The Addition of tert-Butyl (Me3Ċ) and (tert-Butoxy)carbonylmethyl (Me3CO2CĊH2) radicals to alkynes in solution studied by ESR spectroscopy

Absolute rate constants and their temperature dependence are determined by time-resolved electron spin resonance for the addition of Me₃? to 20 and of Me₃CO₂C?H₂ to six mono- and disubstituted alkynes in solution. For Me₃? the rate constants show polar alkyne-substituent effects which are, however, weaker than for the corresponding alkenes. For Me₃CO₂?H₂, the rate constants do not vary strongly with alkyne substitution and probably increase with increasing reaction exothermicity. Both radicals react generally slower with alkynes than with alkenes which is discussed in terms of the state correlations. Several vinyl-type radical adducts of Me₃? to alkenes are characterized by electron spin resonance, and their spectral data indicate linear or bent configurations of the radical carbon depending on the substitution.     

Spectroscopic calculations for the (CH3)3N · BF3 and (CH3)3N · BCL3 complexes

Mean amplitudes of vibration and perpendicular amplitude correction coefficients are calculated for (CH₃)₃N · BF₃ and (CH₃)₃N · BCl₃ complexes using different versions of force fields originating from spectroscopic studies with somewhat different assignments. The results are discussed in conjunction with the electron diffraction results and bonding features.     

Kristallstruktur und Schwingungsspektrum von (H2NPPh3)2[SnCl6]·2CH3CN

Crystal Structure and Vibrational Spectrum of (H₂NPPh₃)₂[SnCl₆]·2CH₃CN Single crystals of (H₂NPPh₃)₂[SnCl₆]·2CH₃CN ( 1 ) were obtained by oxidative addition of tin(II) chloride with N‐chloro‐triphenylphosphanimine in acetonitrile in the presence of water. 1 is characterized by IR and Raman spectroscopy as well as by a single crystal structure determination: Space group , Z = 2, lattice dimensions at 193 K: a = 1029.6(1), b = 1441.0(2), c = 1446.1(2) pm, α = 90.91(1)°, β = 92.21(1)°, γ = 92.98(1)°, R₁ = 0.0332. 1 forms an ionic structure with two different site positions of the [SnCl₆]^2? ions. One of them is surrounded by four N‐hydrogen atoms of four (H₂NPPh₃)⁺ ions, four CH₃CN molecules form N–H···N≡C–CH₃ contacts with the other four N‐hydrogen atoms of the cations. Thus, 1 can be written as [(H₂NPPh₃)₄(CH₃CN)₄(SnCl₆)]²⁺[SnCl₆]^2?.     

Substituent effects on the disproportionation‐combination rate constant ratios for gas‐phase halocarbon radicals. IV. Reactions of ·CF3 + CF3CH2CF2· and CF3CH2CF2· + CF3CH2CF2·

Rate constant ratios, k_d/k_c, for the disproportionation/combination reaction at a temperature of 295 ± 2 K, have been measured as 0.034 ± 0.009 for the collision between CF₃CH₂CF₂ + CF₃ radicals and as 0.075 ± 0.019 for CF₃CH₂CF₂ + CF₃CH₂CF₂ radicals. The effect of the two fluorine substituents on the rate constant ratio is compared to previous k_d/k_cs with CF₃CH₂CH₂, CF₃CH₂CHCl, and CF₃CH₂CHCF₃ radicals. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet: 31: 237–243, 1999     

Attempted Abstraction of the Halogenides in (HNEt3)[Re(CH3CN)2Cl4] and Crystal Structures of cis‐[Re(CH3CN)2Cl4]·CH3CN and cis‐[Re(NHC(OCH3)CH3)2Cl4]

The abstraction of the halogenide ligands in [Re(CH₃CN)₂Cl₄]^? should result in a solvent‐only stabilized Re^III complex. The reactions of salts of [Re(CH₃CN)₂Cl₄]^? with silver(I) and thallium(I) salts were investigated and the solid‐state structures of cis‐[Re(CH₃CN)₂Cl₄]·CH₃CN and cis‐[Re(NHC(OCH₃)CH₃)₂Cl₄] are described.     

Phosphaniminato-Komplexe des Antimons. Die Kristallstrukturen von [Sb2Cl5(NPMe3)2][SbCl6] · CH3CN und [SbCl(NPPh3)]2[SbCl6]2 · 6 CH3CN

Phosphorane Iminato Complexes of Antimony. The Crystal Structures of [Sb₂Cl₅(NPMe₃)₂][SbCl₆] · CH₃CN and [SbCl(NPPh₃)]₂[SbCl₆]₂ · 6 CH₃CN The title compounds are formed by reaction of antimony pentachloride in acetonitrile solution with the phosphorane iminato complexes SbCl₂(NPMe₃) and SbCl₂(NPPh₃), respectively, which themselves are synthesized by reaction of antimony trichloride with Me₃SiNPR₃ (R = Me, Ph). The complexionic compounds are characterized by ¹²¹Sb Mössbauer spectroscopy and by crystal structure determinations. [Sb₂Cl₅(NPMe₃)₂][SbCl₆] · CH₃CN: Space group P4₁, Z = 4, 3 698 observed unique reflections, R = 0.022. Lattice dimensions at ?60°C: a = b = 1 056.0(1), c = 2 709.6(2) pm. The structure consists of SbCl₆^? ions and cations [Sb₂Cl₅(NPMe₃)₂(CH₃CN)]⁺, in which one Sb^III atom and one Sb^V atom are bridged by the N atoms of the phosphorane iminato ligands. [SbCl(NPPh₃)]₂[SbCl₆]₂ · 6 CH₃CN: Space group P1 , Z = 2, 5 958 observed unique reflections, R = 0.033. Lattice dimensions at ?60°C: a = 989.4(11), b = 1 273(1), c = 1 396(1) pm, α = 78.33(7), β = 77.27(8)°, γ = 86.62(8)°. The structure consists of SbCl₆^? ions and centrosymmetric cations [SbCl(NPPh₃)(CH₃CN)₂]₂²⁺, in which the antimony atoms are bridged by the N atoms of the phosphorane iminato ligands.     

Tetrakis(acetonitrile)‐dibromo‐nickel(II)‐di‐acetonitrile, [Ni(CH3CN)4Br2]·2CH3CN

[Tetrakis(acetonitrile)‐dibromo‐nickel(II)]‐di‐acetonitrile was obtained from a solution of nickel(II) dibromide in acetonitrile at 258 K. The crystal structure [monoclinic, P2₁/n (no.14), a = 1005.5(5), b = 831.3(5) , c = 1131.7(5) pm, β = 106.263(5)°, V = 908.1(8)·10⁶ pm³, Z = 2, R₁ for 1580 reflections with I₀>2σ(I₀): 0.0505] contains sixfold coordinated Ni^II atoms. Two trans coordinating bromide anions and four equatorial acetonitrile molecules form an elongated octahedron around the central Ni^II atom. [Ni(CH₃CN)₄Br₂] octahedra are connected via hydrogen bonds to neighboring octahedra as well as to solvate acetonitrile molecules.     

Theoretical study of stabling function of the NO to the (CH3)3CO · radical

The stabling function of the NO to the (CH₃)₃CO · radical has been theoretically investigated. Density functional theory (DFT) calculations are performed to optimize the geometries of relevant species. The single‐point energy is evaluated at CCSD(T)/6‐31++G** level. Three reaction channels of (CH₃)₃CO · + NO in the singlet state are considered. The calculations indicate that NO is a stable reagent of active radical (CH₃)₃CO. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

Mn3(OAc)6·CH3CN: a porous dehydrated manganese(II) acetate

The crystal structure of a new form of dehydrated manganese(II) acetate, poly[[hexa‐μ₃‐acetato‐trimanganese(II)] acetonitrile solvate], {[Mn₃(CH₃COO)₆]·CH₃CN}_n, (I), reveals a three‐dimensional polymeric structure based on an {Mn₃} trimer. The {Mn₃} asymmetric unit contains three crystallographically independent Mn positions, comprising a seven‐coordinate center sharing a mirror plane with a six‐coordinate center, and another six‐coordinate atom located on an inversion center. Two of the four crystallographically independent acetate (OAc) ligands, as well as the acetonitrile solvent molecule, are also located on the mirror plane. The Mn atoms are connected by a mixture of Mn—O—Mn and Mn—OCO—Mn bridging modes, giving rise to face‐ and corner‐sharing interactions between manganese polyhedra within the trimers, and edge‐ and corner‐sharing connections between the trimers. The network contains substantial pores which are tightly filled by crystallographically located acetonitrile molecules. This structure represents the first porous structurally characterized phase of anhydrous manganese(II) acetate and as such it is compared with the closely related densely packed anhydrous manganese(II) acetate phase, solvent‐free β‐Mn(OAc)₂.     

Nature of MoH···I bonds in Cp2Mo(L)H···I‐C≡C‐R Complexes (L=H,CN, PPh2, C(CH3)3; R=NO2, Cl,Br, H,OH, CH3, NH2)

The nature of the MoH···I bond in Cp₂Mo(L)H···I‐C≡C‐R (L= H, CN, PPh₂, C(CH₃)₃; R=NO₂, Cl, Br, H, OH, CH₃, NH₂) was investigated using electrostatic potential analysis, topological analysis of the electron density, energy decomposition analysis and natural bond orbital analysis. The calculated results show that MoH···I interactions in the title complexes belong to halogen‐hydride bond, which is similar to halogen bonds, not hydrogen bonds. Different to the classical halogen bonds, the directionality of MoH···I bond is low; Although electrostatic interaction is dorminant, the orbital interactions also play important roles in this kind of halogen bond, and steric interactions are weak; the strength of H···I bond can tuned by the most positive electrostatic potential of the I atom. As the electron‐withdrawing ability of the R substituent in the alkyne increases, the electrostatic potential maximum of the I atom increases, which enhances the strength of the H···I halogen bond, as well as the electron transfer.     

Darstellung und Kristallstruktur der Addukte [DB-18C6] · CH3CN · CH3CSOH und [DC-18C6](CH3CSOH)2 sowie der salzartigen Verbindungen [Cs(B-15C5)2]CH3CSS und [Cs(DB-18C6)]2S5(DMF)21)

Synthesis and Crystal Structure of the Adducts [DB-18C6] · CH₃CN · CH₃CSOH and [DC-18C6](CH₃CSOH)₂ as well as of the Salt-like Compounds [Cs(B-15C5)₂]CH₃CSS and [Cs(DB-18C6)]₂S₅(DMF)₂¹) The reaction products of crown ethers, cesium, and sulfur in aprotic solvents like acetonitrile and dimethylformamide strongly depend on the reaction conditions. Using CH₃CN as a solvent, sometimes neutral host-guest adducts crystallize only, e.g., [dibenzo-18C6] · CH₃CN · CH₃CSOH (monoclinic, S. G. P2₁/c, Z = 4, a = 9.73(1) Å, b = 22.03(1) Å, c = 11.86(1) Å, β = 91.8(1)°) or [dicyclohexyl-18C6](CH₃CSOH)₂ (monoclinic, S. G. P2₁/n, Z = 2, a = 7.75(1) Å, b = 10.32(1) Å, c = 17.73(1) Å, β = 95.7(1)°). The monothioacetic acid, CH₃CSOH, must be regarded as the first product of the hydrolysis of CH₃CN. Furthermore, another product of this kind of hydrolysis, CH₃CSSH, is obtained too. Therefore, we also obtain the salt-like compound [Cs(benzo-15C5)₂]CH₃CSS (monoclinic, S. G. C2/c, Z = 4, a = 16.05(1) Å, b = 16.73(1) Å, c = 13.11(1) Å, β = 106.3(1)°). If the solvent DMF is used, the pentasulfide [Cs(dibenzo-18C6)]₂S₅(DMF)₂ crystallizes (monoclinic, S. G. P2₁/n, Z = 4, a = 14.79(1) Å, b = 14.24(1) Å, c = 25.74(1) Å, β = 92.7(1°. The S₅^2? anions show the cis-conformation.     

Thermal decomposition of di-t-butyl peroxide in the presence of (CH3)2CCH2: Reactions of CH3, (CH3)2ĊCH2CH3, and (CH3)2ĊCH2C(CH3)2CH2CH3 radicals

A study of the reaction initiated by the thermal decomposition of di-t-butyl peroxide (DTBP) in the presence of (CH₃)₂C?CH₂ (B) at 391–444 K has yielded kinetic data on a number of reactions involving CH₃ (M·), (CH₃)₂CCH₂CH₃ (MB·) and (CH₃)₂?CH₂C(CH₃)₂CH₂CH₃ (MBB·) radicals. The cross-combination ratio for M· and MB· radicals, rate constants for the addition to B of M· and MB· radicals relative to those for their recombination reactions, and rate constants for the decomposition of DTBP, have been determined. The values are, respectively, where θ = RT ln 10 and the units are dm^3/2 mol^?1/2 s^?1/2 for k₂/k and k₉/k, s^?1 for k₀, and kJ mol^?1 for E. Various disproportionation-combination ratios involving M·, MB·, and MBB· radicals have been evaluated. The values obtained are: Δ₁(M·, MB·) = 0.79 ± 0.35, Δ₁(MB·, MB·) = 3.0 ± 1.0, Δ₁(MBB·, MB·) = 0.7 ± 0.4, Δ₁(M·, MBB·) = 4.1 ± 1.0, Δ₁(MB·, MBB·) = 6.2 ± 1.4, and Δ₁(MBB·, MBB·) = 3.9 ± 2.3, where Δ₁ refers to H-abstraction from the CH₃ group adjacent to the center of the second radical, yielding a 1-olefin. © 1994 John Wiley & Sons, Inc.     

Synthese und Kristallstruktur von [ReNCl(NPPh2C6H4)]2 · [Ph3PNH2]Cl · CH3CN,einem rheniumorganischen Nitrido-Phosphaniminato-Komplex

Synthesis and Crystal Structure of [ReNCl(NPPh₂C₆H₄)]₂ · [Ph₃PNH₂]Cl · CH₃CN, a Rhenium Organic Nitrido Phosphoraneiminato Complex The title compound is synthesized by the reaction of ReNCl₄ with Me₃SiNPPh₃ in boiling acetonitrile, forming colourless crystals, which are characterized by an X-ray structure determination. Space group P1 , Z = 2, 4 037 observed unique reflections, R = 0.043. Lattice dimensions at 19°C: a = 1 005.5; b = 1 695.2; c = 1 744.7 pm, α = 105.86°; β = 101.49°; γ = 104.45°. The structure consists of dimeric molecules [ReNCl(NPPh₂C₆H₄)]₂, triphenylphosphorane ammoniumchloride and included acetonitrile molecules. In the nitrido phosphoraneiminato complex the rhenium atoms are μ₂-bridged via the N-Atoms of the phosphoraneiminato ligands. Because of this bridging and a Re? Re bond, one terminal nitrido ligand, one terminal chloro ligand, and a Re? C bond of an -C-atom of one phenylene group of Re-atoms attain co-ordination number six.     

Difluoromethylation of Amines with Zn(CF3)Br · 2 CH3CN,Cd(CF3)2 · 2 CH3CN and the System Bi(CF3)3/AlCl3

The reactions of Zn(CF₃)Br · 2 CH₃CN, Cd(CF₃)₂ · 2 CH₃CN or Bi(CF₃)₃/AlCl₃ with tertiary amines lead to the formation of quaternary ammonium salts of the general formula [R₃NCF₂H]X. The reaction of 4‐N,N‐dimethylaminopyridine with Zn(CF₃)Br · 2 CH₃CN yields (N‐difluoromethyl)‐4‐N,N‐dimethylaminopyridinium bromide. Bi(CF₃)₃/AlCl₃ reacts with 1,4‐diazabicyclo[2.2.2]octane to form a mixture of mono‐ and bis(difluoromethylammonium) salts.     

Formation of· CH2CH2CO + and C2H6+· in the metastable decompositions of ionized ethyl formate

The products of the metastable decompositions of ionized ethyl formate (a) are characterized. The loss of water from a produces ^·CH₂CH₂CO⁺, a rarely reported product. Loss of H appears to produce CH₂=CHC(OH). The third decomposition is an unusual formation of C₂H. This work demonstrates that a previous supposition that isomerization to different intermediates is involved in the losses of ethene and of water from a is correct.     

Absolute rate constants for the addition of hydroxymethyl radicals to alkenes in methanol solution

Absolute rate constants and their temperature dependencies were determined for the addition of hydroxymethyl radicals (CH₂OH) to 20 mono- or 1,1-disubstituted alkenes (CH₂ = CXY) in methanol by time-resolved electron spin resonance spectroscopy. With the alkene substituents the rate constants at 298 K (k₂₉₈) vary from 180 M^?1s^?1 (ethyl vinylether) to 2.1 middot; 10⁶ M^?1s^?1 (acrolein). The frequency factors obey log A/M^?1s^?1 = 8.1 ± 0.1, whereas the activation energies (E_a) range from 11.6 kJ/mol (methacrylonitrile) to 35.7 kJ/mol (ethyl vinylether). As shown by good correlations with the alkene electron affinities (EA), log k₂₉₈/M^?1s^?1 = 5.57 + 1.53 · EA/eV (R² = 0.820) and E_a = 15.86 ? 7.38 · EA/eV (R² = 0.773), hydroxymethyl is a nucleophilic radical, and its addition rates are strongly influenced by polar effects. No apparent correlation was found between E_a or log k₂₉₈ with the overall reaction enthalpy. © 1995 John Wiley & Sons, Inc.     

Synthesis,Vibrational Spectrum and Structure of the Tetracyanoborate K[B(CN)4]·CH3CN

The new tetracyanoborate K[B(CN)₄]·CH₃CN was synthesized by dissolution of the solvent‐free K[B(CN)₄] in acetonitrile and subsequent careful crystallization. The crystal structure has been determined by single‐crystal X‐ray diffraction. It crystallizes in the orthorhombic space group P2₁2₁2₁ with Z = 4. Some comparisons with related structures are made, and the vibrational spectrum is discussed.     

A Novel 3‐D Heterobimetallic Cyano‐bridged Coordination Polymer Incorporating Ag···Ag Interaction: [Cu(dien)Ag(CN)2]2[Ag2(CN)3][Ag(CN)2]

A three‐dimensional cyano‐bridged copper(II) complex, [Cu(dien)Ag(CN)₂]₂[Ag₂(CN)₃][Ag(CN)₂] ( 1 ) (dien = diethylenetriamine), has been prepared and characterized by X‐ray crystallography. Complex 1 crystallized in the monoclinic space group P2₁/n with a = 6.988(2), b = 17.615(6), c = 12.564(4) Å, β = 90.790(5)°. The crystal consists of cis‐[Cu(dien)]²⁺ units bridged by [Ag(CN)₂]^— to form a zig‐zag chain. The Ag atoms of the free and bridging [Ag(CN)₂]^— link together to form additional infinite zig‐zag chains with short Ag···Ag distances. The presence of Ag···Ag interactions effectively increases the dimensionality from a 1‐D chain to a 3‐D coordination polymer.     

Synthese,Schwingungsspektren und Kristallstrukturen der Nitratoargentate (Ph4P)[Ag(NO3)2(CH3CN)]·CH3CN und (Ph4P)[Ag2(NO3)3]

Synthesis, Vibrational Spectra, and Crystal Structures of the Nitrato Argentates (Ph₄P)[Ag(NO₃)₂(CH₃CN)]·CH₃CN and (Ph₄P)[Ag₂(NO₃)₃] Tetraphenylphosphonium bromide reacts in acetonitril suspension with excess silver nitrate to give (Ph₄P)[Ag(NO₃)₂(CH₃CN)]·CH₃CN ( 1 ), whereas (Ph₄P)[Ag₂(NO₃)₃] ( 2 ) is obtained in a long‐time reaction from (Ph₄P)Br and excess AgNO₃ in dichloromethane suspension. Both complexes were characterized by vibrational spectroscopy (IR, Raman) and by single crystal structure determinations. 1 : Space group P2₁/c, Z = 4, lattice dimensions at 193 K: a = 1781.5(3), b = 724.8(1), c = 2224.2(3) pm, β = 96.83(1)°, R₁ = 0.0348. 1 contains isolated complex units [Ag(NO₃)₂(CH₃CN)]^?, in which the silver atom is coordinated by the chelating nitrate groups and by the nitrogen atom of the solvated CH₃CN molecule with a short Ag—N distance of 220.7(4) pm. 2 : Space group I2, Z = 4, lattice dimensions at 193 K: a = 1753.4(4), b = 701.7(1), c = 2105.5(4) pm, R₁ = 0.072. In the polymeric anions [Ag₂(NO₃)₃]^? each silver atom is coordinated in a chelating manner by one nitrate group and by two oxygen atoms of two bridging nitrate ions. In addition, each silver atom forms a weak π‐bonding contact with a phenyl group of the (Ph₄P)⁺ ions with shortest Ag···C separations of 266 and 299 pm, respectively, indicating a (4+1) coordination of silver atoms.     

Mechanism and Rate Constants of the CH3+ CH2CO Reaction: A Theoretical Study

The mechanism of the reaction of ketene with methyl radical has been studied by ab initio CCSD(T)‐F12/cc‐pVQZ‐f12//B2PLYPD3/6‐311G** calculations of the potential energy surface. Temperature‐ and pressure‐dependent reaction rate constants have been computed using the Rice–Ramsperger–Kassel–Marcus (RRKM)–Master Equation and transition state theory methods. Three main channels have been shown to dominate the reaction; the formation of the collisionally stabilized CH₃COCH₂ radical and the production of the C₂H₅ + CO and HCCO + CH₄ bimolecular products. Relative contributions of the CH₃COCH₂, C₂H₅ + CO, and HCCO + CH₄ channels strongly depend on the reaction conditions; the formation of thermalized CH₃COCH₂ is favored at low temperatures and high pressures, HCCO + CH₄ is dominant at high temperatures, whereas the yield of C₂H₅ + CO peaks at intermediate temperatures around 1000 K. The C₂H₅ + CO channel is favored by a decrease in pressure but remains the second most important reaction pathway after HCCO + CH₄ under typical flame conditions. The calculated rate constants at different pressures are proposed for kinetic modeling of ketene reactions in combustion in the form of modified Arrhenius expressions. Only rate constant to form CH₃COCH₂ depends on pressure, whereas those to produce C₂H₅ + CO and HCCO + CH₄ appeared to be pressure independent.