Reactivity of [HFe3(CO)11]−1 toward alkynes: II. Reactions with monosubstituted alkynes: from alkylidyne to acetylide ligands on a triiron unit

The reactions of monosubstituted alkynes (RCCH (R = C₆H₅, C₃H₇, C(O)CH₃ or C(O)OCH₃) with [P(C₆H₅)₄][HFe₃(CO)₁₁] have been studied. Depending on the reaction conditions the complexes [P(C₆H₅)₄][Fe₃(CO)₁₀(μ₃-CCH₂R)] (A) and [P(C₆H₅)₄][HFe₃(CO)₉(μ₃-CCHR)] (B) can be isolated. The two types of complexes are interrelated by the addition of (B → A) or loss (A → B) of carbon monoxide. In two cases (R = C₆H₅, C₃H₇) the transformation B → [P(C₆H₅)₄][Fe₃(CO)₉(μ₃-CCR)] has been observed in refluxing 2-methoxyethanol, and for these two alkynes all the transformations

have been observed on a triiron unit.     

Reaction of [Fe4(μ3-CCH3)(CO)12]− with alkynes: Ethylidyne-alkyne coupling on a tetranuclear iron cluster anion

The [Fe₄(μ₄-η³-C(CH₃)C(R)C(R′)(μ-CO)₂(CO)₉]⁻ cluster anions have been obtained by the reaction of the Fe₄(μ₃-CCH₃)(CO)₁₂⁻ anion with RCCR alkynes in boiling 3-pentanone. In the cases in which R = R′ = C₆H₅ or CH₃, and R = H, R′ = C₆H₅ or t-Bu, only one isomer has been detected. In the case in which R = CH₃, and R′ = C₆H₅, two isomers with the C(CH₃)C(C₆H₅)C(CH₃) and C(CH₃)C(CH₃)C(C₆H₅) fragments have been identified.     

A novel reaction of Os6(CO)18 with Me3NO; isolation and NMR study of the new hexaosmium cluster anion [HOs6(CO)17]−

In the absence of a ligand and in non-coordinating solvents, Os₆(CO)₁₈ racts with 2 equivalents of R₃No (R = Me, Et) to give the new hexaosmium cluster [HOs₆(CO)₁₇]⁻. Variable temperature ¹H and ¹³C NMR and ²D NMR. techniques have been used to investigate the structure of this anion and its dynamic behviour in solution. The mechanism of the novel reaction is discussed.     

A disulfide-bridged manganese carbonyl anion: synthesis,structure and reactivity of [Mn3(CO)10(μ3-S2)2]−

The reduction of Mn₂(CO)₇(μ-S₂), (1) with sodium amalgam in THF provided the new monoanion [Mn₃(CO)₁₀(μ₃-S₂)₂]⁻, (3) isolated in low yield as the [Ph₃PMe] salt. The reaction of Mn₄(CO)₁₅(μ₃-S₂)(μ₄-S₂), (2) with [Ph₃PMe]I provided the same salt [Ph₃PMe] [3] in a good yield, 68%. Anion 3 reacts [CpFe(CO)₂(acetone)]BF₄ to yield the neutral mixed metal complex CpFeMn₃(CO)₁₂(μ₃-S₂)(μ₄-S₂), (4). The structures of [Ph₃PMe] [3] and 4 were determined by single crystal X-ray diffraction analyses. The core of the structure of 3 consists of two [Mn(CO)₃] groups bridged by two disulfido ligands in a μ₂–η² fashion with an additional [Mn(CO)₄] group that bridges the two disulfido ligands. The CpFe(CO)₂ group in 4 is bonded to a sulfur atom of one of the two disulfido ligands of the anionic grouping of 3.     

The reaction of CpWMe(CO)3 with LiEt3BH. Formation of the formyl complex trans-[CpWMe(CHO)(CO)2]− and the (hydrido)(acyl) complex trans-[CpWH(COMe)(CO)2]−

Addition of LiEt₃BH to CpWMe(CO)₃ results in consecutive formation of trans-[CpWMe(CHO)(CO)₂]⁻ (some of which exists in solution as two rotamers of a BEt₃ adduct) and trans[CpWH(COMe)(CO)₂]⁻. Reaction of the latter with CHI₃ and subsequent treatment of the product with either (i) Me₃SiCl, followed by filtration through SiO₂ or (ii) Me₃OBF₄ gives hydroxy- or methoxy-carbenes CpWI[C(OR)Me](CO)₂ (R H or Me), respectively.     

Cleavage of B−C bonds and Anion [PhBH3]− Formation in the Reaction of the Yb(II) Hydride Complex with BPh3

Russian Journal of Coordination Chemistry - The reaction of the amidinatehydride complex of divalent ytterbium [(Amd)YbII(μ2-H)]2 (Amd is {tert-BuC(NC6H3-iso-Pr2-2,6)2}) with BPh3 proceeds...     

Hydrido-Carbonyl Rhenium Clusters with a Square Geometry of the Metal Core. Synthesis and X-Ray Characterization of the Novel [Re4(μ-H)3(CO)16]− Anion

Three and tetranuclear ring clusters have been obtained by treatment of [Re₂(CO)₈(THF)₂] with carbonyl-rhenates containing two terminal hydrides. The reaction with [ReH₂(CO)₄]^- provided a selective route to the previously known [Re₃(-H)₂(CO)₁₂]^- triangular cluster anion 1. The reaction with [Re₂H₂(-H)(CO)₈]^- gave the novel [Re₄(-H)₃(CO)₁₆]^- anion 2, containing a rare example of a puckered-square metal cluster. Protonation of 1 is known to afford the neutral [Re₃(-H)₃(CO)₁₂] species 3. Analogously the reaction of 2 with a strong acid afforded the previously known square metal clusters [Re₄(-H)₄(CO)₁₆] 4. The reaction could not be reversed by treatment with bases. Photolysis of 4 gave the unsaturated complex [Re₂(-H)₂(CO)₈] 5: this is the reverse of the dimerization reaction, that in THF at room temperature produces 4 from 5. Thermal treatment (reflux in cyclohexane for 24 h) left 4 almost unchanged. A single crystal X-ray analysis of [NEt₄]2 showed a s/e/s/s (e=eclipsed, s=staggered) conformation of the Re(CO)₄ units, leading to a puckered geometry of the ring, at variance with the square-planar geometry of 4 (all eclipsed). Two of the three hydrides of 2 have been located as bridging the Re–Re edges from inside the metal ring, as previously observed in 4. Density functional computations indicated a puckered conformation as the most stable for both 2 and 4, with very low activation energies for ring inversion (6.6 and 2.2 kcal·mol^-1, respectively), but ruled out solid state fluxionality for 4, whose observed planar geometry must be attributed to packing stabilization.     

A simple new general synthesis of macrocyclic ketones: A new entry to the synthesis of exaltone and (±)-muscone

We describe an efficient new synthesis of 15-membered cyclic ketones, exaltone and (±)-muscone, based on a three-carbon annelation of cyclic ketones followed by the regioselective radical cleavage of the fused bond of the resulting bicyclic systems.     

Reaction of the heteronuclear cluster RuOs3(μ-H)2(CO)13 with azulenes

Reaction of the heteronuclear cluster RuOs₃(μ-H)₂(CO)₁₃ (1) with azulene under thermal activation afforded the novel clusters RuOs₃(μ-H)(CO)₉(μ₃,η⁵:η²:η²-C₁₀H₉) (3) and Ru₂Os₃(μ-H)₂(CO)₁₃(μ-CO)(μ₃,η⁵:σ²-C₁₀H₈) (5a), with 4,6,8-trimethylazulene to give RuOs₃(μ-H)(CO)₈(μ-CO)(μ,η⁵:η⁴-C₁₀H₆Me₃) (4) and Ru₂Os₃(μ-H)₂(CO)₁₃(μ-CO)(μ₃,η⁵:σ²-C₁₀H₅Me₃) (5b), and with guaiazulene to give Ru₂Os₃(CO)₁₁(μ₃,η⁵:η³:η³-C₁₀H₅Me₂ⁱPr) (6), respectively. In 3–5, cluster-to-ligand hydrogen transfer appears to have taken place, with the organic moiety capping a trimetallic face in 3, bridging a metal–metal bond in 4 and via a μ₃,η⁵:σ² bonding mode in 5a and 5b. Cluster 6 contains a trigonal bipyramidal metal framework with the guaiazulene ligand over a triangular metal face. All five clusters have been completely characterised, including by single-crystal X-ray diffraction analysis.     

A new facile synthesis of α-dicarbonyl compounds by oxidation of alkynes with Mo(VI) peroxocomplex promoted by mercuric acetate

Mercuric acetate promoted oxidation of diaryl-, dialkyl-, and aralkyl alkynes with (HMPA)MoO(O₂)₂ in 1,2-dichloroethane affords the corresponding α-diketones in good yields. Likewise, terminal alkynes can be converted into α-ketoaldehydes in excellent yields by using the same oxidizing system.     

Origin of the different reactivity of the high-valent coinage-metal complexes [RCuiiiMe3]− and [RAgiiiMe3]− (R=allyl)**

High-valent tetraalkylcuprates(iii ) and -argentates(iii ) are key intermediates of copper- and silver-mediated C−C coupling reactions. Here, we investigate the previously reported contrasting reactivity of [RMⁱⁱⁱ Me₃]⁻ complexes (M=Cu, Ag and R=allyl) with energy-dependent collision-induced dissociation experiments, advanced quantum-chemical calculations and kinetic computations. The gas-phase fragmentation experiments confirmed the preferred formation of the [RCuMe]⁻ anion upon collisional activation of the cuprate(iii ) species, consistent with a homo-coupling reaction, whereas the silver analogue primarily yielded [AgMe₂]⁻, consistent with a cross-coupling reaction. For both complexes, density functional theory calculations identified one mechanism for homo coupling and four different ones for cross coupling. Of these pathways, an unprecedented concerted outer-sphere cross coupling is of particular interest, because it can explain the formation of [AgMe₂]⁻ from the argentate(iii ) species. Remarkably, the different C−C coupling propensities of the two [RMⁱⁱⁱ Me₃]⁻ complexes become only apparent when properly accounting for the multi-configurational character of the wave function for the key transition state of [RAgMe₃]⁻. Backed by the obtained detailed mechanistic insight for the gas-phase reactions, we propose that the previously observed cross-coupling reaction of the silver complex in solution proceeds via the outer-sphere mechanism.     

Reaction of [VO(OPr)3] with hexamethyldisylthiane in the presence of β-diketones

The reaction of [VO(OPr)₃] (Pr is n-propyl) with hexamethyldisylthiane Me₃SiSSiMe₃ in the presence of β-diketones (acetylacetone (HAcac), hexafluoroacetylacetone (Hfac), and dipivaloylmethane (Dpm)), is studied. In all cases, vanadium(IV) and vanadium(III) β-diketonate complexes of different types are formed. New crystalline modification [V(Acac)₃] is obtained in the reaction with HAcac. The mixedligand vanadium(III) complex of the composition [V₂(Hfac)₂(μ-OPr)]₂ is formed with Hfac. In the presence of Dpm, the known vanadium(IV) complex [V₂O₂(Dpm)₂(μ-OPr)₂] is obtained in which two vanadyl groups VO²⁺ are linked by two bridging propoxy groups. The structures of all products are determined by X-ray diffraction analysis.     

β-Trimethylsilylethanesulfonyl chloride (SES-Cl): A new reagent for protection of amines

The title compound, easily prepared in two steps from vinyltrimethylsilane, is a useful reagent for the protection of primary and secondary amines as their sulfonamides, which are cleaved by fluoride ion.     

Reactions of the unsaturated anion [Re3(μ-H)4(CO)10]− with phosphines. Synthesis of the anions [Re3(μ-H)2(CO)10(PR3)2]−, and crystal structure of [NEt4][Re3(μ-H)2(CO)10(PPh3)2]

The reaction of the unsaturated cluster anion [Re₃(μ-H)₄(CO)₁₀]⁻ with tertiary phosphines at room temperature results in the substitution of two hydride ligands (eliminated as H₂) by two PR₃ ligands, leading to saturated [Re₃(μ-H)₂(CO)₁₀-(PR₃)₂]⁻ compounds. A single crystal X-ray diffraction study of the PPh₃ derivative revealed that the two phosphines occupy non-equivalent equatorial coordination sites on the triangular cluster. The rate of the reaction greatly increases with increase of the basicity of the phosphine.     

DMF-dimethyl sulfate as a new reagent for the synthesis of β-lactams

A number of 2-azetidinones were synthesized in good to excellent yields by a novel reaction between Schiff bases, substituted acetic acids and alkoxymethylene-N,N-dimethyliminium salts, the adduct formed from DMF and O-alkylating agents. The advantages of this new method are mild reaction conditions, low cost, avoiding the use of chlorinating agents and easy purification of the products. The best results were obtained when DMF and dimethyl sulfate were used at room temperature.     

Reaction of 1-tosyl-2,2-dichloroenamines with the Lawesson’s reagent

In the reaction of the available 1-tosyl-2,2-dihlorenamides with the Lawesson??s reagent the derivatives of 4-tosyl-1,3-thiazole were shown to form containing a labile chlorine atom at the C⁵ position. This fact was used for the synthesis of a number of the previously unknown bifunctionally substituted 4,5-thiazoles.     

Reaction of N,N-disubstituted perfluoroalkanethioamides with trialkyl phosphites. A new method for the synthesis of polyfluorinated α-aminophosphonates

The first examples of the reactions of perfluoroalkanethiocarboxylic acid amides and trialkyl phosphites are presented. The reactions are shown to be dependent on the perfluoroalkyl chain length and the presence of proton-donating reagents. New fluorinated α-aminophosphonate derivatives are obtained in moderate to good yields.     

Transformations of [Au(CN)2]− at the contact with activated carbon surface

We have studied the processes occurring when alkaline aqueous solution of Na[Au(CN)₂] is brought in contact with activated carbon surface. It has been shown that the adsorption of the gold cyanide complex occurs via several independent routes, one of them being accompanied with the partial breakdown of the inner sphere of the compound and free cyanide ions release into the solution. The latter process decreases the gold recovery by aqueous NaOH during the high-temperature (150°C) desorption. A prolonged storage of the adsorbent saturated with [Au(CN)₂]^? in air produces a similar result. The reasons of the observed phenomena have been discussed.