Influence of the nature of the lower free orbital of platinum(IV) bipyridyl complexes on the kinetics and the mechanism of electron transfer processes in which they participate

The kinetics of outer-sphere electron transfer reactions with the participation of [PtEn_xbipy_2–xCl₂]²⁺ complexes (x = 0–2) have been studied. The formal potential and the internal barrier of self-exchange reactions with the electron Pt(IV) Pt(III) have been estimated. A correlation has been shown to exist between the parameters of outer-sphere and intramolecular electron transfer.A. I. Gertsen Russian Fedagogical University, Leningrad. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 27, No. 5, pp. 695–698, November–December, 1991. Original article submitted May 20, 1991.     

Nonisothermal deoxygenation of cobalt complexes in free form and attached to aerosil

Thermal deoxygenation under vacuum has been examined for free oxygenated cobalt complexes formed with phenanthroline, histidine, and histamine and also for those attached to aerosil; mass spectrometry has been applied to the products. The free compounds are deoxygenated in accordance with the Roginskii equation f() = (1–)^2/3 in a certain range. Deoxygenation for the grafted complexes is described by an equation for nucleation and one-dimensional growth f() = 1–. The kinetic parameters have been determined.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 23, No. 3, pp. 311–317, May–June, 1987.     

Coordination-sphere dynamics of bisphosphine o-semiquinone complexes of copper(I)

Depending on steric effects of phosphine and o-semiquinone (SQ) ligands bonded to the copper atom, (R₃P)₂CuSQ complexes have either pseudotetrahedral geometry with equivalent phosphine ligands or trigonal-pyramidal with one equatorial and one axial phosphine ligand. In an ESR study of the exchange dynamics of the phosphine ligands in trigonal-pyramidal complexes, the kinetic parameters of the exchange were determined. A model was proposed which explains distortions in the geometry of the complexes by nonvalence interatomic interactions on the periphery of the phosphine and SQ ligands.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 1986–1991, September, 1991.     

Role of the paramagnetic nickel(I) complex in the catalytic dimerization of norbornadiene

In a joint investigation of the kinetic laws of the catalytic cyclodimerization of norbornadiene in the presence of bis-³-allyl complexes of nickel by gas chromatography and ESR, a definite correspondance in the change in the concentrations of norbornadiene, its dimers, and the paramagnetic nickel(I) complex was detected. The absence of an ESR signal in model systems, as well as the substantial differences in the relative amounts of Ni(I) when bis-₃ -allyl nickel complexes of different structure were used, suggests that paramagnetic Ni(I) does not participate as one of the intermediates in the catalytic process.M. V. Lomonosov Moscow Institute of Fine Chemical Technology. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 27, No. 4, pp. 513–516, July–August, 1991. Original article submitted October 16, 1989.     

Determination of the relaxation times and limiting paramagnetic shifts from NMR line shapes

Absract We obtain the relaxation times due to interaction with the paramagnetic center and the limiting paramagnetic shifts for signals from proton groups of amino-acid complexes (L-histidine and -alanine) with rare-earth (Pr³⁺, d³⁺, Ev³⁺, Tm³⁺, Yb³⁺) in aqueous solutions. The thermodynamic and kinetic parameters of complex-formation reactions are estimated in the temperature region 303–363 K. The data are obtained by analyzing the complete NMR line shape using the spin-density-matrix formalism.Published to initiate discussion.Kuban State University, Krasnodar. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 27, No. 6, pp. 745–750, November–December, 1991. Original article submitted March 31, 1986.     

Radical chain mechanism of the homolytic decomposition of organocobalt complexes

The kinetics and mechanism of the homolytic decomposition of some alkylcobalt(III) complexes with a tridentate Schiff base [series (I)] in acidic media have been investigated spectrophotometrically and by analyzing the products, in experiments with free-radical acceptors and with isotope labels.In contrast to the decomposition of other types of organocobalt complexes and generally of-organic derivatives of transition metals, the homolysis stage is irreversible and initiates the chain reaction. The chain propagation is due to the ability of the free radical to detach a hydrogen atom from the tridentate ligand in the initial complex. The chain reaction mechanism and structural factors promoting it are being discussed.A. N. Nesmeyanov Institute of Heteroorganic Compounds, Academy of Sciences of the USSR, Moscow. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 27, No. 3, pp. 293–300, May–June, 1991. Original article submitted March 25, 1991.     

Kinetics of the destruction of cyclic complexes of nickel(III) and their participation in oscillating chemical processes

A spectrophotometric method has been used to study in sulfuric acid solutions the chelate reduction of nickel(III) compounds Ni^IIIL, where L are l4-membered tetraazamacrocyclic ligands with a different number of substitutents (from 0 to 0) and double bonds (from U to 4). Based on the comparison of the kinetic characteristics of the redox reactions of the nickel complexes with data on the participation of such compounds in oscillating chemical reactions in the systems NiLBrO^– ₃-H₂SO₄ it was concluded that a necessary condition for the creation of OCR in this case is, besides the autocatalytic regime of the oxidation of the [NiL]²⁺ complex with bromate, the ability of nickel(III) to undergo rapid reduction (k > 10^–4 sec^–1) by the oxidation of the coordinated macrocyclic ligand.L. V. Pisarzhevskii Institute of Physical Chemistry, Academy of Sciences of Ukrainian SSR, Kiev. Translated from Teoretichesakaya i ÉksperimentaI'naya Khimiya, Vol. 27, No. l pp. 51–55, January–February, 1991. Original article submitted May 29, 1990.     

Preparation and properties of chiral complexes of Cu(II) with (S)-2-[(N-benzylprolyl)amino]benzaldehyde oxime,catalysts of azlactone hydrolysis

Two Cu(II) complexes of (S)-2-[(N-benzylprolyl)amino]benzaldehyde oxime (L) were isolated. The complex Cu[(LH^–1)(Cl)] is green, whereas Cu₂(LH₂)_–2 is red-brown. The structure of these complexes was proved by elemental analysis, IR and UV spectroscopy. The average molecular masses ( ) of the complexes in ethanol were determined by precision ebulliometry. The concentration dependence of the values of these complexes is consistent with the existence of the following equilibria in ethanol: Cu[(LH_–1)(Cl)] + EtOH Cu[(LH_–1)(HOEt)]⁺+Cl⁺ and [Cu₂(LH_–2)₂] + EtOH 2[Cu(LH-_–2)(HOEt)]. The equilibrium constants of these two reactions were determined. Both [Cu(LH_–1)(Cl)] and [Cu₂(LH_–2)₂] catalyze with equal efficiency the hydrolysis of 2-methyl-4-benzyl-5(4H)-oxazolone in aqueous solutions at a given pH. The UV spectra of both complexes in water at similar pH values are identical. Thus, both complexes must be interconvertible in aqueous solutions. Furthermore, the absence of any electrophoretically mobile particles in neutral aqueous buffers is an indication that the complexes [Cu₂(LH^–2)₂] and [Cu(LH^–2)(H₂O)] are the predominant species in solution under these conditions.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2270–2275, October, 1991.     

Homo and heteronuclear complexes of dioxime ligands

The mononuclear fragments [Cu(HDopn)(OH)2]+ and [Cu(HPopn)(OH)2]+, [H2Dopn=3,3-(trimethylene- dinitrilo)-dibutan-2–one dioximate and H2Popn, = 3, 3-(phenylenedinitrilo)-dibutan-2–one dioximate] were used to prepare four binuclear complexes [(OH2)Cu (Dopn)Cu(ditn)]2+, [(OH2)Cu(Dopn)Ni(ditn)(H2O)]2+ (ditn=diethylenetriamine) and [(OH2)Cu(Popn)Cu(L) (H2O)]2+ (L=2,2-bipyridine or 1,10–phenanthroline). Two trinuclear complexes, [{Cu(Popn)(OH2)}2M (H2O)n]2+ (when M=CuII, n=1; M=ZnII, n= 2), have been synthesised and characterised by elemental analyses, f.a.b. mass, i.r., electronic, e.s.r. spectroscopy and variable temperature (5–300K) magnetic susceptibility measurements. A strong antiferromagnetic interaction (J=–545cm–1 to –700cm–1) has been found for the binuclear copper(II) complexes. The X-band e.s.r. spectra of these complexes at 300K and for trinuclear complexes at 120K indicate square-pyramidal geometry for the copper centres with a (dx2–y2)1 ground state. The binuclear complex of copper(II)–nickel(II) centres with antiferromagnetic interaction (J=–107 cm–1) is described, and moderately strong zero-field splitting within the quartet state leads to Kramers doublet, as indicated by X-band e.s.r. spectra of this complex. The trinuclear copper(II) complex with an antiferromagnetic interaction (J= –350cm–1) is also described. The heterometallic trinuclear copper(II)–zinc(II)–copper(II) system shows a very weak interaction (J–1cm–1).     

EPR of copper(II) chloride complexes with diphosphine dioxides

Stepwise formation of copper(ll) chloride complexes with diphosphine dioxides has been studied using paramagnetic resonance. It was found that in complexes with a copper:ligand composition of 11 substituents have little effect on parameters of the anisotropic EPR spectra. The spectra of complexes with a metal:ligand composition of 12 are considerably more sensitive to the introduction of substituents; this is explained by sterically dependent differences in the structure of the complexes. The possibility of trisligand complexes being formed is evidently largely determined by the size of the groups on the phosphorus atoms.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 362–368, February, 1991.     

Thermal Behaviour and Decomposition Kinetics for Two Palladium(II) Complexes with 1-aminopyrene and its Derivative

The thermal decomposition studies for two palladium(II) complexes Pd(apyr)₂Cl₂ and Pd(pmpa)Cl₂ (apyr=1–aminopyrene and pmpa=N–(2–pyridylmethylene)–1–pyrenylamine) were carried out in pure nitrogen using TG-DTG techniques. The non-isothermal kinetic parameters for the two complexes were evaluated employing the method suggested by Málek, esták, Koga et al. Based on the above results, thermal behaviour of the complexes were carefully discussed, which showed that not only the parameters value, but also the decomposition pattern and mechanism for complex 1 are different from complex 2.This revised version was published online in November 2005 with corrections to the Cover Date.     

Application of perturbation theory to estimate inner and outer spherf ligand reactivities

As a mutual ligand reactivity index we proposed the stabilization energy E calculated by perturbation theory. For intermediate complexes from the oxidation reaction of phosphine and arsine with the halogenide Cu(II) we obtain a correlation between the size of E and the rate constant. The electronic properties of the complexes are calculated using the MWH method.Sokolskii Institute for Organic Catalysis and Electrochemistry, Kazakh Academy of Sciences, Alma-Ata. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 27, No. 6, pp. 653–658, November–December, 1991. Original article submitted March 3, 1987.     

Synthesis,spectroscopic and magnetic properties of methoxo- bridged copper(II) complexes with 2-amino-4-methylpyridine as the ligand

Three new methoxo-bridged copper(II) complexes with 2-amino-4- methylpyridine as the ligand have been synthesized and characterized by elemental analyses, FTIR and electronic spectra, and by their magnetic properties. The complexes exhibit strong antiferromagnetic interactions at room temperature. The u.v.-vis spectra exhibits three absorption bands, which can attributed to d–d, L–M and –* transitions. The i.r. spectra indicates Cu2O2 ring vibrations in the 580–530cm–1 range. The magnetic properties of the [Cu2(2-amino-4-methylpyridine)4(O- Me)2](ClO4)2 complex has been investigated in the 5–270K range and a singlet-triplet energy gap (–2J) of 67cm–1 was observed. All complexes in the solid state are e.p.r.-silent and show no triplet spectrum; in fact a weak signal due to a monomeric impurity are observed. Frozen solution e.p.r. spectra suggest that the complexes dissociate when dissolved in DMF or DMSO.     

Comparative quantum-chemical investigation of the CH acidity of some N-methyl-amino derivatives in the gas phase and in solution

The equilibrium configuration of the molecules of three derivatives of N-methylnitrosoamine, N,N-dimethylnitramine, and 1-phenyl-1-triazene and their carbanions were calculated by various semiempircal SCF methods and also in the nonempirical 3–21G⁺ approximation. The optimized geometric parameters of the AM-1 method and the nonempirical 3–21G⁺ calculation agree with each other and with the experimental data better than the geometric parameters calculated by the MINDO/3 method. The most reliable results are obtained by the AM1 method as applied to the gasphase CH acidity of the N-methylamino derivatives. The scheme for the breakdown of the deprotonation energies of the investigated CH acids into components characterizing the individual atoms and bonds was used to analyze the mechanism of internal stabilization of the conjugated carbanions. Comparison of the kinetic CH acidities of the standard hydrocarbons in the basic solution with their deprotonation energies calculated by the AM1 method made it possible to obtain a correlation, the existence of which confirms that there is a single type of mechanism for the stabilization of the carbanions, excluding the solvation effect. The deviation of N-methylamino derivatives from the main line indicates that the solvent has a strong effect on their kinetic CH acidity.Scientific-Production Association, State Institute of Applied Chemistry, Leningrad. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 27, No. 4, pp. 426–437, July–August, 1991. Original article submitted February 25, 1991.     

Transition metal complexes — A new class of catalysts of interfacial alkylation for the asymmetrical synthesis of α-amino acids

A new class of catalysts of interfacial asymmetrical alkylation is suggested for the synthesis of -amino acids — positively charged complexes of the transition metals Cu(II), Ni(II), and Pd(II). These complexes consist of several fragments, by variation of which the structure of the catalysts can readily be modified. The complexes are chiral on account of (S)proline derivatives contained in them as one of the fragments. The catalyst complexes (C) were used in the alkylation of amino acid fragments of Ni(II) complexes of the Schiff base of glycine with N-(2-pyridinecarbonyl)-o-aminobenzophenone (Ni-PBP-Gly) and the Schiff base of alanine with N-(2-pyridinecarbonyl)-o-aminobenzaldehyde (Ni-PBA-Ala) under interfacial conditions. After decomposition of the alkylated complexes, phenylalanine and -methyl-phenylalanine were isolated with yields of 33–87% and optical purity (o.p.) from 3 to 21%, depending on the C used.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 126–134, January, 1991.     

Influence of substituents in the ligand on the properties of macrocyclic complexes of zinc

The synthesis of complexes of zinc with saturated 14-member tetraazamacrocyclic ligands is described; the compounds obtained were characterized by the of elementary analysis and IR spectroscopy. The distribution of electron density in the coordination mode of complexes of zinc with macrocycles differing in number and mutual arrangement of the substituents was investigated by the XES method. The kineties of reactions of replacement of zinc ions by copper ions in complexes with saturated macrocycles and an analogous noncyclic ligand was investigated; the influence of substituents on the kinetic parameters of these reactions was established.Translated from Teoreticheskaya i Éxperimental'naya Khimiya, Vol. 21, No. 4, pp. 424–431, July–August, 1985.     

2–Hydroxy–1,3–propylene bis (oxamato)–bridged new NiIICuIINiII trinuclear complexes with an S = 3/2 high-spin ground state: synthesis and magnetism

Four new heterotrinuclear complexes have been synthesized and characterized, namely {[Ni(L)2]2[Cu(pbaOH)]}(ClO4)2, where pbaOH denotes 2–hydroxy–1,3–propylenebis(oxamato) and L = 1,10–phenanthroline (phen), 5-nitro-1,10-phenanthroline (NO2–phen), 2,2–bipyridyl (bpy) and 4,4–dimethyl–2,2–bipyridyl (Me2bpy). The temperature dependence of the magnetic susceptibility of {[Ni(phen)2]2[Cu(pbaOH ]}(ClO4)2·H2O has been studied in the 4–300 K range, giving an exchange integral J = –94 cm– . The MT versus T plot exhibits a minimum at ca. 93 K, characteristic of this type of coupled polymetallic complex with an irregular spin-state structure.     

Absorption and fluorescence of complexes of compounds of anthracene carboxylic acids with metal ions in liquid solutions

We have studied the absorption and fluorescent properties of complexes formed by compounds of anthracene-9-carboxylic acid with metal cations in dimethyl sulfoxide and ethanol. The composition and stability of these complexes has been determined. It is shown that when lanthanide ions are added (Ln³⁺) 21 complexes are formed predominantly, i.e., RCOO^– Ln^{3+ –}OOCR, while with Cd²⁺ the complexes are mainly 11, i.e., RCOO^– Cd²⁺. We have considered the principal mechanisms for the deactivation of excitation in complexes based on the RE ions (dipole-dipole energy transfer and electron transfer). The interactions were shown to be inner-sphere in character in the ion triplets, and outer-sphere in the ion pairs. The metal-ligand distance in the 21 complexes is estimated to be 0.5–0.6 nm.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 6, pp. 673–682, November–December, 1989.In conclusion the authors wish to thank A. S. Cherkasov for synthesizing and making available the ACA and for discussing the results of the investigation.     

Electronic and ESR spectroscopic study of thiocyanate-containing coordination compounds of titanium(III) in alcohol solutions

In an investigation of electronic and ESR spectra, it has been established that titanium(III) with the thiocyanate ion (in ethanol) forms distorted tetrahedral and octahedral complexes. The tetrahedral compounds, which are hydroxo complexes of titanium(III) that contain one hydroxyl group and three thiocyanate ions in the coordination sphere, give signals in the ESR spectra with g_o=1.960, A_o=15.0·10^–4 cm^–1 g=1.958, A ^Ti =26.4·10^–4cm^–1, g= 1.691, A^Ti=9.0·10^–4 cm^–1. In the ESR spectra of liquid solutions, additional splitting on the nitrogen atoms is manifested(A _o ^N =2.2·10^–4 cm^–1), which indicates bonding of thiocyanate ions through the nitrogen atom. The pseudo-octahedral complexes of titanium(III), containing from two to six thiocyanate ions in the coordination sphere, are characterized by d-d absorption bands in the 520–590 nm region; and at 77°K, they give anisotropic ESR signals. On the basis of the temperature dependences of the equilibrium constants for the reaction of conversion of the tetrahedral complexes to the octahedral complexes, and also the lifetimes of the tetrahedral complexes, values have been estimated for the heat of reaction (H=26.8 kJ/mole) and the entropy change (S=–1.66 kJ/mole·°K) of the equilibrium process, and also the activation energy for the reaction of titanium(III) thiocyanate formation (E=37 kJ/mole).Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 21, No. 5, pp. 560–567, September–October, 1985.     

Effect of axial anions on the thermal stability of square pyramidal manganese(III) complexes

Summary The effect of the axial anion on the thermal behaviour of square pyramidal Mn^III complexes of [Mn(SB)X] (where SB=tetradentate dibasic Schiff base; X=OAc^–, SCN^–, Cl^–, Br^– or I^–) has been studied. A correlation has been made between the thermal stabilities of the complexes and the electronegativities () of the axial donor atoms. Other solid state phenomena (nature of interaction of the solvent of crystallization and polymorphic transformation) were also studied for the acetato and isothiocyanato complexes.