Synthesis and crystal structure of bis(di-n-butyldithiocarbamato)(1,10-phenanthroline)cadmium(II)

A new mixed-ligand complex, Cd(S₂CN(C₄H₉)₂)₂Phen, is synthesized and investigated by thermal, element, and IR analyses and by diffractometry of polycrystals (DRON-3M, CuK_α radiation, Ni filter). The crystal structure was determined on a CAD-4 Enraf-Nonius automatic diffractometer (MoK_α radiation, θ from 1.5 to 25?, 2325 nonzero independent reflections, 190 refined parameters, R = 0.036 for I > 2Σ(I)). Crystal data for C₃₀H₄₄CdN₄S₄ : a = 15.592(3), b = 22.724(5), c = 9.922(2) å, space group Pbcn, V = 3515.5(12) å₃, Z = 4, M = 701.33, d_calc = 1.325 g/cm³. The structure involves monomeric molecules in which the cadmium atom has a distorted octahedral environment.     

Crystal structure of platinum(II) chloro(1,1,1-trifluoro-4-imino-2-pentanononate(hydrate)) [PtC1(ktf)H<Subscript>2</Subscript>O]

This paper reports on our study of the mixed-ligand Β-iminoketonate complex [PtCl(ktf)H₂O] including l,l,l-trifluoro-4-imino-2-pentanone as a ligand. An X-ray diffraction analysis was performed on a CAD-4 diffractometer (MoK_α radiation, Ω/2θ scan mode). Crystal data of PtClF₃O₂NC₅H₇: a =26.264(5), b =4.750(1), c =15.955(3) å, Β =108.16(3)?, V = 1891.3å₃, space group C2/c, Z = 8, d_calc = 2.82 g/cm³. The Pt atom has a distorted square planar environment. The Pt-Cl, Pt-O(H₂O), Pt-N, and Pt-O bonds are 2.29, 2.07, 1.97, and 1.98 å in length, respectively. The chelate angle is 93.7?. The environment of Pt is completed to pyramidal due to interactions with the C_α atom of the neighboring molecule at a distance of 3.57 å. The compound has a molecular structure. The molecules of the complex are stacked along the Y direction.     

Photoelectron spectroscopy of some thiocyanates,isocyanates and isothiocyanates

Photoelectron spectra of some thiocyanates (RSCN, R = CH₃, C₂H₅, n-C₄H₉), isocyanates (RNCO, R = C₂H₅, n-C₄H₉) and isothiocyanates (RNCS, R = C₂H₅, n-C₄H₉) have been measured, to study interactions between nonbonding and π orbitals, mainly localized on the SCN, NCO or NCS fragments. The spectral interpretation of CH₃SCN is based on semiempirical CNDO/S calculations, sum-rule considerations, and intensity differences between He(I) and HE(II) spectra. For the larger molecules, comparison of the spectra is used as an aid in the interpretation. In a number of aromatic isocyanates (o?, m?, p-tolylisocyanate and m?, p-chlorophenylisocyanate), interactions between the isocyanate group and the highest occupied π and σ orbitals of the phenyl ring are studied. Spectra are assigned on the basis of semiempirical INDO/S calculations.     

Studies on the Formation of β-Cyclodextrin/Alkylcobaloxime Inclusion Complexes by Using NMR Methods

Abstract

It has been established that alkylcobaloxime(R=i-C₄H₉, n-C₄H₉, n-C_sH₁₁, c-C₆H₁₁, PhCH₂) and β-cyclodextrin form a kind of 1: 1 inclusion complexes in aqueous solution by ¹H NMR spectroscopy. Ka and ?ΔG^θ were calculated according to chemical shift changes of different probe protons. The stability constant(Ka) has been found increasing in the order: PhCH₂ > n-C₅H₁₁ > c-C₆H₁₁ > i-C₄H₉ > n-C₄H₉.     

Hartree–Fock and density functional theory study of remote substituent effects on heterolytic Fe―C bond energies of p‐G‐C6H4CH2Fe(CO)2(η5‐C5H5) and p‐G‐C6H4(H)(CN)CFe(CO)2(η5‐C5H5)

Knowledge of the strength of the metal–ligand bond breaking and formation is fundamental for an understanding of the thermodynamics underlying many important stoichiometric and catalytic organometallic reactions. Quantum chemical calculations at different levels of theory have been used to investigate heterolytic Fe―C bond energies of para‐substituted benzyldicarbonyl(η⁵‐cyclopentadienyl)iron, p‐G‐C₆H₄CH₂Fp [1, G = NO₂, CN, COMe, CO₂Me, CF₃, Br, Cl, F, H, Me, MeO, NMe₂; Fp = (η⁵‐C₅H₅)(CO)₂Fe], and para‐substituted α‐cyanobenzyldicarbonyl(η⁵‐cyclopentadienyl)iron, p‐G‐PANFp [2, PAN = C₆H₄CH(CN)]. The results show that BP86 and TPSSTPSS can provide the best price/performance ratio and more accurate predictions in the study of ΔH_het(Fe―C)'s. The good linear correlations [r = 0.98 (g, 1a), 0.99 (g, 2b)] between the substituent effects of heterolytic Fe―C bond energies [ΔΔH_het(Fe―C)'s] of series 1 and 2 and the differences of acidic dissociation constants (ΔpK_a) of C―H bonds of p‐G‐C₆H₄CH₃ and p‐G‐C₆H₄CH₂CN imply that the governing structural factors for these bond scissions are similar. And the excellent linear correlations [r = ?1.00 (g, 1c), ?0.99 (g, 2d)] between ΔΔH_het(Fe―C)'s and the substituent σ_p^? constants show that these correlations are in accordance with Hammett linear free energy relationships. The polar effects of these substituents and the basis set effects influence the accuracy of ΔH_het(Fe―C)'s. ΔΔH_het(Fe―C)'s(1, 2) follow the Capto‐dative Principle. The detailed knowledge of the factors that determine the Fp―C bond strengths would greatly aid in understanding reactivity patterns in many processes. Copyright © 2011 John Wiley & Sons, Ltd.     

The research on the synthesis and structure of some new ferrocene derivatives

The reaction of C₅H₄RLi with FeCl₂ gave nine new compounds of Fe(C₅H₄R)₂ [R=C(CH₃)₂C₆H₄CH₃-p(-m,-o), C₆H₁₀C₆H₅, C(Me)₂C₆C₄OCH_3-o, C₆H₁₀C₆H₄CH₃-p(,-m,-o), C₆H₁₀C₆H₄OCH₃-p]. The compositions of compounds were determined through elementary analysis. The structural determination was made by IR and H²NMR. Mossbauer spectia were taken at room temperature. The IS and QS values are 0.41–0.45mm/s and 2.3–2.5mm/s., respectively. The solid state structure of the complex has been determined by a single crystal x-ray diffraction study, crystal data for Fe[C₅H₄C(CH₃)₂C₆H₅]₂: a=17.988(2)A, b=17. 411(2)A, c=7.496(1)A, α=β=90°, r=112.23°, Z=4, monoclinic form, space group C2/c. Our conclusions are: in π-acceptor ligand, the nucleophilic substituents decrease and the electrophilic substituts increase the metal to ligand electron cloud shift, which results in a decrease or an increase in the strength of the coordinate bonds and in the stabilization of the complexes by their steric effect.     

MULTIPHOTON IONIZATION MASS SPECTRA OF n-C3H7I AND i-C3H7I AT 532 nm

Multiphoton Ionization (MP) Mass Spectra of n-C₃H₇I AND i-C₃H₇I are obtained using a time-offlight mass spectrometer at 532 nm. No parentions are observed in MPI of both isomers. N-propyl cation dissociates more extensively than isopropyl cation. The C₂H⁺₅(M/Z=29) ion is observed instead of C₂H⁺₄(M/Z=28) ion in MPI of n-C₃H₇I, in contrast to i-C₃H₇I. It is found that parent molecules are first two-photon resonantly excited to A-band, then go through dissociation. Fragment ions are produced by ionization and dissociation of neutral fragments. We present directly the diss ociation pathways of n-propyl cation according to the results proposed by Levine using maximum entropy formalism. Moreover, those of isopropyl cation are discussed in this paper through branching ratio analyses.     

Spin-glass behavior and magnetic splitting in molecular magnetic materials {[N(n-C4H9)4][MIIFeIII(C2O4)3]}n (M = Co, Mn)

The mixed valence character and the antiferromagnetic coupling in the molecular magnetic materials {[N(n-C₄H₉)₄][M^IIFe^III(C₂O₄)₃]}_n (M = Co, Mn) were investigated by Mössbauer spectroscopy and magnetic measurements. In the material {[N(n-C₄H₉)₄][CoFe(C₂O₄)₃]}_n, the appearence of the spin-glass phase transition temperature and the magnetic phase transition under zero-field-cooled AC magnetic measurements were studied in the temperature range 5–100 K. In the Mössbauer spectra of {[N(n-C₄H₉)₄][MnFe(C₂O₄)₃]} a magnetic splitting was observed below 30 K. The appearance of the magnetic splitting indicates the occurrence of magnetic ordering in this complex. The hyperfine parameters show that the electronic state of iron is high-spin Fe³⁺.     

Study on the ferromagnetic state in iron mixed-valence complexes, A[FeIIFeIII(dto)3] (A = (n-CnH2n + 1)4N; dto = C2S2O2) by means of Mössbauer spectroscopy

We have investigated the ferromagnetic states for (n-C_nH_2n?+?1)₄N[Fe^IIFe^III(dto)₃] (n = 3–6; dto = C₂O₂S₂) by means of ⁵⁷Fe Mössbauer spectroscopy. The major component of the spin configuration in the ferromagnetic states for n = 3 and 4 is the low-temperature phase (LTP) with the Fe^III (S = 5/2) and Fe^II (S = 0) states. The high-temperature phase (HTP) of n = 4 remains by more than 20%, which is consistent with two ferromagnetic transitions (T_C = 7 & 13 K). Moreover, it was revealed that the Mössbauer spectra in the ferromagnetic states for n = 5 and 6 correspond to the HTP consisting of the Fe^II (S = 2) and Fe^III (S = 1/2) states.     

Mössbauer spectroscopic studies of (n-C n H2n +1NH3)2SnX6 (n=0-4; X = Cl or Br) and their related complexes

Complexes of the type (n-C _n H_2n +1NH₃)₂SnX₆ (0n 4 and X=Cl or Br) have been investigated with a variety of physico-chemical techniques. The structural phase transitions were found in some of these complexes. The temperature dependence of the Mössbauer spectral absorption area for (C₂H₅NH₃)₂SnCl₆ and (C₂H₅NH₃)₂SnBr₆ changed sharply at phase transition temperatures. The temperature dependences for (n-C₄H₉NH₃)₂SnCl₆ and (n-C₄H₉NH₃)₂SnBr₆ decreased gradually with an increase in temperature. The correlation between the temperature dependence of the spectral absorption area and the motion of n-C _n H_2n+1NH₃ ⁺ ions is discussed.     

Magnetic and electric hyperfine interactions of197Au in a paramagnetic molecular complex

Mössbauer spectra measured at low temperature on the paramagnetic compound [Au^II(maleonitrile dithiolate)₂] [(n-C₄H₉)₄N] are discussed in terms of slow electron spin relaxation. Good agreement is obtained using hyperfine interaction parameters derived from ESR measurements.     

Effect of peripheral ligands on the optical limiting property of homoleptic sandwich-type rare earth metal diphthalocyanines

The optical limiting property of sandwich-type rare earth metal diphthalocyanines, Eu[Pc(R)₈]₂[R=n-C₇H₁₅,OC₅H₁₁], was investigated via fluence-dependent transmittance measurements. The measurements were performed using collimated 10-ns pulses generated from a frequency-doubled Nd:YAG laser at 532-nm wavelength. The results demonstrated that Eu[Pc(OC₅H₁₁)₈]₂ exhibited better optical limiting behavior than Eu[Pc(C₇H₁₅)₈]₂. This is attributed to the enhanced delocalization of the π-conjugated system in Eu[Pc(OC₅H₁₁)₈]₂ because of the stronger electron-donating ability of alkoxy relative to that of alkyl. Received: 4 May 2001 / Accepted: 10 August 2001 / Published online: 17 October 2001     

Synthesis,structural study and thermal behaviour of a new compound: trirubidium bis(hydrogen sulphate) dihydrogen arsenate Rb3(HSO4)2.5(H2AsO4)0.5

Mixed crystals Rb₃(HSO₄)_2.5(H₂AsO₄)_0.5 have been prepared by slow evaporation from aqueous solution at room temperature. The crystals were characterized by X-ray single analysis, which revealed that Rb₃(HSO₄)_2.5(H₂AsO₄)_0.5 crystallizes in the space group P with lattice parameters: a = 7.471(3) Å; b = 7.636(1) Å; c = 12.193(2) Å; α = 71.91(1)°; β = 73.04(6)° and γ = 88.77(2)°. In this structure, the ordered S(1)O₄ and the disordered S(3)/AsO₄ tetrahedra are connected by O–H..O hydrogen bonds, to a zigzag chains running in the b-direction. These chains are, in turn, bonded to one another by disordered hydrogen bridges O–H..H–O, to give a planar structure, with hydrogen-bonded sheets, laying parallel to (1 0 0). Each disordered tetrahedron is linked to a tetrahedron neighbouring S(2)O₄ by ordered hydrogen bonds. Broader peaks in IR spectrum of the title material support the assumption of disordered structure. Thermal analysis of the superprotonic transition in Rb₃(HSO₄)_2.5(H₂AsO₄)_0.5 showed that the transformation to the high-temperature phase occurs by one-step process at 404 K. Thermal decomposition of this compound takes place at much higher temperatures, with an onset of approximately 473 K.     

Dielectric properties and phase transitions in alkali cyanides and cyanospinels under the influence of hydrostatic pressure

The effect of hydrostatic pressure p on the low-frequency dielectric constant ? has been investigated for selected cyanides (NaCN, KCN) and cyanospinels [K₂M(CN)₄ with M = Zn, Cd, Hg and Rb₂Zn(CN)₄] for pressures up to 7 kbar In the low-pressure region (decreases monotomcally resulting in negative first-order pressure denvatives of the dielectric constant The second- and third-order pressure derivatives, however, proved to be positive in most cases Using the dielectric constant as a very sensitive probe we observed phase transitions from the cubic low-pressure phase to an orthorhombic (NaCN) resp trigonal (cyanospinels) high-pressure phase at the following transition pressures (for 293.2 K) 2 260 kbar for NaCN, 1 438 kbar for K₂Hg(CN)₄, 2 660 kbar for K₂Cd(CN)₄, 3 318 kbar for K₂Zn(CN)₄ and 0.690 kbar for Rb₂Zn(CN)₄ The transition temperature T_c, was found to increase strictly linear with pressure between 290 and 340 K at a rate of dT_c/dp = 120 2 and 105 3 Kkbar^?1 for K₂Zn(CN)₄ and K₂Cd(CN)₄, respectively.     

EPR investigation of the spin-spin interactions in a Cu(II)-Gd(III)-Fe(III) heterospin system

The spin-spin interactions in a system that contains three different spin carriers, [{LCu}Gd(H₂O)₃×{Fe(CN)₆}] _n ·4nH₂O (1) [L²⁻, N,N-propylenedi(3-methoxysalicylideneiminato)], were investigated by electron paramagnetic resonance spectroscopy. Additional information was obtained by analyzing the discrete heterobinuclear system [LCu(OH₂)Gd(O₂NO)₃] (2), which contains the Cu(II)-Gd(III) pair also existing in the structure of 1, and the compounds [{LCu}Gd(H₂O)₃{Co(CN)₆}] _n ·3.5nH₂O and [{LCu}La(H₂O)₃×{Fe(CN)₆}] _n ·4nH₂O, which are isostructural with 1 and in which the paramagnetic low-spin Fe(III) and Gd(III) ions were replaced by diamagnetic low-spin Co(III) and La(III), respectively. The investigations were carried out in the temperature range of 293–4 K in both X- and Q-bands and also using a dual-mode X-band. The experimental spectra of the Cu(II)-Gd(III) pairs in 2 were interpreted as the sum of spectra of the ground spin state with total S = 4 and the excited state with S = 3 appearing due to the ferromagnetic exchange interaction between Cu(II) and Gd(III) ions. By fitting the experimental and simulated spectra, the zero-field splitting parameters of the Gd(III) ion are estimated and it is shown that no influence of the anisotropic interaction is detected. The magnetic properties of 1 are discussed from the perspective of the interaction of the Cu(II)-Gd(III) binuclear fragments with the Fe(III) ions.     

Pressure broadening and collisional shift of the Rb D2 absorption line by CH4, C2H6, C3H8, n-C4H10, and He

The pressure broadening and shift rates of the rubidium D2 absorption line 5²S_1/2→5²P_3/2 (780.24 nm) with CH₄, C₂H₆, C₃H₈, n-C₄H₁₀, and He were measured for pressures ≤80 Torr using high-resolution laser spectroscopy. The broadening rates γ_B for CH₄, C₂H₆, C₃H₈, n-C₄H₁₀, and He are 28.0, 28.1, 30.5, 31.3, and 20.3 (MHz/Torr), respectively. The corresponding shift rates γ_S are −8.4, −8.8, −9.7, −10.0, and 0.39 (MHz/Torr), respectively. The measured rates of Rb for the hydrocarbon buffer gas series of this study are also compared to the theoretically calculated rates of a purely attractive van der Waals difference potential. Good agreement is found to exist between measured and theoretical rates.     

Steric effects on the mechanism of reaction of nucleophilic substitution of β‐substituted alkoxyvinyl trifluoromethyl ketones with four secondary amines

The kinetics of the reaction of β‐substituted β‐alkoxyvinyl trifluoromethyl ketones R¹O‐CR²?CH‐COCF₃ ( 1a – e ) [( 1a ), R¹?C₂H₅, R²?H; ( 1b ), R¹?R²?CH₃; ( 1c ), R¹?C₂H₅, R²?C₆H₅; ( 1d ), R¹?C₂H₅, R²?V^?pNO₂C₆H₄; ( 1e ), R¹?C₂H₅, R²?C(CH₃)₃] with four aliphatic amines ( 2a – d ) [( 2a ), (C₂H₅)₂NH; ( 2b ), (i‐C₃H₇)₂NH; ( 2c ), (CH₂)₅NH; ( 2d ), O(CH₂CH₂)₂NH] was studied in two aprotic solvents, hexane and acetonitrile. The least reactive stereoisomeric form of ( 1a – d ) was the most populated ( E‐s‐Z‐o‐Z ) form, whereas in ( 1e ), the more reactive form ( Z‐s‐Z‐o‐Z ) dominated. The reactions studied proceeded via common transition state formation whose decomposition occurred by ‘uncatalyzed’ and/or ‘catalyzed’ route. Shielding of the reaction centre by bulky β‐substituents lowered abruptly both k′ (‘uncatalyzed’ rate constant) and k″ (‘catalyzed’ rate constant) of this reaction. Bulky amines reduced k″ to a greater extent than k′ as a result of an additional steric retardation to the approach of the bulky amine to its ammonium ion in the transition state. An increase in the electron‐withdrawing ability of the β‐substituent increased ‘uncatalyzed’ k′ due to the acceleration of the initial nucleophile attack (k₁) and ‘uncatalyzed’ decomposition of transition state (k₂) via promoting electrophilic assistance (through transition state 8 ). The amine basicity determined the route of the reaction: the higher amine basicity, the higher k₃/k₂ ratio (a measure of the ‘catalyzed’ route contribution as compared to the ‘uncatalyzed’ process) was. ‘Uncatalyzed’ route predominated for all reactions; however in polar acetonitrile the contribution of the ‘catalyzed’ route was significant for amines with high pK_a and small bulk. Copyright © 2007 John Wiley & Sons, Ltd.     

Nonlinear spin-wave phenomena in a [Mn{(R/S)-pn}2]2[Mn{(R/S)-pn}2H2O][Cr(CN)6] chiral molecular ferrimagnet

The instability of ferromagnetic resonance (FMR) spectra initiated by microwave power was observed in [Mn{(R/S)-pn}₂]₂[Mn{(R/S)-pn}₂H₂O][Cr(CN)₆] single crystals. It was established that the value of threshold microwave power P _th = 0.2−0.9 mW depends on the orientation of the easy magnetization axis relative to the sweeping magnetic field of the spectrometer. P > P _th spin-wave bistability occurs in the region of high microwave fields.     

The solution of Hydrogen in TaV2

TaV₂ may be prepared as a random b.c.c. alloy or as a (C-15) Laves phase. The behavior of hydrogen dissolved in b.c.c. TaV₂ is significantly different than that exhibited by hydrogen dissolved in (C-15) TaV₂. The b.c.c. TaV₂/H₂; system is similar to pure vanadium/H₂; in the region of hydrogen solid solution, the electronic contribution to the thermodynamics of solution is negligible and the system exhibits apparent H-H attractive interactions. A non-stoichiometric f.c.c. dihydride is formed at p_H2 = 10 atm, T = 273 K. (C-15) TaV₂ does not form a hydride phase; hydrogen is continuously absorbed into solid solution to a maximum hydrogen content H/M ? 0.60. The solid solution of hydrogen in (C-15) TaV₂ exhibits trends which are typical of intermetallie/H₂ systems. The dilute hydrogen region is marked by a strong positive deviation from Sieverts' Law, and the relative partial molar enthalpy of solution becomes less exothermic as the hydrogen content is increased. ΔV? vs H/M relationships and ΔS_H vs H/M relationships indicate that hydrogen segregation at the metal surface or at abnormally stable trapping sites does not contribute significantly to the thermodynamic behavior exhibited by hydrogen in (C-15) TaV₂. Analysis of the excess free energy of hydrogen suggests that electronic effects may exert a significant influence on the behavior of hydrogen in (C-15) TaV₂, even at dilute hydrogen contents. It is suggested that the radom substitution of tantalum into the vanadium lattice exerts a significantly greater effect on the vibrational entropy of dissolved hydrogen than does the structural transformation b.c.c. TaV₂ → (C-15) TaV₂.     

Low-frequency vibrational spectra of crystals of tutton salts

IR absorption spectra and polarized Raman spectra of crystals of Tutton salts K₂M(SO₄)₂6H₂O and (NH₄)₂M(SO₄)₂·6H₂O, where M=Co, Ni, Zn, have been obtained by experiment at 93 K and at room temperature. The frequencies and forms of normal modes of the [Zn(H₂O)₆]²⁺ octahedral complex have been calculated. The observed lines are assigned to the internal modes of the [M(H₂O)₆]²⁺ complex and external modes of the crystal lattice in accordance with the results of the calculations and factor-group analysis. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 4, pp. 445–449, July–August, 2000.