12-coordinate complexes formed by the early lanthanide metals with 2,6-bis(-1,2,4-triazin-3-yl)-pyridine Carole Boucher a , Michael G.B. Drew a, * , Philip Giddings a , Laurence M. Harwood a , Michael J. Hudson a , Peter B. Iveson a , Charles Madic b a Department of Chemistry, University of Reading, Whiteknights, Reading, UK RG6 6AD b Commissariat a l’Energie Atomique, Direction du Cycle du Combustible, B.P. 17171, 30207 Bagnols-sur-C eze Cedex, France Received 2 May 2002; accepted 20 May 2002 Abstract The new extracting agent 2,6-bis(-1,2,4-triazin-3-yl)-pyridine (L 1 ) has been synthesised and has been shown to form unusual 12- coordinate complexes of stoichiometry [LnL 1 2 ðNO 3 Þ 3 ] with Nd and Pr which have been characterised by X-ray diffraction. Ó 2002 Elsevier Science B.V. All rights reserved. Keywords: Lanthanides; Actinides; Extraction; Nuclear reprocessing; 12-coordination One of the main problems associated with the pro- duction of nuclear energy is the safe long-term man- agement of radioactive waste. The main contributor to the long-term radiotoxicity of the waste is plutonium followed by the minor actinides. If the waste is to be stored without any reprocessing, a storage time of over 100,000 years is required for the level of radioactivity to fall to that of natural uranium. Reprocessing of both the plutonium and the minor actinides would reduce the required storage time to a few hundred years. The re- processing of plutonium using the PUREX process is currently undertaken in several countries such as the UK and France. Much current research is consequent- ally related to the reprocessing of the minor actinides [1]. It is envisaged that this reprocessing will include the partitioning of the minor actinides from the waste and their subsequent transmutation to shorter-lived isotopes [2]. Our studies have focussed on the partitioning of the most radiotoxic minor actinide, americium. The parti- tioning step is difficult because americium (III) has to be separated from the chemically similar lanthanide (III) ions which have high neutron-capture diameters. It has been shown, however, that polydentate nitrogen ligands can separate both Am(III) from the Ln(III). The most promising candidate ligands thus far of this type are the 2,6-bis-(5,6-dialkyl-1,2,4-triazin-3-yl)-pyridines (BTPs) (Fig. 1) which give Am/Ln separation factors of between 50 and 150 when used to extract from 1–2 M HNO 3 [3,4]. All the solvent extraction and complexation studies with the BTPs related to reprocessing have been carried out with substituted ligands L 2 with different alkyl groups in the 5 and 6 positions of the triazine rings [3–7]. The results presented here are the first obtained with the unsubstituted ligand 2, 6-bis-(1,2,4-triazin-3-yl)-pyridine (L 1 ). L 1 was synthesised using an adaptation of the lit- erature method (Fig. 2). The published synthesis of L 1 involves the conden- sation of monomeric glyoxal with 2,6-pyridine-dicarb- oxamide hydrazone [8]. This necessitates a preliminary step to obtain monomeric glyoxal by heating trimeric glyoxal [9]. We could only obtain very low yields of the monomeric glyoxal using this method and decided to investigate whether the stable, commercially available trimeric glyoxal could be used directly to synthesise L 1 . We found that L 1 could be synthesised in high yield by stirring the trimeric glyoxal with 2,6-pyridine-dicarbox- amide hydrazone in dry methanol at room temperature for 3 h under nitrogen, followed by refluxing overnight. The resulting yellow precipitate was filtered and further Inorganic Chemistry Communications 5 (2002) 596–599 www.elsevier.com/locate/inoche * Corresponding author. Tel.: +44-118-9318789; fax: +44-118- 9316331. E-mail address: m.g.b.drew@reading.ac.uk (M.G.B. Drew). 1387-7003/02/$ - see front matter Ó 2002 Elsevier Science B.V. All rights reserved. PII:S1387-7003(02)00489-6