Alkylidyne-alkylidyne and alkylidyne-carbonyl coupling on the triosmium framework

Hydrogenation of Os₃(CO)₉ (μ₃-CPh)(μ₃-COMe) (1) at one atmosphere results in alkylidyne-alkylidyne coupling, forming the alkyne complex (μ-H)₂Os₃(CO)₉(μ₃, η²-C₂(OMe)Ph) (3). Reduction of 1 by two equiv. of sodium benzophenone ketyl, followed by protonation with tetrafluoroboric acid, yields the phenylacetylide complex(μ-H)OS₃(CO)₉(μ₃,η²-CCHPh) (4). Sequential reduction/protonation involving (μ-H)OS₃(CO)₁₀(μ₃-CPh) (2) also generates 4, apparently via benzylidyne-carbonyl coupling.     

Synthesis and characterisation of linked triosmium clusters using the bis(diphenylphosphino)acetylene ligand

The reaction of Os₃(CO)₁₁(NCMe) with bis(diphenylphosphino)acetylene (dppa) at room temperature affords [Os₃(CO)₁₁]₂(dppa) (1) in good yield, while Os₃(CO)₁₀(NCMe)₂ with an excess of dppa gives [Os₃(CO)₁₀(dppa)]₃ (2) and [Os₃(CO)₁₀(dppa)]₄ (3) in moderate yields. The structure of 1 has been determined by a single crystal X-ray diffraction study.     

6-alkyl and 5,6-dialkyl-2-methoxy-4(3H)- pyrimidinones in the transformations of pyrimidines—2: Synthesis and conversion into alkyluracils and 2-alkoxy-4(3H)-pyrimidinones

The synthesis of 6-alkyl and 5,6-dialkyl-2-methoxy-4(3H)-pyrimidinones 3 is described. Their versatility to be transformed into 6-alkyl and 5,6-dialkyluracils 4(a-h), 6-alkyl and 5,6-dialkyl-3-methyluracils 7(a,e,f) and 6-alkyl and 5,6-dialkyl-2-alkoxy-4(3H)-pyrimidinones 5(a-i) is also shown.     

Directed ortho metalation reactions. Synthesis of the naturally-occurring benz[a]anthraquinones X-14881 C and ochromycinone

The synthesis of the benz[a]anthraquinone natural products X-14881 C (1c) and ochromycinone (1a) via an aromatic directed metalation strategy (Scheme 1) is described.     

The pyrolysis of 3-oxa-11-chloro-eicosafluoroundecane sulfinate and sulfonate salts

The thermal decomposition of sodium 3-oxa-11-chloro-eicosafluoroundecane sulfinate (1) and potassium 3-oxa-11-chloroeicosafluoroundecane sulfonate (2) were studied. 7-Chlorotridecafluoroheptene-1 (3), 1-hydro-7-chloro-tetradecafluoroheptane (4), 1-hydro-3-oxa-11-chloro-eicosafluoroundecane (5), methyl 8-chloro-tetradecafluorooctanate (6), and methyl 3-oxa-11 - chloro - octadecafluoroundecanate (7) were isolated and characterized when compound 1 was pyrolyzed and then reacted with methanol. However, only 8-chloro-tetradecafluorooctanoic acid and its methyl ester were obtained in high yield when compound 2 was subjected to pyrolysis. A possible mechanism was proposed.     

Isolation and X-ray structure determination of Ru4(CO)12(C6H6O), a precatalyst for the transfer hydrogenation of cyclohex-1-en-2-one

Ru₄(CO)₁₂(C₆H₆O) (1) and Ru₃(CO)₁₀(C₆H₈O) (2) have been obtained from the reaction of Ru₃(CO)₁₂ with cyclohex-1-en-2-one; 1 has been characterized by an X-ray structure determination. Both 1 and 2 have been found to be active precatalysts for the transfer hydrogenation of cyclohex-1-en-2-one.     

Proximity effects in 1-azaspirocyclo[5.5]undecanes. X-ray structure determination of a diol derivative

Neighbouring group participation is used to control bromination of the alkene (1) to give the bromo-acetate (3) which is converted into the diol (6a) [characterised by X-ray structure determination of the cyclic carbamate (8)] and the epoxide (2).     

Metal cluster-induced desulphurization of N-(p-methoxybenzoyl)-S-benzoylsulphenamide. Crystal and molecular structures of [Os6(CO)20(μ4-S)(MeCN)]

Reaction of N-(p-methoxybenzoyl)-S-benzoylsulphenamide1 with [Os₃(CO)₁₀(MeCN)₂] at room temperature gives Os₃(CO)₁₀(μ₃-S)]2 and [Os₆(CO)₂₀(μ₄-S)(MeCN)]3 in moderate yield. The crystal structure of 3 has been determined. Complex 2 is an intermediate in the formation of 3. Complex 3 undergoes dissociation of CO to give [Os₆(CO)₁₉(μ₃-S)] and [Os₅(CO)₁₅(μ₄-S)].     

Synthesis,characterization, and reactivity of a novel ruthenium carbonyl cluster containing tri-O-benzyl-d-glucal as a chiral carbohydrate ligand

A chiral carbohydrate ligand 3,4,6-tri-O-benzyl-d-glucal (L) reacts with the cluster triruthenium dodecacarbonyl Ru₃(CO)₁₂ giving a novel chiral cluster Ru₃(μ-H)₂(CO)₉(L-2H) (I) that shows fluxional behavior at room temperature. The reaction of Ru₃(μ-H)₂(CO)₉(L-2H) (I) with triphenylphosphine and diphenylphosphinoethane (dppe) gives two new clusters Ru₃(μ-H)₂(CO)₇(L-2H)(PPh₃)₂ (II) and Ru₃(μ-H)₂(CO)₇(L-2H)(dppe) (III). The new compounds I, II and III have been characterized by a combination of elemental analysis, mass spectrometry, infrared and variable temperature NMR spectroscopy.     

Design,synthesis, characterization,and antimicrobial evaluation of some new pyridine and chromene derivatives containing Lidocaine analogue

In an attempt to find a new class of antimicrobial agents, a series 2-pyridinone and 2-iminochromene derivatives containing Lidocaine analogue were designed and synthesized. The 2-pyridinone derivatives (3), (4), and (6) were obtained through the cyclocondensation of 2-cyano-N-(2,6-dimethylphenyl)-acetamide (2) with 1,3-dicarbonyl compounds and/or ternary condensation of (2), aromatic aldehyde, and malononitrile. Also, a series of 2-iminochromene derivatives (7–9) were synthesized through the condensation reaction of cyanoacetamide derivative (2) with salicylaldehyde derivatives. The structure of the new compounds were confirmed based on elemental analysis and spectral data. These compounds were screened for their antibacterial and antifungal activity The minimal inhibitory concentration (MIC) (µg/mL) of the most active (4), (5b), and (8) derivatives were determined. The MIC values between 7.81 and 31.26 µg/mL against bacterial species for (8) derivative, and upon comparison to tetracycline exhibited a positive control MIC (31.26–62.6 µg/mL). Besides, the activity against C. albicans (ATCC 1023) showed a MIC value of 15.63 µg/mL, which is similar to that of Amphotericin B.     

Organic carboxylate anions effect on the structures of a series of Mn(II) complexes based on 2-phenylimidazo[4,5-f]1,10-phenanthroline ligand

In our efforts to tune the structures of Mn(II) complexes by selection of organic carboxylic acid ligands, six new complexes [Mn(PIP)₂Cl₂] (1), [Mn(PIP)₂(4,4′-bpdc)(H₂O)]·2H₂O (2), [Mn(PIP)₂(1,4-bdc)] (3), [Mn(PIP)(1,3-bdc)] (4), [Mn(PIP)₂(2,6-napdc)]·H₂O (5), and [Mn(PIP)(1,4-napdc)]·H₂O (6) were obtained, where PIP=2-phenylimidazo[4,5-f]1,10-phenanthroline, 4,4′-H₂bpdc=biphenyl-4,4′-dicarboxylic acid, 1,4-H₂bdc=benzene-1,4-dicarboxylic acid, 1,3-H₂bdc=benzene-1,3-dicarboxylic acid, 2,6-H₂napdc=2,6-naphthalenedicarboxylic acid, 1,4-H₂napdc=1,4-naphthalenedicarboxylic acid. All complexes have been structurally characterized by IR, elemental analyses, and single crystal X-ray diffraction. Structural analyses show that complexes 1 and 2 possess mononuclear structures, complexes 3, 4, and 5 feature chain structures, and complex 6 exhibits a 2D (4,4) network. The structural difference of 1–6 indicates that organic carboxylate anions play important roles in the formation of such coordination architectures. Furthermore, the thermal properties of complexes 1–6 and the magnetic property of 4 have been investigated.     

Investigation of the zinc(II) acetylacetonate/benzotriazole reaction system in the presence of bridging N,N′-ligands: Pentanuclear, enneanuclear and polymeric complexes

The reaction of Zn(acac)₂ with btaH (1,2,3-benzotriazole) in dmf yielded the pentanuclear complex [Zn₅(bta)₆(acac)₄(dmf)]·dmf (1·dmf). In the presence of pyrazine, the pentanuclear [Zn₅(bta)₆(acac)₄(dmf)]·3.7dmf (2·3.7dmf) and enneanuclear [Zn₉(bta)₁₂(acac)₆]·6dmf (3·6dmf) complexes were formed, whereas in the presence of 4,4′-bpy the 1D coordination polymer [Zn(acac)₂(4,4′-bpy)]_n (4) was isolated. The molecular structures of 1·dmf and 2·3.7dmf reveal that the [Zn₅] clusters consist of four Zn^II ions which span the corners of a tetrahedron and the fifth resides at its centre. The molecular structure of 3·6dmf reveals that the [Zn₉] clusters consist of two corner sharing tetrahedra and the structure can be described as the addition of two [Zn₅] clusters of 1·dmf and/or 2·3.7dmf followed by the simultaneous abstraction of [Zn(acac)₂] and dmf molecules; this alternative was accomplished by recrystallization of 1·dmf from dmf which yielded 3·6dmf. Each of the μ₃-κN:κN′:κN′′ benzotriazolate ligands in 1·dmf, 2·3.7dmf and 3·6dmf spans an edge of the tetrahedron. The molecular structure of 4 reveals mononuclear [Zn(acac)₂] units bridged via 4,4′-bpy molecules to 1D coordination polymer. Characteristic IR bands of the four complexes are discussed in terms of the coordination modes of the ligands and known structures.     

Diiron propanedithiolate complex bearing the pyridyl-functionalized phosphine ligand axially coordinated to a photosensitizer zinc tetraphenylporphyrin

Treatment of the starting material (μ-PDT)Fe₂(CO)₆ (PDT = SCH₂CH₂CH₂S) with 4-diphenylphosphinoaminopyridine (PyNHPPh₂) in the presence of the decarbonylating agent Me₃NO·2H₂O afforded (μ-PDT)Fe₂(CO)₅(PyNHPPh₂) (1) in 56% yield. Further treatment of 1 with Zinc tetraphenylporphyrin (ZnTPP) yielded the target light-driven model compound (μ-PDT)Fe₂(CO)₅(PyNHPPh₂)(ZnTPP) (2) in 94% yield. The new complexes 1 and 2 were characterized by elemental analysis, NMR, IR, and X-ray crystallography. The molecular structure of 2 revealed its precursor 1 and a photosensitizer ZnTPP joined together through axial coordination. Furthermore, the fluorescence emission spectra and electrochemistry were also investigated.     

New Ru3(CO)12 derivatives with bulky diphosphine ligands: synthesis,structure and catalytic potential for olefin hydroformylation

The diphosphine clusters Ru₃(CO)₁₀(dcpm) (1) and Ru₃(CO)₁₀(F-dppe) (2) as well as the bis(diphosphine) clusters Ru₃(CO)₈(dcpm)₂ (3) and Ru₃(CO)₈(F-dppe)₂ (4) have been synthesised from Ru₃(CO)₁₂ and the bulky diphosphines 1,2-bis[bis(pentafluorophenyl)phosphino]ethane (F-dppe) and bis(dicyclohexylphosphino)methane (dcpm). While the single-crystal X-ray structure analyses of 1, 2 and 3 show the expected μ₂-η² coordination of the diphosphine ligands, that of 4 reveals an unusual structure with one μ₂-η²-diphosphine and one μ₁-η²-diphosphine ligand. The clusters 1–4 catalyse the hydroformylation of ethylene and propylene to give the corresponding aldehydes, 2 showing higher activities than those observed for Ru₃(CO)₁₂ and Ru₃(CO)₁₀(dppe).     

The formation of iron carbonyl radical anions in the reactions of iron carbonyls with trimethylamine N-oxide

The interaction of iron carbonyls, Fe(CO)₅, Fe₂(CO)₉ and Fe₃(CO)₁₂ with Me₃NO occurs according to a one-electron redox-disproportionation scheme giving rise to iron carbonyl radical anions: Fe₂(CO)₈^·− (1), Fe₃(CO)₁₂^·− (2), Fe₃(CO)₁₁^·− (3) and Fe₄(CO)₁₃^·− (4). The role of Me₃NO, inducing CO-substitution, consists of the generation of reactive 17-electron species with a labile coordination sphere in which the substitution for other ligands occurs, resulting from fast ligand and electron exchange in the confines of the ETC-reaction.     

Synthetic studies of the reaction between aldehydes and the triosmium cluster [Os3(CO)10(NCMe)2]

The reaction of [Os₃(CO)₁₀(NCMe)₂] (1) with aldehydes in refluxing cyclohexane affords the metal clusters [Os₃(CO)₁₀(μ-H)(COR)] (2, R = Me, Ph, CH₂Ph or C₆H₁₃) in ca. 50% yield. The compound 2 (R = CH₂Ph) undergoes hydrogenation under pressure to give the corresponding alcohol, while decarbonylation occurs in the presence of Me₃NO to give the Me₃N-substituted derivative [Os₃(CO)₉(NMe₃)(μ-H)(COCH₂Ph)] in 90% yield.     

New triosmium metal clusters derived from the reactions between [Os3(CO)10(NCMe)2] and amides

Triosmium clusters of the type [Os₃(CO)₁₀(μ-H)(NHCOR)] (1; R = H, Me, Ph, Et or Pr) are formed in high yields form the reaction of [Os₃(CO)₁₀(NCMe)₂] (2) with amides. The nature of the products formed from thermolysis of 1 depend on the group, R.     

Real light emitter in the bioluminescence of the calcium-activated photoproteins aequorin and obelin: light emission from the singlet-excited state of coelenteramide phenolate anion in a contact ion pair

Fluorescence of the phenolate anion (3(O)⁻) and the amide anion (5(N)⁻) of coelenteramide analogues in ion pairs with various counter cations was systematically investigated to elucidate the ionic structure of the light emitter in the bioluminescence of the calcium-activated photoproteins aequorin and obelin. The fluorescent properties of 3(O)⁻ in an ion pair with a conjugate acid of an organic base (BASE-H⁺) were varied depending on the structural variation of the ion pair and the solvent polarity. In particular, the fluorescence of 3(O)⁻ in the ion pair with the conjugate acid of n-butylamine (NBA-H⁺) indicates that the singlet-excited state of 3(O)⁻ (¹3(O)^−∗) and NBA-H⁺ make a contact ion pair in which the fluorescence emission maxima of 3(O)⁻ is sensitive to the solvent polarity and the fluorescence quantum yields of 3(O)⁻ increase in a less polar solvent. The results also confirm that ¹3(O)^−∗ is a twisted intramolecular charge transfer state. By contrast, the fluorescence of 5(N)⁻ in an ion pair depends little on the BASE-H⁺ or the solvent polarity. Based on these results, we conclude that the light emitter in aequorin and obelin bioluminescences is the singlet-excited state of coelenteramide phenolate anion 2(O)⁻ (¹2(O)^−∗) in a contact ion pair with an imidazolium side chain of a histidine residue, which is located at the less polar active sites of the photoproteins. We also propose a mechanism for the bioluminescence reaction, including the chemiexcitation process to give ¹2(O)^−∗.     

Synthetic Connections to the aromatic directed metalation reaction. Radical-induced cyclization to substituted benzofurans,benzopyrans, and furopyridines

The $\text{ortho}$-iodoaryl allyl ethers 2, derived from 1 via the aromatic directed metalation protocol, undergo tributyl tin hydride-induced heteroring annelation to lead to unusually substituted benzofuran (3) and benzopyran, and furopyridine derivatives (Table).     

Übergangsmetall-heteroallen-komplexe XVII .Reaktionen des aza-allyl-komplexes (ketenimin)Fe2(CO)6 mit phosphanen

The aza-allyl complex (ketene imine)Fe₂(CO)₆ (3a) reacts with phosphanes PR₃ to give substitution products of the type (ketene imine)Fe₂(CO)₅PR₃ (4a,b). In addition, the phosphane PMe₃ yields a ferrole complex (5). Phosphites react with complex 3a to form mono- and di-substitution products (ketene imine)- Fe₂(CO)₅P(OR)₃ (4c,d) and (ketene imine)Fe₂(CO)₄(P(OR)₃)₂ (6). Diphosphanes yield substituted complexes of type (ketene imine)Fe₂(CO)₄(μ-Ph₂P ^⌢ PPh₂) (7). The structures of (ketene imine)Fe₂(CO)₅PMe₃ (4a), the ferrole complex 5, and (ketene imine)Fe₂(CO)₄(ν-Ph₂PCH₂CH₂PPh₂) (7b) were determined by X-ray analysis.