Conformational studies of some 2-phenylpropyl derivatives by NMR spectroscopy and use of lanthanide shift reagents

The conformational distribution of CH₃CH(Ph)CH₂X (X = OH, OCH₃, NH₂ Cl) has been studied by NMR and IR spectroscopy. The results are interpreted in favour of the conformers with methoxy- or chloro-groups anti to the phenyl group, but the amino group anti to the methyl group. For the alcohol both forms are about equally populated. It is suggested that intra-molecular hydrogen bonding might be affecting the conformational equilibria when X = OH, NH₂.     

Synthesis,Characterizations, and Structure of Group 4 Metallocene Complexes of Some Difunctional Ligands Containing Oxygen and Sulfur Donors

Reactions of CH₃OCH₂CH₂OH, PhOCH₂CH₂OH, o-CH₃OC₆H₄CH₂OH, or PhSCH₂CH₂OH with Cp₂ZrCl₂ in the presence of NEt₃ gave series monomeric complexes Cp₂ZrClX (X = OCH₂CH₂OCH₃ ( 1 ), OCH₂CH₂OPh ( 2 ), o-OCH₂C₆H₄OCH₃ ( 3 ) or OCH₂CH₂SPh ( 4 )). In a reaction of Cp₂TiCl₂ with PhSCH₂CH₂OH in the presence of NEt₃, the complex Cp₂TiCl(OCH₂CH₂SPh) ( 5 ) was obtained. These complexes were characterized by the ¹H and ¹³C NMR, and the chemical shifts of the Cp rings for complexes 1–4 are nearly identical, despite differences in ligands for an indication of similar structures of these complexes around the metal center. Complex 4 crystallizes into the monoclinic P2₁/c space group with a = 13.806(3) Å, b = 16.394(3) Å, c = 7.838(2) Å, β = 100.85(3)° Z = 4, R = 0.029, R_w = 0.044, and Gof = 1.19. The molecular structure of complex 4 shows that the 2-(phenylthio)ethoxide bonds to the Zr metal center through the alkoxide donor leaving the thioether donor free from coordination.     

Role of donor-acceptor functional groups in N3P3 cyclic-triphosphazene backbone. Unraveling bonding characteristics from natural orbitals within an extended transition state-natural orbital for the chemical valence scheme

The formation of cyclophosphazenes containing several ligands or substituent groups gives rise to an attractive derivative set, for development of novel applications, with variable properties. Here, it is possible to unravel the role of different functional groups attached to the N₃P₃ backbone, to reach a better understanding of the bonding character in the cyclic [─P─N─] skeleton. We employed the extended transition state-natural orbital for the chemical valence scheme to unravel the σ and π orbital kernels that are involved in the assembling of such structures, by varying the acceptor-donor characteristics of the ─CF₃, ─NO₂, ─COOH, ─CN, ─NH₂, ─OH, and ─OCH₃ groups, where ─NO₂ behaves as a stronger electron-withdrawing substituent rather than ─CF₃, ─COOH, and ─CN, denoting that the nature of the ligand-phosphazene interaction contributes to some degree to the bond strength of the cyclic [─P─N─] backbone. Our results reveal that the electron-withdrawing ─NO₂ group leads to higher σ and π [─P─N─] orbital-energy contributions, which is reflected in a shortening of the [─P─N─] distance, contrasting with the case of electron-donating groups such as ─NH₂, ─OH, and ─OCH₃ within the phosphazene set. These insights allow further variation and modulation of the bonding in the [─P─N─] ring.     

Bis(trimethylsilyl)diazene revisited. Density functional theory (DFT) calculations of nitrogen NMR parameters of some azo‐compounds

Calculations of nitrogen NMR parameters [chemical shifts δN and indirect nuclear spin–spin coupling constants J(N,N), J(N,¹³C), J(²⁹Si,N)] of noncyclic azo‐compounds R¹ NN R² (R¹, R² = H, Me, Ph, SiH₃, SiMe₃) and cyclic azo‐compounds [NNCH₂, NN(CH₂)₃ NN(CH₂)₂SiH₂, and NN(SiH₂CH₂SiH₂)] by density functional theory (DFT) methods [B3LYP/6‐311+G(d,p) level of theory] provide data in reasonable agreement with experimental values. The influence of cis‐ and trans‐geometry is reflected by the calculations, and amino‐nitrenes are also included for comparison. The spin–spin coupling constants are analyzed with respect to contact (Fermi contact term, FC) and non‐ contact contributions (paramagnetic and diamagnetic spin‐orbital terms, PSO and DSO, and spin‐dipole term, SD). Bis(trimethylsilyl)diazene 6a can be generated by an alternative method, using the reaction of bis(trimethylsilyl)sulfur diimide with bis‐ (trimethylsilyl)amino‐trimethylsilylimino‐phosphane. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:84–91, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20075     

Low energy,low temperature mass spectra: I—selected derivatives of n-octane

The low voltage, low temperature mass spectra of a series of octane derivatives n-C₈H₁₇X with X=CH₃, OH, OCH₃, NH₂, NHCH₃, N(CH₃)₂, CO₂H, CO₂CH₃, CO₂C₂H₅, CHO and COCH₃ are reported and discussed, using arguments involving thermochemistry where appropriate. The structures of these compounds can be uniquely assigned on the basis of such mass spectra.     

Drei Heterocubanartige (MII4O4)‐Typ Verbindungen (M = FeII,CoII, NiII)

By reaction of M^IICl₂·x H₂O (M = Fe (x = 4), Co, Ni (x = 6)) and LiOH·H₂O in diethylene glycol (DEG) rod‐like crystals of the composition M^II₄Cl₄(OCH₂CH₂OCH₂CH₂OH)₄ are formed. According to X‐ray diffraction data obtained by both, single crystals and powders, the Co^II and Ni^II compounds crystallize monoclinic with C2/c (Co^II₄Cl₄(OCH₂CH₂OCH₂CH₂OH)₄ ( 1 ): a = 2084.1(4), b = 919.0(2), c = 1754.0(4) pm, β = 124.3(1)°, Z = 4; Ni^II₄Cl₄(OCH₂CH₂OCH₂CH₂OH)₄ ( 2 ): a = 2055.2(4), b = 932.1(2), c = 1727.4(4) pm, β = 125.2(1)°, Z = 4), whereas Fe^II₄Cl₄(OCH₂CH₂OCH₂CH₂OH)₄ ( 3 ) crystallizes tetragonal with (a = 1251.4(2), c = 915.3(2) pm, Z = 2). All compounds exhibit analogous molecular structures which are built of a heterocubane‐type core consisting of four metal ions and four deprotonated oxygen atoms of four coordinated diethylene glycol molecules. Neutrality of charge is realized by additional coordination of four chloride anions. In addition to the structural characterization, the thermal and magnetical properties of the title compounds are investigated in detail.     

The heavier pnictogen and chalcogen analogues of isocyanic and cyanic acids and their dimers: A high level ab initio study

The CCSD(T)/cc-pVTZ//CCSD/cc-pVTZ method is used to determine the geometries and energetics of the isomers HXCY vs HY─CX (XN, P, As; YO, S) and their dimers from chain dimerizations and head-to-head or head-to-tail [2 + 2] cyclodimerizations. The HO─CX structures with CX triple bonds lie at energies at least 18.5 kcal/mol above their HXCO isomers. However, the energy differences between the HXCS and HS─CX isomers are found to be particularly small, especially in the [H,P,C,S] and [H,As,C,S] systems. For (HNCY)₂, the lowest energy dimers are the chain isomers, which lie ~11 kcal/mol below the lowest energy cyclic dimers aNO containing a NCNC ring and cNS containing a NCSC ring. Formation of the remaining dimers through dimerization from two monomers is predicted to be endothermic and thus thermodynamically disfavored. However, the energies of the chain isomers in the other (HXCY)₂ (XP, As; YO, S) series are higher than those of the corresponding isomeric lowest energy cyclodimers. For (HXCO)₂ (XP, As), the lowest energy structures are the head-to-head dimers hPO and hAsO containing a C─C─XX ring. For (HXCS)₂ (XP, As), the lowest energy structures are the head-to-head dimers gPS and gAsS with a CCXS ring.     

Methanol oxidation on the PtPd(111) alloy surface: A density functional theory study

The mechanisms of methanol (CH₃OH) oxidation on the PtPd(111) alloy surface were systematically investigated by using density functional theory calculations. The energies of all the involved species were analyzed. The results indicated that with the removal of H atoms from adsorbates on PtPd(111) surface, the adsorption energies of (i) CH₃OH, CH₂OH, CHOH, and COH increased linearly, while those of (ii) CH₃OH, CH₃O, CH₂O, CHO, and CO exhibited odd‐even oscillation. On PtPd(111) surface, CH₃OH underwent the preferred initial C H bond scission followed by successive dehydrogenation and then CHO oxidation, that is, CH₃OH → CH₂OH → CHOH → CHO → CHOOH → COOH → CO₂. Importantly, the rate‐determining step of CH₃OH oxidation was found to switch from CO → CO₂ on Pt(111) to COOH → CO₂ + H on PtPd(111) with a lower energy barrier of 0.96 eV. Moreover, water also decomposed into OH more easily on PtPd(111) than on Pt(111). The calculated results indicate that alloying Pt with Pd could efficiently improve its catalytic performance for CH₃OH oxidation through altering the primary pathways from the CO path on pure Pt to the non‐CO path on PtPd(111).     

Synthesis,X-ray structure,DFT studies,and catalytic activity of a vanadium(V) complex containing a tridentate Schiff base

Reactions of a solution of NH₄VO₃ in H₂O₂ and water and salicylidene benzoyl hydrazine as a tridentate Schiff base (ONO) afford a six-coordinate V(V) complex [VO(ONO)(OCH₃)(CH₃OH)] with a distorted octahedral configuration. The complexes [VO(ONO)(OCH₃)(CH₃OH)] were isolated as air-stable crystalline solids and fully characterized, including by single-crystal X-ray structure analysis. DFT calculations have been performed to understand the electronic structure of the complex. Vibrational frequencies and maximum absorption wavelengths of the complex theoretically calculated are in good agreement with experimental values. [VO(ONO)(OCH₃)(CH₃OH)] shows efficient oxidation of sulfides to their corresponding sulfoxides using urea hydrogen peroxide as the oxidant at room temperature under air.     

Tautomerism of monochalcogenosilanoic acids CH3Si(O)XH (X = S,Se, Te) in the gas phase and in the polar and aprotic solution: An ab initio computational investigation

Computational investigations by an ab initio molecular orbital method (HF and MP2) with the 6‐311+G(d,p) and 6‐311++G(2df, 2pd) basis sets on the tautomerism of three monochalcogenosilanoic acids CH₃Si(?O)XH (X = S, Se, and Te) in the gas phase and a polar and aprotic solution tetrahydrofuran (THF) was undertaken. Calculated results show that the silanol forms CH₃Si(?X)OH are much more stable than the silanone forms CH₃Si(?O)XH in the gas‐phase, which is different from the monochalcogenocarboxylic acids, where the keto forms CH₃C(?O)XH are dominant. This situation may be attributed to the fact that the Si? O and O? H single bonds in the silanol forms are stronger than the Si? X and X? H single bonds in the silanone forms, respectively, even though the Si?X (X = S, Se, and Te) double bonds are much weaker than the Si?O double bond. These results indicate that the stability of the monochalcogenosilanoic acid tautomers is not determined by the double bond energies, contrary to the earlier explanation based on the incorrect assumption that the Si?S double bond is stronger than the S?O double bond for the tautomeric equilibrium of RSi(?O)SH (R?H, F, Cl, CH₃, OH, NH₂) to shift towards the thione forms [RSi(?S)OH]. The binding with CH₃OCH₃ enhances the preference of the silanol form in the tautomeric equilibrium, and meanwhile significantly lowers the tautomeric barriers by more than 34 kJ/mol in THF solution. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

Synthesis and characterization of ferrocenylalkoxygermatranes and crystal structures of FcCH2OGe (OCH2CH2)3N and FcCH(CH3)OGe(OCH2CH2)3N1

Germatranes bearing a ferrocenylalkoxyl moiety have been obtained by the reaction of HOGe(OCH₂CH₂)₃N with various ferrocenyl alcohols. A convenient new synthesis method of FcCH₂OGe(OCH₂CH₂)₃N was reported. FcCH₂OGe(OCH₂CH₂)₃N was prepared in 93% yield when FcCH₂OH reacted with HOGe(OCH₂CH₂)₃N in chloroform at room temperature in the presence of molecular sieves (3 Å) as a dehydrating agent. All compounds were characterized by elemental analysis, ¹H NMR and IR spectroscopy. The molecular structures of FcCH₂OGe(OCH₂CH₂)₃N and FcCH(CH₃)OGe(OCH₂CH₂)₃N have been determined by X‐ray diffraction. The antitumor activities of FcCH₂OGe(OCH₂CH₂)₃N and p‐FcC₆H₄CH₂OGe(OCH₂CH₂)₃N were determined. Copyright © 2005 John Wiley & Sons, Ltd.     

Fluorine Kα x-ray emission studies of fluorinated organic compounds

Fluorine K_α X-ray emission spectra have been measured and interpreted using UV photoelectron and X-ray photoelectron spectral data and the results of quantum-chemical calculations, for a series of fluorine-containing organic molecules: CH₃F, n-C₅F₁₂, polytetrafluoroethylene, tetrafluoroethylene, 4-XC₆H₄F (X = H, F, NH₂, NO₂), 1,3-difluorobenzene, 1,2,4,5-tetrafluorobenzene, 1,4-difluorobenzene, C₆F₅X (X = H, F, SCH₃, OCH₃, CN, NO₂, C₆F₅, P(OCH₃)₂), pentafluoropyridine, octafluoronaphthalene and 2,4-dinitrofluorobenzene, all in solid or gaseous states. It has been concluded that the fluorine 2pAO contribution to the highest occupied π-orbitals of the benzene ring and π-orbital of the ethylene bond is small: it is somewhat higher for a system of lower-lying π-orbitals and the highest for σ-orbitals. CH₃F is assumed to have hyperconjugation.     

Alternativ-Liganden. XXX [1] Neue Tripod-Liganden XM' (OCH2PMe2)n(CH2CH2PMe2)3−n (M' = Si; Ge; n = 0–3) für Käfigstrukturen

Alternative Ligands. XXX Novel Tripod Ligands XM' (OCH₂PMe₂)_n(CH₂CH₂PMe₂)_3?n (M' = Si, Ge; n = 0–3) for Cage Structures Attempts to prepare new tripod ligands XSi(OCH₂PMe₂)₃ [X = CF₃ ( 15 ), C₆F₅ ( 16 ), NMe₂ ( 17 ), Cl ( 18 ), F ( 19 ), H ( 20 ), OEt ( 21 ), OMe ( 22 )] prove to be unsuccessful in spite of using different pathways, because the groups X undergo following reactions giving insoluble solids (polyadducts) or form inseparable mixtures, e. g. (RO)_nSi(OCH₂PMe₂)_4?n (R = Me, Et). In many cases Si(OCH₂PMe₂)₄ ( 13 ) can be isolated from the reaction mixture. The syntheses of the ligands XSi(CH₂CH₂PMe₂)₃ [X = NMe₂ ( 6 ), Cl ( 7 ), F ( 8 ), OMe ( 9 ), Vi ( 12 )], Si(OCH₂PMe₂)₄ ( 13 ) und Me₃GeOCH₂PMe₂ ( 14 ) are successful. The compounds MeSi(OCH₂PMe₂)₂CH₂CH₂NMe₂ ( 10 ) and MeSi(OCH₂PMe₂)₂CH₂CH₂P(CF₃)₂ ( 11 ) with different donor groups are obtained in good yields. The preparative program includes the synthesis of the known representatives MeSi(OCH₂PMe₃)₃ ( 1 ), MeSi(OCH₂PMe₂)₂CH₂CH₂PMe₂ ( 2 ), MeSi(OCH₂PMe₂)(CH₂CH₂PMe₂)₂ ( 3 ), MeSi(CH₂CH₂PMe₂)₃ ( 4 ) and MeGe(OCH₂PMe₂)₃ ( 5 ). Important preparative steps are the substitution of M'Cl (M' = Si, Ge) by Me₂PCH₂O groups and the photochemically induced or base catalyzed addition of HNMe₂, HPMe₂ or HP(CF₃)₂ to SiVi functions. The novel compounds are characterized by analytical and spectroscopic (IR, NMR, MS) investigations.     

Substituent effects in second row molecules : Sulfur(II) compounds

Substituent effects arising from directly bonded groups in sulfur-containing compounds are investigated by molecular orbital calculations of relative energies. Interaction energies, basicities and acidities are obtained from calculations at the supplemented 4–3 IG and 6–3 IG basis set levels for substitution in the three series of sulfur compounds SX^-, SHX, and SH₂X⁺ with X = BH₂, CH₃, NH₂, OH, F and in the bisubstituted series SX₂ (X = CH₃, F). Donor-acceptor interactions are dominated by the σ-electrons and readily account for the data; substitution by BH₂ is an exception, requiring consideration of π-bonding, especially in the anion. Charge transfer, both to and from the second row element, is better tolerated by the sulfur-containing systems than by the corresponding oxygen compounds.     

The Evolution Aspect in the Crystallization Process of [5,5′‐(HCF2CF2CH2OCH2)2‐2,2′‐bpy]MX2 (M = Pt,Pd; X = I,Br): Role of the Intramolecular CF2─H…X(─M) Hydrogen Bonds

The general species (2,2′‐bpy)MX₂ (M = Pd, Pt; X = Br, I) in a crystallization process results in an isomorphous convergence in P2₁/c. Yet, with polyfluorinated side chains, the general [5,5′‐(HCF₂CF₂CH₂OCH₂)₂‐2,2′‐bpy]MX₂ species proceeds to crystallize the isomorphous structures of 5 (M = Pt; X = I) and 6 (M = Pd; X = I) in P2₁/c only; structure 7 (M = Pt; X = Br) crystallizes in P2₁/c but is not isomorphous with 5 and 6 , and structure 8 (M = Pd; X = Br) forms differently in P–1. The causes making the system nonlinear are (1) the intramolecular CF₂─H^…X(─M) hydrogen bonds found in 5–7 but not in 8, and (2) in response to the transition from I to Br, bifurcated [C─H^…]₂ F ─C hydrogen bonds that are formed in 5 and 6 and bifurcated C─ H [^…F─C]₂ hydrogen bonds in 7 . Additionally, the intramolecular CF₂─H^…X(─M) hydrogen bonding from compounds 5–7 could be affirmed by the IR studies.     

Density functional theory investigation of the binding interactions between phosphoryl,carbonyl, imino,and thiocarbonyl ligands and the pentaaqua nickel(II) complex: Coordination affinity and associated parameters

Density Functional Theory (UB3LYP/6‐311++G(d,p)) calculations of the affinity of the pentaaqua nickel(II) complex for a set of phosphoryl [O?P(H)(CH₃)(PhR)], imino [HN?C(CH₃)(PhR)], thiocarbonyl [S?C(CH₃)(PhR)] and carbonyl [O?C(CH₃)(PhR)] ligands were performed, where R?NH₂, OCH₃, OH, CH₃, H, Cl, CN, and NO₂ is a substituent at the para‐position of a phenyl ring.The affinity of the pentaaqua nickel(II) complex for these ligands was analized and quantified in terms of interaction enthalpy (ΔH), Gibbs free energy (ΔG²⁹⁸), geometric and electronic parameters of the resultant octahedral complexes. The ΔH and ΔG²⁹⁸ results show that the ligand coordination strength increases in the following order: carbonyl < thiocarbonyl < imino < phosphoryl. This coordination strength order is also observed in the analysis of the metal‐ligand distances and charges on the ligand atom that interacts with the Ni(II) cation. The electronic character of the substituent R is the main parameter that affects the strength of the metal‐ligand coordination. Ligands containing electron‐donating groups (NH₂, OCH₃, OH) have more exothermic ΔH and ΔG²⁹⁸ than ligands with electron‐withdrawing groups (Cl, CN, NO₂). The metal‐ligand interaction decomposed by means of the energy decomposition analysis (EDA) method shows that the electronic character of the ligand modulates all the components of the metal‐ligand interaction. The absolute softness of the free ligands is correlated with the covalent contribution to the instantaneous interaction energy calculated using the EDA method. © 2013 Wiley Periodicals, Inc.     

NEW CYCLIC AND POLYMERIC PHOSPHAZENES DERIVED FROM N-SILYLPHOSPHORANIMINES

Silicon-nitrogen-phosphorus compounds of the type Me ₃ SiN═PR(R′)X(X= Cl, Br, OCH₂CF ₃ , OPh), known as N-silylphosphoranimines,are useful precursors to both cyclic and polymeric phosphazenes.Depending on the leaving group (X), thermolysis reactions afford either cyclic trimers, [N═PR(R′)] ₃ (when X = Cl, Br), or linear polymers,[N═PR(R′)]_n (when X = OCH ₂ CF ₃ or OPh). Treatment of the P-trifluoroethoxy and P-phenoxy derivatives, Me ₃ SiN═PR(R′)X (X = OCH ₂ CF ₃ , OPh), with alcohols at lower temperature usually results in the formation of cyclic phosphazene trimers via silyl ether elimination. Recently, we have applied these synthetic methods to the preparation of some new phosphazene systems including a series of 4-aryl-functionalized trimers and polymers and a variety of non-geminal, mixed-substituent cyclic trimers. Representative examples of the synthesis, structural characterization, and reactivity of these new phosphazenes and their Si─N─P precursors are reported here.     

Preparation and photophysical properties of halogenated silicon(IV) phthalocyanines substituted axially with poly(ethylene glycol) chains

A series of silicon(IV) phthalocyanines with two axial poly(ethylene glycol) chains SiPcX₈[(OCH₂CH₂)_nOCH₃]₂ (X=H, Cl, Br; n≈16) have been prepared of which the photosensitizing properties are enhanced as the periphery of the macrocycle is substituted with heavier halogens.     

Preparation of cadmium sulfide from CdCl2(CdBr2, CdI2)-CS(NH2)2-CH3OH systems

Summary The solubility isotherms of the ternary systems CdX₂-CS(NH₂)₂-CH₃OH (X = Cl, Br, I) at 25°C have been investigated. The fields of equilibrium existence of the salts CdCl₂·2CH₃OH, CdCl₂·2CS(NH₂)₂, CS(NH₂)₂, CdBr₂·3CH₃OH, CdBr₂·CS(NH₂)₂, CdBr₂·2CS(NH₂)₂, CdI₂ and CdI₂·2CS(NH₂)₂ were determined. The formation of CdS by thermal dissociation of double salts and saturated solutions is discussed.

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Kadmiumsulfid-Herstellung aus CdCl₂(CdBr₂,CdI₂)-CS(NH₂)₂-CH₃OH — Systemen

Zusammenfassung Die Löslichkeitskurven der ternären Systeme CdX₂-CS(NH₂)₂-CH₃OH (X = Cl, Br, I) wurden untersucht. Die Gleichgewichtsbereiche der Salze CdCl₂·2CH₃OH, CdCl₂·2CS(NH₂)₂, CS(NH₂)₂, CdBr₂·3CH₃OH, CdBr₂·CS(NH₂)₂, CdBr₂·2CS(NH₂)₂, CdI₂ und CdI₂·2CS(NH₂)₂ wurden bestimmt. Die Bildung von CdS als durch thermische Zersetzung von Doppelsalzen und gesättigten Lösungen wird diskutiert.