Synthesis and spectral studies ofo-hydroxyacetophenone (N-benzoyl)glycyl hydrazone and some of its lanthanide(III) complexes

Summary o-Hydroxyacetophenone (N-benzoyl)glycyl hydrazone (o-HABzGH) has been characterized by i.r.,¹H n.m.r.,¹³C n.m.r. and mass spectral studies, and its complexes of the types [Ln(o-HABzGH)Cl₂(H₂O)₂]Cl and [Ln(o-HABzGH–2H)OH(H₂O)₃], where Ln=La, Pr, Nd, Sm and Eu, have been synthesized. The structures of the complexes have been studied by conductance, magnetic, electronic, i.r.,¹H n.m.r. and¹³C n.m.r. spectral techniques. The hypersensitive bands of the electronic spectra suggest coordination numbers six and seven around Nd^III in its adduct and neutral complexes respectively. I.r. and n.m.r. spectral data suggest a neutral bidentate behaviour for the ligand in the adducts and a dinegative tridentate nature in the neutral complexes.     

Pteridine studies: III—13C n.m.r. data of pteridine,some of its derivatives and their covalent σ-adducts with ammonia and water

¹³C n.m.r. spectral data of pteridine and nineteen of its derivatives (containing one or more chloro, methylthio, methyl, t-butyl or phenyl substituents) are reported. The ¹³C n.m.r. spectrum of the title compound has been assigned conclusively. ¹³C n.m.r. substituent effects are shown to be very useful in discerning between 6- and 7-substituted pteridines. Additionally, the ¹³C n.m.r. spectra of several covalent amination products, i.e. the 3,4-dihydro-4- amino- and the 5,6,7,8-tetrahydro-6,7-diaminopteridine derivatives, formed by dissolving the appropriate pteridine in liquid ammonia, have been recorded. The ¹³C n.m.r. spectra of the corresponding covalent hydrates are also reported.     

1H and 13C studies of alkenes,epoxides and cyclic thionocarbonates

¹H and ¹³C chemical shift data are presented and discussed for a number of di- and tri-alkyl substituted alkenes, epoxides and thionocarbonates. The completely stereospecific interconversion of these compounds, together with the n.m.r. data, allows a straightforward and quantitative stereochemical analysis. For ¹H n.m.r., the most useful intermediates proved to be the thionocarbonates. The differential shieldings between cis and trans isomers are tentatively explained in terms of the conformational change of the 5-membered thionocarbonate ring. In ¹³C n.m.r., either series can be useful to distinguish between stereoisomers. The conclusions stemming from the ¹³C n.m.r. results complement the ¹H n.m.r. studies.     

NMR-Untersuchungen an Dicyclopentadienderivaten. IV—1-Syn/anti-Epimere von endo-Dicyclopentadienderivaten

The syn/anti-arrangement of some substituents R in position 1 of endo-dicyclopentadiene derivatives is investigated by ¹H-and ¹³C n.m.r. spectroscopy. The HH-coupling constants of the epimeric alcohols 2 and 3 are determined by paramagnetic shift experiments [Eu(fod)₃] and the observed relative paramagnetic shifts ΔEu used for the determination of the configuration. The increasing steric compression in the syn-epimers is well reflected by the ¹H- and ¹³C n.m.r. chemical shifts.     

1H- und 13C-NMR-untersuchungen an dibromoxabicyclo[n.2.1]alkanen

The ¹H n.m.r. spectra of some dibromooxabicyclo[n.2.1]alkanes are discussed for the determination of the configuration and conformation. The ¹³C n.m.r. spectra confirm the observed stereochemistry. With increasing ring size the ¹³C n.m.r. chemical shifts of the hetero atom substituted C-atoms C-1 and C-2 move steadily to lower fields.     

Synthetic and physicochemical studies of divalent metal complexes with cyclic hydrazone and semicarbazone ligands

Summary The syntheses of 3,4,10,11-tetraphenyl-1,2,5,6,8,9,12,13-octaazacyclotetradeca-7, 14-dione-2,4,9,11-tetraene (dbdch) and 6-methoxy-1,6-diphenyl-4-oxo-3,4,5,6-tetrahydro-2,3,5-triazine (bsc) and their complexes with divalent metal ions (copper, nickel, cobalt, zinc, cadmium and mercury) are reported. All compounds were characterized by ¹H n.m.r., ¹³C n.m.r., i.r. and u.v.-vis. spectroscopy and by FAB mass spectrometry; possible structures are presented and discussed.Author to whom all correspondence should be directed.     

A 13C n.m.r. study of the charge-transfer complexes between o-chloranil and some aromatic electron donors

The ¹³C n.m.r. spectra of complexes between o-chloranil and aromatic electron donors were studied. Complexation leads to a general diamagnetic shift of the ¹³C n.m.r. signals for the acceptor (o-chloranil), but for signals from the ¹³C nuclei in the donors both diamagnetic and paramagnetic shifts are found. These phenomena are thought to be the result of competing anisotropy and charge-migration effects. Charge migration in o-chloranil complexes appears to be more important than in corresponding 1,3,5-trinitrobenzene complexes.     

13C n.m.r. spectra of some thiobenzamides. Correlation between 13C and 1H n.m.r. spectra and signal assignments of syn and anti CH2 groups

¹³C n.m.r. spectra of a series of N,N-disubstituted thioamides have been recorded and signal assignments were performed. Separate signals are observed for methylene groups fixed on the nitrogen atom. Since the carbon atom syn to the thiocarbonyl sulfur resonates at higher field than the anti carbon, the syn-anti assignment in ¹H n.m.r. is easily obtained by selective double irradiation. This method, which is rapid and reliable, affords a rather general solution to the interesting problem of resonance assignments in tertiary amides and thioamides (and in analogous molecules such as oximes and nitrosamines).     

Mixed ligand gold(I) complexes with phosphines and selenourea

A series of mixed ligand Au^I complexes with selenourea (Seu) and various phosphines, [R₃PAuSeu]Cl, have been prepared and characterized by elemental analysis, i.r. and n.m.r. methods. A decrease in the i.r. frequency of the C=Se mode of Seu upon complexation is indicative of Au^I binding via a selenone group. An upfield shift in the ¹³C-n.m.r. for the C=Se resonance of Seu, and downfield shifts in ³¹P-n.m.r., for the R₃P moiety are consistent with selenium coordination to Au^I.     

Complexation of palladium cyanide with imidazolidine-2-thione and its derivatives

Summary Pd(CN)₂ reacts with imidazolidine-2-thione (Imt), 1,3-diazinane-2-thione(Diaz), 1,3-diazipnane-2-thione (Diap) and their derivatives to yield complexes of stoichiometry [PdL₂(CN)₂] or [PdL(CN)₂] (L = Imt, Diaz or Diap and L = Imt having N-Me, Et or Pr substituents), which were characterized by elemental analysis, i.r., ¹H and ¹³C n.m.r. spectroscopy. Both mono- and bis ligand complexes are thought to be square planar with the monoligand binding to metal via sulphur (bridging) and the bis ligand via the monodentate thione group. The ¹³C enriched Pd(¹³CN)₂ complex was prepared and the ¹³C n.m.r. recorded. The C-2 resonance of ¹³C n.m.r. of Imt, Diaz or Diap complexes of the copper(I), silver(I), gold(I) and palladium(II) were compared.     

13C n.m.r. spectroscopy: Comparison of the spectra of some dimeric Catharanthus alkaloids and their derivatives

The ¹³C n.m.r. spectra of some dimeric Catharanthus alkaloids are reported and assigned. Methods devised to aid in the assignment of resonances in complex molecules are described. The ¹³C n.m.r. spectra of several derivatives of vinblastine are discussed.     

Deuterium isotope effects in solutions of 2,4-pentanedione

Proton and deuterium n.m.r. measurements in acetylacetone and 3,3-d₂-acetylacetone are reported. Deuterium-isotope effects on chemical shifts and keto–enol equilibria as a function of concentration in the two solvents triethylamine and pyrrole are determined. A strong solvent concentration dependence for d-isotope effects is observed in triethylamine; in pyrrole no dependence is obtained. The results are interpreted in terms of an equilibrium between the symmetrical (C_2v) and asymmetrical (C_s) enolic forms in acetylacetone. The usefulness of ²H n.m.r. for the study of exchange processes is demonstrated.     

Temperature effects on 13C n.m.r. chemical shifts of normal alkanes and some line r and branched 1-alkenes

¹³C n.m.r. chemical shifts of a number of 1,1-disubstituted ethylenes are presented. Moreover, effects of changing temperatures on the ¹³C n.m.r. chemical shifts of some of these compounds as well as of three normal alkanes are given. These variations in chemical shifts are attributed to varying amounts of sterically induced shifts in the different conformational equilibria. In addition to the well-known 1,4 interaction between two alkyl groups shielding effects on the carbon atoms of the connecting bonds are also proposed. No definite explanation of this effect is presented at this time. It is further shown that no simple correlations exist between ¹³C n.m.r. chemical shifts and calculated total charge densities at this level. Instead, the experimental results in 1-alkenes are rationalized by assuming a linear dependence of the ¹³C n.m.r. chemical shifts of C-1 and C-2 via rehybridizations on changes in bond angles for small skeletal deformations caused by steric interactions. These changes in geometries, as well as conformational energies in three 1-alkenes, were calculated by means of VFF calculations. Finally. upfield shifts for both C-2 and C-4 are proposed for those conformations of 1-alkenes in which the C-3? C-4 group interacts with the p_z-orbital of C-2.     

Complexation of (trimethylphosphine)gold(I) with Selenones

Mixed ligand complexes of gold(I) with various selenones and Me₃P, [Me₃PAuSe=C<]Cl, have been prepared and characterized by elemental analyses, i.r. and n.m.r. methods. A decrease in the i.r. frequency of the >C=Se mode of selenones upon complexation is indicative of selenone binding to gold(I) via a selenone group. An upfield shift in ¹³C-n.m.r. for the >C=Se resonance of selenones and downfield shifts in ³¹P-n.m.r. for Me₃P moiety are consistent with the selenium coordination to gold(I). The steric effect as well as the basicity of Me₃PAu⁺ plays a significant role in bonding with Se-containing ligands compared to the Et₃PAu⁺ and Ph₃PAu⁺ complexes.     

2,3-Di-tert-butyl-1-telluradiphosphiran und verwandte Phosphor—Tellur-Heterocyclen

2,3-Di-tert-butyl-1-telluradiphosphirane and related Phosphorus—Tellurium Heterocycles 2,3-Di-tert-butyl-1-telluradiphosphirane was isolated in pure state by trap to trap condensation after reaction of 1,2-Di-tert-butyl-1,2-dichlorodiphosphane with sodium telluride in pentane suspension. The telluradiphosphirane and other P? Te heterocycles (t-BuP)_nTe_m (n = 2, m = 1; n = 3, m = 1,2; n = 4, m = 1,2) are formed from 1,2-Di-tert-butyl-1,2-dichlorodiphosphane or tert-butyldichlorophosphane with bis(trimethylsilyl)telluride and from the reaction of tert-butylbis(trimethylsilyl)phosphane with elemental tellurium. The proposed structures of the P? Te heterocycles are based on ³¹P- and ¹²⁵Te-n.m.r. and MS data     

Platinum(II) complexes ofN-alkylphenothiazines

Summary The synthesis and physical properties of eight square-planar platinum(II) complexes, [PtLCl₂] (L =N-alkylphenothiazine) are reported. Analytical, conductometric, spectral (electronic, i.r. and¹H n.m.r.) and thermal data for the complexes are discussed.     

Gold(I) complexes with selenones and triphenylphosphine as ligands

A number of mixed ligand complexes of gold(I) with various selenones and Ph₃P, [Ph₃PAuSe=C<]Cl have been prepared and characterized by elemental analyses, i.r. and n.m.r. methods. A decrease in the i.r. frequency of the C=Se mode of selenones upon complexation is indicative of gold(I) binding viaa selenone group. An upfield shift in the ¹³ C-n.m.r. for the C=Se resonance of selenones and downfield shifts in ³¹P-n.m.r. for the Ph₃P moiety are consistent with the selenium coordination to gold(I). Available data in the literature suggest that P–Au–Se type complexes are usually linear.     

Silver(I) diethylphosphite — Bonding mode and phosphine co-ordination compounds — a31P NMR study

Summary Silver(I) complexes with the P/O ambidentate phosphito- and phosphinito-ligands are shown to adopt P-bonded structures in solution by means of³¹P n.m.r. spectroscopy.¹J(Ag, P) of AgP(O)(OEt)₂ represents the largest one bond silverphosphorus coupling constant reported so far. AgP(O)(OEt)₂ forms co-ordination complexes of the stoichiometry [Ag{P(O)(OEt)₂}(PBu ₃ ⁿ )_n], n=1, 2 or 3 which were characterized by³¹P n.m.r. spectroscopy.The nomenclature accords with that used in the review of Roundhillet al. ⁽¹⁾.     

Iterative least-squares analysis of dynamic n.m.r. spectra. Hindered rotation of the N-nitroso group in N-nitroso-N-cyanomethylmethylamine

Iterative analysis of dynamic n.m.r. (d.n.m.r.) spectra by the least-squares method was applied to the entire proton spectrum of N-nitroso-N-cyanomethylmethylamine and, separately, to the CH₃ and CH₂CN sub-spectra. Resulting differences in the estimated rates of rotation of the NO group are discussed in terms of systematic errors which may be involved in determining spin exchange rates by d.n.m.r. methods. The most probable explanation is that quadrupolar broadening and then unresolved ¹⁴N? ¹H spin–spin splitting may appear on increasing the temperature. Estimated entropies of activation indicate that the methyl sub-spectrum gives more reliable results.     

Spectral and biological studies of copper(II) complexes of 2-acetyl-pyridine thiosemicarbazones with bulky 4N-substituents

Summary Copper(II) complexes of a large number of 2-acetylpyridine ⁴N-alkyl thiosemicarbazones were prepared and characterized. I.r., electronic and e.s.r. spectra of the complexes, as well as ¹H and ¹³C n.m.r. spectra of the thiosemicarbazones, were obtained. Both the thiosemicarbazones and their complexes show either modest or no growth inhibitory activity against Aspergillus niger, but many have considerable activity against Paecilomyces variotii. There is a relationship between the antifungal activity and size of the ⁴N-substituent for both the thiosemicarbazones and their copper(II) complexes.