Square-Planar Nickel(II) O,O′-Dialkyldithiophosphato Complexes with Triphenylphosphine of the Type [NiX(S2P{OR}2)(PPh3)] (X = Cl,Br, I and NCS)

A series of new [NiX(S₂P{O-c-Hex}₂)(PPh₃)](X = Cl^–, Br^–, I^– and NCS^–)(1)–(4) and [Ni(NCS)(S₂P{OR}₂)(PPh₃)][R =n-Pr (5), i-Pr (6)] complexes has been synthesized and characterized by elemental analyses, f.i.r., i.r., u.v.–vis., ¹H-, ¹³C{¹H}- and ³¹P{¹H}-n.m.r. spectra, magnetochemical and conductivity measurements. A single crystal X-ray analysis of [Ni(NCS)(S₂P{O-n-Pr}₂)(PPh₃)](5) reveals the molecular structure of the complex and confirms a square-planar geometry around the central atom of nickel with the NCS anion coordinated via the nitrogen atom.     

Cobalt(II) complexes of the 2-aminopicolineN-oxides and 2-amino-4, 6-lutidineN-oxide

Summary Cobalt(II) complexes of the four 2-aminopicolineN-oxides and 2-amino-4, 6-lutidineN-oxide were prepared from Co(BF₄)₂ and CoCl₂, and characterized by partial elemental analyses, magnetic moments, molar conductivities, thermal analyses, and by plasma desorption mass, i.r., electronic, and e.s.r. spectroscopy. The compounds derived from CoCl₂ are 4-coordinate, tetrahedral, molecular solids with CoO₂Cl₂ chromophores. Dq values range from 332 to 382 cm^–1 and those of B from 758 to 813 cm^–1 for the five solids. Three of the compounds prepared from Co(BF₄)₂ are octahedral with the following stoichiometry: [CoL₆](BF₄)₂ where L=2-amino-4-picolineN-oxide and [CoL₅(H₂O)] (BF₄)₂ where L is either 2-amino-3-or 2-amino-5-picolineN-oxide. Both 2-amino-6-picolineN-oxide and 2-amino-4, 6-lutidineN-oxide gave square planar [CoL ₄ ²⁺ ] complex ions. While numerous square planar cobalt(II) centers are known, those described here are probably the first examples with monodentate ligands and a CoO₄ center. They have weak e.s.r. spectra, magnetic moments between 2 and 3 BM and characteristic d-d spectra.     

Synthesis,crystal structure and nonlinear optical properties of a new cluster complex: WCu3OS3(PPh3)3{S2P(OPr i 2)2}

A new cluster compound WCu₃OS₃(PPh₃)₃{S₂P(OPr ⁱ ₂)₂}, prepared by reacting (NH₄)₂WOS₃ with PPh₃ and [CuS₂P(OPr ⁱ ₂)₂], was characterized by elemental analysis, i.r. spectroscopy and X-ray crystallography. The structure consists of a tetra-nuclear distorted tetragonal core with one W atom coordinated by one O atom, three ₃-S and three Cu atoms. Anisotropic refinement for all nonhydrogen atoms yielded the value R = 0.0718. Investigation of third-order optical nonlinearity using the Z-scan technique shows that the cluster compound exhibits good nonlinear properties with ₂ values of 1.23 × 10^–10 m w^–1 and n ₂ values of –9.3 × 10^–18 m² w^–1 respectively.     

Synthesis of silver(III) aminomethylpyridine complexes from silver nitrate and aminomethylpyridines

Ag^III complexes have been synthesized with pyridine derivatives, i.e., 2-amino-4-methylpyridine and 2-amino-6-methylpyridine, by the oxidation of AgNO₃ with ammonium peroxydisulfate in the presence of the ligands in aqueous solution. These new complexes were characterized by i.r., ¹H-n.m.r., u.v.–vis., microanalysis, magnetic susceptibility, voltammetry and thermal gravimetry.     

Thermoanalytical investigations of niobium(V) chloride aryloxides

Niobium(V) chloride aryloxides [NbCl₃(OAr)₂] and [NbCl₂(OAr)₃] (Oar = —OC₆H₄Bu ^t -4 and —OC₆H₄OMe-4) have been prepared by reacting NbCl₅ with two and three equivalents of the respective phenol in CCl₄. The complexes have been characterized by elemental analysis, molecular weight determination, i.r., ¹H-n.m.r., u.v.–vis. and MS techniques. Thermal behaviour (t.g.–d.t.) of the complexes has also been studied and decomposition schemes proposed. The kinetic and thermodynamic parameters namely, the activation energy 'E ^*', the frequency factor 'A', entropy of activation 'S' and specific rate constant 'kr' etc. have been calculated employing the Coats–Redfern equation. The non-isothermal t.g. data has also been utilized to determine the most probable mechanism and corresponding activation energy for the decomposition of niobium(V) complexes by testing seven different theoretically possible decomposition mechanisms.     

Synthesis and Stereochemistry of (1S,3S,4S,7R11R)-3-(4-Nitrophenyl)-11-aza-2,6-dioxatricyclo[5,3,1,04,11]undecane

The reaction of (1S,2S)-2-amino-1-(4-nitrophenyl)-1,3-propanediol with glutaraldehyde has been studied. It has been established on the basis of AM1 and PM3 calculations and ¹H NMR spectra recorded in the presence of the shift reagent Eu(fod)₃ that (1S,3S,4S,7R,11R)-3-(4-nitrophenyl)-11-aza-2,6-dioxatricyclo[5,3,1,0^4,11]undecane is formed as the result of the reaction.     

On the linear mixed valence compounds obtained by partial oxidation ofcis-diamminedichloroplatinum(II)

Summary The partial oxidation products ofcis-[Pt(NH₃)₂Cl₂] (Cisplatin) by (NH₄)₂S₂O₈ and by K₂PtCl₆, as well as the recrystallization of the former product in various solutions (HClO₄, NaClO₄, NaBF₄, NaHSO₄, H₂SO₄) have been re-examined. Contrary to the conclusions of previous works, the general formulation of these compounds iscis-[Pt²⁺(NH₃)₂Cl₂]X_x·yH₂O ( = 0.3–0.4, X = SO ₄ ^2– , PtCl ₄ ^2– , ClO ₄ ^2– , BF ₄ ^2– , HSO ₄ ^2– , ..., 0y 1). These materials are all linear chain Pt—Pt compounds belonging to the class III of Robin-Day compounds with Pt—Pt distances in the range 3.00–3.06 Å. The oxidation of Cisplatin by persulphate gives two sulphate compounds of the same formulation (x = 0.2), which differ in aspect, metallic character and spectral properties. Structural information was obtained from polarized micro-Raman spectra of a needle-like sample of the perchlorate and from X-ray powder diffraction spectra. The cell of the perchlorate was orthorhombic while the two sulphate forms had a monoclinic cell with slightly different parameters. Expansion of the Cisplatin interchain distance occurred only along one crystallographic direction. The two sulphate forms differed in the degree of order along this direction. An approximate structure is proposed and discussed in relation to the Cisplatin precursor.     

Rhenium octahedral clusters: the systems Re-S-Br and M-Re-S-Br (M = Na, K, RB, Cs)

The quaternary systems M-Re-S-Br (M = Na, K, Rb, Cs) have been investigated in the domains of composition which are expected to lead to the formation of Re₆ octahedral cluster based compounds. A number of compounds have been obtained. They include the ternaries Re₆S_4+xBr_10−2x (integer x = 0–4) among them crystal data are reported for Re₆S₄Br₁₀ and Re₆S₅Br₈. Various quaternaries are also presented. Most of them are built from the ¦Re₆S_4+nBr_10−n¦ⁿ⁻ anionic units (n = 1–4) stacked in various compounds and solid solutions, the structure of which strongly depends on the number and size of counter cations.     

Complexes of 1,8-bis(2-pyridyl)-3,6-dithiaoctane with cobalt(II) halides

Summary Several cobalt(II) halide complexes derived from 1,8-bis(2-pyridyl)-3,6-dithiaoctane (bpdto) are described. Chemical analysis suggests their formulae to be: Co(bpdto)X₂ (X=Cl^–, Br^–, or I^–). Electrolytic conductivities in acetonitrile, magnetic moments at different temperatures, solid state i.r. and u.v.-visible spectra support a tetrahedral stereochemistry around the cobalt(II). The ligand is bidentate andN-bonded in all cases.This work was presented in the Fifth Annual Meeting of the Portuguese Chemical Society, Porto (Portugal), March 1982.     

Spectrophotometric determination of vanadium(V) with p-Sulphobenzeneazo-4-(2-amino-3-hydroxypyridine)

Summary p-Sulphobenzeneazo-4-(2-amino-3-hydroxypyridine) reacts with vanadium to form an orange-red coloured complex having maximum absorbance at 530 nm. The reaction is slow at room temperature, it is complete at 40–45° C in 5 min. The effects of temperature, time, pH, reagent concentration, and other variables have been studied. The system obeys Beer's law over the concentration range of 1–12g vanadium(V) ml^–1. The molar absorptivity is 5.453 x 10³l·mole^–1·cm^–1. The metal:ligand ratio of 12 was confirmed by Job's continuous variation and mole ratio methods.

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Spektrophotometrische Bestimmung von Vanadin(V) mit p-Sulfobenzolazo-4-(2-amino-3-hydroxypyridin)

Zusammenfassung p-Sulfobenzolazo-4-(2-amino-3-hydroxypyridin) bildet mit Vanadin(V) einen orange-roten Komplex, dessen Absorptionsmaximum bei 530 nm liegt. Bei Zimmertemperatur verläuft die Reaktion langsam, bei 40–45° ist sie in 5 min vollständig. Der Einfluß von Temperatur, Zeit, pH, Reagenskonzentration und anderer variabler Faktoren wurde untersucht. Im Konzentrationsbereich 1–12g Vanadin/ml entspricht die Reaktion dem Beer-schen Gesetz. Die molare Absorptivität ist 5,453 x 10³l·mol^–1·cm^–1. Das Verhältnis Metall:Ligand wurde nach Job bestimmt und beträgt 12.

     

Kinetics and mechanism of base hydrolysis oftrans-bis(Hmalonato)bis(ethylenediamine)cobalt(III) ion

Summary The kinetics of the first step of base hydrolysis oftrans-bis(Hmalonato)bis(ethylenediamine)cobalt(III) [malH^–=HO₂CCH₂CO ₂ ^– ] has been investigated in the 15–35° C range, I=0.3 mol dm^–3 (NaClO₄) and [OH^–]=0.015–0.29 mol dm^–3. The rate law is given by –d In[complex]_T/dt=k₁[OH^–] and at 30° C, k₁=8.5×10^–3 dm³ mol^–1s^–1, H=117.0±7.0 kJ mol^–1 and S=99.0±24.0 JK^–1mol^–1. The activation parameters data are consistent with the SN₁ cb mechanism.     

Synthesis,characterization and biological studies of 2-(3,5-dimethylpyrazol-1-yl)benzothiazole complexes of cobalt(II), nickel(II) and copper(II)

Summary Thirteen new complexes, MLX·nH₂O and ML₂(ClO₄)₂· nH₂O [M = Co, Ni, Cu; X = Cl^–, Br^–, NO _f3 ^p– , 1/2SO _f4 ^p2– ; n = 1 or 2; and L = 2-(3,5-dimethylpyrazol-1-yl)benzothiazole], have been synthesized, and characterized by elemental analysis, conductivity measurements, magnetic moments, thermal studies and electronic, i.r. and e.p.r. spectral studies. On the basis of available data probable structures have been proposed. In a few cases the antibacterial and antifungal activities increase on complexation of the ligand with metals.     

Compounds of nickel(II) with 5SR,7RS,12SR,14SR-5,12-dimethyl-7,14-diphenyl-1,4,8,11-tetraazacyclotetradecane, rmL: The structures of [Ni(rmL)](ClO4)2 · 0.5H2O and cis-[Ni(rmL)(acac)]ClO4

The imine functions of [Ni(mL¹)](ClO₄)₂ (mL¹ = meso-7RS,14SR-5,12-dimethyl-7,14-diphenyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene) are reduced by using NaBH₄ in acetonitrile/methanol to form the meso–meso and rac–meso isomeric cyclic tetramine complex cations [Ni(mmL²)]²⁺ and [Ni(rmL²)]²⁺ (mml² = 5RS,7RS,12SR,14SR- and rmL² = 5SR,7RS,12SR,14SR-5,12-dimethyl-7,14-diphenyl-1,4,8,11-tetraazacyclotetradecane) in ca. 8:1 proportions. [Ni(rmL²)]²⁺ is also prepared from rmL², formed in <1% yield by the reduction of mL¹ by NaBH₄ in ethanol. Square planar singlet ground state (S = 1) salts [Ni(rmL²)](ClO₄)₂ and [Ni(rmL²)][ZnCl₄] and triplet ground state (S = 3) trans-di-ligand octahedral compounds trans-[Ni(rmL²)X₂] ,μ-Y-trans-[Ni(rmL²)Y] and folded macrocycle compounds cis-[Ni(rmL²)(acac)]CIO₄ (acac⁻ = pentane-2,4-dionato), cis-[{Ni(rmL²)}₂(C₂O₄)](ClO₄)₂, cis-[Ni(rmL²)(H₂O)₂](ClO₄)₂ and cis-[Ni(rmL²)X₂], X⁻ = Cl⁻, Br⁻, are described. The S = 1 salt 1SR,4SR,5SR,7RS,8RS,11RS,12SR,14SR-[Ni(rmL²)](ClO₄)₂ · 0.5H₂O has a disordered structure with Ni(II) in square planar coordination by the nitrogen atoms of the macrocycle, in N-configuration III, with Ni–N_mean = 1.96(2) Å. The six-membered chelate rings both have chair conformations, with the phenyl substituents equatorially oriented and with the methyl substituents disordered over axial and equatorial orientations. The S = 3 compound cis-1SR,4SR,5SR,7RS,8SR,11SR,12SR,14SR-[Ni(rmL²)(acac)]ClO₄ has N-configuration V. The macrocycle is folded along N¹–Ni–N⁸, adjacent to the phenyl substituents {N1–Ni–N8 = 176.45(6), N4–Ni–N11 = 98.16(6)°}, with mean Ni–N = 2.09(2) Å and mean Ni–O = 2.121(5) Å. Both six-membered chelate rings have chair conformations with the methyl substituents equatorially oriented, while one has the phenyl substituent equatorially and the other has it axially oriented. The structures of the isomeric [M(rmL²)(acac)]ClO₄, [M(rrL²)(acac)]CIO₄ and [M(mmL²)(acac)]ClO₄ compounds are compared.     

Synergism in molybdenum iron sulphur cluster compounds. Synthetic,structural, magnetic,cyclic voltammetric evidence and the reaction of dicubane clusters containing [MoFe3S4] unit

Summary Dicubane cluster compounds (Et₄N)₄[Mo₂Fe₇S₈(SR)₁₂] (2A) (R=Ph,a;o-tolyl,b;m-tolyl,c;p-tolyl,d) were made by reaction of (Et₄N)₂[Fe₄(SR)₁₀] (1) with (Et₄N)₂MoS₄ in MeCN at room temperature. The structure,¹Hn.m.r.,⁵⁷Fe Mössbauer spectrum, magnetic susceptibility and cyclic voltammogram are described. (Et₄N)₃[Mo₂Fe₆S₈Cl₆(SR)₃] (3) (R=Ph,a;m-tolyl,b) was obtained from the reaction of (2Aa) or (2Ac) with acetyl chloride in MeCN. This is the first time that compound of structural type (2) is transformed into that of structural type (3) by chemical conversion. Compound (2Aa) crystallizes in the triclinic space group P with Z=1 and unit cell dimensionsa=12.775(4),b=13.076(3), andc=20.576(4) Å; the structure was refined to R=7.7% using 4031 unique data with I>3(I_o). Compound (2Ac) 2THF crystallizes in the monoclinic space group P2₁/n with Z=2 and unit cell dimensionsa=18.022(2),b=18.375(2) andc=22.254(3) Å; the structure was refined to R=6.4% using 5173 unique data with I>3(I_o). Compound (3b) crystallizes in the hexagonal space groupP6₃/m with Z=2 and unit cell dimensionsa=b=16.827(3) andc=15.951(16) Å; the structure was refined to R=4.9% using 1296 unique data with I>3(I_o). Its characteristics are discussed and compared with those of known compounds. The ratios of core volumes S₄/M₄ are within the 2.34–2.40 range for core oxidation level [MoFe₃S₄]³⁺ indicating that distortion of the cubane core is a general phenomenon. Different thiolato ligands induce significant changes of structural parameters only at the Fe(SR)₆ region for compound (2A) while terminal chlorides induce changes over the whole molecule of (3b) with the latter structure more comparable to [Mo₂Fe₆S₈(SPh)₉]^5– (3f) with [MoFe₃S₄]²⁺ core than to [Mo₂Fe₆S₈(SPh)₉]^3– (3d). The isotropic shifts of (2A) originate mainly from -contact interaction. Both¹H n.m.r. spectra and magnetic susceptibility measurements indicate practically no magnetic interaction among the three magnetic centres,i.e. a Fe(SR)₆ bridge and two [MoFe₃S₄(SR)₃] units. CV studies showed that the reduction of cubane unit having aromatic thiolates is easier than that having aliphatic thiolates as the aliphatic group is electron-donating. In addition, the very similar differences of E_p,c for first and second cubane units in compounds (2A) and in (3d) and (3e) imply that the effect of the first reduced unit [MoFe₃S₄]²⁺ upon the second unit [MoFe₃S₄]³⁺ is very similar in the two types of dicubane cluster compounds. Synergism in Mo–Fe–S cluster compounds is thus proposed to play an important role in their structural correlation with reactivities and must function in nitrogenase.     

The reactivity of N-2-(4-amino-1,6-dihydro-1-methyl-5-nitroso-6-oxopyrimidinyl)-L-histidine towards copper(II) ions

The acid–base properties of the N-substituted amino acid HL [HL = N-2-(4-amino-1,6-dihydro-1-methyl-5-nitroso-6-oxopyrimidinyl)-L-histidine] and its reactivity towards the Cu^II ion have been measured by potentiometric and spectrophotometric techniques in aqueous solution at 25 °C and 0.1 M KCl ionic strength. These studies show that the neutral HL compound is present in aqueous solution (3–7 pH range) in the zwitterionic form with the diprotonated imidazolic residue. Studies of HL/Cu^II mixtures reveal the existence of complex species with the neutral ligand, HL and containing the deprotonated L ligand. By controlling the reaction conditions, four solid phases of stoichiometry: CuLCl(H₂O)₆, Cu₂LCl₃(H₂O)₈, CuL₂(H₂O)₆ and Cu(HL)₂Cl₂(H₂O)₆ were isolated and characterised by i.r. and electronic spectroscopy, thermal techniques and magnetic measurements.     

Crystal structure of tetraethylammonium bis(tetracarbonylmolybdenum)-tetrathiotungstate, [EtN][(OC)MoSWSMo(CO)] and synthesis, infrared spectra, 95 Mo NMR spectra and cyclic voltammetry of new linear trinuclear Mo(W)–S carbonyl clusters containing mixed-valence metal atoms [(OC)MSM′SM(CO)]− (M, M′=Mo or W)

Four trinuclear molybdenum(tungsten)-sulfur carbonyl cluster compounds, [Et₄N]₂[(OC)₄Mo-S₂MoS₂Mo(CO)₄] (1), [Et₄N]₂[(OC)₄WS₂WS₂W(CO)₄] (2), [Et₄N]₂[(OC)₄MoS₂WS₂Mo(CO)₄] (3), [Et₄N]₂[(OC)₄WS₂MoS₂W(CO)₄] (4) have been prepared by both reaction of [M(CO)₄(S₂CNEt₂)]⁻ with M′S₄²− in MeOH and reaction of MeCN solution of M(CO)₆ with M′S₄²− in MeOH (M=Mo, W; M′=Mo, W). These complexes has been characterized by routine elemental analysis and spectroscopy and the structures of 1 and 3 have been determined by X-ray crystallography. The structure study reveals that the anion of 3 contains a heteronuclear Mo–W–S trimetallic core, [MoS₂WS₂Mo]²−, consisting of two perpendicular rhombic MoS₂W units sharing a tungsten atom. The Mo–W bond distances are 3.028(2) and 3.031(2) Å and the Mo–W–Mo angle is 176.04(5)°. The average bond lengths of W–S and Mo–S are 2.21 and 2.54 Å, respectively. The X-ray, structure, IR, CV (cyclic voltammetry) and 95 Mo NMR studies on these four cluster complexes indicated that these cluster complexes possess wide separated oxidation states of metal atoms and exhibit the charge transfer, M^L→M^HS₄ (M^L represents a low-valance metal atom and M^H a high valence metal atom), between the two different valence metallic centers in the cluster complexes. It has been found that the charge transfer, M^L→M^HS₄, in the complexes are: 1>4, 3>2, 1>3, 4>2, 1>2 and 34 implying the electron-donation ability of low-valence metal atoms in the complexes is Mo⁰>W⁰ and the electron-accepted ability of the high valence metal atoms in the complexes is Mo^VI>W^VI.     

Theoretical calculations of95Mo-NMR chemical shifts for compounds [MoO4−n S n ]2−

Summary Theoretical calculation of⁹⁵Mo-NMR chemical shifts for [MoO_4–n S _n ]^2– (n=0–4) compounds is reported here for the first time on the basis of Fenske-Hall method and Sum-Over-State (SOS) perturbation theory. A systematic decrease in shielding of⁹⁵Mo nuclei with increase of number of sulfur in [MoO_4–n S _n ]^2–, which is observed experimentally, can be reasonably explained by our calculation. A good linear relationship between chemical shifts of calculation and experiment is obtained. The electronic structure and bonding in these compounds are also discussed.Supported by Nature Science Foundation of China     

Coordination chemistry of poly(1-pyrazolyl)alkanes,part IV. Copper(II) complexes of bis- and tris-(1-pyrazolyl)methane

Summary The reactions of some copper(II) salts with bis(1-pyrazolyl)methane, H₂Cbpz, bis(3,5-dimethylpyrazolyl)methane, H₂Cbdmpz, and tris(1-pyrazolyl)methane, HCtpz give the following solid complexes: CuLX₂ · nH₂O (L=H₂Cbpz, H₂Cbdmpz or HCtpz; X=Cl^–, Br^–, NO ₃ ^– , OAc^–, or 1/2 SO ₄ ^2– and n=0, 1, 3 or 5) and CuL₂X₂ · nH₂O (L=HCtpz, X= C^–, Br^–, NO ₃ ^– or ClO ₄ ^– and n=0 or 2). The complexes have been characterised by elemental analysis, visible and i.r. spectral measurements.The reactions of Cu(HCtpz)X₂ · nH₂O (X=Cl^– or Br^–) with acetylacetonate (acac^–), dialkyldithiocarbamate (S₂CNMe ₂ ^– , S₂CNEt ₂ ^– ) or poly(1-pyrazolyl)borate (H₂Bbpz^–, HBtpz^–) in aqueous solutions lead to the displacement of HCtpz and the subsequent formation of neutral [Cu(acac)₂], [Cu(S₂CNR₂)₂], [Cu(H₂Bbpz)₂] and Cu(HBtpz)₂ while the reaction with oxalate ion, C₂O ₄ ^2– yields a stable neutral solid compound, [Cu(HCtpz)(C₂O₄)].     

Transition metal ion complexes of theS-methyldithiocarbazate prepared from 2-acetylpyridine

Summary Metal ion complexes of 2-acetylpyridineS-methyldithiocarbazate, HNNS, have been prepared and spectrally characterised. Preparations in EtOH yield complexes in which the deprotonated ligand, NNS, is complexedvia its pyridyl nitrogen, azomethine nitrogen, and thione sulphur. The stoichiometries are: [M(NNS)₂]X (M=Fe³⁺, Co³⁺ and X=ClO ₄ ^– , [FeCl₄]^–, BF ₄ ^– , 1/2 [CoCl₄]^2– and 1/2 [CoBr₄]^2–), [M(NNS)X] (M=Ni²⁺, Cu²⁺ and X=Cl^–, Br^–), [Cu(NNS)H₂O]BF₄ and Ni(HNNS)(NNS)F(EtOH)]BF₄. The spectral (i.e., i.r., u.v.-vis.-n.i.r. and e.s.r.) and physical properties of these complexes are compared to those of theS-methyldithiocarbazates of 2-formylpyridine and 2-acetylpyridineN-oxide, as well as the related thiosemicarbazones prepared from 2-acetylpyridine. Thermal studies of the nickel(II) complexes indicate that the nature of thermal decomposition of coordinated NNS is different from that of HNNS.     

Synthesis of 4-acetyl-5(3)-amino-3(5)-methylpyrazoles and pyrazolo[3,4-d]pyrimidines from diacetylketeneN,S-acetal

Isomeric 4-acetyl-5-amino-3-methyl- and 4-acetyl-3-amino-5-methylpyrazoles (2, 3) were formed in the reaction of hydrazines with 3-[amino(methylthio)methylene]pentan-2,4-dione (1) (diacetylketeneN,S-acetal). Pyrazolo[3,4-d]pyrimidines (5a,b) were synthesized by condensation of 4-acetyl-5-amino-1,3-dimethylpyrazole (2a) with amide dimethylacetals followed by treatment with ammonium acetate. The structures of the compounds obtained were confirmed by¹³C and¹⁵N NMR spectroscopy.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1429–1433, August, 1993.