Spin-spin coupling constants of 13C-1H and 1H- 1H in 4-substituted pyridines

The spin-spin coupling constants (SSCC) of ¹³C-¹H and ¹H-¹H in 4-substituted pyridines, C₅H₄NX [X=,CN, COCH₃, COOCH₃, N(CH₃)₂, NO₂, OCH₃, Cl, Br], were investigated. To determine the constants, the proton-coupled NMR spectra of ¹³C and ¹³C-satellites in the PMR spectra of the compounds, recorded for monomolecular solutions of 4-substituted pyridines in DMSO-D₆, were analyzed. The interrelationship of the SSCC of ¹³C-¹H and ¹H-¹H in 4-substituted pyridines with the analogous constants in monosubstittued benzenes were obtained. The correlations of the constants with the F- and R-parameters of the substituents are discussed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 948–952, July, 1984.     

Orientation of the unshared electron pair of the nitrogen atom in N-substituted 2,5-dimethyl-4-piperidinones

The axial orientation of the unshared electron pair of the nitrogen atom in cis isomers of N-substituted [R=H, CH₃, CH₂C₆H₅, or C(CH₃)₃] 2,5-dimethyl-4-piperidinones was proven by using the stereospecificity of the direct ¹³C-¹³C spin-spin coupling constants, vicinal ¹³C-¹H spin-spin coupling constants, and two-dimensional nuclear-Overhauser-effect spectroscopy (NOESY).Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 512–513, April, 1989.     

Analysis of effect of specific C-H ...X interaction on the direct13C-1H spin-spin coupling constants based onab initio quantum-chemical calculations

Anab initio quantum-chemical calculation of the direct^13C–¹H spin-spin coupling constants in the CH₄–H₂O system was carried out and experimental data obtained for a series ofN-vinyl compounds were analyzed. The specific C-H ....X (X = O, N) intramolecular interactions result in increasing the direct¹³C–¹H spin-spin coupling constant of the hydrogen involved in bonding and decreasing the direct¹³C-¹H spin-spin coupling constant for the hydrogen atom that takes no part in the interaction.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1362–1365, Tune, 1996.     

An ab initio molecular orbital study of the deprotonation of amines

The geometries of the amines NH₂X and amido anions NHX^?, where X = H, CH₃, NH₂, OH, F, C₂H, CHO, and CN have been optimized using ab initio molecular orbital calculations with a 4-31G basis set. The profiles to rotation about the N? X bonds in CH₃NH^?, NH₂NH^?, and HONH^? are very similar to those for the isoprotic and isoelectronic neutral compounds CH₃OH, NH₂OH, and HOOH. The amines with unsaturated bonds adjacent to the nitrogen atoms undergo considerable skeletal rearrangement on deprotonation such that most of the negative charge of the anion is on the substituent. The computed order of acidity for the amines NH₂X is X = CN > HCO > F ≈ C₂H > OH > NH₂ > CH₃ > H and for the reaction NHX^? + H⁺ → NH₂X the computed energies vary over the range 373–438 kcal/mol.     

Mono‐ and heterodi‐nuclear complexes of aluminium: synthesis,characterization and antifungal activity

Some new types of mononuclear derivatives, AlL(1–4)L(1–4)H ( 1a–1d ) of aluminium were synthesized by the reaction of Al(OPrⁱ)₃ and LH₂ [XC(NYOH)CHC(R)OH], X = CH₃, Y = (CH₂)₂, R = CH₃(L1H₂); X = C₆H₅, Y = (CH₂)₂, R = CH₃(L2H₂); X = CH₃, Y = (CH₂)₃, R = CH₃(L3H₂); X = C₆H₅, Y = (CH₂)₃, R = CH₃(L4H₂) in 1:2 molar ratio in refluxing benzene. Reactions of AlL(1–4)L(1–4)H with hexamethyldisilazane in 2:1 molar ratio yielded some new ligand bridged heterodinuclear derivatives AlL(1–4)L(1–4)SiMe₃ ( 2a – 2d ). All these newly synthesized derivatives were characterized by elemental analysis and molecular weight measurements. Tentative structures were proposed on the basis of IR and NMR spectra (¹H, ¹³C, 27 Al and ²⁹Si) and FAB‐mass studies. Schiff base ligands and their mono‐ and heterodi‐nuclear derivatives with aluminium have been screened for fungicidal activities. These compounds showed significant antifungal activity against Aspergillus niger and A. flavus. Copyright © 2007 John Wiley & Sons, Ltd.     

The synthesis and spectroscopic examination of telluronium salts based on the 1-organo-3,4-benzo-1-telluracyclopentane cation

The syntheses of a new range of telluronium salts based on the 1-organo-3,4-benzo-1-telluracyclopentane cation are reported (C₈H₈TeRX: R  CH₃, CH₂CH₃, X  I; R  CH₃, X  PhCOO; R  CH₃, X  ClO₄; R  CH₃, X  BPh₄; R  Ph, X  BPh₄; R  CH₂Ph, CH₂CHCH₂, CH₂COPh, X  Br.) Solution studies using ¹H, ¹³C and ¹²⁵Te NMR spectroscopy in conjunction with conductivity and molecular weight measurements show the salts to be associated via weak “ionic” bonds in solvents of lower polarity such as chloroform but to be more ionic and strongly solvated in DMSO. Solvents such as DMF provide an intermediate and more complex situation.Mass spectra indicate that association can extend to the gas phase and some novel features in the spectra are discussed. Infrared studies indicate polymorphism for 1-methyl-3,4-benzo-1-telluracyclopentane perchlorate with one form containing perchlorate ions interacting with tellurium.     

Carbon-13 NMR spectra of some o-carbonyl benzeneselenenyl derivatives

The ¹³C NMR signals have been assigned for some ortho-carbonyl benzene-selenenyl derivatives, COR.C₆H₄. Sex, where R = H, CH₃, OCH₃ and OC₂H₅ and X = Cl, Br, CN, SCN, SeCN and CH₃. The effects of the nature of R and X have been discussed.     

Transition metal catalyzed alternating copolymerizations of olefins and co

Well defined Pd(II) catalysts of the type (N′N)Pd(CH₃)(Solv.)⁺ B(Ar_f)₄- (Ar_f = −3, 5-(CF₃)₂C₆H₃) have been prepared for living alternating copolymerizations of olefins with CO. This talk will focus on the mechanistic details of chain growth as elucidated by ¹H and ¹³C NMR spectroscopy, model studies of key migratory insertion steps and synthesis and properties of various copolymers and block copolymers based on styrenes, CH₂=CHC₆H₄X [X = p-C(CH₃)₃, p-OC(O)CH₃, p-OC(O)C-t-Bu), p-NHC(O)(C-t-Bu)]. Use of the catalysts based on the C₂ symmetric, homochiral ligand 2, 2'-bis[2-[4(S)-(Alkyl)-1, 3-oxazolinyl]]propane [Alkyl = CH₃, CH(CH₃)₂] produces a copolymer, 1, with a highly isotactic microstructure and high optical activity in contrast to achiral ligands such as 1,10-phenanthroline which produce copolymers with predominantly syndiotactic microstructure.     

Fluorophenylantimony carboxylates(II): synthetic and spectroscopic studies (UV, IR, H, F and C NMR) of pentafluorophenylantimony(V) di- and tetracarboxylates

Pentafluorophenylantimony(V) di- and tetracarboxylates of the molecular formula C₆F₅SbX₂L₂ (when X=L=OCOR (R=CH₃, CH₂Cl, CHCl₂, CCl₃, CF₃, CH₂OC₆H₃Cl₂-2,4, CH₂OC₆H₂Cl₃-2,4,5) and when X=Cl; L=OCOCH_3, OCOCHCl₂) have been synthesized by the metathetical reaction of pentafluorophenylantimony(V) tetrachloride and (dibromide)dichloride with corresponding sodium salt of carboxylic acids in appropriate molar ratio using 15-crown-5 as phase transfer catalyst. The van’t Hoff factor ‘i’ and molar conductance data of the compounds revealed them to be monomeric and non-conducting in nature. Elemental analysis, UV, IR and NMR (¹H, ¹⁹F and ¹³C) were used to characterize the derivatives. Compounds are tentatively assigned as a pentacoordinated square pyramidal structure in which carboxylate ligand behaving as a monodentate ligand.     

The dependence of 13C-1H coupling constants on CCC bond angles

The relationship between one-bond ¹³C-¹H coupling constants and internuclear CCC bond angles (_n) in hydrocarbons of the type R₂CH₂ is best approximated by a quadratic expression.     

13C-13C spin-spin coupling constants in the spectra of monosubstituted pyridines

The ¹³C- {¹H} NMR spectra of pyridine and a number of monosubstituted pyridines for compounds with the natural percentage of the ¹³C isotope were analyzed. The direct, geminal, and vicinal ¹³C-¹³C spin-spin coupling constants (SSCC) were determined. Linear relationships that link the ¹³C-¹³C SSCC in the spectra of monosubstituted pyridines and benzenes were obtained.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1383–1385, October, 1985.     

Synthesis and Characterization of Some Novel Dialkyldithiophosphate Derivatives of Macrocyclic Complexes of Pb(II) Having N2 S2 Potential Donors in 14- to 20-Membered Rings

Dialkyldithiophosphate derivatives of macrocyclic complexes of Pb(II), having N₂S₂ potential donors, of the general formula, [Pb(L)S₂P(OR)₂] (where L = macrocyclic ligands L¹, L², L³, L⁴ & L⁵ and R = CH₃-, C₃H₇ ⁿ- & C₃H₇ ⁱ-) have been Synthesized from the reactions of [Pb(L)X₂] (where X = Cl, NO₃, or CH₃COO) with sodium dialkyl dithiophosphates in 1:2 molar ratios in THF. Fifteen new derivatives have been synthesized by the combination of five macrocyclic complexes of 14–20 member rings with three different types of dialkyldithiophosphate. These compounds have been characterized by elemental analysis, molar conductance, molecular weight determination, IR, ¹H NMR, ¹³C, and ³¹P NMR. Molecular weight determinations of these complexes indicate their monomeric nature. An octahedral structure is proposed.     

Hyperfine Shifts of the 13C-NMR. in Protoporphyrin IX Iron (III) Dicyanide and Deuteroporphyrin IX Iron (III) Dicyanide

The ¹³C-NMR. in Zn(II) (Protoporphyrin IX), Fe(III) (Protoporphrin IX) (CN)₂, Zn(II) (Deuteroporphyrin IX dimethylester), and Fe(III) (Deuteroporphyrin IX) (CN)₂ have been identified, and the ¹³C hyperfine shifts in the iron complexes evaluated. In a partial analysis of these data the parameters Q^H, Q_CCH^H, and Q_C′CH^C, which characterize the isotropic coupling through hyperconjugation between the ¹H and ¹³C nuclei of the porphyrin side chains and the unpaired electron spin density on the aromatic ring carbon atoms, have been re-examined. This paper is part of an investigation of the electronic states in low spin ferric hemes and hemoproteins, and the relations between the electronic structures and the biological roles of these molecules.     

Properties and reactivity in groups of the periodic system: Ion-molecule reactions CH3X + CH3X+· (X = F through At)

The reactions indicated in the title have been studied in terms of direct processes and complex formation. Quantum-chemical methods have been applied to the passage of an acid (H⁺, CH, X⁺) from CH₃X^+· to CH₃X, and the abstraction of a radical (H^· CH, X^·) from CH₃X by CH₃X^+·. It has been shown that a complex represented by a dimer of a methyl-halide radical cation, (CH₃X), with a two-center three-electron bond X? X, has fairly high stability. These investigations were based on non-empirical quantum-chemical calculations, the results being systematically compared with experimental determinations. Some calculations included all electrons (X=F, Cl, Br), others were based on relativistic pseudopotentials (X=F through At). The two sets of calculations agree qualitatively with each other and with experimental observations.     

Syntheses,Structures and Spectroscopic Studies of Quadruply Bonded Complexes Containing Bridging Acetate and η3-etp Ligands (etp = Ph2PCH2CH2P(Ph)CH2CH2PPh2)

The quadruply bonded complexes containing bridging acetate and polydentate phosphine ligands of the type Mo₂(O₂CCR₃)X_J(η³-etp) (R = H, X = Br, 1; R = F, X = CI, 2; R = F, X = Br, 3; etp = Ph₂PCH₂CH₂P(Ph)CH₂CH₂PPh₂) were prepared by reactions of Mo₂(O₂CCR₃)X₂(PPh₃)₂ with etp in CH₂X₂. Their UV-vis and ³¹P{¹H}-NMR spectra have been recorded, and the structure of 1 has been determined by X-ray crystallography. Crystal data for 1·2CH₂Br₂: space group P2₁/c, a = 13.924(7) Å, b = 21.157(4) Å, c = 14.427(5) Å, β = 101.82(3)°, V = 4159(2) ų, Z = 4, with final residuals R = 0.0797 and Rw = 0.0793. The absorption wavelengths of the δ → δ* transitions and the chemical shifts and the coupling constants of the ³¹P{¹H}-NMR spectra of these complexes are dependent on the natures of the halogen atoms and the acetate ligands.     

Carbon-13 chemical shift assignment of some organophosphorus compounds: 1—Dialkyl and diaryl (alkylamido)phosphates with general formula Y2P(X)NHR

Carbon-13 chemical shifts and the POC, POCC, PNC and PNCC coupling constants of 18 compounds containing the amine moiety, and with the general formula Y₂P(X)NHR [Y=C₂H₅O, C₆H₅O, CH₂O, Y₂=1,2-dioxybenzene; X = O or S; R = H, CH₃, C₂H₅, PhCH₂CH₂, (CH₃)₂CH, C(CH₃)₃, C₆H₁₁, C₆H₅, C₆H₅NH] have been determined. The Y₂P(X) group shows a sterically induced effect on the amine moiety; the ¹³C chemical shift of the Y group is, however, almost unaffected on replacing P(O) by a P(S) group.     

Metal Complexes with a New Tetrapyridyl Pendant Armed Macrocyclic Ligand. X‐ray Crystal Structures of CuII and NiII Complexes

A new pendant‐armed macrocyclic ligand, L¹, bearing four pyridyl pendant groups has been synthesized by N‐alkylation of the tetraazamacrocyclic precursor L with 2‐picolyl chloride hydrochloride. Metal complexes of L¹ have been synthesized and characterized by microanalysis, MS‐FAB, conductivity measurements, IR, UV‐Vis, ¹H and ¹³C NMR spectroscopy and magnetic studies. Crystal structures of the ligand L¹ as well as of the complexes [Ni₂L¹](ClO₄)₄·5CH₃CN and [Cu₂L¹](ClO₄)₄·4.5CH₃CN have been determined by single crystal X‐ray crystallography. The X ray studies show the presence of two metal atoms within the macrocyclic ligand in both metal complexes showing five coordination arrangement for the metal ions.     

Theoretical study of aluminide clusters Al13X, Al13X−, and Al13X 2 − (X=H, Hal, OH, NH2, CH3, and C6H5)

The structural, electronic, energy, and vibrational characteristics of the Al₁₃X^? and Al₁₃X ₂ ^? clusters, with an aluminum-centered (Al_c) icosahedral cage Al₁₃ and with one or two outer-sphere ligands X=H, F, Cl, Br, OH, NH₂, CH₃, C₆H₅, have been calculated within the B3LYP approximation of the density functional theory using the 6-31G* and 6-311+G* basis sets. In all Al₁₃X^? radicals, the unpaired electron is localized at the cage atom Al* located opposite the Al-X bond. This Al* atom is the most favorable site for attaching the second X ligand of any nature (trans-addition rule). According to the previously suggested molecular model of the valence state of the [Al ₁₃ ^? ] “superatom,” the calculated energies D ₁(Al ₁₃ ^? -X) of addition of the first ligand to the Al ₁₃ ^? anion are about 1 eV lower than the corresponding energies of addition of the second ligand D ₂(XAl ₁₃ ^? -X). The structure of the Al₁₃ cage depends on the nature of the nature of the substituent X and can radically change in going from anions to their neutral congeners. In the lowest-lying Al₁₃X isomer with electronegative substituents X (Hal, OH, NH₂, CH₃, etc.), the aluminum cage has a marquee structure (1, symmetry C _s) with a hexagonal base and a pentagonal “roof.” For Al₁₃X analogues with electropositive ligands X (Al, Li, Na), a tridentate isomer (T, C _3v ) with the X substituent coordinated to a face of the Al₁₃ icosahedron is preferable. In the case of moderately electronegative X ligands (of the H type), the marquee (1) and icosahedral (T) isomers are close in energy. The stretching vibration frequencies of isomers 1 and T differ significantly in magnitude and intensity so that vibrational spectroscopy methods can be especially applicable to their experimental identification.     

Metathesis of silicon-containing olefins: IX. Synthesis of 1-(trimethylsilyl)-1-alkenes by olefin metathesis

1-(Trimethylsilyl)-1-alkenes of general formula CH₃(CH₂)_nCH?CHSi(CH₃)₃, where n = 3–15, have been prepared by a novel method, viz. by an effective cross-metathesis of vinyltrimethylsilane with 1-alkenes catalyzed by RuCl₂(PPh₃)₃. Excess of 1-alkene in the reaction mixture gave 1-(trimethylsilyl)-1-alkenes in good yields of up to 60% (in terms of vinylsilane). The products were identified by NMR spectroscopic (¹H, ¹³C NMR) and GC MS methods.     

A theoretical study of C4H5N isomers: Comparison of cyano and isocyano as substituents

Ab initio molecular orbital calculations using a 3-21G basis set have been used to optimize geometries for pyrrole, CH₃(X)CCH₂, CH₃(H)CCHX (both cis and trans), c-C₃H₅X, and CH₂CHCH₂X, where X is CN and NC. In all the alkenyl derivatives methyl groups are found to adopt the conformation in which the methyl hydrogen eclipses the double bond. 6-31G*∥3-21G level calculations show the alkenyl cyanides to be of similar energy to pyrrole, but the isocyanides are ～20 kcal mol^?1 higher in energy. For both substituents the cyclopropyl derivatives are higher in energy by ～10 kcal mol^?1. At the 6-31G* level ring strain is 27.7 kcal mol^?1 for the cyanide and 30.6 kcal mol^?1 for the isocyanide. Data on the relative energies of RCN and RNC are compared when R is (i) a saturated hydrocarbon, (ii) an unsaturated hydrocarbon, (iii) an α-carbenium ion, (iv) an allyl cation, and (v) an α-carbanion.