MoCl5/EtAlCl2-catalysed nonmetathesis polymerization of norbornadiene

Norbornadiene was polymerized, in moderate yield by MoCl₅ or EtAlCl₂. By using both components together, an increase in reaction rates and in polymer yields were observed. By the optimization of the reaction conditions, 100% of polymer yield was achieved. For comparison, the polymerization of the NBD was also accomplished by using initiators such as AlCl₃, Et₃Al, AZBN, and n-butyl lithium. All the obtained polymers gave similar IR and NMR spectra indicating the presence of the polynortricyclene structures. Though they show different molecular weight distribution, the solubilities of the polymers (obtained using MoCl₅, AlCl₃, EtAlCl₂, and MoCl₅/EtAlCl₂) are very similar. DTA analyses show that the polymers (obtained by using MoCl₅/EtAlCl₂ pair or n-butyl lithium or Et₃Al) have high thermal stabilities whereas all the other polymers are unstable in air. © 1996 John Wiley & Sons, Inc.     

Die Reaktion von Molybdänpentachlorid mit (SCN)2, (SeCN)2 und ICN

Reaction of Molybdenum Pentachloride with (SCN)₂, (SeCN)₂, and ICN By reaction of MoCl₅ with (SCN)₂, (SeCN)₂, and ICN in CCl₄ or H₂CCl₂ the compounds MoCl₅(NCS)₂, MoCl₅(NCSe)₂, and MoCl₅NCI were obtained. They are very sensitive towards hydrolysis and decompose on heating. The compounds are characterized by their vibrational and EPR spectra which indicate that the pseudohalogen is bonded via a nitrogen atom.     

N(SCl)2 ⊕[MoCl5(NSCl)]⊖, ein Chlorthionitrenokomplex von Molybdän(VI)

N(SCl)₂^⊕ [MoCl₅(NSCl)]^?, a Chlorothionitrene Complex of Molybdenum (VI) . The title compound is formed together with MoCl₃(N₃S₂) by the reaction of MoCl₄ or MoCl₅ with (NSCl)₃ in CH₂Cl₂. The black, crystalline compound was characterized by its i.r. spectrum and an X-ray crystal structure determination. N(SCl)₂^⊕[MoCl₅(NSCl)]^? crystallizes in the monoclinic space group P2₁/n with four formula units per unit cell. The lattice constants are a = 716.3, b = 1627.4, c = 1178.9 pm and β = 100.90°. The [MoCl₅(NSCl)]^? ion posseses an almost linear Mo = N = S grouping with bond lengths that can be interpreted as double bonds. Crystal data for AsPh₄[MoCl₅(NSCl)] are reported.     

The preparation and molecular structure oftrans-[MoCl2(PMe2Ph)4]

Summary The compoundtrans-[MoCl₂(PMe₂Ph)₄] has been prepared by the reduction of MoCl₅ (by Mg) or of [MoCl₃(PMe₂Ph)₃] (by LiBuⁿ) in the presence of PMe₂Ph in tetrahydrofuran (THF). It has _eff=2.84 B.M. and crystallises in space group P1 witha=11.591(3),b=12.931(3),c=12.703(3) Å, = 95.28(2), =105.97(2), =103.54(2)°. Refinement of the structure gave R=0.036. The Mo-Cl and Mo-P distances average 2.443(6) and 2.534(8) Å, respectively.Low-valent phosphine complexes of the Group VI metals continue to attract much attention because of their involvement in studies of the catalytic activation of dinitrogen⁽¹⁾, dihydrogen(^{2, 3}), alkenes and alkynes(⁴). As a by-product during our studies of dinitrogen(¹) and hydride(²) complexes of molybdenum and tungsten, we obtainedtrans-[MoCl_2- (PMe₂Ph)₄] as yellow, paramagnetic crystals (_eff= 2.84 B.M.). We first obtained the compound during the attempted synthesis ofcis-[Mo(N₂)₂(PMe₂Ph)₄] by reduction of MoCl₅ with Mg in the presence of PMe₂Ph (see Experimental). Upon identification of the compound we found that it could be readily synthesised by treatment of [MoCl₃(PMe₂Ph)₃]⁽⁵⁾ with LiBuⁿ in THF in the presence of PMe₂Ph (experimental).The complex was shown to have thetrans structure by x-ray analysis (Figure). Analogues oftrans-[MoCl₂(PMe₂Ph)₄] have been prepared, namely [CrCl₂(Me₂PCH₂CH₂PMe₂)₂]⁽⁶⁾,trans- [MoCl₂(PMe₃)₄]⁽⁷⁾, [WCl₂(PMe₂Ph)₄]⁽⁸⁾ and [WCl₂(PMe₃)₄]⁽⁴⁾, of which onlytrans-[MoCl₂(PMe₃)₄] has been examined by X-rays⁽⁷⁾. Its principal structural parametersi.e. d(Mo-Cl)= 2.420(6), d(Mo-P)_av=2.496(3) Å⁽⁶⁾ are close to those found here fortrans-[MoCl₂(PMe₂Ph)₄].     

Aromatic H／D Exchange Reaction Catalyzed by Groups 5 and 6 Metal Chlorides

Groups 5 and 6 metal chlorides such as MoCl5, WCI6, NbCl5 and TaCl5 were found to be simple and very efficientcatalysts for the aromatic H/D exchange reactions. Compared with other metal chlorides such as ZnCl2, SnCl4 and TiCl4, groups 5 and 6 metal chlorides showed better catalytic activity in the H/D exchange reaction of naphthalene with C6D6. Deuteration of anthracene using MoC15 as a catalyst proceeded within 24 h at room temperature. Other aromatic compounds such as toluene, diphenylmethane and 1,1,2-triphenylethane were also deuterated smoothly in C6D6 within 24 h at room temperature.     

A new and efficient method for the facile synthesis of N-acyl sulfonamides under Lewis acid catalysis

The N-acylation of sulfonamides with carboxylic acid anhydrides in the presence of Lewis acids is described. Several Lewis acids such as BF₃·Et₂O, ZnCl₂, MoCl₅, TiCl₄, B(C₆F₅)₃, Sc(OTf)₃ and I₂ were found to catalyze the reaction efficiently to furnish the N-acylated products in good yields under solvent-free conditions. The reactions of various sulfonamides were studied with different carboxylic acid anhydrides including the less reactive benzoic and pivalic anhydrides, in the presence of 3 mol % ZnCl₂ as the catalyst. Carboxylic acids were also successfully used as acylating agents via the mixed anhydride method.     

Over‐Oxidation as the Key Step in the Mechanism of the MoCl5‐Mediated Dehydrogenative Coupling of Arenes

Molybdenum pentachloride is an unusually powerful reagent for the dehydrogenative coupling of arenes. Owing to the high reaction rate using MoCl₅, several labile moieties are tolerated in this transformation. The mechanistic course of the reaction was controversially discussed although indications for a single electron transfer as the initial step were found recently. Herein, based on a combined study including synthetic investigations, electrochemical measurements, EPR spectroscopy, DFT calculations, and mass spectrometry, we deduct a highly consistent mechanistic scenario: MoCl₅ acts as a one‐electron oxidant in the absence of TiCl₄ and as two‐electron oxidant in the presence of TiCl₄, but leads to an over‐oxidized intermediate in both cases, which protects it from side reactions. In the course of aqueous work‐up the reagent waste (Mo^III/IV species) acts as reducing agent generating the desired organic C?C coupling product.     

Electronic structure,spectra, and thermodynamical functions of molybdenum pentachloride

The SCF-X -SW method in non-relativistic and quasi-relativistic versions has been used to calculate the electronic structure, ionization potentials, energies and oscillator strengths of the optical transitions in MoCl₅. The electronic absorption spectrum of the gaseous MoCl₅ has been measured. The interpretation of the photoelectron and optical spectra of MoCl₅ is given. Spinpolarization effects and relativistic corrections are discussed. The thermodynamical functions of MoCl₅ (gas) are calculated.     

Kinetics of α-olefin metathesis on binary and ternary catalytic systems based on MoCl<Subscript>5</Subscript>/SiO<Subscript>2</Subscript>: Determination of the number of active centers and the mechanisms of their formation,deactivation, and reactivation

The kinetics of α-olefin metathesis in the presence of binary (MoCl₅/SiO₂-Me₄Sn) and ternary catalytic systems (MoCl₅/SiO₂-Me₄Sn-ECl₄, E = Si or Ge) was studied. It was found that reactivation in the course of metathesis occurred on the addition of a third component (silicon tetrachloride or germanium tetrachloride in combination with tetramethyltin) to a partially deactivated catalyst. The number of active centers was determined (5–6% of the amount of Mo), and the mechanisms of formation, deactivation, and reactivation were proposed for the binary and ternary catalytic systems. The roles of the individual components of the catalytic systems were revealed.     

Gravimetrische Analyse von Halogeniden und Oxidhalogeniden nach der „H-Rohr-Methode“

The application of the “H-tube method” for analyzing the halides and oxyhalides of many metals has been extended by modification of the prior method described bySchÄfer andDohmann. This very simple and time-saving method is applicable now to analyze volatile (e.g. MoOCl₄, MoO₂Cl₂) compounds as well as those, which are attacked easily (e.g. MoCl₅, WOCl₄) or difficulty (e.g. MoCl₂) by nitric acid vapour at higher temperatures.     

Polymerization of acenaphthylene by transition metal catalysts

The polymerization of acenaphthylene (ACN) was examined in the presence of the group V and VI transition metal salts such as WCl₆, MoCl₅, TaCl₅, and NbCl₅, as catalysts under various reaction conditions. These transition metal salts were found to be effective catalysts for the polymerization of ACN. The polymerization of ACN by WCl₆ in chlorobenzene proceeded at a high initial rate when the monomer to catalyst mole ratio was 200. In addition, it was observed that aromatic solvents generally were found to be superior to aliphatic solvents for both conversion and molecular weight. The structure of the resulting polymers was characterized by means of NMR, IR, UV, and x-ray diffraction. Emission properties were also investigated. Fluorescence emission spectra of the polymers obtained by WCl₆ as a catalyst varied strongly depending on the polymerization solvent. Thus, it appears that the polyacenaphthylene produced by WCl₆ was a different configuration dependent on the polymerization solvents used.     

Polymerization of acetylene and its monosubstitutes in the presence of halides and oxohalides of molybdenum and tungsten

MoCl₅, WCl₆, and OMoCl₄ were found to be effective initiators for the polymerization of acetylene and its monosubstituted derivatives RC?CH. The polymerization proceeded in homogeneous and heterogeneous media and was carried out in nonpolar (chloroalkanes, aromatic hydrocarbons) and polar (THF, acetone, dioxane, carboxylic acids) solvents to give a high yield of polymers.     

Multifrequency EPR and DENR of polyacetylene composite

The organo-inorganic composite MoCl_{1.9 ± 0.1}(C_{30 ± 1}H_{30 ± 1}), a product of interaction of MoCl₅ with C₂H₂, has been studied by X- and W-band EPR, double electron nuclear resonance, and W-band electron spin echo spectroscopy. The composite consists of nanosized organometallic molybdenum clusters in the polyacetylene matrix. It has been shown that the composite contains three types of magnetic centers: the first is related to the existence of paramagnetic molybdenum atoms in the polyacetylene matrix, and the other two are paramagnetic defects of the matrix.     

Reactions of terpene alcohols and diols with chlorine dioxide in dimethylformamide

The system chlorine dioxide–dimethylformamide in combination with or without a catalytic amount of MoCl₅, CeCl₃, ZrOCl₂, or VO(acac)₂ induces oxidative chlorination of a number of bicyclic terpene alcohols and vicinal diols. 2α-Chloropinan-3-one, 3α-chloro-10β-pinan-4-one, 5α-chloro-3α-hydroxycaran-4-one, 5β-chloro-3β-hydroxycaran-4-one, and 4α-chloro-2α-hydroxypinan-3-one were thus synthesized in good preparative yields.     

Reactions of molybdenum(III) with macrocyclic polythiaethers

Reactions of MoCl₃(THF)₃ and MoCl₃(PrCN)₃ with the macrocyclic polythiaethers: 1,4,8,11-tetrathiacyclotetradecane (TTP) and 1,4,7,10,13,16-hexathiacyclooctadecane (HTO) were studied. The type of reaction and the complexes formed depend on reactant concentration and nature of the solvent. The complexes: [MoCl₃(HTO)], [(MoCl₃)₂(HTO)(THF)₃], [MoCl₃(TTP)(THF)] and [MoCl₃(TTP)] in which the macrocyclic polythiaethers are coordinated to the molybdenum through sulphur atoms were isolated. Some new mixed-valence complexes were formed in reactions where a partial change in the molybdenum oxidation state and a cleavage of the macrocyclic ring took place. The following complexes were isolated: [Mo₃Cl₉(PHT)₂(PrCN)]·CH₂Cl₂, [Mo₃Cl₉(PHT)₂(THF)] · CH₂Cl₂, [Mo₂Cl₆ (PHT)] · CH₂Cl₂, [Mo₃Cl₉(TTT)₂(THF)] · CH₂Cl₂, where PHT = 3,6,9,12,15-pentathiaheptadec- 16-ene-1-thiolato(1-) and TTT = 4,7,11-trithiatridec-12-ene-1-thiolato(1-). The complexes were characterized on the basis of elemental analyses, magnetic measurements, IR, ¹H NMR, ¹³C NMR and mass spectra.     

Reaktionen von TaCl5, MoCl5 und WCl6 mit Bis(trimethylsilyl) carbodiimid

Reactions of TaCl₅, MoCl₅, and WCl₆ with Bis(trimethylsilyl)carbodiimide When TaCl₅ reacts with Me₃SiNCNSiMe₃ (Me = CH₃) in a 1:1 molar ratio, 1 mol Me₃SiCl and dimeric [Cl₄TaNCNSiMe₃]₂ is formed. The vibrational spectra (IR and Raman) show a planar structure of approximate C_2h symmetry. Polymeric [Cl₄WNCN]_n is formed by the reaction of WCl₆ and Me₃SiNCNSiMe₃, but 2 mol Me₃SiCl result in this 1:1 molar interaction. On the other hand MoCl₅ and Bis(trimethylsilyl)carbodiimide (molar ratio 2:1) forms polymeric [(Cl₄Mo)₂NCN]_n, a compound with Mo? N? Mo and Mo—(Cl₂)—Mo bridges. The IR spectra of these carbodiimide derivatives are used for structural suggestions.     

Polymerization of 1-methoxy-1-ethynylcyclohexane by transition metal catalysts

The polymerization of 1-methoxy-1-ethynylcyclohexane (MEC) was carried out by various transition metal catalysts. The catalysts MoCl₅, MoCl₄, and WCl₆ gave a relatively low yield of polymer (≤ 16%). The catalytic activity of Mo-based chloride catalyst was greater than that of W-based chloride catalyst. However, catalyst tungsten carbene complex (I) gave a larger molar mass and higher yield in the presence of a Lewis acid such as AlCl₃ than in the absence of a Lewis acid. The activity of the tungsten carbene complex was obviously affected by Lewis acidity. The catalyst PdCl₂ was a very effective catalyst for the present polymerization and gave polymers in a high yield. The structure of the resulting poly(MEC) was identified by various instrumental methods as a conjugated polyene structure having an α-methoxycyclohexyl substituent. The poly(MEC)s were mostly light-brown powders and completely soluble in various organic solvents such as tetrahydrofuran (THF), chloroform (CHCl₃), ethylacetate, n-butylacetate, dimethylformamide, benzene, xylene, dimethylacetamide, 1,4-dioxane, pyridine, and 1-methyl-2-pyrrolidinone. Thermogravimetric analysis showed that the polymer started to lose mass at 125°C and that maximum decomposition occurred at 418°C. The x-ray diffraction diagram shows that poly(MEC) has an amorphous structure. © 1997 John Wiley & Sons, Inc.     

Beiträge zur Chemie der Alkylverbindungen von Übergangsmetallen. XXXVII. Zur Existenz von 1-Norbornylverbindungen des Wolframs und Molybdäns

Contributions to the Chemistry of Transition Metal Alkyl Compounds. XXXVII. About the Existence of 1-Norbornyl Compounds of Tungsten and Molybdenum Reactions of WCl₆, WCl₄, WO₂Cl₂, WOCl₄, MoCl₅, and MoO₂(acac)₂ with 1-Norbornyl lithium (1-NorLi¹)) are described. From WCl₆ and WCl₄ [(1-Nor)₂W]_n is formed, whereas in dependence of the solvent WO₂Cl₂ and WOCl₄ are transformed into the complexes Li₂[1-NorWOCl₄] · THF, Li[WOCl₄], Li[WO₂Cl₂], and Li₂[WO₂Cl₂]. MoCl₅ and MoO₂(acac)₂ are reduced with formation of Li[MoCl₅], Li[MoO₂(acac)₂] and Li₂[MoO₂(acac)₂]. — Stable (1-Nor)₄M-derivatives of molybdenum and tungsten, comparable those of 3d-metals (M = Ti? Co) seem not to exist.     

Organometallic Molybdenum(V) Complexes with Primary Phosphine Ligands. Syntheses,Spectroscopic Properties and Molecular Structures of [Cp°MoCl4(PH2R)] (R = But, 1‐Ad,Cy, Ph, 2, 4, 6‐Me3C6H2, 2, 4, 6‐Pri3C6H2, Cp° = C5EtMe4)

[Cp°MoCl₄] (Cp° = C₅EtMe₄) reacts with primary phosphines PH₂R to give the paramagnetic phosphine complexes [Cp°MoCl₄(PH₂R)] [Cp° = C₅EtMe₄, R = Bu^t ( 1 ), 1‐Ad (1‐Ad = 1‐adamantyl; 2 ), Cy ( 3 ), Ph ( 4 ), Mes (Mes = 2, 4, 6‐Me₃C₆H₂; 5 ), Tipp (Tipp = 2, 4, 6‐Prⁱ₃C₆H₂; 6 )]. 1 — 6 were characterized spectroscopically (IR, MS), and X‐ray crystal structures were determined for 1 — 4 and 6 . EPR investigations in liquid and frozen solution confirmed the presence of Mo^V species, and the data were used to analyze the spin‐density distribution in the first coordination sphere. Complexes 3 and 4 react with two equivalents of NEt₃ with formation of [Cp°MoCl₂(η³‐P₄Cy₄H)] ( 7 ) and [Cp°₂Mo₂(μ‐Cl)₂(μ‐P₄Ph₄)] ( 8 ), respectively, in low yield. Complexes 7 and 8 were characterized by X‐ray crystallography.     

Beiträge zur Chemie der Oxidhalogenide von Molybdän und Wolfram. VI. Thermische Zersetzung von MoCl3 und MoOCl2

The temperature dependence of the thermal decay of α-MoCl₃ was determined and the entropies of MoCl₃ and MoCl₂ calculated. The decomposition behaviour of MoOCl₂ under equilibrium conditions may be described by the equation The decomposition reactions 6 MoOCl₂,s = Mo + MoO₂ + 4 MoOCl₃,g has only inferior importance. From the results the enthalpy and entropy values of MoOCl₂ are derived (data see “Inhaltsübersicht”).