Phosphonates as alternative to tributyl phosphate for the separation of actinides from fission products

The present work investigates the role of increase in the basicity of organophosphorus extractant (dialkylalkyl phosphonates) on the uptake of actinides and fission products vis-à-vis tributyl phosphate (TBP), currently employed as a universal extractant. Two dialkylalkyl phosphonates viz. dibutylpropyl phosphonate (DBPrP) and dibutylpentyl phosphonate (DBPeP) were synthesized, characterized and evaluated for their solvent extraction behavior towards U(VI), Th(IV), Eu(III) and Tc(VII) in nitric acid medium ranging from 0.01–6 M. It was observed that increasing the basicity of the phosphoryl oxygen enhanced the uptake of the actinides and the distribution coefficient values were significantly larger as compared to TBP. The limiting organic concentration (LOC) value was estimated for Th(IV) for these extractants and compared with the TBP system. The separation factors of actinides with phosphonates over Tc(VII) are distinctly better than that with TBP.

Spectroscopic and magnetic evidence of coordination properties of bioactive diethyl (pyridin-4-ylmethyl)phosphate ligand with chloride transition-metal ions

A series of five chloride coordination compounds of diethyl (pyridin-4-ylmethyl)phosphate (4-pmOpe) ligand, i.e. [CuCl2(4-pmOpe)2], [NiCl2(4-pmOpe)4], [CoCl2(4-pmOpe)], [ZnCl2(4-pmOpe)2], and [CdCl2(4-pmOpe)2], was prepared and studied. Stoichiometry and stereochemistry of the compounds was confirmed by spectroscopic and magnetic studies as well as by elemental analyses. The 4-pmOpe ligand has a capacity to coordinate to metal ions by means of phosphoryl oxygen and/or nitrogen of pyridine atoms. In Cu(II), Ni(II), and Zn(II) compounds, 4-pmOpe adopts the monodentate coordination mode, bonding metal centers through the pyridine nitrogen atom only. On the contrary, in Co(II) and Cd(II) compounds, 4-pmOpe acts as N,O-bridging ligand forming polynuclear structures. Magnetic studies (1.8–300 K) indicate mononuclear structure of the Co(II) and Ni(II) compounds and suggest existence of a very weak exchange coupling between metal centers in crystal lattice.

Unusual cis/trans Isomerism in Octahedral Nickel(II) Complexes with 1,4,8,11-Tetraazacyclotetradecane-1,8-bis(methylphosphonic Acid) as a Ligand

Nickel(II) ion reacts with 1,4,8,11-tetraazacyclotetradecane-1,8-bis(methylphosphonic acid) (H4L1) at room temperature with formation of cis-[Ni(L1)]2- complex. The complex was crystallised in several forms in dependence on conditions of isolation (temperature, pH, solvent mixture). Crystal structures of cis-O,O-[Ni(H2L1)] (1), cis-O,O-[Ni(H2L1)]·2H2O (2), cis-O,O-[Ni(H3L1)]Cl·H2O (3) and cis-O,O-[Ni(H4L1)]Cl2·2H2O (4) were determined by X-ray diffraction. In all the compounds, Ni2+ is in octahedral cis-O1,O2-trans-N1,N8-cis-O1,N4-[Ni(L1)]2- (hereafter abbreviated as cis-O,O-[Ni(L1)]2-) arrangement with V conformation of the cyclam ring. Complexes 3 and 4 exhibit very unusual coordination through the phosphoryl group of double-protonated phosphonate moiety. Tetraethylester of H4L1 having only poorly coordinating phosphoryl oxygen atoms also forms nickel(II) complex 5 with cis arrangement. Corresponding trans-O,O-[Ni(L1)]2- complex is formed only in strongly acidic medium through conversion of the cis complex; it was characterised by X-ray diffraction as dihydrochloride dihydrate, trans-O,O-[Ni(H4L1)]Cl2·2H2O (6). The analogous compound (NH4)2(trans-O,O-[Ni(L2)])·H2O (7) is obtained quantitatively by reaction of Ni2+ with 4,11-dibenzyl-1,4,8,11-tetraazacyclotetradecane-1,8-bis(methylphosphonic acid) (H4L2). Formation of this complex 7 in the III cyclam ring conformation is preferred to the cis complex due to steric hindrance of bulky benzyl groups in cis-[Ni(L2)]2- complex with the V cyclam ring conformation.

Coordination Compounds of Lanthanide Nitrates with Dimorpholido-N-trichloroacetylphosphorylamide. The Structure of Di(dimorpholido-N-trichloroacetylphosphorylamide)- diaqua Neodymium(III)trinitrate

Lanthanide, Carbacylamidophosphate The coordination compounds of the general formula Ln(NO3)3(HL)2(H2O)2 H2O , where Ln = La, Ce -Nd, Sm -Dy, HL = CCl3C(O)NHP(O)[N(CH2CH2)2O]2, dimorpholido-N-tri-chloroacetylphosphorylamide, have been synthesized. The complexes were studied by IR, 1H and 31P NMR and UV-VIS absorption spectroscopies. X-ray diffraction analyses indicate that all synthesized compounds are isostructural. The crystal structure of Nd(NO3)3(HL)2(H2O)2 H2O was solved (monoclinic, a = 11.0467(3), b = 15.9080(5), c = 24.1921(7) Å, β = 96.4080(10)°, space group P21/n, V = 4224.7(2) Å3, Z = 4, R = 0.049, wR = 0.0915). The complex has a molecular structure. The monodentate neutral phosphorictriamide ligands are coordinated to the metal atom via the phosphoryl oxygen atom. The coordination polyhedron of Nd is a sphenocorona; C.N. = 10(60[NO3-], 20[HL], 20[H2O]). It was shown that these compounds in methanol solution are 1:1 electrolytes, and in acetone solution weak electrolytes. According to NMR data in acetone solution the complexes of the lanthanides with the ligand {HL} have axial symmetry.