Reaktionen von Jod-tris-(trifluoracetat) mit aliphatischen Jodverbindungen

The present paper deals with the behaviour of various alkyliodides towards J(OCOCF₃)₃ bearing a suitable functional group which can serve as an internal nucleophile. All the products found1–8 can be explained without any doubt by a typical neighbouring group effect with the bis-trifluoroacetoxyiodine anion, J(OCOCF₃)₂ ^–, as an easily displaced leaving group.

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F. Cech undE. Zbiral, Tetrahedron31, 605 (1975).     

Structure elucidation and NMR assignments of an unusual aromatic monacolin analog from Monascus purpureus‐fermented rice

One unusual aromatic monacolin analog, aromonacolin A (1), was isolated from the ethanolic extract of Monascus purpureus‐fermented rice. Its structure was elucidated by extensive spectroscopic (HRESIMS, ¹H NMR, ¹³C NMR, HSQC, HMBC, and NOESY) and chemical methods. The absolute configuration of the C‐6 secondary alcohol was deduced via the circular dichroism data of the in situ formed [Rh₂(OCOCF₃)₄] complex.     

Spektroskopische Charakterisierung und Kristallstruktur von Trifluormethylchloriod(III)‐trifluoracetat (CF3I(Cl)OCOCF3)

Spectroscopic Characterization and Crystal Structure of Trifluoromethyl Iodine(III) Chloride Trifluororacetate (CF₃I(Cl)OCOCF₃) The ternary iodine(III) compound CF₃I(Cl)OCOCF₃ is obtained by reaction between CF₃I(Cl)F and (CH₃)₃SiOCOCF₃ at –50 °C. The molecule was characterized by vibrational spectra, NMR‐spectra, and a crystal structure analysis. CF₃I(Cl)OCOCF₃ crystallizes monoclinic in the space group P2₁/c with a = 1102.7(1) pm, b = 785.6(1) pm, c = 989.7(1) pm, and β = 101.34(1)°.     

1H and 13C nuclear magnetic resonance study of (D3)-trishomocuban-4-ol and (D3)-trishomocubanone

The complete assignments of the ¹H and ¹³C NMR spectra for (D₃)-trishomocuban-4-ol (3) and (D₃)-trishomocubanone (4) are reported. The difference between the ¹H and ¹³C chemical shifts of 3 and 4 and those of the hydrocarbon (D₃)-trishomocubane, and the substituent effect of the hydroxy group, can be adequately explained by the unique stereochemistry of these compounds.     

Formation of anionic palladium(0) complexes ligated by the trifluoroacetate ion and their reactivity in oxidative addition

As established previously for Pd(OAc)₂, Pd⁰ complexes are formed in situ from Pd(OCOCF₃)₂ and n equiv. triarylphosphines (4-Z-C₆H₄)₃P (Z = CF₃, F, Cl, H, CH₃; n ? 3). The phosphines are the intramolecular reducing agents and are oxidized to triarylphosphine oxides. The generated Pd⁰ complexes are anionic species ligated by the trifluoroacetate anion: Pd⁰(PAr₃)_n(OCOCF₃)⁻ (n = 2 or 3). Pd⁰(PAr₃)₂(OCOCF₃)⁻ is the reactive species involved in the oxidative addition to PhI. This leads to trans-PhPd(OCOCF₃)(PPh₃)₂, involved in equilibrium with the cationic complex trans-[PhPd(PPh₃)₂(DMF)]⁺, instead of the expected trans-PhPdI(PPh₃)₂ complex. The existence of anionic Pd⁰ complexes ligated by the acetate or trifluoroacetate ions delivered by the precursors Pd(OAc)₂ or Pd(OCOCF₃)₂, respectively, as well as their comparative reactivity in oxidative additions are consistent with theoretical DFT calculations.     

Syntheses and crystal structures of bis(4-dimethylaminopyridine) group 12 trifluoroacetates — M(OCOCF3)2·2DMAP (M=Zn, Cd, Hg)

Bis(4-dimethylaminopyridine) group 12 trifluoroacetates—M(OCOCF₃)₂·2DMAP (M=Zn, Cd, Hg) were prepared in quantitative yields from the anhydrous metal trifluoroacetates and DMAP. All compounds crystallize in the triclinic space group (no. 2) with two molecules per unit cell. While Zn(OCOCF₃)₂·2DMAP is built up by well-separated tetrahedral units exhibiting strongly covalent ZnO bonds to monodentate trifluoroactate groups, Cd(OCOCF₃)₂·2DMAP and Hg(OCOCF₃)₂·2DMAP form dimeric units. The metal centers are distorted octahedrally surrounded by two axial DMAP ligands, two ionic bridging and one chelating trifluoroacetate group.     

Perfluoralkyljod-verbindungen: das trifluormethyljod-bis-trifluoracetat CF3J(OCOCF3)2

CF₃I(OCOCF₃)₂ is formed from the reactions of CF₃IF₂ or CF₃IO with trifluoroacetic anhydride at low temperature. During the reaction of CF₃IF₂ with (CF₃CO)₂O CF₃IF(OCOCF₃) is formed as an intermediate product. The preparation, the ¹⁹F-nmr spectra and the thermal decomposition are described.     

A13C nuclear magnetic resonance study of some linear alkynyl gold(I) and silver(I) complexes

Summary Phenylacetylide gold(I) and silver(I) compounds of the type [n-Bu₄N][M(C=CPh)₂], (1) and [n-Bu₄N][XMC=CPh], (2) have been studied by¹³C n.m.r. spectroscopy and their chemical shifts are reported for the first time. The shielding of the alkynyl carbon linked directly to the metal in (2) isca. 10–15 ppm less than the analogous carbon in (1) (M=Au), andca. 6–11 ppm less in the silver complexes (M=Ag). The variation in chemical shift depends on the nature of X(X=Cl, Br, I, C₂Ph and Ph₃P) and indicates greatly different degrees of polarization of the Au-C= (or Ag-C=) bonds in (1) and (2). I.r. spectra of the title compounds are reported and confirm the weakness of ML back-bonding. Comparison is also made with¹³C and i.r. data for platinum, and mercury complexes.     

Derivatives of cis-NPCl2(NSOCl)2 and (NPCl2)2NSOCl. Part XIV—synthesis and nuclear magnetic resonance study of dimethylamino derivatives of NPCl2(NSOPh)2 and (NPCl2)2NSOPh

The compounds trans-NPCl_2?n(NMe₂)_n(NSOPh)₂(n=0-2iNPCl_2?n NMe₂)_n (NSOPh)₂ (n=0-2) and N₂P₂Cl_4?nl_4?n(NMe₂)_nNSOP₂P₂Cl_4?n(NMe₂)_nNSOPh(n=0-4), were prepared from their chloro-precursors. The substitution follows a completely non-geminal pathway, and all possible isomers are formed. The observed relative abundance of these isomers shows that the phenyl group exhibits a strong directing effect on the incoming amine. The ¹H, ³¹P and ¹³C NMR spectra of the most abundant isomers are reported. ²J(CP) couplings within the PNMe₂ grouping are affected by the number of substituents at the phosphorus atom. Almost linear relationships exist between the degree of substitution and the chemical shift of C-1 and C-4 of the phenyl groups. The effect of substitution on the ¹³C chemical shifts of these groups is ascribed to inductive effects.     

The effect of the solvent upon the rates and machanisms of organometallic reactions: VII. A 19F NMR study of complexation of CF3 HgX (X = Cl,I, OCOCF3)

The concentration and temperature dependence of J(¹⁹⁹HgC¹⁹F) for solutions of CF₃HgX (X = Cl, I, OCOCF₃) in various solvents shows that in inert solvents these molecules exist mainly as non-solvent dimers (X = I or OCOCF₃) or as monomers (X = Cl). In strongly coordinated solvents $\text{1}\text{2}$ complexes are largely formed from CF₃HgX and the electron-donating solvent molecules. In pyridine solution an equilibrium exists between the $\text{1}\text{1}$ and $\text{1}\text{2}$ complexes. Complexes of the type CF₃HgX·D are T-shaped and have a higher relative content of s-electrons in the HgCF group compared with tetrahedral CF₃HgX·2D complexes.     

Déplacements Chimiques du Carbone 13, Constantes de Couplage 1J(CH) et 3J(CH) dans une série de dérivés trisubstitués du benzène

¹³C chemical shifts, 1-bond and 3-bond (meta) ¹³C? H coupling constants have been determined in a series of trisubstituted benzene; the substituents are Cl, NH₂, N(C₂H₅)₂, N(iC₃H₇)₂, N(C₂H₄)₂O. Chemical shifts are only in moderate agreement with the usual additivity rules. Additivity rules relative to the above mentioned coupling constants are proposed. With few exceptions, the difference between predicted and observed values is less than 10%.     

Green and efficient synthesis of 1H-indazolo[1,2-b] phthalazine-1,6,11(13H)-triones using ZrO(NO3)2.2H2O as a novel catalyst and theoretical study of synthesized compounds

The one-pot three-component synthesis for the preparation of 1H-indazolo[1,2-b] phthalazine-1,6,11(13H)-triones through condensation of phthalimide, hydrazine monohydrate, dimedone, and aromatic aldehydes in the presence of a novel catalytic amount of ZrO(NO₃)₂.2H₂O at reflux conditions in water has been reported. Quantum theoretical calculations for the three structures of compounds ( 5a , 5b , and 5c ) were performed using the G3MP2, LC-ωPBE, MP2, and B3LYP methods with the 6-311 + G** basis set. After optimizing the structures, geometric parameters were obtained and experimental measurements were compared with the calculated data. The structures of the products were confirmed by IR, ¹H NMR, ¹³C NMR, and elemental analysis. IR spectra data and ¹H NMR and ¹³C NMR chemical shifts computations of the 1H-indazolo[1,2-b]phthalazine-1,6,11(13H)-trione derivatives in the ground state were calculated. Frontier molecular orbitals, total density of states, thermodynamic parameters, and molecular electrostatic potentials of the title compounds were investigated by theoretical calculations. Molecular properties such as the ionization potential (I), electron affinity (A), chemical hardness (η), electronic chemical potential (μ), and electrophilicity (ω) were investigated for the structures. Consequently, there was an excellent agreement between experimental and theoretical results.     

Interaction of bis(trimethylsilyl)acetylene complex of titanocene with mercury trifluoroacetate

The reaction of the bis(trimethylsilyl)acetylene complex of titanocene Cp₂Ti(Me₃SiC₂SiMe₃) with mercury trifluoroacetate (NF₃COO)₂Hg at 20 °C in a THF medium affords titanocene bis(trifluoroacetate) Cp₂Ti(OCOCF₃)₂ and metallic mercury. The structure of Cp₂Ti(OCOCF₃)₂ was established by the analytical and spectroscopic methods and X-ray diffraction analysis.     

Carbon-13 isotope effect on proton decoupled 13C and 31P n.m.r. spectra of bis(diphenylphosphino)acetylene

High resolution proton decoupled ¹³C and ³¹P n.m.r. spectra of bis(diphenylphosphino)acetylene in (CD₃)₂SO and CDCl₃ are analysed as ABX spectra to give the relative chemical shifts of the ¹³C and ³¹P nuclei as well as the spin–spin coupling constants ³J(PP) and ⁿJ(PC). The differences in ³¹P shieldings are due to secondary ¹³C isotope effects which have been observed to be negligible over more than two bonds.     

Stereospecificity of 1H, 13C and 15N shielding constants in the isomers of methylglyoxal bisdimethylhydrazone: problem with configurational assignment based on 1H chemical shifts

In the ¹³C NMR spectra of methylglyoxal bisdimethylhydrazone, the ¹³C‐5 signal is shifted to higher frequencies, while the ¹³C‐6 signal is shifted to lower frequencies on going from the EE to ZE isomer following the trend found previously. Surprisingly, the ¹H‐6 chemical shift and ¹J(C‐6,H‐6) coupling constant are noticeably larger in the ZE isomer than in the EE isomer, although the configuration around the –CH═N– bond does not change. This paradox can be rationalized by the C–H?N intramolecular hydrogen bond in the ZE isomer, which is found from the quantum‐chemical calculations including Bader's quantum theory of atoms in molecules analysis. This hydrogen bond results in the increase of δ(¹H‐6) and ¹J(C‐6,H‐6) parameters. The effect of the C–H?N hydrogen bond on the ¹H shielding and one‐bond ¹³C–¹H coupling complicates the configurational assignment of the considered compound because of these spectral parameters. The ¹H, ¹³C and ¹⁵N chemical shifts of the 2‐ and 8‐(CH₃)₂N groups attached to the –C(CH₃)═N– and –CH═N– moieties, respectively, reveal pronounced difference. The ab initio calculations show that the 8‐(CH₃)₂N group conjugate effectively with the π‐framework, and the 2‐(CH₃)₂N group twisted out from the plane of the backbone and loses conjugation. As a result, the degree of charge transfer from the N‐2– and N‐8– nitrogen lone pairs to the π‐framework varies, which affects the ¹H, ¹³C and ¹⁵N shieldings. Copyright © 2012 John Wiley & Sons, Ltd.     

Geometric Isomers of Cobalt(II) and Cobalt(III) Picolinates in Solution

Cobalt complexes with picolinic acid (HPic), namely, [Co^II(Pic)₂(H₂O)₂] · 2H₂O (I) and [Co^III(Pic)₃] · H₂O (II) are studied using ¹H and ¹³C NMR spectroscopy. Compound Iexists in solution as three geometric isomers, namely, trans-trans-trans, cis-trans-cis, and trans-cis-cis(molar ratio 4 : 2 : 1, respectively). According to ¹³C NMR data, compound IIexists in solution as a mer-isomer. The relative energy stability of the isomers was estimated using the molecular mechanics method.     

Structural Organization of Symmetrical Dialkylthiuram Disulfides and Their Cyclic Analogs: X-Ray Diffraction and CP/MAS (13C, 15N) NMR Studies

High-resolution ¹³C and ¹⁵N solid-state NMR spectra were recorded for seven crystalline tetraalkyl-thiuram disulfides and their cyclic analogs of the general formula [R₂NC(S)S]₂ (where R = CH₃, C₂H₅, C₃H₇, and i-C₃H₇ or R₂ = (CH₂)₅, (CH₂)₆, and (CH₂)₄O). The ¹⁵N and ¹³C NMR resonances were assigned to the particular atoms in the compounds studied. Different isotropic ¹⁵N chemical shifts for both dialkyldithiocarbamato groups were interpreted while considering the inductive effects of the alkyl substituents combined with the mesomeric effect of the dithiocarbamato group. X-ray diffraction data were used to refine the molecular structure of bis(cyclohexamethylene)thiuram disulfide and to quantitatively characterize the conformations of the seven-membered N(CH₂)₆ heterocycles.     

Electronic effects in octahedral π-allyliron complexes: 13C NMR spectra

¹³C NMR spectra have been studied for the three series of allyliron derivatives: (i) C₃HP₅Fe(CO)₃X (X = I, Br, Cl, ONO₂, OCOCH₃, OCOCF₃); (ii) 2-RC₃H₄Fe(CO)₃X (R = CH₃, Br; X = I, Br, Cl, ONO₂, OCOCF₃), and (iii) 1-RC₃H₄Fe(CO)₃X (R = CH₃, C₆H₅; X = Br, Cl, OCOCF₃). The spectra reveal the effect of the nature of the ligand X and substituent R on the chemical shifts of the allyl and carbonyl carbon atoms.     

Structure, 31P and 13C chemical shift anisotrophy of (CH3)3P, (CH3)3PO, (CH3)3PS and (CH3)3PSe as determined by liquid crystal NMR spectroscopy

The ¹³P and ¹³C spectra of the triply ¹³C labelled molecules (CH₃)₃P, (CH₃)₃PO, (CH₃)₃PS and (CH₃)₃PSe oriented in a nematic phase are reported. The CPC bond angles have been measured. The ¹³P chemical shift tensor shows a large anisotropy except in the case of (CH₃)₃P. The abnormal large value observed for the PSe bond length suggests a large anisotropy of the ¹J(PSe) spin coupling.     

Zur Interpretation 29Si-NMR-chemischer Verschiebungen

The ²⁹Si-NMR chemical shifts δ(²⁹Si) of (CH₃)_4?nSiX_n compounds and some ¹³C-NMR chemical shifts δ(¹³C) of analogous carbon compounds are discussed by means of relative paramagnetic screening constants σ*, calculated by a simplified model. In this model only the Si(3P)- and C(2P)-orbitals are considered; for the calculations, the electronegativities of Si, C and the X-substituents and a single empirical parameter are necessary. The calculated values of σ* are in good agreement with the change of the chemical shifts which are observed for the (CH₃)_4?nMX_n compounds with different X and n. These results clearly show that δ(²⁹Si) and δ(¹³C) depend primarily on the σ-charge of the Si- and C-atom, and that (P? d)π-interactions on the Si-atom are of minor importance.