1,3-Dipolar Activity in Cycloadditions of an Aliphatic Sulfine(,)(1)

2,2,4,4-Tetramethyl-3-thioxocyclobutanone S-oxide (4) combines with diaryl thioketones at room temperature furnishing spiro-1,2,4-oxadithiolanes 6 in equilibrium reactions. Compound 6a was oxidized to the cis-S,S-dioxide 9, the structure of which was established by X-ray analysis. These are the first unequivocal 1,3-cycloadditions of thione S-oxides (sulfines) which possess an allyl anion type MO; cycloadditions to the C=S bond of sulfines as dipolarophile and dienophile had been described before.     

Organotransition-Metal Complexes of Multidentates 2. Synthesis and Allyl Bromination of N,N-Bis(3,5-Dimethylpyrazol-1-YL)Methane Derivatives of the Group VI Metal Carbonyls

N,N-Bis(3,5-dimethylpyrazol-1-yl)methane (H₂CPz'₂) reacts with the hexacarbonyls of chromium, molybdenum, and tungsten to give cis-(H₂CPz'₂)M(CO)₄ derivatives with M=Cr, Mo, W. The direct allyl bromination of these complexes is also investigated and only the molybdenum complex is converted into (H₂CPz'₂)Mo(CO)₂(π-C₃H₃)(Br).     

Organotransition-Metal Complexes of Multidentate Ligands 5. Structural Characterization of Cis-Tetracarbonyl(3,5-Dimethylpyrazol-1-Yl) Methanemolybdenum(0)

The title compound crystallizes in space group P 2₁/c of the monoclinic system in a cell of dimensions: a = 9.231(2), b = 15.931(2), c = 12.420(2) Å, β = 108.37(1)°. The observed density is 1.60 g/cm³ and the density calculated for four molecules in the cell is 1.58 g/cm³. The refinement converged with R = 0.029 and R_w = 0.028 based on 2569 reflections with I > 2.5 σ. The molecule has approximate C_s symmetry with a mirror plane roughly containing the central Mo atom and two cis-carbonyls, C(1)O(1) and C(4)O(4), while bisecting the bidentate, H₂CPz₂, and two trans-carbonyls. The four carbonyls and tine bidentate adopt a quasi-octahedral arrangement around the Mo atom. The C(NN)₂Mo linkage of the (H₂CPz′₂)Mo fragment is observed to be in the boat form. The two cis-carbonyls are bent away by the bulky H₂CPz′₂ bidentate giving ∠C(1)-Mo-C(4) ? 167.3(1)°. The distortion explains the facile allyl bromination and decarbonylation observed for the title compound.     

Organotransition-Metal Complexes of Multidentates 1. Synthesis and Characterization of N,N-Bis(Pyrazol-1-Ylmethyl)Aminomethane and N,N-Bis(3, 5-Dimethylpyrazol-1-Ylmethyl)-Aminomethane Derivatives of the Group VI Metal Carbonyls

N, N-bis(pyrazol-1-ylmethyl)aminomethane (bpam) and N, N-bis(3, 5-dimethylpyrazol-1-ylmethyl)aminomethane (bdmpam) reacted with M(CO)₆ or M(CO)₃(CH₃CN)₃ in acetonitrile to give respectively fac-(bpam)M(CO)₃ and fac-(bdmpam)M(CO)₃ in good yields (M=Cr, Mo, W). These complexes are characterized by elemental analysis, IR, and NMR and compared with the related polypyrazolylborate complexes of the group VI metal carbonyls.     

Synthesis of tricyclic aromatic compounds by the intramolecular pauson-khand reaction promoted by molecular sieves(,)(1)

Pauson-Khand reactions are carried out with different substituted aromatic enynes, yielding tricyclic cyclopentenones related to natural products such as chromenes. Enynes are easily obtained in a two-step approximation from the corresponding salicylaldehydes. The reaction is promoted by dissolved TMANO (trimethylamine N-oxide) and/or 4 A molecular sieves. This new way of induction for the Pauson-Khand reaction increases yields remarkably, allowing the reaction of some substituted alkenes which fail to react in the absence of the zeolite. Isomerization of the double bond of the cyclopentenone ring is observed except when nonterminal triple bonds are used. For trisubstituted alkenes, an interrupted Pauson-Khand process is observed with moderate yields.     

Organotransition-Metal Complexes of Multidentate Ligands 3. The Unexpected Derivatives of Bis(3,5-Dimethylpyrazol-1-YL)Methanetetracarbonylmolybdenlim(0) and-Tungsten(0) Complexes

Thermolysis of (H₂CPz′₂)M(CO)₄ (H₂CPz′₂ = bis(3,5-dimethylpyrazol-1-yl)methane; M=Mo, W) in 1,2-dimethoxyethane did not give the expected 16-electron complexes, (H₂CPz′₂)M(CO)₃, but gave dinuclear compounds, [(H₂CPz′₂)M(CO)₃]₂, probably containing two linear carbonyl bridges and no metal-metal interactions. The dimers reacted with CH₃CN to give mononuclear compounds, (H₂CPz′₂)M(CO)₃(NCCH₃), identical to the substitution products between (H₂CPz′₂)M(CO)₄ and CH₃CN.     

Novel Radical Cation Reactions of Bichromophoric Systems. Transannular Aryl Migrations; Mechanistic and Exploratory Organic Photochemistry(,)(1)(,)(2)

Eight aryl-substituted 1,4-pentadienes were subjected to photochemically induced electron transfer using dicyanonaphthalene and dicyanoanthracene. The radical-cations produced underwent a regioselective cyclization, wherein one electron-deficient aryl group of one diarylvinyl moiety bonds to the beta-carbon of the second diarylvinyl group. A pattern of regioselectivity and reactivity was encountered. As cyclization proceeds, the odd-electron density becomes localized in the benzhydryl side chain while the positive charge becomes localized in the second portion of the molecule. Substitution in one diarylvinyl branch designed to delocalize odd-electron density but destabilize electron deficiency led to higher reactivity than the unsubstituted parent 1,1,5,5-tetraphenyl-3,3-dimethyl-1,4-pentadiene. The benzhydryldihydronaphthalene photoproducts themselves proved photochemically reactive. On sensitization, the benzhydryldihydronaphthalene reacted with a transannular 1,5-migration of one aryl group of the benzhydryl moiety. Where the two benzhydryl aryl groups were different, the cyanophenyl group migrated in preference to phenyl, and both diastereomers led to the same product stereoisomer. Ab initio and semiempirical computations were in accord with the radical cation and triplet regioselectivity.     

Metallacarboranes of the C2B4-cage systems

A comprehensive review of the chemistry of polyhedral cluster complexes in whichs,p,d, andf-block metals are incorporated into C₂B₄-carborane cages to form the respective metallacarboranes is presented. The main focus of the review is directed toward systematizing the chemistry of metallacarboranes in order to promote their use as possible electronic, ceramic, and/or catalytic materials in addition to providing information on which we can test and expand our knowledge about the fundamental interactions that are at work in determining the structures and properties of these cluster complexes.     

聚酰胺46的合成与结构研究：1.合成条件对产物分子量的影响

合成了高性能工程塑料聚酰胺４６并进行了基本表征，讨论了界面缩聚和溶液－固相缩聚时，有机相溶剂类型，单体浓度比，固相缩聚温度、真空度、反应时间对产物分子量的影响。     

Studies on Dioxygen Adducts of Cobalt(II) Complexes with Salen-Analogs Containing A Pendant Group

Abstract

New cobalt(II) complexes ([Co(sal-P)]) with pentadentate salen-analogs possessing a pendant group capable of axial coordination have been synthesized and discussed with respect to coordination behavior of the pendant groups.     

Integrated Ion Exchange and Liquid-Liquid Extraction Process for the Separation of Platinum Group Metals (PGM)

A process for concentration and separation of platinum group metals (PGM) by a combination of ion exchange and liquid-liquid extraction is presented. First the PGM metals are dissolved by HC1/C1₁ and then passed through an isothiouronium anion exchange resin, where specific absorption occurs. The thiourea eluate from the resin is converted to the chloride complexes. Further hydrolysis (conditioning) yields an aqueous feed to a liquid-liquid extraction step, with Alamine-336. Platinum and palladium are very well extracted, while most of the other PGM are rejected in the aqueous phase. The liquid-liquid extraction can be used by itself, if the level of the base metals does not exceed the concentration of the PGM ions.

Platinum and palladium are now separated from each other by the selective stripping of palladium with thiourea, and platinum with thiocyanate.

The paper discusses the extraction chemistry of all the steps, and provides also experimental pilot-plant results.     

Complexes of Group III Metals based on o-Iminoquinone Ligands

Russian Journal of Coordination Chemistry - The currently available published data on the synthesis, structure, and chemical properties of Group III metal complexes based on bi-, tri-, and...     

Cobalt(II) Complexes of 4,6-Dimethylpyrimidine-2(1H)-one

Some cobalt(II) complexes of 4,6-dimethylpyrimidine-2(1H)-one (HL) have been prepared and studied by infrared and electronic spectra and by magneto-chemical and conductometric measurements. The ligand is coordinated through the unprotonated ring-nitrogen atom and in one case also through the carbonylic oxygen atom. The “blue” complexes [CoX₂ · 2HL] (X₂ = Cl₂, ClBr, Br₂, (NCS)₂) and [CoX₂ · 2HL] · 2HL (X = Cl, Br) have a distorted C_2v [CoX₂N₂] coordination; the thiocyanate ion is N-bonded to the metal. The “green” complexes CoX₂ · 2HL (X = Cl(4H₂O), Br) have a square-pyramidal [CoX₂N₂O] coordination. The “pink” CoX₂ · 4HL · nH₂O (X = ClO₄, n = 2; X = BF₄, n = 8; X = F₃Ac, n = 4) and “cream” CoX₂ · 4HL · 6 H₂O (X = I, ClO₄) complexes have an octahedral coordination; only the F₃Ac^? ion is coordinated. The “cyclamen” CoAcL · 2HL · 2 H₂O and Co₃Ac₄L₂ · 2HL · 2H₂O complexes have a polynuclear constitution; the Ac^? ion behaves as bidentate ligand.     

The Separation of Platinum Group Metals (PGM) in Chloride Media by Isothiouronium Resins

Styrene-divinylbenzene copolymers incorporating isothiourea functional groups show a remarkable affinity for platinum-group-metal (PGM) ions in chloride media, The mode of ion binding to the resin depends on the equilibria between isothiourea (free base) form and isothiouronium (conjugated acid) form, This in return is related to matrix structure, A. resin, Monivex, which shows high binding capacities for PGM ions in high acidities (2–6M HC1) is described. Equilibrium, rate and selectivity data, as well as process application data is presented and discussed, Electron microprobe studies are used to follow chemical changes in resin beads and ion regeneration patterns.