Intramolecular Interaction in Heterocyclic Phosphines

Some specific features of space structure, reactivity, complex formation and unusual physical properties of organic and organophosphorus compounds are due to univalent intramolecular interactions. Several intramolecular interactions observed in heterocyclic phosphines will be discussed in this current paper.     

Dimephosphone analogs: I. Synthesis and structure of some dimephosphone aryl- and acylhydrazones

Dimephosphone (2-dimethoxyphosphoryl-2-methylpentan-4-one) phenyl-, nitrophenyl-, benzoyl-, and 4-nitrobenzoylhydrazones were synthesized. The compounds in crystals were shown to have a steric form exclusively of the E-isomer. The structure of hydrazones in solution is defined by the nature of the substituents and the solvent and the time of storage of the solution. The dimephosphone aroylhydrazones in acid solutions exist in several possible forms: the isomers at the imine bond, the conformers at the amide bond, and a cyclic tautomer (1,3,4-oxadiazoline).     

A Double Addition of LnH to a Carbon-Carbon Triple Bond and Competitive Oxidation of Ytterbium(II) and Hydrido Centers

Addition of two Ln?H bonds of an Yb(II) hydrido complex supported by bulky amidinate ligand to a C?C bond lead to the formation of 1,2-dianionic bibenzyl fragment. Both Yb(II) and hydrido centers are oxidized under the reaction conditions. The resulting Yb(II) -η(6) -arene interaction is surprisingly robust: the arene cannot be replaced from the metal coordination sphere when treated with Lewis bases.     

Complexation and extraction of non-ferrous metals by calix[n]arene phosphine oxides

The extraction of non-ferrous metal (M²⁺) nitrates by the calix[4,6]arenes (L), bearing four or six phosphine oxide donor groups at the upper or at the lower rim, was quantitatively described in the form of [M_n(NO₃)_2nL] (n = 1, 2) complexes. The extraction constants (Zn²⁺ > Cu²⁺ > Co²⁺ > Ni²⁺) for the both types of L coincide with Irving-Williams sequence. Calix[4]arenes, phosphorylated at the lower (narrow) rim, provide better stability of ML complexes because of the best spatial fitting of M²⁺ by the donor groups. For the upper (wide) rim phosphorylated calix[4]arenes M₂L and ML₂ complexes are more stable. Unusual zwitterionic [Co₂(NO₃)₄L] complex of the lower rim tetraphosphorylated calix[4]arene 1 was determined by X-ray structural analysis.     

Extraction of gold(III) by sulfur-containing calix[4,6]arenes from hydrochloric acid solutions

Thiacalixarenes 1 and 2, thiacalixarene thioether 5, and calixarene thioethers 3a–3c, 4a, and 4b are compared with respect to gold(III) extraction from hydrochloric acid solutions. The gold extractability increases in the following order: 1,2 5 3a–3c, 4a, 4b. The effect of the substituents at the sulfur atom in R₂S and in 3a–3c, 4a, and 4b is identical when cooperative effects (CE) appear for calixarene thioethers. On the basis of the extraction stoichiometry and the activities of the components of the aqueous phase, the gold distribution in the form of (AuCl₃)_nL (n = 1?4) species is quantified for c_HCl from 0.5 to 6 mol/L. A correlation is found between the gold distribution constants into various diluents and the Kamlet-Taft parameter π*.     

Extraction of palladium with thiacalix[4]arenes from nitric acid nitrate-nitrite solutions

Calix[4]arene 1, thiacalix[4]arenes 2(LH₄), and calix[4]arenethioether 3 were compared in palladium extraction from nitric acid solutions; D _Pd for 2 was shown to be 2?C3 orders of magnitude larger than for 1 at pH > 3 (comparable with 3) because of cation-exchange and coordination extraction of palladium. It was shown by extraction methods and IR spectroscopy that thiacalixarenes 2 extract complex species [Pd _n L _m H_{4 ? 2n} ] (m = 1, n = 1 and 2) and [(PdA₂) _n L _m H₄] (A = m = 1, n = 1?C4) from nitric acid solutions at pH 3. Extraction constants for these palladium species that satisfactorily describe experimental data were calculated. As distinct from 3, thiacalixarenes 2 are promising for the combined extraction of palladium and silver from alkaline solutions and the selective extraction of fission palladium from nitric acid solutions. Phosphorylated at the upper rim thiacalixarenes 2 can be considered as bifunctional extractants for the separation of fission radionuclides.