Copper and palladium complexes with substituted pyrimidine-2-thiones and 2-thiouracils: syntheses,spectral characterization,and X-ray crystallographic study

Copper(I) and palladium(II) complexes containing 5-acetyl-6-methyl-1,2,3,4-tetrahydropyrimidine-2-thione (L¹), ethyl 4,6-dimethyl-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate (L²), cis-5-acetyl-6-ethyl-5,6-dihydro-2-thiouracil (L³), and 5,6-dihydro-2-thiouracil (L⁴) have been synthesized. All complexes were characterized by elemental analysis, IR, ¹H, and ¹³C NMR spectroscopy. To assign bands in the IR spectra of L¹ and L² and complexes with Cu(I) and Pd(II), deuterium substitution of movable protons at N-atoms was used. The crystal structures of two compounds, [Cu(L²)₂Cl] and [Pd(L⁴)₂Cl₂], were determined by X-ray single-crystal and powder diffraction, respectively. In [Cu(L²)₂Cl], copper has a rare coordination number of three and triangular surrounding of two neutral L² molecules, coordinated through sulfurs, and chloride. In [Pd(L⁴)₂Cl₂], palladium has a standard square-planar geometry, formed by two uracil molecules and two chlorides. A new method for the synthesis of 5,6-dihydro-2-thiouracil, starting from β-aminopropionic acid, was suggested.     

Synthesis of 5-(4,6-dimethyl-2-pyrimidinyl)-1,3,4-oxadiazole-2-thione and its alkylation,aminomethylation, and acylation

The reaction of the hydrazide of 4,6-dimethyl-2-pyrimidinecarboxylic acid with potassium ethylxnthate gave 5-(4,6-dimethyl-2-pyrimidinyl)-1,3,4-oxadiazole-2-thione. The alkylation of this product in an alkaline medium proceeds at the sulfur atom, while the aminomethylation and acylation proceed at the nitrogen atom. The major criterion for the structure of the S- and N-derivatives is the chemical shift of C₍₂₎ in the 1,3,4-oxadiazole ring in the ¹³C NMR spectra.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 700–705, May, 1993.     

Synthesis of 4-amino-5-(4,6-diphenyl-2-pyrimidinyl)-3,4-dihydro-2H-1,2,4-triazole-3-thione and its reactions with C-electrophiles

4-Amino-5-(4,6-diphenyl-2-pyrimidinyl)-3,4-dihydro-2H-1,2,4-trazole-3-thione is formed from the reaction of 4,6-diphenylpyrimidinecarboxylic acid or its ethyl ester with thiocarbonyl hydrazide. Alkylation of the product leads to S-alkyl derivaties or 6-substituted 3-(4,6-diphenyl-2-pyriimidinyl)-7H-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazine. Acetylation of 4-amino-5-(4,6-diphenyl-2-pyrimidinyl)-3,4-dihydro-2H-1,2,4-triazole-3-thione gave under different conditions monoacetyl-, diacetyl, and triacetyl derivatives at the amino group and the N₍₂₎ atom, whereas benzoylation gave a benzoyl group at the amino group and 3-(4,6-diphenyl-2-pyrimidinyl)-6-phenyl-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazole. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, 1088–1094, July, 2007.     

Zinc(II), cadmium(II) and mercury(II) complexes of neutral and deprotonated 4,6-dimethylpyrimidine-2(1H)-thione

The following zinc(II), cadmium(II) and mercury(II) complexes of neutral and deprotonated 4,6-dimethylpyrimidine-2(1H)-thione (HL) have been prepared and studied by conductometric and i.r. methods: [M(HL)₂X₂] (M  Zn, Cd, Hg; X  Cl, Br, I), [M(HL)₃]A₂·2H₂O (M  Zn, Cd; A  ClO₄ and M  Hg; A  ClO₄, BF₄, CF₃COO), M(HL)₂(CF₃COO)₂(M  Zn, Cd), ZnL₂·HL and ML₂ (M  Cd, Hg). In most of the complexes the ligand is N,S-bonded to the metal ion, the metal-nitrogen bond being stronger than the metal-sulphur one; only in the cadmium chloride and bromide complexes the ligand seems to be only N-bonded to the metal, with bridging halide ions. Most of the complexes seem to have a distorted six-coordination while to the neutral HgL₂ complex a tetrahedral [N,S]₂ coordination may be assigned.     

Luminescent silver nitrate complexes of bis[2-(diphenylphosphano)phenyl]ether (DPEphos): Crystal structure of [Ag(DPEphos)(py2SH)2]NO3

Heteroleptic silver(I) nitrate complexes containing the bis[2-(diphenylphosphano)phenyl]ether (DPEphos) ligand and the heterocyclic thioamides pyridine-2(1H)-thione (py2SH), pyrimidine-2(1H)-thione (pymtH), 4,6-dimethylpyrimidine-2(1H)-thione (dmpymtH), 1,4,5,6-tetrahydropyrimidine-2-thione (thpymtH) or 1,3-imidazolidine-2-thione (imtH₂) have been synthesized and characterized by IR and UV-Vis spectroscopy, elemental analyses and melting point determinations. The complexes can be obtained by the addition of the thioamide ligand to an AgNO₃-diphosphane adduct in dichloromethane/ethanol solution. The molecular structure of [Ag(DPEphos)(py2SH)₂]NO₃ complex has been established by single-crystal X-ray diffraction. The structure features a tetrahedral silver(I) center with two phosphorus atoms from the chelating diphos ligand, and the exocyclic sulfur atom of two heterocyclic thioamide units. Intense blue-green emission is observed in the region 470-483 nm for all the complexes in the solid state and in solution at ambient temperature.     

Three- and four-coordinate copper(I) halide complexes of 2-(diphenylphosphano)benzaldehyde: Dimerization induced by thione-S ligation

Reactions of copper(I) halides with 2-(diphenylphosphano)benzaldehyde (PCHO) in 1:2 molar ratio afforded mononuclear complexes of the type [CuX(PCHO)₂], whereas treatment of these compounds with equimolar amounts of pyridine-2-thione or pyrimidine-2-thione gave rise to the formation of mixed-ligand dimers of the formula [CuX(PCHO)(thione)]₂. The molecular structures of [CuCl(PCHO)₂], [CuBr(PCHO)₂] and [CuCl(PCHO)(pymtH)]₂ have been established by single-crystal X-ray diffraction. The two homoleptic complexes feature a trigonal copper(I) centre with the phosphane acting as a monodentate ligand via the P atom. In the structure of the dimeric mixed-ligand complex each of the two metal centres exhibit a distorted tetrahedral environment with the thione-S atoms acting in a doubly bridging mode.     

The dramatic effect of thiophenol on the reaction pathway of ethyl 4-chloromethyl-6-methyl-2-oxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate with thiophenolates: ring expansion versus nucleophilic substitution

Ethyl 4-methyl-2-oxo-7-phenylthio-2,3,6,7-tetrahydro-1H-1,3-diazepine-5-carboxylate and/or ethyl 6-methyl-2-oxo-4-(phenylthiomethyl)-1,2,3,4-tetrahydropyrimidine-5-carboxylate were obtained in the reaction of ethyl 4-chloromethyl-6-methyl-2-oxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate with PhSNa or PhSK with or without PhSH, depending on the reagent ratio, reaction time, or temperature, as a result of ring expansion and/or nucleophilic substitution. The reaction pathway was affected strongly by the basicity-nucleophilicity of the reaction media. The results obtained were confirmed by reactions of 4-mesyloxymethyl-6-methyl-5-tosyltetrahydropyrimidin-2-one with PhSNa/PhSH and ethyl 4-chloromethyl-6-methyl-2-oxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate with NaCN/HCN or NaCH(COOEt)₂/CH₂(COOEt)₂.     

Reaction of ethyl 4-aryl-6-bromomethyl-2-oxo-1,2,3,4-tetrahydropyrimidine-5-carboxylates with N-methylmorpholinium 3-cyano-1,4-dihydro- and 3-cyano-1,4,5,6-tetrahydropyridine-2-thiolates

Alkylation of N-methylmorpholinium 4-Ar¹-3-cyano-6-oxo-1,4,5,6-tetrahydropyridine-2-thiolates using ethyl 4-Ar-6-bromomethyl-2-oxo-1,2,3,4-tetrahydropyrimidine-5-carboxylates (10 % KOH, DMF) gives mixtures of diastereomers of ethyl 4-Ar-6-[(4-Ar¹-3-cyano-1,4,5,6-tetrahydropyridin-2-ylthio)methyl]-1-methyl-2-oxo-1,2,3,4-tetrahydropyrimidine-5-carboxylates in overall 30-58 % yield. Under these conditions the N-methylmorpholinium 4-Ar1-5-(N-Ar²-carbamoyl)-3-cyano-6-methyl-1,4-dihydropyridine-2-thiolates undergo aromatization of the dihydropyridine ring to give ethyl 4-Ar-6-[4-Ar¹-5-(N-Ar²-carbamoyl)-3-cyano-6-methylpyridin-2-ylthio)methyl]-2-oxo-1,2,3,4-tetrahydropyrimidine-5-carboxylates (37-51 %). In the absence of KOH, only the substituted pyridine-2(1 H)-thione is formed as a product of oxidation of the dihydropyridine ring in the starting substrate. Some of the alkylation products obtained possess weak or moderate antibacterial activity towards the specific strains of Escherichia coli and Bacillus subtilis but are inactive towards Candida albicans and Staphylococcus aureus.     

Zinc(II), cadmium(II) and mercury(II) complexes of 4-amino-benzophenone

The following zinc(II), cadmium(II) and mercury(II) complexes of 4-amino-benzophenone (L) have been prepared and studied by i.r. and electronic spectra: 2MX₂·3L (M=Zn, Cd; X=Cl, Br), 3ZnI₂·2L, 2ZnI₂·L, MX₂·L (M=Cd, X=I; M=Hg, X=Cl, Br). Infrared spectra show that in the zinc complexes the ligand is principally bonded through the aminic nitrogen atom and in the cadmium and mercury(II) complexes through the carboxylic oxygen atom.     

Zinc (II), cadmium (II) and mercury (II) complexes of 2-methyl-5-mercapto-1,3,4-thiadiazole

The following zinc (II), cadmium (II) and mercury (II) complexes of 2-methyl-5-mercapto-1,3,4-thiadiazole (HL) have been prepared and studied by conductometric, i.r. and Raman methods: MX₂·2HL (M = Zn, X = Cl, Br, I; M = Cd, Hg, X = Cl, Br), Ml₂ (M = Zn, Cd), CdL₂·HL·NH₃, HgL·NO₃, HgL₂·HL, HgL₂·NH₃. In the MX₂·2HL complexes the ligand is bonded to the metal through its thiocarbonylic sulphur atom with terminal MX bonds for the zinc and mercury and with bridging halide ions for cadmium complexes. The polymeric ZnL₂ and CdL₂ complexes have presumably an S₂N₂- and an S₂N₄-coordination, respectively. For the CdL₂·HL·NH₃ and HgL₂·HL complexes an S₃N₃-coordination may be proposed. In the HgL·NO₃ complex the nitrate ion is coordinated presumably with an S, O, N₂ coordination.     

A novel thio­cyanate‐bridged dinuclear cadmium(II) complex: di‐μ‐thio­cyanato‐bis­((methanol){4‐nitro‐2‐[2‐(dimethyl­amino)ethyl­imino­meth­yl]phenolato}cadmium(II))

The title complex, [Cd₂(C₁₁H₁₄N₃O₃)₂(NCS)₂(CH₄O)₂], is an inter­esting thio­cyanate‐bridged dinuclear cadmium(II) compound. It is located on a crystallographic inversion center. The Cd^II atom is six‐coordinated in an octa­hedral configuration by one O and two N atoms of one Schiff base ligand and by the terminal N atom of a bridging thio­cyanate ligand, defining the basal plane, and by the terminal S atom of another bridging thio­cyanate ligand and by the O atom of a coordi­nated methanol mol­ecule, occupying the axial positions. The mol­ecules are linked through inter­molecular O—H⋯O hydrogen bonds, forming chains running along the b axis.     

Synthesis and reactions of “biginelli-compounds”. Part I

Various reactions of 2-oxo(or thioxo)-1,2,3,4-tetrahydropyrimidine-5-carboxylic acid derivatives (Biginelli-compounds) were investigated. The site of methylation and acylation on 6-methyl-4-phenyl-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-carboxylic acid ethyl ester 1a and its 2-oxo derivative 9a was studied. The synthesis of pyrimido[2,3-b]thiazines and thiazolo[3,2-a]pyrimidines was accomplished by condensation of 1a with 1,3-and 1,2-dielectrophiles. A Dimroth-like rearrangement yielding 6H-1,3-thiazines can be observed when 1a was treated with dimethylformamide and phosphorus oxychloride. The formation of indeno[1,2-d]pyrimidines can be achieved by intramolecular Friedl-Crafts acylation of 9a and 13 , respectively. Finally a route for the preparation of 4,6-disubstituted-pyrimidine-5-carbonitriles is presented, starting with Biginelli-compound 25 .     

Zinc(II), cadmium(II) and mercury(II) complexes of 4,6-dimethyl-pyrimidine-2(1H)-one

The following zinc(II), cadmium(II) and mercury(II) complexes of 4,6-dimethylpyrimidine-2(1H)-one (L) have been prepared and investigated by conductometric,IR and Raman methods: MX₂L₂ (M = Zn, X = Cl, Br(CHCl₃, I(CHCl₃, CF₃COO; M = Cd, X = Cl, Br CF₃COO; M = Hg, X = Cl, CF₃COO), Cd₂I₄L₃, Hg₃X₆L₂ (X = Cl, Br), Hg₃X₆L₄(X = Br, I), MX₂L₄·6H₂O (M = Zn, Cd, X = CIO₄, BF₄; M = Hg, X = CIO₄. The ligand is principally bonded through the unprotonated nitrogen atom and in some complexes also through the carbonylic oxygen atom. The zinc halide complexes are tetrahedrally coordinated, the trifluoroacetate ion is coordinated as a monodentate ligand.     

Self-Assembly of Dithiolene-based Coordination Polymers of Mercury(II): Dithioether versus Thiocarbonyl Bonding

The reactions of 4,5-bis(methylthio)-1,3-dithiole-2-thione (L) with mercury(II) halides allowed the isolation and structural characterization of three novel coordination polymers, [HgX₂L]_n (X = I, 1; X = Br, 2; X = Cl, 3). In all cases, the complexation of L on HgX₂ occurs via the thiocarbonyl function. The strength of this Hg–S bond decreases from X = I to X = Cl, as indicated by the increasing Hg–S bond distances (2.583(4) 1; 2.668(4) 2; 2.815(5) ? 3). The 1D polymeric structures result from bridging halide interactions and a combination of π–π and S···S interactions between the sulfur rich ligands. The coordination around the Hg center is distorted tetrahedral in 1, whereas the geometry around the mercury in 3 is better described as distorted square pyramidal. In addition, weak interchain interactions are observed in the crystalline state. The preference of HgI₂ for thiocarbonyl bonding instead of a chelating dithioether bonding was also studied by means of ab initio calculations.     

Mercury-bridged,nitrosyl substituted,triruthenium carbonyl clusters: Synthesis and x-ray crystal structure of [Ru3(NO)(CO)10]2Hg

The neutral mixed-metal cluster [Ru₃(NO)(CO)₁₀]₂Hg has been prepared by the reaction of the [Ru₃(NO)(CO)₁₀], with HgCl₂. An X-ray crystal structure shows that the mercury atom links two Ru₃ triangular units by bridging an RuRu edge of each unit. The dihedral angle between the two Ru₂Hg triangles is 27.6°. In each Ru₃ triangle a nitrosyl ligand bridges the same RuRu edge as the bridging Hg atom while the ten carbonyl groups are all terminal.     

New thiourea organocatalysts and their application for the synthesis of 5-(1H-indol-3-yl)methyl-2,2-dimethyl-1,3-dioxane-4,6-diones a source of chiral 3-indoylmethyl ketenes

The stereoselective properties of modified thiourea organocatalysts were tested in the Friedel–Crafts alkylation of indole with 5-arylidene-2,2-dimethyl-1,3-dioxane-4,6-diones, which produces chiral 5-((1H-indol-3-yl)(aryl)methyl)-2,2-dimethyl-1,3-dioxane-4,6-diones. Based on a tentative reaction mechanism for ((S)-N-benzyl-2-(3-(3,5-bis(trifluoromethyl)phenyl)thioureido)-N,3,3-trimethylbutanamide organocatalysts, modifications were applied in four selected regions. Systematic structure-stereoselectivity relationship study allowed designing the best efficient organocatalyst for the investigated Friedel–Crafts alkylation of indole with 5-arylidene-2,2-dimethyl-1,3-dioxane-4,6-diones.     

The transformation using the soft NO⊕-species

The reaction of NaNO₂ in acidic solution with thiocarbonyl compounds has been studied. Secondary- and tertiary thioamides, 1-benzyl-hexahydro-2H-azepine-2-thione, 5-ethyl-5-phenyl thiobarbituric acid, certain thiourea derivatives, 2H-1-benzopyran-2-thione, O,O-diphenyl-thiocarbonic ester, O,S-diphenyl-dithiocarbonic ester, N,N-dimethyl-S-phenyl-dithiocarbamatic ester, N-ethyl-N-phenyl-O-ethyl-thiocarbamatic ester are all converted into the corresponding carbonyl-analogues. 4,4′-Bis (dimethylamino)-thiobenzophenone (Michler's thioketone) gives 3-nitro-4,4′-bis (dimethylamino)-benzophenone at room temperature. At (?10 °C)-(?5 °C) the expected oxo compound is obtained as the main product together with 4-(N-nitroso-methylamino)-4′-(dimethylamino)-benzophenone.     

Self-Assembly of Dithiolene-based Coordination Polymers of Mercury(II): Dithioether versus Thiocarbonyl Bonding

Summary. The reactions of 4,5-bis(methylthio)-1,3-dithiole-2-thione (L) with mercury(II) halides allowed the isolation and structural characterization of three novel coordination polymers, [HgX₂L]_n (X = I, 1; X = Br, 2; X = Cl, 3). In all cases, the complexation of L on HgX₂ occurs via the thiocarbonyl function. The strength of this Hg–S bond decreases from X = I to X = Cl, as indicated by the increasing Hg–S bond distances (2.583(4) 1; 2.668(4) 2; 2.815(5) ? 3). The 1D polymeric structures result from bridging halide interactions and a combination of π–π and S···S interactions between the sulfur rich ligands. The coordination around the Hg center is distorted tetrahedral in 1, whereas the geometry around the mercury in 3 is better described as distorted square pyramidal. In addition, weak interchain interactions are observed in the crystalline state. The preference of HgI₂ for thiocarbonyl bonding instead of a chelating dithioether bonding was also studied by means of ab initio calculations.     

The first synthesis of 8-aza-2-polyfluoroalkylchromones

The condensation of 3-acetyl-4,6-dimethyl-2-pyridone with R_FCO₂Et in the presence of LiH in dioxane affords corresponding R_F-containing β-diketones, whose dehydration under the action of conc. H₂SO₄ gives 8-aza-5,7-dimethyl-2-polyfluoroalkylchromones.     

The crystal and molecular structure of hexachloro-tris(μ-allylthiourea) ditungsten (III) monohydrate {W2 [SC(NH2)NHCH2CHCH2]3Cl6} · H2O

A new kind of binuclear tungsten complex {W₂[SC(NH₂)NHCH₂CHCH₂]₃Cl₆} H₂O was synthesized by mixing a concentrated hydrochloric acid solution of [W₂Cl]³⁻ with allylthiourea and investigated by X-ray structural analysis. The crystal is monoclinic, belonging to the space group P2₁, with the following parameters: a = 8.496(1)Å, b = 18.760(2)Å, c = 8.591(1)Å, β = 91.36(1)' and Z = 2 with D_c = 2.297 g·cm⁻³. The structure was solved by heavy atom method and difference Fourier synthesis and refined by full-matrix least-squares technique to a final R factor of 0.038 for 2812 independent reflections with I ≥ 3σ(I). The result shows that in the structure each W atom forms an octahedral coordination with three Cl atoms and three bridging S atoms of the allylthiourea molecules. These two octahedra share a common face to form a binuclear complex with a very much shorter W-W bond distance (2.443(1)Å), indicating a strong interaction between the two W atoms. Judging from the orientation of the thiourea ligand groups with respect to the W-S bonds, the thiourea S atoms are coordinated to the two W atoms in different manners. It is noted that one of the two W atoms is located at the point of intersection of the three thiourea planes, while the other W atom is located quite apart from these thiourea planes with three W-S bonds nearly perpendicular to each of them respectively.