Reaction between [MgCl2(THF)2] and [MoOCl3(THF)2]. The Crystal Structures of [Mg(THF)6][MoOCl4THF]2 and [Mg2(m̈-Cl)3(THF)6][MoOCl4THF]

Two [MoOCl₃(THF)₂] molecules are used for detachment of two Cl atoms from [MgCl₂(THF)₂]. In such reaction a green crystalline salt [Mg(THF)₆][MoOCl₄THF]₂ IV is formed. Compound IV reacts further with 3 equivalents of bis(tetrahydrofuran)magnesium dichloride, yielding a green ionic [Mg₂(m?-Cl)₃(THF)₆][MoOCl₄THF] compound V . Compound IV and V vary only in a structure of cation what indicated that the tri-m?-chlorohexakis(tetrahydrofuran)dimagnesium(II) cation in V is really formed in reaction between [Mg(THF)₆]²⁺ cation and [MgCl₂(THF)₂]. The crystal structure of compounds IV and V has been solved by X-ray diffraction method. The [Mg(THF)₆]²⁺ cation forms the tetragonally distorted octahedron with the magnesium atom in the symmetry centre. In homobimetallic di-octahedral [Mg₂(m?-Cl)₃(THF)₆]⁺ cation the magnesium atoms are surrounded by three bridging chlorine atoms and three THF molecules. The structures of [MoOCl₄THF]^? in IV and V are similar. In those anions the molybdenum atom is hexacoordinated with four chlorine atoms in equatorial plane.     

Synthesis and structure of the silylated benzene radical anion salts [K([18]crown-6){C6H4(SiMe3)2-1,4}] and [K([18]crown-6)(THF)2][C6H2(SiMe3)4-1,2,4,5]

The crystalline compound [K([18]crown-6){C₆H₄(SiMe₃)₂-1,4}] (1) was prepared by the low-temperature reduction of the para-disilylated benzene with K/[18]crown-6 in toluene followed by recrystallisation from the same solvent. Reduction of 1,2,4,5-tetrasilylated benzene with 2(K/[18]crown-6) in toluene produced a hydrocarbon-insoluble powder identified as the dianionic derivative [K([18]crown-6)]₂[C₆H₂(SiMe₃)₄-1,2,4,5)] (2), which upon crystallisation from THF/Et₂O yielded [K([18]crown-6)(THF)₂][C₆H₂(SiMe₃)₄-1,2,4,5] (3). An X-ray diffraction study revealed that 1 comprised a contact ion pair with the crown-encapsulated K cation η⁵-connected to the planar ring of the substituted benzene radical anion, while 3 contained a well separated cation and anion.     

Reaction of thianthrene cation radical with grignard reagents : Evidence for electron transfer and trapping of alkyl radicals by the thianthrene cation radical

Reactions are reported between RMgCl and thianthrene cation radical perchlorate (Th^.+ClO^-₄) suspended in ether and tetrahydrofuran (THF). In ether solution reactions R = Bu, s-Bu, t-Bu, 5-hexenyl, and cyclopentylmethyl. Major products were the alkane, the alkene R(-H) in some cases, and, in the cases of R = Bu, 5-hexenyl, and cyclopentylmethyl, the 5-alkylthianthrenium perchlorate (ThR⁺ClO^-₄). When 5-hexenylMgCl was used a mixture of 5-(5-hexenyl)- and 5-(cyclopentylmethyl)thianthrenium per-chlorates in the ratio of approximately 2 was obtained. Since the ratio of 5-hexenyl/cyclopentylmethyl in the Grignard reagent was 10.4, it is concluded that the C₆ sulfonium ions were formed by radical trapping by Th^.+ after single electron transfer from Grignard to cation radical had occurred, thus allowing for cyclization of 5-hexenyl radical. Formation of ThBu⁺ClO^-₄ is attributed to the trapping of butyl radical by Th^·+, while formation of RH and R(-H) is in all cases also attributed to alkyl radical reactions. Reactions in THF(R = Me, i-Pr, Bu, s-Bu, t-Bu, Ph) led almost exclusively to RH and Th. Polymerization of THF was also initiated and took place slowly giving rise to low molecular weight poly(THF). By using THF-d₈, as solvent for reaction between BuMgCl and Th^.+, it was possible to find Bu groups (¹H-NMR) in the poly(THF-d₈). Polymerization of THF is attributed, in some cases (R = Me, Bu), to alkyl-cation transfer from ThR⁺ to THF. In other cases initiation of polymerization by R⁺ and THF(-H)⁺ is considered.     

Polymerization by alkaline earth metal compounds—II Polymerization of 2- and 4-vinylpyridine,styrene and butadiene by triphenylmethyl derivatives of calcium,strontium and barium

Investigations are reported on polymerizations of 2- and 4- vinylpyridine, styrene and butadiene by a series of related alkaline earth metal initiators, Ph₃CMX(THF)_n (M = Ca, Ba, X = Cl, n = 2; M = Ca, X = Br, n = 4; M = Sr, X = Cl, n = 4; M = Sr, X = Br, n = 5) in tetrahydrofuran (THF) or 1,2-dimethoxyethane (DME) at various temperatures and in the absence of solvent. The polymers have been examined by GPC and aspects of their microstructures determined by ¹³C and/or ¹H NMR spectroscopy and, for polybutadiene, i.r. spectroscopy. Poly-2-vinylpyridine produced by Ph₃CMX(THF)_n is rich in isotactic content; the isotacticity is higher for polymer formed in THF than DME solution, falls with change of initiator in the order M = Ca > Sr > Ba and, in DME, is greater when X = Br. The tacticities of poly-4-vinylpyridine and polystyrene are similar to those obtained from related organometallic initiators. The 1,4-content of polybutadiene decreases with initiator Ph₃CMX(THF)_n in the order M = Ba > Sr > Ca; the trans-1,4 structure generally predominates except when M = Ba from which cis-1,4 links are formed in comparable amounts.     

An Unusual Product from the Reaction of C(PPh3)2 with [Mn2(CO)10]: Formation and Crystal Structure of [Mn(OPPh3)2{O2CC(PPh3)2}2][Mn(CO)5]2

The carbodiphosphorane C(PPh₃)₂ ( 1 ) reacts with [Mn₂(CO)₁₀] in THF to produce quantitatively the salt‐like complex (HC{PPh₃}₂)[Mn(CO)₅] ( 2 ) as THF solvate. If the reaction is carried out in 1,2‐dimethoxyethane (DME) small amounts of [Mn(OPPh₃)₂{O₂CC(PPh₃)₂}₂][Mn(CO)₅]₂ ( 3 ) as DME solvate along with solvent free 2 as the main product were isolated. Proton abstraction from the solvent led to the formation of 2 ; the ligands OPPh₃ and O₂CC(PPh₃)₂}₂ of 3 are the results of a side reaction from [Mn₂(CO)₁₀] and 1 in a Wittig type manner. From the reaction in benzene small amounts of 3 were also obtained, crystallizing as benzene solvate 3· 4C₆H₆. The crystal structures of 2· THF, 2 , 3· 1.75DME and 3· 4C₆H₆ are reported. The compounds are further characterized by IR and ³¹P NMR spectroscopy.     

Indenyl and fluorenyl transition metal complexes : V. Study of reversible isomerization of η6- and η5-fluorenylchromium tricarbonyl anions by IR and PMR spectroscopy

IR and PMR spectroscopy was used to study the reversible isomerization of η⁶- and η⁵-fluorenylchromium tricarbonyl anions (I and II, respectively) in solutions. Consideration was given to the dependence of the equilibrium position and nature of the resulting particles on the type of cation (Li⁺, Na⁺, K⁺, Ph₃PCH₃⁺, n-Bu₄N⁺), the solvent and the presence of solvating cation additives (dicyclohexyl-18-crown-6 (IV), DMSO). The η⁵-isomer exists in THF solution as an equilibrium mixture of solvent-separated and contact ion pairs (SSIP and CIP, respectively), the cation in the latter being located near the oxygen atom of one of the carbonyl groups. The existence of such an equilibrium is also shown for the salts of the C₅H₅(CO)₃Cr^? anion. The dependence of the equilibrium constants for I ? II on the above factors was determined. For the K salt in THF solution at 28°C both IR and PMR spectroscopy gave fairly coincident values of K_eq equal to 7.15 and 7.35, respectively. IR spectroscopy was applied to the kinetic studies of the reversible isomerization of K salts of I and II at 0—28°C with and without crown ether IV. The process is shown to be entropy controlled. The equilibrium position is governed by the type of cation, the degree of its solvation and the temperature. The factors promoting the formation of SSIP's lead to the equilibrium being shifted towards I.     

Isolation and Characterization,Including by X‐ray Crystallography,of Contact and Solvent‐Separated Ion Pairs of Silenyl Lithium Species

Reaction of bromoacylsilane 1 (pink solution) with tBu₂MeSiLi (3.5 equiv) in a 4:1 hexane:THF solvent mixture at ?78 °C to room temperature yields the solvent separated ion pair (SSIP) of silenyl lithium E‐[(tBuMe₂Si)(tBu₂MeSi)C=Si(SiMetBu₂)]^? [Li?4THF]⁺ 2 a (green–blue solution). Removal of the solvent and addition of benzene converts 2 a into the corresponding contact ion pair (CIP) 2 b (violet–red solution) with two THF molecules bonded to the lithium atom. The 2 a ? 2 b interconversion is reversible upon THF? benzene solvent change. Both 2 a and 2 b were characterized by X‐ray crystallography, NMR and UV/Vis spectroscopy, and theoretical calculations. The degree of dissociation of the Si?Li bond has a large effect on the visible spectrum (and thus color) and on the silenylic ²⁹Si NMR chemical shift, but a small effect on the molecular structure. This is the first report of the X‐ray molecular structure of both the SSIP and the CIP of any R₂E=E′RM species (E=C, Si; E′=C, Si; M=metal).     

Isolation and Characterization,Including by X‐ray Crystallography,of Contact and Solvent‐Separated Ion Pairs of Silenyl Lithium Species

Reaction of bromoacylsilane 1 (pink solution) with tBu₂MeSiLi (3.5 equiv) in a 4:1 hexane:THF solvent mixture at −78 °C to room temperature yields the solvent separated ion pair (SSIP) of silenyl lithium E‐[(tBuMe₂Si)(tBu₂MeSi)C=Si(SiMetBu₂)]⁻ [Li⋅4THF]⁺ 2 a (green–blue solution). Removal of the solvent and addition of benzene converts 2 a into the corresponding contact ion pair (CIP) 2 b (violet–red solution) with two THF molecules bonded to the lithium atom. The 2 a ⇌ 2 b interconversion is reversible upon THF⇌ benzene solvent change. Both 2 a and 2 b were characterized by X‐ray crystallography, NMR and UV/Vis spectroscopy, and theoretical calculations. The degree of dissociation of the Si−Li bond has a large effect on the visible spectrum (and thus color) and on the silenylic ²⁹Si NMR chemical shift, but a small effect on the molecular structure. This is the first report of the X‐ray molecular structure of both the SSIP and the CIP of any R₂E=E′RM species (E=C, Si; E′=C, Si; M=metal).     

Decamethyl­ferrocenium bis­(2‐oxo‐1,3‐dithiole‐4,5‐dithiolato‐κ2S4,S5)nickelate(III) tetra­hydro­furan solvate

The title compound, [Fe(C₁₀H₁₅)₂][Ni(C₃OS₄)₂]·C₄H₈O or [Fe(Cp*)₂][Ni(dmio)₂]·THF, where [Fe(Cp*)₂]⁺ is the deca­methyl­ferrocenium cation, dmio is the 2‐oxo‐1,3‐dithiole‐4,5‐dithiol­ate dianion and THF is tetra­hydro­furan, crystallizes with two independent half‐anion units [one Ni atom is at the centre of symmetry (, , 0) and the other is at the centre of symmetry (, 0, )], one cation unit (located in a general position) and one THF solvent mol­ecule in the asymmetric unit. The crystal structure consists of two‐dimensional layers composed of parallel mixed chains, where pairs of cations alternate with single anions. These layers are separated by sheets of anions and THF mol­ecules.     

Synthesis, structure, and electroconductivity of new radical cation salt [Pd(dddt)2]2GaBr4

A new radical cation salt based on the dithiolate complex Pd(dddt)₂ (dddt=5,6-dihydro-1,4-dithiine-2,3-dithiolate) with the tetrahedral anion [GaBr₄]^? was synthesized. The crystal and molecular structure was determined by XRD analysis. The crystal structure of the salt contains Pd(dddt)₂ cation layers alternating with layers of [GaBr₄]^? anions along thec axis of the unit cell. The cation layers contain stacks of Pd(dddt)₂, with a Pd...Pd distance of 3.011 Å. The electroconductivity of [Pd(dddt)₂]₂GaBr₄, single crystals at room temperature is 0.25 Ohm^?1 cm^?1 and decreases with temperature decrease, the activation energy beingE _a=0.66 eV.     

Dispersion corrected-DFT investigation on the adsorption and selective detection of organic solvent vapors by Cu2(HCOO)4 paddle wheel of metal organic framework

Porous metal organic frameworks (MOFs) has shown large surface area and high micropore volume making it a promising electrode material for sensing devices. Adsorption and electronic sensitivity of copper-based open metal sites paddlewheel (Cu₂(HCOO)₄) towards polar, moderately polar, and non-polar organic solvent vapors (OSVs) were was investigated using density functional theory, employing B3LYP. The most stable adsorption structures were those with the OSVs interacting with the metal node of PW. Based on calculations, the adsorption energy of molecules is in the range of ?7.8 to ?24.8 kcal/mol, ?9.2 to ?25.7 kcal/mol, and ?6.6 to ?10.9 kcal/mol for polar, moderately polar, and non-polar OSVs, respectively. Also sensing activities of PW were studied from three points of view band gap changing, sensing factor, and work function changes. From the standpoint of conductivity changing, Cu-PW has (i) low sensitivity to acetonitrile, acetone, dimethyl formamide, dimethyl ether, benzene, and ethanol; (ii) moderate sensitivity to toluene, and (iii) strong sensitivity to THF detection so that its HOMO/LUMO gap of the PW is significantly decreased from 1.63 to 0.97 eV which may increase the electrical conductivity, sensing factor is 1.4 * 10¹¹, and work function changing is 0.45 eV after THF adsorption. Thus, we suggest that Cu-PW may be used as a highly sensitive/selective and multi-time reusable sensor material for THF detection.     

Study of Kryptofix5 Complexation with La<Superscript>3+</Superscript> Cation in Several Individual and Binary Nonaqueous Solvents Using Conductometric Method

Complexatio of the La³⁺ cation with 1,13-bis(8-quinolyl)-1,4,7,10,13-pentaoxatridecane(Kryptofix5) was studied in pure solvents acetonitrile (AN), methanol (MeOH), nitrobenzene (NB), tetrahydrofuran (THF), methyl acetate (MeOAC) and in various binary solvent mixtures of AN–MeOH, AN–NB, AN–THF, and AN–MeOAC systems at different temperatures using the conductometric method. The stoichiometry of the complex was found to be 1 : 1 (ML). In all cases, the variation of the log kf with composition of the solvent was non-linear. This behavior is probably due to a change in the structure of these binary mixed solvents as the composition of the medium is varied. The stability order of the complex in pure nonaqueous solvents at 25°C increases in the order: AN > THF > MeOAC > MeOH > NB. The values of thermodynamic data (ΔH _c °,ΔS _c °) formation of (Kryptofix5.La)³⁺ complex are definitely solvent dependent.     

The Ylide Adduct SOC2(PPh3)2 as Complex Ligand. Reaction with [Mn2(CO)10] and InCl3; Crystal Structures of [(CO)4Mn(SOC2{PPh3}2)2][Mn(CO)5] and (H2C{PPh3}2)[InCl4]2

The betain‐like SOC₂(PPh₃)₂ ( 1a ) reacts with [Mn₂(CO)₁₀] in THF to produce the salt‐like complex [(CO)₄Mn(SOC₂{PPh₃}₂)₂][Mn(CO)₅] ( 2 ). 1a is bonded via the sulfur atoms which are arranged in trans position in the octahedral environment of the manganese atom. With InCl₃ from CH₂Cl₂ solution the addition product [Cl₃In(SOC₂{PPh₃}₂)] ( 3 ) is obtained along with the salt (H₂C{PPh₃}₂)[InCl₄]₂ ( 4 ), which is the result of proton abstraction from the solvent. The crystal structures of 2· 0.5THF and 4· CH₂Cl₂ are reported. The compounds are further characterized by IR and ³¹P NMR spectroscopy.     

Single-Crystal Structure of the Solvent-Separated Radical Ion Pair [9,10-diphenylanthracene.⊖][Na⊕(THF)6] and its implication for cation solvation

The one-electron transfer to large π-delocalized hydrocarbons provides an interesting possibility to crystallize solvent-separated ion-pair salts containing optimally solvated cations. Accordingly, the reduction of 9,10-diphenylanthracene in aprotic THF solution at a sodium metal mirror allows to grow dark-blue prismatic crystals of its radical anion and sixfold THF-solvated sodium cation. The structure of the radical anion is very similar to that recently published for the neutral molecule. According to AM1 hypersurface calculations based on the structural data, the phenyl twist angles obviously must be determined by lattice packing, and the negative charge is delocalized predominantly within the anthracene π system. The counter cation [Na^⊕(THF)₆], reported ordered for the first time, shows nearly octahedral coordination within a rather densily packed solvent shell. Due to the strong repulsions between the solvent molecules, its isodesmically calculated solvation enthalpy is smaller than that of the analogous dimethoxyethane complex [Na^⊕(DME)₃].     

Polymerization of 4-phenyl-1-butyne catalyzed by metathesis and Ziegler–Natta catalysts

The polymerization of 4-phenyl-1-butyne was carried out using metathesis and Ziegler-Natta catalysts. Especially, the Fe(acac)₃-AlEt₃ catalyst with toluene as a solvent produced an extremely high molecular weight polymer of M_w ≈ 10⁶. Solubility of the polymers at room temperature in organic solvents such as benzene, toluene, dichloromethane, chloroform, and THF was excellent despite their high molecular weights. It has been indicated that the polymer prepared by the Fe(acac)₃-AlEt₃ catalyst is of cis form with a high stereoregularity. © 1993 John Wiley & Sons, Inc.     

π-dimerization of pleiadiene radical cations at low temperatures revealed by UV–vis spectroelectrochemistry and quantum theory

One-electron oxidation of the non-alternant polycyclic aromatic hydrocarbon pleiadiene and related cyclohepta[c,d]pyrene and cyclohepta[c,d]fluoranthene in THF produces corresponding radical cations detectable in the temperature range of 293–263 K only on the subsecond time scale of cyclic voltammetry. Although the EPR-active red-coloured pleiadiene radical cation is stable according to the literature in concentrated sulfuric acid, spectroelectrochemical measurements reported in this study provide convincing evidence for its facile conversion into the green-coloured, formally closed shell and, hence, EPR-silent π-bound dimer dication stable in THF at 253 K. The unexpected formation of the thermally unstable dimeric product featuring a characteristic intense low-energy absorption band at 673 nm (1.84 eV; logε _max = 4.0) is substantiated by ab initio calculations on the parent pleiadiene molecule and the PF₆⁻ salts of the corresponding radical cation and dimer dication. The latter is stabilized with respect to the radical cation by 14.40 kcal mol⁻¹ (DFT B3LYP) [37.64 kcal mol⁻¹ (CASPT2/DFT B3LYP)]. An excellent match has been obtained between the experimental and TD-DFT-calculated UV–vis spectra of the PF₆⁻ salt of the pleiadiene dimer dication, considering solvent (THF) effects.     

Indenyl and fluorenyl transition metal complexes.: IV. Reactions of 2- and 4-azafluorenes with chromium hexacarbonyl

Reactions of 2- and 4-azafluorenes (I, II) and their methyl derivatives, 3-methyl-2-azafluorene (III) and 7-methyl-4-azafluorene (IV) with chromium hexacarbonyl in a $\text{1}\text{1}$ diglyme/heptane mixture at 140°C have been studied. A N-donor complex, C₁₂H₉NCr(CO)₅ is formed in the reaction of I with Cr(CO)₆. Compounds II–IV react to give arenechromiumtricarbonyl derivatives with benzene rather than pyridine ring bound to the metal. [η⁶-(4b,5,6,7,8,9b)-4-Azafluorene]chromiumtricarbonyl (VIII) gives the corresponding hydrochloride under the action of HCl. Methyl iodide decomposes VIII to produce 4-azafluorene iodomethylate. Deprotonation of VIII with BuLi in ether at ?20°C followed by dilution with hexane leads to precipitation of the corresponding Li salt (Xb), having η⁶-structure. Methylation of Xb with methyl iodide proceeds stereospecifically to yield the exo-methyl derivative XII. Treatment of VIII with excess t-BuOK at 25°C in THF results in a mixture of η⁶-(Xa) and η⁵-anions (XI), the former predominating.     

Synthesis of 5-alkoxy-4-amino-3-bromo-2(5H)-furanones containing benzene rings

Using KF as base and THF as solvent, different 5-alkoxy-3,4-dibromo-2(5H)-furanones were reacted with amines containing a benzene ring structure by Michael addition–elimination reaction at room temperature or 40 °C to give twenty-three 5-alkoxy-4-amino-3-bromo-2(5H)-furanones containing benzene rings, with yields of 21–86 % (mostly over 64 %). The structures of all the newly synthesized compounds were elucidated and confirmed by FTIR, UV, ¹H NMR, ¹³C NMR, and mass spectroscopy, elemental analysis, and X-ray single-crystal diffraction. This rapid synthesis of the series of 2(5H)-furanones derivatives with different bioactive units is not only an important synthetic strategy for 2(5H)-furanone derivatives but also a basis for synthesis of potential drug molecules for activity testing.     

The formation of grignard compounds—III : The influence of the solvent

The reaction of 6-bromo-1-hexene with Mg was studied in order to obtain information on the role of the solvent during the formation of Grignard reagents. The 5-hexenyl radical (R_nc^.) is known to cyclize rapidly and irreversibly to the cyclopentylmethyl radical (R_c^.). Changes in yields of the cyclized and non-cyclized Grignard compounds have been found on varying the solvent. Information on the radical pairs involved is obtained from the yields of the three possible coupling products (R_ncR_nc, R_ncR_c and R_cR_c). Results are correlated to the intensity of the CIDNP spectra of the Grignard compounds. It is found that basicity and viscosity of the solvents influence the reactions at the site of single electron transfer. Formation of Grignard compounds via radical pairs increases: (a) with decreasing basicity of the solvent, (b) with decreasing viscosity of the solvent, and (c) on dilution of THF with benzene. It is proposed that interaction between the radical and the π-electron rich solvent benzene plays a role in reactions run in Bz/THF mixtures.     

Bis[2,4‐diamino‐5‐(3,4,5‐trimethoxybenzyl)pyrimidin‐1‐ium] dl‐malate

<!?tpct=1pt>Racemic malic acid and trimethoprim [5‐(3,4,5‐trimethoxybenzyl)pyrimidine‐2,4‐diamine] form a 1:2 salt (monoclinic, P2₁/c), 2C₁₄H₁₉N₄O₃⁺·C₄H₄O₅²⁻, in which the malate component is disordered across a centre of inversion. The crystal structure of the salt consists of protonated trimethoprim residues and a malate dianion. The carboxylate group of the malate ion interacts with the trimethoprim cation in a linear fashion through pairs of N—H...O hydrogen bonds to form a cyclic hydrogen‐bonded motif. This is similar to the carboxylate–trimethoprim cation interaction observed earlier in the complex of dihydrofolate reductase with trimethoprim. The structure of the salt of trimethoprim with racemic dl ‐malic acid reported here is the first of its kind. The present study investigates the conformations and the hydrogen‐bonding interactions, which are very important for biological functions. The pyrimidine plane makes a dihedral angle of 78.08 (7)° with the benzene ring of the trimethoprim cation. The cyclic hydrogen‐bonded motif observed in this structure is self‐organized, leading to novel types of hydrogen‐bonding motifs in supramolecular patterns.