Reactions of tetrakis(trifluoromethyl) diphosphine and bis(trifluoromethyl) phosphine with ruthenium carbonyl clusters; X-ray structure of tetraruthenium carbonyl cluster derivatives

Reaction of [Ru₃(CO)₁₂ with (CF₃)₂P---P(CF₃)₂ in p-xylene at 140°C yielded the compounds [Ru₄(CO)₁₃{μ-P(CF₃)₂}₂] (1), [Ru₄(CO)₁₄{μ-P(CF₃)₂}₂] (2) and [Ru₄(CO)₁₁{μ-P(CF₃)₂}₄] (3). Reaction with [(μ-H)₄Ru₄(CO)₁₂] under similar conditions yielded [(μ-H)₃Ru₄(CO)₁₂{μ-P(CF₃)₂}] (4). All four compounds have been characterised by X-ray crystallography. The fluxional behaviour of the hydrides in 4 has also been studied by variable-temperature NMR spectroscopy. Compounds 1, 2 and 4 were also obtained from the reactions of Ru₃(CO)₁₂ with (CF₃)₂PH in dichloromethane at 80°C.     

Structures and conformations of trifluoromethanesulfonic anhydride, (CF3SO2)2O, and bis(trifluoromethylsulfonyl)difluoromethane, (CF3SO2)2CF2

The geometric structures and conformational properties of trifluoromethanesulfonic anhydride, (CF₃SO₂)₂O, and bis(trifluoromethylsulfonyl)difluoromethane, (CF₃SO₂)₂CF₂ have been studied by gas electron diffraction (GED) and ab initio calculations (HF/3–21G*). The calculations predict for both systems two stable conformers with C₂ symmetry and one with C₁ symmetry. In both compounds structures with C₂ symmetry and dihedral angles SOSC ≈ 100° ((CF₃SO₂)₂O) and SCSC ≈ 150° ((CF₃SO₂)₂CF₂) are lowest in energy. According to the GED analyses the dominant conformer of (CF₃SO₂)₂O possesses C₂ symmetry with SOSC dihedral angles of 99.1(14)°. The presence of up to 30% of the two other conformers cannot be excluded; for (CF₃SO₂)₂CF₂ only one conformer with C₂ symmetry and SCSC dihedral angles of 143(2)° is observed. A complete set of geometric parameters is given.     

Synthesis and molecular structure of Ba5(μ5-OH)[μ3-OCH(CF3)2]4[μ2-OCH(CF3)2]4 [OCH(CF3)2](THF)4(H2O)·THF: a source of barium fluoride

The reaction between metallic barium and fluoroisopropanol or alcoholysis of [Ba(OPrⁱ)₂] produces a pentanuclear fluoroalkoxide. Its X-ray structure determination showed its formulation to correspond to Ba₅(μ₅-OH)[μ₃-OCH(CF₃)₂]₄[μ₂-OCH(CF₃)₂]₄ [OCH(CF₃)₂](THF)₄(H₂O)·THF. The metallic core is based on a square pyramid encapsulating an hydroxo ligand. In addition to the barium---alkoxide bonds [2.53(3)–2.86(3) Å] neutral O-donors, four THF [2.82(2)–2.86(3) Å] and one H₂O [2.79(3) Å] and secondary barium---fluorine interactions [2.99(2)–3.31(2) Å] ensure high coordination numbers, from 9 to 11 for the metal centers. Hydrogen bonding between the apical fluoroisopropoxide, the water molecule and one THF molecule, non-bonded to a metal center, accounts for the stability of the hydrate and illustrates the Lewis acidity of fluoroalkoxides. Thermal decomposition leads to BaF₂.     

Structures and conformations of trifluoromethanesulfonic anhydride, (CF3SO2)2O, and bis(trifluoromethylsulfonyl)difluoromethane, (CF3SO2)2CF2

The geometric structures and conformational properties of trifluoromethanesulfonic anhydride, (CF₃SO₂)₂O, and bis(trifluoromethylsulfonyl)difluoromethane, (CF₃SO₂)₂CF₂ have been studied by gas electron diffraction (GED) and ab initio calculations (HF/3–21G*). The calculations predict for both systems two stable conformers with C₂ symmetry and one with C₁ symmetry. In both compounds structures with C₂ symmetry and dihedral angles SOSC ≈ 100° ((CF₃SO₂)₂O) and SCSC≈ 150° ((CF₃SO₂)₂CF₂ are lowest in energy. According to the GED analyses the dominant conformer of (CF₃SO₂)₂O₂ possesses C₂ symmetry with SOSC dihedral angles of 99.1(14)°. The presence of up to 30% of the two other conformers cannot be excluded; for (CF₃SO₂)₂CF₂ only one conformer with C₂ symmetry and SCSC dihedral angles of 143(2)° is observed. A complete set of geometric parameters is given.     

Vibrational spectra and microstructure of poly(ε-caprolactone)/siloxane biohybrids doped with lithium triflate

Fourier Transform infrared (FT-IR) and Raman (FT-Raman) spectroscopies and Scanning Electron Microscopy (SEM) were used to investigate ionic association, hydrogen bonding and morphology in a family of sol–gel derived lithium triflate (LiCF₃SO₃)-doped di-urethane cross-linked poly(ε-caprolactone) (PCL(530))/siloxane hybrid electrolytes. The materials studied, with compositions ∞ > n  0.5 (where n – composition – expresses the molar ratio of PCL(530) ester repeat units per Li⁺ ion), are non-porous and homogeneous. The Li⁺ ions interact with the urethane and ester carbonyl oxygen atoms within the whole range of salt concentration analyzed, promoting the formation of hydrogen-bonded aggregates. The composition dependence of the relative concentration of “free” anions and coordinated anions (weakly coordinated anions, ion pairs or [Li(CF₃SO₃)₂]⁻ triplets, aggregates I ([Li₂(CF₃SO₃)]⁺) and aggregates II ([Li₃(CF₃SO₃)]²⁺) in all the samples is in perfect agreement with the values of the room temperature ionic conductivity reported previously.     

Monodentate and bidentate trifluoroacetato ligands in bis(trifluoroacetato)-(N-methyl-meso-tetraphenylporphyrinato)thallium(III)—a new dynamic 4:3 piano stool seven-coordinate geometry

The crystal structure of bis(trifluoroacetato)-(N-methyl-meso-tetraphenylporphyrinato) thallium(III), Tl(N---Me---tpp)(CF₃CO₂)₂ (2), was established and the coordination sphere around the Tl³⁺ ion is described as 4:3 tetragonal base–trigonal base piano stool seven-coordinate geometry in which the two cis CF₃CO₂ ⁻ groups occupy two apical sites. The plane of the three pyrrole nitrogen atoms [i.e. N(2), N(3) and N(4)] strongly bonded to Tl³⁺ is adopted as the reference plane 3N. The pyrrole N(1) ring bearing the methyl group [i.e. C(45)H₃] is the most deviated one from the 3N plane making a dihedral angle of 23.3° whereas smaller angles of 9.9, 2.7 and 4.7° occur with pyrroles N(2), N(3), and N(4), respectively. Because of the larger size of the thallium(III) ion, Tl is considerably out of the 3N plane; its displacement of 1.02 Å is in the same direction as that of the two apical CF₃CO₂ ⁻ ligands. The intermolecular trifluoroacetate exchange process for 2 in CD₂Cl₂ solvent is examined through ¹⁹F and ¹³C NMR temperature-dependent measurements. In the slow-exchange region, the CF₃ and carbonyl (CO) carbons of the CF₃CO₂ ⁻ groups in 2 are separately located at δ 114.3 [¹J(C–F)=290 Hz, ³J(Tl–C)=411 Hz] and 155.1 [²J(C–F)=37 Hz, ²J(Tl–C)=204 Hz], respectively, at −106 °C. In the same slow-exchange region, the fluorine atoms of 2, Tl(N---Me---tpp)(CF₃CO₂)⁺ and the free CF₃CO₂ ⁻ are located at δ −73.76 [⁴J(Tl–F)=44 Hz], −73.30 [⁴J(Tl–F)=22 Hz], and −76.15 ppm at −97 °C, respectively.     

The use of NMR for determination of new structures in irradiated TFE/PMVE fluoropolymers

The radiation chemistry of two TFE/PMVE copolymers with TFE mole fractions of 0.66 and 0.81 has been studied under vacuum using ⁶⁰Co γ-radiation over absorbed dose ranges up to 4.2 MGy. The radiolysis temperature was 313 K for both TFE/PMVE copolymers. New structure formation in the copolymers was identified by solid-state ¹⁹F NMR and the G-values for new chain ends of 2.1 and 0.5 and for branching sites of 0.9 and 0.2 have been obtained for the TFE/PMVE with TFE mole fractions of 0.66 and 0.81, respectively. The relative yields of –O–CF₃ and –CF₂–CF₃ chain ends were found to be proportional to the copolymer composition, but the yields of the –CF₂–CF₃ chain ends and –CF– branch points were not linearly related to the composition, rather they were correlated with the radical yields measured at 77 K.     

Preparation and characterization of ruthenium(II), rhodium(III) and iridium(III) complexes of isocyanide bearing the azo group

Reactions of [(η⁶-arene)RuCl₂]₂ (1) (η⁶-arene=p-cymene (1a), 1,3,5-Me₃C₆H₃ (1b), 1,2,3-Me₃C₆H₃ (1c) 1,2,3,4-Me₄C₆H₂(1d), 1,2,3,5-Me₄C₆H₂ (1e) and C₆Me₆ (1f)) or [Cp*MCl₂]₂ (M=Rh (2), Ir (3); Cp*=C₅Me₅) with 4-isocyanoazobenzene (RNC) and 4,4′-diisocyanoazobenzene (CN–R–NC) gave mononuclear and dinuclear complexes, [(η⁶-arene)Ru(CNC₆H₄N=NC₆H₅)Cl₂] (4a–f), [Cp*M(CNC₆H₄N=NC₆H₅)Cl₂] (5: M=Rh; 6: M=Ir)_, [{(η⁶-arene)RuCl₂}₂{μ-CNC₆H₄N=NC₆H₄NC}] (8a–f) and [(Cp*MCl₂)₂(μ-CNC₆H₄N=NC₆H₄NC)}] (9: M=Rh; 10: M=Ir)_, respectively. It was confirmed by X-ray analyses of 4a and 5 that these complexes have trans-forms for the ---N=N--- moieties. Reaction of [Cp*Rh(dppf)(MeCN)](PF₆)₂ (dppf=1,1′-bis (diphenylphosphino)ferrocene) with 4-isocyanoazobenzene gave [Cp*Rh(dppf)(CNC₆H₄N=NC₆H₅)](PF₆)₂ (7), confirmed by X-ray analysis. Complex 8b reacted with Ag(CF₃SO₃), giving a rectangular tetranuclear complex 11b, [{(η⁶-1,3,5-Me₃C₆H₃)Ru(μ-Cl}₄(μ-CNC₆H₄N=NC₆H₄NC)₂](CF₃SO₃)₄ bridged by four Cl atoms and two μ-diisocyanoazobenzene ligands. Photochemical reactions of the ruthenium complexes (4 and 8) led to the decomposition of the complexes, whereas those of 5, 7, 9 and 10 underwent a trans-to-cis isomerization. In the electrochemical reactions the reductive waves about −1.50 V for 4 and −1.44 V for 8 are due to the reduction of azo group, [---N=N---]→[---N=N---]²⁻. The irreversible oxidative waves at ca. 0.87 V for the 4 and at ca. 0.85 V for 8 came from the oxidation of Ru(II)→Ru(III).     

Perfluoromethyl—element-liganden : XX. Bildung von heteronuclearen zweikernkomplexen des typs mm′(CO)nXY (M = Mn; M′ = Re, Co)

The reactions of MnRe(CO)₁₀ with As₂(CF₃)₄ and MnCo(CO)₉ with P₂(CF₃)₄, As₂(CF₃)₄, S₂(CF₃)₂, Se₂(CF₃)₂, (CF₃)₂EI (E = P, As), (CF₃)₂AsH, (CF₃)₂AsE′CF₃ (E′ = S, Se), (CF₃)₂PSeCF₃, Me₂AsI and (CF₃)₂PPMe₂, respectively, have been studied under various conditions. Besides already known mono- and binuclear compounds the heteronuclear complexes MnRe(CO)₈[As(CF₃)₂]₂ and MnCo(CO)₇[E(CF₃)₂]₂ (E = P, As) are formed. The reactions proceed via cleavage of the M---M′ bond and formation of the mononuclear species Mn(CO)₅X and M′(CO)_nY (M′ = Re, n = 5; M′ = Co, n = 4).     

Polymer chemistry. Part V. γ-Ray induced telomerisation reactions involving 1,1-difluoroethene and hexafluoropropene

Telomerisation reactions have been investigated for the alkenes 1,1-difluoroethene (5) and hexafluoropropene (3) with the telogens CF₂Br₂ (1), CF₃CFBr₂ (8) and CF₃CBr₃ (9), as a means of preparing telomers and co-telomers. The efficiency of chain transfer increases as 18<9. Surprisingly, co-telomerisations of 5 with 3 occurred more efficiently than the corresponding telomerisations with 5 alone. The effects of solvent are described.     

Solvothermal syntheses and crystal structures of two metal coordination polymers with double-chain structures

Two polymeric complexes, [Cu₂(btec)(phen)₂]_n·(H₂O)_n (1) and [Cd₄(btec)₂(phen)₄(H₂O)₄]_n (2) (H₄btec=1,2,4,5-benzenetetracarboxylic acid; PHEN=1,10-phenanthroline), were synthesized by solvothermal reactions at 140 °C. Both complex 1 and 2 possess infinite double-chain structures, in which each Cu(II) center has a tetrahedral configuration and the Cd(II) centers adopt triangular prismatic and square-based pyramidal configurations simultaneously. The inter-chain face to face π–π interactions among the aromatic rings of phen and the hydrogen bond interactions between aqua molecules and carboxyl O atoms result in 3-D networks in the two complexes. The ESR spectra study of complex 1 shows that there is negligibly small long-range super-exchange interactions between the Cu(II) atoms via benzenecarboxylate bridging.     

O- versus F-protonation in (CF3CF2)2O and CF3OCF(CF3)2: a preliminary theoretical study

The relative modifications induced in the structure of perfluorodiethyl ether (CF₃CF₂)₂O and perfluoroisopropyl methyl ether CF₃OCF(CF₃)₂ by oxygen and fluorine protonation are studied at the RHF level with the 3–21G basis and correlated with their proton affinities and dissociation energies.     

The gas phase structure of tetrakis(trifluoromethylthio)ethene, CF3S)2C=C(SCF3)2

The geometric structure of (CF₃S)₂C=C(SCF₃)₂ in the vapour phase was determined by electron diffraction. The molecule possesses D₂ symmetry with the S---CF₃ bonds oriented perpendicular to the ethene plane, in alternating directions up-down-up-down. The following skeletal geometric parameters were obtained (r_a distances and angles, experimental uncertainties are 3σ values): C=C = 1.34Å (ass.), C(sp²---S = 1.761(5)Å, S---C(sp³) = 1.832(5)Å, S---C---C = 119.6(4)°, C---S---C = 100.6(13)°, and ø(C=C---S---C) = 90.9(11)°. The gas phase conformation differs considerably from the crystal structure, where the molecule possesses C_i symmetry and the CF₃ groups, which are bonded to cis-standing sulfur atoms, lie on the same side of the ethene plane with dihedral angles ø(C=C---S---C) of 117° and 127°.     

Nitrous oxide gas phase chemistry during silicon oxynitride film growth

N₂O gas phase chemistry has been examined as it relates to the problem of ultrathin film silicon oxynitridation for semiconductor devices. Computational and analytical kinetics studies are presented that demonstrate: (i) there are 5 main reactions in the decomposition of N₂O, (ii) the gas composition over a 1000K – 1400K temperature range is as follows: N₂ (65.3 − 59.3%); O₂ (32.0 − 25.7%); NO (2.7 − 15.0%), (iii) the N₂O decomposition obeys first-order kinetics, and the initial rate law for N₂O decomposition is R_init = 2k₁[N₂O] which rapidly changes to R_late = k₁[N₂O] as the reaction proceeds, (iv) the branching ratio for the two reactions: N₂O + O → 2NO and N₂O + O → N₂ + O₂ lies between 0.1 and 0.5 (0.1 < < 0.5) and varies with conditions, (v) the apparent activation energy for the decomposition of N₂O is 2.5 eV/molecule (2.4×10² kJ/mole), (vi) the rate law for NO formation is R = k₁N₂O], and (vii) the apparent activation energy for the formation of NO is 2.4 eV/molecule (2.3×10² kJ/mole).     

Ergebnisse aus versuchen zur darstellung von bis(trifluormethylsulphanyl)thioketen (CF3S)2C=C=S

The attempted preparation of bis(trifluoromethylsulphanyl)thioketene is described. Mono-and di-(trifluoromethylsulphanyl)-substituted orthothioesters may be prepared fromCH₃C(SC₂H₅)₃ and CF₃SCl in the presence of anhydrous ZnCl₂. The unstable compoundshave been isolated and characterized. The corresponding CF₃Se and CF₃SO₂ derivativesare only formed as intermediates which decompose to ketene diethylmercaptal. Suchmono- and di-substituted products are obtained in good yield from H₂C=C(SC₂H₅)₂ andCF₃ECl (E=S, Se). The reaction of H₂C=C(SC₂H₅)₂ with CF₃SO₂F gave only poor yieldsof (CF₃SO₂)_nCH_2−n=C(SC₂H₅)₂ (n=1, 2) which were only capable of characterizationin etheral solution by spectral means. Attempts to prepare (CF₃S)₂C=C=S by refluxing(CF₃S)₂CHC(O)Cl, (CF₃S)₂CHC(O)OH or (CF₃S)₂C=C=O with P₄S₁₀ in toluene yieldedonly the cyclic dimer and the corresponding 1,3,4-trithiolan.     

Novel perfluoroalkenylphosphonates and iodoperfluoroalkenes from 3,3 -bis (trifluoromethyl) -1,1,2,4,4,4-hexafluoro-1-butylene and nonafluoro-n-butoxy-1,1,2-trifluoroethylene

The reaction of 3,3-bis(trifluoromethyl)-1,1,2,4,4,4-hexafluoro-1-butylene and nonafluoro-n-butoxy-1,1,2-trifluoroethylene with tris(trimethylsilyl)phosphite gave fluorotrimethylsilane and the respective (Z)-alkenylbis(trimethylsilyl)phosphonates. In one case hydrolysis afforded the free phosphonic acid (CF₃)₃CCF = CFP(O) (OH)₂. Using tri-n-butylphosphine and boron trifluoride etherate, 3,3-bis(trifluoromethyl)-1,1,2,4,4,4-hexafluoro-1-butylene and nonafluoro-n-butoxy-1,1,2-trifluoroethylene were converted into the corresponding phosphonium tetrafluoroborates, which when reacted further with iodine in the presence of Na₂CO₃ gave the iodo derivatives (CF₃)₃CCF = CFI and C₄F₉OCF = CFI.     

Synthesis, structure and reactions of organometallic compounds of Groups 1–3 containing bulky silicon-substituted alkyl groups

Complexes trans-[PtX(L)(PPh₃)₂]A [1: X = CF₃; A = BF₄; L = NCNH₂, NCNMe₂, NCNEt₂, or NCNC(NH₂)₂. 2: X = Cl; A = BPh₄; L = NCNMe₂ or NCNEt₂] and cis-[PtCl(L)(PPh₃)₂][BPh₄] [3: L = NCNH₂ or NCNC(NH₂)₂], which appear to be the first cyanamide or cyanoguanidine complexes of platinum to be reported, have been prepared by treatment of trans-[PtBr(CF₃)(PPh₃)₂] (in CH₂Cl₂/acetone and in the presence of Ag[BF₄]) or of cis-[PtCl₂(PPh₃)₂] (in THF and in the presence of Na[BPh₄]), respectively, with the appropriate substrate. In KBr pellets or in solution 1 (L = NCNMe₂ or NCNEt₂) undergoes ready replacement of the organocyanamide (under the trans influence of CF₃) by bromide to regenerate trans-(PtBr(CF₃)(PPh₃)₂]. The X-ray structure of 1 (X = CF₃, A = BF₄, L = NCNEt₂) is also reported, and shows the presence of two apical intramolecular contacts of the metal with two ortho-hydrogen atoms of the phosphines, whereas the amine N atom of the diethylcyanamide is trigonal planar in the linear NCN framework with a delocalized π system.     

Synthesis, electrochemistry and structural characterization of luminescent rhenium(I) monoynyl complexes and their homo- and hetero-metallic binuclear complexes

A series of luminescent rhenium(I) monoynyl complexes, [Re(N---N)(CO)₃(CC---R)] (N---N=bpy, ^tBu₂bpy; R=C₆H₅, C₆H₄---Cl-4, C₆H₄---OCH₃-4, C₆H₄---C₈H₁₇-4, C₆H₄---C₆H₅, C₈H₁₇, C₄H₃S, C₄H₂S---C₄H₃S, C₅H₄N), together with their homo- and hetero-metallic binuclear complexes, {Re(N---N)(CO)₃(CC---C₅H₄N)[M]} (N---N=bpy, ^tBu₂bpy; [M]=[Re{(CF₃)₂-bpy}(CO)₃]ClO₄, [Re(NO₂-phen)(CO)₃]ClO₄, W(CO)₅) have been synthesized and their electrochemical and photoluminescence behaviors determined. The structural characterization and electronic structures of selected complexes have also been studied. The luminescence origin of the rhenium(I) alkynyl complexes has been assigned as derived states of a [dπ(Re)→π*(N---N)] metal-to-ligand charge transfer (MLCT) origin mixed with a [π(CCR)→π*(N---N)] ligand-to-ligand charge transfer (LLCT) character. The assignments are further supported by extended Hückel molecular orbital (EHMO) calculations, which show that the LUMO mainly consists of π*(N---N) character while the HOMO is dominated by the antibonding character of the Re---CCR moiety resulted from the overlap of the dπ(Re) and π(CCR) orbitals.     

Vibrational frequencies and structural determination of 1,1-difluoro-1,2-propadiene

The normal mode frequencies and corresponding vibrational assignments of 1,1-difluoro-1,2-propadiene in C_2v symmetry are examined theoretically using the 98 set of quantum chemistry codes. All normal modes were successfully assigned to one of 11 types of motion (C=C stretch, C–H stretch, C–F stretch, CH₂ scissors, CF₂ scissors, CH₂ wag, CF₂ wag, CH₂ rock, CF₂ rock, CF₂ twist, and C=C=C bend) predicted by a group theoretical analysis. Comparing the vibrational frequencies with IR and Raman spectra available in the literature, a set of scaling factors is derived. Predicted infrared intensities and Raman activities are reported. Predicted normal mode frequencies of 1,1-difluoro-1,2-propadiene-d₂ are reported.     

Silane-induced ring-opening polymerization of 1,1,3,3-tetramethyl-2-oxa-1,3-disilacyclopentane catalyzed by a triruthenium cluster

The silane-induced ring-opening polymerization of a cyclic siloxane, 1,1,3,3-tetramethyl-2-oxa-1,3-disilacyclopentane (2), is catalyzed by a ruthenium cluster, (μ₃,η²:η³:η⁵-acenapthylene)Ru₃(CO)₇ (1), to give poly(tetramethylsilethylenesiloxane) with M_n=6300–780,000 and M_w/M_n=1.5–3.0. The molecular weight of the polymer can be controlled by changing the concentration of the monomer solution. Addition of acetone results in formation of the polymer with M_n=4400, spectroscopic analysis of which reveals existence of a siloxy and an isopropoxy moieties at the end group.