Nickel(II) chain with alternating end-on/end-to-end single azido bridges: a combined structural, magnetic, and theoretical study

The reaction of a tridentate Schiff base LH (L-: 1,1,1-trifluoro-7-(dimethylamino)-4-methyl-5-aza-3-hepten-2-onato) with a Ni(II) salt in the presence of azide salt has led to a new alternating end-on (EO)/end-to-end (EE) azido-bridged Ni(II) chain of formula {[Ni2(micro1,1-N3)(micro1,3-N3)(L)2(MeOH)2]}n. Its originality lies in the presence of single EE and EO coordination modes for the azide. It crystallizes in the C2/c space group, a=21.570(7) A, b=10.79(1) A, c=16.154(5) A, beta=120.81(2) degrees, Z=4. The chain can be viewed as {Ni2(N3)(L)2(MeOH)2}+ dimeric units linked to each other in a zigzag pattern by the other azide. Magnetic susceptibility and magnetization measurements have been performed and revealed that the chain can magnetically be depicted as isolated {Ni2(N3)} units exhibiting antiferromagnetic interaction (JAF approximately -37 cm(-1)). Ab initio calculations confirmed the efficient magnetic coupling through the EE bridge and vanishingly small EO {Ni2(micro1,1-N3)} interactions.     

4'-substituted-4-biphenylyloxenium ions: reactivity and selectivity in aqueous solution

Azide trapping shows that the 4'-substituted-4-biphenylyloxenium ions 1b-d are generated during hydrolysis of 4-aryl-4-acetoxy-2,5-cyclohexadienones, 2c and 2d, and O-(4-aryl)phenyl-N-methanesulfonylhydroxylamines, 3b and 3c. In addition, the 4'-bromo-substituted ester, 2d, undergoes a kinetically second-order reaction with N3- that accounts for a fraction of the azide adduct, 5d. Since both first-order and second-order azide trapping occurs simultaneously in 2d, the second-order reaction is not enforced by the short lifetime of 1d, which has similar azide/solvent selectivity to the unsubstituted ion, 1a. In contrast the 4'-CN and 4'-NO2 ions 1e and 1f cannot be detected by azide trapping during the hydrolysis of the dichloroacetic acid esters 2e' and 2f' even though 18O labeling experiments show that a fraction of the hydrolysis of both esters occurs through C(alkyl)-O bond cleavage. These esters exhibit only second-order trapping by azide. Correlations of the azide/solvent selectivities of 1a-d with the calculated relative driving force for hydration of the ions (DeltaE of eq 4) determined at the pBP/DN//HF/6-31G and BP/6-31G//HF/6-31G levels of theory suggest that 1e and 1f have lifetimes in the 1-100 ps range. Ions with these short lifetimes are not in diffusional equilibrium with nonsolvent nucleophiles, and must be trapped by such nucleophiles via a preassociation mechanism. The second-order trapping that is observed in these two cases is enforced by the short lifetime of the cations, and may occur by a concerted S(N)2' mechanism or by internal azide trapping of an ion sandwich produced by azide-assisted ionization. Comparison of azide/solvent selectivities of the oxenium ions 1a-c with the corresponding biphenylylnitrenium ions 8a-c shows that 4'-substituent effects on reactivity in both sets of ions are similar in magnitude, although the nitrenium ions are ca. 30-fold more stable in an aqueous environment than the corresponding oxenium ions. The magnitude of the 4'-substituent effects for electron-donating substituents suggest that both sets of ions are more accurately described as 4-aryl-1-imino-2,5-cyclohexadienyl or 4-aryl-1-oxo-2,5-cyclohexadienyl carbocations. Calculated structures of the oxenium ions are also consistent with this interpretation.     

Regiospecific synthesis of 2-allyl-1,2,3-triazoles by palladium-catalyzed 1,3-dipolar cycloaddition

2-Allyl-1,2,3-triazoles were prepared by the palladium-catalyzed three component coupling (TCC) reaction of alkynes, allyl methyl carbonate and trimethylsilyl azide. A π-allylpalladium azide complex, which undergoes the 1,3-dipolar cycloaddition with alkynes, is proposed as a key intermediate in the TCC reaction.     

Hochdrucksynthese von Caesiumamidazid,Cs2(NH2)N3 aus Caesiummetall und Ammoniak

High-pressure Synthesis of Cesium Amide Azide, Cs₂(NH₂)N₃ from Cesium Metal and Ammonia The reaction of cesium and yttrium metal with ammonia at 5–6 kbar and 190–220°C led to a well crystallized cesium amide azide and to YN. The formation of the cesium compound is discussed by volume effects. X-ray investigations gave the atomic arrangement of the compound. The tetragonal unit cell with a = 8.194(3) and c = 4.450(1) Å contains two formula units. The structure determination was successfull in the space group P4/mbm. The azide ion has different coordination and bond length (1.255 Å) as compared with that in the alkali metal azides (1.17 Å). The amide ions carry out a strong libration.     

Reaction of 2,4,6-triazido-1,3,5-triazine with triphenylphosphane. syntheses and characterization of the novel 2-triphenylphosphanimino-4-azidotetrazolo[5,1-a]-[1,3,5]triazine and 2,4,6,-tris(triphenylphosphanimino)-1,3,5-triazine

2-Triphenylphosphanimino-4-azidotetrazolo[5,1-a]-[1,3,5]triazine (6) was obtained by reaction of 2,4,6-triazido-1,3,5-triazine (1) with 1 equiv of triphenylphosphane. Raman and X-ray data revealed that only one azide group formed a tetrazole ring system whereas the second azide group did not undergo ring closure. To investigate the equilibrium between the tetrazole isomer and the open-chain azide structure for these and related species, (31)P NMR studies were carried out. The obtained spectra displayed an equilibrium between the tetrazole and the open-chain azide isomers. 2,4,6-Tris(triphenylphosphanimino)-1,3,5-triazine (4) was prepared by treatment of 1 with 3 equiv of triphenylphosphane, and its X-ray structure is discussed. On the basis of PM3 semiempirical and density functional calculations, the reaction of 1 with triphenylphosphane was studied. The thermodynamics of different isomerization reactions and the activation barriers to cyclization were estimated.     

Syntheses,structural analyses,and magneto-structural correlations of three polymeric Fe(II) complexes with azide ligand

Three new metal-organic polymeric complexes, [Fe(N(3))(2)(bpp)(2)] (1), [Fe(N(3))(2)(bpe)] (2), and [Fe(N(3))(2)(phen)] (3) [bpp = (1,3-bis(4-pyridyl)-propane), bpe = (1,2-bis(4-pyridyl)-ethane), phen = 1,10-phenanthroline], have been synthesized and characterized by single-crystal X-ray diffraction studies and low-temperature magnetic measurements in the range 300-2 K. Complexes 1 and 2 crystallize in the monoclinic system, space group C2/c, with the following cell parameters: a = 19.355(4) A, b = 7.076(2) A, c = 22.549(4) A, beta = 119.50(3) degrees, Z = 4, and a = 10.007(14) A, b = 13.789(18) A, c = 10.377(14) A, beta = 103.50(1) degrees, Z = 4, respectively. Complex 3 crystallizes in the triclinic system, space group P(-)1, with a = 7.155(12) A, b = 10.066(14) A, c = 10.508(14) A, alpha = 109.57(1) degrees, beta = 104.57(1) degrees, gamma = 105.10(1) degrees, and Z = 2. All coordination polymers exhibit octahedral Fe(II) nodes. The structural determination of 1 reveals a parallel interpenetrated structure of 2D layers of (4,4) topology, formed by Fe(II) nodes linked through bpp ligands, while mono-coordinated azide anions are pendant from the corrugated sheet. Complex 2 has a 2D arrangement constructed through 1D double end-to-end azide bridged iron(II) chains interconnected through bpe ligands. Complex 3 shows a polymeric arrangement where the metal ions are interlinked through pairs of end-on and end-to-end azide ligands exhibiting a zigzag arrangement of metals (Fe-Fe-Fe angle of 111.18 degrees) and an intermetallic separation of 3.347 A (through the EO azide) and of 5.229 A (EE azide). Variable-temperature magnetic susceptibility data suggest that there is no magnetic interaction between the metal centers in 1, whereas in 2 there is an antiferromagnetic interaction through the end-to-end azide bridge. Complex 3 shows ferro- as well as anti-ferromagnetic interactions between the metal centers generated through the alternating end-on and end-to-end azide bridges. Complex 1 has been modeled using the D parameter (considering distorted octahedral Fe(II) geometry and with any possible J value equal to zero) and complex 2 has been modeled as a one-dimensional system with classical and/or quantum spin where we have used two possible full diagonalization processes: without and with the D parameter, considering the important distortions of the Fe(II) ions. For complex 3, the alternating coupling model impedes a mathematical solution for the modeling as classical spins. With quantum spin, the modeling has been made as in 2.     

Synthesis of Dopamine,Rotigotin, Ladostigil,Rasagiline Analogues 2-Amino-4,5,6-trimethoxyindane, 1-Amino-5,6,7-trimethoxyindane,and Their Sulfamide Derivatives

Dopamine, rotigotin, ladostigil, and rasagiline analogues 2-amino-4,5,6-trimethoxyindane and 1-amino-5,6,7-trimethoxyindane were synthesized starting from 5,6,7-trimethoxyindan-1-one for the first time with 34% and 45% total yields. α-Carboxylation of indanone, reduction of ketone group with Et₃SiH, basic hydrolysis of ester, Curtius reaction of the acid, and addition of BnOH afforded the corresponding carbamate. Pd-C-catalyzed hydrogenolysis of carbamate and deprotonation of amine hydrochloride with NaOH gave the dopamine and rotigotin analogue 2-aminoindane. Reduction of 5,6,7-trimethoxyindan-1-one with NaBH₄ afforded the alcohol, which was then converted to the azide derivative via Mitsunobu reaction with diphenylphosphoryl azide; Pd-C catalyzed hydrogenation of the azide to the amine hydrochloride and then deprotonation of the amine hydrochloride with NaOH furnished the ladostigil and rasagiline analogue 1-aminoindane. These amines and BnOH were reacted with CSI to produce sulfamoyl carbamates, which were converted to sulfamides via Pd-C-catalyzed hydrogenolysis reaction with 20% and 25% total yields.     

A one-pot procedure for the regiocontrolled synthesis of allyltriazoles via the Pd-Cu bimetallic catalyzed three-component coupling reaction of nonactivated terminal alkynes, allyl carbonate, and trimethylsilyl azide

A one-pot procedure for the regiocontrolled synthesis of both 2-allyl- and 1-allyl-1,2,3-triazoles via the three-component coupling (TCC) reaction between nonactivated terminal alkynes, allyl carbonate, and trimethylsilyl azide (TMSN(3)) under a palladium and copper bimetallic catalyst has been developed. To accomplish the regioselective synthesis of the allyltriazoles, proper choice of two different catalyst systems is needed. The combination of Pd(2)(dba)(3).CHCl(3)-CuCl(PPh(3))(3)-P(OPh)(3) catalyzes the formation of 2-allyl-1,2,3-triazoles, while the combination of Pd(OAc)(2)-CuBr(2)-PPh(3) promotes the formation of 1-allyl-1,2,3-triazoles. The cooperative activity of palladium and copper catalysts plays an important role in the present transformations. Most probably, the palladium catalyst works as a catalyst for generating reactive azide species, pi-allylpalladium azide complex and allyl azide. The copper catalyst probably behaves as an activator of the C-C triple bond of the starting terminal alkynes by forming a copper-acetylide intermediate and thereby promotes the [3 + 2]-cycloaddition reaction between the reactive azide species and the copper-acetylide to form the triazole framework.     

Synthesis of 1H-1,5,7-triazacyclopenta[<Emphasis Type="Italic">c,d</Emphasis>]phenalenes by the electrophilic amination of perimidines using sodium azide in PPA

A method was developed for the synthesis of 1H-1,5,7-triazacyclopenta[c,d]phenalenes by the electrophilic amination of perimidines using the new sodium azide/PPA reagent system and a subsequent one-pot reaction with 1,3,5-triazines. A multicomponent variant of this reaction is possible in the case of 2,4,6-trimethyl- and 2,4,6-triphenyl-1,3,5-triazines.     

A New Method of Dimroth Rearrangement in Fused Triazolo[1,5‐d]‐1,2,4‐triazine

Ethyl 7‐(2‐ethoxy‐2‐oxoethyl)‐3‐phenyl‐[1–3]triazolo[5,1‐c][1,2,4]triazine‐6‐carboxylate (the parent compound) was synthesized by reaction of 4‐phenyl–1H‐1,2,3‐triazole‐5‐diazonium chloride with diethyl‐2‐oxopropane‐1,3‐dicarboxylate at cooling for 2 h. During the reaction of the parent compound with p‐toluenesulphonyl azide in triethylamine, the Dimroth rearrangement occurred to give the tricyclic compound.     

Amine-catalyzed addition of azide ion to alpha,beta-unsaturated carbonyl compounds

[formula: see text] A new protocol for the beta-azidation of alpha,beta-unsaturated carbonyl compounds is described. The method employs tertiary amines as catalysts for azide addition. The azide source is a 1:1 mixture of TMSN3 and AcOH. Tertiary amines, either in solution or bound to a solid support, are efficient catalysts for the reaction.     

Azide Ionic Liquids for Safe,Green, and Highly-Efficient Azidation Reactions to Produce Azide Polymers

Azide compounds are widely used and especially, polymers bearing pendant azide groups are highly desired in numerous fields. However, harsh reaction conditions are always mandatory to achieve full azidation, causing severe side reactions and degradation of the polymers. Herein, we report the design and preparation of two azide ionic liquids (AILs) with azide anion and triethylene glycol (E₃)-containing cation, [P_444E3][N₃] and [MIM_E3][N₃]. Compared with the traditional sodium azide (NaN₃) approach, both AILs showed much higher reaction rates and functional-group tolerance. More importantly, they could act as both reagents and solvents for the quantitative azidation of various polymeric precursors under mild conditions. Theoretical simulations suggested that the outstanding performance of AILs originated from the existence of ion pairs during the reaction, and the E₃ moieties played a crucial role. Lastly, after the reaction, the AILs could be easily regenerated, presenting a safer, greener, and highly efficient synthesis route for azide polymers.     

N,N′‐Diorganylsubstituted Hydrazinium Azides

1,2‐Diorganylsubstituted derivatives of hydrazinium azide were examined in order to investigate their higher volatility and higher sensitivity to initiation compared to 1,1‐diorganylsubstituted hydrazinium azide derivatives. The compounds were synthesized from the respective hydrazines by reaction with HN₃ and characterized by elemental analysis, vibrational (IR, Raman) and multinuclear NMR spectroscopy (¹H, ¹³C, ¹⁴N). Their sensitivity to friction, shock, electrostatic impact and heat was examined and the explosion products were investigated. The crystal structure of pyrazolidinium azide was determined.     

Synthesis and Reaction of Novel Spiro Pyrimidine Derivatives

2‐Mercapto‐6‐[(pyridin‐4‐ylmethylene)‐amino]‐3H‐pyrimidin‐4‐one 1 was synthesized from Schiff base reaction of 6‐amino‐2‐thiouracil with isonicotinaldehyde. The reaction of 1 with hydrazonyl chloride 2a , 2b , 2c , 2d afforded the novel pyrimidin‐4‐one 3a , 3b , 3c , 3d . Compounds 3a , 3b , 3c , 3d reacted with methyl iodide to give 4a , 4b , 4c , 4d . Subsequently, reaction of 4a , 4b , 4c , 4d with triethylamine as a catalyst in dry chloroform yielded tetraaza‐spiro[4.5]deca‐2, 8‐dien‐7‐one 5a , 5b , 5c , 5d . In addition, reaction of 1 with acrylonitrile gave pyrimidin‐propionitrile 6 . The cyclization of 6 by reacting with sodium ethoxide to give pyrimido [2, 1‐b] [1,3] thiazin‐6‐one 7 . The refluxing of 1 with bromine in acetic acid yielded 2‐bromo‐pyrimidin‐4‐one 8 . The latter compound 8 reacted with sodium azide gave tetrazolo‐pyrimidine 10 . The chemical structures of the newly synthesized compounds were characterized by IR, ¹H NMR, ¹³C NMR, and mass spectral analysis.     

Steric and hydrogen-bonding effects on the stability of copper complexes with small molecules

A series of the copper(II) complexes with tripodal tetradentate tris(pyridyl 2-methyl)amine-based ligands possessing the hydrogen-bonding 6-aminopyridine units (tapa, three amino groups; bapa, two amino groups; mapa, one amino group) have been synthesized, and their copper(II) complexes with a small molecule such as dioxygen and azide have been studied spectroscopically and structurally. The reaction of their Cu(II) complexes with NaN(3) have given the mononuclear copper complexes with azide in an end-on mode, [Cu(tapa)(N(3))]ClO(4) (1a), [Cu(bapa)(N(3))]ClO(4) (2a), [Cu(mapa)(N(3))]ClO(4) (3a), and [Cu(tpa)(N(3))]ClO(4) (4a) (tpa, no amino group). The crystal structures have revealed that the coordination geometries around the metal centers are almost a trigonal-bipyramidal rather than a square-planar except for 1a with an intermediate between them. The UV-vis and ESR spectral data indicate that the increase of NH(2) groups of ligands causes the structural change from trigonal-bipyramidal to square-pyramidal geometry, which is regulated by a combination of steric repulsion and hydrogen bond. The steric repulsion of amino groups with the azide nitrogen gives rise to elongation of the Cu-N(py) bonds, which leads to the positive shift of the redox potentials of the complexes. The hydrogen bonds between the coordinated azide and amino nitrogens (2.84-3.05 A) contribute clearly to the fixation of azide. The Cu(I) complexes with bapa and mapa ligands have been obtained as a precipitate, although that with tapa was not isolated. The reactions of the Cu(I) complexes with dioxygen in MeOH at -75 degrees C have given the trans-micro-1,2 peroxo dinuclear Cu(II) complexes formulated as [((tapa)Cu)(2)(O(2))](2+) (1c), [((bapa)Cu)(2)(O(2))](2+) (2c), and [((mapa)Cu)(2)(O(2))](2+) (3c), whose characterizations were confirmed by UV-vis, ESR, and resonance Raman spectroscopies. UV-vis spectra of 1c, 2c, and 3c exhibited intense bands assignable to pi(O(2)(2)(-))-to-d(Cu) charge transfer (CT) transitions at lambda(max)/nm (epsilon/M(-1)cm(-1)) = 449 (4620), 474 (6860), and 500 (9680), respectively. The series of the peroxo adducts generated was ESR silent. The resonance Raman spectra exhibited the enhanced features assignable to two stretching vibrations nu((16)O-(16)O/(18)O-(18)O)/cm(-1) and nu(Cu-(16)O/Cu-(18)O)/cm(-1) at 853/807 (1c), 858/812 (2c), 847/800 (3c), and at 547/522 (2c), 544/518 (3c), respectively. The thermal stability of the peroxo-copper species has increased with increase in the number of the hydrogen-bonding interactions between the peroxide and amino groups.     

Three-Component Reactions with Sterically Crowded 2,2,4,4-Tetramethyl-3-thioxocyclobutanone,Phenyl Azide,and Electron-Deficient C,C-Dipolarophiles

In order to trap ‘thiocarbonyl-aminides’ A , formed as intermediates in the reaction of thiocarbonyl compounds with phenyl azide, a mixture of 2,2,4,4-tetramethyl-3-thioxocyclobutanone ( 1 ), phenyl azide, and fumarodinitrile ( 8 ) was heated to 80° until evolution of N₂ ceased. Two interception products of the ‘thiocarbonylaminide’ A (Ar?Ph) were formed: the known 1,4,2-dithiazolidine 3 (cf. Scheme 1) and the new 1,2-thiazolidine 12 (Scheme 2). The structure of the latter was established by X-ray crystallography (Fig.1). The analogous ‘three-component reaction’ with dimethyl fumarate ( 9 ) yielded, instead of 8 , in addition to the known interception products 3 and 6 (Scheme 1), two unexpected products 15 and 16 (Scheme 3), of which the structures were elucidated by X-ray crystallography (Fig.2). Their formation is rationalized by a primary [2 + 3] cycloaddition of diazo compound 18 with 1 to give 19 , followed by a cascade of further reactions (Scheme 4).     

Calcium-diazido-di-dimethylformamid,Ca(N3)2[OCHN(CH3)2]2 Darstellung und Kristallstruktur

Calcium-diazido-di-dimethylformamide, Ca(N₃)₂[OCHN(CH₃)₂]₂, Preparation and Crystal Structure The title compound was prepared by the reaction of Ca(N₃)₂ with OCHN(CH₃)₂ in aqueous solution. The crystals are orthorhombic, a = 968.5(3), b = 1 479.6(15), c = 1 945.3(17) pm, space group Cmca, Z = 8. The crystal structure was determined by single crystal X-ray diffraction techniques and refined to R = 0.061. Calcium atoms are surrounded by four terminal nitrogen atoms of azide groups and by two oxygen atoms of dimethylformamide (DMF). The polyhedra around Ca are octahedra which are linked via four azide groups to form Ca(N₃)₂ layers. The DMF molecules are located between these layers, and they are highly disordered.     

Mechanisms of tetrazole formation by addition of azide to nitriles

It is well-known that azide salts can engage nitriles at elevated temperatures to yield tetrazoles; however, there is continued debate as to the mechanism of the reaction. Density functional theory calculations with the hybrid functional B3LYP have been performed to study different mechanisms of tetrazole formation, including concerted cycloaddition and stepwise addition of neutral or anionic azide species. The calculations presented here suggest a previously unsuspected nitrile activation step en route to an imidoyl azide, which then cyclizes to give the tetrazole. The activation barriers are found to correlate strongly with the electron-withdrawing potential of the substituent on the nitrile.     

Synthesis of 1‐methyl‐, 4‐nitro‐, 4‐amino‐and 4‐iodo‐1,2‐dihydro‐3H‐pyrazol‐3‐ones

4‐Aminopyrazole‐3‐ones 4b, e, f were prepared from pyrazole‐3‐ones 1b‐d in a four‐step reaction sequence. Reaction of the latter with methyl p‐toluenesulfonate gave 1‐methylpyrazol‐3‐ones 2b‐d . Compounds 2b‐d were treated with aqueous nitric acid to give 4‐nitropyrazol‐3‐ones 3b‐d. Reduction of compounds 3b‐d by catalytic hydrogenation with Pd‐C afforded the 4‐amino compounds 4b, e, f. Using similar reaction conditions, nitropyrazole‐3‐ones derivatives 2c, d were reduced into aminopyrazole‐3‐ones 5e, f. 4‐Iodopyrazole‐3‐ones 7a, 7c and 8 were prepared from the corresponding pyrazol‐3‐ones 2a, 2c and 6 and iodine monochloride or sodium azide and iodine monochloride.     

Time-resolved laser fluorescence spectroscopy and extended X-ray absorption spectroscopy investigations of the N3- complexation of Eu(III), Cm(III), and Am(III) in an ionic liquid: differences and similarities

The complexation of the lanthanide Eu(III) and the actinides Cm(III) and Am(III) by N3- was investigated by application of time-resolved laser fluorescence spectroscopy (TRLFS) and X-ray absorption spectroscopy (XAFS) in the ionic liquid solution of C4mimTf2N (1-butyl-3-methylimidazolium-bis(trifluoromethylsulfonyl)imide). TRLFS measurements show that the interaction of azide with Eu(CF3SO3)3 and Eu(ClO4)3 results in both dynamic luminescence quenching by collisional encounters of N3- with Eu(III) and static luminescence quenching by inner-sphere complexation of Eu(III) by N3-. Hereby, the complexation of Eu-triflate by azide starts at a lower N3- concentration as compared to the perchlorate salt. The authors ascribe this phenomenon to a stronger bonding of ClO4- toward the metal ion than triflate, as well as to a stronger electrostatic repulsion of N3- by the perchlorate ligand. In both actinide samples (Cm(ClO4)3, Am(ClO4)3), the complexation with azide exhibits a clear kinetic hindrance. Nevertheless, mixed actinide-perchlorate-azide complexes are formed after several days in C4mimTf2N. The different reaction kinetics for the Ln- and An-complexation by azide may provide the opportunity for an effective separation of lanthanides from actinides in the nuclear fuel cycle by the use of N-based extractants in ionic liquid solution.