含磷、硫、氮配原子的钴羰基簇合衍生物的合成和表征

过渡金属原子簇化学是当今化学学科中非常活跃的研究领域之一 ,这类簇合物大多有着新颖的几何构型和多样化的成键方式 ,并且具有独特的催化性能[1 ] 。迄今为止 ,人们合成了多种含磷、硫、氮等原子的铁、钴、钌等羰基簇合衍生物 ,但其中三种以上原子同时配位的情况并不多见 ,有金振兴等的含Ｃ、Ｓ、Ｎ配原子的三核钴簇[2 ] ;Ｌｕｇａ和Ｃａｂｅｚａ的三钌簇[3 ,4] 以及Ｃｈｉｈａｒａ等合成的五核钌簇[5] ,其分子中都有Ｐ、Ｎ、Ｏ三原子配位。我们利用复杂的含Ｐ、Ｓ、Ｎ等可配原子的有机配前体与二元钴羰合物反应 ,合成了一系列三核、四核…     

Exceptionally effective catalysis of cyclopropanation reactions by the hexarhodium carbonyl cluster

Hexadecacarbonylhexarhodium exhibits exceptional activity as a cyclopropanation catalyst in reactions between ethyl diazoacetate and alkenes that are remarkably free of competing processes.     

Syntheses and molecular structures of new ferrocenylacetylide-bridged binuclear cobalt carbonyl cluster compounds

The reaction of ferrocenylacetylide compounds with Co₂(CO)₈ at room temperature affords four complexes bearing ferrocenyl units with approximately tetrahedral (μ-alkyne)dicobalt moieties [R–(C≡C) _n –R′] [Co₂(CO)₆] _{n ′} [R?=?C₅H₅FeC₅H₄-C(CH₃)₂-C₅H₄FeC₅H₄, R′?=?H, n?=?1, n′?=?1 (1); R?=?C₅H₅FeC₅H₄ [ferrocenyl (Fc)], R′?=?–CH=CHCl, n?=?1, n′?=?1 (2); R?=?Fc, R′?=?Fc, n?=?2, n′?=?1 (3), n′?=?2 (4)]. The compounds were characterized by elemental analysis, IR, ¹H(¹³C) NMR, MS and single-crystal X-ray diffraction analysis. The X-ray analyses show that coordination of the carbon–carbon triple bond and the dicobalt unit result in the formation of a Co₂C₂ tetrahedral core, and the substituents on the acetylenic units show a distortion from linearity that reflects this coordination mode.     

Base-promoted ruthenium carbonyl cluster complexes: From fundamental reactions to catalysis

An attempt to establish a link between the rich chemistry of ruthenium carbonyl clusters doped by nucleophilic anions, and the known effect of promoters in some ruthenium-based catalytic processes.     

The regiospecific cobalt carbonyl catalyzed synthesis of dienones and trienones by phase transfer catalysis

The phase transfer catalyzed, cobalt carbonyl catalyzed reaction of dienes, and a triene, with methyl iodide and carbon monoxide [r.t., 1 atm. P] is highly regiospecific, affording E-conjugated enones.     

Surface characterization of silica-supported cobalt oxide catalysts

Silica supported cobalt oxides were prepared by the impregnation method, using an aqueous solution of cobalt nitrate hexahydrate (Co(NO₃)₂ · 6H₂O), then calcined at different temperatures (510, 620 and 870 K). Characterization of the samples was carried out by X-ray diffraction, N₂-adsorption at −196°C, UV–Vis diffuse reflectance spectroscopy and KBr-IR spectroscopy of the calcination products. The surface acidity was studied by IR spectroscopy of adsorbed pyridine at different temperatures (300, 370, 470 and 570 K). Results indicated that Co₃O₄ is the stable phase on silica, however, dispersion of minor amount of cobalt oxide could not be ruled out. Results also indicated that the crystallinity of the formed Co₃O₄ increased by increasing the loading level and/or the calcination temperature. Furthermore, the surface area of the support was decreased by increasing the loading level and the calcination temperatures. It has been also found that the surface of the supported catalysts exposed strong different Lewis acid sites.     

Cooperative catalysis by silica-supported organic functional groups

Hybrid inorganic-organic materials comprising organic functional groups tethered from silica surfaces are versatile, heterogeneous catalysts. Recent advances have led to the preparation of silica materials containing multiple, different functional groups that can show cooperative catalysis; that is, these functional groups can act together to provide catalytic activity and selectivity superior to what can be obtained from either monofunctional materials or homogeneous catalysts. This tutorial review discusses cooperative catalysis of silica-based catalytic materials, focusing on the cooperative action of acid-base, acid-thiol, amine-urea, and imidazole-alcohol-carboxylate groups. Particular attention is given to the effect of the spatial arrangement of these organic groups and recent developments in the spatial organization of multiple groups on the silica surface.     

Synthesis and structure of a dithioether-substituted butene-2-olide-4-ylidene-4 cobalt carbonyl complex

The complex (1) has been prepared and its structure determined. Complex1 is the first stable thioether derivative of a metal carbonyl containing only cobalt as metal. It crystallizes in the monoclinic P2₁/c space group, witha = 13.975( 4 ),b = 11.363( 3 ),c = 14.686(2)A, = 112.25(2)°,V = 2158.5(7)A³.Z = 4. The solution using direct methods and the anisotropic refinement of all nonhydrogen atoms led toR = 0.039,wR = 0.041 for 3296 reflections with F> 4.0(F) Analogous but less stable complexes are formed with 1,6-diphenyl-2,5-dithiahexane and the crown thioether 1,4,7-trithiacyclonane, the latter functioning either as a bidenlate or a tridentate ligand.     

Synthesis and crystal structure of a new triosmium alkylidyne carbonyl cluster containing a chiral ferrocenylphosphine ligand

The synthesis, spectroscopic characterization and X-ray crystal structure of a new chiral triosmium alkylidyne carbonyl cluster, (R,S)-[Os3(mu-H)2(CO)9{mu3-CPPh2(eta(5)-C5H4)Fe(eta(5)-C5H3(PPh2)CH(Me)NM(2)}] (1) are described. Compound 1 crystallizes in the non-centrosymmetric space group P2(1) and its absolute configuration has been established.The structure consists of an Os3C metal core with one of the PPh2 moieties of the chiral ferrocenylphosphine bonded to the apical alkylidyne carbon atom to give a zwitterionic cluster complex, reminiscent of the phosphorus ylide.     

Practical cobalt carbonyl catalysis in the thermal Pauson--Khand reaction: efficiency enhancement using Lewis bases

In this report we have shown that the commercially available Co(2)(CO)(8) and Co(4)(CO)(12), and enyne--Co(2)(CO)(6) complexes, are sufficiently effective in catalyzing the Pauson--Khand reaction under one atmosphere of CO pressure. It was further demonstrated that the efficiencies of these cyclization protocols could be enhanced by the presence of cyclohexylamine. These procedures have also rendered more practical and highly convenient alternatives for the catalytic Pauson--Khand reaction. Most importantly, we have dispelled the common belief that Co(4)(CO)(12) is inactive in the Pauson--Khand reaction under one atmosphere of carbon monoxide. Of mechanistic importance is that these studies have also shown that the probable formation of Co(4)(CO)(12) is not necessarily a dead end pathway in the Co(2)(CO)(8)-catalyzed Pauson--Khand reaction. It is also of interest that substoichiometric amounts of Co(2)(CO)(8), in DME and in the presence of cyclohexylamine, are sufficient for the cyclocarbonylation of enynes under a nitrogen atmosphere. Our findings have provided more practical protocols for the Pauson-Khand reaction using catalytic amounts of cobalt carbonyl complexes and a better understanding of the influence of Lewis bases on their efficiency. These reports on the activity of Co(4)(CO)(12) are anticipated to develop into a convenient and practical alternative for Co(2)(CO)(8) catalysis.     

Low-temperature cluster catalysis

Free and supported metal clusters reveal unique chemical and physical properties, which vary as a function of size as each cluster possesses a characteristic electron confinement. Several previous experimental results showed that the outcome of a given chemical reaction can be controlled by tuning the cluster size. However, none of the examples indicate that clusters prepared in the gas phase and then deposited on a support material are indeed catalytically active over several reaction cycles nor that their catalytic properties remain constant during such a catalytic process. In this work we report turn-over frequencies (TOF) for Pd(n) (n = 4, 8, 30) clusters using pulsed molecular beam experiments. The obtained results illustrate that the catalytic reactivity for the NO reduction by CO (CO + NO --> 1/2N(2) + CO(2)) is indeed a function of cluster size and that the measured TOF remain constant at a given temperature. More interestingly, the temperature of maximal reactivity is at least 100 K lower than observed for palladium nanoparticles or single crystals. One reason for this surprising observation is the character of the binding sites of these small clusters: N(2) forms already at relatively low temperatures (400 and 450 K) and therefore poisoning by adsorbed nitrogen adatoms is prevented. Thus, small clusters not only open the possibility of tuning a catalytic process by changing cluster size, but also of catalyzing chemical reactions at low temperatures.     

Synthesis and structural characterization of new multiferrocenyl diyne ligands and their cobalt carbonyl complexes

New multiferrocenyl diyne ligands FcC(CH₃)₂Fc′–C≡C–C≡C–Fc [L ₁ ; Fc?=?C₅H₅FeC₅H₄; Fc′?=?C₅H₅Fe(1,3-disubstituted)C₅H₃], FcC(CH₃)₂Fc′–C≡C–C≡C–Fc′C(CH₃)₂Fc (L ₂ ) and their complexes [FcC(CH₃)₂Fc′–C≡C–C≡C–Fc][Co₂(CO)₆] _n [n?=?1, (1); n?=?2, (2)], [FcC(CH₃)₂Fc′–C≡C–C≡C–Fc′C(CH₃)₂Fc][Co₂(CO)₆] _n [n?=?1, (3); n?=?2, (4)] have been synthesized by the coupling reaction of terminal ferrocenylacetylene and the reaction of ligands L₁ and L₂ with Co₂(CO)₈. The composition and molecular structure of the ligands L₁ , L₂ and their cobalt complexes were characterized by element analysis, IR, ¹H(¹³C)NMR and MS. The electrochemical properties of compounds L₁ , L₂ , 1, 2, 3, 4 were studied by cyclic voltammetry(CV). The results of the electrochemical research reveal that all three ferrocenyl groups in L₁ become redox active centers, but there are only two (not four) ferrocenyl redox active centers in L₂ .     

Synthesis,crystal structure and properties of a new lanthanide‐transition metal carbonyl cluster

A new type heterobimetallic complex containing lanthanide and transition metal carbonyl cluster (Ln? M carbonyl cluster), Sm₂{OOCCCo₃(CO)₉}₂{OOCCF₃}₄{(CO)₉Co₃CCOOH}₄, has been synthesized by reaction of (CO)₉Co₃CCOOH with Sm(OOCCF₃)₃(H₂O)₂, and structurally characterized by single‐crystal X‐ray diffraction. Application of the complex as a catalyst precursor for hydrogenation of carbon monoxide (Fischer–Tropsch reaction) was explored, and the thermogravimetric behavior and magnetic properties of the compound were examined as well. Copyright © 2008 John Wiley & Sons, Ltd.     

Mixed iron cobalt carbonyl sulphides

Two new mixed iron cobalt carbonyl sulphide clusters HFe₂(CO)₉S and Fe₂Co(CO)₈(NO)S have been prepared and characterized. The hydride complex undergoes acidic dissociation in polar solvents and the resulting anion was isolated as (Et₄N)[Fe₂Co(CO)₉S]. An efficient high pressure synthesis has been found for H₂Fe₃(CO)₉S.     

Synthesis,structure, and properties of a pentanuclear cobalt(III) coordination cluster

The synthesis, X-ray structure and properties of a pentanuclear cobalt(III) coordination cluster [{L(O₂CCH₃)Co₂O(OCH₃)₂}₂Co](ClO₄)₃ (1) (L^? = 2,6-bis((3-aminopropylimino)methyl)-4-methylphenolate) are described. The dinucleating L^? is coordinated with two cobalt(III) centers to form the {L(O₂CCH₃)Co₂O(OCH₃)₂} unit, where each metal center is in a distorted octahedral N₂O₄ environment. The oxo and the methoxo ligands of these two dinuclear units assemble a distorted octahedral O₆ coordination sphere around the central cobalt(III). Elemental analysis and spectroscopic (IR, NMR, UV–vis, and HRMS) features are consistent with the pentanuclear structure of the complex. The diamagnetic complex is a 1?:?3 electrolyte in solution. It is redox-active and displays a metal-centered reduction at E_1/2 = ?0.04 V (vs. Ag/AgCl).     

Mass spectra of cobalt carbonyl complexes

The mass spectra of the following acetylenic derivatives of Co₂(CO)₈ are reported: Co₂(CO)₆C₂H₂Co₂(CO)₆C ₂,(CH₃)₂, Co₂(CO)₆ C₂(CH₂Cl)₂, Co₂(CO)₆C₂ (CF₃)₂, Co₂(CO)₂C₂(C₆H₅)₂ and Co₂(CO)₆C₂(COOCH₃)₂. The effect of different C₂RR′ on fragmentation modes is investigated. When R and R′ are aromatic groups, the major controlling factor is the stability of charged fragments; in other cases, it seems to be the loss of a stable neutral moiety. Transfer processes of alkoxylic groups are observed in Co₂(CO)₆C₂(COOCH₃)₂, as well as in Co₃(CO),₉CCOOCH₃, and Co₃(CO)₉CCOOC₂H₅. It is suggested that both cobalt and carbon atoms may be the migration sites.     

Homogeneous catalysis by ruthenium carbonyl clusters

The historical background of and the incentive for using ruthenium carbonyl clusters as homogeneous catalysts are outlined. Keeping in view the possible solutions the uncertainties arising from declusterification and metal colloid formation are discussed. All ruthenium cluster-catalysed reactions are broadly classified as reactions with or without carbon monoxide as one of the reactants and the basic differences between such reactions are highlighted. Some of the factors of special relevance to cluster-catalysed reaction systems are mentioned. The reactions involving carbon monoxide are then discussed. These include water-gas-shift reaction, carbon monoxide hydrogenation, hydroformylation, reductive carbonylation of nitrobenzene and other carbonylation reactions. Hydrogenation, transfer hydrogenation, isomerisation and a few other reactions are then discussed. For all these reactions, special emphasis is laid on well-characterised cluster complexes that have been proposed as catalytic intermediates. Finally an attempt has been made to identify the path that future research in cluster catalysis is likely to follow.     

Novel pyridinium based cobalt carbonyl ionic liquids: synthesis, full characterization, crystal structure and application in catalysis

Through an optimized synthetic strategy, a series of novel alkylpyridinium cobalt tetracarbonyl salts, [C(1)Py][Co(CO)(4)] (), [C(4)Py][Co(CO)(4)] () and [C(16)Py][Co(CO)(4)] () (C(n)Py = N-C(n)H(2n+1)-pyridinium), were successfully prepared in good yields, using a water-organic biphasic system. All the three compounds melt well below 100 degrees C and could be classified as ionic liquids. The compounds were fully characterized using IR, UV-Vis, (1)H NMR, (13)C NMR, ESI-MS and elemental analysis, and was structurally characterized by X-ray single crystal analysis. Compound has been found to be an efficient and reusable catalyst for the alkoxycarbonylation of propylene oxide without the aid of a base additive.