Coordination compounds of disulphur dinitride

Summary Coordination compounds of the S₂N₂ molecule including methods for their preparation, reactivities, i.r. data, structures, and aspects of chemical bonding are reviewed. Methods of synthesis include reactions of S₂N₂, S₄N₄ or (NSCl)₃ with metal halides, metal complexes such as carbonyls, or even metals themselves. In all cases, the planar S₂N₂ ring is coordinated, usuallyvia both, of its nitrogen atoms so that S₂N₂ acts as a bridging ligand between two metal centres; short contact distances imply that halogen atoms linked to the metal atoms show some interaction with the sulphur atoms. The stability of S₂N₂ is greatly enhanced by coordination. In the i.r. spectra, two characteristic S₂N₂ vibrations assist identification of the S₂N₂ species, a ring stretching mode being observable atca. 850 cm^–1 and the out-of-plane deformation at 450–490 cm^–1.     

Versuche zur Darstellung von t‐BuCN5S3 und die unerwartete Isolierung einer kovalenten Modifikation von Tetraschwefelpentastickstoff‐chlorid S4N5Cl

Attempts to prepare t‐BuCN₅S₃ and the unexpected Isolation of a covalent Modification of Tetrasulfur‐pentanitrogen Chloride S₄N₅Cl Attempts to prepare the bicyclic sulfur‐nitrogen heterocycle t‐BuCN₅S₃ via (NSCl)₃ and the corresponding silylated amidinates and amidines failed because of the inaccessibility of the silylated intermediates. Reactions of MN(SiMe₃)₂ (M = Li, Na) with t‐BuCN did not yield the expected amidinates t‐BuC(NSiMe₃)₂M, instead the adducts [t‐BuCN·MN(SiMe₃)₂]₂ were isolated. The attempted synthesis of t‐BuCN₅S₃ from t‐BuCN(SiMe₃)₂M, prepared in situ from t‐BuLi and Me₃SiNCNSiMe₃, and (NSCl)₃ unexpectedly resulted a mixture of S₄N₅Cl and S₅N₆. The crystal structure determination for S₄N₅Cl showed a new covalent modification of S₄N₅Cl (monoclinic, P2₁/c, a = 1005.0(4) pm, b = 1193.5(8) pm, c = 1152.5(6) pm, β = 93.67(3)°), different from the known ionic S₄N₅Cl (orthorhombic, Pnma, a = 1738.90(10) pm, b = 781.50(10) pm, c = 483.03(5)). The unsuccessful attempts to prepare t‐BuCN₅S₃, the unexpected formation of S₄N₅Cl and S₅N₆, and the bonding properties of the new covalent modification of S₄N₅Cl are discussed.     

CARBODIPHOSPHAN (2.4.6-tBu3C6H2[sbnd]P[dbnd]2)C: REAKTION MIT ELEKTROPHILEN

Abstract

The reaction of Ar[sbnd]P[dbnd]C[dbnd]P[sbnd]Ar (Ar=2.4.6-^tBu₃C₆H₂) with electrophiles (H⁺, S₈) proceeds at the phosphorus atom with subsequent cyclisation of an o-^tbutyl group.     

Asymmetrical Schiff Bases as Carriers in PVC Membrane Electrodes for Cadmium (II) Ions

5‐[((4‐Methyl phenyl) azo)‐N‐(6‐amino‐2‐pyridin) salicylaldimine] (S₁), and 5‐[((4‐methyl phenyl) azo)‐N‐(2‐diamino‐2‐cyano‐1‐ethyl cyanide) salicylaldehyde] (S₂) with N and O donor atoms are effective ionophores to make Cd²⁺‐selective membrane electrodes. The electrodes based on S₁ and S₂ exhibits a Nernstian or near‐Nernstian response for cadmium ion over a wide concentration range 1.5×10^?1–7.5×10^?7 with a slope of 28 and 2.0×10^?1–4.0×10^?7 with a slope of 22, respectively. They have quick response and can be used for three or four months without any divergence in potential. The proposed sensors show fairly good selectivity over some alkali, alkaline earth, transition and heavy metal ions. The electrodes based on S₁ and S₂ can be used in the pH range 3.5–9. These electrodes were used as an indicator electrode in potentiometric titration of cadmium ion with EDTA and in the direct determination of cadmium ion in aqueous solutions.     

ON THE REARRANGEMENT OF N-ARYL SULFIMIDES

Abstract

N-Aryl-S,S-dialkylsulfimides, 1, with R¹ = alkyl other than CH₃, have been rearranged by heating in ethanol yielding o-alkylthiomethyl-anilines, 2, as main products. Isomeric o-methylthioalkyl-anilines, 14, are formed in minor amounts only. Reactions of sulfimides, 1, with R¹ = CH₃, with certain alkylating or acylating agents yielded o-methylthiomethylated, N-alkylated or -acylated products 9. Mechanistic considerations are discussed. The rearrangement of sulfimides 1 has been assumed to occur via [2,3]-sigmatropic reactions of intermediate azasulfonium ylids 3. Attempts to resolve (+)-camphor-10-sulfonates of N-aryl sulfimides failed, but optically active N-aryl sulfimides could be obtained by reaction of anilines with optically active sulfoxides and P₄O₁₀. Optically active 2,6-disubstituted sulfimides, 1, could be rearranged in ethanolic KOH to yield optically active cyclohexadienimines 12, indicating a transfer of asymmetry from sulfur to carbon and supporting the assumption of a sigmatropic rearrangement.     

Chromium(III), manganese(II), iron(III), cobalt(II), nickel(II) and copper(II) complexes with a pentadentate, 15-membered new macrocyclic ligand

Complexes of Cr^III, Mn^II, Fe^III, Co^II, Ni^II and Cu^II containing a macrocyclic pentadentate nitrogen–sulphur donor ligand have been prepared via reaction of a pentadentate ligand (N₃S₂) with transition metal ions. The N₃S₂ ligand was prepared by [1 + 1] condensation of 2,6-diacetylpyridine with 1,2-di(o-aminophenylthio(ethane. The structures of the complexes have been elucidated by elemental analyses, molar conductance, magnetic susceptibility measurements, i.r., electronic and e.p.r. spectral studies. The complexes are of the high spin type and are six-coordinate.     

Seven-coordinate iron(II) complexes of sulfur-based N3S2-macrocyclic ligands: synthesis,properties, and crystal structure

The reaction of pyridine-2,6-dicarbaldehyde or 2,6-diacetylpyridine with 1,2-bis(o-aminophenylthio)ethane (1) in acetonitrile in the presence of stoichiometric amounts of iron(II) perchlorate gave the complexes [(pyN₃S₂)Fe^II(ClO₄)₂] (4) and [(pyN₃Me₂S₂)Fe^II(ClO₄)₂] (5) of the 15-membered N₃S₂ macrocyclic ligands, pyN₃S₂ ?=?{6,7-dihydro-15,19-nitrilobenzo(e,p)(1,4,7,15)dithiadiazacyclo-heptadecine-N,N′,N″,S,S′} and pyN₃Me₂S₂?=?{6,7-dihydro-16,18-dimethyl-15,19-nitrilobenzo(e,p)(1,4,7,15)dithiadiazacyclo-heptadecine-N,N′,N″,S,S′}, respectively. Physical measurements led to the conclusion that these complexes contained seven-coordinate iron(II) and a single-crystal X-ray examination of 4 confirmed this. Coordination of the Fe(II) center in 4 is best described as distorted pentagonal-bipyramidal with the three nitrogen atoms and two sulfur donors of the macrocycle defining the pentagonal plane and the perchlorate ions occupying axial positions. Room temperature (293?K) magnetic moments of 4 and 5 (μ _eff?=?4.9 and 4.7 B.M., respectively) are close to the value predicted for high-spin d⁶ systems.     

Cobalt-catalyzed C–N,C–O,C–S bond formation: synthesis of heterocycles

In recent decades, a large number of reports related to the synthesis of N-, O- and S-containing heterocycles have appeared owing to a wide variety of their biological activity. Traditional approaches require expensive or highly specialized equipment or would be of limited use to the synthetic organic chemist due to their highly inconvenient approaches. New strategies have been developed for the preparation of heterocycles in the last decades. Metal and non-metal catalysts are used in organic reactions with high activity. These synthetic strategies are becoming important and highly rewarding protocols in organic synthesis. In this review article, the synthesis of heterocycles is presented with the application of cobalt metal as a catalyst. It describes the formation of different sized heterocyclic rings containing different heteroatoms.

     

RINGCLOSURE REACTIONS WITH CARBON SUBSULFIDE

Abstract

Carbon suboxide has been used frequently in organic synthesis,¹ especially in the synthesis of heterocyclic compounds not obtainable by other routes. Although carbon subsulfide is known for more than 80 years, until recently only a few simple derivatives such as dithiomalonamides were prepared. The reason for this situation arises from the difficulties encountered in the preparation of C₃S₂. We have recently described a modification of the known preparation procedures, taking advantage of commercially available glassware (Quickfitt)².     

ELECTRON-RICH THIAZENES: SOME PRINCIPLES OF SYNTHESIS AND STRUCTURE

Abstract

General methods of preparation and typical bond distances and bond angles (at sulfur and nitrogen) are reviewed for cyclic sulfur–nitrogen compounds. Correlations between sulfur-nitrogen bond distance and unstrained bond angles in SNS and NSN groups can be used to assess angular strain in 4 and 5 atom thiazene rings and the optimum ring geometries of larger thiazene cations such as S₅N⁺ ₅ and S₄N_{2+ 4}. The geometry of S₃N^? ₃ is also discussed.     

Cyclization of N-alkyldithiocarbamates in alkaline media,a counter example of well-known chemistry – an experimental and theoretical study

In strong alkaline media, the reaction of 2-(tert-butylamino)ethanol (3: R?=?Bu^t) with CS₂ at 0°C produced a cyclic dithiocarbamate, 3-tert-butylthiazolidine-2-thione (1: R?=?Bu^t), rather than alkaline metal or ammonium salts of [S₂CN(Bu^t)CH₂CH₂OH]^?. This is in contrast to isolation of stable alkaline metal or ammonium salts of [S₂CN(R)CH₂CH₂OH]^? (R?=?Me, Et, Pr, or CH₂CH₂OH) obtained in analogous reactions. The use of Ni(OAc)₂, both as a source of Ni(II) and a weaker base, in a one-pot reaction with (3: R?=?Bu^t) and CS₂, successfully gave the first reported metal complex of [S₂CN(Bu^t)CH₂CH₂OH]^?, namely [Ni{S₂CN(Bu^t)CH₂CH₂OH}₂] (2: R?=?Bu^t). Compounds 1 and 2 have been fully characterized by infrared and NMR spectroscopies, and by X-ray crystallography. DFT calculations on the cyclization and stabilities of [S₂CN(R)CH₂CH₂OH]^? (R?=?Pr and Bu^t) have been carried out.     

The Synthesis of Some New Sulfur-Bearing Various Heterocyclic Systems Derived from Asymmetrical N,N′-Disubstituted Thiourea Derivatives

The heterocyclization of an asymmetrical N,N′-disubstituted thiourea (1a–d) in ring closure reactions with Br₂/AcOH, ethyl chloroacetate, diethyl oxalate, diethyl malonate, and hydrazine hydrate led to the direct formation of sulfur-bearing various heterocyclic systems (2–8) in which the thiaenolization is toward the aryl group. The synthetic work and reactivity investigations have been well supported by standard modern spectroscopic techniques (IR, ¹ H NMR, ¹³ C NMR, mass spectrum, and microanalysis).     

Defluorinative C(sp3)−P Bond Construction for the Synthesis of Phosphorylation gem‐Difluoroalkenes under Catalyst‐ and Oxidant‐Free Conditions

Defluorinative C(sp³)?P bond formation of α‐trifluoromethyl alkenes with phosphine oxides or phosphonates have been achieved under catalyst‐ and oxidant‐free conditions, giving phosphorylation gem‐difluoroalkenes as products. α‐Trifluoromethyl alkenes bearing various of aryl substituents such as halogen, cyano, ester and heterocyclic groups are available in this transformation. The results of control experiments demonstrated that the mechanism of dehydrogenative/defluorinative cross‐coupling reactions was not a radical route, but might be an S_N2′ process involving phosphine oxide anion.     

New asymmetric N2S2 macrocycles,their metal chelates and the photokinetics of DNA-complex interaction

New asymmetric ligands have been synthesized by condensing o-phenylene diamine with CS₂ and PhCHO/MeCHO, and their complexes with Mn^II, Co^II, Ni^II, Cu^II and Zn^II were prepared and characterized by elemental analyses, conductivity measurements, i.r., u.v.–vis., e.p.r. and n.m.r. spectra. The transition metals in the complexes show square planar geometry and are ionic. Photokinetic studies of the DNA-metal complexes [C₁₀H₁₀S₄N₂Cu](NO₃)₂ and [C₁₀H₁₀S₄N₂Ni](NO₃)₂ were carried out and the rate constants k_{(DNA-complex)} were calculated. The results indicate that DNA reacts with the metal complex in two steps. DNA first undergoes structural degradation and is then completely hydrolysed as indicated by spectral changes consistent with earlier results. The asymmetric N₂S₂ macrocyclic metal complexes show a strong propensity for DNA inhibition and can be used as an intercalating binding model.     

Rheological Measurements in Titania Gels Synthesized from Reverse Micelles

Abstract

TiO₂ sol and gel systems have been synthesized by hydrolysis of titanium butoxide in microemulsions W/O. Different systems compositions were prepared at constant W _o = [H₂O]/[AOT] and changing R = [H₂O]/[Ti(BuO)₄]. Experimental measurements show a progressive increase of the viscosity with time, characteristic of a sol-gel transition. The rheology of the transition was studied by following the behavior of viscoelastic parameters (G′, G″ and η?) as a function of time at different frequencies.

The possibility to apply standard percolation theory was discussed. The application of two alternative growth models-either “fractal growth model” or “nearly linear growth model”-has been analysed.     

Palladium acetate assisted synthesis of five-membered N-polyheterocycles

Abstract

The metal-assisted synthesis of heterocyclic compounds is known to be one of the extremely developing as well as significant concepts of organic chemistry. Because of their expensive, complex working of the instrument and difficult procedures, the methodologies used earlier for the heterocycle synthesis were less amicable to the researchers. The Pd(OAc)₂-mediated cyclic reactions have been recognized to be very effective for both the stereoselective as well as regioselective formation of the 5-membered N-bearing heterocyclic compounds. The different uses of palladium acetate, as a catalyst in the formation of 5-membered N-containing polyheterocycles, are covered in this review article.     

An orthorhombic polymorph of a cyclization product of perindopril

Low‐temperature X‐ray diffraction experiments were employed to investigate the crystal structures of an orthorhombic polymorph of the intramolecular cyclization product of perindopril, a popular angiotensive‐converting enzyme (ACE) inhibitor, namely ethyl (2S)‐2‐[(3S,5aS,9aS,10aS)‐3‐methyl‐1,4‐dioxo‐5a,6,7,8,9,9a,10,10a‐octahydro‐3H‐pyrazino[1,2‐a]indol‐2‐yl]pentanoate, C₁₉H₃₀N₂O₄, (Io), and its tetragonal equivalent, (It), which was previously reported at ambient temperature [Bojarska et al. (2013). J. Chil. Chem. Soc. 58 , 1415–1417]. Polymorph (Io) crystallizes in the orthorhombic space group P2₁2₁2₁ with two molecules in the asymmetric unit, while tetragonal form (It) crystallizes in the space group P4₁2₁2 with one molecule in the asymmetric unit. The geometric parameters of (Io) are very similar to those of (It). The six‐membered rings in both polymorphs adopt a slightly deformed chair conformation and the piperazinedione rings are in a boat conformation. However, the proline rings adopt an envelope conformation in (Io), while in (It) the ring exists in a slightly deformed half‐chair conformation. The most significant difference between the two structures is the orientation of the ethyl pentanoate chain. Molecules associate in pairs in a head‐to‐tail manner forming infinite columns. In (Io), molecules are related by a twofold screw axis forming identical columns, while in (It), molecules in successive neighbouring columns are related by alternating twofold screw axes and fourfold screw axes. In both cases, the crystal packing is stabilized by weak intermolecular C—H...O interactions only.     

The Synthesis,Characterization and Conductance Studies of New Cu(II), Ni(Ii) And Zn(II) Complexes with the Schiff Base Derived from 1,2-Bis-(o-Aminophenoxy)Ethane and Salicylaldehyde

Cu(II), Ni(II) and Zn(II) complexes with the Schiff base derived from 1,2-bis-(o-aminophenoxy)ethane with salicylaldehyde have been prepared. The complexes have been characterized by elemental analysis, magnetic measurements, ¹H NMR, ¹³C NMR, UV, visible and IR spectra as well as conductance measurements. The ligand is coordinated to the central metal as a tetradentate ONNO ligand. The four bonding sites are the central azomethine nitrogen and aldehydic OH groups. The ligand was used for complexation studies. Stability constants were measured by a conductometric method. Furthermore, the stability constants for complexation between ZnCl₂ and Cu(NO₃)₂ salts and N,N′-bis(salicylidene)-1,2-bis-(o-aminophenoxy)ethane (H₂L) in 80% dioxane/water and pure methanol were determined from conductance measurements. The magnitudes of these ion association constants are related to the nature of the solvation of the cation and the complexed cation. The mobilities of the complexes are also dependent, in part, upon solvation effects.     

X-ray structures of iron(III) and cobalt(III) complexes containing 2-<Emphasis Type="Italic">S</Emphasis>-methyl-6-methyl-4-formylpyrimidine-<Emphasis Type="Italic">N</Emphasis>(4)-ethylthiosemicarbazone

Iron(III) and cobalt(III) complexes of types [Fe(LEt)₂]ClO₄·3/2C₆H₆ (1) and [Co(LEt)₂]ClO₄·2CH₂Cl₂ (2) with a new pyrimidine-derived thiosemicarbazone ligand, 2-S-methyl-6-methyl-4-formylpyrimidine-N(4)-ethylt-hiosemicarbazone (HLEt), having N, N, S donor centers have been synthesized and characterized by X-ray crystallography. The structural study shows distorted octahedral geometry for both 1 and 2 with MN₄S₂ chromophores. The space group of 1 is C2/c (monoclinic) and that of 2 is P2₁2₁2₁ (orthorhombic). The electrochemical electron transfer study in MeCN solutions shows a one-electron reductive response presumably due to a metal(III)–metal(II) couple.     

Features of the reactions of β-aryl(heteryl)-α-nitroacrylates with N,N-, N,O-, and N,S-binucleophiles

The reactions of ??-aryl(heteryl)-??-nitroacrylates with N,N-, N,O-, and N,S-binucleophiles proceed regiospecifically through the initial formation of the Ad_N products, among which only the product from o-aminothiophenol was isolated. The conditions of converting the S-adducts into 2-aryl(heteryl)benzothiazole were found. The N-adducts formed in the reaction with hydrazine, o-phenylenediamine, and o-aminophenol undergo immediately the spontaneous transformation into the linear (azine, azomethine) or heterocyclic (benzimidazole) structures.