Mononuclear palladacycles of N,N′-diaryl-2-iminoisoindolines

Reaction of acetato-bridged dinuclear palladacycles, [Pd(iminoisoindoline)(μ-OAc)]₂, with stoichiometric amounts of PR₃ (where R = Ph or Cy) resulted in formation of the corresponding mononuclear phosphine-ligated, six-membered palladacycles with the general formula [Pd(iminoisoindoline)(OAc)PR₃]. The analogous chloride complexes were synthesized by reaction of [Pd(iminoisoindoline)(μ-OAc)]₂ with LiCl in acetone followed by addition of phosphine to afford the monomeric derivatives [Pd(iminoisoindoline)(Cl)PR₃]. Representative crystal structures of both types of mononuclear palladacycles confirmed the mononuclear nature of the complexes and showed a trans-arrangement of the phosphine ligand to the heterocyclic imine-nitrogen of the palladacycles.     

Negative ion photoelectron spectroscopy of N2O− and (N2O)−2

We have recorded the photoelectron spectra of the gas phase negative ions N₂O⁻ and (N₂O)₂⁻ both of which were prepared in a nozzle ion source. The shift between the maxima of the two spectra is interpreted in terms of the dissociation energy of the dimer ion.     

Synthesis of guanidines via the I2 mediated desulfurization of N,N′-di-Boc-thiourea

The I₂ mediated desulfurization of N,N′-di-Boc-thiourea was developed. Various primary amines, including sterically and electronically deactivated primary amines, were transformed into the corresponding bis-Boc protected guanidines under mild conditions.     

Reaction of 2-formyl-1,3-cyclanediones with N,N′-substituted 1,1-diamino-2-nitroethylenes

Reaction of 2-formyldimedone and 2-formyl-1,3-indanedione with 1,1-di(2-hydroxyethylamino)- and 1,1-di(4-morpholyl)-2-nitroethylenes produces 2-[3,3-di(2-hydroxyethylamino)-2-nitroprop-2-en-1-ylidene]- and 2-[3,3-di(4-morpholyl)-2-nitroprop-2-en-1-ylidene]-5,5-dimethyl-1,3-cyclohexanediones and the 1,3-indanediones, respectively. The reaction of the same 2-formyl-1,3-cyclanediones with 2-nitromethyleneimidazolidine yields 8,8-dimethyl-4-nitro-6-oxo-1,2,3,6,7,8-hexahydroimidazo[1,2-a]quinoline and 4-nitro-6-oxo-1,2-dihydro-6H-imidazo[1,2-c]-4-azafluorene.Riga Technical University, Riga LV-1658, Latvia; e-mail: marina@osi.lanet.lv. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 330–333, March, 1999.     

Intramolecular cyclization of 1,3-diamino-2-hydroxypropan-N,N,N´,N´-tetrakis(methylphosphonic acid) upon phosphonomethylation of 1,3-diaminopropan-2-ol

Phosphonomethylation of 1,3-diaminopropan-2-ol affords the mixture of 1,3-diamino-2-hydroxypropan-N,N,N´,N´-tetrakis(methylphosphonic acid) (1) with its cyclic ether, viz., [(6-[bis(phosphonomethyl)amino]methyl-2-hydroxy-2-oxido-1,4,2-oxazaphosphinan-4-yl)methyl]phosphonic acid (2), but not 1, as assumed earlier.

     

Synthesis and structural features of copper(II) complexes of N,N,N′,N′-tetramethylethylenediamine with 2-chlorobenzoate1− and 2-hydroxybenzoate1−

Abstract

Two copper(II) coordination complexes, formulated as [Cu(tmen)(Clba)₂] (1) and [Cu(tmen)(Hsal)₂·H₂O] (2) (where tmen?=?N,N,N′,N′-tetramethyl ethylenediamine (C₆H₁₆N₂), Clba^1? = 2-chlorobenzoate (C₇H₄ClO₂^1?), and Hsal^1? (C₇H₅O₃^1? = monoanion of o-hydroxybenzoic acid (salicylic acid)), have been synthesized and characterized by elemental combustion analysis, spectroscopic techniques, thermal studies, and single crystal X-ray analyses. Complex 1 consists of two distinct monomeric units in which the coordination environment around the central copper(II) ion is a distorted octahedron with a CuN₂O₄ chromophore, constituted by a chelating tmen molecule, and two 2-chlorobenzoate^1? anions coordinated through their carboxylate-O atoms in an asymmetrical bidentate fashion. Complex 2 is also a monomer and consists of an CuN₂O₃ chromophore, in which tmen is coordinated to Cu(II) through its two N atoms in a chelating bidentate fashion, and an aqua-O and the two o-hydroxybenzoate^1? (HSal^1?) anions are coordinated through one of their carboxylate-O atoms in a monodentate mode, forming a square pyramidal structure. Hydrogen bonding interactions especially of O–H…O, N–H…O, and C–H…Cl types interweave monomeric units and stabilize the overall crystal structures in both complexes. Thermal analysis and antibacterial activities of 1 and 2 against various bacterial strains were also investigated.     

Direct determination of the rate constant for the reaction CO + N2O → CO2 + N2

The rate constant for the bimolecular reaction CO + N₂O → CO₂ + N₂ was determined by comparison of calculated infrared emission profiles of CO₂ with those observed in shock-tube experiments in the temperature range 1350–2100 K for CO-N₂O-He-Ar mixtures. The rate constant was found to be k₁ = 3.2 × 10¹¹exp(−85 kJ/RT) cm³ mol⁻¹ s⁻¹.     

Cyclopalladation of N,N,N′,N′-tetramethylisophthalthioamide

Summary N,N,N,N-Tetramethylisophthalthioamide (Hmpt) was cyclopalladated with PdCl₂ in hot dimethylsulphoxide to give [PdCl(mpt)]. The structure was determined by X-ray analysis. The thioamide is metallated at C(2) to act as an S528-01C528-02S tridentate anionic ligand. There is appreciable steric repulsion between the benzene ring H(4, 6) and the dimethylamino groups. The hydrogens and the methyl groups mutually deviate from the coordination plane in opposite directions. The stability of the fused 5,5-membered chelate ring formed by the S528-03C528-04S ligand seems to overcome the steric hindrance. Derivatives were prepared by replacement of the chloride ion with iodide, diethyldithiocarbamate, 4-tert-butylpyridine, or tri-n-butylphosphine, and characterized spectroscopically. The S528-05C528-06S-fused chelate ring was maintained in these derivatives.     

Structural studies of cyclic ureas: 1. Enthalpies of formation of imidazolidin-2-one and N,N′-trimethyleneurea

A thermophysical and thermochemical study has been carried out for crystalline imidazolidin-2-one and N,N′-trimethyleneurea [tetrahydropyrimidin-2(1H)-one]. The thermophysical study was made by differential scanning calorimetry, d.s.c., in the temperature intervals between T = 268 K and their respective melting temperatures. Several solid–solid transitions have been detected in imidazolidin-2-one. The standard (p^° = 0.1 MPa) molar enthalpies of formation, at T = 298.15 K, for crystalline imidazolidin-2-one and N,N′-trimethyleneurea [tetrahydropyrimidin-2(1H)-one], were determined using static-bomb combustion calorimetry. The standard molar enthalpies of sublimation, at T = 298.15 K, for the two compounds were derived from the variation of their vapour pressures, measured by the Knudsen effusion method, with the temperature. These two thermochemical parameters yielded the standard molar enthalpies of formation of the two cyclic urea compounds studied in the gaseous phase at T = 298.15 K. These values are discussed in terms of molecular structural contributions and interpreted on the bases of the “benzo-condensed effect” and of the ring strain of imidazolidin-2-one.     

Complexation of the N,N′,O-donor ligand N-trans-(2′-hydroxycyclohexyl)-2-aminomethylpyridine

The potentially tridentate N,N′,O-donor N-trans-(2′-hydroxycyclohexyl)-2-aminomethylpyridine (1) forms ML₂ complexes with M(II)?=?Cu, Ni, and Zn. X-ray crystal structures of the isostructural Ni(II) and Zn(II) complexes confirm bis-tridentate coordination in significantly distorted octahedral geometries as the all-cis facial isomer. Structural comparisons with the previously reported all-trans facial Cu(II) and cis,cis,trans(N_py) facial Co(III) complexes are presented. Protonation constants for 1 and stability constants with Cu(II), Ni(II), and Zn(II) are reported, with both ML and ML₂ species defined. The trend for ML (log K ₁ values for Cu, Ni, and Zn of 8.3, 6.9, and 5.3, respectively) is conventional. Protonation and stability constants with Cu(II) for N,N-bis(2-pyridylmethyl)amine (2) were also defined. The log K ₁ value measured for 2 of 7.4 is very similar to that found for 1 of 8.3, despite the marked difference in the third donor group; it appears that the third donor of the tridentate ligand generally binds only poorly to Jahn–Teller elongated Cu(II) in solution.     

“Magic” losses of one to five N2 molecules from metastable N+2n clusters

SIMS and FAB of solid N₂ generated large N_2n⁺ clusters (N₄⁺ -N⁺₅₄) which showed three types of metastable decay: (i) loss of a single N₂ molecule, assigned to ordinary (“thermal”) metastability, (ii) nearly total disintegration, assigned to radiationless decay of an electronically excited state, and (iii) “magic” losses of very specific small numbers of N₂ molecules, assigned to N₂(v = 1) vibrational relaxation by use of isotope effects. Average N₂ binding energies are estimated.     

Aminoamidines. 5. Synthesis and acetylation of N,N1,N2-triaryl-substituted β-aminoamidines

Triaryl-substituted -aminoamidines were obtained by the reaction of ,-unsaturated N-arylimidoyl chlorides with arylamines. Acylation of the products gave the products from monosubstitution at the -amino group. Triaryl-substituted -aminoamidines react with phosgene and with oxalyl chloride to form 4-aryliminoperhydropyrimidin-2-ones and 5-aryliminoperhydro-1,4-diazepine-2,3-diones, respectively.For previous communication, see [1].A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan' Scientific Center, Russian Academy of Sciences, 420083 Kazan'. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 11, pp. 2633–2642, November, 1992.     

Synthesis and Crystal Structure of a N,N,N＇-tri（2-hydroxy-5-methylbenzyl）-l,2-ethanediamine

An aminophenol ligand, N,N,N＇-tri（2-hydroxy-5-methylbenzyl）-l,2-ethanediamine, was prepared through the Marmich reaction, and structurally characterized by NMR, IR, MS and single-crystal X-ray diffract...     

Density functional study of Fe2 ?N2

The interaction of two iron atoms with molecular nitrogen was studied by means of density functional techniques. Calculations were of the all-electron type, and both conventional local and gradient-dependent approximate (GDA) models were used. A ground state (GS) of linear structure was found for Fe₂-N₂ with 2S + 1 = 7; whereas a distorted tetrahedral structure, being also a septuplet, was located at 4.0 and 14.3 kcal/mol above the GS, at the local and GDA levels of theory, respectively. The N-N bond is moderately perturbed in the GS, but it is strongly activated in the tetrahedral mode: It has bond orders of 2.6 and 1.5, vibrational frequencies of 2148 and 1496 cm^-1, and equilibrium bond lengths of 1.14 and 1.24 Å, for the linear and tetrahedral geometries, respectively. These values are 3.0, 2359 cm^-1, and 1.095 Å, for free N₂. At GDA level of theory, the Fe₂-N₂ binding energy is 15 kcal/mol, which is bigger than that of Fe-N₂ (9 kcal/mol). The π-back donation, in the linear GS, is of 0.31 electrons, but the total charge transfer, from Fe₂ to N₂, is only 0.05 units. This is relevant in comparison with the tetrahedral mode, where the Fe₂ to N₂ total charge transfer is of 0.45 electrons, yielding a stronger activated N₂ moiety. © 1996 John Wiley & Sons, Inc.     

Synthesis of N‐Aryl‐2‐substituted Tetrahydrobenzimidazoles via Direct N‐Arylation

A series of novel N‐aryl‐2‐substituted tetrahydrobenzimidazoles has been synthesized via direct N‐arylation of 2‐substituted tetrahydrobenzimidazoles, which was accomplished by a medium aryl electrophile, 4‐methylsulfonylfluorobenze, in the presence of 37% KF/Al₂O₃ and 18‐crown‐6 in fair yields under mild reaction conditions. Meanwhile, the hydrogenation of 2‐phenylbenzimidazole was studied.