Synthesis,characterization, and reactivity of the neutral metal formyl (η5-C5Me5)(CO)2(PPh3)MoCHO. A new route to monocationic secondary alkoxycarbene complexes [(η5-C5Me5)(CO)2(PPh3)Mo(CHOE)]+ X− (E = H,Me)

(η⁵-C₅Me₅)(CO)₂(PPh₃)MoCHO (2) one of the few isolated neutral metal formyls, reacts with the electrophilic reagents (CF₃COOH and CH₃SO₃F without disproportionation to give the secondary carbene complexes [(η⁵-C₅Me₅)(CO)₂(PPh₃)Mo(CHOE)]⁺ X⁻ (E = H, X = CF₃COO (4); E = Me, X = PF₆ (5)).     

Zur reaktion von metall-koordiniertem kohlenmonoxid mit yliden : VII. Trimethylphosphoranylidenmethyl(trimethylsiloxy)carben-komplexe von chrom,molybdän und wolfram: aufbau einer metallvinyl-einheit durch c(carbanion)c(carben)-π-wechselwirkung und photochemische e/z-isomerisierung

The treatment of the hexacarbonylmetal compounds M(CO)₆ (M = Cr. Mo, W) with two equivalents Me₃PCH₂ yields the phosphonium acylmetalphosphorus ylides Me₄P[(CO)₅MC(O)CHPMe₃] 1a–1c. Their reaction with Me₃SiOSO₂CF₃ leads via O-silylation to formation of the neutral “siloxy(ylidecarbene) complexes” (CO)₅MC(OSiMe₃)CHPMe₃2a–2c, which are protonated by HX (X = Cl, CF₃SO₃) to give the thermolabile carbene complexes [(CO)₅MC(OSiMe₃)H₂CPMe₃]X, 3a, 3b. ¹H, ¹³C NMR and IR data suggest, that delocalization of the ylidic charge to the carbene carbon generates a metal-coordinated vinyl group in the case of 2a–2c. In addition this fact is proved by the X-ray analysis of 2c, for which a C(ylide)C(carbene) bond distance of 133 pm is found. 2a–2c are obtained as pure E-isomers but can be converted to the Z-isomers 2a′–2c′ upon photolysis.     

The influence of sodium trifluoroacetate on the acidity function of solutions of trifluoroacetic acid in N,N-dimethylformamide

The influence of CF₃COONa on the acidity function (H ₀) and IR spectra of the CF₃COOH-N,N-dimethylformamide (DMF)-CF₃COONa system ([CF₃COOH] ≤ [DMF], [CF₃COONa] = 0–3 M) and H ₀ of solutions of the salt in 100% CF₃COOH ([CF₃COONa] = 0–1.2 M) was studied. The addition of the salt to 100% CF₃COOH insignificantly changed solution acidity; H ₀ passed a minimum at [CF₃COONa] = 0.7 M because of the formation of (CF₃COO…H…OOCCF₃)^? anions and destruction of acid associates in the presence of the salt. Changes in the acidity of solutions of CF₃COOH in DMF caused by the addition of the salt depended on the n = [CF₃COOH]/[DMF] ratio. At n = 1, the salt almost did not influence H ₀. At n < 1, a substantial decrease in the acidity of solutions was observed, because the salt increased the degree of proton transfer in CF₃COO…H…OC(H)N(CH₃)₂ quasi-ion pairs solvated by DMF molecules.     

Theoretical study on the reaction mechanism of Pd(OAc)2-catalyzed trifluoroethylation: Role of additive CF3COOH

The mechanism of Pd(OAc)₂-catalyzed trifluoroethylation of aromatic systems is explored using the density function theory (DFT) computations. The calculation results indicate that the whole catalytic cycle involves a coordinated process of catalyst Pd(OAc)₂ with acetanilide 1a, a C–H bond activation and a two-step migration of CF₃CH₂– group. The interesting role of additive (CF₃COOH) is that it can react with substrate 2a (mesityl(trifluoroethyl)iodonium triflate) to form an active species mesityl(trifluoroethyl)iodonium trifluoroacetate 2a′. 2a′ can assist the C–H activation to decrease the rate-limiting free energy barrier of the catalytic reaction by changing the rate-limiting step from the transferring process of CF₃CH₂– group to the C–H bond activation.     

Structural control in palladium(II)-catalyzed enantioselective allylic alkylation by new chiral phosphine-phosphite and pyridine-phosphite ligands

The ligands 6-[(diphenylphosphanyl)methoxy]-4,8-di-tert-butyl-2,10-dimethoxy-5,7-dioxa-6-phosphadibenzo[a,c]cycloheptene, 1, (S)-4-[(diphenylphosphanyl)methoxy]-3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4a′]dinaphthalene, (S)-2, and (S)-4-[(diphenylphosphanyl)methoxy]-2,6-bis-trimethylsilanyl-3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a′]dinaphthalene, (S)-3, (S)-2-(3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a′]dinaphthalen-4-yloxymethyl)pyridine, (S)-4, and (S)-2-(3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a′]dinaphthalen-4-yloxy)pyridine, (S)-5, have been easily prepared.The cationic complexes [Pd(η³-C₃H₅)(L-L′)]CF₃SO₃ (L–L′=1–(S)-5) and [Pd(η³-PhCHCHCHPh)(L–L′)]CF₃SO₃ (L–L′=(S)-2–(S)-4) were synthesized by conventional methods starting from the complexes [Pd(η³-C₃H₅)Cl]₂ and [Pd(η³-PhCHCHCHPh)Cl]₂, respectively. The behavior in solution of all the π-allyl- and π-phenylallyl-(L–L′)palladium derivatives 6–14 was studied by ¹H, ³¹P{¹H}, ¹³C{¹H} NMR and 2D-NOESY spectroscopy. As concerns the ligands (S)-4 and (S)-5, a satisfactory analysis of the structures in solution was possible only for palladium–allyl complexes [Pd(η³-C₃H₅)((S)-4)]CF₃SO₃, 11, and [Pd(η³-C₃H₅)((S)-5)]CF₃SO₃, 12, since the corresponding species [Pd(η³-PhCHCHCHPh)((S)-4)]CF₃SO₃, 13, and [Pd(η³-PhCHCHCHPh)((S)-5)]CF₃SO₃, 14, revealed low stability in solution for a long time. The new ligands (S)-2–(S)-5 were tested in the palladium-catalyzed enantioselective substitution of (1,3-diphenyl-1,2-propenyl)acetate by dimethylmalonate. The precatalyst [Pd(η³-C₃H₅)((S)-2)]CF₃SO₃ afforded the allyl substituted product in good yield (95%) and acceptable enantioselectivities (71% e.e. in the S form). A similar result was achieved with the precatalyst [Pd(η³-C₃H₅)((S)-3)]CF₃SO₃. The nucleophilic attack of the malonate occurred preferentially at allylic carbon far from the binaphthalene moiety, namely trans to the phosphite group. When the complexes containing ligands (S)-4 and (S)-5 were used as precatalysts, the product was obtained as a racemic mixture in high yield. The number of the configurational isomers of the Pd-allyl intermediates present in solution in the allylic alkylation and the relative concentrations are considered a determining factor for the enantioselectivity of the process.     

Beiträge zur 14/15N-NMR-Spektroskopie CF3S-substituierter Stickstoffverbindungen mit natürlicher Isotopenhäufigkeit

Contributions on ^14/15N-N.M.R. Spectroscopy of CF₃S-substituted Nitrogen Compounds with Natural Isotope Abundance ¹⁴N and ¹⁵N data are reported of compounds of the type CF₃SNXY (X = H, Y = H, SiMe₃; X = Y = SiMe₃), (CF₃S)₂NX (X = H, CH₃, CH₂OH, SiMe₃, SnMe₃), as well as (CF₃S)₃N and [(CF₃S)₂N]₂Hg. The δ-values of the CF₃S-amines lie at higher field than those of the non-fluorinated RSNR₂ compounds. This is attributed to the large s-contribution of the S? N bond (sp² hybridization of the N atom), as a result of the electron withdrawing effect of the CF₃ group. The ? I effect of the CF₃S group on the δ-values is thereby not discernible. The notion of a p_π – d_π interaction between S and N atoms (N acting as a donor) is not supported by the ^14/15N-n.m.r. data. With the aid of known N-n.m.r. data a dependance was found between δ and EN that leads to a straight line, according to which the substituents at N can be divided into two categories with regard to their steric effect. The CF₃S substituted amines show in accord with this straight line a higher field displacement. The known regularities of the δ-values (-α, -β-effect, the influence of hydrogen bridging) are qualitatively valid for the CF₃S amines too. The substitution of Me₃Si groups by CF₃S ones enhances the shielding effect at the N-nucleus; in secondary amines an increasing s-character of the N? H bond is evident from the J_NH value.     

Synthesis and structure of pseudotetrahedral Co(II) zwitterionic complexes: trichloro(1-methylpiperazin-1-ium-N4)cobalt(II) and trichloro(1,4-dimethylpiperazin-1-ium-N4)cobalt(II)

The pseudotetrahedral cobalt(II) zwitterionic complexes, [CoCl₃(H₂Meppz)] (1) [H₂Meppz⁺=1-methylpiperazin-1-ium cation] and [CoCl₃(HMe₂ppz)] (2), [HMe₂ppz⁺=1,4-dimethylpiperazin-1-ium cation] have been synthesized and characterized in the solid state by X-ray single crystal analysis, IR spectra, magnetic measurements and electronic spectra. In both the compounds the cobalt(II) center is coordinated in a distorted tetrahedral fashion by the three chloride ions and by one nitrogen of the piperazine ring that retains the more stable chair conformation. The distorted coordination polyhedron in complex 1 preserves the C_3v symmetry while in complex 2 it retains only the m symmetry. In complex 1, the (H₂Meppz)⁺ cation binds the Co(II) ion in the equatorial position of the piperazine ring using the unmethylated N1–H nitrogen atom that is less hindered than the methylated one. Complex 2, on the contrary, is a novelty being the first example of a Co(II) ion bound in the axial position of a piperazine ring, this produces a long Co(II)–N bond, 2.108(4) Å. Electronic spectra in the solid state are in perfect accordance with the X-ray crystallographic results indicating a C_3v symmetry for complex 1 and a C_s(m) symmetry for complex 2. These complexes present strong two-center and three-center hydrogen bonds of N⁺–H⋯Cl type.     

Zur Bildung und Stabilität von Difluormethylenphosphoranen,R3P⊕-C̄–F2

Inhaltsübersicht. Die Reaktion von Difluorhalogenmethanen, CF₂X₂, mit Phosphanen, R₃P, in Gegenwart von Metallen und Carbonylverbindungen, R″R′CO, führt zur Bildung geminaler Difluorolefine, R″R′C=CF₂. Die sorgfältige Untersuchung der Einzelschritte dieser komplexen Reaktion zeigt, daß intermediär Difluorhalogenmethylphosphoniumhalogenide, [R₃P–CF₂X]X, und Difluormethylenphosphorane, R₃P^⊕ – c?^?-F₂, gebildet werden. Die Phosphoniumsalze sind stabil und können als kristalline Substanzen isoliert werden. Durch Metalle oder Phosphene werden sie zu den instabilen Difluormethylenphosphoranen reduziert. Diese zersetzen sich beim Fehlen geeigneter Reaktionspartner in Phosphan und Difluorcarben, CF₂. Ihre Bildung durch Addition von CF₂ an R₃P ist nicht möglich. Mit Halogenwasserstoffen bilden sie Difluormethylphosphoniumsalze, [R₃P-CHF₂]X. Formation and Stability of Difluoromcthylene Phosphoranes, R₃P^⊕ —c?F₂ In the presence of metals and carbonyl compounds, R″R′CO, the reaction of difluoro-halomethanes, CF₂X₂, with phosphanes, R₃P, leads to the formation of geminal difluoroolefins, R″R′C=CF₂. Our investigations have proved that difluorohalomethylphosphonium halides, [R₃P–CF₂X]X, and difluoromethylene phosphoranes, R₃P^⊕–C??F₂, are formed intermediately. The phosphonium salts are stable. They can be isolated as crystalline substances. They are reduced by metals or phosphanes forming unstable difluoromethylene phosphoranes as intermediates. These decompose into phosphane and difluorocarbene, CF₂, if suitable reactants are absent. Their reaction with hydrogen halides, HX, yields difluoromethylphosphonium salts, [R₃P–CHF₂]X. The formation of difluoromethylene phosphoranes by addition of CF₂ to R₃P is not possible.     

Copper(I) halide complexes with N,N′-diallyl-N,N,N′,N′-tetramethylethylenediaminium (L2+). Synthesis and crystal structures of the complexes [L0.5CuCl2], [L0.5CuCl0.72Br1.28], and [L0.5CuBr2]

The Eschweiler-Clarke reaction of ethylenediamine with formaldehyde and formic acid yielded N,N,N′,N′-tetramethylethylenediamine, which was alkylated with allyl chloride or allyl bromide to give the corresponding N,N′-diallyl-N,N,N′,N′-tetramethylethylenediaminium (L²⁺) dihalides. In methanolic solutions of copper(II) halide and an appropriate ligand, ac electrochemical synthesis with copper wire electrodes afforded single crystals of Cu(I) complexes with L²⁺: [L_0.5CuCl₂] (I), [L_0.5CuCl_0.72Br_1.28] (II), and [L_0.5CuBr₂] (III). The crystal structures of complexes I–III were determined by X-ray diffraction study. The isostructural crystals of I and II are monoclinic, space group P2₁/n, Z = 4. For I: a = 7.632(4) Å, b = 11.318(5) Å, c = 10.635(5) Å, β = 98.551(7)°, V = 908.4(7) ų. For II: a = 7.7415(7) Å, b = 11.4652(9) Å, c = 10.7267(10) Å, β = 98.351(4)°, V = 942.0(2) ų. The organic cation L²⁺ acts as a bridge linking a pair of separate cuprous halide fragments Cu₂X₄. Although being isostoichiometric with I and II, complex III has a different structure. The crystals of III are monoclinic, space group P2₁/c, a = 6.519(2) Å, b = 9.060(3) Å, c = 16.284(6) Å, β = 97.219(4)°, V = 954.2(6) ų, Z = 4. In structure III, the inorganic fragment forms infinite polymer chains (CuBr ₂ ^? ) _n . The organic and inorganic parts are held together only by electrostatic interactions. Structures I–III are stabilized by hydrogen bonds (C)H…X (2.6–2.9 Å).     

Acid Co(II) and Ni(II) trifluoroacetate complexes: Synthesis and crystal structure

Anhydrous and partially hydrated acid trinuclear trifluoroacetates of divalent transition metals of the composition [M₃(CF₃COO)₆(CF₃COOH)₆)](CF₃COOH) and [M₃(CF₃COO)₆(CF₃COOH)₂(H₂O)₄)](CF₃COOH)₂, respectively, where M = Co (I, III) Ni (II, IV), were synthesized and studied by X-ray diffraction. Complexes I and II were obtained by crystallization from solutions of M(CF₃COO)₂ · 4H₂O in trifluoroacetic anhydride; complexes III and IV were synthesized under the same conditions with the use of 99% trifluoroacetic acid as a solvent. Crystals I are triclinic: space group $P\bar 1$ , a = 13.199(6) Å, b = 14.649(6) Å, c = 15.818(6) Å, α = 90.04(4)°, β = 114.32(4)°, γ = 108.55(4)°, V = 2611.3(19) ų, Z = 2, R = 0.0480. Crystals II are trigonal: space group $R\bar 3$ , a = 13.307(2) Å, c = 53.13(1) Å, V = 8148(2) ų, Z = 6, R = 0.1112. Crystals III are triclinic: space group $P\bar 1$ , a = 9.001(8) Å, b = 10.379(9) Å, c = 12.119(9) Å, α = 83.67(5)°, β = 72.33(5)°, γ = 83.44(5)°, V = 1068.3(15) ų, Z = 1 Å, R = 0.1031. Crystals IV are triclinic: space group $P\bar 1$ , a = 9.121(18) Å, b = 10.379(2) Å, c = 12.109(2) Å, α = 84.59(3)°, β = 72.20(3)°, γ = 82.80(3)°, V = 1080.94(40) ų, Z = 1, R = 0.0334.     

Application of Langlois' reagent（NaSO2CF3） in C–H functionalisation

The process of selectively introducing a CF₃ group into an organic molecule using inexpensive,stable,and solid sodium trifluoromethanesulfinate has rapidly advanced in recent years to become an eco-friendly method used by organic chemists to synthesize various natural and bioactive molecules.This review focuses on advances made within the last five years regarding C-H functionalisation,namely thermochemical C（sp²）-H（thio）trifluoromethylations,photochemical C（sp²）...     

Trichloro- and methyldichlorogermyl monochelates and dibromo- and dichlorogermyl bischelates derived from N,N-disubstituted amides of 2-hydroxycarboxylic acids

The reactions of GeCl₄, GeBr₄, and MeGeCl₃ with O-trimethylsilyl derivatives of N,N-disubstituted amides of 2-hydroxycarboxylic acids afforded pentacoordinate and hexacoordinate neutral (O,O)-mono- and (O,O)-bischelates. The reactions of glycolic acid derivatives with GeX₄ produced bischelates X₂Ge[OCH₂C(O)NR²R³]₂ 7a,c,d (X = Cl, R² = R³ = Me (a), (CH₂)₅ (c), (CH₂CH₂)₂O (d)) and 8a (X = Br). By contrast, the reactions of lactic and mandelic acid derivatives with GeCl₄ and MeGeCl₃ gave monochelates Cl₃Ge[OCH(R¹)C(O)NR²R³] (S)-9a–c (R¹ = Me) and Cl₂MeGe[OCH(R¹)C(O)NR²R³] 10a (R¹ = H), (S)-11a,b (R¹ = Me), and (S)-12a (R¹ = Ph) (R²R³ = (CH₂)₄ (b)), respectively. According to the X-ray diffraction data, the Ge atom in bischelates 7c,d and 8a has a coordination number 6, and its coordination polyhedron can be described as a slightly distorted octahedron. In monochelates (S)-9a-c, 10a, (S)-11a,b, and (S)-12a, the Ge atom has a coordination number 5, and its coordination polyhedron can be described as a trigonal bipyramid with two halogen atoms or one halogen atom and one ethereal oxygen atom in equatorial positions and the halogen atom and the amide oxygen atom in the axial positions. The bonds in the axial positions are somewhat longer than the corresponding bonds in tetracoordinate Ge compounds.     

Metallacumulenylidene complexes in the [(η5-C5Me5)(η2-dppe)Fe(=C(=C)nR2)]X (n = 0, 1, 2) series: investigations of the iron-carbon bonding by Mössbauer spectroscopy and X-ray analyses

The synthesis of the iron allenylidene complexes [(η⁵-C₅Me₅)(η²-dppe)Fe(=C=C=C(Ph)Ph)][X] (5a, X = PF₆, 95%; 5b, X = BPh₄, 91%; dppe = 1,2-bis(diphenylphosphino)ethane) was achieved by reacting the complex (η⁵-C₅Me₅)(η²-dppe)FeCl (10) with 1 equiv of 1,1-diphenyl-prop-2-yn-1-ol in methanol in the presence of KPF₆ or NaBPh₄. Surprisingly, when the reaction was carried out in the presence of the tetraphenylborate anion, the final product contained both 5b and the hydroxyvinylidene [(η⁵-C₅Me₅)(η²-dppe)Fe(=C=C(H)C(OH)(Ph)₂)][BPh₄] (14b) in the 1:1 ratio. Further treatment of the mixture with Amberlyst 15 in methanol provided the allenylidene 5b as a pure sample. The allenylidene complexes [(η⁵-C₅Me₅)(η²-dppe)Fe(=C=C=C(Me)Ph)][PF₆] (6) and [(η⁵-C₅Me₅)(η²-dppe)Fe(=C=C=C(Me)Et)][PF₆] (7) were prepared according to the same procedure and they were isolated as purple powders in 90% yield. The X-ray crystal structures were determined for the vinylidene complexes [(η⁵-C₅Me₅)(η²-dppe)Fe(=C=CH₂)][PF₆] (3) and [(η⁵-C₅Me₅)(η²-dppe)Fe(=C=C(Ph)H)][PF₆] (4), and the allenylidene derivative 5a. In the homogeneous series of complexes [(η⁵-C₅Me₅)(η²-dppe)Fe(=(C)_n(R)R’)][PF₆], (n = 1, R = H, R′ = Me, X = PF₆, 1; n =1, R = H, R’ = OMe, X = PF₆, 2a; n = 1, R = H, R’ = OMe, X = CF₃OSO₂, 2b; n = 2, R = R′ = H, X = PF₆, 3; n = 2, R = H, R′ = Ph, X = PF₆, 4; n = 3, R = R′ = Ph, X = PF₆, 5a; n = 3, R = R′ = Ph, X = BPh₄, 5b; n = 3, R = Me, R′ = Ph, X = PF₆, 6; n = 3, R = Me, R′ = Et, X = PF₆, 7; n = 3, R = Me, R′ = OMe, X = BPh₄, 8), an empiric relationship between the Mössbauer parameters, δ and QS, was found. This observation would indicate that the positive charge on the iron nucleus decreases with the Fe=C bond order. Moreover, in this series of iron cumulenylidene derivatives, comparison of the variation of the metal–carbon bond distances determined by X-ray analyses with the Mössbauer QS values allows the observation of a linear correlation (R = 0.99). To cite this article: G. Argouarch et al., C. R. Chimie 6 (2003).     

Tris- and tetrakis-(trifluoromethyl)fluorogermanates; the structure of an anion with pentacoordinated germanium

Reactions of (CF₃)₃GeX (X = halogen) or (CF₃)₄Ge with fluoride ions in aqueous or acetonitrile solutions give the trigonal-bipyramidal (CF₃)₃GeF₂⁻ and octahedral fac-(CF₃)₃GeF₃²⁻ or cis-(CF₃)₄GeF₂²⁻ anions, respectively. The crystal structure of [(CH₃)₄N][(CF₃)₃GeF₂] has been determined. The symmetry of the anion (C_s) approximates to C₃v, with axial F atoms (r_av(GeF) 1.835(8) Å) and equatorial CF₃ groups (r_av(GeC) 2.000(5) Å) (both distances corrected for libration). The bonding in the anion is discussed on the basis of structural and vibrational spectral data. The configurations of the octahedral complexes have been deduced from their ¹⁹F NMR spectra.     

Synthesis,structure, spectroscopy and redox energetics of a series of uranium(IV) mixed-ligand metallocene complexes

A series of uranium(IV) mixed-ligand amide–halide/pseudohalide complexes (C₅Me₅)₂U[N(SiMe₃)₂](X) (X = F (1), Cl (2), Br (3), I (4), N₃ (5), NCO (6)), (C₅Me₅)₂U(NPh₂)(X) (X = Cl (7), N₃ (8)), and (C₅Me₅)₂U[N(Ph)(SiMe₃)](X) (X = Cl (9), N₃ (10)) have been prepared by one electron oxidation of the corresponding uranium(III) amide precursors using either copper halides, silver isocyanate, or triphenylphosphine gold(I)azide. Agostic U?H–C interactions and η³-(N,C,C′) coordination are observed for these complexes in both the solid-state and solution. There is a linear correlation between the chemical shift values of the C₅Me₅ ligand protons in the ¹H NMR spectra and the U^IV/U^III reduction potentials of the (C₅Me₅)₂U[N(SiMe₃)₂](X) complexes, suggesting that there is a common origin, that is overall σ-/π-donation from the ancillary (X) ligand to the metal, contributing to both observables. Optical spectroscopy of the series of complexes 1–6 is dominated by the (C₅Me₅)₂U[N(SiMe₃)₂] core, with small variations derived from the identity of the halide/pseudohalide. The considerable π-donating ability of the fluoride ligand is reflected in both the electrochemistry and UV-visible-NIR spectroscopic behavior of the fluoride complex (C₅Me₅)₂U[N(SiMe₃)₂](F) (1). The syntheses of the new trivalent uranium amide complex, (C₅Me₅)₂U[N(Ph)(SiMe₃)](THF), and the two new weakly-coordinating electrolytes, [Pr₄N][B{3,5-(CF₃)₂C₆H₃}₄] and [Pr₄N][B(C₆F₅)₄], are also reported.     

Bonding isomerism in the η-P coordination of the P4X3 (X=S, Se) molecules toward 16e rhodium fragments stabilized by tripodal tetradentate ligands

The reaction of tetraphosphorus trichalcogenides P₄X₃ (X=S, Se) with the electronically and coordinatively unsaturated 16 electron systems [(EP₃)Rh]⁺ [E=N, NP₃=tris(2-diphenylphosphanylethyl)amine, (1); E=P, PP₃=tris(2-diphenylphosphanylethyl)phosphane, (2)] in tetrahydrofuran affords new tetraphosphorus trichalcogenide derivatives of formula [(EP₃)Rh(P₄X₃)]CF₃ SO₃ [E=N; X=Se (3), S (5). E=P; X=Se (4), S (6)]. In the P₄Se₃ derivatives 3 and 4 the heptatomic cage is bound to the metal through the apical phosphorus atom. The P₄S₃ derivatives 5 and 6 are obtained as pairs of coordination isomers, with the cage linked to the metal either through the apical or through one of the basal P atoms; the former isomer is predominant and its amount depends on the nature of the trans-disposed apical donor (N or P) of the tripodal ligand. The monometal species [(NP₃)Rh(η¹-P₄S₃)]CF₃SO₃ (5) reacts with 1 affording the dimetal compound [{(NP₃)Rh}₂(μ,η^1:1-P_apical,-P_basal-P₄S₃)](CF₃SO₃)₂, where the cage exhibits both modes of bonding. All of the compounds have been characterized by ³¹P NMR spectra and elemental analyses.     

Hydrogen bonding and halogen bonding co-existing in the reaction of heptafluorobenzyl iodide with N,N,N,N-tetramethylethylene diamine

Two novel assembling systems 3 and 4, with the structures of C₆F₅CF₂⁻?H⁺N(Me)₂CH₂CH₂(Me₂)N⁺H?⁻CF₂C₆F₅ and C₆F₅CF₂I?N(Me)₂CH₂CH₂(Me)₂N?ICF₂C₆F₅, respectively, have been generated from the solution of heptafluorobenzyl iodide 1 and N,N,N^′,N^′-tetramethylethylenediamine 2 in dichloromethane. Their structures have been characterized by X-ray diffraction analysis, NMR and IR spectroscopy. Intermolecular N?I halogen bond and F?H hydrogen bond are revealed to be the driving forces for their formation.     

Recent advance in transition-metal-mediated trifluoromethylation for the construction of C(sp)–CF3 bonds

In the past 5 years, transition-metal-mediated trifluoromethylation for the construction of various CF₃-containing building blocks has been the focus of recent research in both industrial and academic communities. Progresses in the construction of C(sp²)–CF₃ bonds and C(sp)–CF₃ have been well reviewed. This Letter will focus on the cases of transition-metal-mediated C(sp³)–CF₃ bond formation, which involves the trifluoromethylation of sp³-hybridized C–X bonds, alkyl organometallic reagents, sp³-hybridized C–H bonds, and alkene derivatives.     

Triferrocenyl-komplexe von wolfram(VI): Molekülstruktur im festkörper und dynamisches verhalten in Lösung von triferrocenyl-ferrocenoxy-oxo-wolfram,WO(OFc)Fc3

Triferrocenyltungsten complexes of the type WO(X)Fc₃ (X = Cl, (1), OMe (2), OFc (3) and OⁿBu (4)) were obtained by treating WOCl₄ with ferrocenyllithium, FcLi, in tetrahydrofuran solution¹. Reaction of WOCl₄ with a threefold excess of FcLi gives 1, which may be converted into 2 using KOCH₃. Reaction of WOCl₄ with a sixfold excess of FcLi gives a mixture containing 3 und 4 in addition to ferrocene and biferrocene. According to the X-ray crystallographic analysis, WO(OFc)Fc₃ (3) has a trigonal-bipyramidal structure with three ferrocenyl ligands occupying the equatorial positions and an axial ferrocenoxy group coordinated trans to the oxo ligand. The three WC(ferrocenyl) (average 2.092 Å) and the OC(ferrocenyl) (1.33(1) Å) bond distances are remarkably short. The axial tungsten—oxygen distances correspond to a WO double and a WO single bond (1.705(5) and 1.945(5) Å), respectively. The ¹H and ¹³C NMR spectra of WO(OFc)Fc₃ (3) are temperature-dependent. This is ascribed to a hindered rotation of the ferrocenyl ligands around the WC(ferrocenyl) bonds; the free activation enthalpy ΔG^≠(T_c) of this intramolecular dynamic process is 62.5 ± 0.5 kJ mol⁻¹.     

Five-coordinate pentafluorobenzothiolate osmium(IV) complexes [Os(SC6F5)4(P(C6H4X-4)3)] (X = OCH3, CH3, F, Cl or CF3): Solid and solution structural characterization

The reactions of OsO₄ with excess of HSC₆F₅ and P(C₆H₄X-4)₃ in ethanol afford the five-coordinate compounds [Os(SC₆F₅)₄(P(C₆H₄X-4)₃)] where X = OCH₃ 1a and 1b, CH₃ 2a and 2b, F 3a and 3b, Cl 4a and 4b or CF₃ 5a and 5b. Single crystal X-ray diffraction studies of 1 to 5 exhibit a common pattern with an osmium center in a trigonal-bipyramidal coordination arrangement. The axial positions are occupied by mutually trans thiolate and phosphane ligands, while the remaining three equatorial positions are occupied by three thiolate ligands. The three pentafluorophenyl rings of the equatorial ligands are directed upwards, away from the axial phosphane ligand in the arrangement “3-up” (isomers a). On the other hand, ³¹P{¹H} and ¹⁹F NMR studies at room temperature reveal the presence of two isomers in solution: The “3-up” isomer (a) with the three C₆F₅-rings of the equatorial ligands directed towards the axial thiolate ligand, and the “2-up, 1-down” isomer (b) with two C₆F₅-rings of the equatorial ligands directed towards the axial thiolate and the C₆F₅-ring of the third equatorial ligand directed towards the axial phosphane. Bidimensional ¹⁹F–¹⁹F NMR studies encompass the two sub-spectra for the isomers a (“3-up”) and b (“2-up, 1-down”). Variable temperature ¹⁹F NMR experiments showed that these isomers are fluxional. Thus, the ¹⁹F NMR sub-spectra for the “2-up, 1-down” isomers (b) at room temperature indicate that the two S-C₆F₅ ligands in the 2-up equatorial positions have restricted rotation about their C–S bonds, but this rotation becomes free as the temperature increases. Room temperature ¹⁹F NMR spectra of 3 and 5 also indicate restricted rotation around the Os–P bonds in the “2-up, 1-down” isomers (b). In addition, as the temperature increases, the ¹⁹F NMR spectra tend to be consistent with an increased rate of the isomeric exchange. Variable temperature ³¹P{¹H} NMR studies also confirm that, as the temperature is increased, the a and b isomeric exchange becomes fast on the NMR time scale.