Triphenylphosphineoxide nitrosyl complexes of molybdenum

Summary The tetramethylthiourea (TMTU) complexes of cobalt(II) and nickel(II) halides have been studied in the solid state by electronic, i.r. and far i.r. spectroscopy and magnetochemically. The tetrahedral Co(TMTU)₂X₂ (X = Cl, Br, 1) and Ni(TMTU)₂X₂ (X = Cl, Br) complexes have normal magnetic moments, electronic spectra and crystal field parameters; Ni₂ (TMTU)₃I₄ is diamagnetic. The cobalt complexes have normal (CoX) and (CoX) vibrational frequencies. Ni(TMTU)₂Cl₂ and Ni₂(TMTU)₃I₄ have (NiX) frequencies corresponding to long or bridging Ni-X bonds, while Ni(TMTU)₂Br₂ has normal (NiBr) frequencies for terminal Ni-Br bonds. The (MS) frequencies are similar to those of cobalt(II) and nickel(II) complexes of other thioureas.     

Isocyanide complexes of molybdenum nitrosyl

Reaction of π-cyclopentadienylmolybdenum nitrosyl halide with CNR (R = alkyl) gives [(π-C₅H₅)Mo(NO)X₂(CNR)] (X = Br or I), [Mo(NO)(CNR)₅]X (X = I or PF₆) and [Mo(NO)(CNR)₄I]; treatment of [Mo(NO)(CNR)₅]I with R′NH₂ gives [Mo(NO)(CNR)₄ {C(NHR)(NHR′)}]I or [Mo(NO)(CNR)₄(NH₂R′)]I (R′ = alkyl) depending on temperature.     

Transition metal nitrosyl compounds,Part XXV1 Studies of some nitrosyl complexes of molybdenum and tungsten

Summary On u.v. irradiation, the dinitrosyldithiocarbamato M(NO)₂ (S2 CNR2 )2 (M = Mo or W) complexes are converted quantitatively into the mononitrosyl M(NO)(S₂CNR₂)₃ complexes. The tungsten complex exhibits nonrigid behaviour at high temperatures; the activation energy for this process has been determined and compared to that of the molybdenum analogue. The M(NO)₂ (MeCOCHCOMe)₂ and M(NO)₂ [(O)SCNR₂]₂ compounds have been prepared; these undergo conversion into uncharacterized nitrosyl derivatives upon irradiation. Cationic complexes of the type [M(NO)₂ (MeCN)₄]2+, [M(NO)₂ (MeCN)₃ X]+ and [M(NO)₂ (MeCN)₂ (MeCOCHCOMe)]+ have been prepared and their exchange with CD₃CN studied. Exchange occursvia a dissociative process and is stereospecific for [M(NO)₂ (MeCN)₄ ]2+ (M = Mo or W) and [M(NO)₂ (MeCN)₃ X]+ (M = MO, X = Cl; M = W, X = Br).     

Polymerization of epoxidized triglycerides with fluorosulfonic acid

The use of triglycerides as agri-based renewable raw materials for the development of new products is highly desirable in view of uncertain future petroleum prices. A new method of polymerizing epoxidized soybean oil has been devised with the use of fluorosulfonic acid. Depending on the reaction conditions, one can get a viscous oil or a solid as the reaction product. The reaction mechanism has been studied through a systematic examination of the fluorosulfonic acid-initiated reaction of epoxidized methyl oleate and epoxidized methyl linoleate. Through ¹³C NMR spectroscopy, the major species derived from fluorosulfonic acid-initiated polymerization of epoxidized soybean oil have been determined. The effects of temperature, initiator dosage, and reaction time have been studied and shown to affect the nature of polymer products obtained and the distribution of different chemical species present.     

Reaction of internal fluoroolefin oxides with fluorosulfonic acid

Conclusions Internal perfluoroolefin oxides react with fluorosulfonic acid to give perfluoroketones that contain a fluorosulfate group in the-position.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1878–1879, August, 1979.     

Cyclization of α-terpenols and their acetates by fluorosulfonic acid

It has been shown that the superacid cyclization of α-terpenols and their acetates takes place with structural selectivity and chemo- and stereospecificity and leads to cyclic isoprenoids with higher yields than the cyclization of the corresponding β-terpenols and their acetates.     

Half-sandwich cyclopentandienyl molybdenum and tungsten nitrosyl complexes containing bidentate sulfur ligands

Half-sandwich nitrosyl complexes Cp*M(NO)I2 (M = Mo, or W) react with dithiocarbamates (NaS2CNMe2 and NaS2CNEt2) in THF to form of complexes: Cp*Mo(NO)I (S2CNMe2) (1), Cp*Mo(NO)I(S2CNEt2) (2), Cp*W(NO)I(S2CNMe2) (3) and Cp*W(NO)I(S2CNEt2) (4) in high yields. Treatments of Cp*M(NO)I2 (M = Mo, W) or [CpMo(NO)I2]2 with phosphinodithioate (NaS2PMe2) and phosphorodithioate [(NH4)S2P(OMe)2] result in complexes: Cp*Mo(NO)I(S2PMe2) (5a), CpMo(NO)I (S2PMe2) (5b), Cp*Mo(NO)(S2PMe2)2 (6a), CpMo (NO) (S2PMe2)2 (6b) and Cp*Mo(NO)I[S2P(OMe)2] (7), Cp*W(NO)I(S2PMe2) (8), Cp*W(NO) I[S2P(OMe)]2 (9). Treatment of (5a) and (5b) with an excess of NaS2PMe2 gives (6a) and (6b). The complexes have been characterized by their elemental analyses, i.r., 1H, 13C-n.m.r. and by EI-MS spectrometry.     

Tungsten and molybdenum catalyst-mediated cyclisation of N-propargyl amides

Tungsten and molybdenum catalysts were employed to promote the cyclisation of N-propargylic amides to afford the corresponding oxazolines or oxazines via 5-exo-dig or 6-endo-dig mode.     

Electrocatalytic activity of bisalkoxide molybdenum nitrosyl complexes in the reduction of chloroform

Bis(alkoxy)tris(3,5-dimethylpyrazol-1-yl)hydroborato nitrosyl molybdenum complexes having redox potential values no less cathodic than −1.82 V vs. Fc⁺/Fc appeared to be efficient catalysts of chloroform electroreduction. The system, the great advantage of which is its controllable redox potential, is active only in dichloromethane and the presence of alcohols or hydroxy groups as ligands inhibits the catalysis.     

Ruthenium nitrosyl complexes in nitric acid solutions

Nine nitrosyl ruthenium complexes have been separated and identified in aqueous solutions of nitric acid. The separation method was low temperature, gradient elution, reverse phase partition chromatography using tri-n-butyl phosphate on a kiesel gel 60 support using ¹⁰⁶Ru labelled complexes in the nitric acid phase. The identification of the complexes was deduced from the relationships between the products of aquation and nitration and paper chromatography using both methyl-iso-propyl ketone and nitric acid-acetone elutions. The proportion of each complex at equilibrium in various concentrations of nitric acid have been measured. The rates of nitration in 10 M nitric acid, and of equation in 0.45 M nitric acid have been determined at 0°C.     

Tungsten(VI) and mixed tungsten,molybdenum(VI) complexes of tartaric acid

A number of studies of species formed in the tungsten(VI) oxide-R,R-(+)-tartaric acid-water system have been carried out(^1–3). While various species have been proposed, it is generally accepted that three main ones predominate. Two have tungsten: (+)-tartaric acid [(+)-tartH₄] ratios of 11 and the third has the same ratio of 12. This latter species cannot be that proposed by Avaloset al. ⁽³⁾ since both ligands in their structure would have to be present as unidentates.Recently we have shown⁽⁴⁾ that high resolution¹H and¹³C n.m.r. studies were particularly useful in delineating the complexes formed in aqueous solution in the analogous molybdenum(VI) system. Thus, we turned our attention to the corresponding tungsten(VI) complexes, especially in view of the controversy surrounding the nature of the species formed in aqueous solution with (+)-tartH₄. The results of our studies, presented below, indicate that only a few species are formed, and that these are quite analogous, as might be expected, to the previously described molybdenum(VI) species⁽⁴⁾. In addition we have observed the formation of a mixed dimeric species [MoWO⁴{(+)-tart}₂]^4–, whose structure is akin to the mono-metallic complexes, as well as the well-characterized antimony(III) and arsenic(III) dimers of (+)-tartH₄ ⁽⁵⁾.     

Theoretical modeling of electrochemical interactions in bimetallic molybdenum nitrosyl complexes incorporating saturated bridges

Hybrid B3LYP and non-hybrid OLYP DFT formalism has been applied to neutral and reduced forms of bimetallic hydrotris(3-methylpyrazol-1-yl)borato (Tp^3-Me) molybdenum nitrosyl complexes incorporating ethane-1,2-diolate bridges. Direct evidence for localization of an extra electron in mixed-valence compounds {16e:17e}⁻ is based on the analysis of electron density, energetic stabilization of asymmetric structures with an electron trapped on one Mo and the splitting of both calculated and experimental ν_NO stretching frequencies. Differences in the first and second electron affinities calculated in PCM solvent model have been successfully related to cyclic voltammetry measurements. Electronic interactions through saturated ethanediolato bridges are evidenced by the extent of spin density delocalization towards the second Mo center.     

Reaction of sulfur chlorides with hexafluoropropylene in the presence of fluorosulfonic and chlorosulfonic acid

Conclusions In the reaction of sulfur chlorides with hexafluoropropylene in the presence of halosulfonic acids products of conjugated electrophilic addition are produced. Bis[(-halosulfonyloxy)hexafluoroisopropyl] trisulfides are formed as a result of the reaction of 2-(chlorodithio)hexafluoropropyl halosulfates with halosulfonic acids.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2367–2372, October, 1988.For previous communications, see [1, 2].     

Tungsten and molybdenum phosphine hexahydrides: The first examples of nine coordination among mononuclear molybdenum complexes

An improved preparation and some reactions of WH₆(PMe₂Ph)₃ are described. This method has been extended to prepare the novel MoH₆ (PR₃)₃ compounds, the first mononuclear nine-coordinate molybdenum complexes.     

Protonation enthalpies in fluorosulfonic acid using ab initio self-consistent reaction field theory

Electrostatic solvation free energies were computed for several small neutral bases and their conjugate acids using a continuum solvation model called the self-consistent isodensity polarizable continuum model (SCIPCM). The solvation energies were computed at the restricted Hartree–Fock (RHF) and second-order Møller–Plesset (MP2) levels of theory, as well as with the Becke3–Lee–Yang–Parr (B3LYP) density functional theory, using the standard 6–31G** Gaussian basis set. The RHF solvation energies are similar to those computed at the correlated MP2 and B3LYP theoretical levels. A model for computing protonation enthalpies for neutral bases in fluorosulfonic acid solvent leads to the equation ΔH(B)=−PA(B)+ΔE_t(BH⁺)−ΔE_t(B)+β, where PA(B) is the gas phase proton affinity for base B, ΔE_t(BH⁺) is the SCIPCM solvation energy for the conjugate acid, and ΔE_t(B) is the solvation energy for the base. A fit to experimental values of ΔH(B) for 10 neutral bases (H₂O, MeOH, Me₂O, H₂S, MeSH, Me₂S, NH₃, MeNH₂, Me₂NH, and PH₃) gives β=238.4±2.9 kcal/mol when ΔΔE_t is computed using the 0.0004 e⋅bohr⁻³ isodensity surface for defining the solute cavity at the RHF/6–31G** level. The model predicts that for carbon monoxide ΔH(CO)=10 kcal/mol. Thus, protonation of CO is endothermic, and the conjugate acid HCO⁺ (formyl cation) behaves as a strong acid in fluorosulfonic acid. © 1998 John Wiley & Sons, Inc. J Comput Chem 19: 250–257, 1998