Protein modeling and molecular dynamics simulation of the two novel surfactant proteins SP-G and SP-H

The prospects of a control for a novel gallium nitride pseudo-halide vapor phase epitaxy (PHVPE) with HCN were thoroughly analyzed for hydrocarbons–NH₃–Ga gas phase on the basis of quantum chemical investigation with DFT (B3LYP, B3LYP with D3 empirical correction on dispersion interaction) and ab-initio (CASSCF, coupled clusters, and multireference configuration interaction including MRCI+Q) methods. The computational screening of reactions for different hydrocarbons (CH₄, C₂H₆, C₃H₈, C₂H₄, and C₂H₂) as readily available carbon precursors for HCN formation, potential chemical transport agents, and for controlled carbon doping of deposited GaN was carried out with the B3LYP method in conjunction with basis sets up to aug-cc-pVTZ. The gas phase intermediates for the reactions in the Ga-hydrocarbon systems were predicted at different theory levels. The located π-complexes Ga…C₂H₂ and Ga…C₂H₄ were studied to determine a probable catalytic activity in reactions with NH₃. A limited influence of the carbon-containing atmosphere was exhibited for the carbon doping of GaN crystal in the conventional GaN chemical vapor deposition (CVD) process with hydrocarbons injected in the gas phase. Our results provide a basis for experimental studies of GaN crystal growth with C₂H₄ and C₂H₂ as auxiliary carbon reagents for the Ga-NH₃ and Ga-C-NH₃ CVD systems and prerequisites for reactor design to enhance and control the PHVPE process through the HCN synthesis.     

Biomass Pyrolysis in an Argon/Hydrogen Plasma Reactor

This paper presents the experimental results of biomass pyrolysis in a laboratory argon/hydrogen plasma reactor. The samples tested were wood and rice husk. The gaseous product was found to contain mainly H₂, CO, C₂H₂ and CH₄. The conversion of carbon and oxygen from the biomass feed to gaseous product can reach up to 79 % and 72 %, respectively. The results indicate that plasma pyrolysis of biomass may be a useful way for gaseous fuel production.     

Carbon and energy yields in prebiotic syntheses using atmospheres containing CH4, CO and CO2

Yields based on carbon are usually reported in prebiotic experiments, while energy yields (moles cal^–1) are more useful in estimating the yields of products that would have been obtained from the primitive atmosphere of the earth. Energy yields for the synthesis of HCN and H₂CO from a spark discharge were determined for various mixtures of CH₄, CO, CO₂, H₂, H₂O, N₂ and NH₃. The maximum yields of HCN and H₂CO from CH₄, CO, and CO₂ as carbon sources are about 4×10^–8 moles cal^–1.     

Mechanism for the Coupled Photochemistry of Ammonia and Acetylene: Implications for Giant Planets,Comets and Interstellar Organic Synthesis

Laboratory studies provide a fundamental understanding of photochemical processes in planetary atmospheres. Photochemical reactions taking place on giant planets like Jupiter and possibly comets and the interstellar medium are the subject of this research. Reaction pathways are proposed for the coupled photochemistry of NH₃ (ammonia) and C₂H₂ (acetylene) within the context Jupiter’s atmosphere. We then extend the discussion to the Great Red Spot, Extra-Solar Giant Planets, Comets and Interstellar Organic Synthesis. Reaction rates in the form of quantum yields were measured for the decomposition of reactants and the formation of products and stable intermediates: HCN (hydrogen cyanide), CH₃CN (acetonitrile), CH₃CH = N-N = CHCH₃ (acetaldazine), CH₃CH = N-NH₂ (acetaldehyde hydrazone), C₂H₅NH₂ (ethylamine), CH₃NH₂ (methylamine) and C₂H₄ (ethene) in the photolysis of NH₃/C₂H₂ mixtures. Some of these compounds, formed in our investigation of pathways for HCN synthesis, were not encountered previously in observational, theoretical or laboratory photochemical studies. The quantum yields obtained allowed for the formulation of a reaction mechanism that attempts to explain the observed results under varying experimental conditions. In general, the results of this work are consistent with the initial observations of Ferris and Ishikawa (1988). However, their proposed reaction pathway which centers on the photolysis of CH₃CH = N-N = CHCH₃ does not explain all of the results obtained in this study. The formation of CH₃CH = N-N = CHCH₃ by a radical combination reaction of CH₃CH = N? was shown in this work to be inconsistent with other experiments where the CH₃CH = N? radical is thought to form but where no CH₃CH = N-N = CHCH₃ was detected. The importance of the role of H atom abstraction reactions was demonstrated and an alternative pathway for CH₃CH = N-N = CHCH₃ formation involving nucleophilic reaction between N₂H₄ and CH₃CH = NH is advanced.     

Far UV irradiation of model prebiotic atmospheres

UV light has been the most important energy source on the primitive Earth. However, very few experiments have been performed to test directly the possible role of this energy source on the chemical evolution of the primitive atmosphere, mainly on account of experimental difficulties. Experiments are generally performed with other excitations, mainly electric discharge, and it is frequently assumed that UV irradiation would give similar results.As theoretical considerations make this assumption questionable, direct experimental controls have been undertaken: Model primitive atmospheres have been submitted to 147 nm UV light and the gaseous phase has been analysed. Preliminary qualitative results concerning CH₄–NH₃ atmospheres are reported.Irradiation of pure CH₄ gives rise to the synthesis of a large number of hydrocarbons, mainly saturated hydrocarbons but including also unsaturated ones as, C₂H₂, C₂H₄, C₃H₆, C₃H₄. These insaturated hydrocarbons are synthetized at a very low rate when ammonia is present in the medium.Irradiations of CH₄–NH₃ mixtures give rise, in addition to hydrocarbons, to important amounts of HCN (about 0.1%) and to lesser amounts of CH₃CN and C₂H₅CN. No unsaturated nitriles such as acrylonitrile and cyanoacetylene have been detected. Search for amines is in progress.These results evidence that UV irradiation may contribute largely to synthesis of HCN in CH₄–NH₃ atmospheres and, consequently to the synthesis of many biochemical compounds that can be derivated from HCN. However, synthesis of other compounds, such as pyrimidines, which can derivate from other nitriles, such as cyanoacetylene, cannot be initiated only by UV light, contrary to electric discharges. In addition, if electric discharges are very efficient for synthesis of nitriles in CH₄–N₂ atmospheres, there is not yet evidence that UV light is able to do so.Presented at the 2nd ISSOL Meeting and the 5th ICOL in Kyoto, 5–10 April, 1977.     

Energy yields for hydrogen cyanide and formaldehyde syntheses: The hcn and amino acid concentrations in the primitive ocean

Prebiotic electric discharge and ultraviolet light experiments are usually reported in terms of carbon yields and involve a large input of energy to maximize yields. Experiments using lower energy inputs are more realistic prebiotic models and give energy yields which can be used to estimate the relative importance of the different energy sources on the primitive earth. Simulated prebiotic atmospheres containing either CH₄, CO or CO₂ with N₂, H₂O and variable amounts of H₂ were subjected to the spark from a high frequency Tesla coil. The energy yields for the synthesis of HCN and H₂CO were estimated. CH₄ mixtures give the highest yields of HCN while H₂CO is most efficiently produced with the CO mixtures. These results are a model for atmospheric corona discharges, which are more abundant than lightning and different in character. Preliminary experiments using artificial lightning are also reported. The energy yields from these experiments combined with the corona discharge available on the earth, allows a yearly production rate to be estimated. These are compared with other experiments and model calculations. From these production rates of HCN (e.g. 100 nmoles cm⁻² yr⁻¹) and the experimental hydrolysis rates, the steady state concentration in the primitive ocean can be calculated (e.g., 4 × 10⁻⁶ M at pH 8 and 0°). A steady state amino acid concentration of 3 × 10⁻⁴ M is estimated from the HCN production rate and the rate of decomposition of the amino acids by passage through the submarine vents.     

Stoichiometric and catalytic hydrogenation of the [Co2(CO)6(μ2-η2-alkyne)] complexes

The [Co₂(CO)₆(RC₂R′)] complexes (R, R′ = H, Me, Et, Prⁿ) react with molecular hydrogen under mild conditions of temperature and pressure, at low but appreciable rates. The effect of the steric hindrance of the substituents and the strength of the metalcarbon bonds are discussed. The kinetic data measured for [Co₂(CO)₆(HC₂H)], suggest that both H₂-coordination and CO-dissociation are involved in the rate-determining step of the overall hydrogenation process.The catalytic activity of [Co₂(CO)₆(HC₂H)] in the homogeneous hydrogenation of acetylene is described. At low substrate/catalyst ratio the initial hydrogenation rate is equal, within experimental error, to that found for the stoichiometric reaction; on increasing the acetylene concentration, cyclotrimerization to benzene becomes the dominant process. Interestingly C₄ hydrocarbons (mainly butadiene and 1-butene) are produced in measurable yield (?8%). The formation of these products is interpreted as the result of the hydrogenation of the elusive [Co₂(CO)₅(HC₂H)₂] complex, an unstable intermediate in the cyclotrimerization chain.     

Abiotic synthesis of organic molecules from minerals containing traces of dissolved H2O,CO2 and N2 part II: Experimental data

Even though a given mineral, for instance olivine, may contain only traces of dissolved H₂O, CO₂ and N₂ the gases which evolve from its surface during heating comprise (a) highly reduced molecules such as H₂, CH₄, C_mH_n and more complex hydrocarbons, HCN and other N-bearing compounds (b) oxidized species in various degrees of oxidation from formaldehyde and CO to oxygen. These gases evolve sequentially besides H₂O, CO₂ and possibly N₂, their relative amounts being controlled by experimental parameters such as the rate of heating. Preliminary indications of amino acids have been obtained by liquid extraction. The chemical complexity is a consequence of radical reactions between different solute species in the surface and the bulk of the mineral grains. Data for synthetic MgO and for mantle-derived olivine are presented.     

Reactions of [Os3(CO)10(MeCN)2] with ethynyl thiophenes: The formation of linked clusters

The reaction of 2 equiv. of [Os₃(CO)₁₀(MeCN)₂] with R-CC-L-CC-R (R = H, L = (C₄H₂S); R = SiMe₃, L = (C₄H₂S-C₄H₂S), (C₄H₂S-C₄H₂S-C₄H₂S), (C₄H₂S)-(C₁₄H₈)-(C₄H₂S)) affords the series of linked clusters [{Os₃(CO)₁₀}(HCC(C₄H₂S)CCH){Os₃(CO)₁₀}] (1), [{Os₃(CO)₁₀}(Me₃SiCC(C₄H₂S-C₄H₂S)CCSiMe₃){Os₃(CO)₁₀}] (2), [{Os₃(CO)₁₀}(Me₃SiCC(C₄H₂S-C₄H₂S-C₄H₂S)CCSiMe₃){Os₃(CO)₁₀}] (4) and [{Os₃(CO)₁₀}(Me₃SiCC(C₄H₂S)-(C₁₄H₈)-(C₄H₂S)CCSiMe₃){Os₃(CO)₁₀}] (6) as the major products. The complexes have been characterised by a range of spectroscopic methods and, in the case of 1 and 2 by single crystal X-ray crystallography. The alkyne groups cap the osmium triangles in the expected μ₃-η²-||-bonding mode and each triangle is coordinated by nine terminal and one μ₂-carbonyl group. Solution UV-Vis spectra of the complexes were similar to those observed for the free ligands consistent with there being little delocalisation between the cluster units and the thiophene groups.     

The inhibition of mitochondrial cytochrome oxidase by the gases carbon monoxide, nitric oxide, hydrogen cyanide and hydrogen sulfide: chemical mechanism and physiological significance

The four gases, nitric oxide (NO), carbon monoxide (CO), hydrogen sulfide (H₂S) and hydrogen cyanide (HCN) all readily inhibit oxygen consumption by mitochondrial cytochrome oxidase. This inhibition is responsible for much of their toxicity when they are applied externally to the body. However, recently these gases have all been implicated, to greater or lesser extents, in normal cellular signalling events. In this review we analyse the chemistry of this inhibition, comparing and contrasting mechanism and discussing physiological consequences. The inhibition by NO and CO is dependent on oxygen concentration, but that of HCN and H₂S is not. NO and H₂S are readily metabolised by oxidative processes within cytochrome oxidase. In these cases the enzyme may act as a physiological detoxifier of these gases. CO oxidation is much slower and unlikely to be as physiologically important. The evidence for normal physiological levels of these gases interacting with cytochrome oxidase is equivocal, in part because there is little robust data about their steady state concentrations. A reasonable case can be made for NO, and perhaps CO and H₂S, inhibiting cytochrome oxidase in vivo, but endogenous levels of HCN seem unlikely to be high enough.     

Structure determination of proteins in <Superscript>2</Superscript>H<Subscript>2</Subscript>O solution aided by a deuterium-decoupled 3D HCA(N)CO experiment

We developed an NMR pulse sequence, 3D HCA(N)CO, to correlate the chemical shifts of protein backbone ¹Hα and ¹³Cα to those of ¹³C′ in the preceding residue. By applying ²H decoupling, the experiment was accomplished with high sensitivity comparable to that of HCA(CO)N. When combined with HCACO, HCAN and HCA(CO)N, the HCA(N)CO sequence allows the sequential assignment using backbone ¹³C′ and amide ¹⁵N chemical shifts without resort to backbone amide protons. This assignment strategy was demonstrated for ¹³C/¹⁵N-labeled GB1 dissolved in ²H₂O. The quality of the GB1 structure determined in ²H₂O was similar to that determined in H₂O in spite of significantly smaller number of NOE correlations. Thus this strategy enables the determination of protein structures in ²H₂O or H₂O at high pH values.     

Absence of nitrogen fixation (acetylene reduction) by procaryotes in nectar of Banksias

Summary An earlier hypothesis that blue-green algae in the nectar ofBanksia telmatiaea contribute to the nitrogen economy of the host by fixing N₂ was tested. Field and laboratory experiments failed to demonstrate C₂H₄ production in C₂H₂-treated containers over extended periods. Soil N was not higher at the end of the flowering season and plants in which flower heads were removed prior to nectar production did not contain less N than the controls.     

Complexes of the fac-{Re(CO)3} core with tridentate ligands derived from arylpiperazines

Arylpiperazines, XC₆H₄N(CH₂CH₂)₂NH, are readily alkylated to give the N-alkylpiperazines of the type XC₆H₄N(CH₂CH₂)₂N(CH₂)_nNH₂. The amine functions of these derivatives are in turn easily subjected to mono- or dialkylation to provide potentially tridentate ligands of the types XC₆H₄N(CH₂CH₂)₂N(CH₂)_nN(H)(CH₂Y) and XC₆H₄N(CH₂CH₂)₂N(CH₂)_nN(CH₂Y)(CH₂Z), respectively. The latter class of dialkylated derivatives may be symmetrically (Y=Z) or unsymmetrically (Y ≠ Z) substituted. The donor groups Y and Z of this study include pyridine, imidazole, methyl-imidazole, thiazole, carboxylate and thiolate.The reactions of these ligands with [NEt₄]₂[Re(CO)₃Br₃] yield complexes of the type [Re(CO)₃{(YCH₂)N(H)(CH₂)_n(H)_xN(CH₂CH₂)₂N(H)_yC₆H₄X}]ⁿ and [Re(CO)₃{(ZCH₂)(YCH₂)N(CH₂)_n(H)_xN(CH₂CH₂)₂N(H)_yC₆H₄X}]ⁿ where the molecular charge n (0, +1, or +2) depends on the nature of the donor groups Y and Z (whether neutral or anionic or a combination of neutral and anionic) and on the degree of protonation of the piperazine unit (x=0 or 1; y=0 or 1). This variety of tridentate chelators provides complexes with fac-{Re(CO)₃N₃}, {Re(CO)₃N₂O}, {Re(CO)₃NO₂}, {Re(CO)₃N₂S} and {Re(CO)₃NS₂} coordination geometries. The structures of the model compound [Re(CO)₃{(CH₃N₂C₃H₂CH₂)N(H)CH₂CH₂-piperidine}]Br · H₂O, [Re(CO)₃{(CH₃N₂C₃H₂CH₂)N(H)CH₂CH₂-Fphenpip}]Br, [Re(CO)₃{(NC₅H₄CH₂)N(H)CH₂CH₂-Fphenpip}]Br, [Re(CO)₃{(O₂CCH₂)₂NCH₂CH₂CH₂-CH₃OphenpipH}] · xCH₃OH (x≈0.875), [Re(CO)₃{(NC₅H₄CH₂)₂NCH₂CH₂CH₂-CH₃OphenpipH}]Br₂ · 2CH₂Cl₂ · H₂O and [Re(CO)₃{(CH₃N₂C₃H₂CH₂)(O₂CCH₂)NCH₂CH₂CH₂-CH₃OphenpipH₂}]BrCl · 1.5CH₃OH · H₂O are discussed (phenpip: phenylpiperazine, -C₆H₄N(CH₂CH₂)₂N-).     

Recent observations of interstellar molecules: Detection of CCO and a limit on H2C3O

In order to test gas-phase reaction schemes for the production of small oxides of carbon in cold, dense interstellar clouds, we have searched for the radical CCO and for propadienone (H₂C₃O) in Taurus Molecular Cloud 1, a nearby cloud which exhibits a rich organic chemistry. The radical CCO has been detected with a fractional abundance some two orders of magnitude less than that of CCS, about one order of magnitude less than that of H₂CCO, and slightly less than that of C₃O. An upper limit has been obtained on the abundance of propadienone which is slightly less than that of its isomer propynal (HC₂CHO).     

Preparation of mono- or di-metal indenyl-iridium edrivatives and of tri-metal iridium-platinum complexes

Treatment of [IrCl(C₂H₄)₄] with K(C₉H₇) (C₉H₇ =indenyl) gives [Ir(C₂H₄)₂(η-C₉H₇)]. This compound is converted quantitatively into [Ir(CO)₂(η-C₉H₇)] by treatment with carbon monoxide. By reacting together these two iridium complexes [Ir₂(μ-CO)(CO)₂(ηC₉H₇)₂] has been obtained. The compound [Ir(CO)₂(η-C₉H₇)] reacts with [Pt(C₂H₄)₂{P(cyclo-C₆H₁₁)₃}] to give the complex [Ir₂Pt(CO)₃{P(cyclo-C₆H₁₁)₃}(η-C₉H₇)₂]. Protonation of the latter affords the salt [Ir₂Pt(μ-H)(CO)₃{P(cyclo-C₆H₁₁)₃}(μ-C₉H₇)₂] [BF₄]. The main features of the molecular structure of these complexes have been established by IR and NMR spectroscopy.     

Decomposition of toluene in a steady-state atmospheric-pressure glow discharge

Results are presented from experimental studies of decomposition of toluene (C₆H₅CH₃) in a polluted air flow by means of a steady-state atmospheric pressure glow discharge at different water vapor contents in the working gas. The experimental results on the degree of C₆H₅CH₃ removal are compared with the results of computer simulations conducted in the framework of the developed kinetic model of plasma chemical decomposition of toluene in the N₂: O₂: H₂O gas mixture. A substantial influence of the gas flow humidity on toluene decomposition in the atmospheric pressure glow discharge is demonstrated. The main mechanisms of the influence of humidity on C₆H₅CH₃ decomposition are determined. The existence of two stages in the process of toluene removal, which differ in their duration and the intensity of plasma chemical decomposition of C₆H₅CH₃ is established. Based on the results of computer simulations, the composition of the products of plasma chemical reactions at the output of the reactor is analyzed as a function of the specific energy deposition and gas flow humidity. The existence of a catalytic cycle in which hydroxyl radical OH acts a catalyst and which substantially accelerates the recombination of oxygen atoms and suppression of ozone generation when the plasma-forming gas contains water vapor is established.     

Chalcogenolato-bridged cyclometallated binuclear palladium complexes: Synthesis, spectroscopy, structures of [Pd2(μ-Cl)(μ-SMes)(C10H6NMe2-C,N)2] and [Pd2(μ-SePh)2(C10H6NMe2-C,N)2]

Reactions of orthometallated binuclear palladium complexes with NaER, obtained by NaBH₄ reduction of R₂E₂ in methanol, gave complexes, [Pd₂(μ-ER)₂(C^∩Y)₂] (HC^∩Y = N,N-dimethylbenzylamine (C₆H₅CH₂NMe₂), N,N-dimethylnaphthylamine (C₁₀H₇NMe₂), tri-o-tolylphosphine {P(tol-o)₃}; ER=SePh, SeMes, TePh, TeMes (Mes = 2,4,6-Me₃C₆H₂). Similar reactions of [Pd₂(μ-Cl)₂(C₁₀H₆NMe₂-C,N)₂] with Pb(SMes)₂ or MesSH in the presence of NaHCO₃ gave chloro/thiolato-bridged complex [Pd₂(μ-Cl)(μ-SMes)(C₁₀H₆NMe₂-C,N)₂]. The newly synthesized complexes were characterized by elemental analysis, UV-Vis, IR, NMR (¹H, ¹³C, ³¹P, ⁷⁷Se, ¹²⁵Te) spectroscopy. These complexes crystallized out preferentially in sym-cis configuration. A low energy charge transfer transition has been identified from chalcogenolate centers to an emptyπ^∗ orbital of cyclometallated ligand in absorption spectroscopy in these complexes. The structures of [Pd₂(μ-Cl)(μ-SMes)(C₁₀H₆NMe₂-C,N)₂] (1) and [Pd₂(μ-SePh)₂(C₁₀H₆NMe₂-C,N) ₂] (3) have been established by single crystal X-ray diffraction analyses. In the former, the two palladium atoms are held together by chloro and thiolato bridges whereas in the latter, the two phenylselenolato ligands bridge two palladium atoms. The pyrolysis of [Pd(μ-TeMes)(C₁₀H₆NMe₂-C,N)]₂ (10) in a furnace gave Pd₇Te₃ whereas thermolysis in TOPO afforded primarily PdTe₂.     

Respiration and the energy requirement for nitrogen fixation in nodulated pea roots

Pisum sativum L. cv. Trapper plants were inoculated and grown in a controlled environment on N-free nutrient solution. After 4 weeks N was supplied to treatment plants as NH₄NO₃, KNO₃, or NH₄Cl and rates of C₂H₂ reduction, root + nodule respiration, and leaf photosynthesis were determined 1 week later. The increase in respiration per unit of C₂H₂ reduction was not affected by either the form of N added or the light conditions during growth, although the basal respiration rate with no C₂H₂ reduction increased with irradiance level. The mean regression coefficient from plots of respiration versus C₂H₂ reduction was 0.23 + 0.04 (P [unk] .01) mg of CO₂ (μmol of C₂H₂ reduced)⁻¹ which was very similar to the value for the coefficient of respiration associated with nitrogenase activity estimated by subtracting growth and maintenance respiration. Since the rate of N accumulation in N-free nutrient conditions was proportional to the rate of C₂H₂ reduction, it appears that the method gives a true estimate of the energy requirements for N fixation which for these conditions was equivalent to 17 grams of carbohydrate consumed per gram of N fixed.     

Synthesis of [{Os3(CO)10(μ2-H)}2{μ2,μ2-NC6H4C6H4N}] and [{Os3(CO)9(μ2-H)PPh3}2{μ2,μ2-NC6H4C6H4N}]: Carbon–carbon bond formation promoted by organorhodium species

Synthesis and characterization of linked cluster [{Os₃(CO)₁₀(μ₂-H)}₂{μ₂,μ₂-NC₆H₄C₆H₄N}] (1) from the reaction of [Os₃Rh(μ-H)₃(CO)₁₂] with aniline in the presence of an excess amount of 4-vinyl phenol in refluxing heptane is reported. A similar reaction with [Os₃(CO)₁₀(NCMe)₂] as starting material gave a known compound, [Os₃(CO)₁₀(μ₂-H)(μ₂-HNC₆H₅)] (2). The treatment of complexes 1 and 2 with Wilkinson’s catalyst in refluxing heptane respectively, yielded [{Os₃(CO)₉(μ₂-H)PPh₃}₂{μ₂,μ₂-NC₆H₄C₆H₄N}] (3). An interesting and unexpected C–C coupling of phenyl-amido ligands was observed in complexes 1 and 3, which is believed to be catalysed by the organometallic rhodium species. The newly synthesized compounds 1 and 3 were fully characterized by IR, ¹H NMR spectroscopy, mass spectroscopy, elemental analysis, and X-ray crystallography. Both structures 1 and 3 comprise two triangles of osmium atoms. The two triangular osmium metal cores are linked by a bi-amido ligand via the two nitrogen atoms N(1) and N(1)* and N(1) and N(2), at their equatorial sites. The electronic absorption spectra of complexes 1, 2, and 3 display both low energy absorption, dπ (Os) → π* (amido) metal-to-ligand charge-transfer (MLCT) transition, and π → π* intra-ligand electronic transitions of the amido and bi-amido ligands.     

Reactivity of electron-deficient triosmium quinoline cluster [Os3(CO)9(μ3-η-C9H6N)(μ-H)] with alkynes

Reactions of the electron-deficient triosmium cluster [Os₃(CO)₉(μ₃-η²-C₉H₆N)(μ-H)] (1) with various alkynes are described. Cluster 1 readily reacts with the activated alkyne dimethyl acetylenedicarboxylate (dmad) upon mild heating (65-70 °C) to give the adduct [Os₃(CO)₉(μ-C₉H₆N)(μ₃-MeO₂CCCHCO₂Me)] (2). In contrast, a similar reaction of 1 with diphenylacetylene affords previously reported compounds [Os₃(CO)₁₀(μ-η²-C₉H₆N)(μ-H)] (3), [Os₃(CO)₉(μ-C₄Ph₄)] (4) and [Os₃(CO)₈{μ₃-C(C₆H₄)C₃Ph₃}(μ-H)] (5) while with 2-butyne gives only the known compound [Os₃(CO)₇(μ-C₄Me₄)(μ₃-C₂Me₂)] (6). The new cluster 2 has been characterized by a combination of spectroscopic data and single crystal X-ray diffraction analysis.