A Practical,One-Pot Preparation of Diisopinocampheylchloroborane

A one-pot preparation of the chiral reducing agent diisopinocampheylchloroborane (Ipc₂BCl) from Δ-pinene and borane methyl sulfide has been developed. The procedure obviates isolation of the air and moisture sensitive reagent, making it useful for large scale operations. Asymmetric reduction of ketones using the in situ prepared Ipc₂BCl is comparable to that using isolated reagent.     

A New Approach to the Efficient Method for the Asymmetric Synthesis of (S)-O-, M-, P-Fluorophenylalanines and Their 2-Methyl-substituted Analogs

Abstract

The reactions of asymmetric C-alkylation of glycine and alanine in Ni^II complexes of their Schiff's bases with modified chiral auxiliaries (S)-2-N-[(N′-2-chlorobenzylprolyl)amino]benzophenone and (S)-2-N-[N′-(3,4-dimethylbenzylprolyl)amino]benzophenone by fluorine-substituted benzyl halogenides have been studied. As a result, a highly stereoselective and relatively rapid method for the asymmetric synthesis of (S)-o-, m-, p-fluorophenylalanines and their 2-methyl substituted analogs has been developed.     

A new oxamato-bridged heterotrinuclear NiIICuIINiII complex: synthesis,structure and properties

A new oxamato-bridged Ni^IICu^IINi^II species, [Ni(iprtacn)]₂[Cu(pba)(H₂O)_0.5](BPh₄)₂ (1), (iprtacn?=?1,4,7-triisopropyl-1,4,7-triazacyclononane; pba?=?1,3-propylenebis(oxamato)) has been synthesized and structurally as well as magnetically characterized. Complex 1 has a discrete trinuclear Ni^IICu^IINi^II structure: Two nickel(II) ions are bridged by [Cu(pba)]^2? with the macrocyclic ligand iprtacn a terminal ligand of nickel(II). Fitting the magnetic data of 1 led to g _Cu?=?2.16, g _Ni?=?2.18, J?=??112.5?cm^?1, D?=?±7.78?cm^?1. The irregular spin state structure and interaction of complex 1with DNA are described here.     

Coordination of a mesogenic Schiff-base with Mn, Co, Ni, Cu and Zn: Synthesis, spectral studies and crystal structures

A novel mesogenic (nematic) Schiff-base, N,N′-di-4-(4′-pentyloxybenzoate)salicylidene diaminoethane, H₂dpbsde (abbreviated as H₂L⁵) was synthesized and its structure studied. The Schiff-base crystallizes in the non-centrosymmetric space group Pna2₁ with Z = 4, and the mesogenic isomorphous nickel and copper complexes, [NiL⁵]₂ and [CuL⁵], in the centrosymmetric space group P2₁/c with Z = 4. The (L⁵)²⁻ species coordinates to the metal ions through two phenolate oxygens and two azomethine nitrogens. Both the [NiL⁵]₂ and [CuL⁵] complexes involve cis-MN₂O₂ planes; the former complex has a low-spin distorted square-pyramidal geometry with a Ni–Ni bonding of 3.337 Å and the latter, a square-planar geometry.     

Molecular and Supramolecular Structures of a Nickel(II)–Copper(II)–Nickel(II) Trinuclear Complex Containing a New Macrocyclic Oxamido Complex Ligand

The title complex, [Cu(NiL)₂(H₂O)₂](ClO₄)₂, has been obtained by self-assembly, where [NiL] is a new macrocyclic oxamido complex ligand. In the crystal, a new kind of supramolecular interaction between the carbon atoms of the oxamido group of each [NiL] complex ligand in a [Cu(NiL)₂(H₂O)₂]^{2 +} cation and the oxygen atom of one of the ester carbonyls of another [Cu(NiL)₂(H₂O)₂]^{2 +} cation, and C—HO, O—HO and interactions are observed and link the trinuclear fragments and perchlorate ions to form a 3D supramolecular network.     

Syntheses and structures of two NiIICoIINiII complexes of macrocyclic ligands

Two new linear trinuclear complexes, [Co(NiL¹)₂(SCN)₂] (1) and [Co(NiL²)₂(H₂O)₂](ClO₄)₂?·?2C₂H₅OH (2), have been prepared by using Co(ClO₄)₂?·?6H₂O and two macrocyclic complex ligands NiL¹ and NiL². L¹ and L² are the doubly deprotonated forms of dimethyl 5,6,7,8,15,16-hexahydro-6,7-dioxodibenzo[1,4,8,11]tetraazabicyclo[12.4.0^15,16]13,18-dicarboxylate and dimethyl 5,6,7,8,15,16-hexahydro-15-methyl-6,7-dioxodibenzo[1,4,8,11]tetraazacyclotetradecine-13,18-dicarboxylate, respectively. X-ray single crystal analyses reveal the coordination geometries around Ni(II) in both 1 and 2 are identical and slightly distorted square planar with N₄ donors; all Ni–N bonds in the two complexes are very short. The Co(II) ions are at the centers of the trinuclear complexes and have distorted octahedral coordination geometries of O₄N₂ donors in 1 and an O₆ in 2. π?···?π interactions involving aromatic and non-aromatic π-systems join the trinuclear entities to form 2-D layers in the crystals of 1 and 2.     

5-(Pyridylmethylidene)-substituted 2-thiohydantoins and their complexes with CuII, NiII, and CoII: Synthesis, electrochemical study, and adsorption on the cystamine-modified gold surface

A series of Cu^II, Ni^II, and Co^II complexes with 5-(pyridylmethylidene)-substituted 2-thiohydantoins (L) were synthesized by the reactions of the corresponding organic ligands with MCl₂·nH₂O. The resulting complexes have the composition LMCl₂ (M = Cu or Ni) or L₂MCl₂ (M = Co). The reactions with N(3)-unsubstituted thiohydantoins afford complexes containing four-membered metallacycles, in which the metal ion is coordinated by the S and N(3) atoms of the thiohydantoin ligand. The reactions of N(3)-substituted thiohydantoins give complexes in which the S and N(1) atoms are involved in coordination. Study by IR spectroscopy demonstrated that the pyridine nitrogen atom is not involved in coordination. Based on the results of electrochemical study of the ligands and complexes by cyclic voltammetry and calculation of their frontier orbitals by the PM3(tm) method, the mechanism of oxidation and reduction of these compounds was proposed. In the first reduction and oxidation steps, the metal atom in the copper and nickel complexes remains, apparently, intact, and these processes occur with the involvement of the ligand fragments, viz., the coordinated thiohydantoin ligand and chloride anion, respectively. In the cobalt complexes, the first reduction step occurs at the ligand; the first oxidation state, at the metal atom. Measurements of the contact angle of aqueous wetting and electrochemical study demonstrated that carboxy-containing 2-thiohydantoins and their complexes can be adsorbed on the cystamine-modified gold surface. The structures of the complexes on the surface differ from the structures of these complexes in solution. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 978–990, June, 2006.     

Syntheses,structures, and properties of CdII and CoII complexes with 5-(pyridin-4-yl)isophthalate

A N-donor containing carboxylic ligand, 5-(pyridin-4-yl)isophthalic acid (H₂L), was applied to construct two new coordination polymers [Cd(L)(DMF)] _n (1, DMF?=?N,N-dimethylformamide) and {[Co(L)(H₂O)₂]?·?0.5CH₃OH?·?1.5H₂O} _n (2) under different conditions. The complexes were characterized by IR, elemental, and thermogravimetric analyses, powder and single crystal X-ray diffraction. In 1 each L^2? links four Cd^II to form a 3-D framework, while in 2 each L^2? connects three metals to form a 2-D layer structure, which is further connected together by hydrogen bonds to form a 3-D architecture. The thermal stability of the complexes and the photoluminescence of 1 were investigated.     

X-Ray Structural Analysis of NiII, PdII, and PtII Complexes with the Potentially Tridentate Ligand 1,3-Bis(diphenylphosphinomethyl)benzene, 1,3-C6H4(CH2PPh2)2

The ligand 1,3-bis(diphenylphosphinomethyl)benzene, 1,3-C₆H₄(CH₂PPh₂)₂ undergoes cyclometalation reactions, thus forming derivatives containing the tridentate moiety 2,6-bis(diphenylphosphinomethyl)phenyl,2,6-C₆H₃(CH₂PPh₂)₂. Complexes of the type trans-[MBr(C₆H₃CH₂PPh_{2 2})] with M = Ni^II, Pd^II, and Pt^II could be obtained and their crystal structures were here determined by X-ray diffraction (XRD) methods. The Ni complex belongs to the space group P2 ₁/c with a = 10.257(2), b = 16.234(5), c = 17.475(4) Å, = 109.34(2), and Z = 4. The Pd complex belongs to the space group P2 ₁/n with a = 10.325(3), b = 16.279(4), c = 17.303(4) Å = 105.34(3), and Z = 4. The Pt complex belongs to the space group P2 ₁/n with a = 10.127(2), b = 14.776(2), c = 19.023(3) Å, = 91.01(1), and Z = 4. Different distortions are induced by the rigid tridentate ligand on the square planar coordinations of the three metals. A significant difference between the two M-P bond distances is present in the Pt complex and can also be found in an analogous Pd complex.     

A kinetic study of the oxidation of hydroxamic acids by compounds I and II of horseradish peroxidase: Effect of transition metal ions

Abstract

Oxidation of hydroxamic acids (HXs) generates HNO, and it is not clear whether it is formed also in the presence of metal ions. The kinetics of the oxidation of HXs, such as acetohydroxamic acid, suberohydroxamic acid, and suberoylanilide hydroxamic acid (SAHA), by compounds I and II of horseradish peroxidase (HRP) at pH 7.0 and 25?°C have been studied using rapid-mixing stopped-flow. The kinetics of these reactions were compared to those observed in the presence of Cu(ClO₄)₂, NiSO₄, or ZnSO₄. The rates decrease upon increasing [Cu^II] at constant [HXs], and no oxidation of HX occurs when [HX]/[Cu^II] ≈ 2, implying that HX oxidation in the presence of Cu^II proceeds through the free ligand since the predominant complex is CuX₂. In the case of Ni^II, the oxidation rate decreases upon increasing the ratio [Ni^II]/[HX] beyond 1, where the predominant complex is Ni^IIX⁺, implying that its oxidation is feasible. The effect of Zn^II could be studied only on the rate of HXs oxidation by compound II demonstrating similar behavior to that of Ni^II. HXs were also oxidized catalytically by HRP/H₂O₂ at pH 7.0, demonstrating that metal ions facilitate the formation of HNO while hardly affecting its yield and the extent of HX oxidation.     

Halo-substituted (S)-N-(2-benzoylphenyl)-1-benzylpyrolidine-2-carboxamides as new chiral auxiliaries for the asymmetric synthesis of (S)-α-amino acids

The synthesis of new chiral auxiliaries (S)-N-(2-benzoylphenyl)-1-(3,4-dichlorobenzyl)-pyrrolidine-2-carboxamide (1a), (S)-N-(2-benzoylphenyl)-1-(pentafluorobenzyl)pyrrolidine-2-carboxamide (1b), and (S)-N-(2-benzoylphenyl)-1-(4-isopropoxytetrafluorobenzyl)pyrrolidine-2-carboxamide (1c) and their application in the asymmetric synthesis of amino acids using Ni^II complexes of their Schiff"s bases with alanine and glycine are described. Compound 1a is particularly appropriate for highly stereoselective synthesis of -methyl--amino acids with high enatiomeric purity (ee >95%).     

Asymmetric Synthesis of Perfluoroalkylated α-Amino Acids through Generated Radicals Using a Chiral Ni(II) Complex

Perfluoroalkylated α-amino acids (PFAAs) are a unique class of compounds for biochemistry and pharmaceutical science. In this context, we report the successful intermolecular coupling of the Belokon’s chiral dehydroalanine Ni(II) complex with a variety of perfluoroalkyl iodides. A 4-cyanopyridine/B₂Pin₂ catalytic system generates perfluoroalkyl radicals, which after trapping by the ligand sphere of a chiral Ni(II) complex provide the diastereomeric complexes with up to >20 : 1 dr (seven examples). The obtained major (S,S)-diastereomers were easily isolated by simple silica column chromatography in 33–54 % yields. The perfluoroalkylated α-AA was subsequently released from the obtained Ni(II) complex through aqueous HCl treatment. The chiral auxiliary ligand ((S)-BPB=(S)-2-(N-benzylprolyl)aminobenzophenone) can be easily recycled after the acidic complex decomposition and reused for the synthesis of the starting dehydroalanine Ni(II) complex.     

Hydrothermal synthesis, crystal structures, and properties of Co and Ni supramolecular complexes with 2,4,6-trimethyl benzoate and 4,4′-bipyridyl

Two new coordination complexes, viz. [Co(tmb)₂(4,4′-bpy)₂(H₂O)₂](Htmb)₂ (1) and {[Ni(tmb)₂(μ-4,4′-bpy)₂(H₂O)₂](4,4′-bpy)}_n (2), have been hydrothermally synthesized by reaction of the corresponding metal acetate with 2,4,6-trimethylbenzoic acid (Htmb) and 4,4′-bipyridyl (4,4′-bpy). X-ray single-crystal diffraction suggests that complex 1 represents a discrete mononuclear species in which the central metal ion is coordinated by the terminal carboxylate moiety and the 4,4′-bipyridyl ligand. The crystal structure of complex 2 reveals a 1D chain coordination polymer in which the Ni(II) ions are connected by the bridging 4,4′-bipyridyl ligands. In both cases, the coordination arrays are further extended via hydrogen bonding interactions to generate 3D supramolecular networks. Complexes 1 and 2 have also been characterized by spectroscopic (IR and UV/Vis), thermal (TGA) and magnetic susceptibility measurements. In addition, both complexes exhibit antimicrobial activity.     

Structural and physicochemical characteristics of chelate nickel(II) compounds based on 1,2,3-triketone (hydrazone)imines

The crystal structures of the chelates Ni^IIL (L²⁻ are the N,N′-(o-phenylene)-bis[4-(4-methylphenyl)hydrazono-3-oxo-1,1,2,2-tetrafluorononane-5-iminate], N,N′-ethylene-bis[3-(4-methylphenyl)hydrazono-4-oxo-5,5,6,6,7,7,8,8-octafluorooctane-2-iminate], or N,N′-ethylene-bis(4-hydroxy-5,5,6,6,7,7,8,8-octafluoro-3-octene-2-iminate) anions) were studied by X-ray diffraction. Magnetic measurements and ESR spectroscopic studies revealed the appearance of paramagnetism due to a tetrahedral distortion of the coordination unit and also the unusual behavior of the effective magnetic moment at low temperatures. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 103–109, January, 2007.     

The Synthesis of Novel S-, S,S-, S,S,S-, and N,S-Substituted Nitrodienes from Polyhalonitrodienes and Thiols

Abstract

The novel S-, S,S-, and S,S,S-substituted nitrobutadienes were synthesized from the reactions of 2-nitrobutadiene compounds with some thiols. The new N,S-substituted nitrobutadienes were obtained from the reaction of the mono-thiosubstituted butadienes with morpholine, thiomorpholine, homopiperazine, and piperazine derivatives. The structures of new compounds were determined by spectroscopic techniques.

GRAPHICAL ABSTRACT      

双(取代水杨醛)间苯二甲酰腙有机锡配合物的一锅溶剂热法合成、结构和荧光性质

以间苯二甲酰肼、取代水杨醛和有机锡前体化合物进行一锅溶剂热法反应,合成了5个双(取代水杨醛)间苯二甲酰腙有机锡配合物m-Ph (CONH—N=CH (o-O) PhR¹)(SnR²)²： R¹=Naphth,R²=Cy (1); R¹=3-t-Bu,R²=n-Bu (2); R¹=5-F,R²=Ph (3); R¹=4-Cl,R²=Ph (4); R¹=3-t-Bu,R²=Ph (5)。经元素分析、红外光谱、(¹H、¹³C和¹¹⁹Sn)核磁共振谱表征,并用X射线衍射方法确证了配合物1~5的晶体分子结构。配合物1~4为三斜晶系P>1空间群,配合物5为单斜晶系P2₁空间群。中心锡与配位原子组成五配位畸形三角双锥构型。将水杨醛酰腙链与有机锡配位形成远离中心苯环的构型称为“反式”,将与中心苯环取向相同的构型称为“顺式”。通过C1—C2或C4—C8单键旋转,中心苯环上的2个配位链发生构型翻转。配合物1形成“反-反”式构型,配合物2形成“顺-顺”式构型,配合物3、4和5形成“顺-反”式构型。荧光研究表明,配合物具有发光性能,特别是配合物1和4的有机溶液具有很强的荧光性能。     

双(取代水杨醛)间苯二甲酰腙有机锡配合物的一锅溶剂热法合成、结构和荧光性质

以间苯二甲酰肼、取代水杨醛和有机锡前体化合物进行一锅溶剂热法反应,合成了5个双（取代水杨醛）间苯二甲酰腙有机锡配合物m-Ph （CONH-N=CH （o-O） PhR¹）（SnR²）₂：R¹=Naphth,R²=Cy （1）; R¹=3-t-Bu,R²=n-Bu （2）; R¹=5-F,R²=Ph （3）; R¹=4-Cl,R²=Ph （4）; R¹=3-t-Bu,R²=Ph （5）。经元素分析、红外光谱、（¹H、¹³C和¹¹⁹Sn）核磁共振谱表征,并用X射线衍射方法确证了配合物1~5的晶体分子结构。配合物1~4为三斜晶系P1空间群,配合物5为单斜晶系P2₁空间群。中心锡与配位原子组成五配位畸形三角双锥构型。将水杨醛酰腙链与有机锡配位形成远离中心苯环的构型称为"反式",将与中心苯环取向相同的构型称为"顺式"。通过C1-C2或C4-C8单键旋转,中心苯环上的2个配位链发生构型翻转。配合物1形成"反-反"式构型,配合物2形成"顺-顺"式构型,配合物3、4和5形成"顺-反"式构型。荧光研究表明,配合物具有发光性能,特别是配合物1和4的有机溶液具有很强的荧光性能。     

A Convenient Laboratory Preparation of N,N-Dimethyl-dichloro-methylene-iminium Chloride (Phosgene-iminium chloride)

A method of preparation of the title compound 1a avoiding the use of gaseous chlorine is described. Tetramethylthiuram disulfide 4 is oxidized with sulfuryl chloride to dime thyl thiocarbamoyl chloride 5, which is converted to 1a by means of phosphorus pentachloride.     

Synthesis, crystal structure, spectroscopy and magnetic properties of a dinuclear Cu complex with 3,5-bis(2-pyridyl)pyrazole bridging ligand

A dinuclear Cu^II complex [Cu₂(bpp)₂(H₂O)₂](ClO₄)₂ (1) with 3,5-bis(2-pyridyl)pyrazole (Hbpp), has been synthesized and characterized by elemental analyses, thermal analysis, conductance, UV-vis and IR spectra. The crystal structure of 1, determined by X-ray diffraction technique, reveals that two centrosymmetric Cu^II centers are bridged by a pair of tetradentate anionic bpp ligands, adopting a square-pyramidal environment with the water ligand occupying the axial site. An interesting feature of this structure is the formation of a two-dimensional supramolecular network through O-H?O hydrogen bonds between the water moieties of the cationic [Cu₂(bpp)₂(H₂O)₂]²⁺ subunits and perchlorate anions. The magnetic properties of 1 have been investigated by variable-temperature magnetic susceptibility and EPR measurements. Very strong antiferromagnetic interaction between the Cu^II centers (with H=−JS₁S₂, J=−368.3 cm⁻¹) has been observed, and the magneto-structural correlations was analyzed.     

Synthesis of Chiral Aromatic Alcohols: Use of New C2-Symmetric RhIIICp∗, RuII(cymene), or RuII(benzene) Complexes Containing Chiral Diaminocyclohexane Ligand as Asymmetric Transfer Hydrogenation Catalyst

Abstract

Twelve chiral secondary alcohols were synthesized by asymmetric transfer hydrogenation (ATH) using C₂-symmetric bis(sulfonamide) ligand (2) derived from (1R,2R)-cyclohexane-1,2-diamine and complexed with [RhCl₂Cp?]₂, [RuCl₂(cymene)]₂, or [RuCl₂(benzene)]₂ and then used in situ in the reduction of prochiral ketones. The alcohols were obtained in 85–99% yield and 90–99% enantioselectivity with isopropanol as the hydrogen source. Two-fold rate enhancement and better yields were achieved (88–99%) with 80–99% enantioselectivity using the complex [RhCl₂Cp?]₂ and aqueous sodium formate as the hydrogen source.