Deoxybenzoins from Stille carbonylative cross-couplings using molybdenum hexacarbonyl

Stille-type carbonylative cross-couplings, employing palladium catalysis and Mo(CO)₆ as the carbon monoxide carrier, were used for the preparation of deoxybenzoins. Straightforward transformations were conveniently performed in closed vessels at 100 °C, providing the products in good yields. Benzyl bromides and chlorides were used as coupling partners with aryl and heteroaryl stannanes. This mild three-component carbonylation employs the destabilizing agent DBU to promote smooth release of carbon monoxide from Mo(CO)₆, which made this protocol operationally simple and minimized the formation of Stille diarylmethane products.     

Fast microwave promoted palladium-catalyzed synthesis of phthalides from bromobenzyl alcohols utilizing DMF and Mo(CO)6 as carbon monoxide sources

A fast method utilizing in situ generated CO for the synthesis of phthalides has been developed. DMF and Mo(CO)₆ were applied as two alternative CO-sources in these microwave promoted carbonylation-lactone formation reactions. Mo(CO)₆ was found to be the more generally applicable CO-source and provided phthalides as well as dihydroisocoumarin, dihydroisoindone, and phthalimide from the corresponding aryl bromide via an efficient CO insertion within a 1 h reaction time.     

Activation of the Ge-H bond of Et3GeH in photochemical reaction with molybdenum(0) carbonyl complexes and hydrogermylation of norbornadiene

The germane intermediate σ-complexes, characterized by high-field resonances in the region from −6 to −8 ppm, have been detected during the ¹H NMR spectroscopy monitoring of the photochemical reaction of Et₃GeH with Mo(CO)₆, [Mo(CO)₄(η⁴-cod)], and [Mo(CO)₄(η⁴-nbd)] in the NMR tube. The activation of the Ge-H bond of germane in photochemical reaction of the norbornadiene (nbd) complex [Mo(CO)₄(η⁴-nbd)] has been applied in the hydrogermylation of norbornadiene, which leads to the formation of triethylgermylnorbornene.     

Kinetic and thermochemical characteristics of the dissociation of Mo(CO)6 and W(CO)6

The thermal dissociation of gaseous Mo(CO)₆ and W(CO)₆ in an argon carrier gas, Mo(CO)₆ → Mo(CO)₅ + CO (1) and W(CO)₆ → W(CO)₅ + CO (2), is studied over temperature ranges of ∼585–685 K for (1) and ∼690−810 K for (2) at a total gas concentrations of 4 × 10⁻⁶ and 4 × 10⁻⁵ mol/cm³ by using the shock tube technique in conjunction with absorption spectrophotometry. The measured rate constants are extrapolated to the high-pressure limit by means of a newly developed procedure, with the resultant expressions for the indicated temperature ranges reading as k_d1,∞(T),[s⁻¹] = 10^{16.12 ± 0.68}exp[(−148.8 ± 8.1 kJ/mol)/RT] and k_d2,∞(T),[s⁻¹] = 10^{15.93 ± 0.63}exp[(−171.7 ± 8.9 kJ/mol)/RT]. Comparison of the high-pressure dissociation rate constants with the published data revealed a considerable discrepancy, a tentative explanation of which is given. Based on the obtained high-pressure dissociation rate constants and the available data on the high-pressure room-temperature rate constants for the reverse reaction of recombination, the first bond dissociation energies for these molecules are evaluated and compared with previous determinations, both theoretical and experimental. The enthalpies of formation of Mo(CO)₅ and W(CO)₅ are determined: Δ_fH°(Mo(CO)₅, g, 298.15 K) = −644.1 ± 5.6 kJ/mol and Δ_fH°(W(CO)₅, g, 298.15 K) = −581.9 ± 6.6 kJ/mol. Based on the enthalpies of formation of Mo(CO)₅, W(CO)₅, Mo(CO)₆, and W(CO)₆, and the published molecular parameters of these four species, their thermochemical functions are calculated and presented in the form of NASA seven-term polynomials.     

Reactions of Cr,Mo, W,and Mn carbonyls with 3,6-di-tert-butyl-o-quinone under the action of elastic wave pulses

Solid-state reactions of Cr, Mo, W, and Mn carbonyls with 3,6-di-terl-butyl-o-benzoquinone (Q) proceeding in molded powder-like mixtures (carbonyl-Q) treated with pulses of elastic waves were studied. The products of the reactions of Q with Cr(CO)₆, Mo(CO)₆, and W(CO)₆ are paramagnetic serniquinone complexes of Cr, Mo, and W. The formation of two semiquinone complexes with one or two manganese atoms was detected in the reaction of Mn₂(CO)₁₀ with Q.Translated fromIzvestiya Akademi Nauk. Seriya Khimicheskaya, No. 11, pp.2780–2784, November,1996     

Plasma reaction of group VI metal carbonyls

The hexacarbonyl compounds of Cr, Mo, and W have been used as precursors in plasma-enhanced chemical vapor depositions (PECVD). They form films of good adherence on glass, ceramics, and a variety of polymers. The nature of the deposits depends very much on the composition of the gas, which forms the plasma. When pure argon is used, the resulting films contain considerable amounts of oxygen and carbon. Films deposited in hydrogen/argon mixtures consist of the metal and/or the carbide. With Ar/O₂ mixtures, Mo(CO)₆ and W(CO)₆ are converted into films of MoO₃ and WO₃, respectively. When H₂S/H₂ mixtures are used as plasma gas, Mo(CO)₆ yields films consisting of MoS_x.     

Synthesis, spectroscopic and structural characterisation of molybdenum, tungsten and manganese carbonyl complexes of tetrathio- and tetraseleno-ether ligands

A range of complexes of the binucleating tetrathio- and tetraseleno-ether ligands, 1,2,4,5-C₆H₂(CH₂EMe)₄ (E = S, L³ or Se, L⁴) or C(CH₂EMe)₄ (E = S, L⁵ or Se, L⁶) and of bidentate analogues 1,2-C₆H₂(CH₂EMe)₂ (E = S, L¹ or Se = L²) with molybdenum and tungsten carbonyls and manganese carbonyl chloride have been prepared, and characterised by IR and multinuclear NMR (¹H, ¹³C{¹H}, ⁷⁷Se, ⁵⁵Mn, ⁹⁵Mo) spectroscopy and mass spectrometry. Crystal structures are reported for [Mo(CO)₄(L²)], [Mo(CO)₄(L³)], [Mo(CO)₄(μ-L³)Mo(CO)₄], [Mo(CO)₄(L⁴)], [Mn(CO)₃Cl(μ-L³)Mn(CO)₃Cl], [Mo(CO)₄(μ-L⁵)Mo(CO)₄], [Mn(CO)₃Cl(L⁵)] and two forms (containing meso and DL diastereoisomers) of [W(CO)₄(L⁵)].     

The use of half-sandwich iridium dithiolate and diselenolate complexes, Cp*Ir(L)(ER)2 (L=CO, PMe3, PPh3; ER=SPh, SePh, SeMe), for the synthesis of heterodimetallic compounds. The molecular structure of Cp*Ir(CO)(μ-SePh)2[Mo(CO)4]

Carbonyl–iridium half-sandwich compounds, Cp*Ir(CO)(EPh)₂ (E=S, Se), were prepared by the photo-induced reaction of Cp*Ir(CO)₂ with the diphenyl dichalcogenides, E₂Ph₂, and used as neutral chelating ligands in carbonylmetal complexes such as Cp*Ir(CO)(μ-EPh)₂[Cr(CO)₄], Cp*Ir(CO)(μ-EPh)₂[Mo(CO)₄] and Cp*Ir(CO)(μ-EPh)₂[Fe(CO)₃], respectively. A trimethylphosphane–iridium analogue, Cp*Ir(PMe₃)(μ-SeMe)₂[Cr(CO)₄], was also obtained. The new heterodimetallic complexes were characterized by IR and NMR spectroscopy, and the molecular geometry of Cp*Ir(CO)(μ-SePh)₂[Mo(CO)₄] has been determined by a single crystal X-ray structure analysis. According to the long Ir…Mo distance (395.3(1) Å), direct metal–metal interactions appear to be absent.     

About the Reaction of C(PPh3)2 with [M(CO)6] (M = Cr,Mo): Unusual Formation of μ-Carbonato Complexes of Mo under Participation of THF

Attempts to synthesize complexes of group 6 carbonyl compounds [M(CO)₆] (M = Cr, Mo, W) with the carbone C(PPh₃)₂ ( 1 ) via the photo chemically created adducts [(CO)₅M(THF)] lead to quantitative formation of the salts [HC(PPh₃)₂]₂[M₂(CO)₁₀] ( 2 , Cr; 3 , Mo; 4 , W). Alternatively, a long-time thermal reaction of [Mo(CO)₆] performed with 1 in THF generates a series of products initiated by a Wittig-type reaction. In addition to 3 , minor amounts of [(CO)₅MoCCPPh₃] ( 8 ), [(CO)₅MoO₂CC{PPh₃}₂] ( 5 ), and the carbonate complexes [HC(PPh₃)₂]₂[(CO)₅Mo(CO₃)Mo(CO)₄] ( 6 ) and [HC(PPh₃)₂]₂[(CO)₄Mo(CO₃)Mo(CO)₄] ( 7 ) were found. Compounds 2 , 3 , 5 , 6 , and 7 were characterized by X-ray analyses, ³¹P NMR, and IR spectroscopy. The water, necessary for the formation of the carbonate, stems from decomposition of THF.     

Gas phase ion chemistry of molybdenum hexacarbonyl

In an ion cyclotron resonance (ICR) cell, Mo(CO)_n⁺ ions (n = 0–6), generated by electron ionization (EI) with 70 eV electrons, on collisions with Mo(CO)₆ undergo charge exchange (confirmed by isotopic experiments), collision-induced dissociation (CID), and association reactions to produce Mo_m(CO)_n⁺ ions (m = 1–6). Reactions are essentially complete within 9 s at a pressure of 3 × 10⁻⁹ Torr, as recorded by the manifold ion gauge (uncalibrated); Mo(CO)_n⁺ ions with n = 0–5 have been consumed within this time whereas Mo(CO)₆⁺ ions have achieved a steady concentration. All Mo₂(CO)_n⁺ ions (n = 0–11) were observed: the abundances of dimolybdenum-containing ions with n < 7 decrease at extended reaction times, whereas those with n ≥ 7 remain steady or increase slowly, implying that reactivity decreases with increasing CO content. The major dimers have n = 7, 9, and 10. When subjected to CID the Mo₂(CO)₇⁺ ion yields Mo₂(CO)_n⁺ ions (n = 0–6). Most Mo₃(CO)_n⁺ ions (n = 0–13) were observed, those with n = 9 being formed most readily. Similar observations apply to larger clusters, the most abundant ions being those with CO:Mo ratios of 2–3:1. Mo(CO)_n⁺ ions (n = 0, 3–6) formed by EI with 15 eV electrons are unreactive for reaction times of at least 5 s at the same pressure. General reaction sequences are proposed. Negative ions generated with 70 eV electrons (∼ 90% Mo(CO)₅⁻) are much less reactive but also lead to cluster ion formation on reaction with Mo(CO)₆.     

A study of molybdenum catalysts in the polymerization of 2,5-didodecyl-1,4-dipropynylbenzene

The reaction of 2,5-didodecyl-1,4-dipropynylbenzene with different molybdenum sources (Mo(CO)₆, norbornadiene-Mo(CO)₄, cyclooctadiene-Mo(CO)₄, cycloheptatriene-Mo(CO)₃, (PhCCPh)₃Mo(CO), (acac)₂MoO₂/AlEt₃) was investigated in the presence of 4-chlorophenol or 2-fluorophenol. Upon heating to 105-130 °C, the formation of didodecyl-PPE resulted. The degree of polymerization of the PPE is dependent on the used phenol and to the utilized molybdenum precursor. The most active catalyst forms from (acac)₂MoO₂, AlEt₃ and 2-fluorophenol. This catalyst combination gives high molecular weight PPEs after 6 h at 105 °C.     

Molybdenum hexacarbonyl supported on amine modified multi‐wall carbon nanotubes: an efficient and highly reusable catalyst for epoxidation of alkenes with tert‐butylhydroperoxide

In the present work, highly efficient epoxidation of alkenes catalyzed by Mo(CO)₆ supported on multi‐wall carbon nanotubes modified by 2‐aminopyrazine, APyz‐MWCNTs, is reported. The prepared catalyst was characterized by elemental analysis, scanning electron microscopy, FT IR and diffuses reflectance UV–vis spectroscopic methods. This new heterogenized catalysts, [Mo(CO)₆@APyz‐MWCNT], was used as a highly efficient catalyst for epoxidation of alkenes with tert‐BuOOH. This robust catalyst was reused several times without loss of its catalytic activity. Copyright © 2010 John Wiley & Sons, Ltd.     

Comparative Investigation of Mo(CO)6 Adsorption on Clean and Oxidized Si(111) Surfaces

Mo(CO)₆ adsorption on the clean, oxygen-precovered and deeply oxidized Si(111) surfaces was comparatively investigated by high-resolution electron energy loss spectroscopy. The downward vibrational frequency shift of the C-O stretching mode in adsorbed Mo(CO)₆ illustrates that different interactions of adsorbed Mo(CO)₆ occur on clean Si(111) and SiO₂/Si(111) surfaces, weak on the former and strong on the latter. The strong interac-tion on SiO₂/Si(111) might lead to the partial dissociation of Mo(CO)₆, consequently the formation of molybdenum subcarbonyls. Therefore, employing Mo(CO)₆ as the precursor, metallic molybdenum could be successfully deposited on the SiO₂/Si(111) surface but not on the clean Si(111) surface. A portion of the deposited metallic molybdenum is transformed into the MoO₃ on the SiO₂/Si(111) surface upon heating, and the evolved MoO₃ finally desorbs from the substrate upon annealing at elevated temperatures.     

Synthesis and spectroscopic studies of some new metal carbonyl derivatives of 1-(2-pyridylazo)-2-naphthol

Interaction of 1-(2-pyridylazo)-2-naphthol (PAN) with [Mo(CO)₆] in air resulted in formation of the tricarbonyl oxo-complex [Mo(O)(CO)₃(PAN)], 1. The dicarbonyl complex [Ru(CO)₂(PAN)], 3, was obtained from the reaction of [Ru₃(CO)₁₂] with PAN. In presence of triphenyl phosphine (PPh₃), the reaction of PAN with either Mo(CO)₆ or Ru₃(CO)₁₂ gave [Mo(CO)₃(PAN)(PPh₃)], 2, and [Ru(CO)₂(PAN)(PPh₃)], 4. All the complexes were characterized by elemental analysis, mass spectrometry, IR, and NMR spectroscopy. The thermal properties of the complexes were also investigated by thermogravimetry.     

Group V complexes of the tricarbonyl(η-cycloheptatrienylium)molybdenum cation and their reduction to monosubstituted derivatives of tricarbonyl(1-6-η-cycloheptatriene)molybdenum

Reaction of [(η-C₇H₇)Mo(CO)₃][PF₆] with certain Group V donor ligands afforded monosubstituted complexes [(η-C₇H₇)Mo(CO)₂L][PF₆] (L = P(OPh)₃, PPh₃, PPh₂Me, PPhMe₂, AsPh₃, SbPh₃). These were reduced by NaBH₄ to the corresponding cycloheptatriene complexes (1-6-η-C₇H₈)Mo(CO)₂L. In addition, the preparation of alkylcycloheptatriene complexes (1-6-η-C₇H₇R)Mo(CO)₂L (R = Me, L = P(OPh)₃, PPh₃, PPh₂Me; R = t-Bu, L = PPh₃) is described. Spectroscopic properties, including ¹³C NMR, are reported.     

Aminocyclophosphazene derivatives of molybdenum carbonyl

Summary Reactions of aminated cyclotri-and tetraphosphazenes,viz., N₃P₃L₆ and N₄P₄L₈ (L=–NC₅H₁₀, –NC₄H₈O and –HNC₆H₁₁) with Mo(CO)₆ have been studied. N₃P₃L₆ yield (N₃P₃L₆)Mo(CO)₃ derivatives, whereas tetracarbonyl substituted derivatives, (N₄P₄L₈)Mo(CO)₄, are obtained with N₄P₄L₈. Several mixed derivatives of both cyclotri- and tetra-phosphazenes have been synthesised with (o-phen)Mo(CO)₄.     

Molybdenum hexacarbonyl supported on functionalized multi-wall carbon nanotubes: Efficient and highly reusable catalysts for epoxidation of alkenes with tert-butyl hydroperoxide

In the present work, highly efficient epoxidation of alkenes catalyzed by Mo(CO)₆ supported on amines modified multi-wall carbon nanotubes, MWCNTs, is reported. The prepared catalysts were characterized by elemental analysis, scanning electron microscopy, FT-IR and diffuse reflectance UV-Vis spectroscopic methods. These new heterogenized catalysts, [Mo(CO)₆@amines-MWCNT], were used as highly efficient catalysts for epoxidation of alkenes with tert-BuOOH. These robust catalysts could be reused several times without loss of their catalytic activities.     

On the use of common effective core potentials in density functional calculations. I. Test calculations on transition-metal carbonyls

The performance of effective core potentials adjusted at the Hartree-Fock level but applied in density functional calculations has been tested in a set of calculations using various basis sets and/or core potentials. Test molecules have been the first-row transition-metal carbonyls Cr(CO)₆, Fe(CO)₅, and Ni(CO)₄ and the second-row carbonyls Mo(CO)₆, Ru(CO)₅, and Pd(CO)₄. Only “small-core” potentials have been used, and these are able to reproduce molecular structures and bond energies from all-electron calculations. Relativistic effects have been estimated for the second-row carbonyls by using quasi-relativistic core potentials. © 1996 John Wiley & Sons, Inc.     

Bowl-shaped aromatic hydrocarbon precursors of fullerenes as η<Superscript>6</Superscript>-π-ligands in transition metal complexes: Complexes based on sumanene C<Subscript>21</Subscript>H<Subscript>12</Subscript> derivatives

The density functional theory in the PBE approximation was used to explore the geometry and electronic structure of sumanene C₂₁H₁₂ and its five derivatives C₂₁H₁₂R₆ (R = H, F, Cl, Br, and CN). The R groups in C₂₁H₁₂R₆ molecules are attached to carbon atoms in α positions with respect to the central six-membered ring. The possibility of the formation of C₂₁H₁₂R₆η ⁶-π complexes with Cr(C₆H₆), Cr(CO)₃, Mo(C₆H₆), and Mo(CO)₃ was discussed. The relative stability of these complexes was evaluated. The attachment of M(C₆H₆) and M(CO)₃ (M = Cr, Mo) to sumanene C₂₁H₁₂ with the formation of η⁶-π bonds is energetically less favorable than their attachment to sumanene derivatives C₂₁H₁₂R₆. The complexes of sumanene derivatives with Cr(C₆H₆), Cr(CO)₃, Mo(C₆H₆), and Mo(CO)₃ were found to be the most promising objects for synthesis. The C₆₀ and η⁶-(C₆H₆)M-C₆₀ and η⁶-(CO)₃M-C₆₀ (M = Cr, Mo) fullerene complexes were predicted to be much less stable than the η⁶-(CO)₃M-C₆₀R₆ and η⁶-(C₆H₆)M-C₆₀R₆ complexes (M = Cr, Mo; R = H, Hal, CN), where R groups bordered one of the fullerene C₆₀ six-membered rings comprising the atoms to which metal atoms were coordinated.     

Optisch aktive N.N-bis[phosphinomethylen]-aminosäureester und deren molybdäncarbonyl-komplexe

Aminoacidesters and hydroxymethylphosphines form the title compounds, which react as bidentate ligands with Mo (CO)₆ to give the cyclic Mo (CO)₄ -complexes.