Differentiation of isomeric allylic alkenyl methyl ethers by Raman spectroscopy

The Raman spectra of several pairs of alkenyl methyl ethers of general structure R¹R²CCR⁵C(R³R⁴)OCH₃ and R¹R²C(OCH₃)C(R⁵)CR³R⁴ (R¹, R², R³, R⁴, R⁵ = H or C_nH_2n+1, n = 1-3) are reported and discussed, with a view to establishing whether Raman spectroscopy offers a viable means of distinguishing between these isomeric unsaturated species. Key bands associated with the ν(sp₂CH) and ν(CC) stretching modes are found to be particularly useful in this connection: R¹R²CCHCH₂OCH₃ and R¹R²C(OCH₃)CHCH₂ ethers (R¹, R² = CH₃, C₂H₅) are easily distinguished on this basis. Differentiation of their lower homologues, R¹CHCHCH₂OCH₃ and R¹CH(OCH₃)CHCH₂ (R¹ = CH₃, C₂H₅, C₃H₇), by similar means is also quite straightforward, even in cases where cis and trans isomers are possible. Pairs of isomeric ethers, such as CH₃CHC(CH₃)CH₂OCH₃ and CH₃CH(OCH₃)C(CH₃)CH₂, in which the structural differences are more subtle, may also be distinguished with care. Deductions based on bands ascribed to the stretching vibrations are usually confirmed by consideration of the signals associated with the corresponding δ(sp₂CH) deformation vibrations. Even C₂H₅CHCHCH(C₃H₇)OCH₃ and C₃H₇CHCHCH(C₂H₅)OCH₃ are found to have distinctive Raman spectra, but differentiation of these closely related isomers requires additional consideration of the low wavenumber region.     

Synthesis and crystal structure of [(η3-C3H5)(CO)2Mo(μ-S2CPCy3)-Mo(η3-CH2CMeCH2)(CO)2]

A novel dimolybdenum complex [(³-C₃H₅)(CO)₂Mo(-S₂CPCy₃)Mo(³-CH₂CMeCH₂)(CO)₂], obtained by reacting the [(CO)₂(³-C₃H₅)Mo(-S₂CPCy₃)Mo(CO)₃]^– anion with an excess of ClCH₂CMe=CH₂, has been characterized by i.r., ³¹P{¹H}, ¹H- and ¹³C-n.m.r. spectroscopy and by elemental analysis. The crystal structure of the complex, determined by X-ray diffraction, shows a definite preference for the central carbon of the S₂CPCy₃ bridge to bind to the Mo(2) atom coordinated by ³-2-methylallyl, rather than the Mo(1) atom attached to unsubstituted ³-allyl ligand.     

Copper(II) and nickel(II) complexes of N,N′-bis(2-cyanoethyl)-5, 7-dioxo-1,4,8,11-tetra-azacyclotetradecane

Summary Reaction of 5,7-dioxo-1,4,8,11-tetra-azacyclotetradecane with acrylonitrile gives the dicyanoethylated ligand (L). The Cu^II complex [CuLH_-2]·2H₂O has been isolated from basic solution where the macrocycle is deprotonated and acts as a dinegative quadridentate ligand. The ligand L is protonated in acidic solution and the ionisation equilibria can be summarised as LH _inf2 ^sup2+ LH⁺ +H⁺; K₁ LH⁺ L + H⁺; K₂ where pK₁ = 3.05 and pK₂ = 5.94 at 25 °C and I = 0.1 mol dm^-3 (NaNO₃). Complexation with Cu^II can be represented by the equilibria at 25 °C. Cu²⁺ + L [CuLH_-1]⁺ + H⁺; log_{11 – 1} = -3.43 Cu²⁺ + L [CuLH_-2] + 2H²⁺; log_{11 – 2} = -9.18 For Ni^II only the single equilibrium is of importance. Ni²⁺ + L [NiLH_-2] + 2H²⁺; log_{11 – 2} = -14.45     

Redox Properties of Rhodium(III) Oxo-Bridged Carboxylate Complexes

Chemical and electrochemical oxidation of rhodium (III) oxo-bridged carboxylate complexes was studied. The chemical [with O₃ and Ce(IV) salts] or electrochemical (at potentials of 1.00-1.20 V) oxidations of the binuclear complexes [Rh₂(-O)(-O₂CCH₃)₂(H₂O)₆]^{2 +} and [Rh₂(-O)(-O₂CCF₃)₂(H₂O)₆]^{2 +} leads to the superoxo complexes [Rh₂(-O)(O₂-)(-O₂CCH₃)₂(H₂O)₅]⁺ and [Rh₂(-O)(O₂ ^-)(-O₂CCF₃)₂(H₂O)₅]⁺ with terminal coordination of O₂-. The trinuclear acetate [Rh₃(₃-O)(-O₂CCH₃)₆(H₂O)₃]⁺, unlike its trifluoroacetate analog [Rh3(₃-O)(-O₂CCF₃)₆(H₂O)₃]⁺, is oxidized only electrochemically at a potential of 1.38 V. The oxidation of [Rh₃(₃-O)(-O₂CCH₃)₆(H₂O)₃]⁺ is reversible and involves formation of an unstable superoxo group O₂ ^- between two Rh₃III(₃-O) cores.     

Formation of cobalt(iii) cations with semiquinonediimine ligands

The reactions of polynuclear cobalt(ii) trimethylacetates [Co(OH) _n (OOCCMe₃)_2–n ] _x , Co₆(₃-OH)₂(OOCCMe₃)₁₀(HOOCCMe₃)₄, or Co₄(₃-OH)₂(OOCCMe₃)₆(HOEt)₆ with an excess of N-phenyl-o-phenylenediamine (1) in toluene followed by treatment with atmospheric oxygen afforded the diamagnetic complex [Co{²-(NPh)(NH)C₆H₄}₂{¹-(NH₂)C₆H₄(NPhH)}]⁺(Me₃CCOO...H...OOCCMe₃)^– (3), whose cation contains the Co^III atom. The reaction of Co₄(₃-OH)₂(OOCCMe₃)₆(HOEt)₆ with a deficient amount of diamine 1 in acetonitrile under an argon atmosphere gave rise to the antiferromagnetic ionic complex [Co{²-(NPh)(NH)C₆H₄}₂MeCN]⁺[Co₂(₂,²-OOCCMe₃)(₂-OOCCMe₃)₂(²-OOCCMe₃)₂]^–·2MeCN (4), whose cation is an isoelectronic analog of the cation in complex 3. The structures of the new compounds were established by X-ray diffraction analysis.     

The chemistry of cyclopentadienyl nitrosyl and related complexes of molybdenum,part 10(1). Cationic allyl complexes and attack thereon by nucleophiles

Summary The syntheses of [Mo(⁵-C₅H₅)(³-C₃H₄R)(CO)(NO)]⁺ (R=H, 1- or 2-Me) and [Mo(⁵-C₅H₅)(³-C₃H₅)(NCR)(NO)]⁺ (R=Me or Ph), by treatment of Mo(⁵-C₅H₅)(CO)₂(NO) with RC₃H₄Br and Ag⁺, and of Mo(⁵-C₅H₅)(³-C₃H₅)(NO)I with Ag⁺ in the presence of RCN, is described. Treatment of these cations with nucleophiles gives Mo(⁵-C₅H₅)(³-C₃H₅)(NO)X (X=halide, NCS or NCO), Mo(⁵-C₅H₅)(³-C₃H₅Q)(CO)(NO) (C₃H₅Q= propene ligand, Q= H, SCOMe, SEt, S₂CNMe₂, S₂CNEt₂, S₂CN(Bu-n)₂, C₅H₅, acac, OH, OMe or OAc), and [Mo(⁵-C₅H₅)(₂C₃H₅L)(CO)(NO)]⁺ (L=PEt₃, n-Bu₃P, PPh₃, PPh₂H, PMe₂Ph, C₅H₅N, 1-, 3- or 4-MeC₅H₄N and Me₂NNH₂). Reaction of [Mo(⁵-C₅H₅)(³-C₃H₅)(NCMe)(NO)⁺ with pyridine gave [Mo(⁵-C₅H₅)(³-C₃H₅)(pyr)(NO)]⁺, while treatment of [Mo(⁵-C₅H₅)(³-C₃H₅)(CO)(NO)]⁺ with PPh₃ in the presence of NaOEt afforded Mo(⁵-C₅H₅)(CO)(NO)(PPh₃). The¹H and¹³C n.m.r. spectra of these complexes are discussed particularly in relation to the occurrence ofexo andendo isomers of the allylic species. Comparison is made briefly between Mo(⁵-C₅H₅)(³-C₃H₅)(NO)I and Mo(C₅H₅)₂(NO)I.     

Synthesis and structures of silicon-, germanium-, and tin-containing tungsten carbyne complexes (ButO)3W≡C—EPh3 and [(ButO)3W≡C]2EPh2 (E = Si,Ge, Sn)

New tungsten carbyne complexes (Bu^tO)₃WC—SiPh₃, [(Bu^tO)₃WC]₂SiPh₂, [(Bu^tO)₃WC]₂GePh₂, and [(Bu^tO)₃WC]₂SnPh₂ were prepared by the reactions of (Bu^t)₆W₂ with Ph₃SiCC—Pr or Ph₂E(CC—Pr)₂ (E = Si, Ge, Sn) in individual crystalline form in 48—80% yields. The structures of both the (Bu^tO)₃WC—GePh₃ and (Bu^tO)₃WC—SnPh₃ compounds synthesized earlier and the new complexes were established by X-ray diffraction analysis.     

Preparation and structure of cobalt(II), nickel(II), copper(II) and zinc(II) complexes with 3-amino-5-(α/β)pyridyl-1, 2, 4-triazoles

Summary Complexes of bidentate 3-amino-5-()-pyridyl-1,2,4-triazole (L¹) and 3-amino-5-()-pyridyl-1, 2, 4-triazole (L²) of composition [ML¹Cl₂·H₂O], [ML²Cl₂·H₂O], [ML ₃ ^2/1 Cl₂] and [ML ₃ ^2/2 Cl₂] [M=Co^II, Ni^II, Cu^II, M=Zn^II] have been prepared and characterized by elemental analyses, i.r., u.v./visible, e.s.r. spectra, magnetic moments and molar conductances.     

Free Radical Reactions of N2O Molecules

Experimental data are presented on the spectral (ESR, IR, and optical) and thermochemical characteristics of a complex between the (Si–O)₃Si^.radical and an N₂O molecule. The rate constants of separate reactions in the systems (Si–O)₃Si^.+ N₂O and (Ge–O)₃Ge^.+ N₂O are found. The results of quantum chemical calculations of potential energy surfaces and spectral characteristics are presented for the following systems: H^.+ N₂O, H₃C^.+ N₂O, H₃Si^.+ N₂O, F₂HSi^.+ N₂O, F₃Si^.+ N₂O, and F₃Ge^.+ N₂O. The latter three systems served as molecular models for experimentally found systems. Based on experimental and theoretical data, the product of N₂O addition to (Si–O)₃Si^.has the structure Si–N=N–O^.. The reactions of free radicals H^., H₃C^., H₃Si^., F₂HSi^., F₃Si^., (Si–O)₃Si^., and (Ge–O)₃Ge^.with N₂O are compared. The spectrum of optical absorbance of the (Si–O)₃Si–O^.radical is recorded and qualitatively characterized.     

Temperature and ionic strength influence on U(VI/V) and U(IV/III) redox potentials in aqueous acidic and carbonate solutions

Redox potentials: E(UO ₂ ²⁺ /UO ₂ ⁺ )=60±4 mV/NHE, E(U⁴⁺/U³⁺)=–630±4mV/NHE measured at 25°C in acidic medium (HClO₄ 1M) using cyclic voltametry are in accordance with the published data. From 5°C to 55°C the variations of the potentials of these systems (measured against Ag/AgCl electrode) are linear. The entropies are then constant: [S(UO ₂ ²⁺ /UO ₂ ⁺ )–S(Ag/AgCl)]/F=0±0.3 mV/°C, [S(U⁴⁺/U³⁺)–S(Ag/AgCl)]/F=1.5±0.3 mV/°C. From 5°C to 55°C, in carbonate medium (Na₂CO₃=0.2M), the Specific Ionic Interaction Theory can model the experimental results up to I=2M (Na⁺, ClO ₄ ^– , CO ₃ ^2– ): E(UO₂(CO₃) ₃ ^4– /UO₂(CO₃) ₃ ^5– )=–778±5 mv/NHE (I=0, T=25°C, (25°C)=(UO₂(CO₃) ₃ ^4– , Na⁺)–(UO₂(CO₃) ₃ ^5– , Na⁺)=0.92 kg/mole, S(UO₂(CO₃) ₃ ^4– /UO₂(CO₃) ₃ ^5– =–1.8±0.5 mV/°C (I=0), =(Cl^–, Na⁺)=(1.14–0.007T) kg/mole. The U(VI/V) potential shift, between carbonate and acidic media, is used to calculate (at I=0,25°C):

Lithium and lanthanum complexes with acenaphthylene dianion. Molecular structure of [Li(Et2O)2]2μ2:η3[Li(η3:η3-C12H8)]2 complex

The lithium complex with the acenaphthylene dianion [Li(Et₂O)₂]₂₂:³[Li(³:³-C₁₂H₈)]₂ (1) was synthesized by the reduction of acenaphthylene with lithium in diethyl ether. According to the X-ray diffraction data, compound 1 has a reverse-sandwich structure with the bridging dianion ₂:³[Li(³:³-C₁₂H₈)]₂. Two lithium atoms in complex 1 are located between two coplanar acenaphthylene ligands of the ₂:³[Li(³:³-C₁₂H₈)]₂ ^2– dianion and are ³-coordinated with the five- and six-membered rings. The lanthanum complex with the acenaphthylene dianion [LaI₂(THF)₃]₂(₂-C₁₂H₈) (2) was synthesized by the reduction of acenaphthylene in THF with the lanthanum(iii) complex [LaI₂(THF)₃]₂(₂-C₁₀H₈) containing the naphthalene dianion. The ¹H NMR spectrum of complex 2 in THF-d₈ exhibits four signals of the acenaphthylene dianion, whose strong upfield shifts compared to those of free acenaphthylene indicate the dianionic character of the ligand. The highest upfield chemical shift belongs to the proton bound to the C atom on which, according to calculation, the maximum negative charge is concentrated.     

Das chlorsilylsubstituierte Silanimin Bu2SiNSiClBu2

In the thermolysis of the silaterazolines silatetrazoline ^tBu₂SiNSiCl^tBu₂ · ^tBu₃SiN₃ the silanimine ^tBu₂SiNSiCl^tBu₂ and the silyl azide ^tBu₃SiN₃ are formed quantitatively. The silanimine ^tBu₂SiNSiCl^tBu₂ has been trapped with Et₃NHF, Me₃NHCl, water, 1-butene, 2,3-dimethyl-1,3-butadiene, isobutene, methylvinyl ether, and ^tBu₂SiClN₃. The structure of the disiloxane (^tBu₂SiCl-NH-Si^tBu₂)₂O and of the bis(di-tert-butylchlorsilyl)-substituted silatetrazoline ^tBu₂SiNSiCl^tBu₂ · ^tBu₂SiClN₃ has been determined by X-ray structure analysis.     

Gold-ruthenium compounds containing bridging phosphide or thiolate groups: Crystal structures of the intermediate species [Ru3(CO)8L(μ3-η,η,η-{Me3SiCC(C2Fc)SC(Fc)CSCCSiMe3})] (L = NMe3 or PPh2H)

New tetranuclear complexes have been prepared using bridging phosphide or thiolate groups between phosphine gold fragments and the compound [Ru₃(CO)₉(μ₃-η²,η⁴,η³-{Me₃SiCC(C₂Fc)SC(Fc)CSCCSiMe₃})]. The crystal structures of the intermediates [Ru₃(CO)₈(NMe₃)(μ₃-η²,η⁴,η³-{Me₃SiCC(C₂Fc)SC(Fc)CSCCSiMe₃})] and [Ru₃(CO)₈(PPh₂H)(μ₃-η²,η⁴,η³-{Me₃SiCC(C₂Fc)SC(Fc)CSCCSiMe₃})] have been solved.     

Role of metal center in reactions of polynuclear nickel(ii) and cobalt(ii) trimethylacetates with 8-amino-2,4-dimethylquinoline

The reactions of 8-amino-2,4-dimethylquinoline (L) (1) with polynuclear nickel(ii) and cobalt(ii) hydroxotrimethylacetato complexes under anaerobic conditions were studied. The nonanuclear cluster Ni₉(₄-OH)₃(₃-OH)₃(_n-OOCCMe₃)₁₂(HOOCCMe₃)₄ gave the mononuclear complex Ni(²-L)(²-OOCCMe₃)₂ (2). The tetranuclear complex Ni₄(₃-OH)₂(-OOCCMe₃)₄(²-OOCCMe₃)₂(EtOH)₆ produced the mononuclear complex Ni(²-L)(²-OOCCMe₃)(OOCCMe₃)L (3). At room temperature, the cobalt-containing polynuclear trimethylacetates, viz., the polymer [Co(OH) _n (OOCCMe₃)_2–n ] _x and the tetranuclear complex Co₄(₃-OH)₂(-OOCCMe₃)₄(²-OOCCMe₃)₂(EtOH)₆, were transformed into the trinuclear cobalt(ii) complex Co₃(₃-OH)(-OOCCMe₃)₄(²-L)₂(OOCCMe₃) (4). Meanwhile, at 80 °C these compounds generated the binuclear cobalt(iii) complex Co₂(₂²-(HN)C₉NMe₂)₂(-OOCCMe₃)(L)(OOCCMe₃)₃ (5). The structures of the resulting compounds were established by X-ray diffraction analysis. Compounds 2—4 exhibit the antiferromagnetic spin-spin exchange coupling, whereas compound 5 is diamagnetic.     

EPR of gamma irradiation induced radicals in NaHCO3, CsHCO3 and Na2CO3

In this study gamma irradiated NaHCO₃, CsHCO₃ and Na₂CO₃ were investigated at room temperature. The radicals induced by gamma irradiation in NaHCO₃ were found to be CO⁻₃, HCO₃ and CO⁻₂; in CsHCO₃ the species were attributed to HCO₃; and in Na₂CO₃ to CO⁻₃ and CO⁻₂ radicals. The hyperfine parameters for the hydrogen in HCO₃, and the ¹³C nucleus in CO⁻₂ radical have been determined. The results were compared with literature data for similar compounds and the EPR properties of the CO⁻₂ radical were discussed.     

ESR spectroscopic investigation of steric and polar factors in the addition of radicals to unsaturated compounds

The rate constants of the addition of CCl₃CH₂ClCH₃(R⁶) radicals to -methyl-styrene, styrene, methyl methacrylate, methyl acrylate, and acrylonitrile and of CCl₃CH₂(CH₃)₂(R⁷) radicals to styrene, methyl acrylate, and acrylonitrile were determined by ESR spectroscopy. It was shown that the radicals R⁶ and R⁷ possess approximately equal reactivity in addition to unsaturated compounds, despite the difference in the donor-acceptor properties of the substituents at the vinyl group. In a comparison of the reactivity of radicals R⁶ and R⁷ with the reactivity of radicals CCl₃CH₂H₂(R¹), CCl₃CH₂HCH₃(R³), CCl₃CH₂HCl(R⁴), and ClCH₂CH₂Cl₂(R⁵) [1] in addition reactions, it was shown that polar and steric effects of the substituents situated in the -position to the radical site of the above-mentioned radicals, as well as the donor-acceptor properties of the substituents at the vinyl group in the unsaturated compounds, lead to appreciable changes in reactivity.A. N. Nesmeyanov Institute of Heteroorganic Compounds, Russian Academy of Sciences, 117813 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 136–141, January, 1992.     

An aqueous thermodynamic model for Ca2+−SO 3 2− ion interactions and the solubility product of crystalline CaSO3·1/2H2O

The solubility of CaSO₃·1/2H₂O(c) was studied under alkaline conditions (pH>8.2), in deaerated and deoxygenated Na₂SO₃ solutions ranging in concentration from 0.0002 to 0.4M and in CaCl₂ solutions ranging in concentration from 0.0002 to 0.01M, for equilibration periods ranging from 1 to 7 days. Equilibrium was approached from both the over- and the under-saturation directions. In all cases, equilibrium was reached in <1 days. The aqueous Ca²⁺–SO ₃ ^2– ion interactions can be satisfactorily modeled using either ion-association or ion-interaction aqueous thermodynamic models. In the ion-association model, the log K°=2.62±0.07 for Ca²⁺+SO ₃ ^2– CaSO ₃ ⁰ . In the Pitzer ion-interaction model, the binary parameters (⁰) and (¹) for Ca²⁺–SO ₄ ^2– were used, and the value of (²) was determined from the experimental data. As expected given the strong association constant, the value of (⁰) was quite small (about –134). We feel a combination of the two models is most useful. The logarithm of the thermodynamic equilibrium constant (K°) of the CaSO₃·1/2H₂O(c) solubility reaction (CaSO₃·1/2H₂O(c)Ca²⁺+SO ₃ ²⁺ +0.5H₂O) was found to be –6.64±0.07.     

Structures and relative energies of gas phase [C3H7O]+ ions

Ab initio molecular orbital calculations have been carried out for 17 possible isomeric [C₃H₇O]⁺ structures. Optimized geometries have been obtained with a split-valence basis set and improved relative energies determined with polarization basis sets and with incorporation of electron correlation. The results agree well with available experimental data. In particular, (CH₃)₂COH⁺, CH₃CH₂CHOH⁺, CH₃CHOCH₃⁺, CH₃CH₂OCH₂⁺, and have been confirmed as low-energy isomers. Six additional structures appear to be energetically accessible and to offer a reasonable prospect for experimental observation. These are CH₂CHCH₂OH₂⁺, CH₂C(CH₃)OH₂⁺, CH₃CHCHOH₂⁺, CH₂CHOHCH₃⁺, and .