Synthesis of [B12H12]2- based extractants and their application for the treatment of nuclear wastes

Several closo-hydroborates bearing phosphite oxide, phosphine oxide or CMPO (carbamoylmethylphosphine oxide) groups, Cs[(Ph2P(O))(2)N(H)B12H11] (1), K[Ph2P(O)CH2C(O)N(H)(2)B12H11] (2), Na[Bz(2)N(H)B12H10OCH2CH2OCH2CH2P(O)(OBu)(2)] (5), Na[Bz(2)N(H)B12H10O(CH2)(4)N(R)C(O)CH2P(O)(Ph)(2)] (9, R=Pr-i; 10, R= Octyl), Na[Bz(2)N(H)B12H10OCH2CH2OCH2CH2N(Bu-i)C(O)CH2P(O)(Ph)(2)](-) (11) were synthesised employing novel neutral bipolar intermediates [Bz(2)N(H)B12H10O(CH2)(4)] (3) and [Bz(2)N(H)B12H10O(CH2CH2)(2)O] (4) as useful synthons. All new compounds were characterised by NMR spectroscopy and mass spectrometry techniques. Their abilities to extract selectively the radionuclides Am-241 and Eu-152 from nuclear waste solutions were investigated using a liquid-liquid extraction technique. Promising results were obtained with compound 10, which exhibits enhanced hydrophobicity and solubility in organic extraction solvent. (C) 2002 Elsevier Science B.V. All rights reserved.