Dynamic 1H NMR study around the carbon-carbon single bond and partial carbon-carbon double bond in the two particular phosphorus ylides and in an enaminoester

Herein, a series of separate dynamic (1)H NMR effects are reported at different temperatures within a particular enaminoester involving a phenanthridine. These effects are attributed to restricted rotation around the two single bonds such as carbon-carbon (H(a)-C-C-H(b)) and nitrogen-carbon (NCCOOCH(3)). Activation energies (E(a)) for these interconversion processes in their rotational isomers are equal to 20 and 20 ± 1 kJ mol(-1), respectively. In addition, three dynamic (1)H NMR effects are investigated at different temperatures for a particular phosphorus ylide involving a 2-indolinone around the carbon-carbon single bond (H-C-C-PPh(3)) within the two Z- and E-rotational isomers and partial carbon-carbon double bond (OCH(3)-C=C-PPh(3)). Activation energies (E(a)) for these interconversion processes in rotational isomers are equal to 53, 63 and 73 ± 1 kJ mol(-1) , respectively. This behavior was also observed for other phosphorus ylide containing 2-mercaptobenzoxazole around the carbon-carbon single bond and partial carbon-carbon double bond with their relevant activation energies containing 13, 10 and 75 ± 1 kJ mol(-1), respectively.     

Synthesis,crystal structure and electrochemical properties of carbonylchromium and tungsten complexes containing substituted pyrazole ligands

A series of carbonylchromium and tungsten complexes containing substituted pyrazole ligands, M(CO)₅L, have been synthesized by the photochemical reactions of substituted pyrazoles with M(CO)₆ (M = Cr or W). Their electrochemical behavior, investigated by cyclic voltammetry, indicates that the chromium complexes exhibit one reversible or quasi-reversible couple corresponding to a one-electron oxidation, whereas the tungsten complexes have one irreversible oxidation process. The crystal structure of W(CO)₅L [L = 3(5)-t-butylpyrazole] was determined by X-ray diffraction, indicating that 3(5)-t-butylpyrazole is a monodentate ligand, and that the central metal is six-coordinate with a quasi-octahedral coordination geometry. All new compounds were characterized by elemental analyses, i.r., ¹H-n.m.r. and by ¹³C-n.m.r. in the case of the tungsten complexes.     

Allylic carbon-carbon double bond directed Pd-catalyzed oxidative ortho-olefination of arenes

Pd-catalyzed selective ortho-olefination of arenes assisted by an allylic C-C double bond at room temperature using O(2) as a terminal oxidant is described. A possible mechanism involving the initial coordination of allylic C═C bond to Pd followed by selective o-C-H bond metalation is proposed.     

含吡唑配体的VIB金属羰基配合物的合成与电化学性质研究

研究了吡唑类配体与M(CO)6(M=Cr,W)的光化学反应,合成了一系列的含吡唑配体的五羰基铬钨配合物。研究了该类化合物的电化学性质。结果表明：铬系列化合物存在一对准可逆的氧化还原峰,而钨系列化合物只存在一个不可逆的氧化峰,用X射线单晶衍射测定了化合物3,4,5－三甲基吡唑五羰基铬的晶体结构。该晶体为单斜晶系,空间群为P2(1)/m,晶胞参数为a=0.9106(3)nm,b=07627(2)nm,c=0.9637(3)nm,β＝91.855(5)°,V=0.6689(3)nm^3,Z=2,R=0.042,Cr为六配位的变形八面体构型。     

Synthesis and characterization of two isomeric liquid crystal series with reactive double bonds

Two series of potentially cross-linkable liquid crystal materials derived from p-phenylenebisacrylic (series I, n(P.FB.P), n = 2-10) and p-hydroxycinnamic acid (series II, n(HC.T.HC), n = 2-10) have been synthesized and their thermal and mesomorphic properties studied. All these compounds show enantiotropic mesomorphism over a wide range of temperatures. Compounds with short terminal chains are nematic and when the terminal chain length is increased they show smectic polymorphism-smectic A and C. Most of the compounds are thermally stable over their mesophase ranges.     

X-ray crystal structures of two solvent complexes involving positionally isomeric 9,10-anthraquinonecarboxylic acids and DMSO

Two constitutionally isomeric 9,10-anthraquinonecarboxylic acids 1 and 2 are reported to yield DMSO-solvated crystals (1a and 2a) on the crystallization from DMSO. The molecular and crystal structures are described and comparatively discussed with reference to the effect implicated by the different position of the carboxylic group at the anthraquinone basis and the involvement of the solvent molecule.     

Catalytic arylation of carbon-carbon double bond followed by N- or O-cyclization

Under the catalytic action of palladium,o-hydroxy- oro-amino-substituted aryl iodides oxidatively add to palladium(0), insert strained or rigid olefins, and close the ring between the aliphatic carbon and theortho-functional group. This reaction occurs under mild conditions in the absence of phosphine ligands in a DMF solution and affords fused dihydrofurans or-pyrroles.     

Synthesis, X-ray structure and anti-corrosion activity of two silver(I) pyrazino complexes

Two new silver(I) pyrazine complexes [Ag₂(ampyz)(NO₃)₂]_n, 1 and {[Ag(2,3-pyzdic)](NO₃)}_n, 2 (where ampyz = aminopyrazine, and 2,3-pyzdic = 2,3-pyrazinedicarboxamide) were synthesized and structurally characterized by X-ray single crystal structure analysis. Complex 1 has a 2D sheet structure through both bridging μ_O,O′-(NO₃) groups and μ_N,N′-pyrazine moieties. A 3D structure with a characteristic (10,3)-d or 10³-utp net is formed through extensive hydrogen bonding. Complex 2 has a 1D chain structure through bridging μ_N,N′-pyrazine moieties. Strong hydrogen bonds further connect these chains to extend the dimensionality to a 3D network structure. The complexes were tested as corrosion inhibitors for mild steel in 0.1 M nitric acid medium using potentiodynamic polarization technique. Both complexes are of mixed type corrosion inhibitors with dominant anodic effect. The inhibition efficiencies are 68% and 50% for complexes 1 and 2, respectively. The inhibition mechanisms of both inhibitors are mainly due to adsorption of the inhibitor molecules on the surface of mild steel. All data were compared and fitted to the kinetic-thermodynamic model. The binding constants K are 3263 and 1147 for complexes 1 and 2, respectively.     

Synthesis and structure of isomeric palladium(II)-pyrazole chelate complexes with and without an N-H group as hydrogen bond donor

Four new ligands containing a pyrazole ring and either a phosphine or thioether were prepared and converted to their cis-dichloropalladium(II) complexes. Two of the ligands are especially notable for the attachment of a side chain at pyrazole carbon, rather than at nitrogen. The new metal complexes include dichloro[3-(diphenylphosphinomethyl)pyrazole]palladium(II) (1-PdCl2) and dichloro[3-(methylthiomethyl)pyrazole]palladium(II) (2-PdCl2), which both feature an N-H group as a potential proton or hydrogen bond donor. For comparison, isomeric complexes lacking an NH group were prepared: dichloro[1-(diphenylphosphinomethyl)pyrazole]palladium(II) (3-PdCl2) and dichloro[1-(methylthiomethyl)pyrazole]palladium(II) (4-PdCl2). As determined by X-ray crystallography, all four complexes were found to have slightly distorted square planar geometry. Complexes 1-PdCl2 and 2-PdCl2, which contain an NH group, exhibit both intermolecular and intramolecular hydrogen bonding, whereas isomers 3-PdCl2 and 4-PdCl2 do not. Single-crystal X-ray structure determinations on the following compounds are reported: 1-PdCl2, space group P1, a = 8.4488(9) A, b = 8.9175(13) A, c = 12.731(2) A, Z = 2, V = 871.8(2) A3; 2-PdCl2, space group Pbca, a = 10.8827(10) A, b = 11.7721(7) A, c = 14.874(2) A, Z = 8, V = 1905.6 A3; 3-PdCl2, space group P2(1)/c, a = 20.520(2) A, b = 12.549(2) A, c = 13.9784(13) A, Z = 8, V = 3401.1(6) A3; 4-PdCl2, space group Pbca, a = 10.6545(10) A, b = 12.0205(11) A, c = 14.6474(14) A, Z = 8, V = 1875.9(3) A3.     

Synthesis of two isomeric dimethylthiazolophenothiazines

Two condensed four-ringed heterocyclic bases—2, 10-dimethylthiazolo[4, 5-b]phenothiazine and 2, 6-dimethylthiazolo[4, 5-c]pheno-thiazine-have been synthesized. The structure of the new heterocycles has been confirmed by their IR and UV spectra.     

Synthesis and X-ray structure of an unexpected bidentate allene-aminocarbene complex of tungsten

This contribution describes the results obtained from the alkylation reaction upon base-induced of propargyl bromide at nitrogen of Ferrocenyl-N-pentylaminocarbene of tungsten, chromium and molybdenum. This led to unexpected highly strained Fischer-type carbene complexes (5a-c) containing a bidentate allene-aminocarbene ligand. This is the first report of the η²-allene Fischer carbene complexes. The structure of 5a was confirmed by an X-ray diffraction analysis.     

Synthesis and molecular structure of titanium complexes containing a reduced TEMPO radical

Two titanium compounds containing monoanionic ligands derived from TEMPO were synthesized and structurally characterized, demonstrating the flexibility of the coordination modes adopted by the ligand.     

Synthesis and characterization of tungsten carbonyl complexes containing N-methyl substituted urea and thiourea ligands

Six new mixed-ligand tungsten carbonyl complexes containing N-methyl substituted urea and thiourea of the type W(CO)₄[RCH₂N-(C=X)NH₂] where X?=?O or S and R?=?morpholine, piperidine and diphenylamine are reported. These have been prepared by refluxing hexacarbonyl tungsten(0) with corresponding ligands in THF to produce cis-disubstituted products, [(L-L)W(CO)₄] where L-L?=?a chelating bidentate ligand, morpholinomethyl urea (MMU), morpholinomethyl thiourea (MMTU), piperidinomethyl urea (PMU), piperidinomethyl thiourea (PMTU), diphenylaminomethyl urea (DAMU) and diphenylaminomethyl thiourea (DAMTU). The compounds have been characterized by elemental analysis, IR, electronic and ¹³C NMR spectra, magnetic moments and conductivity measurements. The IR spectra suggests that in all the complexes, the ligands are bidentate chelating, coordinating the metal through carbonyl oxygen or thiocarbonyl sulphur and the ring nitrogen or tert-nitrogen of diphenylamine. The CO force constants and CO–CO interaction constants for these derivatives have also been calculated using Cotton–Kraihanzel secular equations, which indicate poor π-bonding ability of the ligands. ¹³C NMR and electronic spectra reveal loss of cis-carbonyl ligands to produce cis-disubstituted tetracarbonyl derivatives. Molecular modeling studies have been carried out using Hyperchem release 7.52 which suggest a distorted octahedral geometry for these complexes.     

Synthesis, spectroscopic characterization and X-ray studies of two novel double open cubane-like cadmium(II) complexes

Two novel azide cadmium(II) compounds [Cd₄(dafone)₄Cl₂(μ_1,1-N₃)₄(μ_1,1,1-N₃)₂] (1) and [Cd₄(dafone)₄(N₃)₂(μ_1,1-N₃)₄(μ_1,1,1-N₃)₂] (2) were synthesized and characterized by spectroscopic and crystallographic methods. They are first cadmium(II) complexes adopting double open cubane-like structure. The fluorescence properties of the complexes 1 and 2 were examined both in solid state and solution, and compared with the free ligand. Additionally, the electronic spectra of 4,5-diazafluoren-9-one and 1 were investigated at the TDDFT level.     

Photochemical route to cembranoids containing a cis-disubstituted double bond

The 2-cis isomers of the natural diterpenoids isocembrol, 4-epiisocembrol, and isocembrene have been synthesized from a norcembrane ketone by the use of photochemical methods.Novosibirsk Institute of Organic Chemistry, Siberian Branch, USSR Academy of Sciences. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 180–187, March–April, 1988.     

含Fe3S3簇核的两个异构体化合物的合成和结构研究

用氯化亚铁、苯硫酚钠及溴化四乙基铵在乙腈溶液中, 经一步反应, 得到两个同分异构的化合物α-[Et4N]3[Fe3(PhS)3Cl3Br3]1和β-[Et4N]3[Fe3(PhS)3Cl3Br3]2. X射线晶体结构测定表明, 1和2的阴离子骨架为3Fe、3S交叉排列的六元环, 前者为扭船型,后者为椅型. 1属单斜晶系, 空间群C2/c, 晶胞参数: a=24.569(4), b=13.504(2),c=18.348(3)埃, β=110.78(1)°. Z=4, R=0.070. 2属三方晶系, 空间群P3cl, 晶胞参数: a=b=13.720(3), c=35.748(5)埃, Z=4, R=0.059. 讨论了反应和结构特点.