies on sulfinatodehalogenation: III. The sulfinatodeiodination of primary perfluoroalkyl iodides and α,ω-perfluoroalkylene diiodides by sodium dithionite

Using P. T. C. or cosolvents, both perfluoroalkyl iodides such as Cl(CF₂),_nI (n=2, 4, 6, 1a-1c), H(CF₂)₈I (1d), CF₃(CF₂)_nI (n=3, 5, 7, 1e-1g), and α. ω-perfluoroalkylene diiodides such as (ICF₂CF₂)₂O (4a), I (CF₂)_nI (n=6, 8, 10, 4b-4d) reacted smoothly with sodium dithionite in aqueous solution under mild conditions to give the corresponding perfluoroalkanesulfinates Cl(CF₂)_nSO₂Na (n=2, 4, 6, 2a-2c), H(CF₂)₈SO₂Na (2d), CF₃(CF₂)nSO₂Na (n=3, 5, 7, 2e-2g), α, ω-perfluoroalky-lenedisulfinates O (CF₂CF₂SO₂K)₂ (5a), and KO₂S(CF₂)_nSO₃K (n=6, 8, 10, 6b-6d) in moderate to high yields. These sulfinates were converted to the corresponding sulfonyl chlorides by reacting with chlorine in the usual way. Thus the discovery of the new reagent renders sulfinatodeiodination a practical method for the synthesis of perfluorosulfinic and perfluorosulfonic acids and their derivatives from the corresponding perfluoroalkyl iodides.     

The reactions of perfluoro- and α,α-dichloropolyfluoroalkanesulfinates

Sodium perfluoroalkanesulfinate, R_FSO₂Na [R_F?Cl(CF₂)₄, 1a; CF₃(CF₂)₅, 1b; Cl(CF₃)₆, 1c] reacted with bromine in aqueous solution to give the corresponding sulfonyl bromide R_FSO₂Br (2a-2c) and in acetonitrile or acetic acid, to form perfluoroalkyl bromide R_FBr (3a-3c). Heating in acetonitrile at 80°C, 2a-2c were converted smoothly into 3a-3c. However, reaction of sodium α,α-dichloropolyfluoroalkanesulfinate RCCl₂SO₂Na (R?CF₃, Cl(CF₂)n, n=2, 4, 6, 5a-5d) with bromine in aqueous solution gave directly the corresponding bromoalkanes 1-bromo-1,1-dichloropolyfluoroalkane RCCl₂Br (6a-6d). In aqueous potassium iodide solution, 1a-1c, 5a and 5b also reacted with iodine to form the corresponding iodo-polyfluoroalkane 4a-4c, 7a and 7b directly. 6a and 7a underwent free radical addition to alkene readily in the presence of free radical initiator and reacted with Na₂S₂O₄ in the usual way to form α,α-dichloropolyfluoroethane sulfinate (5a). 5a was stable in strong acid, but reacted with strong base to yield 10. 5a was oxidised by hydrogen peroxide to the sulfonate 11 and reduced by zinc in dilute acid to from the α-chloro sulfinate 12.     

The syntheses of fluorinated alkanesulfonamides and poly-(fluorinated alkanesulfonamides)

In order to synthesize poly-(fluorinated alkanesulfonamides) a series of model experiments were carried out: (1) reactions of fluorinated alkanesulfonyl fluorides with amines, (2) reactions of fluorinated alkanesulfonyl chloride with amines and (3) reactions of sodium salts of fluorinated alkanesulfonamides with alkyl iodides of fluorinated alkanesulfonic acid esters. Seventeen new fluorinated alkanesulfonamides were prepared in good yields, namely: R_FO(CF₂)₂SO₂NR¹R² (1a-h), R¹R²NSO₂R_FSO₂NR¹R² (2a-h) and [Cl (CF₂)₄O(CF₂)₂SO₂NH(CH₂)₃]₂ (3). Reaction of R_FSO₂NH₂ with equivalent amount of NaOCH₃ and methyl iodide was shown to give both the N-mono- and N,N-di-substituted amides. Consequently the N-monosubstituted alkanesulfonamides were chosen as monomers for syntheses of the poly-(fluorinated alkanesulfonamides) and two new polymers were synthesized. The effect of the condition of the polycondensation on M?_n of the polymers were discussed and elemental composition, ¹⁹F NMR, IR, M?_n, Tg, tensile strength, thermal and chemical stabilities of the polymers were measured. Several new perfluoroalkanesulfonyl chlorides CISO₂R_FSO₂Cl (4a-c) and fluorinated alkanesulfonic acid esters (6a-d) were synthesized. However, reaction of CFCl₂CF₂O(CF₂)₂SO₂F with AlCl₃ was found to give Cl₃CCF₂O(CF₂)₂SO₂F (5) instead of the expected sulfonyl chloride.     

Perfluoro- ω -iodo-3-oxaalkanesulfonyl fluorides as intermediates for surfactants and vinyl compounds

The well known fluorosulfonyldifluoroacetyl fluoride (I), FOCCF₂SO₂F (I) quantitatively formed from sulfur trioxide and TFE through the tetrafluoroethanesultone has been converted into the octafluoro- -5-iodo-3-oxapentanesulfonyl fluoride (II) ICF₂CF₂OCF₂CF₂SO₂F (II) by the well known reaction (1) involving MF, iodine, TFE in aprotic solvents.The iodo compound (II) allowed us to obtain TFE telomers having both fluorosulfonyl and iodo as terminal groups.The said telomers have been easily converted into surfactants (III) through fluorination and vinyl derivatives (IV) by dehalogenation.CF₃CF₂(CF₂CF₂)_nOCF₂CF₂SO₃M (III)CF₂CF(CF₂CF₂)_nOCF₂CF₂SO₂F (IV)     

The reaction of perfluoroalkanesulfinates: IV. Perfluoroalkyl radical addition to olefins initiated by single electron oxidation of perfluoroalkanesulfinate

Sodium perfluoroalkanesulfinates [Cl (CF₂)_n SO₂ Na (1), a , n = 4; b , n = 6; c , n = 8] with the reduction potentials about 0.95—1.00V could be oxidized readily with various oxidizing agents such as Mn (OAc)₃ 2H₂O, Ce (SO₄)₂, HgSO₄ and Co₂O₃ to generate perfluoroalkyl radicals which added to the olefins RCH ? CHR' to give two kinds of adducts, namely RCH (R_f) CHXR' (3, X ? H; 4, X ? OAc), with good yields depending upon the solvent system used. Different oxidizing agents showed slight variation on the yields of the adducts. The reaction time could be greatly shortened at higher temperature. Thus, this reaction provides a new way for introducing a perfluoroalkyl group into olefinic compounds.     

Perfluoroalkylation of aromatic compounds with perfluoroalkyl radical generated from the oxidation of sodium perfluoroalkanesulfinate

Sodium perfluoroalkanesulfinates [R_fSO₂Na(1), R_f = Cl (CF₂)_n; a, n = 4; b, n = 6; c, n = 8] on oxidation with various single electron oxidizing agents, such as Mn (OAc)₃ · 2H₂O and Ce (SO₄)₂, yielded perfluoroalkyl radicals capable of perfluoroalkylating aromatic compounds to give a mixture of o-and p-monoperfluoroalkylated products. Thus, this reaction provides a new method for the synthesis of o-and p-monoperfluoroalkyl substituted aromatic compounds.     

Chiral Fluorinated α‐Sulfonyl Carbanions: Enantioselective Synthesis and Electrophilic Capture,Racemization Dynamics,and Structure

Enantiomerically pure triflones R¹CH(R²)SO₂CF₃ have been synthesized starting from the corresponding chiral alcohols via thiols and trifluoromethylsulfanes. Key steps of the syntheses of the sulfanes are the photochemical trifluoromethylation of the thiols with CF₃Hal (Hal=halide) or substitution of alkoxyphosphinediamines with CF₃SSCF₃. The deprotonation of RCH(Me)SO₂CF₃ (R=CH₂Ph, iHex) with nBuLi with the formation of salts [RC(Me)? SO₂CF₃]Li and their electrophilic capture both occurred with high enantioselectivities. Displacement of the SO₂CF₃ group of (S)‐MeOCH₂C(Me)(CH₂Ph)SO₂CF₃ (95 % ee) by an ethyl group through the reaction with AlEt₃ gave alkane MeOCH₂C(Me)(CH₂Ph)Et of 96 % ee. Racemization of salts [R¹C(R²)SO₂CF₃]Li follows first‐order kinetics and is mainly an enthalpic process with small negative activation entropy as revealed by polarimetry and dynamic NMR (DNMR) spectroscopy. This is in accordance with a C_α? S bond rotation as the rate‐determining step. Lithium α‐(S)‐trifluoromethyl‐ and α‐(S)‐nonafluorobutylsulfonyl carbanion salts have a much higher racemization barrier than the corresponding α‐(S)‐tert‐butylsulfonyl carbanion salts. Whereas [PhCH₂C(Me)SO₂tBu]Li/DMPU (DMPU = dimethylpropylurea) has a half‐life of racemization at ?105 °C of 2.4 h, that of [PhCH₂C(Me)SO₂CF₃]Li at ?78 °C is 30 d. DNMR spectroscopy of amides (PhCH₂)₂NSO₂CF₃ and (PhCH₂)N(Ph)SO₂CF₃ gave N? S rotational barriers that seem to be distinctly higher than those of nonfluorinated sulfonamides. NMR spectroscopy of [PhCH₂C(Ph)SO₂R]M (M=Li, K, NBu₄; R=CF₃, tBu) shows for both salts a confinement of the negative charge mainly to the C_α atom and a significant benzylic stabilization that is weaker in the trifluoromethylsulfonyl carbanion. According to crystal structure analyses, the carbanions of salts {[PhCH₂C(Ph)SO₂CF₃]Li? L }₂ ( L =2 THF, tetramethylethylenediamine (TMEDA)) and [PhCH₂C(Ph)SO₂CF₃]NBu₄ have the typical chiral C_α? S conformation of α‐sulfonyl carbanions, planar C_α atoms, and short C_α? S bonds. Ab initio calculations of [MeC(Ph)SO₂tBu]^? and [MeC(Ph)SO₂CF₃]^? showed for the fluorinated carbanion stronger n_C→σ* and n_O→σ* interactions and a weaker benzylic stabilization. According to natural bond orbital (NBO) calculations of [R¹C(R²)SO₂R]^? (R=tBu, CF₃) the n_C→σ*_{S? R} interaction is much stronger for R=CF₃. Ab initio calculations gave for [MeC(Ph)SO₂tBu]Li ? 2 Me₂O an O,Li,C_α contact ion pair (CIP) and for [MeC(Ph)SO₂CF₃]Li ? 2 Me₂O an O,Li,O CIP. According to cryoscopy, [PhCH₂C(Ph)SO₂CF₃]Li, [iHexC(Me)SO₂CF₃]Li, and [PhCH₂C(Ph)SO₂CF₃]NBu₄ predominantly form monomers in tetrahydrofuran (THF) at ?108 °C. The NMR spectroscopic data of salts [R¹(R²)SO₂R³]Li (R³=tBu, CF₃) indicate that the dominating monomeric CIPs are devoid of C_α? Li bonds.     

Mechanistic insights into the reaction of CF3CCl3 with SO3: Theory and experiment

Reaction mechanism of 1,1,1-trifluorotrichloroethane (CF₃CCl₃) and sulphur trioxide (SO₃) in the presence of mercury salts (Hg₂SO₄ and HgSO₄) was studied applying the density functional theory (DFT) at the UB3LYP/6-31+G(d,p) level. It was found that this reaction occurs in the free radical chain path as follows: mercury(I) sulphate free radical is generated by heat, causing CF₃CCl₃ to produce the CF₃CCl₂ free radical which reacts with SO₃ leading to the formation of CF₃CCl₂OSO₂ decomposing into CF₃COCl and SO₂Cl. The SO₂Cl free radical triggers CF₃CCl₃ to regenerate CF₃CCl₂ which recycles the free radical growth reaction. This elementary reaction has the highest energy barrier and it is therefore the rate control step of the whole reaction path. Experiment data can confirm the existence of the mercury(I) salt free radical and the free radical initiation stage. So, mercury salts play the role of initiators not that of catalysts. The results agree well with our hypothesis.     

Studies on fluoroalkylation and fluoroalkoxylation: 8. Palladium(0)-catalyzed addition reaction of fluoroalkyl iodides with alkynes

Fluoroalkyl iodide R_fI [R_F=(CF₂)_nCl, n=2, 4, 6; CF₃(CF₂)_n, n=1, 3; H(CF₂)₄] reacted with alkyne (CH≡CC₄H₉; CH≡CSiMe₃; CH≡CC₆H₅) in the presence of catalytic amounts of tetrakis (triphenylphosphine) palladium (0) to give a mixture of E and Z-fluoroalkylated adduct. The reaction could not be catalyzed by dichloro-bis(triphenylphosphine)palladium (II) and fluoroalkyl complex of palladium (II). 2-Nitro-2-nitrosopropane partly suppressed the reaction. It is believed that the reaction proceeds through a free radical intermediate rather than fluoroalkyl complex of palladium (II).     

Acetalization and Transacetalization Reactions Catalyzed by Ruthenium,Rhodium, and Iridium Complexes with {2‐{{Bis[3‐(trifluoromethyl)phenyl]phosphino}methyl}‐2‐methylpropane‐ 1,3‐diyl}bis[bis[3‐(trifluoromethyl)phenyl]phosphine] (MeC[CH2P(m‐CF3C6H4)2]3)

The complexes [RhCl_(3−n)(MeCN)_n(CF₃triphos)](CF₃SO₃)_n (n=1, 2; CF₃triphos=MeC[CH₂P(m‐CF₃C₆H₄)₂]₃) and [M(MeCN)₃ (CF₃triphos)](CF₃SO₃)_n (M=Ru, n=2; M=Ir, n=3) are catalyst precursors for some typical acetalization and transacetalization reactions. The activity of these complexes is higher than those of the corresponding species containing the parent ligand MeC[CH₂P(C₆H₅)₂]₃(Htriphos). Also the complexes [MCl₃(tripod)] (tripod=Htriphos and CF₃triphos) are active catalysts for the above reactions. The complex [RhCl₂(MeCN)(CF₃triphos)](CF₃SO₃) catalyzes the acetalization of benzophenone.     

Kinetic studies of dicopper complexes in catechol oxidase model reaction by using an approximationless evaluating method

The oxidation of 3,5-di-tert-butylcatechol to 3,5-di-tert-butyl-o-benzoquinone catalyzed by dinuclear copper(II) complexes {[Cu₂(L¹)(CF₃SO₃)₂(H₂O)₄]-(CF₃SO₃)₂ (1) and [Cu₂(L²O)](CF₃SO₃)₂ (2)| has been investigated in methanol saturated with O₂ at ambient temperature. Detailed kinetic studies were carried out and for the treatment the fitting software ZiTa was applied. On the basis of the results in the kinetic studies a possible mechanism of the catalytic reaction is proposed.This revised version was published online in December 2005 with corrections to the Cover Date.     

Sodium dithionite initiated addition of CF2Br2, CF3I and (CF3)2CFI to allylaromatics: Synthesis and the reactivity of 4-aryl-1,1-difluorodienes and 4-aryl-1,1-bis(trifluoromethyl)dienes

Sodium dithionite initiated addition of CF₂Br₂, CF₃I and (CF₃)₂CFI to the terminal double bond of allylbenzenes and of (CF₃)₂CFI to allylpyridines in a MeCN/H₂O system were investigated. The reactions of CF₂Br₂ with allylbenzenes gave comparable amounts of adducts, 1-(2,4-dibromo-4,4-difluorobutyl)benzenes, debrominated products,1-(4-bromo-4,4-difluorobutyl)benzenes, and dimeric compounds in total yields 40-66%. Treatment of the adducts with DBU resulted in double dehydrohalogenation affording 4-aryl-1,1-difluorobutadienes which undergo Diels-Alder condensation with nitrogen dienophiles to give N-heterocycles with difluoromethylene group in the ring. The reactions of CF₃I and (CF₃)₂CFI with allylbenzenes gave the respective adducts, (4,4,4-trifluoro-2-iodobutyl)benzenes and 1-(4,5,5,5-tetrafluoro-4-(trifluoromethyl)-2-iodopentyl)benzenes as the main products. Dehydrohalogenation of these adducts resulted, respectively, in (4,4,4-trifluoro-but-1-enyl)benzenes and 4-aryl-1,1-bis(trifluoromethyl)butadienes in high yields. (CF₃)₂CFI reacted rapidly with allylpyridines to give mixtures from which, after treatment with DBU, 4-pyridyl-1,1-bis(trifluoromethyl)butadienes were isolated in a ca. 60% yield.     

Studies on fluoroalkylation and fluoroalkoxylation: 2. Perfluoroalkylation of aromatics with perfluoroalkyl iodides in the presence of copper

Perfluoroalkyl iodide R_fI [R_f = (CF₂)_nO(CF₂)₂SO₂F, n = 2, (a); n = 4, (b); (CF₂)₄Cl, (c)] reacted with substituted benzene C₆H₅Y (Y = alkyl, OCH₃, CF₃, F, Cl, Br, I) in the presence of copper in acetic anhydride to give the corresponding mixture of isomeric disubstituted benzene (R_fC₆H₄Y). The conversion and yield depend on both the amount of copper used and nature of substituent. The likely explanation is that the reaction may involve a free radical process. The perfluoroalkyl radical can be trapped by cyclohexene, isopropylbenzene and styrene. Using DMSO in place of acetic anhydride as a solvent the reaction takes a different course, it is believed that the reaction in DMSO proceeds through a perfluoroalkylcopper intermediate.     

Synthesis of nitrogen-containing drimane sesquiterpenoids from 11-dihomodrim-8(9)-en-12-one

Products from the reaction of 11-dihomodriman-8α-ol-12-one with several reagents such as MeSO₃SiMe₃, CF₃SO₃SiMe₃, Sc(CF₃SO₃)₃, conc. H₂SO₄ in EtOH (30% solution), and Amberlist-15 ion-exchange resin were studied. 11-Dihomodrim-8(9)-en-12-one and its oxime were synthesized. The reaction of its oxime with H₃PO₄ (86%) or CF₃CO₂H produced (1S,2S,4aS,8aS)-2,5,5,8a-tetramethyldecahydro-1H-naphtho [1,2-e]-3-methyl-4,5-dihydro-[1,2,6]-oxazine; with p-TsCl in Py, (1S,2S,4aS,8aS)-2,5,5,8a-tetramethyldecahydro-1H-naphtho[1,2-d]-2-methylpyrroline-N-oxide; and with PCl₅ in Et₂O, 11-acetylaminodrim-8(9)-ene and 11-methylaminooxodrim-8(9)-ene.     

Bi-functional fluoroalkylation reagents: an introduction to halo-substituted 3-oxa-perfluoroalkanesulfonyl fluorides

X(CF₂CF₂)_nOCF₂CF₂SO₂F (X=I, Br, Cl; n=1, 2, 3, 4) are widely used fluoroalkylation reagents, which can incorporate ‘heavy’ fluorous tags into organic compounds. X(CF₂CF₂)_nOCF₂CF₂SO₂F have both sulfonyl and halo groups. They behave as bi-functional fluoroalkylation reagents. The cleavage of the C–I bonds of I(CF₂CF₂)_nOCF₂CF₂SO₂F by reductants (such as Na₂S₂O₄, Zn), single electron transfer reagents and radical initiator systems (like Bz₂O₂, AIBN, and (t-BuO)₂, or under UV and heat) gives, respectively, the sulfinatodehalogenated products, the hydrodehalogenated products, the homo-coupling products and the perfluoroalkylated products (if alkenes, alkynes or arenes were added). The functionalization of the sulfonyl groups (SO₂F) of X(CF₂CF₂)_nOCF₂CF₂SO₂F by esterification, amidation, and fluorination affords the corresponding perfluoroalkanesulfonates, fluoroalkanesulfonamide, and perfluoroalkanes. In many cases, both the halo and sulfonyl groups of X(CF₂CF₂)_nOCF₂CF₂SO₂F are transformed. These transformations finally lead to hundreds of useful highly fluorinated materials, such as supper acids, catalysts, surfactants, ion-exchange resins, electrolytes, polymers, and dense ionic liquids. Furthermore, X(CF₂CF₂)_nOCF₂CF₂SO₂F have commendable advantages, such as the easy preparation, the wide range of substrate tolerance, the mild reaction condition, and the high yields of desired products, which make them very promising. This review briefly summarizes the synthesis, reactivity, and applications of these intriguing reagents.     

Metal–ligand Lability and Ligand Mobility Enables Framework Transformation via Ligand Release in a Family of Crystalline 2D Coordination Polymers

A family of seven silver(I)-perfluorocarboxylate-quinoxaline coordination polymers, [Ag₄(O₂CR_F)₄(quin)₄] 1 – 5 (R_F=(CF₂)_n-1CF₃)₄, n=1 to 5); [Ag₄(O₂C(CF₂)₂CO₂)₂(quin)₄] 6 ; [Ag₄(O₂CC₆F₅)₄(quin)₄] 7 (quin=quinoxaline), denoted by composition as 4 : 4 : 4 phases, was synthesised from reaction of the corresponding silver(I) perfluorocarboxylate with excess quinoxaline. Compounds 1 – 7 adopt a common 2D layered structure in which 1D silver-perfluorcarboxylate chains are crosslinked by ditopic quinoxaline ligands. Solid-state reaction upon heating, involving loss of one equivalent of quinoxaline, yielding new crystalline 4 : 4 : 3 phases [Ag₄(O₂C(CF₂)_n-1CF₃)₄(quin)₃]_n ( 8 – 10 , n=1 to 3), was followed in situ by PXRD and TGA studies. Crystal structures were confirmed by direct syntheses and structure determination. The solid-state reaction converting 4 : 4 : 4 to 4 : 4 : 3 phase materials involves cleavage and formation of Ag−N and Ag−O bonds to enable the structural rearrangement. One of the 4 : 4 : 3 phase coordination polymers ( 10 ) shows the remarkably high dielectric constant in the low electric field frequency range.     

Studies on the copolymerization of norbornene with CO catalyzed by a new catalytic system PdCl<Subscript>2</Subscript>/phen/M(CF<Subscript>3</Subscript>SO<Subscript>3</Subscript>)<Subscript>n</Subscript>

A new three-component catalytic system, PdCl₂/phen/M(CF₃SO₃)_n where M = La, Y, Yb, Zn, and Cu, was studied for the copolymerization of norbornene (NBE) with CO to prepare polyketone (PK). It was found that the CF₃SO₃H catalytic system gave a low catalytic activity for the copolymerization of norbornene with CO, but when M(CF₃SO₃)_n was introduced instead of CF₃SO₃H, the PdCl₂/phen/M(CF₃SO₃)_n catalytic system exhibited much higher activity. The effects of ligands, M(CF₃SO₃)_n, solvents, and temperatures on the copolymerization have been discussed in detail. The results showed that with 1,10-phenanthroline (phen) and Cu(CF₃SO₃)₂ used as cocatalysts, the corresponding reaction rate reached 82 000 g PK (mol Pd)⁻¹h⁻¹ when the reaction was carried out in methanol at 90°C and 3.0 MPa of CO, and the weight average molecular weight (M _w) of the resultant copolymer is 1090 g/mol. The copolymer was characterized with various techniques such as FT-IR, ¹HNMR, ¹³CNMR, TGA, and DSC. The infrared spectrum of the product includes two features at 1697 and 1732 cm⁻¹ for the NBE/CO copolymer in CH₃OH that are attributed to carbonyl groups in ketones (repeating unit) and esters (end group), respectively. Due to the tension of the ring of norbornene, the degree of copolymerization is not high. Published in Russian in Kinetika i Kataliz, 2007, Vol. 48, No. 1, pp. 51–58. This article was submitted by the authors in English.