Syntheses,crystal structures and luminescence of 2,6- bis - (5-phenyl-1H-pyrazol-3-yl)pyridine and its d10 metal complexes

A new bis-pyrazole derivative, 2,6-bis-(5-phenyl-1H-pyrazol-3-yl) pyridine (H₂BPPP), and two d¹⁰ metal complexes [Zn(H₂BPPP)Cl₂](DMF)₂ (1), [Cd(H₂BPPP)Cl₂](DMF)₂ (2) have been synthesized and characterized. There is a tautomeric equilibrium of the bis-pyrazole compound in solution and the H atom of pyrazolyl NH can transfer to the adjacent N atoms. X-ray structure analyses reveal the H atom is on the 2-position of pyrazolyl ring in donor solvents, while the H atom is on the 1-position of pyrazolyl ring in metal complexes. The luminescence of the ligand and complexes have been investigated.     

Synthesis of the new ligand bis[3-(2-pyrazinyl-pyrazol-1-yl) dihydroborate,and the crystal structures of its complexes with thallium(I) and lead(II)

Reaction of 3-(2-pyrazinyl)pyrazole with KBH₄ in a 21:1 ratio afforded the new ligand bis3, 2, 1dihydroborate [L]⁻a bis(pyrazolyl)borate in which each pyrazolyl ring is functionalised with a pyrazin-2-yl group at the C³ position[L]⁻ is therefore a potentially chelating tetradentate ligand with two externally-directed N atoms (the pyrazinyl N⁴ atoms) which are available for additional metal–ion bindingleading to eg coordination polymers The crystal structure of [TlL] shows it to be a simple mononuclear complex with the Tl(I) ion coordinated in the N₄ binding pocket of the ligandand the externally-directed N atoms involved only in intermolecular N H–C hydrogen-bonding interactions The two Tl–N bonds to the pyrazolyl N² atoms (average length 270 Å) are much shorter than the bonds to the pyrazinyl N¹ atoms (average length 305 Å) also there is an obvious gap in the apical position of the metal–ion coordination sphere characteristic of a stereochemically active lone pair The crystal structure of [PbL₂] Et₂O shows that the Pb(II) centre is nine-coordinate with two tetradentate chelating ligands and the ninth donor being a pyrazinyl N⁴ atom from an adjacent complex unit The molecules therefore form infinite one-dimensional chains in the crystal via bridging pyrazinyl groups The coordination geometry about the Pb(II) ions is approximately capped square antiprismatic with no obvious gap in the coordination sphere suggesting that the lone pair is stereochemically inactive.     

Three ways of reactions of 5-(3,5-dimethyl-1<Emphasis Type="Italic">H</Emphasis>-pyrazol-1-yl)-2-phenyl-1,3-oxazole-4-carbonitrile and its analogs with nitrogen-containing bases

Substituted 5-(3,5-dimethyl-1H-pyrazol-1-yl)-1,3-oxazole-4-carbonitrile differently react with nitrogen bases having different numbers of labile hydrogen atoms. Treatment of the title compounds with secondary amines or morpholine results in nucleophilic replacement of the pyrazolyl substituent at C⁵, the ozaxole ring remaining unchanged. Their reactions with primary amines are accompanied by cleavage of the oxazole ring with formation of the corresponding enamino nitriles. Hydrazine hydrate acts in a similar way, but enehydrazino nitriles thus formed undergo fast cyclization to give new 4,5-diaminopyrazole derivatives. The latter can be converted into substituted pyrazolo[1,5-a]pyrimidines whose structure has been proved by X-ray analysis.     

Peculiarities of the reaction of (SPY-5-34)-dichloro-(κ2(C,O)-2-formylbenzylidene)(1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene)ruthenium with potassium hydridotris(pyrazolyl)borate

The reaction of (SPY-5-34)-dichloro-(κ²(C,O)-2-formylbenzylidene)(H₂IMes)ruthenium (H₂IMes=1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene) with potassium hydridotris(pyrazolyl)borate (KTp) in dichloromethane yielded an unusual ruthenium complex chloro(κ³(N,N,N)-chlorotris(pyrazolyl)borate)(κ²(C,C)-1-(2,4,6-trimethylphenyl)-3-(4,6-dimethylphenyl-2-methylidene)-4,5-dihydroimidazol-2-ylidene)ruthenium (2). In 2, a chlorotris(pyrazolyl)borate ligand, which had been created during this reaction, binds in κ³(N,N,N)-mode to the central ruthenium atom. Additionally, a double C–H activation of a methyl group of the H₂IMes resulted in the formation of a chelating N-heterocyclic biscarbene ligand and liberation of the former 2-formylbenzylidene as 2-methylbenzaldehyde. Formally, a double hydrogen transfer from a methyl group of the H₂IMes to the initial carbene carbon occurred. 2 was characterized by NMR spectroscopy, elemental analysis and single crystal X-ray structure determination. The reaction of KTp with (SPY-5-34)-dichloro(κ²(C,O)-2-ethoxycarbonylbenzylidene)(H₂IMes)ruthenium, on the other hand, gave the expected product chloro(κ³(N,N,N)-hydridotris(pyrazolyl)borate)(H₂IMes)(2-ethoxycarbonylbenzylidene)ruthenium (6). Compound 6 was characterized by NMR spectroscopy, elemental analysis and single crystal X-ray structure determination. Investigations of the relative activities of these complexes in model ring opening metathesis polymerizations showed a pronounced thermal latency. Polymerizations proceeded at temperatures above 100 °C in case of 6 and 130 °C in case of 2.     

1H, 13C and 15N NMR spectra of [1,2-15N2]pyrazole derivatives

The chemical shifts and coupling constants of [1,2-¹⁵N₂]pyrazole, 2-(1-[1,2- ¹⁵N₂]pyrazolyl)-2-[l,3-²H₆]propanol, 1-nitro[1,2¹⁵N₂] and 3-nitro[1,2-¹⁵N₂]pyrazole are reported.     

Synthesis and structural characterization of fluorenyltris(pyrazol-1-yl)borate ligands as new examples of cyclopentadienyl/scorpionate hybrid ligands

Two fluorenyl/tris(pyrazol-1-yl)borate hybrid ligands, FlBpz₃Li and FlB(pz^3-tBu)₃Li, have been synthesized and structurally characterized by X-ray crystallography (Fl: 9-fluorenyl; pz: pyrazolyl). From the reaction of FlBpz₃Li and ZnCl₂ in THF, the dinuclear complex (THF)₃Lipz(Fl)Bpz₂ZnCl₂ was obtained in which a ZnCl₂ moiety is chelated by two pyrazolyl ligands while the third pz ring coordinates to an Li(THF)₃ fragment. Acetonitrile solutions of the compound gradually transform into the mononuclear species Fl(pz)Bpz₂Znpz₂B(pz)Fl featuring a distorted tetrahedral ZnN₄ core. In all molecular structures of [FlBpz₃]⁻ or [FlB(pz^3-tBu)₃]⁻ complexes investigated so far, the hybrid ligands adopt very similar conformations with only two pyrazolyl rings bonded to the central metal, whereas the third pyrazolyl acts as dangling substituent. The fluorenyl substituent of FlBpz₃Li may be deprotonated with KH in quantitative yield.     

The mass spectrum of 1-(2-thienyl) hexane-1-13C

The mass spectrum of 1-(2-thienyl) hexane-1-¹³C is reported. The principal fragmentation routes ofthe parent ion are delineated. Beta cleavage of the alkyl chain predominates, and the label retention indicates that the alpha carbon atom remains with the charged ring moiety. A substantial part of the m/e 97 ion undergoes a ring expansion to a six membered ring. A small amount of alpha cleavage of the alkyl chain occurs with the expected loss of the label. Further fragmentation of the ions from initial alpha or beta cleavage produces similar fragment ions. It is noted that many of the neutral particles lost in the formation of the fragment ions are typical of those encountered in the alkylbenzenes or other aromatic ion systems.     

Synthesis and tautomerism of 2-(3,5-diaryl-1H-pyrazol-4-yl)-1-methyl-1H-benzimidazoles

The cyclocondensation of 1-methyl-2-phenacyl-1H-benzimidazole with aroylhydrazines yields 2-(3,5-diaryl-1H-pyrazol-4-yl)-1-methyl-1H-benzimidazoles. The ¹H NMR spectra indicate that these products display tautomerism. The more stable tautomers have structures containing electron-donor aryl substituents at C-5 and electron-withdrawing aryl substituents at C-3 of the pyrazole ring.     

Synthesis and spectroscopic studies of diorganotin(IV) adducts based on cyclotriphosphazene scaffolds with exocyclic pyrazolyl substituents

Functionalized cyclotriphosphazenes with four pyrazolyl substituents have been employed for the synthesis of two new organotin complexes. These new compounds have been characterized by elemental analysis and IR, ¹H, ³¹P and ¹¹⁹Sn NMR spectroscopy. On the basis of these data, pyrazolylcyclotriphosphazene is bis-bidentate neutral ligand coordinating to two SnMe₂Cl₂ molecules in the resulting adducts. Coordination occurs only via the pyrazolyl nitrogens; cyclotriphosphazene ring nitrogens are not involved in coordination. The ¹¹⁹Sn NMR data are consistent with increasing of coordination number of tin(IV) in solution.     

Synthesis and isomerism of 2-(3,5-diaryl-1H-pyrazol-4-yl)-1H-benzimidazoles

2-(3,5-Diaryl-1H-pyrazol-4-yl)-1H-benzimidazoles have been obtained by the cyclocondensation of 2-phenacyl-1H-benzimidazoles with 4-nitro- and 4-methoxybenzoylhydrazines. The reaction mechanism and the isomerism of the obtained products are discussed. According to the data of ¹H NMR spectroscopy the stabilized isomer is that in which the electron-withdrawing aryl substituent is located in position 3 and the electron-donating substituent in position 5 of the pyrazole ring.     

Imidazolyl derivatives of the chroman ring. 1

The synthesis of 2-(1H-imidazol-1-yl)-2,3-dihydro-2H-1-benzopyran-4-ones (I) through 3-bromo-2,3-dihydro-4H-1-benzopyran-4-ones or more conveniently through chroman ring closure from 2-(1H-imidazol-1-yl)-2′-hydroxyacetophenones is described. The ring closure also works well for the pyrazolyl derivatives. Compounds I and the corresponding imidazolylchromanols, -chromenes, and -chromans derived from the former, were pharmacologically investigated.     

Structure and properties of 1-(2-pyridyl)-3-phenyl-5-arylformazans

A series of 1-(2-pyridyl)-3-phenyl-5-arylformazans, which form deeply colored complexes with Zn²⁺, Cu²⁺, Co²⁺, and Ni²⁺ salts, were obtained by coupling of arenediazonium salts, containing various substituants in the phenyl ring, with benzaldehyde 2-pyridylhydrazone. The presence of a nitro group causes deepening of the color and leads to the appearance of negative solvatochromism.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1379–1381, October, 1972.     

1-Methyl-2(3,4)-(1-vinylpyrrol-2-yl)pyridinium iodides: some structural features revealed by 1H and 13C NMR spectroscopy

The reactions of 2-, 3-, and 4-(1-vinylpyrrol-2-yl)pyridines with methyl iodide afford the corresponding quaternary salts. Analysis of their ¹H and ¹³C NMR spectra showed that the quaternization of the nitrogen atom considerably enhances the -acceptor effect of the pyridine ring on the pyrrole ring and on the vinyl group. 1-Methyl-2-(1-vinylpyrrol-2-yl)pyridinium iodide contains no weak intramolecular C--H...N hydrogen bond present in the starting compound.     

Protophilic isotopic hydrogen exchange of 1-ferrocenyl-2-(nitrophenyl)ethylenes

cis-1-Ferrocenyl-2-(4-nitrophenyl)ethylene enters into the protium/deuterium exchange in basic medium at the expense of hydrogens of the phenyl ring, at ortho positions in respect of the nitro group. The homoaromatic analogue, 4-nitrostilbene, under the same conditions, undergoes isotopic exchange occurring exclusively at the vinylic CH fragment attached to the nitrophenyl group. The difference is eliminated as a result of the shift of the nitro group from position 4 into position 2 of the phenyl ring: cis-1-ferrocenyl-2-(2-nitrophenyl)ethylene enters into H⁺/D⁺ exchange in the same manner as 4-nitrostilbene. Correspondence to: Professor Z.V. Todres.     

Reaction of 5-(2-furyl)-1-methyl-1<Emphasis Type="Italic">H-</Emphasis> and 1-methyl-5-(2-thienyl)-1<Emphasis Type="Italic">H</Emphasis>-imidazoles with electrophilic reagents

5-(2-Furyl)-1-methyl-1H- and 1-methyl-5-(2-thienyl)-1H-imidazoles were synthesized. The electronwithdrawing effect of the 5- and 2-imidazole substituents on the furan ring was studied by ¹H NMR spectroscopy and quantum-chemical calculations. Some electrophilic substitution reactions were investigated (nitration, bromination, sulfonation, hydroxymethylation, formylation, and acylation). In some cases, depending on the reaction conditions, both the furan and thiophene ring and the imidazole fragment undergo electrophilic attack.     

桥头碳上氮杂芳基功能化的双吡唑甲烷与羰基钨反应

研究了(氮甲基咪唑-2-基)双(3,5-二甲基吡唑)甲烷(L¹),2-吡啶基双(3,5-二甲基吡唑)甲烷(L²)及4-吡啶基双(3,5-二甲基吡唑)甲烷(L³)与羰基钨的反应,合成了一系列以单齿,双齿及三齿氮配位的羰基金属衍生物LW(CO)₅ (L=L¹或L³),LW(CO)₄ (L=L¹,L²或L³)和LW(CO)₃ (L=L¹或L²).核磁,红外及X-射线单晶衍射分析表明这3种配体表现出了可变的配位方式.在LW(CO)₅中,当配体为L¹时,其倾向于通过咪唑氮与金属配位,而为L³则倾向于利用吡啶氮与金属作用;在LW(CO)₄中,配体L¹表现为通过咪唑氮和吡唑氮原子配位的[N,N']双齿配体,而L²和L³表现为通过吡唑氮原子配位的[N,N]双齿配体;在LW(CO)₃中,L¹和L²起着[N,N,N']三齿螯合配体的作用.     

Low temperature 13C NMR study of 1-(3-pentyloxyphenylcarbamoyloxy)-2-dialkyl- aminocyclohexanes

Cyclohexane and piperidine ring reversal in 1-(3-pentyloxyphenylcarbamoyloxy)-2-dialkylaminocyclohexanes was investigated by ¹³C NMR. An unusually low conformational energy ΔG = 0.59 kJ mol^?1 and activation parameters ΔG^≠₂₁₈ = 43.8 ± 0.4 kJ mol^?1, ΔH^≠ = 48.9 ± 2.5 kJ mol^?1 and ΔS^≠ = 23 ± 9 J mol^?1 K^?1 were found for the diequatorial to diaxial transition of the cyclohexane ring in the trans-pyrrolidinyl derivative. In the trans-piperidinyl derivative, ΔG₂₂₂ = 44.7 ± 0.5 KJ mol^?1, ΔH^≠ = 55.7 ± 6.3 kJ mol^?1 and ΔS^≠ = 51 ± 21 J mol^?1 K^?1 was found for the piperidine ring reversal from the non-equivalence of the α-carbons.     

桥头碳上氮杂芳基功能化的双吡唑甲烷与羰基钨反应

研究了(氮甲基咪唑-2-基)双(3,5-二甲基吡唑)甲烷(L1),2-吡啶基双(3,5-二甲基吡唑)甲烷(L2)及4-吡啶基双(3,5-二甲基吡唑)甲烷(L3)与羰基钨的反应,合成了一系列以单齿,双齿及三齿氮配位的羰基金属衍生物LW(CO)5(L=L1或L3),LW(CO)4(L=L1,L2或L3)和LW(CO)3(L=L1或L2)。核磁,红外及X-射线单晶衍射分析表明这3种配体表现出了可变的配位方式。在LW(CO)5中,当配体为L1时,其倾向于通过咪唑氮与金属配位,而为L3则倾向于利用吡啶氮与金属作用;在LW(CO)4中,配体L1表现为通过咪唑氮和吡唑氮原子配位的[N,N′]双齿配体,而L2和L3表现为通过吡唑氮原子配位的[N,N]双齿配体;在LW(CO)3中,L1和L2起着[N,N,N′]三齿螯合配体的作用。     

Extraction of hydrochloric and nitric acid with 1-{[2-(2,4-Dichlorophenyl)-4-propyl-1,3-dioxolan-2-yl]-methyl)-1H-1,2,4-triazole and (RS)-1-(4-Chlorophenyl)-4,4-dimethyl-3-(1H-1,2,4-triazol-1-yl-methyl)-pentan-3-ol

Extraction of hydrochloric and nitric acid with 1-{[2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolan-2-yl]-methyl}-1H-1,2,4-triazole (propiconazole) and hydrochloric acid with (RS)-1-(4-chlorophenyl)-4,4-dimethyl-3-(1H-1,2,4-triazol-1-yl-methyl)-pentan-3-ol (tebuconazole) was studied. It is established that extraction of acids proceeds with the formation of monosolvates as an exothermic process. Effective extraction constants of acids are evaluated. By means of the IR and ¹H NMR spectroscopy it was shown that the protonaccepting center of tebuconazole is N⁴ atom of the triazole ring.