Behavior of nitrite forms of nitrosylruthenium on extraction and back extraction of heterometalic Ru/Zn complexes with trioctylphosphine oxide

The state of ruthenium in conjugated phases upon extraction of trans-[Ru(¹⁵NO)(¹⁵NO₂)₄(OH)]^2? complex with tri-n-octylphosphine oxide (TOPO) in the presence of Zn²⁺ and subsequent back extraction with H¹⁵NO₃ and NH₃(concd.) solutions was studied by ¹⁵N NMR. Binuclear complexes [Ru(NO)(NO₂)_5?n (μ-NO₂) _n?1(μ-OH)Zn(TOPO) _n ] and [Ru(NO)(NO₂)_4?n (ONO)(μ-NO₂) _n?1(μ-OH)Zn(TOPO) _n ], where n = 2, 3, are predominant forms in extract. Kinetic restrictions for ruthenium extraction with TOPO solution in hexane and its back extraction with aqueous solutions of nitric acid and ammonia are eliminated in the absence of direct coordination of extractant to ruthenium. fac-Dinitronitrosyl forms [Ru(NO)(H₂O)₃(NO₂)₂]⁺, [Ru(NO)(H₂O)₂(NO₂)₂(NO₃)]⁰ (3 and 6 M HNO₃) and [Ru(NO)(H₂O)(NO₂)₂(NO₃)₂]^? (6 M HNO₃) prevail in nitric acid back extracts. Equilibrium constant at ambient temperature (0.05 ± 0.01) was assessed for the coordination of second nitrate ion to nitrosylruthenium dinitronitrato complex. Complex species [Ru(NO)(NO₂)₄(OH)]^2? and [Ru(NO)(NO₂)₃(ONO)(OH)]^2? prevail in ammonia back extract.     

Theoretical study of substituent effects on the acidity of the methyl group: Structure of anions CH2X−

Geometries have been optimized using molecular-orbital calculations (a) with a 4-31G Gaussian basis set for carbanions CH₂X^? where X = H, CH₃, NH₂, OH, F, C?CH, CH?CH₂, CHO, COCH₃, CN, and NO₂; and (b) with an STO -3G basis set for methyl acetate and acetyl deprotonated methyl acetate. All the carbanions containing unsaturated substituents are planar, with a considerable shortening of the C? X bond. Carbanions containing saturated substituents are pyramidal with the out-of-plane angle α increasing with the electronegativity of the substituent. Double-zeta basis set calculations give proton affinities over the range 449 (for CH₃CH₂^?) to 355 kcal/mol (for CH₂NO₂^?), with all unsaturated anions having smaller affinities than saturated anions. The correlation of proton affinities with 1s binding energies, and with charges on both the carbon of the anion and on the acidic proton of the neutral molecule are examined.     

Potential functions of internal rotations in n-mononitroalkanes

Internal rotation is studied in n-mononitroalkanes, CH₃(CH₂) _n NO₂, n ?? 7, with the use of the B3LYP/6-311++G(3df, 3pd) and MP2/6-311++G(3df, 3pd) models. Conformations are investigated, and 36 potential functions (V(??)) for all rotations are found. It is shown that as the hydrocarbon chain becomes longer, the potential functions that describe particular molecular fragments change only negligibly beginning from a certain n. Such dependences of V(??) are presented in the form of generalized functions with averaged coefficients (V(??)_av). The V(??)_av values can be recommended for use in simulations. In molecules with n ?? 2, the phenomenon of ??top interactions?? (??movement interactions??) and the gauche effect (the equality between the total energies of gauche ⁺, gauche ^?, and trans-conformers) are observed.     

The mass spectra of (trimethylstannyl)x methanes: Occurrence of tin-carbon double bonds

The mass spectra of (Me₃Sn)_nCH_4?n, where n varies from 1 to 4, (Me₃Sn)₂CClX, where X equals H, Cl, Br or I, together with some tetraalkyltin compounds and Me₃SnCCl₃, are presented. Comparisons with mass spectra of the silicon analogs¹ show a large number of similarities, including the appearance of allylic ions which require Group IV metal to carbon π-bonding. Multiple rearrangements are observed with the halogenated tin compounds which bring the α-halogen into direct bonding with the tin atom.     

Organolead chemistry : III. 207Pb chemical shifts in some organolead compounds

²⁰⁷Pb chemical shifts are reported for the compounds (CH₃)_4?nPb X_n, where n = 1 · 4, X = 4-FC₆H₄; n = 1, 2, 4, X = CH₃ CC; n = 1, 4, X = CH₂CH; n = 1, X = Cl, CH₃O, CH₃CO₂. A correlation between δ(²⁰⁷Pb) and δ(¹⁹F) for the 4-fluorophenyl derivatives is discussed, and solvent effects on δ(²⁰⁷Pb) for the propynyl derivatives are interpreted in terms of complex formation.     

Distribution of electronic density in n-mononitroalkanes

In the framework of ??quantum theory of atoms in molecule?? (QTAIM) was distribution of electronic density analyzed and inductive effect studied in trans- and gauche-isomers of n-mononitroalkanes CH₃(CH₂) _n NO₂ with n ?? 8. Influence of NO₂ is demonstrated to spread on the four neighboring NO₂ groups. Association of gauche-effect with the electronic density distribution has been given adequate consideration. Definitions were formulated for the standard NO₂ group and perturbed CH₂ groups. It has been suggested the refinements of additive procedures for properties calculation of n-nitroalkanes as well as of big molecules containing the nitroalkane substituents.     

The anomeric effect: Ab-initio studies on molecules of the type X?CH2?O?CH3

The anomeric effect of the functional groups X = C?N, C?CH, COOH, COO^?, O? CH₃, NH₂, and NH⁺₃ has been studied with ab initio techniques. Geometry effects upon rotation around the central C? O bond in X? CH₂? O? CH₃ have been compared in the various compounds. The energy differences between the conformers with a gauche and trans (X? C? O? C) arrangement were calculated at the 6-31G* level in the fully optimized 4-21G geometries. Energy differences calculated at the 4-21G level appeared not to be reliable, especially for the groups X that contain non-sp³ hybridized atoms. The 6-31G* energy differences indicate a normal anomeric effect for X = COO^?, O? CH₃, and NH₂(g⁺) (ca. 13 kJ/mol) and a small anomeric effect for X = COOH, C?N, and C?CH (ca. 6 kJ/mol). For X = NH₂(t) and NH⁺₃ a reverse anomeric effect occurs. These observations are in line with experimental results and evidence is given for a competition among various stereoelectronic interactions that occur at the same anomeric center. Geometry variations can be understood in terms of simple rules associated with anomeric orbital interactions. Trends followed when the group X is varied cannot be related in a straightforward way to the energy differences between the trans and the gauche forms in these compounds. Only the variation in the gauche torsion angle X? C? O? C follows roughly the same trend.     

CH3O(X2E) production from 266 nm photolysis of methyl nitrite and reaction with NO

The CH₃O($\text{X}$²E) radical produced by the 266 nm photolysis of CH₃ONO is characterized by laser-induced fluorescence. Using a flowing gas cell the reaction rate of CH₃O($\text{X}$²E) with NO is measured to be (2.08 ± 0.12) × 10^?11 cm³ s^?1 molecule^?1 based upon disappearance of CH₃O and appearance of HNO detected by laser induced fluorescence. Upper limits for CH₃O reactions with CH₄, CO, N₂O, NH₃, CH₃OH, (CH₃)₃CH and CH₂CHCH₂CH₃ are reported. These reactions are all too slow to measure under our experimental conditions.     

Umsetzungen von Borazinderivaten mit Bis(trimethylsilyl)-acetamid und Lithiumhexamethyldisilazan

Bis-(trimethylsilyl)acetamide (BSA) reacts with borazines [RNBX]₃, R=H,X=F; R=CH₃,X=F; R=C₆H₅,X=F and R=C₆H₅,X=Cl to the corresponding borazines,X=OSi(CH₃)₃. The¹H-NMR signal of the Si(CH)₃-groups of [C₆H₅NBOSi(CH₃)₃]₃ is at abnormally high field. With [CH₃NBCl]₃,BSA forms borazines which contain both Si(CH₃)₃O- and O?C(CH₃)=NSiR₃ groups bonded to the boron atoms. With LiN[Si(CH₃)₃]₂, [CH₃NBCl]₃ forms silylaminoboranes.¹H-NMR, mass spectrometric and analytical data are reported.     

The geometric, energetic, and electronic properties of charged phosphorus-doped silicon clusters, PSi n +/PSi n ? (n?=?1�C8)

Charged phosphorus-doped small silicon clusters, PSi _n ⁺/PSi _n ^? (n?=?1?8), have been investigated using the B3LYP/6-311+G* level Kohn?CSham density functional theory (KS-DFT) method. For comparison, the geometries of neutral PSi _n clusters were also optimized at the same level, though most of them have been previously reported. According to our results, cationic PSi _n ⁺ clusters have ground state structures similar to those of pure silicon clusters Si _n+1, with the exception of n?=?5. For anionic PSi _n ^?, most of the lowest-energy structures are in accord with Wade??s 2N+2 rule for closed polyhedra: PSi₄ ^?, PSi₅ ^?, PSi₆ ^?, and PSi₈ ^?, respectively, favor the trigonal bipyramid, tetragonal bipyramid, pentagonal bipyramid, and tricapped trigonal prism (TTP) structures, corresponding to Wade??s 2N+2 rule with N?=?5, 6, 7, and 9. The structures tend to contract when the cationic species is reduced initially to the neutral species and subsequently to the anionic species, implying a strengthening interaction between atoms within the clusters on one and two electron reductions of the cationic species to the neutral and anionic species, respectively. The relative order of stability of the PSi _n ⁺/PSi _n ^? isomers differs from that of the PSi _n isomers. Cluster stability was also analyzed by adiabatic ionization potentials (AIP), adiabatic electron affinities (AEA), binding energies (BE), second-order energy differences (?₂E), and HOMO-LUMO gap values. The results indicate that PSi₄ ^? and PSi₇ ^? clusters are more stable than their neighboring anionic clusters and would be potential species for further mass spectrometric measurements.     

Synthesis and structure of silver coordination polymer with extended ditopic ligand containing terminal amino groups [Ag(C24H28N2)1.5]NO3

[AgL]NO₃ and [AgL_1.5]NO₃ (I) complexes, where L = NH₂-C₆H₄-C(CH₃)₂-C₆H₄-C(CH₃)₂-C₆H₄-NH₂, were obtained. The structure of compound I was determined. Triclinic crystals, space group P $\bar 1$ , a = 6.259(1) ?, b = 15.663(1) ?, c = 20.653(3) ?, ?? = 71.13(1)°, ?? = 81.66(1)°, ?? = 82.45(1)°, V = 1887.8(3) ?³, ??_calc = 1.208 g/cm³, Z = 2. Ag⁺ ion coordinated to three nitrogen atoms of ligands L has a distorted T-shaped coordination. The structure of I is built of cationic polymeric chains [Ag(L)] _?? ⁺ composed of one bridging ligand L (Ag-N(l) = 2.207(6) ? and Ag-N(2) = 2.221(6) ?, NAgN angle is 160.5(2)°). Second crystallographically nonequivalent centrosymmetrical ligand L pairwise combines the chains to form infinite tapes along direction [010] (Ag(l)-N(3) = 2.529(6)?). Noncoordinated NO ₃ ^? anion (Ag(1)??O(1) = 2.982(6) ?) participates in N-H??O hydrogen bonds as proton acceptor to form 3D supramolecular assembly.     

Theoretical study of substituent effects on electronic and structural properties of 2,4-diamino-5-para-substituted-phenyl-6-ethyl-pyrimidines

Density functional theory (DFT) method at the level of B3LYP with 6?C311G(d) basis set was used to investigate the effects of a variety of substituents (H, NH₂, NMe₂, OCH₃, CH₃, Cl, Br, CN, NO₂) on the electronic and structural properties of 2,4-diamino-5-p-substituted-phenyl-6-ethyl-pyrimidines. The investigation showed that the atomization energy was affected by substitution. Likewise, the molecular orbitals HOMO and LUMO and energy gap ??E were affected by the substituent. Dipole moment was also affected by the introduction of the substituent. On the other hand, the Mulliken charges at only C1??, C2 and N7, were correlated with both MSP and DSP models.     

Jahn-teller effects in the MNDO approximation: structures of the molecular cations of some simple organoberyllium compounds

The MNDO method gives geometries for the molecular cations of organoberyllium compounds of types BeR₂ and HBeR (R = CH₃, CHCH₂, CCH, CN, C₅H₅), of C₄H₄Be and CH₃BeBeH₃ and of the series CH_4?n(BeH)_n (n = 0–4) which have symmetries in precise accord with the predictions of the Jahn-Teller theorem. In the series CH_4?n(BeH)_n and CH_4?n(BeH)_n⁺, the barriers to inversion via a planar intermediate decrease with increasing n, are significantly smaller for the cations than for the neutral molecules, and are zero for CH(BeH)₃⁺ and C(BeH)₄⁺, both of which have their minimum energy when strictly planar at carbon.     

subject index

Two conformers of piperidine interconvert through nitrogen inversion. In this equilibrium, conformers with equatorial N–H appear dominant over those with axial N–H. In this study, substituent (X) effects are investigated on nitrogen inversions, for axially substituted 3-X-piperidines, using ab initio calculated NQR parameters, where X=H, F, Cl, Br, CH₃, CF₃, OH, CHO, COOH, CN, NH₂ and NO₂. These 12 species are in three forms. They may have an axial sp³ N–H (1_X), a planar sp² N–H (2_X), and/or an equatorial sp³ N–H (3_X). The axial minima, 1_X, appear to go through transition states (TS), 2_X, and convert to equatorial minima, 3_X. Ab initio and DFT methods are employed to study these equilibria (1_X (min)⇌2_X(TS)⇌3_X(min)). Energies, structural parameters as well as ²H (²H–N) and ¹⁴N quadrupole coupling constants (χ_2H and χ_14N, respectively) are calculated for 1_X, 2_X and 3_X. The order of χ_2H magnitude appears to be: 2_X>3_X>1_X. The same order is obtained for χ_14N when X=F, Cl, Br, CH₃, CF₃, COOH, CN, NH₂ and NO₂. For X=H, OH and CHO, χ_14N trend changes to: 2_X>1_X>3_X. According to our B3LYP/6-31 g (d,p) and MP2/6-31g(d,p) data, the equilibrium shifts in favor of 1_X over 3_X form is demonstrated, when X is F, Cl, Br, COOH, NO₂, CN or CF₃. On the other hand, equatorial 3_X dominate over axial 1_X when X=H, CH₃, OH and NH₂.     

Fourier transform NMR studies of organometallic compounds. II—synthesis and NMR spectroscopy of propenyl and isopropenyl derivatives of silicon and lead

Isomeric mixtures of compounds Me_nM(CH?CHMe)_4?n (M=Si, Pb; n=0?3) have been prepared and studied, as well as pure Me₃M(CMe?CH₂) and mixtures containing propenyl isopropenyl residues bonded to silicon and lead. ¹H, ¹³C, ²⁹Si and ²⁰⁷Pb NMR data are presented; as previously observed for the corresponding tin compounds, the ²⁹Si and ²⁰⁷Pb shifts for the Me₃MC₃H₅ isomers can be used to calculate the shifts expected for the other isomers; while for lead the agreement is good, calculated and observed values for silicon diverge with decreasing n due, at least in part, to steric factors.     

Adsorption properties and surface chemistry of MgO

The adsorption properties of MgO, which is used as a sorbent and catalyst support, were studied using gas chromatography. The test absorbents used were n-alkanes (which show only nonspecific dispersion interactions when physisorbed on any adsorbent) and adsorbates whose molecules are capable of specific interactions with the surface reactive sites of MgO. Adsorption isotherms were measured for CHCl₃, CH₃NO₂, CH₃CN, (CH₃)₂CO, CH₃COOC₂H₅, and (C₂H₅)₂O on MgO at 50–100°C. Differential molar enthalpy changes (?ΔH), equal to molar heats of adsorption, were determined. For polar adsorbates, contributions from dispersive and specific interactions into ?ΔH were determined. The electron-acceptor and electron-donor abilities of the MgO surface were estimated.     

The rate constants for the reaction of the hydroxyl radical with methyl,n-propyl,and n-butyl nitrites

The kinetics of the reaction of OH radicals with methyl, n-propyl, and n-butyl nitrite have been studied in a discharge flow system under pseudo first-order conditions. The OH radicals were generated by the reaction of H atoms with NO₂ and the concentration of OH; monitored by resonance fluorescence, was followed as a function of time in an excess of each nitrite. Values of k(CH₃ONO) = (0.6 ± 0.09) × 10⁹ dm³ mol^?1 s^?1 k(n – C₃H₇ONO) = (1.39 ± 0.20) × 10⁹ dm³ mol^?1 s^?1, and k(n – C₄H₉ONO) = (2.89 ± 0.43) × 10⁹ dm³ mol^?1 s^?1 at 295 K were obtained. These results agree with previous relative rate measurements from this laboratory but the value for k (CH₃ONO) is a factor of 7 greater than the value obtained by relative rate measurements elsewhere using a different OH source.     

Distortion of the coordination polyhedron in mononuclear copper(II) complexes. Optical absorption and electron spin resonance studies on some five-coordinate copper(II) complexes

The preparation and spectral properties are reported for a series of ten mixed-ligand copper(II) complexes of the form [Cu(A)(B)_n](X), where A is acetylacetonate anion, B represents a mono- or bidentate ligand such as morpholine, piperidine, isonicotinic acid hydrazide, 2,2′-bipyridine, 1,10-phenanthroline and X is variously NO^?₃ or ClO^?₄ anion and n = 1 or 2. The coordination of the anions and ligands has been demonstrated by infrared and electronic spectral methods. Electron spin resonance spectral data show the square-pyramidal five-coordinated arrangement around copper(II) in these complexes. Parameters such as g₆, g_⊥, A₆, A_⊥, 〈g〉 and 〈A〉 calculated from electron spin resonance data in solid and solution state at room temperature as well as frozen solution indicate the presence of the unpaired electron in the d_x2_?y2 or d_z2 orbital. These results are in good agreement with electronic and photoacoustic spectral studies.     

Chemische Effekte des isomeren Überganges von Brom-80m in Pentamminkobalt(III)-und Bisäthylendiaminkobalt(III)-bromiden

Zusammenfassung Die chemischen Effekte des isomeren Überganges von^80mBr wurden bei Temperaturen von–78° C und–196° C an mit^80mBr markierten Proben von [Co(NH₃)₅ X]Br_3.2 nH₂O und [Co(en)₂ X _2']Br_3.1 nH₂O untersucht (X=NH₃, NCS, NO₂, OH₂, ONO, ONO₂, F, Cl, Br, I, undX'=en, NH₃, NCS, Cl, Br). Es zeigte sich, daß die Ligandenausbeute an⁸⁰Br, in den Komplexen mit abnehmender Frequenz des Maximums in der ersten Absorptionsbande des [Co(NH₃)₅ X] und des [Co(en)₂ X _2'] zunimmt. Mit anderen Worten, weniger stabile, Liganden werden leichter von Radiobrom ersetzt als Folge des isomeren Überganges in festen Komplexen.

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Chemical effects of the isomeric transition of^80mBr in pentammincobalt(III) and bisethylenediaminecobalt(III) bromides

The chemical effects of the isomeric transition of^80mBr were investigated at temperatures of–78° C and–196° C with^80mBr-labeled samples of [Co(NH₃)₅ X]Br_3.2 nH₂O and [Co(en)₂ X _2']Br_3.1 nH₂O (X=NH₃, NCS, NO₂, OH₂, ONO, ONO₂, F, Cl, Br, I, andX'=en, NH₃, NCS, Cl, Br). The ligand yield of⁸⁰Br in the complexes was found to increase with the decrease in the frequency of the maximum in the first absorption band of [Co(NH₃)₅ X] and [Co(en)₂ X _2']. In other words, less stable ligands were more easily replaced by radiobromine as a consequence of isomeric transition in solid complexes.

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Mit 1 Abbildung

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Herrn Prof. Dr.E. Broda zum 60. Geburtstag gewidmet.     

Syntheses,characterisation and solid state thermal studies of 1-(2-aminoethyl)piperidine (L), 1-(2-aminoethyl)pyrrolidine (L′) and 4-(2-aminoethyl)morpholine (L″) complexes of nickel(II): X-ray single crystal structure analyses of trans-[NiL2(CH3CN)2](ClO4)2, trans-[NiL2(NCS)2] and trans-[NiL″2(NCS)2]

Reactions of nickel(II) salts with substituted ethane-1,2-diamine where one of the amine nitrogens is a part of a flexible cyclic ring, e.g. 1-(2-aminoethyl)piperidine (L), 1-(2-aminoethyl)pyrrolidine (L′) and 4-(2-aminoethyl)morpholine (L″) produce a number of complexes of the type: (i) Ni(AA)₂X₂ (where X=CF₃CO₂ ⁻, SCN⁻ and NO₂ ⁻; AA represents L/L′/L″); (ii) Ni(AA)₂(CH₃CN)₂X₂ (X=ClO₄ ⁻ and NO₃ ⁻); (iii) Ni(AA)₂(H₂O)₂X₂ (X=CF₃SO₃ ⁻, Cl⁻, Br⁻ and I⁻); and (iv) Ni(AA)₂(H₂O)₄X₂ (X=0.5SO₄ ²⁻, 0.5SeO₄ ²⁻ and CF₃SO₃ ⁻). The complexes possess octahedral geometry. The major complexes upon desolvation retain trans-geometry, some of which are cis with respect to the counter-anion and a few of them are square planar. X-ray single crystal structure analyses of trans-[NiL₂(CH₃CN)₂](ClO₄)₂, trans-[NiL₂(NCS)₂] (violet) and trans-[NiL″₂(NCS)₂] (sky-blue) have been done. The violet and sky-blue thiocyanato species have blue and green coloured isomers, respectively, and these pairs of isomers are proposed to be conformational isomers. Solid state thermal investigation of the complexes has been carried out. The complexes show thermochromism due to deaquation–anation/deaquation reaction/change of conformation. Only [NiL₂](ClO₄)₂, [NiL′₂(CF₃CO₂)₂] and [NiL″₂(NO₂)₂] undergo thermally induced phase transition. The effect of flexible ring size on diamine has been discussed.