Co-complexes of ortho-dilithiated thiophenol or 2-trimethylsilylthiophenol with lithiated TMEDA molecules: synthesis, crystal structures and theoretical studies (TMEDA = N,N,N',N'-tetramethylethylenediamine)

When an excess of nBuLi was used in the ortho-dilithiation of thiophenol or 2-trimethylsilylthiophenol in the presence of TMEDA (TMEDA = N,N,N',N'-tetramethylethylenediamine), deprotonation of TMEDA occurred and crystals of [Li3{(2-S-C6H4)(CH2MeNCH2CH2NMe2)(TMEDA)}]2 (1) or [Li4{(2-S-3-SiMe3-C6H3)(CH2MeNCH2CH2NMe2)2(TMEDA)}] (2) were obtained. Molecular orbital calculations on gas-phase 1 and 2 at the DFT B3LYP/6-31G(d) level reproduce the experimental structures fairly well. In spite of the short Li...Li distances, total electron density representations do not support the existence of Li...Li interactions.     

Synthesis and X-ray structure of ruthenium bis(acetylacetonate)(N,N,N',N'-tetramethylethylenediamine)

Although several ruthenium complexes of the type Ru(acac)(2)(L)(x), where x is 1 for a bidentate or 2 for a monodentate ligand, are known, the tmed complex is conspicuously absent. This article describes the synthesis of this complex from trans-RuCl(2)(tmed)(2), acetylacetone, and triethylamine in toluene. A new synthesis of trans-RuCl(2)(tmed)(2) is also described. Some physical properties and the X-ray crystal structure of Ru(acac)(2)(tmed) are provided.     

Kinetic study on the transfer mechanism of uranyl(VI) ions using N,N,N',N'-tetrabutyladipicamide from nitric acid media

By using stirred-cell method as experimental technique, the kinetictransfer mechanism of UO₂ ²⁺+ with N,N,N',N'-tetrabutyladipicamide(TBAA) from nitric acid solutions into toluene was studied. The differentconditions effecting the extraction rate constants (k'_f and k'_b ) were investigated, such as UO₂ ²⁺ concentration,HNO₃ concentration, TBAA concentration, temperature and agitationspeed. It was found that the extraction process was controlled by the diffusionof UO₂ (NO₃ )₂ . 2TBAA from the liquid-liquidsurface into the organic phase in the range of the experimental concentrationof HNO₃. The extraction rate was found to be of pseudo-first orderwith respect to the concentration of uranium(VI).     

Molecular structure and bonding properties of tris(N-methyl-formamide) formamide)(N,N, N', N'-tetramethylethylenediamine)-copper(II) perchlorate

Summary The x-ray crystal structure of tris(N-methylformamide) (N, N, N', N'-tetramethylethylenediamine)copper(II) perchlorate has been determined using three-dimensional x-ray diffraction data. The complex crystallizes in space group P2₁/c with Z=4. The cell dimensions are=8.255(3),b=17.951(6),c=16.541(4) Å, and =91.03(2)°. Least-squares refinement of the structure has yielded a final R value of 4.52% for 2108 independent reflect ions. The square pyramidal structure consists ofN, N, N', N'-tetramethylethylenediamine and twoN-methylformamide ligands forming a basal square plane with Cu–N bond lengths of 2.029(5) and 2.033(5) and Cu–O 1.981(4) and 1.985(4) Å, and a thirdN-methylformamide on the apex with a Cu–O distance of 2.181(4)Å. Each of the molecular plances of the three N-methylformamides lies nearly coplanar with thexy, yz andxz molecular coordination planes. The bonding properties of the title compound and its i.r. and uv-vis spectra are discussed with reference to the structure.     

N,N,N',N'-Tetrabutyladipicamide as a new extractant in toluene of nitric acid and uranium (VI)

N,N,N',N'-Tetrabutyladipicamide (TBAA) was used for the extraction of nitric acid and uranyl(II) ion from nitric acid media into toluene. The effects of nitric acid, uranyl(II) ion, and extractant concentration, temperature and back extraction on the distribution coefficient of uranyl(II) ion have been studied. The main adduct of TBAA and HNO₃ is TBAA·HNO₃ in 1.0 mol/l nitric acid solution. The 1:2:2 complex of uranyl(II) ion, nitrate ion and TBAA as extracted species is further confirmed by IR spectra of the extraction of uranyl(II) ion with TBAA. The values of the thermodynamic parameters have also been calculated.     

Synthesis and characterization of N,N,N',N'-tetrabutylsuccinamide as extractant for uranium(VI) and thorium(IV) ions from nitric acid solution

Synthesis and characterization of N,N,N',N'-tetrabutylsuccinamide (TBSA)was carried out and used for the extraction of U(VI) and Th(IV) from nitricacid solutions. Toluene was found to be the most suitable diluent for TBSAcompared with the other diluents tested. Extraction distribution ratios (D)of U(VI) and Th(IV) have been studied as a function of aqueous HNO 3 concentrations,NO₃ – ion concentration, TBSA concentration and temperature.The results obtained indicated that U(VI) and Th(IV) are mainly extractedas UO₂ (NO₃ ) ₂ . ₂TBSA and Th(NO₃ ) ₄ . TBSA, respectively, and the IR spectra of the extractedspecies have been investigated. The values of thermodynamic functions havebeen calculated. Back-extraction of U(VI) and Th(IV) from organic phases wasalso studied.     

An electron paramagnetic resonance study of Mn2(H2O)(OAc)4(tmeda)2 (tmeda = N,N,N',N'-tetramethylethylenediamine): a model for dinuclear manganese enzyme active sites

The complex Mn2(H2O)(OAc)4(tmeda)2 (tmeda = N,N,N',N'-tetramethylethylenediamine) is a model for the active site of hydrolase enzymes containing acetate-bridged dimanganese cores. The two high-spin Mn(II) ions are antiferromagnetically coupled, as determined by previous magnetic susceptibility studies (Yu, S.-B; Lippard, S. J.; Shweky, I; Bino, A. Inorg. Chem. 1992, 31, 3502-3504) to yield a spin "ladder" with total spin S = 0, 1, 2, ..., 5 in increasing energy. In this study, the complex was characterized by Q-band and X-band EPR spectroscopy in frozen solution. Analysis of the temperature dependence of these EPR spectra indicates that the primary spectral contribution is from the S = 2 manifold. The EPR spectra were simulated using a full spin Hamiltonian for this manifold of a coupled spin system, which provided the fit parameters J = -2.9 cm-1, g = 2.00, and D2 = -0.060 +/- 0.003 cm-1. An additional multiline EPR signal is observed which is proposed to arise from the total spin S = 5/2 ground state of a Mn(II) trimer of the type Mn3(OAc)6(tmeda)2.     

Radiolysis of cobalt(III)-1,2 bis(beta-aminoethoxy)ethane N,N,N',N' sodium sulfonate triacetic acid chelate

Chelation studies of cobalt(III) with 1,2 bis(beta-aminoethoxy)ethane N,N,N',N' sodium sulfonate triacetic acid (ASTA) were performed. The results showed the effectiveness of ASTA as a chelating agent by using: molar ratio, continuous variation and slope ratio methods. Stable complex 1∶1 was formed at pH from 6.0 to 10.5. Solutions of Co-ASTA chelate of different molar ratios at pH 6.5 and 8.0 were irradiated by different gamma-radiation doses. The results showed a linear decrease of absorbance with gamma-radiation dose which can be utilized as a dosimeter for low dose rate measurement in the range studied. A proposed radiolytic mechanism is discussed. The degradation of the ASTA ligand has been related to hydroxyl radical attack.     

Extraction of Dy(III) with N,N,N',N'-tetrabutylmalonamide

The extraction behavior of N,N,N',N'-tetrabutylmalonamide (TBMA) employing toluene as diluent toward Dy(III) has been investigated. The effect of the concentrations of nitric acid, lithium nitrate and extractant and also of the temperature on the distribution ratio has been studied. The stoichiometry found for the Dy(III) extracted species suggests a structure such as Dy(NO₃)₃ ^.3TBMA. An attempt has been made to establish the structure of the isolated extracted species recurring to the data of IR.     

Liquid chromatography of lanthanide chelates of 1-(p-nitrophenyl)ethylenediamine-N,N,N',N' -tetra-acetic acid

Preparation of the chelating agent, 1-(p-nitrophenyl)ethylenediamine-N,N,N',N'-tetra-acetic acid (p-nitrophenylEDTA), is described in detail. Separation of p-nitrophenylEDTA chelates of ytterbium(III), erbium(III), dysprosium(III) and europium(III) has been achieved by reversed-phase ion-pair liquid chromatography. With spectrophotometric detection at 254 nm, linear responses over about four orders of magnitude were achieved with detection limits (S/N = 2) of about 0.5 pmole.     

N,N,N',N'-四丁基丙二酰胺萃取铀(VI)的机理

研究了Ｎ,Ｎ,Ｎ’,Ｎ’－四丁基丙二酰胺（ＴＢＭＡ）以甲苯为稀释剂,从硝酸介质中萃取硝酸和铀（Ⅵ）的机理。在该萃取体系中,ＴＢＭＡ和 ＨＮＯ_３形成 ＴＢＭＡ· ＨＮＯ_３,和 Ｕ（Ⅵ）形成为 ＵＯ_２（ＮＯ_３）_２· ３ＴＮＭＡ。借助红外光谱分析,确定了在萃合物中ＮＯ_３~－不参与ＵＯ_２~（２＋）的直接配位,并对萃合物中配体的配位方式进行了讨论。     

Solution structures of lithium enolates, phenolates, carboxylates, and alkoxides in the presence of N,N,N',N'-tetramethylethylenediamine: a prevalence of cyclic dimers

The method of continuous variation was used to characterize lithium enolates, phenolates, carboxylates, and alkoxides solvated by N,N,N',N'-tetramethylethylenediamine (TMEDA). The method relies on characterizing an ensemble of homo- and heteroaggregates using (6)Li NMR spectroscopy. A combination of aggregate counts and symmetries, nearly statistical distributions, and quantitative parametric fits revealed that cyclic dimers are the dominant forms. Nonstatistical distributions favoring heteroaggregated dimers were observed when hindered enolates and carboxylates were mixed with unhindered enolates. Hindered (tertiary) alkoxides form higher aggregates (possibly hexamers), whereas hindered lithium phenolates appear to form TMEDA-solvated monomers.     

Synthesis and structural investigation of N,N',N' '-trialkylguanidinato-supported zirconium(IV) complexes

The addition of 2 equiv of N,N',N' '-triisopropylguanidine (guanH(2)) to Zr(CH(2)Ph)(4) produced the bis(guanidinato)bis(benzyl)zirconium complex [((i)PrNH)C(N(i)Pr)(2)](2)Zr(CH(2)Ph)(2) (1). The mono(guanidinato) complex [((i)PrN)(2)C(NH(i)Pr)]ZrCl(3) (2) was accessible by the reaction of 2 equiv of guanH(2) with ZrCl(4). Guanidinium hydrochloride, [C(NH(i)Pr)(3)]Cl, is a byproduct of this reaction. When crystallized from THF, complex 2 was isolated as the THF adduct [((i)PrNH)C(N(i)Pr)(2)]ZrCl(3)(THF) (2-THF). The mixed cyclopentadienyl guanidinato complex [eta(5)-1,3-(Me(3)Si)(2)C(5)H(3)][((i)PrNH)C(N(i)Pr)(2)]ZrCl(2) (3) was prepared by treatment of [1,3-(Me(3)Si)(2)C(5)H(3)]ZrCl(3) with the in situ generated lithium triisopropylguanidinate salt. The reaction of guanH(2) with [1,3-(Me(3)Si)(2)C(5)H(3)]ZrMe(3) affords the dimethyl derivative [eta(5)-1,3-(Me(3)Si)(2)C(5)H(3)][((i)PrNH)C(N(i)Pr)(2)]ZrMe(2) (4). Definitive evidence for the molecular structures of these products is provided through single-crystal X-ray characterization of 1, 2-THF, and 3, which are presented. The extent of pi delocalization within the guanidinato ligand is discussed in the context of the metrical parameters obtained from these structural studies.