Synthesis of carbon nanotubes by catalytic pyrolysis method with Feitknecht compound as precursor of NiZnAl catalyst

Carbon nanotubes are synthesized by catalytic pyrolysis method with a kind of new type catalyst——nickel-zinc-alumina catalyst prepared from Feitknecht compound. Tubular carbon nanotubes, bamboo-shaped carbon naotubes, herringbone carbon nanotubues and branched carbon nanotubes are all found formed at moderate temperature. It is important for the formation of quasi-liquid state of the metal nanoparticles at the tip of carbon naotubes during the growth of carbon nanotubes to lead to different …     

The synthesis of [Fe(CO)3(η1-dppm) {Sn(n-Bu)2}]2 by silicon-tin exchange,its crystal structure and its use as a metallodiphosphine ligand

The reaction of the siloxyl containing ferrate [Fe(CO)₃( ¹-dppm){Si(OMe)₃}]^–,1 (dppm = Ph₂PCH₂PPh₂) with Sn(OAc)₂(n-Bu)₂ has yielded the new dimeric complex [Fe(CO)₃( ¹-dppm){µ-Sn(n-Bu)₂}]₂, 3 in 89% yield. Compound3 was characterized crystallographically and was found to be a centrosym-etrical molecule with a rhomboidal Fe₂Sn₂ cluster at the center. Each iron atom contains me ¹-dppm ligand. Compound3 was found to react with [Pd(dmba) (µ-Cl)]₂ (dmba=dimethylbenzylamine) to yield the new complexmer-[Fe(CO)₃{Sn(n-Bu)₂}(µ-dppm)Pd(dmba)Cl]₂, 4 by attachment of a palla-dium grouping to each of the uncoordinated phosphorus atoms in 3. Crystal data for 3: space groupP ,a=11.399(2) Å, 6=15.98(3) Å, c=10.869(3) Å, =94.10(2)°.=100.56(2)°, =69.35(1)°,Z=2, 3533 reflections,R=0.034.     

Chemistry of {Fe2(CO)6PR}, an Aromatic Organometallic 2π Intermediate

Abstract

Compounds Fe₂(CO)₆(μ₂-Cl)(μ₂-PRCl), 1, undergo reductive dehalogenation to yield what may be interpreted as an aromatic Fe₂(CO)₆PR 2π entity. The intermediate, though not isolated itself, may be trapped by various organic and organometallic scavangers, leading to compounds of type 2 to 4.     

Synthesis and X-ray crystal structure analysis of Fe2(CO)6(μ3-S)2Pd(bipy)

The reaction of Fe₂(CO)₆(μ-S₂),1 withbis(dibenzylideneacetone)-palladium, Pd(dba)₂, in the presence of 2,2′-bipyridine yielded the new compound Fe₂(CO)₆(μ ₃-S)₂Pd(bipy),2 in good yield (66%). Compound2 was characterized by IR,¹H NMR and single-crystal X-ray diffraction analyses. Compound2 contains a Pd(bipy) group that has been inserted into the S-S bond of1. Crystal data for2: space group P2₁/n,a=10.019(2) Å,b=25.414(5) Å,c=7.714(2) Å,β=90.26(2)°,Z=4, 1436 reflections,R=0.023.     

Nanoparticles of the novel coordination polymer KBi(H2O)2[Fe(CN)6]·H2O as a potential contrast agent for computed tomography

An aqueous synthetic procedure for preparing nanoparticles of the novel potassium bismuth ferrocyanide coordination polymer KBi(H(2)O)(2)[Fe(CN)(6)]·H(2)O is reported. The crystal structure of this coordination polymer is determined through X-ray powder diffraction using the bulk materials. The stability, cytotoxicity, and potential use of such nanoparticles coated with PVP as a CT contrast agent are investigated.     

Synthesis of [(μ2-η2-CHCHPh)(μ-S){Fe2(CO)6}2(μ4-S)]− and its reactions with electrophiles

The action of [(μ₂-η²-CHCHPh)(μ-CO)Fe₂(CO)₆]⁻ with (μ-S)₂Fe₂(CO)₆ gives the anionic complex [(μ₂-η²-CHCHPh)(μ-S){Fe₂(CO)₆}₂(μ₄-S)]⁻ (1). The anion 1 reacts with alkyl halides, acid chlorides and Cp(CO)₂FeI to yield neutral products (μ₂-η²-CHCHPh)(μ-RS)[Fe₂(CO)₆]₂(μ₄-S) (R=Me, 2a; Et, 2b; PhCH₂, 2c; PhC(O), 3a; PhCHCHC(O), 3b and Cp(CO)₂Fe, 4).     

[Fe2S2(CO)6]2− as a cluster precursor: synthesis and structure of [MoFe3S6(CO)6]2− and oxidative decarbonylation to a persulfide-bridged MoFe3S4 double cubane

Reactions of [Fe₂S₂(CO)₆]²⁻ (3) with [Cl₂FeS₂MS₂]²⁻ [M = Mo (4) or W (6)] and [Cl₂FeS₂VS₂FeCl₂]³⁻ (8) in acetonitrile-THF solutions afford the new clusters [MFe₃S₆(CO)₆]²⁻ (M = Mo (5) or W (7)] and [VFe₆S₈(CO)₁₂]³⁻ (9). (Et₄N)₂ (5) crystallizes in orthorhombic space group Pbcn with a = 15.314(7) Å, b = 16.627(6) Å, c = 29.971(13) Å, and Z = 8. Cluster 5 is formed by displacement of chloride from 4 by 3 to yield a species with the [Fe₂(μ₃-S)₂Fe(μ₂-S)₂MoS₂]²⁻ core arrangement containing one Fe(II) and Mo(VI) in distorted tetrahedral sites. Similar structures are proposed for 7 and 9, with the latter containing two 3 ligands bound to the [VFe₂S₄]¹⁺ core of 8. Treatment of 5 with RSSR results in oxidative decarbonylation and formation of [Mo₂Fe₆S₈(S₂)₂(SR)₆]⁴⁻ (10) (R = p-C₆H₄Cl or p-C₆H₄Br), which consists of two [MoFe₃(μ₃-S)₄]³⁺ cubane-type subclusters bridged by two μ₂-η³-S₂²⁻ groups. Cluster 10 was also obtained in a direct-assembly system consisting of [MoS₄]²⁻ + 3FeCl₃+ S₂²⁻ + 7RS⁻ in methanol. Evidence is presented that the solid-state structure of 10 is maintained in solution. The redox change [MoFe₃(μ₂-S)₂(μ₃-S) ₂S₂]²⁻ (5) → [MoFe₃(μ₃-S)₄(S₂)]¹⁺ (10) is described as an oxidatively induced core internal conversion in which there is net Fe and S oxidation and Mo reduction. It is argued that the reduction of tetrahedral Mo(VI) to or near Mo(III), stabilized in a six-coordinate site, is a significant factor in the formation of the cubane structure. The formation of the cubane cluster [VFe₃S₄Cl₃(DMF)₃]¹⁻ from 8 and FeCl₂ is similarly promoted by the reduction of tetrahedral V(V) to or near V(III). The syntheses of 5, 7, 9 and 10 illustrate the utility of 3 as a cluster precursor.     

A classical versus quantum mechanics study of the hbox{OH},+,hbox{CO} rightarrow,hbox{H},+,hbox{CO}_2 (J?=?0) reaction

When appropriately used, the multiconfigurational self-consistent field (MCSCF) approximation is useful in discerning correct electronic structure results. However, with the increasing size of chemical systems of interest, MCSCF rapidly becomes unfeasible due to the requirement of larger active spaces, which lead to computationally unmanageable numbers of configurations. This situation is especially true for complete active space self-consistent field (CASSCF). In particular, reducing this computational expense by using restricted active spaces in solving for gradients and nonadiabatic couplings (NACs) during dynamics runs would save computer time. However, the validity of such restricted spaces is not well-known even for recovering the majority of the nondynamical correlation and inevitably varies between chemical systems across a range of nuclear geometries. As such, we use the recently implemented coupled perturbed–occupation restricted multiple active space (CP-ORMAS) equations (West et al., unpublished) to verify the accuracy of this approximation for gradients and NACs vectors around two specific conical intersection geometries for the silaethylene and butadiene systems. Overall, no excitations between appropriate subspaces show qualitatively reasonable results while single excitations significantly improve ORMAS results relative to the CASSCF level in these particular systems. However, single excitation schemes do not always lead to the correct orbital subspaces, and as a result, seemingly smooth potential energy surfaces (PES) do not always result in smooth analytical gradients and NACs. In addition, while some of the single excitation ORMAS and CASSCF schemes have improper orbitals rotate into the active space, the schemes without excitations (even with more subspaces) do not exhibit this behavior.     

Acetylene as a ligand on clusters: An accurate determination of the crystal and molecular structure of (Cp)2Ni2Fe(CO)3(μ3−C2H2) and of (CP)2Ni2Fe2(CO)6(μ4−C2H2)

Abstarct The Cp)₂Ni₂Fe(CO)₃(µ₃-C₂H₂) and Cp)₂Ni₂Fe(CO)₃(µ₃-C₂H₂) (B) complexes have been synthesized and spectroscopically characterized. An accurate X-ray study and a comparison with related structures shows that the substituents of the alkyne ligands exert considerable effects on the bonding parameters.Crystal data for complex A, monoclinic space group P2₁/n,a = 8.418(1),b = 15.779(2),c = 14,493(1) Å, = 91.64(1)°,Z = 4, 2753 observed reflections,R = 0.022; crystal data for complex B, monoclinic space group C2/c,a = 16.2189(7),b = 7.445(3),c = 25.745(5) Å, = 103.74(3),Z=8, 1853 observed reflections,R = 0.051.     

过渡金属卡宾配合物 VI:单、双核锰和双核铼的铁硫原子簇卡宾配合物-π-C5H5(CO)2MnC(C6H5)(μ-S)(μ-C6H5S)Fe2(CO)6和[π-C5H5(CO)2MC(C6H5)]2(μ-S)2Fe2(CO)6(M=Mn,Re)的合成和波谱

本文报道了锰和铼的阳离子卡拜配合物[π-C5H5(CO)2MCC6H5]BRr4(M=Mn, Re)分别与(μ-苯硫)六羰基二铁和双(μ-锂硫)六羰基二铁阴离子反应生成标题化合物. 产物的组成和结构由元素分析, IR, ^1H NMR和MS分析, 以及7的单晶X射线结构分析确定的. 文中还对合成和波谱研究结果进行了讨论.     

X-ray structure of Fe{C(CF3)2(OH)}(CO)2(η-C5H5), a complex containing a substituted hydroxymethyl ligand

An X-ray structure determination on Fe{C(CF₃)₂(OH)}(CO)₂(η-C₅H₅), obtained by protonating the product from Na[Fe(CO)₂(η-C₅H₅)] and (CF₃)₂CO, showed the crystal to contain discrete molecules. There are substantial intramolecular OH…FCF₂ bonds but only weak intermolecular OH…O interactions. Important distances are: FeC 2.060(6), CCF₃ 1.505(9), COH 1.435(7), CF…HO 2.131(6), 2.485(6) Å.     

Formation of sulfhydryl (SH) species on the clean and (2 × 2)-S covered Pt(111) surfaces by H2S decomposition

H₂S decomposition on the clean and (2 × 2)-S covered Pt(111) surfaces has been characterized using high-resolution electron energy loss (HREELS) and temperature-programmed desorption (TPD) spectroscopies. On the Pt(111)-(2 × 2)-S surface, a mixture of molecular H₂S and sulfhydryl (SH) species forms following H₂S adsorption at 110 K. The molecular H₂S desorbs at 140 K leaving a (2 × 2)-S overlayer saturated with SH; the SH is stable up to 190 K. On the clean Pt(111) surface, a mixture of atomic sulfur, SH and chemisorbed molecular H₂S is formed following H₂S adsorption at 110 K. On the clean surface, adsorbed SH decomposes near 150 K. We report here the first definitive observation of an adsorbed sulfhydryl species on a metal surface.     

Tris(hydroxymethyl)aminomethane as an efficient organobase catalyst for the synthesis of β-phosphonomalonates

Tris(hydroxymethyl)aminomethane (THAM) is a highly efficient and recyclable organobase catalyst for the nucleophilic phosphonylation of benzylidene malononitrile under solvent-free conditions. This new catalytic methodology is applicable without a solvent, eco-friendly, economically viable, avoids conventional isolation procedures, and has a facile work-up procedure and wide scope. THAM is an inexpensive, commercially available, non-toxic, and biodegradable novel organocatalyst. Furthermore, it can be reused in up to five cycles without loss in catalytic activity, and no chromatographic separation is needed to obtain the desired products.     

Calculation of the ground and excited states of a mixed valence compound [Fe2(OH)3(NH3)6]2+: a class II or class III compound?

The effective group potentials (EGP) approach has been successfully used for the computation of the ground and excited states energies of the mixed valence compound [Fe2(OH)3(NH3)6]2+. It is the first time that for a system as big as the complex presented above the ground and excited states are computed with their own orbitals and studied in such a detailed way. First of all, the NH3 EGP was validated by comparing calculations where NH3 was treated explicitly at different levels of calculations. Once the validation was obtained, the complete spectrum of the compound under interest was calculated and compared with results obtained in a previous work by Barone et al. and the spin Hamiltonian of widespread use. Some deviations from these predictive approaches were observed. This allowed us to emphasize the importance of the dynamic correlation which is not included explicitly in the spin Hamiltonian. Then, the influence of vibration has been studied by computing the potential energy curves obtained when moving the (OH)3 plane. This study shows that our calculations lead to a delocalized compound (class III) as expected according to former experimental data.     

Coupling insertion reactions of diphenylbuta-1, 4-diyne into iron-carbene bonds of [Fe2(CO)7{μ-C(Ph)C(NEt2}]. Syntheses and reactivities of the ferracyclopentadiene [Fe2(CO)6{C(Ph)C(NEt2)C(Ph)C(C2Ph)}] with [Fe2(CO)9]

The diiron ynamine complex [Fe₂(CO)₇{-C(Ph)C(NEt₂)}] (1) reacts with the diphenylbuta-1, 4-diyne, PhCC-CCPh, in refluxing hexane to yield three isomer complexes [Fe₂(CO)₆{C(Ph)C(NEt₂)C(Ph)C(C₂Ph}] (2a), [Fe₂(CO)₆{C(Ph)C(NEt₂)C(C₂Ph)C(Ph)}] (2b), and [Fe₂(CO)₆{NEt₂)C(Ph)C(C₂)C(Ph)}] (2c) All three compounds were identified by their¹H NMR spectra. Compounds2a and2c were characterized by single crystal X-ray diffraction analyses. Crystal data: for2a: space group = P2₁/n,a = 17.873(1) Å, = 18.388(6) Å,c = 9.429(3) Å = 91.99(3)°,Z = 4.3751 reflections,R = 0.044; for2c: space group = P2₁/n,a = 40.58(2) å,b = 12.101(9) Å,c = 12.551(5) Å, = 94.29(7)°,Z = 8.4723 reflection,R = 0.076. Complexes2a and2b result from a [2 + 2] cycloaddition between one of the CC triple bonds of the diyne ligand and the FeC carbene bond, whereas2c results from insertion of one of the CC group into the bridging carbene. Addition of [Fe₂(CO)₉] on2a gave two major products, the tripledecker [Fe₃(CO)₈{C(Ph)C(NEt₂)C(C₂Ph)}], (3 and a tetrairon cluster [Fe₄(CO)₁₁{C(Ph)C(NEt₂)C(Ph)C(C₂Ph)}] (4). Both compounds were characterized by single crystal diffraction analyses. Crystal data: for3: space group = P2₁/n,a = 12.039(3) Å,b = 18.046(3) å,c = 15.270(2) Å, = 90.11(2)°,Z = 4, 1430 reflections,R = 0.067; for4 space group = C2/c,a = 18.633(3) Å,b = 21.467(1)_Å,c = 20.742(2) Å, = 115.03(8)°,Z = 8.992 reflections, R = 0.076. Complex4 is based on a spiked triangular cluster with the alkynyl triple bond attached in ₃-parallel mode on the triangular grouping.     

Migration of the η1:η6-C6H5Cr(CO)3 ligand into the cyclopentadienyl ring during metallation of the η5-C5H5(CO)2Fe η1:η6-C6H5Cr(CO)3 binuclear complex

It was found that the ¹⁶-C₆H₅Cr(CO)₃ ligand migrates into the cyclopentadienyl ring when the ⁵-C₅H₅(CO)₂Fe ¹⁶-C₆H₅Cr(CO)₃ binuclear complex is metallated with BuⁿLi. Under the same conditions, no migration of the phenyl ligand in the ⁵-C₅H₅(CO)₂Fe ¹-C₆H₅ complex was observed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 325–326, February, 1994.     

The synthesis and reactivity of the heptanuclear dianion [Os7(CO)20]2− including the synthesis and structural characterizations of the compounds [Os7(CO)20(AuPEt)3 2] and [Os8(CO)20(η6-C6H6]

Reduction of the heptaosmium cluster [Os₇(CO)₂₁] With [Et₄N][NH₄) gives the cluster dianion [Os₇(CO)₂₀]^2–,1, in high yield. The reaction of the dianion with [AuPR ₃Cl] (R=Et or Ph) in the presence of TlPF₆ forms [Os₇((CO)₂₀(AuPR ₃)₂] [R=Et (2a);R = Ph(2b)] in 80% yield, while the corresponding reaction with (Os(C₆H₆)(CH₃CN)₃]²⁺ gives [Os₈(CO)₂₀ ( ⁶-C₆H₆)] (3) in reasonable yield (ca. 30%). The dianion,1, and the clusters2 and3 have been fully characterized by bout spectroscopic and crystallographic methods. The crystal structure of the [Ph₄P]⁺ salt of1 shows that the metals in the anion adopt a capped octahedral geometry, with all twenty carbonyl ligands in terminal sites. The metal core geometry in2a is best described as a tricapped octahedron, and is based on the structure of the dianion1 with two adjacent octahedral faces capped by the Au atoms of the two AuPEt₃ groups. In a similar fashion, the geometry of3 is related to that of1 with the addition of an Os(C₆H₆) unit capped to a triangular face, to give a bicapped octahedral framework.     

Reaction of iron pentacarbonyl with N,N-diethyl-S-ethylcarbamate; crystal structure of [{Fe(CO)6}3(μ4-S)2(μ-CNEt2)2]3(feFe), a compound containing three butterfly units

Reaction of iron pentacarboynl with N,N-diethyl-S-ethylcarbamate {SC-(NEt₂)SEt} gave [{Fe₂(CO)₆}{Fe₃(CO)₉(μ₄-S)(μ-CNEt₂(μ-SEt)}](FeFe)3-(FeFe) (I) and [{Fe₂(CO)₆}₃(μ₄-S)₂(μ-CNEt₂3(FeFe) (II). The structure of complex II has been determined by single crystal X-ray crystallography. It crystallizes from methylene chloride as C₂₆H₂₀O₁₈N₂S₂Fe₆·1/2CH₂Cl₂ in the monoclinic space group C2/c with a 46.754(2), b 9.268(1), c 19.628(2) Å, β 100.7(1)°, Z = 8, V 8358.6 ų, D_c 1.77 g cm⁻³, D_m 1.77 gm cm⁻³. The strucutre was solved by direct methods and refined to R = 0.0819 (R_w = 0.0469) for 3017 relfections. It consists of three metalmetal bonded Fe₂(CO)₆ units linearly linked in butterfly configuration by two bridging sulphur athoms, and terminated on both sides by bridging diethylimoniocarbene (CNEt₂) ligands.