Functionalized cobalt bis(dicarbollide) ions as selective extraction reagents for removal of M2+ and M3+ cations from nuclear waste, crystal and molecular structures of the [8,8′-μ-CIP(O)(O)2(1,2-C2B9H10)2-3,3′-Co]HN(C2H5)3 and [8,8′-μ-Et2NP(O)(O)2(1,2-C2B9H10)2-3,3′-Co](HN(CH3)3)

Abstract New reliable synthetic methods leading to derivatives of the closo -[(1,2-C 2 B 9 H 11 ) 2 -3,3′-Co] − ( 1 ) anion 1 with phosphorus containing substituents on the cage boron atoms have been successfully developed, starting from its 8-OH ( 2 ) and 8,8′-(OH) 2 ( 3 ) hydroxyderivatives. Reactions of 2 with either Cl 3 PO or PhCl 2 PO followed by hydrolysis gave 8-(HO) 2 POO ( 4 ) and [(8-PhPO(OH)O)-1,2-C 2 B 9 H 10 )(1,2-C 2 B 9 H 11 )-3,3′-Co] − ( 5 ) phosphorylated species, respectively. Analogous reactions of Cl 3 PO with 3 provided a chlorine bearing bridged product [8,8′-μ-ClP(O)(O) 2 (1,2-C 2 B 9 H 10 ) 2 -3,3′-Co] − ( 6 ) with surprisingly high hydrolytic stability. The anticipated anion [8,8′-μ-(HO)(O)-P(O) 2 (1,2-C 2 B 9 H 10 ) 2 -3,3′-Co] − ( 7 ) with phosphoric acid as the bridging substituent was obtained after alkaline hydrolysis of compound 6 . The related [8,8′-μ-Ph(O)P(O) 2 (1,2-C 2 B 9 H 10 ) 2 -3,3′-Co] − ( 8 ) derivative was prepared by similar reaction of 3 with PhCl 2 PO and subsequent hydrolysis. Further developments starting from versatile precursor 6 led to synthesis of a derivative containing an asymmetric bridging diethylphosporamide moiety [8,8′-μ-(Et 2 N)P(O)(O) 2 (1,2-C 2 B 9 H 10 ) 2 -3,3′-Co] − ( 9 ). A crystal of the compound 9 containing a pure enantiomer was selected, and its absolute configuration was determined by X-ray diffraction. Molecular structure of the compound 6 was also determined by X-ray diffraction analysis and the crystallographic results for both compounds are presented. Compounds 6 and 7 represent efficient Eu 3+ extractants, enabling metal extraction even from highly acidic solutions (up to 1 M HNO 3 ) to aromatic solvents. The novel compounds thus amalgamate in the single molecule good extraction properties of cobalta bis(dicarbollide) anion and the complexation ability of alkylphosphates.