The N—H and O—H bond dissociation energies in 4-hydroxydiphenylamine and its phenoxyl and aminyl radicals

The N—H and O—H bond dissociation energies in 4-hydroxydiphenylamine Ph—NH—C₆H₄—OH (D _NH= 353.4, D _OH=339.3 kJ mol^–1) and its semiquinone radicals D _NH(Ph—NH—C₆H₄—O^·) = 273.6, D _OH(Ph—N^·—C₆H₄—OH) = 259.5 kJ mol^–1 were first estimated using the parabolic model and experimental data (rate constants) on two elementary reactions with participation of N-phenyl-1,4-benzoquinonemonoimine (2). One of the reactions, namely, that of 2 with aromatic amines, was studied in this work using a specially developed method.     

Sb–C Bond Cleavage Reaction on a Triruthenium Cluster and the Formation of a Bridging Phenylacyl Unit

Syntheses and single crystal X-ray structures of an open triruthenium acyl carbonyl cluster [(C₆H₅)₂SbRu₃(COC₆H₅)(CO)₁₀] (1) and a simple triruthenium Ru₃(CO)₉[(C₆H₅)₂PCH₂P(C₆H₅)₂]Sb(C₆H₅)₃ (2) are reported. Formation of compound (1) at room temperature from [Ru₃(CO)₁₂] and [Sb(C₆H₅)₃] is unique, a similar reaction with Ru₃(CO)₁₀[(C₆H₅)₂PCH₂P(C₆H₅)₂] under identical conditions results in compound (2), with Sb(C₆H₅)₃ occupying an equatorial site. IR, ¹H, ¹³C NMR spectra of the compounds are reported. The X-ray crystal structure of (1) consist of 2 crystallography distinct molecules and shows Ru–Sb distances in the range: 2.6361(6)–2.6273(7) Å and Ru–Ru distances in the range: 2.8236(7)–2.9855(7) Å. Ru–O distances in the bridging carbonyl are: 2.137(4), 2.158(4) Å. The Sb–Ru–Ru angles in the two molecules of the asymmetric unit are in the range of 73.78(2)–77.52° indicating the puckered nature. Compound (2) has bond parameters comparable to those of Ru₃(CO)₁₀[(C₆H₅)₂PCH₂P(C₆H₅)₂]. The present study shows for the first time that the cleaving of Sb–C bond at room temperature is possible under non-ionic conditions, though there have been many instances of P–C and As–C bond cleavages reported previously.     

Ruthenium-azoimine-chloranilates Synthesis,Spectra and Electrochemistry of Ruthenium(II)-1-alkyl-2-(arylazo)imidazole-chloranilate Complexes

Ag⁺-assisted dechlorination of blue cis-trans-cis Ru(R-aai-R′)₂Cl₂ followed by the reaction with chloranilic acid (H₂CA) in the presence of Et₃N, gives a neutral mononuclear violet complex [Ru(R-aai-R′)₂(CA)]. [R-aai-R′=p-R-C₆H₄—N=N—C₃H₂—NN, abbreviated as an N,N′ chelator where N(imidazole) and N(azo) represent N and N′, respectively; R = H (a), OMe (b), NO₂ (c) and R′= Me (4), Et(5), Bz(6)]. All the complexes exhibit strong intense MLCT transitions in the visible region and weak broad bands at higher wavelength (>700 nm). Visible transitions (580–595 nm) show a negative solvatochromic effect. The cyclic voltammograms show two quasireversible to irreversible couples positive to SCE and are due to CA⁻/CA²⁻ (1.2–1.35 V) and Ru(III)/Ru(II) (1.6–1.8 V) redox processes. Three couples, negative to SCE, are assigned to CA²⁻/CA³⁻ (−0.2 to −0.3 V), and azo reductions (−0.5 to −0.7, −0.8 to −0.9 V) of the chelated R-aai-R′.     

[N(PPh3)2]2[{Au3Ag2(C2Ph)6} {Au3Cu2(Cu2Ph)6}]: Co-crystallized pentanuclear bimetallic gold-silver and gold-copper clusters

The X-ray structural study of the reaction product of equimolar amounts of [Au₃Cu₂(C₂Ph)₆]. [{Au(C₂Ph)} _n ], and [Ag(C₂Ph)} _n ] revealed two bimetallic anionic [N(PPh₃)₂] + [Au₃Ag₂(C₂Ph)₆]^– and [N(PPh₃)₂]⁺[Au₃Cu₂ (C₂ Pg)₆] — clusters co-crystallized in one asymmetric unit. Each cluster has trigonal bipyramidal geometry with three gold atoms occupying equatorial planes and two silver or copper atoms in the apical positions. Our earlier conclusion based upon spectroscopic characterization describing the product of be above reaction as trimetallic cluster containing three coinage-metals with an overall composition [Au₃CuAg(C₂Ph)₆]^–, was erroneous.Presented at the 210th ACS Meeting, August 19–24, 1995, Chicago, Illinois.     

Syntheses,crystal structures and magnetic properties of two cyano-bridged two-dimensional assemblies [Fe(salpn)]2 [Fe(CN)5NO] and [Fe(salpn)]2[Ni(CN)4]

Two cyano-bridged assemblies, [Fe^III(salpn)]₂[Fe^II(CN)₅NO] (1) and [Fe^III (salpn)]₂[Ni^II(CN)₄] (2) [salpn = N, N-1,2-propylenebis(salicylideneiminato)dianion], have been prepared and structurally and magnetically characterized. In each complex, [Fe(CN)₅NO]^2– or [Ni(CN)₄]^2– coordinates with four [Fe(salpn)]⁺ cations using four co-planar CN^– ligands, whereas each [Fe(salpn)]⁺ links two [Fe(CN)₅NO]^2– or [Ni(CN)₄]^2– ions in the trans form, which results in a two-dimensional (2D) network consisting of pillow-like octanuclear [—M^II—CN—Fe^III—NC—]₄ units (M = Fe or Ni). In complex (1), the NO group of [Fe(CN)₅NO]^2– remains monodentate and the bond angle of Fe^II—N—O is 180.0°. The variable temperature magnetic susceptibilities, measured in the 5–300 K range, show weak intralayer antiferromagnetic interactions in both complexes with the intramolecular iron(III)iron(III) exchange integrals of –0.017 cm^–1 for (1) and –0.020 cm^–1 for (2), respectively.     

Synthesis,crystal structure and magnetic properties of a two-dimensional mixed-valence assembly [Fe(salen)]2[Fe(CN)5NO]

A cyanide-bridged Fe^III–Fe^II mixed-valence assembly, [Fe^III(salen)]₂[Fe^II(CN)₅NO] [salen = N,N-ethylenebis(salicylideneiminato)dianion], prepared by slow diffusion of an aqueous solution of Na₂[Fe(CN)₅NO] · 2H₂O and a MeOH solution of [Fe(salen)NO₃] in an H tube, has been characterized by X-ray structure analysis, i.r. spectra and magnetic measurements. The product assumes a two-dimensional network structure consisting of pillow-like octanuclear [—Fe^II—CN—Fe^III—NC—]₄ units with dimensions: Fe^II—C = 1.942(7) Å, C—N = 1.139(9) Å, Fe^III—N = 2.173(6) Å, Fe^II—C—N = 178.0(6)°, Fe^III—N—C = 163.4(6)°. The Fe^II—N—O bond angle is linear (180.0°). The variable temperature magnetic susceptibility, measured in the 4.8–300 K range, indicates the presence of a weak intralayer antiferromagnetic interaction and gives an Fe^III–Fe^III exchange integral of –0.033 cm^–1.     

Ab initio investigation of the synthesis of (3-(2,3,4,5-tetramethylcyclopentadienyl)propoxy)titanium dichloride

The two-step synthesis of [η⁵:η¹-C₅Me₄(CH₂)₃O]TiCl₂ from [C₅Me₄(CH₂)₃OMe]TiCl₃ is investigated through molecular orbital calculations. Results of ab initio, restricted Hartree–Fock calculations at the 6-311G(d) basis set level are reported for the reactants, products, and an intermediate, [C₅Me₄(CH₂)₃OMe]TiCl₂(CHPPh₃). These results provide insight into the mechanism of the second reaction, which is found to be a charge-controlled intermolecular nucleophilic attack. The nature of the titanium–ylid bond in the intermediate complex is also reported.     

Electrophilic substitution in benzo[b]thieno[2,3-c]pyridines. Nitration

A study was carried out on the nitration of substituted benzo[b]thieno[2,3-c]pyridines. Depending on the conditions, either one nitro group is introduced at C₍₆₎ or two nitro groups are introduced at C₍₆₎ and C₍₈₎. If C₍₆₎ is blocked, a mixture of products is formed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 706–709, May, 1993.     

Reactions of azinium cations. 6. N(1)-alkyl-1,2,4-triazinium salts. Reactions with indoles — The first case of the double addition of nucleophiles to a triazine ring

N₍₁₎-Alkyl-3-morpholino-1,2,4-triazinium salts and N₍₁₎-alkyl-3-pyrrolidino-1,2,4-triazinium salts were synthesized. The structures of these salts were established by ¹³C NMR spectroscopy. 1,2,4-Triazinium cations add indoles at C₍₅₎ and C₍₆₎ thereby displaying properties characteristic for 1,4-diazinium salts.For communication 5, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1535–1543, November, 1986.     

UV–visible spectrum of the phenyl radical and kinetics of its reaction with NO in the gas phase

Pulse radiolysis transient UV–visible absorption spectroscopy was used to study the UV–visible absorption spectrum (225–575 nm) of the phenyl radical, C₆H₅(), and kinetics of its reaction with NO. Phenyl radicals have a strong broad featureless absorption in the region of 225–340 nm. In the presence of NO phenyl radicals are converted into nitrosobenzene. The phenyl radical spectrum was measured relative to that of nitrosobenzene. Based upon σ(C₆H₅NO)_{270 nm}=3.82×10⁻¹⁷ cm² molecule⁻¹ we derive an absorption cross-section for phenyl radicals at 250 nm, σ(C₆H₅())_{250 nm}=(2.75±0.58)×10⁻¹⁷ cm² molecule⁻¹. At 295 K in 200–1000 mbar of Ar diluent k(C₆H₅()+NO)=(2.09±0.15)×10⁻¹¹ cm³ molecule⁻¹ s⁻¹.     

Reduction of nitrosoarene ligands in binuclear palladium(ii) complexes

Reduction of the binuclear Pd^II complexes Pd₂(OCOR)₂(o-CH₂C₆H₄—NO)₂ (1) and Pd₂(OCOR)₂(o-PhN—C₆H₄—NO)₂ (2) (where R = Me, CF₃, Bu^t, or Ph) by sodium borohydride, an ethanolic solution of KOH, or molecular hydrogen was examined. The first stage of reduction was demonstrated to afford metallic palladium and aromatic amines, viz., o-toluidine o-Me—C₆H₄—NH₂ from complex 1 and aniline Ph—NH₂ from complex 2. The reactions with molecular hydrogen involve deeper stages to yield cyclic ketones (o-methylcyclohexanone and cyclohexanone) and then cycloalkanes (methylcyclohexane and cyclohexane, respectively). The latter reactions are accompanied by elimination of N₂. The mechanism of reduction of complexes 1 and 2 with molecular hydrogen was proposed.     

Kinetics and mechanism of pentacyanohydroxoferrate(III) formation from mono(aminocarboxylato)iron(III) complexes

Summary The kinetics and mechanism of the system: [FeL(OH)]^2–n + 5 CN^– [Fe(CN)₅(OH)]^3– + L^n–, where L=DTPA or HEDTA, have been investigated at pH= 10.5±0.2, I=0.25 M and t=25±0.1 C.As in the reaction of [FeEDTA(OH)]^2–, the formation of [Fe(CN)₅(OH)]^3– through the formation of mixed ligand complex intermediates of the type [FeL(OH)(CN)_x]^2–n–x, is proposed. The reactions were found to consist of three observable stages. The first involves the formation of [Fe(CN)₅(OH)]^3–, the second is the conversion of [Fe(CN)₅(OH)]^3– into [Fe(CN)₆]^3– and the third is the reduction of [Fe(CN)₆]^3– to [Fe(CN)₆]^4– by oxidation of L^n– The first reaction exhibits a variable order dependence on the concentration of cyanide, ranging from one at high cyanide concentration to three at low concentration. The transition between [FeL(OH)]^2–n and [Fe(CN)₅(OH)]^3– is kinetically controlled by the presence of four cyanide ions around the central iron atom in the rate determining step. The second reaction shows first order dependence on the concentration of [Fe(CN)₅(OH)]^3– as well as on cyanide, while the third reaction follows overall second order kinetics; first order each in [Fe(CN)₆]^3– and L^n–, released in the reaction. The reaction rate is highly dependent on hydroxide ion concentration.The reverse reaction between [Fe(CN)₅(OH)]^3– and L^n– showed an inverse first order dependence on cyanide concentration along with first order dependence each on [Fe(CN)_5– (OH)]^3– and L^n–. A five step mechanism is proposed for the first stage of the above two systems.     

A Nonempirical Quantum-Chemical Study and Natural Bond Orbital Analysis of C6H5XCY3 Species (X = SO or SO2, Y = H or F)

The potential functions of internal rotation about the C² _sp—S bonds for C₆H₅XCY₃ species (X = SO or SO₂, Y = H or F) have been obtained at the MP2 (full)/6-31+G(d) level of ab initio theory. It is found that the spatial structures with the plane of C² _sp—S—C³ _sp bonds, which is near perpendicular to the benzene ring plane, are the energy-favourable conformations. The values of the rotational barrier about the C² _sp—S bond are equal to (kJ/mole): 21.2 (C₆H₅SOCH₃), 29.0 (C₆H₅SOCF₃), 20.4 (C₆H₅SO₂CH₃), and 28.2 (C₆H₅SO₂CF₃). On the basis of the Natural Bond Orbital (NBO) analysis results, it has been revealed that the double S=O bond is a strongly polarized covalent -bond, whereas -bond electrons practically are localized on the oxygen atom. The S=O bond order for aromatic sulfoxides and sulphones is mainly caused by hyperconjugational interactions according to the LP(O) ^*(S—C_ipso) and LP(O) ^*(S—C _Y ) mechanisms. In sulphones there is also the additional mechanism of hyperconjugational interactions such as LP(O^{1 *}(S—O²) and LP(O²) ^*(S—O¹). With the replacement of one hydrogen atom on the —XCY₃ group, the charge loss of the unsubstituted benzene molecule increases: —SOCH₃ < —SO₂CH₃ < — SOCF₃ < —SO₂CF₃. The substitution of the —CH₃ group for the —CF₃ group weakly influences the charge value on the sulfur atom but effects the acceptor characteristics of the substituent to a greater extent than the variation of the sulfur atom coordination.     

Theoretical studies upon the electronic structures and spectroscopic properties for a series of luminescent terpyridyl platinum(II) phenylacetylide complexes

A comprehensive calculations were carried out to get a deep insight into the ground- and excited-state electronic structures and the spectroscopic properties for a series of [Pt(4-X–trpy)CCC₆H₄R]⁺ complexes (trpy = 2,2′,6′,2″-terpyridine; X = H, R = NO₂ (1), Cl (2), C₆H₅ (3) and CH₃ (4); R = Cl, X = CH₃ (5) and C₆H₅ (6)). MP2 (second-order Møller–Plesset perturbation) and CIS (single-excitation configuration interaction) methods were employed to optimize the structures of 1–6 in the ground and excited states, respectively. The investigation showed that substituted phenylacetylide and trpy ligands only give rise to a small variation in geometrical structures but lead to a sizable difference in the electronic structures for 1–6 in the ground and excited states. The introduction of electron-rich groups into the phenylacetylide and/or terpyridyl ligands produces two different low-lying absorptions for 1 and 2–6, i.e., Pt(5d) → π^*(trpy) metal-to-ligand charge transfer (MLCT) mixed with π → π^*(CCPh) intraligand charge transfer (ILCT) for 1 and Pt(5d)/π(CCPh) → π^*(trpy) charge transfer (MLCT and LLCT) for 2–6. Remarkable electronic resonance on the whole Pt–CCPh–NO₂ moiety for 1 may be responsible for the difference. Solvatochromism calculation revealed that only LLCT/MLCT transitions showed the solvent dependence, consistent with the experimental observations.     

Tin(IV) complexes ofSchiff bases derived from salicylaldehyde and aminoalcohols

11 and 12 molar reactions of tin(IV) chloride with theSchiff bases, HO–C₆H₄CHNROH [where R=–(CH₂)₂–, –CH₂–, –CH(CH₃)–, –(CH₂)₃–, and –CH(C₂H₅)CH₂–] have been studied in different stoichiometric ratios and derivatives of the type SnCl₄(SBH₂) and SnCl₄(SBH₂)₂ (whereSBH₂ represents theSchiff base molecule) have been isolated. These have been characterised by elemental analysis, conductivity measurements and I.R. spectral studies.     

Synthesis, structure and DNA binding studies of mononuclear copper(II) complexes with mixed donor macroacyclic ligands, 2,6-bis({N-[2&3-(phenylselenato)alkyl]}benzimidoyl)-4-methylphenol

Two new phenol based macroacyclic Schiff base ligands, 2,6-bis({N-[2-(phenylselenato)ethyl]}benzimidoyl)-4-methylphenol (bpebmpH, 1) and 2,6-bis({N-[3-(phenylselenato)propyl]}benzimidoyl)-4-methylphenol (bppbmpH, 2) of the Se₂N₂O type have been prepared by the condensation of 4-methyl-2,6-dibenzoylphenol (mdbpH) with the appropriate (for specific reactions) phenylselenato(alkyl)amine. These ligands with Cu(II) acetate monohydrate in a 2:1 molar ratio in methanol form complexes of the composition [(C₆H₂(O)(CH₃){(C₆H₅)CN(CH₂)_nSe(C₆H₅)}{(C₆H₅)CO}₂Cu] (3 (n = 2), 4 (n = 3)) with the loss of phenylselenato(alkyl)amine and acetic acid. In both these complexes, one arm of the ligand molecule undergoes hydrolysis, and links with Cu(II) in a bidentate (NO) fashion, as confirmed by single crystal X-ray crystallography of complex 3. The selenium atoms do not form part of the copper(II) distorted square planar coordination sphere which has a trans-CuN₂O₂ core. The average Cu–N and Cu–O distances are, respectively, 1.973(3) and 1.898(2) Å. The N–Cu–N and O–Cu–O angles are, respectively, 167.4(11)° and 164.5(12)°. The compounds 1–4 have been characterized by elemental analysis, conductivity measurements, mass spectrometry, IR, electronic, ¹H and ⁷⁷Se{¹H} NMR spectroscopy and cyclic voltammetry. The interaction of complex 3 with calf thymus DNA has been investigated by a spectrophotometric method and cyclic voltammetry.     

Magnetische Untersuchungen an Komplexen von La(III), Pr(III) und Nd(III) mitSchiffschen Basen

Specific magnetic susceptibilities (_s) of several newly synthesized chelates of some of the lanthanons [La(III), Pr(III) and Nd(III)] are reported. These derivatives are of the general type,Ln(O-i-C₃H₇)_3–n (C₆H₅CHNRO) _n [where,Ln=La(III), Pr(III) or Nd(III);n=1 or 2 and R=CH₂CH₂, CH₂CHCH₃ or C₆H₄] and have been prepared by the reaction of the alkoxides of the lanthanons withSchiff bases such as benzylidene-2-hydroxyethylamine (C₆H₅CHNCH₂CH₂OH), benzylidene-2-hydroxy-n-propylamine (C₆H₅CHNCH₂CHOHCH₃) and benzylidene-o-aminophenol (C₆H₅CHNC₆H₄OH) in different molar relations in dry benzene.The resulting crystalline derivatives are non-volatile, light to deep yellow or blackish in colour. These tend to polymerize on keeping as shown by their insoluble nature and higher melting points, the polymerisation possibly occurring by the intermolecular coordination through oxygen atoms as reported earlier¹.UsingGouy method², the bis-isopropoxy mono-Schiff base and mono-isopropoxy bis-Schiff base complexes of La(III) have been shown to be diamagnetic, with _s values being in the range of –0.32 to –0.45×10^–6 and –0.39 to –0.55×10^–6 c.g.s. units at 305 K respectively.In the remaining derivatives, Pr(O-i-C₃H₇)_3–n (C₆H₅CH NRO) _n and Nd(O-i-C₃H₇)_3–n (C₆H₅CHNRO) _n (where,n=1 or 2 and R=CH₂CH₂, CH₂CHCH₃ or C₆H₄) the magnetic moment values range between 3.25 to 3.32 and 3.30 to 3.33 _B respectively indicating their paramagnetic nature.     

1,10-Phenanthrolinium hydrogensquarate monohydrate—A non-centrosymmetric structure from two non-chiral agents

Four different dimethyltin(IV) complexes of Schiff bases derived from 2-amino-3-hydroxypyridine and different substituted salicylaldehydes have been synthesized. The compounds, with the general formula [Me₂Sn(2-OArCHNC₅H₃NO)], where Ar = –C₆H₃(5-CH₃) [Me₂SnL¹], –C₆H₃(5-NO₂) [Me₂SnL²], –C₆H₂(3,5-Cl₂) [Me₂SnL³], and –C₆H₂(3,5-I₂) [Me₂SnL⁴], were characterized by IR, NMR (¹H and ¹³C), mass spectroscopy and elemental analysis. Me₂SnL³ was also characterized by X-ray diffraction analysis and shows a fivefold C₂NO₂ coordination with distorted square pyramidal geometry. H₃C–Sn–CH₃ angles in the complexes were calculated using Lockhart's equations with the ¹J(^117/119Sn–¹³C) and ²J(^117/119Sn–¹H) values (from the ¹H-NMR and ¹³C-NMR spectra). The in vitro antibacterial and antifungal activities of dimethyltin(IV) complexes were also investigated.     

The structure of karatavic acid

Conclusions Karatavic acid has been isolated from the resin of the roots ofFerula karatavica Rgl. et Schmalh; this is an ether of umbelliferone and a hydroxy acid C₁₅H₂₄O₃ probably having the humulane type of hydrocarbon skeleton. Two possible structural formulas—(I) and (II)—have been proposed for karatavic acid.Khimiya Prirodnykh Soedinenii, Vol. 4, No. 5, pp. 283–287, 1968     

Feasibility study for the production of 32 P-labeled diphosphonic acids by neutron irradiation and radiochemical separation

Two simple diphosphonates, CH₆P₂ O₆(MDP) and C₂ H₈ P₂ O₇ (HEDP),have been irradiated with neutrons to produce the corresponding ³²P-labeled compounds. After irradiation for 0.5–5 hours in a thermalneutron flux of 4.2 . 10¹⁶ n . m ^—2 s^—1 the irradiated compounds were dissolved and fractionated using a SephadexG10 column. The separated fractions were identified using planar paper chromatographyand autoradiography. The labeling yield was ca 35% for each of the compounds,and the specific activity attainable ranged up to 4.8 GBq . mol ^—1 . For practical applications, the labeled diphosphonates have to bepurified further.